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Catálisis para el Medioambiente y la Energía

Broad objectives:
Synthesis procedures of supported and structured catalysts for pollution control and hydrogen production, Application of microchannel reactor technology for pollution abatement and hydrogen production
Specific objectives:
Development of new synthesis procedures, e.g. SIL (Supported Ionic Liquids) catalysts
Specific advantages
The line is able of addressing answers to the catalytic problems from the very basic aspects (ab initio calculations; study of model catalysts) to the manufacturing of state-of-the-art devices (microreactors) due to the acquired knowledge in other fields

Catedráticos
Nombre Teléfono email web
Caballero Martínez, Alfonso 954 48 95 38 caballero@us.es matproner
Navío Santos, José Antonio 954 48 95 50 navio@us.es sisius
Odriozola Gordón, José Antonio 954 48 95 44 odrio@us.es sisius
Investigadores Científicos
Nombre Teléfono email web
Centeno Gallego, Miguel Angel 954 48 95 43 centeno@icmse.csic.es
Colón Ibáñez, Gerardo 954 48 96 26 gcolon@icmse.csic.es matproner
Científicos Titulares
Nombre Teléfono email web
Hidalgo López, María del Carmen 954 48 95 50 mchidalgo@icmse.csic.es mchidalgo
Holgado Vázquez, Juan Pedro 954 48 95 36 holgado@icmse.csic.es matproner
Profesores Titulares
Nombre Teléfono email web
Domínguez Leal, María Isabel 954 48 96 64 mleal@icmse.csic.es sisius
Macías Azaña, Manuel 954 48 95 41 mmacias@icmse.csic.es sisius
Romero Sarria, Francisca 954 48 96 64 francisca@icmse.csic.es sisius
Investigadores/Doctores Contratados
Nombre Teléfono email web
Bobadilla Baladrón, Luis Francisco 954 48 95 00 + ext. 90 92 18 bobadilla@icmse.csic.es
Ivanova Lyuvimirova, Svetlana 954 48 95 00 + ext. 90 92 18 svetlana@icmse.csic.es
Laguna Espitia, Oscar 954 48 95 43 oscarh@icmse.csic.es
Martínez Tejada, Leidy Marcela 954 48 95 76 leidy@icmse.csic.es
Penkova, Anna Dimitrova 954 48 95 00 + ext. 90 92 18 anna@icmse.csic.es
Pereñiguez Rodríguez, Rosa 954 48 95 76 rosa@icmse.csic.es matproner
Becarios Predoctorales
Nombre Teléfono email web
Azancot Luque, Lola 954 48 95 00 + ext. 90 92 31 lola.azancot@icmse.csic.es
Castillo Barrero, Rafael 954 48 95 00 + ext. 90 92 22
García Moncada, Nuria 954 48 95 00 + ext. 90 92 22 nuria.garcia@icmse.csic.es
Garcilaso de la Vega González, Victoria 954 48 95 00 + ext. 90 92 30 victoriagarcilaso@icmse.csic.es
Jiménez Barrera, Elena 954 48 95 00 + ext. 90 92 22
Santos Muñoz, José Luis 954 48 95 00 + ext. 90 92 30 josel.santos@icmse.csic.es
Personal Contratado
Nombre Teléfono email web
López Martín, Ángeles María 954 48 95 00 + ext. 90 92 25 angeles.lopez@icmse.csic.es matproner
Navarro De Miguel, Juan Carlos jnavarro12@us.es

Desarrollo de Materiales Foto-Funcionales para Aplicaciones Medioambientales



Investigador Principal: José Antonio Navío Santos
Periodo: 01-01-2016 / 31-12-2018
Organismo Financiador: Ministerio de Economía y Competitividad
Código: CTQ2015-64664-C2-2-P
Componentes: María del Carmen Hidalgo López, Manuel Macías Azaña

Resumen [+]

La fotocatálisis heterogénea es un proceso avanzado de oxidación que ha sido objeto de una enorme cantidad de estudios relacionados con la purificación de gases y del agua. La mayoría de estos estudios se han realizado para el tratamiento de aguas y utilizando el TiO2 o materiales basados en este óxido y más recientemente, aunque en una clara minoría, se han estudiado otros óxidos inorgánicos binarios, ternarios y cuaternarios, predominando en todo caso los estudios de estos últimos materiales para el tratamiento de aguas. En cuanto al catalizador (base del proceso fotocatalítico) que es el responsable de la eficacia o fracaso del proceso, en la última década se han desarrollado numerosos y variados métodos de síntesis que han sido principalmente probados en procesos de degradación fotocatalítica en fase acuosa. Sin embargo, pocos estudios se han realizado con óxidos mixtos ( binarios, binarios-acoplados, ternarios y cuaternarios) y menos en fase gasesosa.

En base a estas consideraciones y a la dilatada y reconocida experiencia que el grupo de este Subproyecto#2 tiene el campo de la síntesis y caracterización de materiales foto-funcionales (en el UV y UV/Vis), y debido al reducido número de estudios fotocatalíticos en fase gas, en su mayoría estudiando un sólo componente, se plantea en este Subproyecto#2, el desarrollo de materiales foto-funcionales que conduzcan a materiales basados no sólo en TiO2 con propiedades mejoradas sino a otros materiales basados en este óxido y a otros óxidos inorgánicos binarios, los obtenidos por acoplamientos de óxidos binarios y ternarios, que se obtengan por procedimientos de síntesis distintos (o modificados) a los ya recogidos en la bibliografía, y cuya fotoactividad sea evaluada por el grupo del Subproyecto#1, sin que se descarte ensayos previos de actividad fotocatalítica en agua por el grupo del Subproyecto#2.

Entre los materiales que se pretenden sintetizar en el Subproyecto#2 (empleando métodos no-hidrotermales, hidrotermales y sol-gel) se contemplan: óxidos binarios (TiO2, ZnO, ZnO2, Fe2O3, WO3, Bi2O3, Ta2O5 , La2O3), óxidos binarios acoplados (TiO2-WO3, TiO2-ZnO, TiO2-ZnO2; TiO2-Ta2O5, TiO2-La2O3, ZnO-Fe2O3 y ZnO2-Fe2O3), óxidos ternarios (Bi2WO6, Bi2WO6-ZnO, Bi2WO6-ZnO2, Bi2WO6-Fe2O3, Bi2Ti2O7, ZnWO4, La2Ti2O7), contemplando la foto-deposición de metales (Pt, Ag, Au) en los sistemas que muestren una actividad fotocatalítica considerable (Semiconductores/Metal).

Los mejores sistemas evaluados se remitirán al grupo del Subproyecto#1 para el estudio de la viabilidad fotocatalítica en la eliminación de NOx,COVs, CO, CO2 y SO2 presentes en emisiones gaseosas.


Sistemas Catalíticos Estructurados para la Producción de Biocombustible



Investigador Principal: José Antonio Odriozola Gordón
Periodo: 01-01-2016 / 31-12-2018
Organismo Financiador: inisterio de Economía y Competitividad
Código: ENE2015-66975-C3-2-R
Componentes: María Isabel Domínguez Leal, Anna Dimitrova Penkova, Francisca Romero Sarria

Resumen [+]

La dependencia de nuestro actual sistema energético de las fuentes de combustibles fósiles y sus adversos efectos medioambientales están potenciando el desarrollo de fuentes de energía de origen renovable. Este es el caso de los biocombustibles de segunda generación. Los procesos de producción de combustibles a partir de biomasa lignocelulósica y residuos orgánicos son habitualmente catalíticos y se caracterizan por la necesidad de un intenso intercambio de calor asociado al elevado efecto térmico de las reacciones químicas implicadas, dificultad para minimizar simultáneamente las limitaciones difusionales y la caída de presión en los reactores convencionales de lecho fijo y, en ocasiones, por necesitar tiempos de contacto extremadamente cortos. Todo ello hace que las tecnologías catalíticas convencionales trabajen en condiciones no óptimas.

Los sistemas catalíticos estructurados, catalizadores estructurados y reactores de microcanales ofrecen excelentes oportunidades para superar estas limitaciones ya que permiten minimizar simultáneamente las limitaciones difusionales y la caída de presión, mejorar los flujos radiales de calor y materia y permitir tiempos de contacto muy cortos con elevadas eficiencias. Los monolitos de canales paralelos longitudinales, las espumas de porosidad abierta y las mallas metálicas son sustratos que pueden fabricarse a partir de numerosas aleaciones metálicas y con diferentes densidades de celda o poro. También pueden ser recubiertas de cualquier catalizador de interés, adaptándose así a los diferentes requerimientos de cada proceso. Por otro lado, los reactores de microcanales pueden proporcionar una intensificación del proceso sin igual que va acompañada de un excelente control de la temperatura, de la calidad de producto y con mejoras sustanciales en la seguridad del proceso.

El objetivo del proyecto es estudiar sistemas catalíticos estructurados para la producción de energía de origen renovable. En concreto, se estudiarán la síntesis de Fischer-Tropsch, la síntesis directa de dimetiléter y la producción del gas de síntesis que alimentará estos procesos mediante reformado de biogás y "producer gas".Además se estudiará la reacción de desplazamiento del gas de agua que resulta clave para el ajuste de la relación H2/CO en el gas de síntesis.

Se hará especial hincapié en la influencia de las características térmicas de los sistemas estructurados en su comportamiento catalítico. Para ello se estudiará el efecto de la densidad de celdas en monolitos, densidad de poros en espumas, luz de malla en mallas apiladas, tipo de aleación metálica, espesor del recubrimiento catalítico y geometría del sustrato (incluyendo en algunos casos reactores de microcanales).Se considerarán como fases activas catalizadores muy próximos al estado del arte.

El desarrollo de estos estudios se hará con el apoyo de tres tareas transversales lideradas por cada uno de los tres grupos participantes, pero en las que participarán todos ellos: la preparación de los sistemas catalíticos estructurados, la caracterización mediante técnicas avanzadas y los estudios de modelado y simulación. Mediante este proyecto se pretende generar un conocimiento que contribuya a expandir el actual campo de aplicación de los sistemas catalíticos estructurados hacia aplicaciones energéticas sostenibles que se verían beneficiadas por las ventajas que ofrecen estos sistemas en línea con el reto Energía segura, eficiente y limpia.


Desarrollo de procesos catalíticos y fotocatalíticos para la valorización del gas natural: activación y transformación de metano e hidrocarburos ligeros



Investigador Principal: Alfonso Caballero Martínez
Periodo: 1-01-2015 / 31-12-2017
Organismo Financiador: Ministerio de Economía y Competitividad
Código: CTQ2014-60524-R
Componentes: Juan Pedro Holgado Vázquez, Gerardo Colon Ibáñez, Rosa María Pereñiguez Rodríguez, Alberto Rodríguez Gómez

Resumen [+]

  En el presente proyecto se pretenden realizar diversos estudios y desarrollos relacionados con distintos procesos de activación y transformación de metano en moléculas de más valor añadido. Con este fin se estudiarán tanto procesos bien establecidos de conversión indirecta, a través de reacciones de reformado (RM) para la obtención de gas de síntesis, como distintos procesos de conversión directa, en concreto la oxidación directa a metanol (DOM) y la aromatización de metano (DAM).

    En lo que respecta a la reacción de reformado, se plantea el desarrollo de sistemas catalíticos con resistencia mejorada a los procesos de desactivación. Para ello se prepararán y caracterizarán nuevos catalizadores bimetálicos nanoestructurados de niquel depositados en soportes como ceria, alumina y alumina/ceria, así como soportes mesoporosos de tipo SBA-15, dopados con ceria y alumina. Como segundo metal se utlizarán cobalto o hierro. Paralelamente, se realizará un estudio de la reacción de reformado por vía fotocatalítica utilizando sistemas de Cu, Pt y Ni depositados en soportes activos clásicos como titania o ceria, así como otros de más reciente desarrollo, como son Ga2O3, nitruro de carbono o grafeno. En este caso, se pretende igualmente explorar las posibilidades de la activación fotoquímica para la reacción de oxidación preferencial de CO (foto-PROX) en presencia de hidrógeno, de utilidad en los procesos de purificación de hidrógeno procedente del gas de síntesis. Se incidirá en la preparación de sistemas con una estructura de de bandas apropiada para el control de esta oxidación selectiva de CO.

     En cuanto a los procesos de conversion directa, se estudiará la reacción de DOM usando O2, H2O2 o N2O como activadores de la reacción, en combinación con sistemas basados en Au/Pd, Fe, Cu y/o Ni depositados en soportes como zeolitas ZSM-5, grafeno y TiO2. En este último caso, utilizando Au/Pd como fase metálica activa en presencia de H2O2 como especie oxidante se planteará la posibilidad de combinar la síntesis in situ de agua oxigenada con la posterior oxidación directa de metano. Igualmente, se explorará el proceso de oxidación fotocatalítica de metano a metanol como una alternativa novedosa y altamente atractiva. En este caso, el uso de nuevos fotocatalizadores de oxidación como el BiVO4 así como la presencia de mediadores redox permitirán controlar la oxidación selectiva a metanol.

    Algunos sistemas estrechamente relacionados con los anteriores, y en particular los basados en Mo soportados en zeolitas ZSM-5 y MCM-22, se utilizarán para el estudio de la reacción de aromatización de metano. La proporción de aluminio, el porcentaje de molibdeno y su activación en la estructura microporosa del soporte, así como la adición de promotores como Ga, Tl o Pb serán algunas de las variables a optimizar para esta reacción. De forma paralela se podrá estudiar el proceso de aromatización fotoinducido, recientemente descrito por algunos autores.


Desarrollo de catalizadores biomórficos obtenidos a partir de biomasa residual para producción de hidrógeno y refino de bio-oil



Investigador Principal: Miguel Angel Centeno Gallego
Periodo: 1-01-2014 / 31-12-2017
Organismo Financiador: Ministerio de Economía y Competitividad
Código: ENE2013-47880-C3-2-R
Componentes: María Isabel Dominguez Leal, Carlos López Cartes, Leidy Marcela Martínez Tejada, Svetlana Ivanova

Resumen [+]

El objetivo principal del presente proyecto coordinado entre las universidades de Zaragoza y el Instituto de Ciencias de Materiales de Sevilla es el desarrollo de catalizadores metálicos soportados en carbones biomórficos (CB), para su posterior aplicación a procesos de producción de hidrógeno y de refino de bio-oil. La técnica de Mineralización Biomórfica es una innovadora herramienta capaz de sintetizar materiales inorgánicos funcionales utilizando como plantilla diversas estructuras formadas en procesos biológicos. Así, a partir de materiales lignocelulósicos (biomasa) se puede preparar una gran variedad de materiales cerámicos microestructurados. No obstante, la replicación de los distintos niveles jerárquicos existentes en los tejidos biológicos sigue siendo un gran reto a día de hoy. Para avanzar en esta línea, en este proyecto se va a abordar el estudio de la síntesis, caracterización y aplicación de catalizadores metálicos soportados en carbón biomórfico (Me/CB), con distribuciones de tamaño homogénea y porosidad jerarquizada.
La preparación de estos materiales se realiza mediante descomposición térmica en atmósfera reductora (o inerte) a alta temperatura, y elevadas velocidades de calentamiento, de un material lignocelulósico (e.g. celulosa, lignina, papel) impregnado con los precursores metálicos catalíticos. De esta manera, en una sola etapa, se obtiene un soporte carbonoso biomórfico con nanopartículas de metal dispersas en su superficie. Este método de síntesis presenta una extraordinaria versatilidad, puesto que además de poder utilizar diferentes materias primas de partida, se pueden obtener catalizadores de muy distintas composiciones y contenidos metálicos, así como su estructuración en dispositivos monolíticos y espumas. Como materias primas, además de celulosa, lignina o papel, se van estudiar biomasas agrícolas residuales.
Los catalizadores tipo Me/CB se pretenden aplicar en procesos de producción de hidrógeno (descomposición de hidrocarburos ligeros, de amoniaco y deshidrogenación de ácido fórmico), en la reacción de Water-Gas-Shift (WGS), y en distintas reacciones test de refino de bio-oil (conversión de acético a acetona, hidrogenación de vainillina y ciclohexeno y conversión de m-cresol a fenol).
 


Aprovechamiento de CO2 para la obtención de gas de síntesis en catalizadores



Investigador Principal: Miguel Angel Centeno Gallego
Periodo: 01-02-2013 / 31-01-2017
Organismo Financiador: Junta de Andalucía
Código: P11-TEP-8196 (Proyecto de Excelencia)
Componentes: Svetlana Ivanova, Maria Isabel Domínguez Leal, José Antonio Odriozola Gordón, Tomás Ramírez Reina, Francisca Romero Sarria

Resumen [+]

Hoy en día no existen dudas acerca de que la concentración de gases de efecto invernadero, en particular la de CO2, está aumentando de manera considerable en la atmósfera terrestre. Para evitar este aumento continuado se debe aumentar la eficiencia en la producción de energía, disminuir la intensidad del uso de las fuentes fósiles y, finalmente, potenciar la captura y secuestro del CO2. Todo esto debe conseguirse manteniendo el crecimiento económico y la calidad de vida. En consecuencia, si tenemos en cuenta el desarrollo de las naciones menos industrializadas y el intensivo consumo energético necesario para aumentar su nivel de vida, la captura y secuestro de CO2 parece la alternativa más favorable.
En el presente proyecto se propone la utilización del CO2 como materia prima para el reformado de gas natural como paso previo a la obtención de combustibles líquidos sintéticos. Usando tecnologías convencionales, esta propuesta sólo es económicamente viable asociada a grandes reservas de gas natural. Sin embargo, la tecnología de microcanales permite abordar la síntesis de combustibles sintéticos de forma discontinua y con capacidad de producción flexible de modo económicamente viable. Para ello, es necesario el diseño, caracterización y ensayo de catalizadores activos, selectivos y estables en la reacción de reformado de metano con vapor y CO2:


CO2 + 3CH4 + 2H2O  → 4CO + 8H2


La selección de estos catalizadores culminará con la estructuración de los mismos utilizando soportes metálicos con microcanales paralelos (micromonolitos) a fin de establecer las condiciones necesarias para, en un futuro, la construcción de reactores de microcanales.


Aprovechamiento de gas no convencional: Reactores de microcanales en GTL



Investigador Principal: José Antonio Odriozola Gordón
Periodo: 01-01-2013 / 31-12-2015
Organismo Financiador: Ministerio de Economía y Competitividad
Código: ENE2012-37431-C03-01
Componentes: Svetlana Ivanova, Anna Dimitrova Penkova, Tomás Ramírez Reina, Sandra Palma del Valle, Ara Muñoz Murillo, María Isabel Domínguez Leal, Francisca Romero Sarria

Resumen [+]

Existen en la actualidad fuentes de gas que podríamos agrupar bajo el calificativo de no-convencional que incluyen el que se encuentra confinado en formaciones geológicas de baja permeabilidad, el gas asociado al crudo, los pequeños yaciemientos en lugares remotos, el biogas producido en la digestión anaerobia de residuos y los denominados product gas generados en la gasificación de biomasa y en la combustión de alquitran. La composición de todas estas fuentes de gas es similar estando constituidas por una mezcla de metano y dióxido de carbono con cantidades inferiores de otros gases permanentes. La concentración de CO2 puede llegar a ser de hasta el 40% en volumen como ocurre con el gas asociado de algunos campos off-shore y el biogas producido por fermentación de residuos agrícolas. La valorización de este gas mediante el proceso GTL (Gas to Liquid) es una alternativa cuando su localización remota o distante de los gaseoductos no permite ser agregado a las fuentes convencionales o no puede ser consumido in situ, ya que los combustibles líquidos son más fáciles de almacenar y transportar y tienen aplicación directa en el transporte.
La tecnología GTL convencional no es aplicable ya que su viabilidad económica exige instalaciones y suministros a una escala elevadísima. Por ello, se está desarrollando esa misma tecnología en reactores de microcanales de pared catalítica que consiguen incrementar de forma notable el rendimiento de las unidades de producción de gas de síntesis y síntesis de Fischer-Tropsch (SFT), al poder trabajar con elevadas velocidades espaciales, mejorando el control de la temperatura y con ello de la selectividad y la seguridad del proceso; además, la naturaleza modular basada en la replicación de unidades simplifica de forma considerable el escalado del proceso, adaptándose bien a unidades de producción de gas no convencional que, por lo general, no son grandes.
En el presente proyecto se pretende desarrollar la tecnología de microcanales para el proceso GTL utilizando mezclas metano-dióxido de carbono para simular las fuentes de gas no convencional. Los estudios que hemos venido realizando sobre reactores de microcanales deberán ampliarse a condiciones de presión y temperatura más drásticas, lo que debe permitir validar y mejorar la selección de materiales para la construcción y las técnicas de unión.
La aplicación de esta tecnología requiere el desarrollo de nuevos catalizadores activos, selectivos y estables que se adapten a los procesos GTL en reactores de microcanales. Se diseñarán catalizadores para el reformado al vapor, el reformado seco y la oxidación parcial de metano para la producción de gas de síntesis, así como catalizadores SFT. Se construirán reactores de microcanales para el ensayo de dichos catalizadores, se obtendrán las ecuaciones cinéticas de los catalizadores seleccionados y se modelarán y simularán los reactores construidos.
 


Desarrollo de sistemas catalíticos nanoestructurados preparados mediante métodos sol-gel y de deposición fotoquímica para aplicaciones energéticas y medioambientales (NanoFotoCat)



Investigador Principal: Alfonso Caballero Martínez
Periodo: 01-01-2012 / 31-12-2014
Organismo Financiador: Ministerio de Ciencie e Innovación
Código: ENE2011-24412
Componentes: Gerardo Colón Ibáñez, Juan Pedro Holgado Vázquez, Sergio Obregón Alfaro, Rosa María Pereñiguez Rodríguez, Fátima Ternero Fernández

Resumen [+]

En el presente proyecto se plantea el desarrollo de una serie de catalizadores nanoestructurados basados en metales de transición tales como Ni, Cu, Au o Pd, y depositados en soportes activos (TiO2, CeO2, WO3, Fe2O3 y soportes mesoporosos como SBA-15 dopado con titania y ceria). Se utilizarán métodos de preparación convencionales (impregnación, deposición-precipitación, etc.), junto con procedimientos de síntesis de desarrollo más reciente, como métodos sol-gel y, muy especialmente, el denominado Fotodeposición Asistida Fotoquímicamente (Photochemical Assisted Deposition, PAD). De esta forma, esperamos controlar de manera rigurosa a la escala nanométrica tanto el tamaño de la partícula metálica y/o bimetálica, como la interacción metal-soporte. En el caso concreto del método PAD, uno de los objetivos principales del proyecto es el estudio y la optimización de las variables del proceso de deposición de manera que, además de controlar el tamaño de la partícula metálica desde diámetros en torno a 15nm hasta sistemas atómicamente dispersos sobre soportes activos como ceria o titania, nos permita diseñar la distribución de los metales en la partícula metálica, haciendo uso de procesos controlados de fotodeposición consecutivos y/o simultáneos de los metales. Esta metodología debe permitir la obtención de distribuciones metálicas de tipo core-shell o aleadas, lo que como es conocido, puede llegar a afectar de manera fundamental a las prestaciones catalíticas. Estas prestaciones serán comprobadas en diferentes reacciones de interés energético y/o medioambiental, tanto en fase gas como en fase líquida. Así, los sistemas basados en niquel y oro se utilizarán en las reacciones de reformado húmedo y seco de metano (Steam and Dry Methane Reforming, SRM/DRM) y la oxidación selectiva de CO (Preferential Oxidation of CO, PROX), respectivamente. Los sistemas mono y bimetálicos basados en paladio y paladio-oro serán utilizados para la optimización de la reacción de síntesis directa de agua oxigenada a partir de hidrógeno y oxígeno, realizada en fase líquida a alta presión. La correlación entre el estado físico-químico y la reactividad de los sistemas catalíticos nos permitirá aclarar aspectos fundamentales de los mecanismos de las reacciones heterogéneas propuestas.


Materiales Foto-Activos para el desarrollo de la Energía Solar en Procesos Fotocatalíticos de Interés Medioambiental



Investigador Principal: José Antonio Navío Santos
Periodo: 1-01-2012 / 31-12-2012
Organismo Financiador: Ministerio de Ciencia e Innovación
Código: CTQ2011-26617-C03-02
Componentes: Mª del Carmen Hidalgo López, Manuel Macías Azaña, Julie J. Murcia Mesa; Sebastián Murcia López

Resumen [+]

La fotocatálisis heterogenea ha mostrado sobradamente su potencial para destoxificación y desinfección de medios acuosos y gaseosos. Sin embargo, su desarrollo tecnológico ha sido muy limitado debido a una serie de dificultades que pueden agruparse en dos grupos principales:

1. Dificultades para separar el catalizador del medio al finalizar el proceso, para su reactivación y reutilización.

2. Bajo rendimiento del proceso, que sólo aprovecha un porcentaje muy pequeño de los fotones útiles, siendo estos además una pequeña parte del espectro natural.

En nuestra propuesta se coordinan tres subproyectos liderados por tres grupos que aunan amplia experiencia en: Síntesis, modificación y caracterización de materiales fotocatalíticos (principalmente el grupo de la Universidad de Sevilla), Preparación y caracterización de óxidos metálicos en lámina delgada sobre diferentes substratos(principalmente el grupo del CIEMAT) y Modificación, caracterización espectroscópica de centros activos y estudios de fotorreactividad en fase acuosa y gaseosa (principalmente el grupo de la ULPGC).

 

Sobre la base de esta experiencia acumulada y de las principales tendencias en el desarrollo de la fotocatálisisheterogénea, nuestro consorcio se plantea como objetivo central de este proyecto: Sintetizar materiales basados en TiO2, SnO2, ZnO y materiales ternarios tipo titanato de bismuto (BITs),  en forma de polvo con tamaño manométrico con alta actividad fotocatalítica y su fijación sobre sustratos adecuados (vidrio, membranas, láminas metálicas, etc.) recubiertos con películas delgadas de diferentes óxidos metálicos que faciliten el anclaje de estas partículas y/o actúen como semilla para la formación o cristalización de estas partículas, para poder utilizar estos sistemas de forma eficiente en procesos de descontaminación fotocatalítica en fase acuosa y gaseosa.


Desarrollo de nuevos procesos industriales basados en sistemas catalíticos para la obtención sostenible de ingredientes base en fragancias y aromas



Investigador Principal: Juan Pedro Holgado Vázquez
Periodo: 04-05-2011 / 31-12-2014
Organismo Financiador: Ministerio de Economía y Competitividad
Código: IPT-2011-1553-420000
Componentes: Alfonso Caballero Martínez, Víctor Manuel González de la Cruz, Rosa Pereñíguez Rodríguez, Gerardo Colón Ibáñez

Resumen [+]

En la actualidad, los procesos industriales utilizados para la transformación de muchos compuestos utilizados en el campo de las fragancias y los aromas ofrecen bajos rendimientos y generan una enorme cantidad de residuos peligrosos, que requieren varias etapas de segregación y tratamiento de los mismos durante el proceso. La mayor parte de estos procesos se basan en reacciones de oxidación/reducción de compuestos estequiometricos, o están basados en sistemas de catálisis homogénea, los cuales presentan inconvenientes asociados con la corrosión, la recuperación del catalizador de la mezcla de reacción y su regeneración para su posible reutilización. En este contexto “eco-amigable”, existe un interés creciente para el uso de oxidantes menos contaminantes, tales como el peróxido de hidrógeno o el oxígeno molecular, y la integración de dichos oxidantes en sistemas de catálisis heterogénea. Obviamente uno de los mayores retos que presentan las reacciones basadas en sistemas catalíticos es lograr el máximo rendimiento (producto de conversión por selectividad) con objeto de reducir el consumo de reactivos (materias primas), y minimizar los procesos de separación y eliminación de subproductos no deseados fruto de la ineficacia del proceso. En este tipo de reacciones (con compuestos principalmente orgánicos, muchos de origen natural), no es, en general, difícil obtener una alta conversión, pero dado que estos compuestos presentan multiples funcionalidades y/o puntos susceptibles de ser oxidados , el reto se centra en la obtención de una alta selectividad, generalmente incluso a nivel enantiomérico.

En el marco del proyecto, se han seleccionado procesos de interés en la industria cosmética y alimentaria, con objeto de conseguir el desarrollo a escala industrial de procesos basados en sistemas de catálisis heterogénea para la obtención de compuestos intermedios de gran valor añadido en el mercado de los perfumes y aromas, como son, entre otros, el proceso de obtención de la l-carvona a partir de la oxidación catalítica del d-limoneno.


Nuevos fotocatalizadores basados en compuestos de Bi3+ altamente fotoactivos en el visible



Investigador Principal: Gerardo Colon Ibáñez
Periodo: 11-03-2011 / 31-03- 2015
Organismo Financiador: Junta de Andalucía
Código: P09-FQM-4570
Componentes: M. Carmen Hidalgo López, José Antonio Navío Santos, Manuel Macías Azaña, Sebastián Murcia López

Resumen [+]

El objetivo principal de este proyecto es el desarrollo de una nueva generación de materiales nanoestructurados alternativos al TiO2 que presenten una alta fotoactividad en la región del visible y que puedan ser utilizados de forma competitiva y eficiente en procesos de tratamiento de efluentes líquidos y gaseosos mediante el aprovechamiento de la luz solar. El presente proyecto pretende desarrollar nuevos sistemas de nanocatalizadores heterogéneos basados en Bi3+ (Bi2WO4, Bi2MoO6, BiVO4, Bi3O4Cl, CaBi2O4, PbBi2Nb2O9,…) que presenten unas propiedades optoelectrónicas adecuadas para el aprovechamiento de la energía solar en el rango del visible (Fotocatálisis Solar) y que al mismo tiempo exhiban unas propiedades fisicoquímicas mejoradas que optimicen el proceso fotocatalítico desde el punto de vista de difusión y transferencia de portadores de carga fotogenerados.


Catalizadores nanoestructurados basados en Au para reacciones de oxidación selectiva



Investigador Principal: Juan Pedro Holgado Vázquez
Periodo: 1-01-2011 / 31-12-2011
Organismo Financiador: Ministerio de Ciencia y Tecnología
Código: CTQ2010-21348-C02-01
Componentes: Alfonso Caballero Martínez, Víctor Manuel González de la Cruz, Fátima Ternero Fernán-dez, Richard M. Lambert

Resumen [+]

El objetivo del proyecto es el desarrollo de catalizadores con base oro, con alta reactividad en los procesos de oxidación selectiva. En este contexto, se abordan reacciones tales como la oxidación selectiva del alcohol bencílico (y derivados) o la oxidación selectiva de CO.  esta última conectada con su aplicación en Catálisis Ambiental como es el control de la calidad del aire y en aplicaciones energéticas como la purificación de corriente de H2 procedente de procesos de reformado (PROX).

Las propiedades del oro, metal biocompatible y no tóxico, puede ser explotadas en catálisis cuando se usa en forma soportada y muy dispersa. Se pretende optimizar el rendimiento de los catalizadores mediante el control del tamaño, forma de las nanopartículas y su interacción con el soporte, en base a la “dependencia de la estructura” de estas reacciones.  Así, se preparan catalizadores basados en Au, doblemente nanoestructurados (tanto a nivel de la fase activa como del soporte) soportados sobre CeO2 y TiO2 (Al2O3 y SiO2 como referencia) mediante distintas estrategias de síntesis; evaluando sus propiedades mediante técnicas de caracterización avanzadas y evaluando su comportamiento en reactividad (en régimen estacionario y transitorio) en procesos de oxidación. En el mismo contexto, y considerando la reciente aparición de catalizadores bimetálicos (AuCu, AuPd) para estas reacciones con elevados rendimientos, se prepararan sistemas AuPt, AuCu y Au Ni con control del tamaño y la composición de la fase activa.


Reformado Catalítico de Glicerina



Investigador Principal: José Antonio Odriozola Gordón
Periodo: 01-01-2010 / 31-12-2012
Organismo Financiador: Junta de Andalucía
Código: P09-TEP-5454 (Proyecto de Excelencia)
Componentes: Luis F. Bobadilla Baladrón, Sylvia A. Cruz Torres, M. Isabel Domínguez Leal, Anna Dimitrova Penkova, Francisca Romero Sarria, Andrea Alvarez Moreno

Resumen [+]

Este proyecto pretende la producción de hidrógeno a partir del reformado de glicerina. La glicerina es el producto secundario principal en la producción de bio-diesel a través de la transesterificatión de ácidos grasos. Si tenemos en cuenta el desarrollo actual, la producción de bio-combustibles se estima en 9.9 Mtoe para 2010, lo que representa el 50% de los objetivos de la Unión Europea. Los sistemas de energía actuales necesita el desarrollo de modelos energéticos alter-nativos. El empleo de hidrógeno como vector energético representa una de esas alternativas, aunque para asegurar la sostenibilidad se requiere que el hidrógeno se produzca a partir de fuentes renovables. La principal ventaja del planteamiento que proponemos, aprovechamiento de la glicerina, reside en que además de sostenible el balance de carbono es prácticamente neutro. Además, su valorización debe conducir a aumentar la rentabilidad de las bio-refinerías que de otro modo se verían afectadas por el incremento de costes asociados a la eliminación de este producto.


Integración de reactores catalíticos de microcanales para la producción de hidrógeno a partir de alcoholes



Investigador Principal: José Antonio Odriozola Gordón
Periodo: 1-08-2009 / 31-07-2012
Organismo Financiador: Ministerio de Ciencia y Tecnología
Código: ENE2009-14522-C05-01
Componentes: Miguel Angel Centeno, Svetlana Ivanova, Francisca Romero Sarria, M.Isabel Domínguez, Sandra Palma, Oscar Laguna, Ana Penkova, Sylvia Cruz, W.Yesid Hernández, Luis Bobadilla

Resumen [+]

El uso masivo y generalizado de dispositivos eléctricos y electrónicos portátiles aumenta la necesidad de fuentes de potencia autónomas y eficientes, de hasta unos 50 We, capaces de reemplazar la tecnología actual basada en el uso de baterias. El uso de combustibles o productos químicos convencionales, hidrocarburos o alcoholes por ejemplo, es una alternativa prometedora cuando se combina con los recientes desarrollos en intensificación de procesos basados en la tecnología de reactores de microcanales. El desarrollo de la tecnología de microcanales para la producción de hidrógeno, in situ y a de-manda, a partir de alcoholes, se comenzó a estudiar en el proyecto anterior (MAT2006-12386-C05). Este estudio permitió la construcción de reactores de microcanales para las reacciones de reformado catalítico de metanol y oxidación preferente de CO (PROX) . En el presente proyecto se pretenden aplicar los conocimientos adquiridos para acoplar los microrreactores entre sí integrando flujos térmicos y materiales, escalarlos, y unirlos a una celda de combustible comercial de 50 We (PEMFC). En paralelo, se desarrollarán reactores de microcanales para el reformado catalítico de etanol y la reacción de desplazamiento del gas de agua (WGS) lo que permite aumentar la versatilidad el dispositivo diseñado. La viabilidad de estas fuentes de potencia autónomas requiere el estudio no sólo de la fabricación, escalado de los microreactores e integración de los flujos térmicos y materiales sino también explorar el uso de materiales de mayor disponibilidad (aceros ferríticos adaptados al uso), su durabilidad (aceros, catalizadores, soldaduras, juntas, …) y el desarrollo de un algoritmo de control para el conjunto formado por el procesador de combustible (reformado + eliminación de CO) y la pila de combustible.


Desarrollo de estrategias para la preparación y optimización de materiales altamente fotoactivos



Investigador Principal: José Antonio Navío Santos
Periodo: 01-01-2009 / 31-12-2011
Organismo Financiador: Ministerio de Ciencia y Tecnología
Código: CTQ2008-05961-C02-01
Componentes: Gerardo Colón Ibáñez, M. Carmen Hidalgo López, Manuel Macías Azaña, Marina Maicu

Resumen [+]

El objetivo general de este proyecto coordinado es “diseñar una nueva generación de materiales en forma de polvo con tamaño manométrico basados en TiO2, SnO2 y ZnO simples, mixtos y/o dopados con otros iones, con alta actividad fotocatalítica en el visible y su fijación en otros materiales (membranas, vidrios, arcillas y láminas metálicas) que permitan emplear-los, de manera eficiente y competitiva en procesos de descontaminación fotocatalítica de efluentes líquidos y gases contaminados”. La hipótesis fundamental de la que se parte es que existen pigmentos inorgánicos (tales como el TiO2, SnO2, ZnO, etc.) con actividad fotocatalítica en UV capaces de degradar de forma no selectiva a especies tóxicas presentes en nuestro medio ambiente. El reto es superar los problemas derivados de la utilización sólo de la parte UV del espectro solar y extender la respuesta hacia el visible, implementando al mismo tiempo, las propiedades fisicoquímicas de los fotocatalizadores. Para realizar este estudio se proponen dos bloques principales de actividad que serán el diseño y desarrollo de catalizadores heterogéneos de tamaño nanométricos altamente fotoactivos, basados en TiO2, SnO2 y ZnO que puedan hacer las transformaciones de degradación de contaminantes mediante el concurso de luz solar visible (Química Solar Medioambiental) y la inmovilización de nanopartículas de estos semiconductores, simples, mixtos y/o dopados, en soportes adecuados (membranas, vidrios, láminas metálicas, fibras, placas cerámicas, etc,) con el fin de desarrollar dispositivos fotocatalíticos con alta actividad para el tratamiento de contaminantes en gases y aguas, para la generación de superficies autolimpiables.


Producción de gas de síntesis e hidrógeno mediante reformado de hidrocarburo con catalizadores nanoestructurados de niquel



Investigador Principal: Alfonso Caballero Martínez
Periodo: 1-12-2007 / 30-11-2011
Organismo Financiador: Ministerio de Educación y Ciencia
Código: ENE2007-67926-C02-01
Componentes: Juan Pedro Holgado Vázquez, Agustín R. Gon-zález-Elipe, Victor Manuel González de la Cruz, Rosa Pereñiguez Rodríguez

Resumen [+]

Este proyecto coordinado de investigación, que puede considerarse como extensión de los anteriores ENE2004-01660 y ENE2004-06176, pretende la preparación de nuevos sistemas catalíticos,con tamaños de partícula discretos y con alta resistencia a la desactivación. El objetivo ultimo es la mejora de la reacción de reformado de hidrocarburos para producción de H2(+CO), principalmente metano y propano, al ser esta una reacción dependiente de la estructura, y por tanto sensible al tamaño de partícula.

Para ello, se prepararán diferentes series de nanopartículas de níquel de tamaño y morfología bien definidos, utilizando métodos ex-situ como la irradiación mediante plasma de microondas, líquidos iónicos, microemulsión inversa o la impregnación con modificación externa del soporte por sililación.

Estos métodos nos permitirán obtener partículas con un rango de tamaños muy amplio, desde menos de 10nm hasta valores entorno a los 100nm y con una estrecha distribución de tamaños de partícula.

La actividad catalítica de estas nanopartículas, una vez depositadas en soportes como ZrO2 or Al2O3, será evaluada en las reacciones de reformado de metano y propano; estableciendo una correlación estructura-reactividad. Se estudiarán con una especial atención los procesos de deposición de carbón sobre los catalizadores en condiciones de reacción, ya que son los principales responsables de la disminución en la eficiencia de estos sistemas catalíticos. El control estricto de la morfología de las nanopartículas metálicas nos permitirá, por tanto, correlacionar la cinética de estos procesos de desactivación con sus características estructurales. Por otro lado, estudiaremos el efecto en la mejora de las prestaciones catalíticas globales de la adición de promotores como Pt, Au, Sr, K, etc.

Alternativamente, se realizará un estudio de la reacción de reformado inducida por un plasma de microondas, con el fin último de desarrollar un sistema integrado térmico-plasma, que esperamos mejore las condiciones de reacción, reduciendo la temperatura necesaria y/o disminuyendo los procesos de deposición de coque sobre los catalizadores.


Diseño de sistemas fotocatalíticos con alta actividad en el visible para aplicaciones ambientales



Investigador Principal: Gerardo Colón Ibáñez
Periodo: 01-01-2007 / 31-12-2010
Organismo Financiador: Junta de Andalucía
Código: FQM-1406
Componentes: José Antonio Navío Santos, Manuel Macías Azaña, Carmen Hidalgo López, Marina Maicu

Resumen [+]

La Fotocatálisis ha demostrado ser una técnica muy eficiente en la oxidación de una gran variedad de sustratos en cortos tiempos de reacción. Es conocido que los catalizadores más utilizados, solo pueden ser activados por radiaciones menores de 390 nm, constituyéndose en una limitación para su empleo a mayor escala por el impedimento de usar luz solar. El objetivo principal de este proyecto se basa en el desarrollo en nuestro laboratorio de sistemas basados en TiO2 de alta eficiencia fotocatalítica en UV, capaz de degradar de forma no selectiva a especies tóxicas presentes en nuestro medio ambiente. El reto es superar los problemas derivados de la utilización sólo de la parte UV del espectro solar. El bloque central de la actividad de este proyecto consistirá en el desarrollo de sistemas de óxidos de Ti y Zn dopados, de forma que podamos obtener sistemas cuyo umbral de absorción esté en la región del visible. 

Así, desde el punto de vista de la mejora en las eficiencias de los procesos fotocatalíticos, es evidente que el diseño y desarrollo de fotocatalizadores alternativos al TiO2 es de un interés considerable. Se pretende la obtención de materiales altamente eficientes en procesos fotocatalíticos heterogéneos (en fase líquida y gaseosa) mediante la incorporación de distintos dopantes y la inmovilización de estos sistemas en distintos soportes. Para ello se abordarán distintas rutas de síntesis de polvo, y métodos de deposición. La evaluación la actividad fotocatalítica de los catalizadores se abordará estudiando procesos de fotooxidación de distintos compuestos orgánicos tóxicos (fenol y pigmentos orgánicos).


2017


Titulo: Synthesis and characterization of Rh/MnO2-CeO2/Al2O3 catalysts for CO-PrOx reaction
Autores: Martinez, TLM; Laguna, OH; Lopez-Cartes, C; Centeno, MA
Revista: Molecular Catalysis, 440 (2017) 9-18
resumen | texto completo


Rh/MnO2-CeO2/Al2O3 catalysts with different manganese-to-ceria ratios have been synthesized, characterized and tested in CO-PrOx reaction. The physicochemical properties of the solids were studied by XRD, Raman spectroscopy, BET surface area, H-2-TPR, TGA-DTG and TEM. The differences observed in the textural, structural and redox properties were related to the Mn-to-ceria ratio of the samples. The segregation of Mn species was observed at high Mn-to-Ce ratios. In opposite way, MnO2-CeO2 solid solutions were obtained at low Mn to Ce ones. In this last case, the physicochemical properties of the solids were favored by the intimate Rh-Ce-Mn contact. The effect of the Mn-Ce presence on Rh catalysts which promotes the catalytic behavior towards selective CO oxidation was observed to be better at low temperatures. At higher temperatures, Mn species promote the Reverse Water Gas Shift reaction, whilst ceria promotes the H-2 oxidation in the whole range of working temperatures.

Octubre, 2017 | DOI: 10.1016/j.mcat.2017.06.018

Titulo: Cobalt Carbide Identified as Catalytic Site for the Dehydrogenation of Ethanol to Acetaldehyde
Autores: A. Rodríguez-Gómez; J.P. Holgado; A. Caballero
Revista: ACS Catalysis, 7 (2017) 5243-5247
resumen | texto completo


Two cobalt catalysts, Co/SBA-15 and Co/SiO2, have been studied in steam reforming of ethanol (SRE). Besides the steam reforming products, ethoxide dehydrogenation to acetaldehyde is observed as one of the main reactions. Although by hydrogen treatment cobalt is reduced to the metallic state, under SRE conditions, a phase appears that has been identified as cobalt carbide and correlates with acetaldehyde production. These findings provide insights about the catalytic sites, for SRE, in cobalt catalysts. Comparison with previous results shows that these conclusions are not translatable to other cobalt catalysts, stressing the importance of the support on the catalytic behavior of cobalt.

Julio, 2017 | DOI: 10.1021/acscatal.7b01348

Titulo: Analysis of Ni species formed on zeolites, mesoporous silica and alumina supports and their catalytic behavior in the dry reforming of methane
Autores: Drobna, Helena; Kout, Martin; Soltysek, Agnieszka; Gonzalez-Delacruz, Victor M.; Caballero, Alfonso; Capek, Libor
Revista: Reaction Kinetics Mechanisms and Catalysis, 121 (2017) 255-274
resumen | texto completo


The presented investigation is focused on the analysis of Ni species formed on microporous (zeolites MFI and FAU) and mesoporous materials (Al-MCM- 41 and SBA-15) and alumina supports and their catalytic behavior in the dry reforming of methane. The paper lays emphasis on the relationship between the catalytic behavior of Ni-based catalysts and their textural/structural properties. Ni-based catalysts were prepared by wet impregnation (11 wt% of Ni) followed by calcination in air and reduction in hydrogen. The properties of Ni-based catalysts were also compared prior and after the catalytic tests. The critical role was played by the high value of the specific surface area and the high strength of the interaction between the Ni species and the support, which both determined the high dispersion and stability of metal Ni-0 particles. Ni-Al-MCM-41 and Ni-SBA-15 showed the values of the conversion of CO2 and CH4 above 90% (stable during 12 h). Slightly lower values of the conversion of CO2 and CH4 were observed over Ni-Al2O3 (also stable during 12 h). In contrast to these materials, Ni-MFI and Ni-FAU exhibited the worse metallic Ni-0 particles dispersion and very bad catalytic behavior.

Junio, 2017 | DOI: 10.1007/s11144-017-1149-3

Titulo: Critical Role of Oxygen in Silver-Catalyzed Glaser-Hay Coupling on Ag(100) under Vacuum and in Solution on Ag Particles
Autores: Orozco, N; Kyriakou, G; Beaumont, SK; Sanz, JF; Holgado, JP; Taylor, MJ; Espinos, JP; Marquez, AM; Watson, DJ; Gonzalez-Elipe, AR; Lambert, RM
Revista: ACS Catalysis, 7 (2017) 3113-3120
resumen | texto completo


The essential role of oxygen in enabling heterogeneously catalyzed Glaser–Hay coupling of phenylacetylene on Ag(100) was elucidated by STM, laboratory and synchrotron photoemission, and DFT calculations. In the absence of coadsorbed oxygen, phenylacetylene formed well-ordered dense overlayers which, with increasing temperature, desorbed without reaction. In striking contrast, even at 120 K, the presence of oxygen led to immediate and complete disruption of the organic layer due to abstraction of acetylenic hydrogen with formation of a disordered mixed layer containing immobile adsorbed phenylacetylide. At higher temperatures phenylacetylide underwent Glaser–Hay coupling to form highly ordered domains of diphenyldiacetylene that eventually desorbed without decomposition, leaving the bare metal surface. DFT calculations showed that, while acetylenic H abstraction was otherwise an endothermic process, oxygen adatoms triggered a reaction-initiating exothermic pathway leading to OH(a) + phenylacetylide, consistent with the experimental observations. Moreover, it was found that, with a solution of phenylacetylene in nonane and in the presence of O2, Ag particles catalyzed Glaser–Hay coupling with high selectivity. Rigorous exclusion of oxygen from the reactor strongly suppressed the catalytic reaction. Interestingly, too much oxygen lowers the selectivity toward diphenyldiacetylene. Thus, vacuum studies and theoretical calculations revealed the key role of oxygen in the reaction mechanism, subsequently borne out by catalytic studies with Ag particles that confirmed the presence of oxygen as a necessary and sufficient condition for the coupling reaction to occur. The direct relevance of model studies to a mechanistic understanding of coupling reactions under conditions of practical catalysis was reaffirmed.

Mayo, 2017 | DOI: 10.1021/acscatal.7b00431

Titulo: NO photooxidation with TiO2 photocatalysts modified with gold and platinum
Autores: Rodriguez, MJH; Melian, EP; Santiago, DG; Diaz, OG; Navio, JA; Rodriguez, JMD
Revista: Applied Catalysis B-Environmental, 205 (2017) 148-157
resumen | texto completo


In this study, a comparative analysis is made of TiO2 modified with Pt or Au in NO photoxidation under different radiation and humidity conditions. The metals were deposited on the TiO2 surface using two methods, photodeposition and chemical reduction. All catalysts were supported on borosilicate 3.3 plates using a dip-coating technique. These modified photocatalysts were characterized by X-ray diffraction analysis (XRD), UV-vis diffuse reflectance spectra (DRS), Brunauer-Emmett-Teller measurements (BET), transmission electron microscopy (TEM) and X-ray photoelectron spectrum analysis (XPS). It was found from the XPS results that Pt and oxidized Pt species coexist on the samples obtained by photodeposition and chemical reduction. In the case of Au, though other oxidation states were also detected the dominant oxidation state for both catalysts is Au. TEM results showed most Au-C particles are below 5 nm, whereas for Au-P the nanoparticles are slightly bigger. With UV irradiation, the Pt modified catalysts do not show any significant improvement in NO photocatalytic oxidation in comparison with the unmodified P25. For Au, both modified photocatalysts (Au-P and Au-C) exceed the photocatalytic efficiency of the unmodified P25, with Au-C giving slightly better results. The incorporation of metals on the TiO2 increases its activity in the visible region. 

Mayo, 2017 | DOI: 10.10161/j.apcatb.2016.12.006

Titulo: Deep insight into Zr/Fe combination for successful Pt/CeO2/Al2O3 WGS catalyst doping
Autores: Gonzalez-Castano, M; Ivanova, S; Ioannides, T; Centeno, MA; Odriozola, JA
Revista: Catalysis Science & Technology, 7 (2017) 1556-1564
resumen | texto completo


Efficient promotion of the Pt/CeO2/Al2O3 catalytic system was achieved by the addition of two different ceria promoters, Zr and Fe. From the exhaustive data analysis, the key features for enhanced catalytic performance and the roles of each doping metal are established. The combination of both doping agents manifests a synergistic effect reflected in noteworthy improvements in H2 reducibility. In addition, the catalyst's doping influences its chemisorptive properties, which is reflected in an increase of the easiness of carbonaceous species desorption, thus leading to superior catalyst resistance toward deactivation.

Abril, 2017 | DOI: 10.1039/c6cy02551j

Titulo: High UV-photocatalytic activity of ZnO and Ag/ZnO synthesized by a facile method
Autores: C. Jaramillo-Páez; J.A. Navío; M.C. Hidalgo; M. Macías
Revista: Catalysis Today, 284 (2017) 121-128
resumen | texto completo


ZnO nanoparticles have been successfully synthesized by a facile precipitation procedure by mixing aqueous solutions of Zn(II) acetate and dissolved Na2CO3 at pH ca. 7.0 without template addition. We have investigated the effect of annealing temperature in the final surface and structural properties. Photocatalytic studies were performed using two selected substrates, Methyl Orange and Phenol, both as single model substrates and in mixtures of them.

It has been stated that calcination treatments lead to a significant improvement in the photocatalytic properties of the studied samples, even better than TiO2(P25). As expected, the addition of Ag+ during the photocatalytic degradation of MO increases the reaction rate of the degradation of MO, giving a resultant Ag/ZnO photocatalyst which, after recovery, can be reused at least 18 times for the MO degradation tests, being even more photoactive than ZnO.

Abril, 2017 | DOI: 10.1016/j.cattod.2016.11.021

Titulo: Structural and catalytic properties of Au/MgO-type catalysts prepared in aqueous or methanol phase: application in the CO oxidation reaction
Autores: Hernandez, Willinton Y.; Alic, Funda; Navarro-Jaen, Sara; Centeno, Miguel A.; Vermeir, Pieter; Van der Voort, Pascal; Verberckmoes, An
Revista: Journal of Materials Science, 52 (2017) 4727-4741
resumen | texto completo


Au/MgO and Au/Mg(OH)(2)-type catalysts for CO oxidation reaction were prepared by using two different synthesis methods in presence of either an aqueous or methanol phase. The influence of the porous and morphological properties of the starting magnesium oxide supports was analyzed and correlated with the catalytic performances of the final gold-supported catalysts. It was found that the deposition of gold in the presence of methanol as a solvent avoids the total rehydration of the MgO support and maintains the textural and morphological properties of the starting oxides. The support synthesized by a surfactant-assisted hydrothermal route, having a combined meso-macroporous structure (i.e., MgO-P) showed a positive influence on the CO oxidation reaction as it favored the dispersion of gold and the surface-to-gas phase interaction during the catalytic process.

Abril, 2017 | DOI: 10.1007/s10853-016-0715-9

Titulo: Monitoring the Reaction Mechanism in Model Biogas Reforming by InSitu Transient and Steady-State DRIFTS Measurements
Autores: Bobadilla, LF; Garcilaso, V; Centeno, MA; Odriozola, JA
Revista: Chemsuschem, 10 (2017) 1193-1201
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In this work, the reforming of model biogas was investigated on a Rh/MgAl2O4 catalyst. In situ transient and steady-state diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) measurements were used to gain insight into the reaction mechanism involved in the activation of CH4 and CO2. It was found that the reaction proceeds through of an initial pathway in which methane and CO2 are both dissociated on Rh metallic sites and additionally a bifunctional mechanism in which methane is activated on Rh sites and CO2 is activated on the basic sites of the support surface via a formate intermediate by H-assisted CO2 decomposition. Moreover, this plausible mechanism is able to explain why the observed apparent activation energy of CO2 is much lower than that of CH4. Our results suggest that CO2 dissociation facilitates CH4activation, because the oxygen-adsorbed species formed in the decomposition of CO2 are capable of reacting with the CHx species derived from methane decomposition.

Marzo, 2017 | DOI: 10.1002/cssc.201601379

Titulo: Preferential oxidation of CO on a La-Co-Ru perovskite-type oxide catalyst
Autores: Pereniguez, R; Caballero, A; Ferri, D
Revista: Catalysis Communication, 92 (2017) 75-79
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A Ru-containing perovskite-type oxide La(Co,Ru)O3 of nominal composition LaCo0.8Ru0.2O3 was prepared by ultrasonic spray combustion and tested for the preferential oxidation of CO (PROX). EXAFS indicated that Ru adopted the coordination environment of Co in LaCoO3 while Co was present as LaCoO3 and Co3O4. PROX activity was replaced by CO hydrogenation activity above 250 °C. Short oxidation at 500 °C between temperature programmed reaction ramps did not restore the initial La(Co,Ru)O3 structure but generated a catalyst with improved PROX activity compared to the initial La(Co,Ru)O3. Under reductive PROX conditions the material experienced structural changes that improved its overall catalytic activity only if the catalyst was oxidized after each temperature programmed ramp.

Marzo, 2017 | DOI: 10.1016/j.catcom.2016.12.020

Titulo: Identification of Outer and Inner Nickel Particles in a Mesoporous Support: How the Channels Modify the Reducibility of Ni/SBA-15 Catalysts
Autores: Rodriguez-Gomez, A; Caballero, A
Revista: Chemnanomat, 3 (2017) 94-97
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Two different nickel supported on SBA-15 catalytic systems have been prepared by means of impregnation (Ni/SBA-15-ImU) and deposition-precipitation (Ni/SBA-15-DP) methodologies. Upon calcination, Ni/SBA-15DP presents a well-developed nickel phyllosilicate phase, which after reduction gives rise to a dispersed and homogeneous metallic phase, mainly located inside the 5 nm in diameter mesoporous structure of the support. On the contrary, as evidenced by XRD and a double temperature programmed reduction (TPR) peak, the Ni/SBA-15-ImU catalyst presents two different NiO phases, which after reduction in hydrogen generate nickel particles in a wide range of sizes. In situ XAS and XPS have unambiguously showed that the distinct TPR profiles obtained for each system are related with particles located in and out the mesoporous structure of the SBA-15 channels. The particles inside the porous are more difficult to reduce, clearly showing a kind of confinement effect of the SBA-15 mesostructure, modifying the reducibility of the NiO phase.

Febrero, 2017 | DOI: 10.1002/cnma.201600297

Titulo: Outstanding visible photocatalytic activity of a new mixed bismuth titanatate material
Autores: Zambrano, P; Sayagues, MJ; Navio, JA; Hidalgo, MC
Revista: Applied Surface Science, 394 (2017) 16-24
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In this work, a new photocatalyst based on bismuth titanates with outstanding visible photocatalytic activity was prepared by a facile hydrothermal method. The synthesised material showed visible activity as high as UV activity of commercial TiO2 P25 under the same experimental conditions for phenol degradation. A wide characterisation of the photocatalyst was performed. The material was composed of three phases; majority of Bi20TiO32 closely interconnected to Bi4Ti3O12 and amorphous TiO2. The high visible activity showed by this material could be ascribed to a combination of several features; i.e. low band gap energy value (2.1 eV), a structure allowing a good separation path for visible photogenerated electron-holes pairs and a relatively high surface area. This photocatalyst appeared as a promising material for solar and visible applications of photocatalysis.

Enero, 2017 | DOI: 10.1016/j.apsusc.2016.10.042

Titulo: Study of the E. coli elimination from urban wastewater over photocatalysts based on metallized TiO2
Autores: Murcia, JJ; Avila-Martinez, EG; Rojas, H; Navio, JA; Hidalgo, MC
Revista: Applied Catalysis B-Envionmental, 200 (2017) 469-476
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In this study, a series of photocatalysts based on TiO2 was tested in the elimination of Escherichia coli (E. coli) from urban wastewater. Firstly, TiO2 obtained by sol-gel method was modified by sulfation, and then gold or platinum nanoparticles were photodeposited on sulfated titania surface. Platinized samples were also prepared with different Pt content of 0.5 and 2 wt.%. The samples thus obtained were extensively characterized and it was found that sulfation considerably increases the S-BET value of TiO2 and promotes the anatase phase formation; it was also found that 0.5 wt.% Pt-TiO2 sample presents the lowest noble metal particle size and the best particle dispersion. All the photocatalysts synthesized have shown bactericidal effect and the results obtained by using bare and metalized TiO2 were considerably better than the results obtained with the commercial TiO2 P25 Evonic. Different light intensities were also evaluated in the photocatalytic tests and it was found that 120 W/m(2) leads to obtain the highest E. coli elimination from wastewater samples; however no total elimination of E. coli or other species of bacteria was achieved even after 5 h of photocatalytic treatment without catalyst. Total elimination of the E. coli was achieved after 3 h of photocatalytic reaction by using 120 Wim(2) of light intensity and 2 wt.% Pt-TiO2 as photocatalyst; no bacterial regrowth was observed even after 72 h. 

Enero, 2017 | DOI: 10.1016/j.apcatb.2016.07.045

Titulo: Gold promoted Cu/ZnO/Al2O3 catalysts prepared from hydrotalcite precursors: Advanced materials for the WGS reaction
Autores: Santos, JL; Reina, TR; Ivanova, S; Centeno, MA; Odriozola, JA
Revista: Applied Catalysis B-Envionmental, 201 (2017) 310-317
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Outstanding catalysts for the water was shift reaction are reported in this work. The combination of gold nanoparticles with Cu/ZnO/Al2O3 prepared from hydrotalcite-like precursors leads to very promising systems for pure hydrogen production. Full CO conversion is reached at temperatures as low as 180 degrees C. The key point seems to be the cooperation of Au and Cu and the optimal metal-oxide contact derived from the synthesis method. The high activity of gold for low temperature CO oxidation and the suitability of copper for the WGS results in a perfect synergy. Moreover the materials developed in this work present good stability and tolerance towards start/stop cycles an indispensable requisite for a realistic application in an integrated hydrogen fuel processor.

Enero, 2017 | DOI: 10.1016/j.apcatb.2016.08.017

Titulo: Gold catalysts screening in base-free aerobic oxidation of glucose to gluconic acid
Autores: Benitez, JJ; Heredia-Guerrero, JA; Cruz-Carrillo, MA; Barthel, MJ; Knicker, HE; Heredia, A
Revista: Catalysis Today, 279 (2017) 148-154
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Base-free aerobic oxidation of glucose in presence of Au/Al2O3, Au/CeO2, Au/CeO2(20 wt%)/Al2O3, Au/CeO2(25 wt%)/ZrO2 and Au/CeO2(50 wt%)/ZrO2 catalysts using molecular oxygen at atmospheric pressure is studied. Within the whole series high conversion and selectivity to gluconic acid are observed after 18 h of reaction at 120 degrees C. The activity and especially the selectivity changes are related to the support nature in a way that the higher the Lewis acidity of the support the lower the selectivity to gluconic acid and the higher the production of lactic acid. The highest yield to gluconic acid is obtained over Au/Al2O3 for which the influence of the reaction time, temperature and stirring rate are further evaluated and discussed.

Enero, 2017 | DOI: 10.1016/j.cattod.2016.06.046

Titulo: Mixed alpha-Fe2O3/Bi2WO6 oxides for photoassisted hetero-Fenton degradation of Methyl Orange and Phenol
Autores: Jaramillo-Paez, C; Navio, JA; Hidalgo, MC; Bouziani, A; El Azzouzi, M
Revista: Journal of Photochemistry and Photobiology A-Chemistry, 332 (2017) 521-533
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Mixed oxides, alpha-Fe2O3/Bi2WO6, were prepared using a mechanical mixing procedure by adding to the Bi2WO6 previously obtained by hydrothermal method the corresponding amount of a prepared alpha-Fe2O3, the latter obtained by thermal decomposition of Fe(NO3)center dot 9H(2)O. The physicochemical surface, structural, morphological characteristics and optical properties of the samples, single and mixed, were determined by BET, XRD, FE-SEM, XPS and UV-vis diffuse reflectance spectroscopy. UV-vis diffuse reflectance spectra showed that incorporating a 5%wt. of alpha-Fe2O3 to the corresponding amount of Bi2WO6 sample broadened the visible light absorption of Bi2WO6 as expected. The photocatalytic activity, of single and mixed catalysts, to degrade a selected dye such as Methyl Orange (MO) as well as the transparent substrate Phenol (Ph) was studied, in aqueous medium (pH 5.5) under UV and sun-like illumination conditions in the absence and presence of H2O2. In the present study the use of a alpha-Fe2O3/Bi2WO6/H2O2 system demonstrate much higher photocatalytic efficiency to degrade both MO and Ph than pristine Bi2WO6 or alpha-Fe2O3, single or mixed. Using the system alpha-Fe2O3/Bi2WO6/H2O2, around 85% of MO was degraded in 60 min under sun-like illumination whereas 100% was degraded in 60 min under UV-illumination. However, just around 30% of Ph was degraded in 120 min in the alpha-Fe2O3/Bi2WO6/H2O2 system under sun-like illumination whereas around a 95% was degraded in 90 min under UV-illumination. Under UV illumination, the generation of hydroxyl radicals is favorable; whereas under sun-like illumination, only the small fraction of the UV can produces the center dot OH. Under illumination, the H2O2 could react with photoinduced electrons from the photocatalysts leading to the production of hydroxyl radicals (center dot OH).

Enero, 2017 | DOI: 10.1016/j.jphotochem.2016.09.031

Titulo: Structuring Pt/CeO2/Al2O3 WGS catalyst: Introduction of buffer layer
Autores: Gonzalez-Castano, M; Ivanova, S; Laguna, OH; Martinez, LM; Centeno, MA; Odriozola, JA
Revista: Applied Catalysis B-Envionmental, 200 (2017) 420-427
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This work is devoted to the development of novel structured catalytic system for WGS reaction. The new concept is related to the presence of a pre-catalytic "buffer" layer formed by WGS-inert oxide, i.e. not involved in CO conversion, but able to increase the number of participating sites in water dissociation step during the reaction. The performance of the proposed systems appears to depend strongly on the stream composition, being its effect beneficial in highly reducing atmospheres making it ideal for cleanup application. An increment of the partial kinetic order for water species is observed and reveals the key role of the water activation for superior catalytic behavior. 

Diciembre, 2016 | DOI: 10.1016/j.apcatb.2016.07.039

2016


Titulo: Intensifying glycerol steam reforming on a monolith catalyst: A reaction kinetic model
Autores: Bobadilla, LF; Blay, V; Alvarez, A; Dominguez, MI; Romero-Sarria, F; Centeno, MA; Odriozola, JA
Revista: Chemical Engineering Journal, 306 (2016) 933–941
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In this work, a structured monolithic catalyst has been tested under a wide range of conditions (partial pressure, residence time, temperature and time-on-stream), with the aim of modeling its kinetic behavior and assessing its economic and upscaling potential. We have developed a sequential model to help us interpret both main trends and salient features. Unexpected behavior was found for certain parameter values, which led us to consider kinetic parasitic effects such as mass or heat transfer limitations. By independently invoking these effects, a conciliatory view of the results observed could not be reached. A combined explanation may prove successful, although overfitting could not be ruled out at this point. More importantly, however, the observed salient features of this stable and selective monolith catalyst may hold potential for process intensification of glycerol steam reforming, thus contributing to a more sustainable industry.

Diciembre, 2016 | DOI: 10.1016/j.cej.2016.08.021

Titulo: Influence of the ionic liquid presence on the selective oxidation of glucose over molybdenum based catalysts
Autores: Megias-Sayago, C; Carrasco, CJ; Ivanova, S; Montilla, FJ; Galindo, A; Odriozola, JA
Revista: Catalysis Today, 278 (2016) 82-90
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Two different approaches are proposed in this work in order to study the influence of the ionic liquid presence in the reaction of glucose oxidation by H2O2 in mild conditions. The ionic liquids are applied either as a solvent by using homogeneous Mo based catalyst, [Mo(O)(O2)2(H2O)n] complex, or by using it as an integral part of a heterogeneous catalyst, organic inorganic hybrids based on Mo Keggin structure. Both catalytic strategies resulted in acceptable glucose transformation degrees but lead to different oxidation products depending on the role of the ionic liquid. The hybrid approach restrains the number of the received products being the most selective one. A detailed study of the effect of the hybrid nature and reaction conditions is proposed in the second part of this study.

Diciembre, 2016 | DOI: 10.1016/j.cattod.2016.06.040

Titulo: Selectivity control in oxidation of 1-tetradecanol on supported nano Au catalysts
Autores: Martinez-Gonzalez, S; Ivanova, S; Dominguez, MI; Corberan, VC
Revista: Catalysis Today, 278 (2016) 113-119
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Selective oxidation of tetradecanol, a model higher fatty alcohol, on Au/CeO2-Al2O3 catalyst has been investigated to assess the factors that control selectivity. The analysis of the effect of operation conditions (temperature, run time and alcohol/metal (AIM) ratio) on catalytic performance revealed a quite complex reaction network, in which acid formation starts only after a certain level of conversion is reached. This level depends linearly on the total support surface available, indicating that it must be saturated by species generated by the reaction itself to allow acid formation to start. Addition of water to reaction medium did not modify this level, indicating that such species is not adsorbed water, as previously hypothesized, but probably spilled over hydrogen species. The resulting drastic change in the selectivity trends makes the ratio A/M a critical factor to control selectivity to aldehyde and to acid. Selectivity to ester is less sensible to operation parameters. It is noteworthy that aldehyde yields up to 27% with 90% selectivity, and acid yields up to 40% with 81% selectivity can be reached by proper selection of operation parameters.

Diciembre, 2016 | DOI: 10.1016/j.cattod.2016.06.019

Titulo: WGS and CO-PrOx reactions using gold promoted copper-ceria catalysts: "Bulk CuO-CeO2 vs. CuO-CeO2/Al2O3 with low mixed oxide content"
Autores: Reina, TR; Ivanova, S; Laguna, OH; Centeno, MA; Odriozola, JA
Revista: Applied Catalysis B-Environmental, 197 (2016) 62-72
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A copper-ceria bulk catalyst has been compared to a series of catalysts designed according to the as called "supported approach", corresponding to the dispersion of low content mixed copper-ceria oxide on alumina matrix. The principal characteristics of both types of catalysts are contemplated and the differences in their electronic and redox properties discussed in details. As a plus, the gold metal promotion of the catalysts is also envisaged. The advantages of the systems in the CO clean up reactions, WGS and CO-PrOx are commented. While the WGS activity appears to be ruled especially by the Cu/Ce surface to volume ratio, the CO-PrOx reaction is governed by the CuO loading. Gold addition provides benefits only at the low temperature WGS regime. Very importantly, the supported systems are always superior to the bulk configuration in terms of specific activity, a key factor from the catalyst's design perspective. 

Noviembre, 2016 | DOI: 10.1016/j.apcatb.2016.03.022

Titulo: Recycling of construction and demolition waste generated by building infrastructure for the production of glassy materials
Autores: Dominguez, A; Dominguez, MI; Ivanova, S; Centeno, MA; Odriozola, JA
Revista: Ceramics International, 42 (2016) 17217-175223
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The use of waste materials generated by construction and demolition industry to yield valuable glassy materials, i.e. enamel for glazed ceramic tiles and cellular glasses is presented in this study. Both types of materials are produced by one-step treatment at moderate temperatures after simple waste chemical composition adjust. The enamels are manufactured directly from the initial waste powder by melting, while the expanded materials result from mixing of the vitreous material obtained after waste vitrification with an adequate foaming agent and posterior thermal treatment. Through the manuscript the feasibility of one step production of second generation profit materials is discussed in order to help achieving sustainable development and environmental protection.

Noviembre, 2016 | DOI: 10.1016/j.ceramint.2016.06.157

Titulo: Forced deactivation and postmortem characterization of a metallic microchannel reactor employed for the preferential oxidation of CO (PROX)
Autores: Laguna, OH; Dominguez, MI; Centeno, MA; Odriozola, JA
Revista: Chemical Engineering Journal, 302 (2016) 650-662
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This manuscript is one of the few works presenting evidences of the effect of prolonged use of a microreactor. Our reactor has been designed for the PROX reaction. Near to 550 h of operation under different feed-streams, including CO2 and H2O, in the 100-300 degrees C temperature range, and several regeneration cycles, and a final forced deactivation during similar to 360 h resulted in the permanent loss of activity of the microreactor. This could be attributed to some phenomena whose have compromised the chemical nature of the catalyst and that of the reactor including: displacement of the coating to the mouth of the channels, detachments and cracks of the catalytic layer, migration of some elements of the metallic substrate to the surface (Fe, Cr, Y), and deposition of carbonaceous species from the reaction over the catalytic layer and/or the metallic substrate. Furthermore, sulfur compounds were detected in both inlet and outlet zones of the microreactor, coming probably from a lubricant applied over the screws that sealed the assembling of the microreactor. 

This is a first approach for understanding possible effects of deactivation during long-term applications of a microreactor in the PROX reaction that could be considered as a case study useful for future designs of this kind of devices. The presented information could be extrapolated to similar reactions where thermal treatments along with highly corrosive atmospheres would be applied, in order to carry out a more appropriate design of future generations" of microreactors, with a longer useful life. For that purpose not only the adequate selection of the catalysts must be done, but also the adequate choice of the fabrication material of the reactors is needed. 

Octubre, 2016 | DOI: 10.1016/j.cej.2016.05.104

Titulo: Au-supported on Fe-doped ceria solids prepared in water-in-oil microemulsions: Catalysts for CO oxidation
Autores: Laguna, OH; Centeno, MA; Boutonnet, M; Odriozola, JA
Revista: Catalysis Today, 278 (2016) 140-149
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Gold catalysts were synthesized by deposition-precipitation employing Fe-doped ceria systems, previously obtained by means of the water-in-oil microemulsions methodology with different iron contents (10, 25 and 50 Fe at.%). The final catalysts were tested in the CO oxidation reaction in presence of H2. After gold deposition the crystalline structure of the supports was not altered. Moreover no XRD lines associated to gold were detected, indicating its high dispersion. Solid solution was generated in all samples, although the segregation of iron oxide was detected for the material with the highest iron loading. This phenomenon was then enhanced for the corresponding gold catalyst that also presented sintering of the gold nanoparticles.

Strong interaction between gold and the oxygen vacancies of the supports was demonstrated, as well as the promotion of the reducibility of surface Ce4+ and Fe3+species at low temperatures. A remarkable promotion of the CO conversion at lower temperatures respect to that of the supports was observed for the gold catalysts. Below 120 °C, lower the amount of iron incorporated, higher the catalytic performance of the catalyst. This behaviour is closely related not only to a high gold dispersion but also to the ability for creating additional oxygen vacancies in the support, required for the CO oxidation reaction.

Octubre, 2016 | DOI: 10.1016/j.cattod.2016.05.059

Titulo: Au/CeO2 Catalysts: Structure and CO Oxidation Activity
Autores: Centeno, MA; Reina, TR; Ivanova, S; Laguna, OH; Odriozola, JA
Revista: Catalysts, 6 (2016) 158
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In this comprehensive review, the main aspects of using Au/CeO2 catalysts in oxidation reactions are considered. The influence of the preparation methods and synthetic parameters, as well as the characteristics of the ceria support (presence of doping cations, oxygen vacancies concentration, surface area, redox properties, etc.) in the dispersion and chemical state of gold are revised. The proposed review provides a detailed analysis of the literature data concerning the state of the art and the applications of gold–ceria systems in oxidation reactions.

Octubre, 2016 | DOI: 10.3390/catal6100158

Titulo: Liquid-phase oxidation with hydrogen peroxide of benzyl alcohol and xylenes on Ca-10(PO4)(6)(OH)(2) - CaWO4
Autores: Dominguez, MI; Cojocaru, B; Tudorache, M; Odriozola, JA; Centeno, MA; Parvulescu, VI
Revista: Comptes Rendus Chimie, 19 (2016) 1156-1165
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A W-containing apatite (W/HAp) catalyst was prepared following a hydrothermal synthesis route and served as a model catalyst. Crystallographic analysis indicated that the resulting material contained hydroxyapatite, Ca10-3xWx(PO4)(6)(OH)(2), W-hydroxyapatite, calcium tungstate, CaWO4, and tricalcium phosphate, Ca-3(PO4)(2). The catalyst was investigated in liquid phase oxidation of benzyl alcohol and xylenes using hydrogen peroxide as an oxidant. For comparison, commercial calcium phosphate, hydroxyapatite and CaWO4 were tested in the same reaction. Calcium phosphate and hydroxyapatite appeared as inactive and decomposed hydrogen peroxide non-selectively. A moderate activity but low hydrogen peroxide efficiency was observed for the CaWO4 phase. In contrast, the W/HAp catalyst showed a reasonable activity and a better hydrogen peroxide efficiency in the oxidation of benzyl alcohol and xylenes. This new W/HAp catalyst showed, after six cycles, losses of the activity below 15% compared to the fresh catalyst with no effect on the selectivity. It is noteworthy that ICP-OES analyses showed no tungsten leaching that is the main advantage of this catalyst. 

Octubre, 2016 | DOI: 10.1016/j.crci.2015.10.013

Titulo: Growth of carbonaceous nanomaterials over stainless steel foams. Effect of activation temperature
Autores: Latorre, N; Cazana, F; Sebastian, V; Royo, C; Romeo, E; Centeno, MA; Monzon, A
Revista: Catalysis Today, 273 (2016) 41-49
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Some of the problems that occur during the operation of chemical reactors based of structured catalytic substrates, as monoliths, foams, membranes, cloths, fibres and other systems, are related to the preparation of long term stable coatings. Frequently, the deposition of the catalytic layer is carried out by washcoating, requiring this step a cautious attention, especially in the case of complex geometries, like of that of foams or cloths. In the case of the deposition of layers of carbonaceous materials (CNMs), an alternative route, avoiding the washcoating, it is their direct growth by catalytic decomposition light hydrocarbons (also called CCVD), over the surface of the metallic substrate. In this case, if the metallic substrate is of stainless steel, it already contains the catalytic active phases like Fe and Ni. 

In order to optimize the process of CNMs growth over structured metallic substrates, we are studying the effect of the main operational variables of the ethane decomposition reaction on stainless steel foams. In this contribution we present a study of the influence of the temperature of the activation (oxidation and reduction) stage on the type and morphology of the carbonaceous materials formed. The results obtained allow us to determine the optimal operating conditions to maximize the amount and the selectivity of the process to obtain a given type of CNM.

Septiembre, 2016 | DOI: 10.1016/j.cattod.2016.02.063

Titulo: Photocatalytic Escherichia coli inactivation by means of trivalent Er3+, Y3+ doping of BiVO4 system
Autores: Adan, C; Marugan, J; Obregon, S; Colon, G
Revista: Applied Catalysis A-General, 526 (2015) 126-131
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BiVO4 samples doped with different contents of Er3+ and Y3+ were prepared by a simple surfactant free hydrothermal method. X-ray diffraction reveals that the doped materials consist of a heterogeneous structure formed by a mixture of tetragonal and monoclinic phases, being found Er3+ and Y3+ co-doping clearly stabilize the tetragonal structure of BiVO4. The monoclinic BiVO4 samples shows a strong absorption in the visible light region leading to band-gap values of around 2.4eV while the tetragonal BiVO4 displays higher band-gap values of 2.9 eV. The photocatalytic activity of the catalysts was investigated for the oxidation of methanol and inactivation of Escherichia coli showing that all the BiVO4 catalysts are photocatalytically active in the oxidation of methanol and are able to inactivate more than 99.99% of bacteria not only under UV light but also under visible light irradiation. The results revealed that the co-doping of Er3+ and Y3+ into BiVO4 exhibited enhanced photocatalytic activity for methanol oxidation under simulated solar light irradiation. The inactivation of E.coli show similar results for the doped systems although in relative terms of activity the Er3+,Y3+-BiVO4 sample show a better use of the visible light, leading to a higher activity than P25-TiO2.

Septiembre, 2016 | DOI: 10.1016/j.apcata.2016.08.002

Titulo: Impact of structured catalysts in amine oxidation under mild conditions
Autores: Latorre, N; Cazana, F; Sebastian, V; Royo, C; Romeo, E; Centeno, MA; Monzon, A
Revista: Catalysis Today, 273 (2016) 266-272
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A structured graphene/graphite catalyst grown on a commercial austenitic stainless steel sheet providing a micromonolith was obtained by submitting the nude stainless steel structure to a carbon-rich atmosphere (first 300 mL/min of a reductive H-2/N-2 (1:1) flow, then to 180 mL/min of a CH4/H-2 (1:5)) at high temperature (900 degrees C) for 2 h. The preparation procedure resulted in a homogenous surface coated with a carbon-rich film as observed by EDX and SEM images. Further characterizations by Raman spectroscopy revealed characteristic Raman lines of graphene and crystalline graphite disposed in a hierarchical organization. The disposal of the obtained surface layers was also confirmed by grazing incidence X-ray diffraction. Besides this, XRD indicated the overlapping diffraction lines of graphite, cementite and M7C3 carbides. The graphene nature of the outermost layer was also confirmed by XPS. The catalytic behavior of the structured graphene/graphite catalyst was evaluated in the selective oxidation of heptylamine. At 200 degrees C it afforded a total conversion with a combined selectivity in heptanonitrile and N-heptylidene-heptylamine of 67% (10% heptanonitrile) that corresponds indeed to a very efficient system in the absence of any metal. Kinetic experiments with the scope to calculate the activation energies were also performed. 

Septiembre, 2016 | DOI: 10.1016/j.cattod.2016.05.001

Titulo: Photocatalytic removal of patent blue V dye on Au-TiO2 and Pt-TiO2 catalysts
Autores: Vaiano, V; Iervolino, G; Sannino, D; Murcia, JJ; Hidalgo, MC; Ciambelli, P; Navio, JA
Revista: Applied Catalysis B: Environmental, 188 (2016) 134-146
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In this work it was studied the efficiency of a photocatalytic process for the removal of patent blue V. This dye is very difficult to remove by conventional treatments such as adsorption or coagulation therefore the photocatalytic process is a very interesting alternative for the removal this dye mainly because it does not require expensive oxidants and it can be carried out at mild temperatures and pressures. In this work it was tested the efficiency of Au-TiO2 and Pt-TiO2 photocatalysts in the Patent blue V removal. The Au-TiO2 catalysts were prepared by two different methods: chemical reduction and photochemical deposition; Pt-TiO2 catalysts were obtained only by photochemical deposition. In the synthesis of the catalysts prepared by photochemical deposition, it was evaluated the influence of some parameters, such as deposition time and the intensity of the light source over the physicochemical properties and photocatalytic activity of the materials obtained. An analysis of the effect of the catalyst dosage and initial patent blue V concentration over the dye degradation efficiency was also attempted. 
In general, it was observed that the presence of Au or Pt on TiO2 enhances the patent blue V photodegradation; it was found that noble metal particle size and distribution on TiO2 surface are important factors influencing the dye removal. The highest dye degradation was obtained over the Au-TiO2 catalyst prepared by photochemical deposition, using high light intensity and 15 min of deposition time during the synthesis. A discoloration and a total organic carbon (TOC) removal of 93 and 67% respectively, were obtained over this material after 180 min of UV irradiation. These values are higher than that the obtained on S-TiO2 (discoloration and TOC removal of about 25% and 3%, respectively).

Julio, 2016 | DOI: 10.1016/j.apcatb.2016.02.001

Titulo: Photocatalytic hydrogen production from degradation of glucose over fluorinated and platinized TiO2 catalysts
Autores: Iervolino, G; Vaiano, V; Murcia, JJ; Rizzo, L; Ventre, G; Pepe, G; Campiglia, P; Hidalgo, MC; Navio, JA; Sannino, D
Revista: Journal of Catalysis, 339 (2016) 47-56
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The present work reports the renewable hydrogen production by photocatalytic degradation of glucose over commercial and home prepared TiO2 modified by the simultaneous presence of fluorine and Pt (Pt-F-TiO2). The obtained materials were widely characterized by different techniques (XRD, SBF, UV-Vis DRS, XRF, SEM and TEM) and it was found that surface area, anatase/rutile ratio and the distribution and size of the platinum particles are important factors influencing the effectiveness of these materials in the H-2 production. The photocatalytic H-2 production from the glucose solution was 97 mu mol of H-2 after 3 h of irradiation on home prepared TiO2 modified by F and Pt addition, while a lower value corresponding to 31 mu mol of H-2 was obtained on commercial TiO2 modified by F and Pt, after 3 h of irradiation. The hydrogen production rate increased by decreasing the initial pH of solution reaching the highest value of about 590 mu mol h(-1) g(-1) after 3 h of irradiation time at pH = 2. Accordingly, sugar containing wastewaters from food industry has the potential for producing hydrogen by photocatalytic process while removing organics before disposal or reuse. 

Julio, 2016 | DOI: 10.1016/j.jcat.2016.03.032

Titulo: The role of Au, Cu & CeO2 and their interactions for an enhanced WGS performance
Autores: Reina, TR; Ivanova, S; Centeno, MA; Odriozola, JA
Revista: Applied Catalysis B: Environmental, 187 (2016) 98-107
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The WGS reaction over multicomponent Au/Ce1-xCuxO2/Al2O3 catalysts is studied in this work. The systems are carefully designed aiming to take advantage of every active phase included in the formulation: gold, ceria and copper. Special emphasis is given to the CeO2-CuO synergy and its influence on the displayed catalytic performance with and without gold. To this aim a meaningful correlation between the physicochemical properties of the mixed materials and their activity/stability is proposed. In general terms the developed catalysts present high activity under realistic WGS reaction conditions, with fairly good long term stability. In addition, the systems successfully withstand start-up/shut-downs situations, indispensable requisite for real applications in the field of pure hydrogen production for fuel cell goals. 

Junio, 2016 | DOI: 10.1016/j.apcatb.2016.01.031

Titulo: In-situ hydrogasification/regeneration of NiAl-hydrotalcite derived catalyst in the reaction of CO2 reforming of methane: A versatile approach to catalyst recycling
Autores: Abdelsadek, Z; Sehailia, M; Halliche, D; Gonzalez-Delacruz, VM; Holgado, JP; Bachari, K; Caballero, A; Cherifi, O
Revista: Journal of CO2 Utilization, 14 (2016) 98-105
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A novel approach describing the in-situ regeneration of NiAl hydroalcite derived catalyst between two cycle reaction systems of CO2 reforming of methane, also known as dry reforming of methane (DRM) is described herein. The catalyst was initially prepared by co-precipitation method at pH = 11 and calcined at 450 degrees C for 6 h. The obtained material was characterized using X-ray diffraction (XRD) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, Brunauer-Emmett-Teller (BET), atomic absorption spectroscopy (AAS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetry (TG/ATD) and temperature programmed reduction (TPR-H-2) techniques. Following treatment of our catalyst under DRM conditions, the catalyst was subjected to in-situ hydrogasification conditions to promote regeneration followed by a second DRM cycle. An increase of 15.7% in the conversion of CH4 and 17.3% in the conversion of CO2 was attained, while the ratio of resulting H-2/CO augmented by 14%. The ratio of H-2 consumed over the course of two hours hydrogasification, to that generated over ten hours of DRM, was 9.6%. The small particle sizes of resulting Ni degrees species as well as their high stability were both key factors contributing to the increase in the amount of H-2/CO produced prior to and after regeneration. 

Junio, 2016 | DOI: 10.1016/j.jcou.2016.03.004

Titulo: Nickel catalyst with outstanding activity in the DRM reaction prepared by high temperature calcination treatment
Autores: Smolakova, L; Kout, M; Capek, L; Rodriguez-Gomez, A; Gonzalez-Delacruz, VM; Hromadko, L; Caballero, A
Revista: International Journal of Hydrogen Energy, 41 (2016) 8459-8469
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The catalytic performance of some Ni-Ce/Al2O3 catalytic systems (11 wt.% Ni and 3 wt.% Ce) were checked after being submitted to different calcination and reduction treatments. It was found that, the reduced Ni-Ce/Al2O3 catalysts were more active and stable in the dry reforming reaction of methane than thecorresponding not-reduced catalysts. This high activity was initially connected with the smaller size of pre-reduced Ni species, which at the same time leads on to the formation of filamentous carbon. The best overall performance was obtained for the reduced catalyst after being calcined at 1000 degrees C. This catalyst presents a very high stability, a low level of carbon formation, maintaining the nickel particle size constant during reaction. Surprisingly, although its reduction degree is only 12% at 750 degrees C, its catalytic activity is similar to the full reduced catalysts. So, the small number of reduced metallic particles of this catalyst shows a very high activity, much higher than the other catalysts.

Junio, 2016 | DOI: 10.1016/j.ijhydene.2016.03.161

Titulo: Promoting effect of Sn on supported Ni catalyst during steam reforming of glycerol
Autores: Bobadilla, LF; Romero-Sarria, F; Centeno, MA; Odriozola, JA
Revista: International Journal of Hydrogen Energy, 41 (2016) 9234-9244
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The promoting effect of Sn on the catalytic performance of supported Ni catalyst in the reaction of glycerol steam reforming was studied. The physico-chemical properties of the prepared samples were investigated by X-ray fluorescence (XRF), BET surface area, in situ X-ray diffraction (XRD), laser Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and temperature-programmed oxidation (TPO) techniques. The characterization results of the samples after reduction treatment (in the same conditions than the activation before catalytic activity measurements) revealed the formation of NiSn alloy. The Sn-doped catalyst exhibited a high activity and it was demonstrated that the Sn addition increase the catalyst stability and durability by decreasing the coke deposition.

Junio, 2016 | DOI: 10.1016/j.ijhydene.2016.04.119

Titulo: The role of carbon overlayers on Pt-based catalysts for H-2-cleanup by CO-PROX
Autores: Romero-Sarria, F; Garcia-Dali, S; Palma, S; Jimenez-Barrera, EM; Oliviero, L; Bazin, P; Odriozola, JA
Revista: Surface Science, 648 (2016) 84-91
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In this work, we analyze the effect of the activation method on the catalytic activity of Pt-based catalysts supported on alumina in the PROX reaction. For this, model Pt/Al2O3 catalysts with variable amounts of acetic acid were prepared and their thermal evolution studied by FTIR spectroscopy. From the analysis of the nature of the platinum surface upon acetic acid decomposition and the gas phase evolved products, we have demonstrated the formation of partially hydrogenated carbon overlayers that tailor the activity of Pt-based catalysts in the PROX reaction. 

Junio, 2016 | DOI: 10.1016/j.susc.2015.12.017

Titulo: O-2-assisted Water Gas Shift reaction over structured Au and Pt catalysts
Autores: Gonzalez-Castano, M; Reina, TR; Ivanova, S; Tejada, LMM; Centeno, MA; Odriozola, JA
Revista: Applied Catalysis B: Enviromental, 185 (2016) 337-343
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Platinum and gold structured catalysts were compared as active phases in classical and O2-assisted Water Gas Shift (WGS) reaction. Both metals were supported on iron-doped ceria mixed oxide and then, structured on metallic micromonolithic devices. As expected the WGS activity of both micromonoliths is conditioned by the nature of the noble metals being Pt the most active metal in traditional conditions. However, the addition of oxygen to the classical water gas feed turns the balance in favor of the gold based catalysts, being the presence of gold responsible for an excessive improvement of the catalytic activity.

Mayo, 2016 | DOI: 10.1016/j.apcatb.2015.12.032

Titulo: Cascade charge separation mechanism by ternary heterostructured BiPO4/TiO2/g-C3N4 photocatalyst
Autores: Obregon, S; Zhang, YF; Colon, G
Revista: Applied Catalysis B: Enviromental, 184 (2016) 96-103
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A complex ternary BiPO4/TiO2/gC(3)N(4) heterostructure has been obtained from a simple impregnation method having good photoactivities for the degradation of phenol under solar-like irradiation. From the wide structural, surface and electronic characterization, we have stated that the formation of the ternary heterojunction notably affect photoactivity of pristine TiO2. Thus, the best result for the binary system was obtained for 70 wt%TiO2-30 wt% BiPO4 system. The incorporation of gC(3)N(4) leads to a further improvement on the photocatalytic activity when it is specifically done over TiO2. By means of photoluminescence spectroscopy and reactive oxygen species formation test, we propose that the effective charge carrier separation is taking place through a cascade-driven electronic mechanism. Therefore, by choosing the adequate band-engineering tailoring an important improved photoactivity can be achieved. 

Mayo, 2016 | DOI: 10.1016/j.apcatb.2015.11.027

Titulo: Towards the hydrogen production by photocatalysis
Autores: Colon, G
Revista: Applied Catalysis A-General, 518 (2016) 48-59
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Nowadays, problems derived from climate change urgently demand us to focus our attention on new alternatives to fossil fuels. Within this framework, the photocatalytic production of hydrogen as a clean fuel from oxygenates arises as a necessary option that must be considered. Thus, the development of highly efficient photocatalyst is crucial in order to achieve a viable technology under the industrial point of view. For this sake, it is necessary to understand the principles of photoreforming reaction. In this brief review we will revisit the different photocatalytic materials proposed in the literature highlighting on the role of different co-catalysts.

Mayo, 2016 | DOI: 10.1016/j.apcata.2015.11.042

Titulo: Nanogold mesoporous iron promoted ceria catalysts for total and preferential CO oxidation reactions
Autores: Reina, TR; Ivanova, S; Idakiev, V; Tabakova, T; Centeno, MA; Deng, QF; Yuan, ZY; Odriozola, JA
Revista: Journal of Molecular Catalysis A-Chemical, 414 (2016) 62-71
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Herein, a series of highly efficient gold based catalysts supported on mesoporous CeO2-Fe2O3 mixed oxides for CO elimination reactions have been developed. The materials have been fully characterized by means of XRD, Raman and UV-vis spectroscopies among other techniques. We identify the Ce-Fe synergism as a fundamental factor controlling the catalytic performance. Our data clearly reveal that the CO oxidation activity is maximized when the electronic and structural properties of the support are carefully controlled. In this situation, fairly good catalysts for environmental applications as for example H-2 streams purification for fuel cell goals or CO abatement at room temperature can be designed. 

Abril, 2016 | DOI: 10.1016/j.molcata.2016.01.003

Titulo: Comparison of supported TiO2 catalysts in the photocatalytic degradation of NOx
Autores: Rodriguez, MJH; Melian, EP; Diaz, OG; Arana, J; Macias, M; Orive, AG; Rodriguez, JMD
Revista: Journal of Molecular Catalysis A-Chemical, 413 (2016) 56-66
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A comparison is made in this study of the effectiveness of various commercial catalysts in the oxidation of NOx by heterogeneous photocatalysis. The following catalysts were considered: Aeroxide TiO2 P25, Aeroxide TiO2 P90, Hombikat UV-100, Kronos vlp7000, CristalACTIV PC105, CristalACTIV PC500, Kemira 650 and Anatasa Aldrich. All catalysts were deposited by a dip -coating technique onto borosilicate 3.3 glass plates. Optimization of catalyst load showed no significant enhancement of photoactivity, in general, above a deposited mass of 1.16 mg cm(-2). Differences between photocatalyst activity were more apparent at longer illumination times. Photoactivity decreased in the presence of humidity and differences in the adsorbed products were detected. Photocatalyst activity was strongly influenced by specific surface area, with the best results obtained by the catalysts with the largest surface area, namely the PC500, Hombikat and Kronos. Photocatalyst stability was demonstrated in successive reuse cycles. 

Marzo, 2016 | DOI: 10.1016/j.molcata.2015.12.007

Titulo: TiO2-clay based nanoarchitectures for enhanced photocatalytic hydrogen production
Autores: Perez-Carvajal, J; Aranda, P; Obregon, S; Colon, G; Ruiz-Hitzky, E
Revista: Microporous and Mesoporous Materials, 222 (2016) 120-127
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New functional TiO2-clay nanoarchitectures based on layered and fibrous silicates and incorporating Pd and Pt noble metal nanoparticles (NPs) have been synthesized by applying a sol–gel methodology that involves the use of commercial organoclays. The incorporation of the noble metal NPs can be done using two different approaches: i) direct addition to the synthesis medium of a noble metal precursor (typically acetylacetonate) during the generation of the nanoarchitecture, and ii) selective photodeposition of the noble metal NPs in a post-treatment of the TiO2-clay nanoarchitecture. The resulting materials have been characterized by means of XRD, FTIR, Raman, 29Si-NMR, FE-SEM, TEM and N2 adsorption–desorption isotherms. The efficiency of these nanoarchitectures in the photocatalytic hydrogen production has been tested in the photoreforming of methanol. The higher rate in the hydrogen production corresponds to the nanoarchitectures containing Pt and TiO2 NPs derived from sepiolite.

Marzo, 2016 | DOI: 10.1016/j.micromeso.2015.10.007

Titulo: Intensification of hydrogen production by methanol steam reforming
Autores: Sanz, O; Velasco, I; Perez-Miqueo, I; Poyato, R; Odriozola, JA; Montes, M
Revista: International Journal Hydrogen Energy, 41 (2016) 5250-5259
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This paper studies the methanol steam reforming intensification to enhance the hydrogen production in a multi-channel block type micro-reformer. The effects of operating parameters such as reforming temperature, space velocity and catalyst layer thickness on reforming performance are investigated. For optimized design and operating conditions, the 8 cm(3) reformer unit produced 170 LH2/h containing on dry basis 75.0% H-2, 23.5% CO2, 0.06% CH3OH and 1.44% CO at 648 K allowing the production of 218-255 Win a commercial PEMFC with 80% hydrogen utilization. This study shows that high methanol conversion can be achieved with high Pd/ZnO catalyst loading at 648 K with very low CO content (<1.5%) in the outlet stream. 

Marzo, 2016 | DOI: 10.1016/j.ijhydene.2016.01.084

Titulo: In-situ Raman spectroscopy study of Ru/TiO2 catalyst in the selective methanation of CO
Autores: Martinez Tejada, LM; Munoz, A; Centeno, MA; Odriozola, JA
Revista: Journal of Raman Spectroscopy, 47 (2016) 189-197
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Raman spectroscopic technique has been used to characterize a Ru/TiO2 catalyst and to follow in situ their structural changes during the CO selective methanation reaction (S-MET). For a better comprehension of the catalytic mechanism, the in-situ Raman study of the catalysts activation (reduction) process, the isolated CO and CO2 methanation reactions and the effect of the composition of the reactive stream (H2O and CO2 presence) have been carried out. Raman spectroscopy evidences that the catalyst is composed by islands of TiO2-RuO2 solid solutions, constituting Ru-TiO2 interphases in the form of RuxTi1-xO2 rutile type solid solutions. The activation procedure with H-2 at 300 degrees C promotes the reduction of the RuO2-TiO2 islands generating Ru-o-Ti3+ centers. The spectroscopic changes are in agreement with the strong increase in chemical reactivity as increasing the carbonaceous intermediates observed. The selective methanation of CO proceeds after their adsorption on these Ru-o-Ti3+ active centers and subsequent C?O dissociation throughout the formation of CHx/CnHx/CnHxO/CHx?CO species. These intermediates are transformed into CH4 by a combination of hydrogenation reactions. The formation of carbonaceous species during the methanation of CO and CO2 suggests that the CO presence is required to promote the CO2 methanation. Similar carbonaceous species are detected when the selective CO methanation is carried out with water in the stream. However, the activation of the catalysts occurs at much lower temperatures, and the carbon oxidation is favored by the oxidative effect of water.

Febrero, 2016 | DOI: 10.1002/jrs.4774

Titulo: Ru-Ni Catalyst in the Combined Dry-Steam Reforming of Methane: The Importance in the Metal Order Addition
Autores: Alvarez, MA; Centeno, MA; Odriozola, JA
Revista: Topics in Catalysis, 59 (2016) 303-313
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Biogas is one of the main biomass-energy resources. Its use for syngas production with a H-2/CO ratio close to two would have huge environmental, social and economic impact in the actual energetic scenario. However, the use of dry reforming, where the two main components are transformed into syngas, does not allow the desired H-2/CO ratio. For this reason, the addition of water is proposed. The process was performed with two Ru-Ni catalysts where the metal order in the impregnation process was varied. The catalysts were prepared either by simultaneous or consecutive impregnation of the active phases and its catalytic performance in the combined dry-steam reforming of methane was tested. The catalysts were characterized by XRF, XRD, S-BET, TPR-H-2 and Raman spectroscopy. The existence of a strong Ni-Ru interaction is evidenced by Raman spectroscopy and TPR-H-2 in the sample synthesized by the simultaneous impregnation. Concerning the catalytic activity, this sample presents the highest CH4 and CO2 conversion values in the entire composition rate and the lowest amount of carbon deposits after reaction. After pulse, and reactivity tests it was concluded that the higher Ni-Ru interaction displayed by the catalyst synthesized by the simultaneous impregnation, enhances the carbon gasification.

Febrero, 2016 | DOI: 10.1007/s11244-015-0426-5

2015


Titulo: Cu–TiO2 systems for the photocatalytic H2 production: Influence of structural and surface support features
Autores: Obregon, S; Munoz-Batista, MJ; Fernandez-Garcia, M; Kubacka, A; Colon, G
Revista: Applied Catalysis B: Environmental, 179 (2015) 468-478
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The influence of different TiO2 supports on the Cu active species has been studied. It was found that the photocatalytic H2 evolution is highly affected by the structural and electronic features of surface Cu species. Thus, metal dispersion and oxidation state appears strongly conditioned by the structural and surface properties of the TiO2 support. We have examined three TiO2 supports prepared by different synthetic methods; sol–gel, hydrothermal and microemulsion. In addition, we have induced structural and surface modifications by sulfate pretreatment over freshly prepared TiO2 precursors and subsequent calcination. Notably different copper dispersion and oxidation state is obtained by using these different TiO2 supports. From the wide structural and surface analysis of the catalysts we are able to propose that the occurrence of highly disperse Cu2+ species, the sample surface area as well as the crystallinity of the TiO2 support are directly related to the photocatalytic activity for H2 production reaction.

Noviembre, 2015 | DOI: 10.1016/j.apcatb.2015.05.043

Titulo: Study of the phenol photocatalytic degradation over TiO2 modified by sulfation, fluorination, and platinum nanoparticles photodeposition
Autores: Murcia, JJ; Hidalgo, MC; Navio, JA; Arana, J; Dona-Rodriguez, JM
Revista: Applied Catalysis B: Environmental, 179 (2015) 305-312
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In this work, titanium dioxide has been modified by sulfation, fluorination and simultaneous Pt nanoparticles deposition; the influence of these treatments on the photocatalytic activity of this oxide has been studied. A complete characterization study was carried out and it was observed that sulfation, fluorination and metallization were important factors influencing the TiO2 properties. The photocatalytic activity of the materials prepared was evaluated in the phenol degradation and it was found that TiO2fluorination significantly increased the phenol photodegradation rate, compared with bare TiO2, sulfated TiO2 or the commercial TiO2 Degussa P25. It was also found that Pt photodeposition on sulphated TiO2 notably increased the photocatalytic activity of this oxide, while Pt on fluorinated TiO2 did not modify significantly the phenol photodegradation rate.

Noviembre, 2015 | DOI: 10.1016/j.apcatb.2015.05.040

Titulo: Enhancement of stability and photoactivity of TiO2 coatings on annular glass reactors to remove emerging pollutants from waters
Autores: Espino-Estevez, MR; Fernandez-Rodriguez, C; Gonzalez-Diaz, OM; Navio, JA; Fernandez-Hevia, D; Dona-Rodriguez, JM
Revista: Chemical Engineering Journal, 279 (2015) 488-497
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TiO2 coatings of highly photoactive lab-made titania were prepared on the outer wall of the inner tube of a glass tubular reactor by dip-coating method. The effect of decreasing the size of the aggregates to improve adhesion and photoactivity of the coatings to degrade phenol, diclofenac and isoproturon was also investigated. Chemical disaggregation of the TiO2 particles resulted in a lower aggregate size, between 0.1 and 1 μm, than mechanical disaggregation, between 1 and 10 μm. The results of the adhesion tape test showed that either milling of aggregate material with a planetary mill or chemical stabilization of the particles were necessary to obtain TiO2 coatings on glass tube with acceptable quality to be used in water treatment applications. SEM images showed that coatings prepared after milling the TiO2 suspension were more homogeneous without surface aggregates. The degree of adhesion of the coatings after increasing the roughness of the support by abrasive blasting was also evaluated. Adhesion to the substrate was slightly lower when using the modified support. The photoactivity results showed that the coatings prepared after wet milling of catalyst during 30 min and after chemical disaggregation were more efficient in terms of degradation and mineralization when using phenol as model molecule. Subsequent studies with two emerging pollutants, diclofenac and isoproturon, also showed enhanced efficiency of these coatings. The reusability of the TiO2 coatings was also evaluated and a promising photocatalytic performance was observed with a very low variation of the decay rate after five consecutive usages.

Octubre, 2015 | DOI: 10.1016/j.cej.2015.05.038

Titulo: Simultaneous Production of CH4 and H-2 from Photocatalytic Reforming of Glucose Aqueous Solution on Sulfated Pd-TiO2 Catalysts
Autores: Vaiano, V; Iervolino, G; Sarno, G; Sannino, D; Rizzo, L; Mesa, JJM; Hidalgo, MC; Navio, JA
Revista: Oil & Gas Science and Technology-Revue D IFP Energies Nouvelles, 70 (2015) 891-902
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In this work, the simultaneous production of CH4 and H-2 from photocatalytic reforming of glucose aqueous solution on Pd-TiO2 catalysts under UV light irradiation by Light-Emitting Diodes (LED) was investigated. The Pd-TiO2 catalysts were prepared by the photodeposition method. The Pd content was in the range 0.5-2 wt% and a photodeposition time in the range 15-120 min was used. Pd-TiO2 powders were extensively characterized by X-Ray Diffraction (XRD), SBET, X-Ray Fluorescence spectrometry (XRF), UV-Vis Diffuse Reflectance Spectra (UV-Vis DRS), TEM and X-Ray Photoelectron Spectroscopy (XPS). It was found that the lower Pd loading (0.5 wt%) and 120 min of photodeposition time allowed us to obtain homogeneously distributed metal nanoparticles of small size; it was also observed that the increase in the metal loading and deposition time led to increasing the Pd-0 species effectively deposited on the sulfated TiO2 surface. Particle size and the oxidation state of the palladium were the main factors influencing the photocatalytic activity and selectivity. The presence of palladium on the sulfated titania surface enhanced the H-2 and CH4 production. In fact, on the catalyst with 0.5 wt% Pd loading and 120 min of photodeposition time, H-2 production of about 26 lmol was obtained after 3 h of irradiation time, higher than that obtained with titania without Pd (about 8.5 lmol). The same result was obtained for the methane production. The initial pH of the solution strongly affected the selectivity of the system. In more acidic conditions, the production of H-2 was enhanced, while the CH4 formation was higher under alkaline conditions.

Octubre, 2015 | DOI: 10.2516/ogst/2014062

Titulo: Synergy between gold and oxygen vacancies in gold supported on Zr-doped ceria catalysts for the CO oxidation
Autores: Laguna, OH; Perez, A; Centeno, MA; Odriozola, JA
Revista: Applied Catalysis B-Environmental, 176 (2015) 385-395
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The CO oxidation activity of 1 wt.% gold catalysts prepared by deposition-precipitation on a series of ceria doped with Zr supports was studied. The supports (10, 25 and 50 Zr at.%) were synthesized by a pseudo sol-gel method through the thermal decomposition of the corresponding metallic propionates. All the prepared solids were characterized by means of XRF, BET, XRD, Raman spectroscopy, SEM, and H-2-TPR. Solid solution was obtained in all mixed systems, while the segregation of different Ce-Zr oxides was observed for the solid with the 50 Zr at.%. The oxygen vacancies population and the amount of easier reducible Ce4+ species in the solids increase with the Zr content. No major textural or structural modifications were detected after gold deposition, although a strong Au-support interaction was generated. Such interaction is strongly influenced by the nucleation of gold deposits on the oxygen vacancies and consequently the amount of Zr inserted in the ceria network also determines the dispersion of gold. The presence of gold eases the surface reduction at lower temperatures, and as higher the amount of Zr in the gold catalysts, higher the CO conversion at low temperatures, probably due to the enhancement of the electronic transfer at the surface of the catalysts. 

Septiembre, 2015 | DOI: 10.1016/j.apcatb.2015.04.019

Titulo: Oxodiperoxomolybdenum complex immobilized onto ionic liquid modified SBA-15 as an effective catalysis for sulfide oxidation to sulfoxides using hydrogen peroxide
Autores: Carrasco, Carlos J.; Montilla, Francisco; Bobadilla, Luis; Ivanova, Svetlana; Antonio Odriozola, Jose; Galindo, Agustin
Revista: Catalysis Today, 255 (2015) 102-108
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A supported ionic-liquid-phase (SILP) was prepared by the reaction of 1-methyl-3-(3-(triethoxysilyl) propyl)-1H-imidazol-3-ium chloride with a mesoporous SBA-15 silica and then an oxodiperoxomolybdenum complex was immobilized onto the obtained SILP. The resulting material, identified as SBA-15 + ImCl+ MoO5, was characterized by solid state NMR (H-1, C-13 and Si-29), and their textural and thermogravimetric properties were determined. The SBA-15 + ImCl+ MoO5 material was investigated as catalyst for the oxidation of methylphenylsulfide, as model reaction, with aqueous hydrogen peroxide as oxidant at room temperature. The presence of the molybdenum species was crucial for achieving good conversions and methanol was selected as the best solvent (conversion of 95% and selectivity toward sulfoxide 98%). The optimized reaction conditions were applied for the oxidation of several selected sulfides. In general, good catalytic activity and selectivity to sulfoxide were obtained and, remarkably, the selectivity toward sulfoxide is higher than those observed in the study of the same process carried out in [C(4)min][PF6] (C(4)mim = 1-buty1-3-methylimidazolium) and catalyzed by a molecular molybdenum complex, under the same reaction conditions. The importance of the IL-functionalization in the SBA-15 material was evidenced by recycling experiments. The SBA-15 + ImCl+ MoO5 catalyst was used for the sulfoxidation of the methylphenylsulfide substrate for ten reaction cycles without a significant change in conversion, selectivity to sulfoxide and molybdenum content.

Septiembre, 2015 | DOI: 10.1016/j.cattod.2014.10.053

Titulo: Microreactors technology for hydrogen purification: Effect of the catalytic layer thickness on CuOx/CeO2-coated microchannel reactors for the PROX reaction
Autores: Laguna, O. H.; Castano, M. Gonzalez; Centeno, M. A.; Odriozola, J. A.
Revista: Chemical Engineering Journal, 271 (2015) 45-52
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Two blocks of microreactors composed by 100 microchannels and coated, respectively, with 150 and 300 mg of a CuOx/CeO2 catalyst, were prepared and tested in the preferential oxidation of CO in presence of H2 (PROX). The deposition of different amount of catalyst resulted in different catalytic layer thicknesses thus modifying the catalytic performances of the microreactor. The evaluation of the main reaction variables (the space velocity, the O2-to-CO ratio and the presence of H2O and/or CO2 in the stream) was performed over both microreactors and compared to that of the parent powder catalyst. The least loaded microreactor, with a coating thickness around 10 μm, presented the highest CO conversion and selectivity levels at temperatures below 160 °C. This result evidences (i) the improvement of the catalytic performances got by the structuration of the powder catalyst and (ii) the importance of the selection of the adequate thickness of the catalytic layer on the microreactor, which have not to exceed and optimal value. An adequate coating thickness allows minimizing the mass and heat transport limitations, thus resulting in the enhancement of the catalytic performance during the PROX reaction.

Agosto, 2015 | DOI: 10.1016/j.cej.2015.04.023

Titulo: Boosting the activity of a Au/CeO2/Al2O3 catalyst for the WGS reaction
Autores: Reina, T. R.; Ivanova, S.; Centeno, M. A.; Odriozola, J. A.
Revista: Catalysis Today, 253 (2015) 149-154
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Herein a strategy to design highly efficient Au/CeO2/Al2O3 based WGS catalysts is proposed. The inclusion of transition metals, namely Fe, Cu and Zn as CeO2 dopant is considered. All the promoters successfully increased the WGS performance of the undoped sample. The activity improvement can be correlated to structural and/or redox features induced by the dopants. The comparative characterization of the doped samples by means of XRD, Raman spectroscopy and OSC evaluation permits an accurate understanding of the boosted WGS activity arising from the Ce-promoter interaction. This study establishes distinction among both, structural and redox sources of promotion and provides a useful strategy to develop highly active Au/CeO2 based catalysts for the WGS reaction.

Agosto, 2015 | DOI: 10.1016/j.cattod.2015.01.041

Titulo: Boosting the visible-light photoactivity of Bi2WO6 using acidic carbon additives
Autores: Carmona, RJ; Velasco, LF; Hidalgo, MC; Navio, JA; Ania, CO
Revista: Applied Catalysis A-General, 505 (2015) 467-477
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We have explored the role of the physicohemical properties of carbon materials as additives to bismuth tungstate on its structure, optical properties, and photocatalytic activity for the degradation of rhodamine B under visible light. For this purpose, C/Bi2WO6 hybrid composites were prepared following two different routes: (i) physical mixture of the catalyst components, and (ii) one-pot hydrothermal synthesis of the semiconductor in the presence of the carbon additive. Three carbons with different properties were selected as additives: biomass-derived activated carbon, carbon nanotubes and carbon spheres obtained from polysaccharides. Data has shown the outstanding role of the acidic/basic nature of the carbon additive, and of the synthetic method on the photocatalytic performance of the resulting composites. For a given additive, the degradation rate of RhB is greatly improved for the catalysts prepared through a one-step hydrothermal synthesis, where there is low shielding effect of the carbon matrix. Carbon additives of acidic nature boost the surface acidity of the hybrid photocatalyst, thereby enhancing the photodegradation of RhB under visible light via a coupled mechanism (photosensitization, semiconductor photocatalysis and carbon-photon mediated reactions).

Agosto, 2015 | DOI: 10.1016/j.apcata.2015.05.011

Titulo: A comparative study of Bi2WO6, CeO2, and TiO2 as catalysts for selective photo-oxidation of alcohols to carbonyl compounds
Autores: Lopez-Tenllado, FJ; Murcia-Lopez, S; Gomez, DM; Marinas, A; Marinas, JM; Urbano, FJ; Navio, JA; Hidalgo, MC; Gatica, JM
Revista: Applied Catalysis A-General, 505 (2015) 375-381
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Several semiconductors based on ceria or bismuth tungstate were tested for selective oxidation of alcohols to carbonyl compounds in a search for photocatalysts more selective than TiO2. Gas-phase selective photo-oxidation of propan-2-ol to acetone and liquid-phase transformation of 2-buten-1-ol (crotyl alcohol) to 2-butenal (crotonaldehyde) were studied as test reactions. In both processes the highest selectivities were achieved with Bi2WO6-based solids. Further studies on crotyl alcohol transformation evidenced the lower adsorption of the aldehyde on these systems which could minimize the decrease in crotyl alcohol yield observed for TiO2 or CeO2 at high conversions. Incorporation of titania (5% molar) to the Bi2WO6 system increased the reaction rate significantly whereas the aldehyde yield remained high. 

Agosto, 2015 | DOI: 10.1016/j.apcata.2015.08.013

Titulo: Facile Synthesis of Decahedral Particles of Anatase TiO2 with Exposed {001} Facets
Autores: Perales-Martinez, IA; Rodriguez-Gonzalez, V; Obregon-Alfaro, S; Lee, SW
Revista: Journal of Nanoscience and Nanotechnology, 15 (2015) 7351-7356
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This paper reports a facile synthesis of decahedral particles of anatase TiO2 dominated by {101} and {001} faces. The decahedral particles has been enhanced by means a microwave-assisted hydrothermal method using TiF4 as a titanium precursor and HF as capping agent to promote oriented growth and formation of {001} faces in only 4 h. The prepared samples were characterized by scanning electron microscopy, high resolution of transmission electron microscopy and X-ray diffraction. The morphology of anatase TiO2 particles is consisted of near-perfect-truncated-bipyramid-shape. Reaction time is a key factor to obtain truncated-bipyramid-shaped particles with sharp and well-defined edges. Reaction times longer than 4 h induce irregular particles. Decahedral anatase TiO2 particles are truncated bypiramid crystals which have eight {101} and two {001} facets at top/bottom surfaces. The average size of decahedral anatase TiO2 particles are similar to 250 nm for the samples obtained without applying the microwave irradiation and similar to 350 nm for reaction 4 h.

Agosto, 2015 | DOI: 10.1166/jnn.2015.10578

Titulo: On the origin of the photocatalytic activity improvement of BIVO4 through rare earth tridoping
Autores: Obregon, S; Colon, G
Revista: Applied Catalysis A-General, 501 (2015) 56-62
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Rare earth (Tm3+/Er3+,Yb3+,Y3+) tri-doped BiVO4 have been synthesized by means of a surfactant free hydrothermal method having good photoactivities under sun-like excitation for the degradation of methylene blue and O-2 evolution reactions. The improved photocatalytic performance has been attained by multiple approach of the overall photocatalytic mechanism. From the structural and morphological characterization it has been stated that the presence of Y3+ induces the stabilization of the tetragonal phase probably due to its substitutional incorporation in the BiVO4 lattice. Moreover, the extensive doping with rare earth ions such as Yb3+ and Er3+/Tm3+ t-BiVO4 evidenced that important structural, electronic changes as well as the luminescence properties were also exalted. Ternary doping clearly prompts the higher photocatalytic activities. A more packed tetragonal structure in conjunction leading to improved charge carriers mobility, with the observed visible and NIR photoactivities of t-BiVO4 could be the responsible of the improved photocatalytic activity under solar-like irradiation.

Junio, 2015 | DOI: 10.1016/j.apcata.2015.04.032

Titulo: Photocatalytic propylene epoxidation on Bi2WO6-based photocatalysts
Autores: Murcia-Lopez, S.; Vaiano, V.; Sannino, D.; Hidalgo, M. C.; Navio, J. A.
Revista: Research on Chemical Intermediates, 41 (2015) 4199-4212
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The photocatalytic epoxidation of propylene (PR) with molecular oxygen was carried out in a fluidized-bed reactor with several Bi2WO6-based materials under UV-A illumination. Three different photocatalysts were tested: one of single Bi2WO6 and two of coupled Bi2WO6-TiO2 heterostructures, thus showing that a mixed system of Bi2WO6 with commercial TiO2 Degussa-P25 leads to the best combination of conversion and PO selectivity. Then, direct support on glass spheres and silica gel was made, being a good alternative for improving the Bi2WO6 performance. Additionally, several reaction conditions of temperature and PR to O-2 feed ratio were studied.

Junio, 2015 | DOI: 10.1007/s11164-013-1523-3

Titulo: H-2 oxidation as criterion for PrOx catalyst selection: Examples based on Au-Co-O-x-supported systems
Autores: Reina, TR; Megias-Sayago, C; Florez, AP; Ivanova, S; Centeno, MA; Odriozola, JA
Revista: Journal of Catalysis, 326 (2015) 161-171
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A new approach for understanding PrOx reaction over gold catalysts is proposed in this work. The competition between H-2 and CO oxidation has been studied over a series of Au/MOx/Al2O3 (M = Ce and Co) catalysts in simulated post-reforming gas stream, containing H2O and CO2 for H-2 cleanup goals. The catalysts' behavior is correlated to their oxygen storage capacity, redox behavior, and oxidation ability. The estimation of the reaction rates reveals that in these solids the H-2 combustion, the selectivity limiting factor in the PrOx process, is mainly controlled by the support and not by the gold presence. The possible use of the hydrogen oxidation reaction as a catalyst selection criterion is discussed. 

Mayo, 2015 | DOI: 10.1016/j.jcat.2015.03.015

Titulo: A novel two-steps solvothermal synthesis of nanosized BiPO4 with enhanced photocatalytic activity
Autores: Zhang, YF; Sillanpaa, M; Obregon, S; Colon, G
Revista: Journal of Molecular Catalysis A-Chemical, 402 (2015) 92-99
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Nano-sized BiPO4 has been successfully synthesized via a novel designed two-steps solvothermal route using ethylene glycol as solvent. Comparing with traditional hydrothermal method, the novel approach could readily prepare BiPO4 with shorter time. The photocatalytic activity of prepared BiPO4 has been tested via degradation of methylene blue (MB) under light irradiation. The experimental results show that the BiPO4 prepared by novel route had enhanced photocatalytic activity and the synthetic parameters also impact the reaction rate meaningfully. Finally, the obtained samples have been widely characterized by means of powder X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET) surface area, scanning electron microscopy (SEM), UV–vis diffuse reflectance spectra (DRS) and Fourier transformed infrared (FTIR) spectra. BiPO4 prepared by this novel approach have a particles size below 100 nm, which is a big improvement by comparing with previous works (few micrometer). The effect of EG during the formation of BiPO4 has been discussed and a possible formation mechanism is proposed.
 

Mayo, 2015 | DOI: 10.1016/j.molcata.2015.03.011

Titulo: Theory and Practice: Bulk Synthesis of C3B and its H2- and Li-Storage Capacity
Autores: King, TC; Matthews, PD; Glass, H; Cormack, JA; Holgado, JP; Leskes, M; Griffin, JM; Scherman, OA; Barker, PD; Grey, CP; Dutton, SE; Lambert, RM; Tustin, G; Alavi, A; Wright, DS
Revista: Angewandte Chemie International Edition, 54 (2015) 5919-5923
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Previous theoretical studies of C3B have suggested that boron-doped graphite is a promising H2- and Li-storage material, with large maximum capacities. These characteristics could lead to exciting applications as a lightweight H2-storage material for automotive engines and as an anode in a new generation of batteries. However, for these applications to be realized a synthetic route to bulk C3B must be developed. Here we show the thermolysis of a single-source precursor (1,3-(BBr2)2C6H4) to produce graphitic C3B, thus allowing the characteristics of this elusive material to be tested for the first time. C3B was found to be compositionally uniform but turbostratically disordered. Contrary to theoretical expectations, the H2- and Li-storage capacities are lower than anticipated, results that can partially be explained by the disordered nature of the material. This work suggests that to model the properties of graphitic materials more realistically, the possibility of disorder must be considered.

Abril, 2015 | DOI: 10.1002/anie.201412200

Titulo: Mono and bimetallic Cu-Ni structured catalysts for the water gas shift reaction
Autores: O. Arbeláez, T.R. Reina, S. Ivanova, F. Bustamante, A.L. Villa, M.A. Centeno, J.A. Odriozola
Revista: Applied Catalysis A-General, 497 (2015) 1-9
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The water-gas shift (WGS) reaction over structured Cu, Ni, and bimetallic Cu-Ni supported on active carbon (AC) catalysts was investigated. The structured catalysts were prepared in pellets form and applied in the medium range WGS reaction. A good activity in the 180–350 °C temperature range was registered being the bimetallic Cu-Ni:2-1/AC catalyst the best catalyst. The presence of Cu mitigates the methanation activity of Ni favoring the shift process. In addition the active carbon gasification reaction was not observed for the Cu-containing catalyst converting the active carbon in a very convenient support for the WGS reaction. The stability of the bimetallic Cu-Ni:2-1/AC catalyst under continuous operation conditions, as well as its tolerance towards start/stop cycles was also evaluated.

Abril, 2015 | DOI: 10.1016/j.apcata.2015.02.041

Titulo: The role of silver nanoparticles functionalized on TiO2 for photocatalytic disinfection of harmful algae
Autores: Lee, Soo-Wohn; Obregon, S.; Rodriguez-Gonzalez, V.
Revista: RSC Advances, 5 (2015) 44470-44475
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Silver loaded TiO2 samples were prepared by photodeposition of different amounts of Ag+ ions over commercial titanium dioxide (Evonik TiO2 P25) in aqueous media without the presence of sacrificial agents. The obtained photocatalysts were characterized by several techniques such as X-ray powder diffraction (XRD), UV-vis diffuse reflectance spectroscopy (DRS), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) in order to correlate the effect of the silver amount on the photocatalytic properties of the final nanocomposite. The effect of the silver nanoparticles on the photocatalytic behaviour of TiO2 was evaluated by means of the photodegradation of methyl orange dye and the inactivation of noxious algae Tetraselmis suecicaand Amphidium carterae under continuous exposure of low power irradiation UV-light. The sample with 1.5% wt of silver nanoparticles showed the highest photocatalytic elimination of the azo dye and both algae types. According to the results, the cells were deformed during the photocatalytic process by the attack of highly reactive species such as hydroxyl radicals, H2O2 and superoxide ions generated on the TiO2 surface. The algae cells were not regenerated by themselves after the photocatalytic process due the high degree of fragmentation that they suffered during the light irradiation.

Abril, 2015 | DOI: 10.1039/C5RA08313C

Titulo: Photocatalytic reduction of CO2 over platinised Bi2WO6-based materials
Autores: Murcia-Lopez, S; Vaiano, V; Hidalgo, MC; Navio, JA; Sannino, D
Revista: Photochemical & Photobiological Sciences, 14 (2015) 678-685
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The photocatalytic reduction of CO2 with H2O to produce CH4 in the gas phase was carried out in the presence of two Bi2WO6-based materials. For this purpose, single Bi2WO6 and a coupled Bi2WO6-TiO2 system were synthesised and metallised with Pt, through a Pt photodeposition method. Then, the samples were characterised and the photocatalytic activity was evaluated in a continuous fluidised-bed reactor irradiated with UV light. Single Bi2WO6 presents an interesting behaviour under H2O rich conditions. In particular, the metallisation improves the material's performance for CH4 formation, while the TiO2 addition to Bi2WO6 increases the CH4 yield only at low H2O/CO2 ratio. The Bi2WO6-TiO2 system metallised with a Pt photocatalyst displayed the highest CH4 yield among all the prepared photocatalysts. The stability of the system can be enhanced through the addition of a blue phosphor to the reactant mixture, especially under H2O rich conditions.

Marzo, 2015 | DOI: 10.1039/c4pp00407h

Titulo: Role of ruthenium on the catalytic properties of CeZr and CeZrCo mixed oxides for glycerol steam reforming reaction toward H2 production
Autores: Martinez, LM; Araque, M; Centeno, MA; Roger, AC
Revista: Catalysis Today, 242 (2015) 80-90
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The effect of ruthenium on the physico-chemical properties of CeZr and CeZrCo mixed oxides for H2production by glycerol steam reforming reaction has been studied. The combination of in situ Raman spectroscopy under both reductive and oxidative conditions, H2/O2 pulses and XRD, Raman, BET analysis, H2-TPR and TPD-TPO analyses contributed to the determination of the structural and textural properties, redox behavior, re-oxidation capacity and resistance to carbon deposition of the synthesized catalysts. The results show that the catalytic activity is improved by the (positive) cooperative and complementary effect between cobalt and ruthenium that favors the selectivity toward the steam reforming, selective to H2, with respect to the unselective thermal decomposition of glycerol. Ruthenium stabilizes the cobalt cations inserted in the fluorite structure preventing its rejection as Co3O4; and provides the necessary hydrogen to reduce Ce4+. The combination cobalt–ruthenium modifies positively the redoxproperties of the catalysts, increases the re-oxidation capacity (OSC) and promotes the gasification of the carbon deposits. Under the reaction conditions, the decrease in glycerol conversion came along with a change of selectivity. The formation of H2 and CO2 were strongly decreased, while the formation of CO, C2H4 and condensable products (mainly hydroxyacetone) increase. The differences in the catalytic stability and activity of the catalysts are related to the capability of the catalysts to activate H2O under the reaction conditions, favoring the steam reforming reaction over the thermal decomposition.

Febrero, 2015 | DOI: 10.1016/j.cattod.2014.07.034

Titulo: Ni-CeO2/C Catalysts with Enhanced OSC for the WGS Reaction
Autores: Pastor-Perez, L; Ramirez Reina, T; Ivanova, S; Centeno, MA; Odriozola, JA; Sepulveda-Escribano, A
Revista: Catalysts, 5 (2015) 298-309
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In this work, the WGS performance of a conventional Ni/CeO2 bulk catalyst is compared to that of a carbon-supported Ni-CeO2 catalyst. The carbon-supported sample resulted to be much more active than the bulk one. The higher activity of the Ni-CeO2/C catalyst is associated to its oxygen storage capacity, a parameter that strongly influences the WGS behavior. The stability of the carbon-supported catalyst under realistic operation conditions is also a subject of this paper. In summary, our study represents an approach towards a new generation of Ni-ceria based catalyst for the pure hydrogen production via WGS. The dispersion of ceria nanoparticles on an activated carbon support drives to improved catalytic skills with a considerable reduction of the amount of ceria in the catalyst formulation.

Febrero, 2015 | DOI: 10.3390/catal5010298

Titulo: Ionic liquid immobilization on carbon nanofibers and zeolites: Catalyst design for the liquid-phase toluene chlorination
Autores: Losch, Pit; Martinez Pascual, Antonio; Boltz, Marilyne; Ivanova, Svetlana; Louis, Benoit; Montilla, Francisco; Antonio Odriozola, Jose
Revista: Comptes Rendus Chimie, 18 (2015) 324-329
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The environmental-friendly chlorination reaction of toluene by trichloroisocyanuric acid (TCCA, C3N3O3Cl3) was investigated applying immobilized ionic liquids (ILs) on different supports. Ionic liquids were grafted either on carbon nanofibers (CNF) or encapsulated in zeolites. Their influence on the chlorination activity as well as on the selectivity in different chlorinated products was studied. An unusually high selectivity toward meta-chlorotoluene was achieved, up to 36%. Hence, the selectivity could be tuned to produce either expected ortho-/para-chlorotoluene or meta-chlorotoluene with a proper support choice. 

Febrero, 2015 | DOI: 10.1016/j.crci.2014.06.006

Titulo: Evolution of H-2 photoproduction with Cu content on CuOx-TiO2 composite catalysts prepared by a microemulsion method
Autores: Kubacka, A; Munoz-Batista, MJ; Fernandez-Garcia, M; Obregon, S; Colon, G
Revista: Applied Catalysis B: Environmental, 163 (2015) 214-222
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Copper oxides in contact with anatase correspond to promising materials with high activity in the photo-production of hydrogen by aqueous reforming of alcohols. By a single pot microemulsion method we obtained a series of Cu-Ti composite systems with controlled copper content in the 0-25 wt.% range. The scanning of such a wide range of composition led to the discovery of two well differentiated maxima in the photo-reaction performance. These maxima present rather high and relatively similar reaction rates and photonic efficiencies but are ascribed to the presence of different copper species. A multi-technique analysis of the materials indicates that the maxima obtained comes from optimizing different steps of the reaction; while the first would be connected with a positive effect on anatase charge handling performance the second seems exclusively related to electron capture by surface copper species.

Enero, 2015 | DOI: 10.1016/j.apcatb.2014.08.005

Titulo: Synthesis and application of layered titanates in the photocatalytic degradation of phenol
Autores: Ivanova, S; Penkova, A; Hidalgo, MD; Navio, JA; Romero-Sarria, F; Centeno, MA; Odriozola, JA
Revista: Applied Catalysis B: Environmental, 163 (2015) 23-29
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This study proposes a direct synthetic route to single titanate sheets through the mild and versatile conditions of the “chimie douce”. The stages of the production include the complexation of the titanium alkoxide precursor by benzoic acid, the formation of titanium oxo-clusters and their controlled transformation into single sheet titanates during the hydrolysis stage. The resulted material appears to be an excellent precursor for self-organized TiO2 nanotubes formation which presents an excellent activity as photocatalyst in the photo-degradation of phenol.

Enero, 2015 | DOI: 10.1016/j.apcatb.2014.07.048

Titulo: Water splitting performance of Er3+-doped YVO4 prepared from a layered K3V5O14 precursor
Autores: Obregon, S; Colon, G
Revista: Chemical Engineering Journal, 262 (2015) 29-33
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Erbium-doped YVO4 have been synthesized by means of a simple solution method having good photo activities under UV-like excitation for the water splitting half reactions. From the structural and morphological characterization it has been stated that the presence of Er3+ induces the promotion of luminescence. Moreover the incorporation of erbium clearly affects to the morphology YVO4 leading to 200 nm size well-defined spindle-like particles. The improved photocatalytic performance might be associated to a better electron–hole separation mechanism, probably due to the slight increase of band-gap value. The obtained photoactivities for H2 and O2 evolution reactions make this material a promising candidate for water splitting reactions.

Enero, 2015 | DOI: 10.1016/j.cej.2014.09.073

Titulo: Photocatalytic activity of bismuth vanadates under UV-A and visible light irradiation: Inactivation of Escherichia coli vs oxidation of methanol
Autores: Adan, C; Marugan, J; Obregon, S; Colon, G
Revista: Catalysis Today, 240 (2015) 93-99
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Four bismuth vanadates have been synthesized by using two different precipitating agents (NH3 and triethylamine) following a hydrothermal treatment at 100 °C for 2 h and at 140 °C for 20 h. Then, solids were characterized by X-ray diffraction, BET surface area, UV–vis spectroscopy and scanning microscopy techniques. The characterization of the synthesized materials showed a well crystallized scheelite monoclinic structure with different morphologies. All materials display optimum light absorption properties for visible light photocatalytic applications. The photocatalytic activity of the catalysts was investigated for the inactivation of Escherichia coli bacteria and the oxidation of methanol under UV–vis and visible light irradiation sources. Main results demonstrate that BiVO4 are photocatalytically active in the oxidation of methanol and are able to inactivate bacteria below the detection level. The activity of the catalyst decreases when using visible light, especially for methanol oxidation, pointing out differences in the reaction mechanism. In contrast with bacteria, whose interaction with the catalyst is limited to the external surface, methanol molecules can access the whole material surface.

Enero, 2015 | DOI: 10.1016/j.cattod.2014.03.059

Titulo: Glycerol steam reforming on bimetallic NiSn/CeO2-MgO-Al2O3 catalysts: Influence of the support, reaction parameters and deactivation/regeneration processes
Autores: Bobadilla, LP; Penkova, A; Alvarez, A; Dominguez, MI; Romero-Sarria, F; Centeno, MA; Odriozola, JA
Revista: Applied Catalysis A: General, 492 (2015) 38-47
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NiSn bimetallic catalysts supported over Al2O3 modified with different promoter (Mg and/or Ce) were prepared and characterized by powder X-ray diffraction (XRD), N2 sorptometry, and temperature programmed reduction (TPR). Hydrogen production by glycerol steam reforming over these catalysts was investigated. Among the catalysts, NiSn/AlMgCe catalyst shows the highest hydrogen yield as well as the best stability during the reaction. The effect of reaction temperature, water/glycerol molar ratio and space velocity on the glycerol steam reforming over NiSn/AlMgCe were also investigated. Finally, it was verified that the catalyst can be regenerated by oxidation of carbonaceous deposits.

Enero, 2015 | DOI: 10.1016/j.apcata.2014.12.029

Titulo: Effective photoreduction of a nitroaromatic environmental endocrine disruptor by AgNPs functionalized on nanocrystalline TiO2
Autores: Hernandez-Gordillo, A; Obregon, S; Paraguay-Delgadod, F; Rodriguez-Gonzalez, V
Revista: RSC Advances, 5 (2015) 15194-15197
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Unprecedented photoactivity of silver nanoparticles photodeposited on nanocrystalline TiO2 for the efficient reduction of 4-nitrophenol at room temperature is reported. The use of Na2SO3 as a harmless scavenger agent for the reduction of a nitroaromatic endocrine disruptor yields a valuable 4-aminophenol reagent.

Enero, 2015 | DOI: 10.1039/c5ra00094g

Titulo: Structural and chemical reactivity modifications of a cobalt perovskite induced by Sr-substitution. An in situ XAS study
Autores: Hueso, JL; Holgado, JP; Pereniguez, R; Gonzalez-DelaCruz, VM; Caballero, A
Revista: Materials Chemistry and Physics, 151 (2015) 29-33
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LaCoO3 and La0.5Sr0.5O3O3-delta perovskites have been studied by in situ Co K-edge XAS. Although the partial substitution of La(III) by Sr(II) species induces an important increase in the catalytic oxidation activity and modifies the electronic state of the perovskite, no changes could be detected in the oxidation state of cobalt atoms. So, maintaining the electroneutrality of the perovskite requires the generation of oxygen vacancies in the network. The presence of these vacancies explains that the substituted perovskite is now much more reducible than the original LaCoO3 perovskite. As detected by in situ XAS, after a consecutive reduction and oxidation treatment, the original crystalline structure of the LaCoO3 perovskite is maintained, although in a more disordered state, which is not the case for the Sr doped perovskite. So, the La0.5Sr0.5CoO3-delta perovskite submitted to the same hydrogen reduction treatment produces metallic cobalt, while as determined by in situ XAS spectroscopy the subsequent oxidation treatment yields a Co(III) oxide phase with spinel structure. Surprisingly, no Co(II) species are detected in this new spinel phase. 

Enero, 2015 | DOI: 10.1016/j.matchemphys.2014.11.015

Titulo: Sonogashira Cross-Coupling and Homocoupling on a Silver Surface: Chlorobenzene and Phenylacetylene on Ag(100)
Autores: Sanchez-Sanchez, C; Orozco, N; Holgado, JP; Beaumont, SK; Kyriakou, G; Watson, DJ; Gonzalez-Elipe, AR; Feria, L; Sanz, JF; Lambert, RM
Revista: Journal of the American Chemical Society, 137 (2015) 940-947
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Scanning tunneling microscopy, temperature-programmed reaction, near-edge X-ray absorption fine structure spectroscopy, and density functional theory calculations were used to study the adsorption and reactions of phenylacetylene and chlorobenzene on Ag(100). In the absence of solvent molecules and additives, these molecules underwent homocoupling and Sonogashira cross-coupling in an unambiguously heterogeneous mode. Of particular interest is the use of silver, previously unexplored, and chlorobenzene—normally regarded as relatively inert in such reactions. Both molecules adopt an essentially flat-lying conformation for which the observed and calculated adsorption energies are in reasonable agreement. Their magnitudes indicate that in both cases adsorption is predominantly due to dispersion forces for which interaction nevertheless leads to chemical activation and reaction. Both adsorbates exhibited pronounced island formation, thought to limit chemical activity under the conditions used and posited to occur at island boundaries, as was indeed observed in the case of phenylacetylene. The implications of these findings for the development of practical catalytic systems are considered.

Diciembre, 2014 | DOI: 10.1021/ja5115584

Titulo: Catalytic screening of Au/CeO2-MOx/Al2O3 catalysts (M = La, Ni, Cu, Fe, Cr, Y) in the CO-PrOx reaction
Autores: Reina, TR; Ivanova, S; Centeno, MA; Odriozola, JA
Revista: International Journal of Hydrogen Energy, 40 (2015) 1782-1788
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In this work, a series of Au/CeO2-MOx/Al2O3 catalysts has been prepared and evaluated in the PrOx reaction. Within the series of dopants Fe and Cu containing samples enhanced the catalytic performance of the parent Au/CeO2/Al2O3 catalyst being copper the most efficient promoter. For both samples an enhanced oxygen storage capacity (OSC) is registered and accounts for the high CO oxidation activity. More particularly, the Au/CeO2-CuOx/Al2O3 catalyst successfully withstands the inclusion of water in the PrOx stream and presents good results in terms of CO elimination. However to achieve a good selectivity toward, CO2 formation properly adjusting of the reaction parameters, such as oxygen concentration and space velocity is needed. Within the whole screened series the Cu-containing catalyst can be considered as the most interesting alternative for H-2 clean-up applications.

Diciembre, 2014 | DOI: 10.1016/j.ijhydene.2014.11.141

2014


Titulo: Heterogeneous selective oxidation of fatty alcohols: Oxidation of 1-tetradecanol as a model substrate
Autores: Corberan, VC; Gomez-Aviles, A; Martinez-Gonzalez, S; Ivanova, S; Dominguez, MI; Gonzalez-Perez, ME
Revista: Catalysis Today, 238 (2014) 49-53
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Selective oxidation of fatty alcohols, i.e., linear long-chain alkanols, has been scarcely investigated to date, despite its potential application in high value chemical's production. We report for the first time the liquid phase heterogeneous oxidation of 1-tetradecanol, used as a model molecule for fatty alcohols, according to green chemistry principles by using a Au/CeO2-Al2O3 catalyst and O-2 as oxidant at normal pressure. High selectivity to tetradecanal (ca. 80%) or to tetradecanoic acid (60-70%) are reached at medium conversion (up to 38%), depending on the reaction conditions used. Comparison with similar tests of 1-octanol oxidation shows that the increase of the carbon chain length decreases the alcohol conversion and the formation of ester, probably due to a greater steric effect.

Noviembre, 2014 | DOI: 10.1016/j.cattod.2014.03.033

Titulo: Active Site Considerations on the Photocatalytic H-2 Evolution Performance of Cu-Doped TiO2 Obtained by Different Doping Methods
Autores: Valero, JM; Obregon, S; Colon, G
Revista: ACS Catalysis, 4 (2014) 3320-3329
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A photocatalytic H2 evolution reaction was performed over copper doped TiO2. The influence of sulfate pretreatment over fresh TiO2 support and the Cu doping method has been evaluated. Wide structural and surface characterization of catalysts was carried out in order to establish a correlation between the effect of sulfuric acid treatment and the further Cu-TiO2photocatalytic properties. Notably a different copper dispersion and oxidation state is obtained by different metal decoration methods. From the structural and surface analysis of the catalysts we have stated that the occurrence of highly disperse and reducible Cu2+ species is directly related to the photocatalytic activity for the H2 production reaction. Highly active materials have been obtained from a chemical reduction method leading to 18 mmol·h–1·g–1for 3 mol % copper loading.

Septiembre, 2014 | DOI: 10.1021/cs500865y

Titulo: Heterostructured Er3+ doped BiVO4 with exceptional photocatalytic performance by cooperative electronic and luminescence sensitization mechanism
Autores: Obregon, S; Colon, G
Revista: Applied Catalysis B: Environmental, 158-159 (2014) 242-249
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Er-BiVO4 has been synthesized by means of mw-assisted hydrothermal method having good photoactivity under sun-like excitation. It is stated that the precursor addition sequence plays a critical role which determine the further structural feature of BiVO4. From the structural and morphological characterization, it can be demonstrated that the presence of Er3+ would induce the stabilization of the tetragonal phase probably due to the formation of tetragonal-ErVO4 seeds previous to BiVO4 formation. The best photocatalytic performance is attained for the sample with 0.75 at% Er3+ content. At this dopant loading a mixture of tetragonal and monoclinic phase (70% tetragonal) is obtained. The dramatic increase in the photocatalytic activity for 0.75 at% Er-BiVO4 is related to the occurrence of such heterostructure. For this system, the MB degradation rate constant appears drastically higher as bare m-BiVO4. Furthermore, activities of photocatalysts for visible-light-driven O2 evolution have been evaluated, demonstrating that the photocatalytic activity of this Er-doped system (O2 evolution rate, 1014 μmol g−1 h−1) is 20 times as that of undoped m-BiVO4 (O2 evolution rate, 54 μmol g−1 h−1). From the obtained results, the cooperative conjunction of electronic and luminescence mechanism involved in the reaction is proposed to be the origin of the enhanced photocatalytic efficiencies of such systems.

Septiembre, 2014 | DOI: 10.1016/j.apcatb.2014.04.029

Titulo: Pyridine adsorption on NiSn/MgO-Al2O3: An FTIR spectroscopic study of surface acidity
Autores: Penkova, A; Bobadilla, LF; Romero-Sarria, F; Centeno, MA; Odriozola, JA
Revista: Applied Surface Science, 317 (2014) 241-251
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The acid-base properties of MgO-Al2O3 supports and NiSn/MgO-Al2O3 catalysts were evaluated by IR spectroscopy using pyridine as a probe molecule. The results indicate that only Lewis acid sites were detected on the surface of the supports as well as on the catalysts. Nevertheless, Bronsted acid sites were not detected. In the support without MgO three kinds of coordinatively unsaturated acid sites were detected: Al3+ cations occupying octahedral, tetrahedral and tetrahedral with cationic vacancy in the neighbourhood. The last sites appear as the strongest. Moreover, they are able to activate the pyridine molecules leading to the formation of an intermediate ce-pyridone complex. When MgO or NiO were added to the alumina, the number and strength of the Lewis acid sites decreased and significant changes were observed in the tetrahedral sites with adjoining cation vacancies. The incorporation of the Mg2+ cations into the alumina's structure takes place on the vacant tetrahedral positions, forming spinel MgAl2O4. As a result, the fraction of tetrahedral sites with adjoining cationic vacancy diminished and the intermediate ce-pyridone complex in the support with the highest MgO loading was hardly detected. The addition of Ni2+ cations leads to the filling of the free octahedral positions, resulting in the formation of a NiAl2O4 spinel structure and the thermal stability of the ce-pyridone species decreases. In the catalysts, the progressive reduction of the number and strength of the Lewis acid sites is due to a competitive formation of the two types of MgAl2O4 and NiAl2O4 spinels. In the catalyst NiSn/30MgO-Al2O3 no cationic vacancies were detected and the surface reaction with ce-pyridone formation did not occur. 

Septiembre, 2014 | DOI: 10.1016/j.apsusc.2014.08.093

Titulo: Improved O-2 evolution from a water splitting reaction over Er3+ and Y3+ co-doped tetragonal BiVO4
Autores: Obregon, S; Colon, G
Revista: Catalysis Science & Technology, 4 (2014) 2042-2050
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Erbium–yttrium co-doped BiVO4 with a tetragonal structure is synthesized by means of a surfactant free hydrothermal method. The studied photocatalyst shows good photoactivity under sun-like excitation for the degradation of methylene blue (MB) and for O2 evolution. From structural and morphological characterization, it has been stated that the presence of lanthanides induces the stabilization of the tetragonal phase. This is probably due to the substitutional occupation that occurs in the BiVO4 lattice. The photocatalytic performance under visible-NIR radiation clearly evidences the occurrence of an up-conversion process involved in the overall photo-electronic mechanism. The tetragonal phase Er0.0075,Y0.03–Bi0.9625VO4 system gives the highest O2 evolution rate (425 μmol g−1 h−1) under sun-like excitation, being 8 times higher than that attained for m-BiVO4 (53 μmol g−1 h−1).

Junio, 2014 | DOI: 10.1039/C4CY00050A

Titulo: Bifunctional, Monodisperse BiPO4-Based Nanostars: Photocatalytic Activity and Luminescent Applications
Autores: Becerro, AI; Criado, J; Gontard, LC; Obregon, S; Fernandez, A; Colon, G; Ocana, M
Revista: Crystal Growth & Design, 14 (2014) 3319-3326
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Monodisperse, monoclinic BiPO4 nanostars have been synthesized by a homogeneous precipitation reaction at 120 °C through controlled release of Bi3+ cations from a Bi–citrate chelate, in a mixture of glycerol and ethylene glycol, using H3PO4 as the phosphate source. The set of experimental conditions necessary to obtain uniform nanoparticles is very restrictive, as the change in either the polyol ratio or the reactant concentrations led to ill-defined and/or aggregated particles. The morphology of the particles consists of a starlike, hierarchical structure formed by the ordered arrangement of nanorod bundles. Transmission electron tomography has revealed that the nanostars are not spherical but flattened particles. Likewise, Fourier transform infrared spectroscopy and thermogravimetry have shown that the synthesized nanostars are functionalized with citrate groups. The mechanism of formation of the nanostars has been analyzed to explain their morphological features. The as-synthesized BiPO4 nanostars exhibit an efficient photocatalytic performance for the degradation of Rhodamine B. Finally, it has been demonstrated that the stars can be Eu3+-doped up to 2 mol % without any change in the particle morphology or symmetry, and the doped samples show emission in the orange-red region of the visible spectrum after ultraviolet excitation. These experimental observations make this material a suitable phosphor for biotechnological applications.

Junio, 2014 | DOI: 10.1021/cg500208h

Titulo: Excellent photocatalytic activity of Yb3+, Er3+ co-doped BiVO4 photocatalyst
Autores: Obregon, S.; Colon, G.
Revista: Applied Catalysis B: Environmental, 152-153 (2014) 328-334
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Ytterbium-Erbium co-doped BiVO4 have been synthesized by means of a surfactant free hydrothermal method having good photoactivities under sun-like excitation for the degradation of Methylene Blue and O2 evolution reactions. From the structural and morphological characterization it has been stated that the presence of Yb3+ and Er3+ induces the stabilization of the tetragonal phase probably due to its substitutional incorporation in the BiVO4 lattice. The occurrence of the Yb3+,Er3+ co-doped monoclinic-tetragonal BiVO4 heterostructure induces the higher photocatalytic activities. The best photocatalytic performance was attained for the sample with 1:4 Er3+:Yb3+ ratio. The observed NIR photoactivity clearly denotes the occurrence of an up-conversion mechanism involved in the overall photocatalytic process.

Mayo, 2014 | DOI: 10.1016/j.apcatb.2014.01.054

Titulo: A study of the optical properties of metal-doped polyoxotitanium cages and the relationship to metal-doped titania
Autores: Lv, YK; Cheng, J; Matthews, PD; Holgado, JP; Willkomm, J; Leskes, M; Steiner, A; Fenske, D; King, TC; Wood, PT; Gan, LH; Lambert, RM; Wright, DS
Revista: Dalton Transactions, 43 (2014) 8679-8689
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To what extent the presence of transition metal ions can affect the optical properties of structurally well-defined, metal-doped polyoxotitanium (POT) cages is a key question in respect to how closely these species model technologically important metal-doped TiO2. This also has direct implications to the potential applications of these organically-soluble inorganic cages as photocatalytic redox systems in chemical transformations. Measurement of the band gaps of the series of closely related polyoxotitanium cages [MnTi14(OEt)28O14(OH)2] (1), [FeTi14(OEt)28O14(OH)2] (2) and [GaTi14(OEt)28O15(OH)] (3), containing interstitial Mn(II), Fe(II) and Ga(III) dopant ions, shows that transition metal doping alone does not lower the band gaps below that of TiO2 or the corresponding metal-doped TiO2. Instead, the band gaps of these cages are within the range of values found previously for transition metal-doped TiO2 nanoparticles. The low band gaps previously reported for 1 and for a recently reported related Mn-doped POT cage appear to be the result of low band gap impurities (most likely amorphous Mn-doped TiO2).

Mayo, 2014 | DOI: 10.1039/C4DT00555D

Titulo: Phase assembly and electrical conductivity of spark plasma sintered CeO2-ZrO2 ceramics
Autores: Poyato, R; Cruz, SA; Cumbrera, FL; Moreno, B; Chinarro, E; Odriozola, JA
Revista: Journal of Materials Science, 49 (2014) 6353-6362
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Cex Zr1−x O2 (x = 0.10, 0.16 and 0.33) nanocrystalline powders were obtained by a two-step synthesis technique and sintered by spark plasma sintering (SPS). As consequence of the reduction of Ce4+ to Ce3+ species by carbon in the graphite environment in SPS, phase assemblies including tetragonal, monoclinic and pyrochlore phases were generated in the ceramics during the sintering process. The electrical conductivity was highly dependent on phase assembly and atmosphere (N2, H2 and O2). A significant decrease in the activation energy was noticed in the ceramics with high pyrochlore content when measuring the conductivity in H2 atmosphere, consequence of the strong reduction promoted in these ceramics during the measurement. Equal conduction behavior with similar activation energy was observed in all the ceramics when measuring in O2 atmosphere.

Mayo, 2014 | DOI: 10.1007/s10853-014-8361-6

Titulo: Correlation study between photo-degradation and surface adsorption properties of phenol and methyl orange on TiO2 Vs platinum-supported TiO2
Autores: Murcia, JJ; Hidalgo, MC; Navio, JA; Arana, J; Dona-Rodriguez, JM
Revista: Applied Catalysis B: Environmental, 150-151 (2014) 107-115
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Adsorption of phenol and methyl orange on the surface of TiO2 and Pt–TiO2 photocatalysts was investigated by FT-IR spectroscopy. It was found that platinum plays an important role in the adsorption properties of the studied substrates on TiO2. Platinum deposits modified the phenol-photocatalyst interaction providing new adsorption sites on TiO2 surface. On Pt–TiO2 photocatalysts, phenol mainly interacts via formation of adsorbed phenolates species. It was also found that the adsorption of methyl orange on titania and Pt–TiO2 photocatalysts occurs via interaction of the azo group with surface Ti4+. Pt photodeposition significantly increases the TiO2 photoreactivity in phenol and methyl orange photo-degradation; however, this increase depends on the properties of the Pt deposits. Moreover, it was observed that platinum content is the main factor determining the substrate-photocatalyst interaction and therefore the Pt–TiO2 photocatalytic performance.

Abril, 2014 | DOI: 10.1016/j.apcatb.2013.12.010

Titulo: In situ XAS study of an improved natural phosphate catalyst for hydrogen production by reforming of methane
Autores: Abba, MO; Gonzalez-DelaCruz, VM; Colon, G; Sebti, S; Caballero, A
Revista: Applied Catalysis B: Environmental, 150-151 (2014) 459-465
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Some nickel catalysts supported on natural phosphate (NP) have been tested for the dry methane reforming reaction. Although the original impregnated 15%Ni/NP catalyst has no activity at all, the modification of the support by mechano-chemical and/or acid treatment strongly improved the catalytic performance, yielding a series of very active and stable catalysts. The chemical and physical characterization by X-ray diffraction (XRD), temperature programmed reduction (TPR), in situ X-ray absorption spectroscopy (XAS) and other techniques have shown that these treatments mainly modify the interaction between the nickel phase and the support surface. The nickel ions occupy calcium position in the surface of the phosphate phase, which stabilizes and improves the dispersion of nickel species. The final reduced catalysts present a much better dispersed metallic phase interacting with the NP surface, which has been identified as responsible for the observed outstanding catalytic performances.

Abril, 2014 | DOI: 10.1016/j.apcatb.2013.12.031

Titulo: Could an efficient WGS catalyst be useful in the CO-PrOx reaction?
Autores: Reina, TR; Papadopoulou, E; Palma, S; Ivanova, S; Centeno, MA; Ioannides, T; Odriozola, JA
Revista: Applied Catalysis B: Environmental, 150-151 (2014) 554-563
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This work presents an evaluation of a high performance series of water gas shift (WGS) catalysts in the preferential CO oxidation reaction (PrOx) in order to examine the applicability of the same catalyst for both processes as a first step for coupling both reactions in a single process. Gold based catalysts are applied in an extensive study of the CO-PrOx reaction parameters, such as λ, WHSV, CO concentration and [H2O]/[CO2] ratio in order to obtain the best activity/selectivity balance. CO and H2 oxidation reactions were treated separately in order to establish the degree of CO/H2 oxidation competition. Additionally the catalysts behavior in the CO-PrOx parallel reactions such a WGS and RWGS have been also carried out to analyze their effect on product composition.

Abril, 2014 | DOI: 10.1016/j.apcatb.2014.01.001

Titulo: Pt vs. Au in water-gas shift reaction
Autores: Castano, MG; Reina, TR; Ivanova, S; Centeno, MA; Odriozola, JA
Revista: Journal of Catalysis, 314 (2014) 1-9
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This work presents a comparison of the gold- and platinum-based catalysts behavior in the water–gas shift (WGS) reaction. The influence of the support, e.g., its composition and electronic properties, studied in detail by means of UV–Vis spectroscopy, of the metal nature and dispersion and of the stream composition has been evaluated. The catalytic performance of the samples is directly correlated with the electronic properties modification as a function of metal and/or support. Both metals present high activity in the selected reaction although in a different operation temperature window.

Abril, 2014 | DOI: 10.1016/j.jcat.2014.03.014

Titulo: Effect of the type of acid used in the synthesis of titania–silica mixed oxides on their photocatalytic properties
Autores: Llano, B; Hidalgo, MC; Rios, LA; Navio, JA
Revista: Applied Catalysis B: Environmental, 150-151 (2014) 389-395
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TiO2–SiO2 mixed oxides were synthesized by the sol–gel technique using three different acids, i.e., acetic, sulfuric, or chlorhydric acid. Their photocatalytic behavior was evaluated on the phenol oxidation in liquid phase and correlated with the characterization results. It was found that the kind of acid used during the preparation strongly influences the phase composition and stability of the TiO2 phases incorporated in the silica structure as well as the photocatalytic activity. In all cases, silica introduced a dispersive effect that stabilized the TiO2 crystalline phases upon calcination at 700 °C. SO42− and CH3COO− ions stabilized the anatase phase at high calcination temperatures (700 °C) leading to samples with the highest photoactivities. Cl− ions induced the formation of traces of rutile and brookite resulting in a lower photoactivity. The highest photoactivity was achieved with the catalyst synthesized with acetic acid and calcined at 700 °C (TS1-700-ace). The photocatalytic performance of this material was even better than that obtained with the commercial catalyst Degussa P-25.

Abril, 2014 | DOI: 10.1016/j.apcatb.2013.12.039

Titulo: Viability of Au/CeO2-ZnO/Al2O3 Catalysts for Pure Hydrogen Production by the Water-Gas Shift Reaction
Autores: Reina, TR; Ivanova, S; Delgado, JJ; Ivanov, I; Idakiev, V; Tabakova, T; Centeno, MA; Odriozola, JA
Revista: ChemCatChem, 6 (2014) 1401-1409
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The production of H2 pure enough for use in fuel cells requires the development of very efficient catalysts for the water–gas shift reaction. Herein, a series of gold catalysts supported on ZnO-promoted CeO2–Al2O3 are presented as interesting systems for the purification of H2 streams through the water–gas shift reaction. The addition of ZnO remarkably promotes the activity of an Au/CeO2/Al2O3 catalyst. This increase in activity is mainly associated with the enhanced oxygen storage capacity exhibited for the Zn-containing solids. High activity and good stability and resistance towards start-up–shut-down situations was found, which makes these catalysts a promising alternative for CO clean-up applications.

Abril, 2014 | DOI: 10.1002/cctc.201300992

Titulo: Metallic structured catalysts: Influence of the substrate on the catalytic activity
Autores: Dominguez, MI; Perez, A; Centeno, MA; Odriozola, JA
Revista: Applied Catalysis A-General, 478 (2014) 45-57
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In order to study the influence of the metallic substrate on the catalytic activity of structured micromonolithic catalysts, a CuOx/CeO2 catalyst was deposited on different oxidized or enameled metallic micromonoliths and tested in the PROX reaction under ideal and realistic conditions. The obtained results show as both activity and selectivity depend on the nature of the alloy and the nature of the interphase between the metal substrate and the catalyst layer. In oxidized micromonoliths, diffusion of Cr and Fe has been observed. For enameled micromonoliths, together with that diffusion, the interaction of the glass-ceramic interphase with the reactive gas streams resulted in the partial hydrolysis of this layer leading to diffusion toward the catalyst surface of the hydrolysis products, namely Na, Ca and Si cations. In some cases, the alteration of the surface composition favors the spreading of the copper active phase. As a result, it must be concluded that the metallic substrates are not spectators, at least in the PROX reaction, playing a fundamental role in the performances of the catalytic devices.

Abril, 2014 | DOI: 10.1016/j.apcata.2014.03.028

Titulo: Production of hydrogen by water photo-splitting over commercial and synthesised Au/TiO2 catalysts
Autores: Mendez, JAO; Lopez, CR; Melian, EP; Diaz, OG; Rodriguez, JMD; Hevia, DF; Macias, M
Revista: Applied Catalysis B: Environmental, 147 (2014) 439-452
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H2 production from methanol/water photo-splitting was compared using various commercial photocatalysts (Evonik P25 (P25), Hombikat UV-100 (HB) and Kronos vlp7000 (KR)) and others synthesised with a sol–gel-hydrothermal (HT) process and a sol–gel method followed by calcination (SG400 and SG750). All photocatalysts had been surface modified with Au at different concentrations, from 0.2 to 6.0 wt.%, using the photodeposition method. A complete characterisation study of the different photocatalysts was performed (BET, XRD, TEM, SEM-EDX, FTIR, UV–vis Reflectance Diffuse Spectra and aggregate size). The experiments were conducted for 3.5 h using 1 g L−1 of photocatalyst with methanol (25 vol.%) as sacrificial agent. In addition to H2 generation, production of the main intermediates, formaldehyde and formic acid, and of CO2 was also evaluated. The commercial photocatalyst KR at 0.8 wt.% Au had the highest H2 production of all the photocatalysts studied with 1542.9 μmol h−1. Of the photocatalysts synthesised by our group, SG750 at Au loading of 2.0 wt.% gave the highest H2 production of 723.1 μmol h−1. The SG750 photocatalyst at Au loading of 2.0 wt.% also had the highest H2 production yield per unit of surface area at 45.5 μmol g h−1 m−2.

Marzo, 2014 | DOI: 10.1016/j.apcatb.2013.09.029

Titulo: Surface Oxygen Vacancies in Gold Based Catalysts for CO Oxidation
Autores: Romero-Sarria, F; Plata, JJ; Laguna, OH; Marquez, AM; Centeno, MA; Sanz, JF; Odriozola, JA
Revista: RSC Advances, 4 (2014) 13145-13152
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Experimental catalytic activity measurements, Diffuse Reflectance Infrared Fourier Spectroscopy, and Density Functional Theory calculations are used to investigate the role and dynamics of surface oxygen vacancies in the CO oxidation with O2 catalyzed by Au nanoparticles supported on a Y-doped TiO2 catalyst. Catalytic activity measurements show that the CO conversion is improved in a second cycle of reaction if the reactive flow is composed by CO and O2 (and inert) while if water is present in the flow, the catalyst shows a similar behaviour in two successive cycles. DRIFTS-MS studies indicate the occurrence of two simultaneous phenomena during the first cycle in dry conditions: the surface is dehydroxylated and a band at 2194 cm-1 increases (proportionally to the number of surface oxygen vacancies). Theoretical calculations were conducted in order to explain these observations. On one hand, the calculations show that there is a competition between gold nanoparticles and OH to occupy the surface oxygen vacancies and that the adsorption energy of gold on these sites increases as the surface is being dehydroxylated. On another hand, these results evidence that a strong electronic transfer from the surface to the O2 molecule is produced after its adsorption on the Au/TiO2 perimeter interface (activation step), leaving the gold particle in a high oxidation state. This explains the appearance of a band at a wavenumber unusually high for the CO adsorbed on oxidized gold particles (2194 cm-1) when O2 is present in the reactive flow. These simultaneous phenomena indicate that a gold redispersion on the surface occurs under reactive flow in dry conditions generating small gold particles very actives at low temperature. This fact is notably favoured by the presence of surface oxygen vacancies that improve the surface dynamics. The obtained results suggest that the reaction mechanism proceeds through the formation of a peroxo-like complex formed after the electronic transfer from the surface to the gas molecule.

Marzo, 2014 | DOI: 10.1039/c3ra46662k

Titulo: Influence of the acid–base properties over NiSn/MgO–Al2O3 catalysts in the hydrogen production from glycerol steam reforming
Autores: Bobadilla, LF; Penkova, A; Romero-Sarria, F; Centeno, MA; Odriozola, JA
Revista: International Journal of Hydrogen Energy, 39 (2014) 5704-5712
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In this work we have investigated the hydrogen production from glycerol steam reforming. The effect of the acid-base properties was evaluated using four catalysts based in an alloy Ni-Sn as active phase supported over (Upsilon)-Al2O3 with different content in MgO, varying between 0 and 30 wt.% The incorporation of MgO results in the formation of MgAl2O4 spinel, which modifies the acid-base properties of the catalyst. Addition of MgO favored the glycerol conversion into gas, and the catalyst loaded with 10 wt.% MgO exhibited better catalytic performance and higher stability. A blank test with quartz was performed indicating that pyrolysis of glycerol takes place in the quartz.

Marzo, 2014 | DOI: 10.1016/j.ijhydene.2014.01.136

Titulo: Understanding the Role of the Cosolvent in the Zeolite Template Function of Imidazolium-Based Ionic Liquid
Autores: Ayala, R; Ivanova, S; Blanes, JMM; Romero-Sarria, F; Odriozola, JA
Revista: Journal of Physical Chemistry B, 118 (2014) 3650–3660
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In this work, a study for understanding the role played by [ClBmim], [BF4Bmim], [PF6Bmim], and [CH3SO3Bmim] ionic liquids (ILs) in the synthesis of zeolites is presented. The use of [ClBmim] and [CH3SO3Bmim] ILs, as reported earlier [ Chem. Eur. J. 2013, 19, 2122] led to the formation of MFI or BEA type zeolites. Contrary, [BF4Bmim] and [PF6Bmim] ILs did not succeed in organizing the Si–Al network into a zeolite structure. To try to explain these results, a series of quantum mechanical calculations considering monomers ([XBmim]) and dimers ([XBmim]2) by themselves and plus cosolvent (water or ethanol) were carried out, where X ≡ Cl–, BF4–, PF6–, or CH3SO3–. Our attention was focused on the similarities and differences among the two types of cosolvents and the relation between the structure and the multiple factors defining the interactions among the ILs and the cosolvent. Although a specific pattern based on local structures explaining the different behavior of these ILs as a zeolite structuring template was not found, the calculated interaction energies involving the Cl– and CH3SO3– anions were very close and larger than those for BF4– and PF6– species. These differences in energy can be used as an argument to describe their different behavior as structure directing agents. Moreover, the topology of the cosolvent is also an ingredient to take into account for a proper understanding of the results.

Marzo, 2014 | DOI: 10.1021/jp410260g

Titulo: Gold supported on CuOx/CeO2 catalyst for the purification of hydrogen by the CO preferential oxidation reaction (PROX)
Autores: Laguna, OH; Hernandez, WY; Arzamendi, G; Gandia, LM; Centeno, MA; Odriozola, JA
Revista: Fuel, 134 (2014) 9-20
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Hydrogen produced from the conversion of hydrocarbons or alcohols contains variable amounts of CO that should be removed for some applications such as feeding low-temperature polymer electrolyte membrane fuel cells (PEMFCs). The CO preferential oxidation reaction (PROX) is particularly well-suited for hydrogen purification for portable and on-board applications. In this work, the synthesis and characterization by XRF, BET, XRD, Raman spectroscopy and H2-TPR of a gold catalyst supported on a copper−cerium mixed oxide (AuCeCu) for the PROX reaction are presented. The comparison of this catalyst with the copper–cerium mixed oxide (CeCu) revealed that the experimental procedure used for the deposition of gold gave rise to the loss of reducible material by copper lixiviation. However, the AuCeCu solid was more active for CO oxidation at low temperature. A kinetic study has been carried over the AuCeCu catalyst for the PROX reaction and compared with that of the CeCu catalyst. The main difference between the models affected the contribution of the CO adsorption term. This fact may be related to the surface electronic activity produced by the interaction of the cationic species in the AuCeCu solid, able to create more active sites for the CO adsorption and activation in the presence of gold.

Enero, 2014 | DOI: 10.1016/j.fuel.2013.10.072

Titulo: Spinodal decomposition and precipitation in Cu–Cr nanocomposite
Autores: Sheibani, S; Heshmati-Manesh, S; Ataie, A; Caballero, A; Criado, JM
Revista: Journal of Alloys and Compounds, 587 (2014) 670-676
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In this study, spinodal decomposition and precipitation mechanism of mechanically alloyed supersaturated Cu–3wt.%Cr and Cu–5wt.%Cr solid solutions was investigated under nonisothermal aging. Decomposition mechanism and kinetics were studied using differential scanning calorimetry (DSC) and X-ray diffraction (XRD) techniques. Also, the microstructure was characterized by transmission electron microscopy (TEM). Effect of Al2O3 reinforcement on the aging kinetics was also evaluated. It was found that Cu–3wt.%Cr and Cu–5wt.%Cr solid solutions undergo spinodal decomposition at initial stages of ageing. However, decomposition mechanism was changed to nucleation and growth by the aging progress. The aging kinetics for the Cu–Cr/Al2O3 composition appeared to be slightly faster than that for Cu–Cr, since the ageing activation energy is decreased in presence of Al2O3 nano-particles. This behavior is probably due to the higher dislocation density and other structural defects previously produced during ball milling. A detailed comparison of the DSC results with those obtained by TEM, showing good consistency, has been presented. The average size of Cr-rich precipitates was about 10 nm in the copper matrix.

Enero, 2014 | DOI: 10.1016/j.jallcom.2013.11.019

Titulo: Wall paintings studied using Raman spectroscopy: A comparative study between various assays of cross sections and external layers
Autores: Perez-Rodriguez, JL; Robador, MD; Centeno, MA; Siguenza, B; Duran, A
Revista: Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 120 (2014) 602-609
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This work describes a comparative study between in situ applications of portable Raman spectroscopy and direct laboratory measurements using micro-Raman spectroscopy on the surface of small samples and of cross sections. The study was performed using wall paintings from different sites of the Alcazar of Seville.

Little information was obtained using a portable Raman spectrometer due to the presence of an acrylic polymer, calcium oxalate, calcite and gypsum that was formed or deposited on the surface. The pigments responsible for different colours, except cinnabar, were not detected by the micro-Raman spectroscopy study of the surface of small samples taken from the wall paintings due to the presence of surface contaminants.

The pigments and plaster were characterised using cross sections. The black colour consisted of carbon black. The red layers were formed by cinnabar and white lead or by iron oxides. The green and white colours were composed of green emerald or atacamite and calcite, respectively. Pb3O4 has also been characterised. The white layers (plaster) located under the colour layers consisted of calcite, quartz and feldspars. The fresco technique was used to create the wall paintings.

A wall painting located on a gypsum layer was also studied. The Naples yellow in this wall painting was not characterised due to the presence of glue and oils.

This study showed the advantage of studying cross sections to completely characterise the pigments and plaster in the studied wall paintings.

Enero, 2014 | DOI: 10.1016/j.saa.2013.10.052

Titulo: Promoting effect of Ce and Mg cations in Ni/Al catalysts prepared from hydrotalcites for the dry reforming of methane
Autores: Djebarri, B; Gonzalez-Delacruz, VM; Halliche, D; Bachari, K; Saadi, A; Caballero, A; Holgado, JP; Cherifi, O
Revista: Reaction Kinetics, Mechanisms and Catalysis, 111 (2014) 259-275
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Several catalytic systems containing Ni/Mg/Al/Ce were synthesized from nitrates of Ni2+, Mg2+, Al3+ and Ce3+ cations with M2+/M3+ = 2 ratios by means of the carbonate co-precipitation method and subsequent calcination at 800 A degrees C. Atomic absorption spectroscopy, X-ray diffraction (XRD), FT-IR spectroscopy, BET, temperature programmed reduction and scanning electron microscopy were used in order to describe the structural, morphological and surface characteristics of the solids completely. The effect of substitution/incorporation of Al by Ce and/or Mg on NiAl sample was studied. XRD analyses confirm that on Al-containing samples (NiAl, NiMgAl), the formation of the precursors layered double hydroxide structure. On the other hand, on cerium containing samples (NiCe, NiMgCe), poorly resolved diffractograms were observed what can be explained by the large radius of cerium. The catalysts were evaluated in the reaction of CO2 reforming of methane at 750 A degrees C. NiCe and NiMgAl catalysts exhibit higher activity and a H-2/CO ratio of almost 1. NiAl and NiMgCe samples showed lower conversions and a CH4/CO2 ratio < 1, indicating the occurrence of reverse water gas shift reaction.

Enero, 2014 | DOI: 10.1007/s11144-013-0646-2

Titulo: Improved H2 production of Pt-TiO2/g-C3N4-MnOx composites by an efficient handling of photogenerated charge pairs
Autores: Obregon, S; Colon, G
Revista: Applied Catalysis B: Environmental, 144 (2014) 775-782
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Pt-TiO2/g-C3N4-MnOx hybrid structures are synthesized by means of a simple impregnation method of Pt-TiO2 and g-C3N4-MnOx. From the wide structural and surface characterization we have stated that TiO2/g-C3N4 composites are formed by an effective covering of g-C3N4 by TiO2. The modification of composite by Pt and/or MnOx leads to improved photoactivities for phenol degradation reaction. Moreover, enhanced photoactivities have been obtained for composites systems for H2 evolution reaction. The notably photocatalytic performance obtained was related with the efficient separation of charge pairs in this hybrid heterostructure.

Diciembre, 2013 | DOI: 10.1016/j.apcatb.2013.07.034

Titulo: Effect of gold on a NiLaO3 perovskite catalyst for methane steam reforming
Autores: Palma, S; Bobadilla, LF; Corrales, A; Ivanova, S; Romero-Sarria, F; Centeno, MA; Odriozola, JA
Revista: Applied Catalysis B: Environmental, 144 (2014) 846-854
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The effect of gold addition to a supported Ni SRM catalyst has been studied in this work in order to determine the influence of gold on both the amount and type of carbon species formed during the reaction. The structure of the support, a mixed La–Al perovskite, determines the catalyst reducibility and Ni particle size. Gold addition affects the metal particle size increasing metal dispersion on increasing the gold content. Therefore, although gold blocks step Ni sites, the more active sites for Csingle bondH activation, and increases electron density on nickel, the higher dispersion results in an apparently higher activity upon gold addition. Moreover, gold addition increases the catalyst stability by decreasing the rate of growth of carbon nanotubes.

Diciembre, 2013 | DOI: 10.1016/j.apcatb.2013.07.055

Titulo: Exalted photocatalytic activity of tetragonal BiVO4 by Er3+ doping through a luminescence cooperative mechanism
Autores: Obregon, S; Lee, SW; Colon, G
Revista: Dalton Transactions, 43 (2014) 311-316
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Er-doped BiVO4 are synthesized by means of a surfactant free microwave assisted hydrothermal method having good photoactivities under sun-like excitation for the degradation of methylene blue. From the structural and morphological characterization, it has been stated that the presence of Er3+ induces a slight stabilization of the tetragonal phase, probably due to its incorporation in the BiVO4 lattice. The best photocatalytic performances were attained for the samples with Er3+ content higher than 3 at%. The occurrence of the Er3+ doped tetragonal BiVO4 clearly induces higher photocatalytic activities. The existence of a luminescence process has been related with the enhanced photoactivity observed.

Diciembre, 2013 | DOI: 10.1039/C3DT51923F

Titulo: A ternary Er3+-BiVO4/TiO2 complex heterostructure with excellent photocatalytic performance
Autores: Obregon, S; Colon, G
Revista: RSC Advances, 4 (2014) 20765-20771
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Ternary erbium doped BiVO4/TiO2 complexes are synthesized by means of a simple impregnation method with good photoactivities under sun-like excitation for the degradation of phenol. From the structural and morphological characterization it has been stated that the presence of Er3+ induces a slight stabilization of the tetragonal phase probably due to its incorporation in the BiVO4 lattice. Therefore a ternary heterostructured material has been obtained. The best photocatalytic performance was attained for the samples with 1 wt% of Er3+-doped BiVO4 content with respect to TiO2. The occurrence of a complex structural mixture with the adequate band position leads to effective charge pair separation which induces higher photocatalytic activities.

Diciembre, 2013 | DOI: 10.1039/C3RA46603E

2013


Titulo: Au/CeO2 metallic monolith catalysts: influence of the metallic substrate
Autores: Tejada, LMM; Dominguez, MI; Sanz, O; Centeno, MA; Odriozola, JA
Revista: Gold Bulletin, 46 (2013) 221-231
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Ceria-based gold catalysts were successfully deposited on ferritic stainless steel (Fecralloy) and aluminium monoliths. The prepared monolithic and reference powder catalysts were characterized by means of S-BET, X-ray diffraction, glow discharge optical emission spectroscopy and scanning electron microscopy-energy dispersive X-ray analysis techniques and tested in the CO oxidation reaction. Characterization results put in evidence the diffusion of cations from the catalytic layer on the surface of the monoliths to the metallic oxide scale and inversely, from the oxide scale to the catalysts, thus altering the catalytic formulation and affecting the CO oxidation properties of the catalytic device. The extension and nature of the modifications produced depend on the nature of the catalysts and the metallic substrate, as well as the reaction conditions applied. These facts must be considered when gold catalysts are supported on metallic-structured devices.

Noviembre, 2013 | DOI: 10.1007/s13404-013-0102-0

Titulo: Preparation of Titanium Oxide/Silicon Oxide (TiO2/SiO2) systems through the solvothermal method for applications in photocatalysis
Autores: Galeano, L.; Navío, J.A.; Restrepo, G.M.; Marín, J.M.
Revista: Información Tecnológica, 24 (2013) 81-92
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Sistemas Óxido de Titanio/Óxido de Silicio (TiO2/SiO2) fueron obtenidos por anclaje de TiO2 en SiO2. El fotocatalizador TiO2 se obtuvo por alcohólisis del TiCl4 con 2-propanol y posterior cristalización a presión autógena a 200 °C, excluyendo etapas de calcinación a altas temperaturas. Se emplearon diferentes relaciones SiO2/TiCl4 para determinar su influencia en la estabilidad, propiedades y fotoactividad de los sistemas TiO2/SiO2. La actividad fotocatalítica fue evaluada por la fotodegradación de metanol en fase gaseosa. El TiO2 cristalizó como fase anatasa o como una mezcla rutilo/anatasa, dependiendo por la relación SiO2/TiCl4 inicial. Los resultados muestran que se producen materiales compuestos con alta cristalinidad del TiO2. Se encontró también que hay una fuerte relación entre la actividad fotocatalítica con las propiedades fisicoquímicas y de estas con las composiciones iniciales de síntesis.

Noviembre, 2013 | DOI: 10.4067/S0718-07642013000500010

Titulo: A single-source route to bulk samples of C3N and the co-evolution of graphitic carbon microspheres
Autores: King, TC; Matthews, PD; Holgado, JP; Jefferson, DA; Lambert, RM; Alavi, A; Wright, DS
Revista: Carbon, 64 (2013) 6-10
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The thermolysis of commercially available m-phenylenediamine (1,3-(NH2)2C6H4) at 800 °C under a static vacuum in a sealed quartz tube provides the first bulk synthesis of C3N, whose properties have only been predicted theoretically previously. Hollow carbon microspheres (CMSs) which do not contain significant nitrogen doping (1–3 μm diameter) are co-produced in the reaction and readily separated from the C3N flakes. The separate C3N flakes and CMSs have been characterized by electron microscopy, X-ray spectroscopy and X-ray diffraction. These studies show that the samples of C3N and CMSs both possess multi-layered turbostratic graphitic structures. A new mechanism for the template-free assembly of CMSs is proposed on the basis of electron microscopy that involves bubble evolution from a static carbonized layer.

Octubre, 2013 | DOI: 10.1016/j.carbon.2013.04.043

Titulo: Preferential oxidation of CO over Au/CuOx–CeO2 catalyst in microstructured reactors studied through CFD simulations
Autores: Uriz, I; Arzamendi, G; Dieguez, PM; Laguna, OH; Centeno, MA; Odriozola, JA; Gandia, LM
Revista: Catalysis Today, 216 (2013) 283-291
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A computational fluid dynamics (CFD) simulation study of the preferential oxidation of CO (CO-PROX) in microstructured reactors consisting in square and semicircular microchannels coated with an Au/CuOx–CeO2 catalyst is presented. The CO content of the feed stream was set at 1 vol.%. A parametric sensitivity analysis has been performed under isothermal conditions revealing that an optimal reaction temperature exists that leads to a minimum CO content at the microreactor exit. The influence of the space velocity, CO2 concentration and oxygen-to-CO molar ratio in the feed stream (λ), catalyst loading, and microchannel characteristic dimension (d) on the microreactor performance has been investigated. Under suitable conditions, the CO concentration can be reduced below 10 ppm at relatively low temperatures within the 155–175 °C range. A negative effect of the increase of d from 0.35 mm to 2.8 mm on the CO removal efficiency has been found and attributed to a more detrimental effect of the mass transport limitations on the oxidation of CO than that of H2. Non-isothermal CFD simulations have been performed to investigate the cooling of the CO-PROX reactor with air or a fuel cell anode off gas surrogate in parallel microchannels. Due to the very rapid heat transfer allowed by the microreactor and the strong influence of the reaction temperature on the exit CO concentration, a careful control of the coolant flow rate and inlet temperature is required for proper reactor operation. The microreactor behavior is virtually isothermal.

Octubre, 2013 | DOI: 10.1016/j.cattod.2013.04.023

Titulo: In situ FT-IR study of the adsorption and photocatalytic oxidation of ethanol over sulfated and metallized TiO2
Autores: Murcia, JJ; Hidalgo, MC; Navio, JA; Arana, J; Dona-Rodriguez, JM
Revista: Applied Catalysis B: Environmental, 142-143 (2013) 205-213
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TiO2 Degussa P25, TiO2 prepared by sol–gel submitted to sulfation pre-treatment and some metallized catalysts obtained by photodeposition of Au or Pt over the sulfated TiO2, were evaluated in the reaction of ethanol photo-oxidation. FT-IR spectroscopy was used to investigate the surface features of the photocatalysts, identifying adsorbed species and following the evolution of intermediate products in the ethanol photo-oxidation reaction. Nature of surface acidity in terms of Brönsted and Lewis centers was also studied.

Results showed that sulfation pre-treatment and metallization were important factors influencing the selectivity. Acetaldehyde was the main oxidation product on sulfated TiO2; in the case of P25 also acetates production was observed. The photodeposition of metals had a detrimental effect on the selectivity to acetaldehyde; on metallized catalysts the formation of stable secondary intermediates was detected.

Based on these findings, a reaction pathway for the ethanol photo-oxidation over the different photocatalysts, via acetaldehyde or via acetate formation is proposed.

Septiembre, 2013 | DOI: 10.1016/j.apcatb.2013.05.022

Titulo: Monoclinic–Tetragonal Heterostructured BiVO4 by Yttrium Doping with Improved Photocatalytic Activity
Autores: Usai, S; Obregon, S; Becerro, AI; Colon, G
Revista: Journal of Physical Chemistry C, 117 (2013) 24479-24484
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Yttrium-doped BiVO4 has been synthesized by means of a surfactant free hydrothermal method having good photoactivities under sun-like excitation for the degradation of Methylene Blue (MB). From the structural and morphological characterization it has been stated that the presence of Y3+ induces the progressive stabilization of the tetragonal phase and the slight higher surface area values. By following the tetragonal cell parameters, the substitutional incorporation of Y3+ into the BiVO4 tetragonal lattice might be considered. Best photocatalytic performances were attained for the samples with Y3+ content of 3.0 at. % for which the MB degradation rate constant appears 2-fold higher. Furthermore, photoactivities for visible-light-driven O2 evolution demonstrate that the photocatalytic performance of the best Y-doped system (initial rate of O2 evolution, 285 μmol g–1 h–1) was more than 5 times that of undoped m-BiVO4 (initial rate of O2 evolution, 53 μmol g–1 h–1). The occurrence of Y3+ doping and a monoclinic–tetragonal heterostructured BiVO4 system induces the higher photocatalytic activities. PL analysis provides a clear evidence of the lower charge carriers recombination in heterostructured yttrium-doped systems.

Septiembre, 2013 | DOI: 10.1021/jp409170y

Titulo: Gold(III) stabilized over ionic liquids grafted on MCM-41 for highly efficient three-component coupling reactions
Autores: Bobadilla, LF; Blasco, T; Odriozola, JA
Revista: Physical Chemistry Chemical Physics, 39 (2013) 16927-16934
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Two alkoxysilyl-modified ionic liquids (ILs) have been synthesized and further grafted onto mesoporous silica, MCM-41; these ionic liquids were used for dispersing AuCl3 catalysts that activate C–H bonds as required for the synthesis of propargylamines by coupling alkyne, aldehyde and amine (A3 coupling) species. 29Si NMR experiments demonstrate the formation of covalent bonds between alkoxysilyl-modified Bmim IL and the MCM-41 surface through silanol groups. The catalytic activities of Au(III)-supported MCM-41 and Au(III) homogeneous catalysts are lower than those obtained for the IL functionalized Au–MCM-41 solids when the same gold loading is considered. An interaction between Au(III) species and the IL is proposed for explaining the stabilization of gold(III) species. However, successive reaction cycles result in a decrease in the catalytic activity that has been explained on the basis of gold leaching.

Septiembre, 2013 | DOI: 10.1039/C3CP52924J

Titulo: Promotional effect of the base metal on bimetallic Au-Ni/CeO2 catalysts prepared from core-shell nanoparticles
Autores: Holgado, JP; Ternero, F; Gonzalez-delaCruz, VM; Caballero, A
Revista: ACS Catalysis, 3 (2013) 2169-2180
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A set of three catalysts (a Au–Ni bimetallic and their corresponding Au and Ni monometallics) has been prepared by impregnation of previously prepared suspensions of monodisperse metallic particles to ensure the precise control of their physicochemical characteristics (size and composition). The Au–Ni/CeO2 bimetallic catalysts present better reactivity toward CO oxidation than monometallic Au/CeO2 and Ni/CeO2 prepared under identical conditions. “operando-like” characterization of Ni and Au atoms into the bimetallic particles using, among other techniques, ambient-pressure photoelectron spectroscopy and diffuse reflectance infrared Fourier transform spectroscopy has allowed us to determine that under oxidative conditions the samples present a Au@NiO core–shell distribution, where Ni surface atoms are affected by an electronic effect from inner Au atoms.

Agosto, 2013 | DOI: 10.1021/cs400293b

Titulo: A low-temperature single-source route to an efficient broad-band cerium(III) photocatalyst using a bimetallic polyoxotitanium cage
Autores: Lv, YK; Yao, MM; Holgado, JP; Roth, T; Steiner, A; Gan, LH; Lambert, RM; Wright, DS
Revista: RSC Advances, 3 (2013) 13659-13662
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Aqueous hydrolysis of a series of cerium-containing polyoxotitanium cages gives Ce(III)-doped TiO2 [TiO2(Ce)] or TiO2-supported Ce(III)2Ti2O7, depending on the starting Ti : Ce ratio of the precursor. TiO2-supported Ce2Ti2O7 exhibits superior photocatalytic activity to the Ce-doped TiO2 materials and unusual broad-band absorption behaviour across the visible and near-infrared regions.

Agosto, 2013 | DOI: 10.1039/C3RA41524D

Titulo: On the different photocatalytic performance of BiVO4 catalysts for Methylene Blue and Rhodamine B degradation
Autores: Obregon, S; Colon, G
Revista: Journal of Molecular Catalysis A: Chemical, 376 (2013) 40-47
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BiVO4 hierarchical structures were synthesized by means of a surfactant free hydrothermal method having good photoactivities for the degradation of Methylene Blue and Rhodamine B under UV–vis irradiation. From the structural and morphological characterization it has been stated that BiVO4 present the monoclinic crystalline phase with different morphologies depending on the pH value. For Methylene Blue the photodegradation rate is strongly affected by the crystallite size and higher (0 0 4) facet exposition. On the contrary, for Rhodamine B, the ζ-potential of the surface clearly determines the photocatalytic performance of BiVO4 catalyst.

Agosto, 2013 | DOI: 10.1016/j.molcata.2013.04.012

Titulo: Role of activated carbon on the increased photocatalytic activity of AC/Bi2WO6 coupled materials
Autores: Murcia-López, S; Navío, J.A.; Hidalgo, M.C.
Revista: Applied Catalysis A: General, 466 (2013) 51-59
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The photocatalytic activities of several Bi2WO6 and TiO2/Bi2WO6 materials with different activated carbon (AC) contents were studied for Rhodamine B (RhB) (and Phenol) photodegradation under UV–vis and vis illumination. A wide characterization of the materials was carried out. The addition of AC strongly affected the Bi2WO6 morphology although not the crystalline phase. Even in the material with the lowest AC content (2 wt% nominal content) a structure with hierarchical porosity was formed. AC presence increased the initial reaction rates in the degradation of RhB. An important improvement in the photoactivity under both UV–vis and vis illumination conditions was obtained with the lowest AC content (2 wt%) when compared to the pristine material Bi2WO6 or to the systems with higher AC additions. AC/TiO2/Bi2WO6 materials were also improved in comparison to the TiO2/Bi2WO6 heterostructure without carbon. The improvement cannot be only ascribed to adsorption capability and surface area effects. A mechanism explaining the role of AC on the photocatalytic activity improvement is proposed.

Agosto, 2013 | DOI: 10.1016/j.apcata.2013.06.022

Titulo: Effect of the alloy on micro-structured reactors for methanol steam reforming
Autores: Echave, FJ; Sanz, O; Velasco, I; Odriozola, JA; Montes, M
Revista: Catalysis Today, 213 (2013) 145-154
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Micro-monoliths and foams made of aluminium, Fecralloy® and brass were studied as substrates for structured systems for methanol steam reforming (MSR). All the alloys exhibited very adherent oxide layer produced by pre-treatment to improve the adhesion between substrate and catalyst. 2.5% Pd/ZnO catalyst was prepared and deposited on structured substrates. Both, good catalyst adhesion and stable catalytic performance were achieved in the case of brass micro-monoliths. The Fecralloy® and aluminium substrates reacted with the catalytic active components resulting in catalyst modification. The aluminium based substrates promoted dimethyl ether (DME) formation. Aluminium foam produced better performance than aluminium micro-monoliths that could be related to improved mass and heat transfer properties in foams.

Agosto, 2013 | DOI: 10.1016/j.cattod.2013.02.027

Titulo: Hydrogen production using Pt-loaded TiO2 photocatalysts
Autores: Melian, EP; Lopez, CR; Mendez, AO; Diaz, OG; Suarez, MN; Rodriguez, JMD; Navio, JA; Hevia, DF
Revista: International Journal of Hydrogen Energy, 38 (2013) 11737-11748
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A series of synthesised TiO2-based and commercial photocatalysts were modified by Pt photodeposition and a study made of their photocatalytic activity in hydrogen production. The modified commercial photocatalysts were Evonik P25, Kronos vlp7000 and Hombikat UV-100, and the other modified photocatalysts were synthesised by our group using sol–gel and sol–gel hydrothermal processes (SG400, SG750 and HT). Pt weight percentages used in the study were 0.5, 1.0 and 2.1 wt.% (Pt/TiO2). The photocatalysts were extensively characterised by X-ray diffraction (XRD), UV–vis diffuse reflectance, Brunauer–Emmett–Teller (BET) surface area measurement, transmission electron microscopy (TEM), scanning electron microscopy (SEM–EDX), Fourier transform infrared spectroscopy (FTIR) and laser light dispersion. Methanol (25% vol.) was used as sacrificial agent over the 8 h of the hydrogen production tests and measurements were taken of the final concentrations of formaldehyde and formic acid as well as initial and final TOC. Photoactivity of all photocatalysts increased in the presence of Pt. The most efficient of the synthesised photocatalysts was SG750 and of the commercial photocatalysts P25. Maximum production of SG750 was 1846 μmol h−1 at 1.0 wt.% Pt and its production per surface unit was notably higher than that of P25.

Agosto, 2013 | DOI: 10.1016/j.ijhydene.2013.07.006

Titulo: Erbium doped TiO2–Bi2WO6 heterostructure with improved photocatalytic activity under sun-like irradiation
Autores: Obregon, S; Colon, G
Revista: Applied Catalysis B: Environmental, 140-141 (2013) 299-305
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Erbium doped TiO2–Bi2WO6 have been synthesized by means of a surfactant free hydrothermal method having good photoactivities under sun-like excitation for the degradation of Rhodamine B. From the structural and morphological characterization it has been stated that the presence of Er3+ induces a progressive russelite cell contraction due to its incorporation in the Bi2WO6 lattice in substitutional sites. The best photocatalytic performance was attained for the samples with 1 at% of Er. From the study of the photocatalytic activity under different irradiation conditions it can be inferred that Er3+ presence induces a significant improvement of the photoactivity in the UV range. The evolution of band-gap values seems to be similarly related with the reaction rate progression. Thus, the higher band-gap values in lower Er doped systems would be the cause of a better electron hole separation under UV irradiation.

Julio, 2013 | DOI: 10.1016/j.apcatb.2013.04.014

Titulo: Degradation of Rhodamine B/Phenol Mixtures in Water by Sun-Like Excitation of a Bi2WO6–TiO2 Photocatalyst
Autores: Murcia-López, S; Navío, J.A.; Hidalgo, M.C.
Revista: Photochemistry and Photobiology, 89 (2013) 832-840
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Bi2WO6 and Bi2WO6–TiO2 (5% molar Ti) nano-heterostructures were synthesized by a hydrothermal method. The properties of the synthesized catalysts were characterized, having high photoactivity for Rhodamine B degradation under sun-like illumination, explained by a synergetic mechanism previously proposed through UV and visible induced processes, in which the photosensitization effect of Rhodamine B is considered. We now report that using Phenol, a molecule which does not lead the photosensitization process, the photoactivity decreased considerably, thus emphasizing how important is the model molecule selected as degradation substrate for evaluating the photoactivity. The photocatalytic properties of the synthesized catalysts have been evaluated by exposing a mixture of Rhodamine B and Phenol in water, to different illumination conditions. It can be confirmed that the photoinduced mechanism via the photosensitization of Rhodamine B is a key factor responsible for the increase on the photocatalytic activity showed by the Bi2WO6–TiO2 compound and that the degradation mechanism of Rhodamine B is not changed by the simultaneous presence of other transparent substrate as Phenol.

Junio, 2013 | DOI: 10.1111/php.12054

Titulo: Cyclohexane photocatalytic oxidation on Pt/TiO2 catalysts
Autores: Murcia, JJ; Hidalgo, MC; Navio, JA; Vaiano, V; Sannino, D; Ciambelli, P
Revista: Catalysis Today, 209 (2013) 164-169
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Gas-solid heterogeneous photocatalytic oxidation (PCO) of cyclohexane in humidified air over TiO2 and Pt/TiO2 catalyst was studied.

Pt/TiO2 photocatalysts were synthesized by photodeposition method at different Pt loadings (0.5–2 wt.%). The addition of 0.5 wt.% Pt does not significantly modify the TiO2 properties. The increase in Pt loading induces to an aggregation of metallic particles on TiO2 surface.

The cyclohexane PCO was performed in a fluidized bed photoreactor at 60 and 100 °C. Pure TiO2 was more active than 1 and 2 wt.% Pt/TiO2 samples at 60 °C. Nevertheless, the conversion level increases with temperature on Pt/TiO2 photocatalysts. The cyclohexane was mineralized into CO2, water and low amount of CO. A beneficial effect of Pt addition was found, since total CO2 selectivity was obtained. The Pt/TiO2 photocatalysts prepared by photodeposition provide the total cyclohexane PCO without CO production. Photocatalysts deactivation was not observed in any performed test. Evidence of an opportune tuning of temperature is highlighted.

Mayo, 2013 | DOI: 10.1016/j.cattod.2012.11.018

Titulo: Steam reforming of methanol over supported Ni and Ni–Sn nanoparticles
Autores: Bobadilla, LF; Palma, S; Ivanova, S; Dominguez, MI; Romero-Sarria, F; Centeno, MA; Odriozola, JA
Revista: International Journal of Hydrogen Energy, 38 (2013) 6646-6656
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The influence of the synthesis method and Sn addition on Ni/CeO2–MgO–Al2O3 catalyst is correlated to its catalytic behavior in the reaction of methanol steam reforming. The catalysts prepared by impregnation method are compared to samples obtained by deposition of previously obtained nanoparticles by the polyol method. X-ray diffraction (XRD), specific surface area measurements and H2-temperature programmed reduction (TPR) were used to characterize the catalysts. The differences of the structure, phase transformation and reduction behavior are discussed and related to the catalytic performance of the samples as well as the nature of the carbonaceous deposits formed during the reaction.

Abril, 2013 | DOI: 10.1016/j.ijhydene.2013.03.143

Titulo: In situ characterization of iron-promoted ceria–alumina gold catalysts during the water-gas shift reaction
Autores: Reina, TR; Xu, WQ; Ivanova, S; Centeno, MA; Hanson, J; Rodriguez, JA; Odriozola, JA
Revista: Catalysis Today, 205 (2013) 41-48
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In this work an in situ XRD and XANES study of two gold catalysts supported on iron-promoted ceria–alumina carriers was carried out during the water-gas shift reaction (WGS). The first catalyst, Au/CeO2–FeOx/Al2O3, was prepared using a commercial alumina support in order to obtain a Ce–Fe oxide solid solution and in the second one, Au/FeOx/CeO2–Al2O3, an iron oxide monolayer was deposited onto a ceria–alumina commercial support to promote its redox properties. Catalytic activities in the WGS were remarkably different for both systems. The catalytic activity of the Au/CeO2–FeOx/Al2O3 catalyst was higher than the one shown by the Au/FeOx/CeO2–Al2O3 catalyst that resulted active at much higher temperatures. In situ XRD demonstrates the formation of magnetite (Fe3O4) during the WGS reaction and the presence of big gold particles, ca. 21 nm in diameter, in the low-activity system. This in contrast to the high-activity system that shows undetectable gold nanoparticles and the absence of diffraction peaks corresponding to magnetite during the WGS. The data obtained using in situ XANES states that Ce4+ species undergo reduction to Ce3+during the WGS for both catalysts, and also confirms that in the high-activity catalyst iron is just present as Fe3+ species while in the low-activity catalyst Fe3+ and Fe2+ coexist, resulting in iron spinel observed by XRD. These results allow us conclude that the Au/CeO2–Fe2O3/Al2O3 catalyst is a suitable catalyst for WGS when avoiding the formation of magnetite, in such a case Fe3+ species favors reduction and water splitting increasing the catalytic activity in the WGS reaction.

Marzo, 2013 | DOI: 10.1016/j.cattod.2012.08.004

Titulo: Au/TiO2 supported on ferritic stainless steel monoliths as CO oxidation catalysts
Autores: Milt, VG; Ivanova, S; Sanz, O; Dominguez, MI; Corrales, A; Odriozola, JA; Centeno, MA
Revista: Applied Surface Science, 270 (2013) 169-177
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Metallic supported structured catalysts were obtained by washcoating AluchromYHf monoliths with an Au/TiO2 catalyst. The powder catalyst was synthesized by DAE (direct anionic exchange) method. Using this catalyst, a stable slurry was prepared and used to washcoat the monoliths. TEM and SEM studies revealed that gold nanoparticles in the Au/TiO2 powder catalyst had an average diameter of 3–4 nm, but during the preparation of the structured catalyst, aggregate Au particles of the slurry reached diameters of 9 nm. Before coating, Aluchrom YHf monoliths were thermally treated to generate a homogeneous and well-adhered oxide rough surface layer, mainly composed of α-Al2O3 whiskers, which favored the anchoring of the catalyst. The catalytic layer deposited was well attached and contained not only the Au/TiO2 catalyst but also metallic oxides formed from stainless steel components that diffused through the oxide scale. The structural characterization was performed by XRD, XRF, TEM, SEM, GD-OES and SBET.

The catalytic activity of the powder and structured catalysts was tested in the oxidation of the CO reaction. Catalysts demonstrated to be active at room temperature. After a first activation run, and in spite of their larger gold particle size, the catalytic activities of the structured catalysts overcame those of the powder catalyst. This improvement is probably due to the segregation of the transition metal oxides toward the surface oxide scale.

Marzo, 2013 | DOI: 10.1016/j.apsusc.2012.12.159

Titulo: High-performance Er3+–TiO2 system: Dual up-conversion and electronic role of the lanthanide
Autores: Obregon, S; Kubacka, A; Fernandez-Garcia, M; Colon, G
Revista: Journal of Catalysis, 299 (2013) 298-306
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Erbium-doped TiO2 materials are synthesized by means of a surfactant-free hydrothermal method having good photoactivities for the liquid-phase degradation of phenol and MB and the gas phase of toluene. From the structural and morphological characterization, it has been stated that the presence of Er3+ induces a progressive anatase cell expansion due to its incorporation in the TiO2 lattice. The best photocatalytic performance was attained for the samples with 2 at% of Er3+ irrespective of the chemical degradation reaction essayed. From activity and optical studies under different irradiation excitation conditions, a dual-type mechanism is proposed to be at the origin of the photocatalytic activity enhancement. On one hand, the improvement observed under UV irradiation occurs by the effective charge separation promoted by Er3+ species which would act as electron scavenger. Besides, the up-conversion luminescence process of Er3+ allows profiting the NIR range of the lamp and transferring energy in the UV range to the TiO2. The dual action of Er ions located at anatase networks will open up a wide roadway for the developing of an integral solar active photocatalyst.

Febrero, 2013 | DOI: 10.1016/j.jcat.2012.12.021

Titulo: Impact of Ce–Fe synergism on the catalytic behaviour of Au/CeO2–FeOx/Al2O3 for pure H2 production
Autores: Reina, TR; Ivanova, S; Idakiev, V; Delgado, JJ; Ivanov, I; Tabakova, T; Centeno, MA; Odriozola, JA
Revista: Catalysis Science & Technology, 3 (2013) 779-787
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In this work the development of a series of gold catalysts, essentially based on γ-alumina promoted with a small superficial fraction of Ce–Fe mixed oxides, is reported. The catalytic behaviour is evaluated in the water gas shift reaction. The formation of a Ce–Fe solid solution is evidenced by XRD and related to the catalytic activity where the importance of the Ce–Fe interaction is demonstrated. The best catalyst reached CO conversions very close to the equilibrium limit. A long-term stability test is performed and the loss of activity is observed and attributed to reaction intermediates. Almost complete recovery of the initial conversion is achieved after oxidation treatment, suggesting that the problem of stability could be overcome by a suitable change in the reaction parameters thus leading to a highly efficient catalyst for future applications in H2 production and clean-up.

Febrero, 2013 | DOI: 10.1039/C2CY20537H

Titulo: Influence of the O2/CO ratio and the presence of H2O and CO2 in the feed-stream during the preferential oxidation of CO (PROX) over a CuOx/CeO2-coated microchannel reactor
Autores: Laguna, OH; Dominguez, MI; Oraa, S; Navajas, A; Arzamendi, G; Gandia, LM; Centeno, MA; Montes, M; Odriozola, JA
Revista: Catalysis Today, 203 (2013) 182-187
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The catalytic performance of a CuOx/CeO2 powder catalyst and that of a microchannel reactor or microreactor (MR) coated with the same solid was determined and compared. The catalytic activity measurements were carried out with varying O2/CO molar ratios in the feed-stream. In addition, the influence of the presence of CO2 and H2O in the reaction mixture was studied. Some discrepancies were observed between the performances of the powder catalyst and the MR depending on the O2/CO ratio. The MR presented a very good performance with a superior selectivity for CO conversion. This behaviour was due to a more efficient heat removal in the case of the MR that inhibited the H2 oxidation reaction and the r-WGS. The isothermicity of the microreactor during the process was demonstrated through the monitoring of the MR inlet and outlet temperatures.

Concerning the presence of CO2 or H2O in the feed-stream, both compounds gave rise to a decrease of the CO conversion. The negative effect on the catalytic performance was more marked when both compounds were fed together, although the principal inhibitor effect was associated to the CO2. This seems to be related with the formation of stable carbonates at the catalyst surface.

Febrero, 2013 | DOI: 10.1016/j.cattod.2012.04.021

Titulo: Preferential oxidation of CO in excess H2 over CuO/CeO2 catalysts: Characterization and performance as a function of the exposed face present in the CeO2 support
Autores: Gamarra, D; Camara, AL; Monte, M; Rasmussen, SB; Chinchilla, LE; Hungria, AB; Munuera, G; Gyorffy, N; Schay, Z; Corberan, VC; Conesa, JC; Martinez-Arias, A
Revista: Applied Catalysis B: Environmental, 130-131 (2013) 224-238
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A series of oxidised copper-cerium nanostructured catalysts prepared by impregnation of copper over ceria supports synthesized by different methods (hydrothermal with varying preparation parameters, microemulsion/precipitation), in order to achieve different specific morphologies (nanocubes, nanorods and nanospheres), have been examined with respect to their catalytic properties for preferential oxidation of CO in excess H2 (CO-PROX). The catalysts have been characterized in detail by XRD, Raman, SBET measurement, HREM, XPS, TPR and EPR, which allows establishing a model of structural characteristics of the catalysts. The characterization results have been correlated with analysis of CO-PROX catalytic properties by means of catalytic activity measurements complemented by operando-DRIFTS. Structural dependence of the CO oxidation reaction on the dispersed copper oxide entities as a function of the exposed face present at the surface of the different ceria supports is revealed. An important overall enhancement of the CO-PROX performance is detected for the sample supported on ceria nanocubes which is proposed to be a consequence of the interaction between copper oxide and (1 0 0) faces of the ceria support.

Enero, 2013 | DOI: 10.1016/j.apcatb.2012.11.008

Titulo: Multiple Zeolite Structures from One Ionic Liquid Template
Autores: Blanes, JMM; Szyja, BM; Romero-Sarria, F; Centeno, MA; Hensen, EJM; Odriozola, JA; Ivanova, S
Revista: Chemistry-A European Journal, 19 (2013) 2122-2130
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This study reports the use of 1-butyl-3-methyl imidazolium methanesulfonate ionic liquid as a template in the synthesis of zeolites. It is found that the silicon source determines the formation of beta (BEA), mordenite framework inverted (MFI), or analcime (ANA) zeolites. Depending on this source, different preorganized complexes are obtained that drive the formation of the different zeolite structures. In the presence of ethanol, the ionic liquid form preorganized complexes that drive the formation of MFI. In its absence, BEA is obtained. Whereas, the large amount of sodium present when using sodium metasilicate leads to ANA formation. A molecular simulation study of the relative stability of the template-framework system and location of the template provides further insight into the mechanism of synthesis.

Enero, 2013 | DOI: 10.1002/chem.201202556

Titulo: Improved photocatalytic activity of g-C3N4/TiO2 composites prepared by a simple impregnation method
Autores: Miranda, C; Mansilla, H; Yanez, J; Obregon, S; Colon, G
Revista: Journal of Photochemistry and Photobiology A: Chemistry, 253 (2013) 16-21
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g-C3N4 and TiO2 hybrid structures are synthesized by means of a simple impregnation method having good photoactivities for the degradation of phenol under UV irradiation. From the wide structural and surface characterization we have stated that the presence of g-C3N4 notably affect the surface feature of TiO2 (surface area and pore size distribution). Enhanced photoactivities have been obtained for composites systems. The best result was obtained for 2 wt% loading of g-C3N4 leading to a 70% of improvement with respect to bare TiO2 in the reaction rate. The effective charge carrier separation was proposed as the responsible of such improved photoactivity.

Enero, 2013 | DOI: 10.1016/j.jphotochem.2012.12.014

Titulo: Gas-phase Photocatalytic Partial Oxidation of Cyclohexane to Cyclohexanol and Cyclohexanone on Au/TiO2 Photocatalysts
Autores: Sannino, D; Vaiano, V; Ciambelli, P; Murcia, JJ; Hidalgo, MC; Navio, JA
Revista: Journal of Advanced Oxidation Technologies, 16 (2013) 71-82
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The heterogeneous photocatalytic partial oxidation of cyclohexane in gas-phase as an alternative green process for fine chemicals synthesis was successfully achieved on Au/TiO2 photocatalysts prepared by photodeposition technique. Different gold loadings ranging between 0.5 and 2 wt.% of photodeposited Au on TiO2 synthesized by sol-gel method were obtained by changing the concentration of gold precursor at fixed illumination intensity and time. The cyclohexane partial photoxidation was conducted in a gas-solid photocatalytic fluidized bed reactor at high illumination efficiency. Main observed reaction products were cyclohexanol, cyclohexanone and CO2. The resulting selectivity was dramatically influenced by the gold content. The reaction temperature was a critical parameter to reach the photocatalysts stability, avoiding deactivation phenomena while the tuning of Au content of the photocatalysts, resulted in the promotion of the formation of cyclohexanol or cyclohexanone with high selectivity. In particular, by increasing Au content, the process selectivity is completely reversed, passing from high cyclohexanol selectivity (75%) to high selectivity to cyclohexanone (80%). These promising results evidenced that Au/TiO2 catalysts in the selected operating conditions, are effective materials for the synthesis of cyclohexanone and cyclohexanol in gas-phase by photocatalysis, at very low reaction temperatures and without the additional step of catalyst recovering needed in the liquid partial oxidation of cyclohexane.

Diciembre, 2012 | DOI: ---

2012


Titulo: Hydrogenation of 2,2,2-trifluoroacetophenone: Molecular insight into the role of solvent in enantioselection
Autores: Rosa Pereñiguez; Gianluca Santarossa; Tamas Mallat; Alfons Baiker
Revista: Journal of Molecular Catalysis A: Chemical, 365 (2012) 39-49
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The unique solvent effect in the enantioselective hydrogenation of α-fluorinated ketones has been investigated in ten different solvents using the  hydrogenation of 2,2,2-trifluoroacetophenone (1) on cinchonine (CN)-modified Pt/Al2O3 as a model reaction. Application of strongly basic solvents – but also increasing hydrogen pressure or conversion – inverted the sense of enantiodifferentiation from (S)-alcohol (expected enantiomer based on the stereochemistry of CN) to (R)-alcohol. The known formation of hemiketals was the origin of the inversion in alcohols. Considering only the non-reacting solvents and low conversions at low pressures, the best correlation was established between the enantiomeric excess and the solvent basicity represented by the H-bond acceptor ability (β). In contrast to former proposals, solvent acidity (α) did not play a significant role. The experimental results are validated by theoretical calculations. The docking of 1 to CN has been investigated in the absence of solvent and also in the presence of toluene and dimethyl formamide. Several competing docking complexes have been isolated that can coexist on the metal surface. Detailed analyses of these complexes show that their stabilities depend on the formation of enantiospecific local interactions between 1, CN, and the platinum surface. The presence of solvent interferes with these interactions, affecting the relative stability of the docking complexes. A correlation between the solvent-induced interactions at molecular level and changes in enantioselectivity is suggested.

Noviembre, 2012 | DOI: 10.1016/j.molcata.2012.08.006

Titulo: Selective photooxidation of alcohols as test reaction for photocatalytic activity
Autores: Lopez-Tenllado, F. J.; Marinas, A.; Urbano, F. J.; Colmenares, J. C.; Hidalgo, M. C.; Marinas, J. M.; Moreno, J. M.
Revista: Applied Catalysis B-Environmental, 128 (2012) 150-158
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Twenty-four different titania-based systems synthesized through the sol–gel process varying the precursor (titanium isopropoxide or tetrachloride) and/or the ageing conditions (magnetic stirring, ultrasounds, microwave or reflux) were tested for liquid-phase selective photooxidation of 2-butenol (crotyl alcohol) to 2-butenal (crotonaldehyde) and gas-phase selective photooxidation of 2-propanol to acetone. To the best of our knowledge, the former process is suggested for the first time as test reaction for photocatalytic activity. Interestingly, both test reactions (despite having very different reactant/catalyst ratio and contact times) showed quite similar results in terms of influence of the precursor (titanium isopropoxide leading to better results than titanium tetrachloride) and the metals (the presence of iron, palladium or zinc being detrimental to activity whereas zirconium and especially gold improved the results as compared to pure titania). To our mind, these results give validity to both processes as test reactions for a fast screening of catalysts for photocatalytic tranformations. Finally, some gold-containing solids even improved photocatalytic activity of Degussa P25.

Octubre, 2012 | DOI: 10.1016/j.apcatb.2012.02.015

Titulo: Ethanol partial photoxidation on Pt/TiO2 catalysts as green route for acetaldehyde synthesis
Autores: Murcia, JJ; Hidalgo, MC; Navio, JA; Vaiano, V; Ciambelli, P; Sannino, D
Revista: Catalysis Today, 196 (2012) 101-109
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Heterogeneous photocatalytic partial oxidation of ethanol was studied over different Pt/TiO2 as an alternative green process for acetaldehyde production.

The catalysts were synthesized through the photodeposition of Pt over sol–gel TiO2 with platinum loads of 0.5 and 1 wt.%. The effect of some experimental conditions during photodeposition, such as deposition time and Pt loading, was investigated. A short deposition time at 0.5 wt.% Pt nominal loading led to small average particle size of platinum (2–3 nm) homogeneously distributed all over the TiO2 surface.

Ethanol partial oxidation was tested in a gas–solid photocatalytic fluidized bed reactor at high illumination efficiency, using different reaction temperatures. Activity results have been correlated with characterization results of the different samples. Platinized samples prepared with short deposition times showed high conversion levels and high selectivity to acetaldehyde. Materials prepared at longer times, 120 min, showed selectivities >98%, although with lower ethanol conversion.

Sample with 1 wt.% Pt loading prepared with 15 min deposition time combined a good compromise between a relevant ethanol conversion and a very high selectivity to acetaldehyde at a selected reaction temperature of 80 °C, with an acetaldehyde yield higher than 80%, which make of this catalyst a good candidate for acetaldehyde production by photocatalysis.

Octubre, 2012 | DOI: 10.1016/j.cattod.2012.02.033

Titulo: Gold supported on pillared clays for CO oxidation reaction: Effect of the clay aggregate size
Autores: Alvarez, A; Moreno, S; Molina, R; Ivanova, S; Centeno, MA; Odriozola, JA
Revista: Applied Clay Science, 69 (2012) 22-29
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A series of 1% m/m gold particles supported on Fe, Ce and Al pillared bentonite (from Valle del Cauca, Colombia) and clay “M64” (from Tolima, Colombia) using three different fractions of aggregate sizes (≤ 2 μm, ≤ 50 μm, and ≤ 150 μm) were characterized by particle size measurements, X-ray diffraction, transmission electronic microscopy (TEM), SBET and X-ray fluorescence spectrometry (XRF) techniques. The materials tested with CO oxidation. The separation yield for each fraction depended on the type of clay. Whatever the clay or the aggregate size, the pillaring process was successfully carried out, introducing Fe, Ce and Al pillars and increasing the microporosity and the specific surface area of the material. Gold particles presented a homogenous distribution of 2–3 nm on the pillared bentonite, and of about 10 nm on the pillared clay M64. The aggregate size slightly influenced the amount of deposited gold particles and their size. All gold catalysts were active in CO oxidation, the activity depending on the nature of the clay as well as the gold loading and average gold particle size but not on the aggregate size.

Octubre, 2012 | DOI: 10.1016/j.clay.2012.07.008

Titulo: Influence of PVP in magnetic properties of NiSn nanoparticles prepared by polyol method
Autores: Bobadilla, LF; Garcia, C; Delgado, JJ; Sanz, O; Romero-Sarria, F; Centeno, MA; Odriozola, JA
Revista: Journal of Magnetism and Magnetic Materials, 324 (2012) 4011-4018
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The influence of PVP on the magnetic properties of NiSn nanoparticles prepared by polyol method has been studied. NiSn nanoparticles exhibit superparamagnetic behavior although there is a ferromagnetic contribution due to particles agglomerated below the blocking temperature. The particle size is controlled by the addiction of PVP in varying amounts. The addition of PVP also favours the particles isolation, narrow the particle size distribution and decrease the interparticle interaction strength increasing the superparamagnetic contribution.

Octubre, 2012 | DOI: 10.1016/j.jmmm.2012.07.005

Titulo: Preparation of nanostructured nickel aluminate spinel powder from spent NiO/Al2O3 catalyst by mechano-chemical synthesis
Autores: Nazemi, M. K.; Sheibani, S.; Rashchi, F.; Gonzalez-DelaCruz, V. M.; Caballero, A.
Revista: Advanced Powder Technology, 23 (2012) 833-838
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In this paper, the possibility of mechano-chemical synthesis, as a single step process for preparation of nanostructured nickel aluminate spinel powder from NiO/Al2O3 spent catalyst was investigated. Powder samples were characterized in terms of composition, morphology, structure, particle size and surface area using complementary techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), differential thermal analysis (DTA) and volumetric adsorption of nitrogen. It was found that formation of spinel was possible after 60 h of milling with no heat treatment. Additionally, influence of mechanical activation on the heat treatment temperature was discussed. It was observed that heat treatment of 15 h milled sample at 1100 °C is enough to produce nickel aluminate spinel. A product of direct mechanical milling showed higher value of surface area (42.3 m2/g) and smaller crystallite size (12 nm) as compared to the heat treated product.

Octubre, 2012 | DOI: 10.1016/j.apt.2011.11.004

Titulo: Effect of deposition of silver on structural characteristics and photoactivity of TiO2-based photocatalysts
Autores: Melian, EP; Diaz, OG; Rodriguez, JMD; Colon, G; Navio, JA; Macias, M; Pena, JP
Revista: Applied Catalysis B-Environmental, 127 (2012) 112-120
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The homemade bare TiO2 photocatalyst obtained in a previous work was modified with nanosized silver particles by liquid impregnation and photodeposition methods to obtain different noble metal loadings (0.3–1 at.%). Characterization of the synthesized photocatalysts was carried out by the BET method, XPS, TEM, SEM-EDX, XRD and diffuse reflectance measurements. Photocatalytic activity of these silver-deposited TiO2 nanoparticles was tested by photocatalytic degradation of phenol as a reference model representing phenolic pollutants. The noble metal content on the TiO2 surface affected the efficiency of the photocatalytic process, and the photocatalytic activity of noble metal-modified TiO2 was considerably better than that of bare TiO2. Phenol decomposition rate was higher with TiO2 modified by the liquid impregnation method than with TiO2 modified by the photodeposition method.

Septiembre, 2012 | DOI: 10.1016/j.apcatb.2012.08.007

Titulo: Insights towards the influence of Pt features on the photocatalytic activity improvement of TiO2 by platinisation
Autores: Murcia, JJ; Navio, JA; Hidalgo, MC
Revista: Applied Catalysis B-Environmental, 126 (2012) 76-85
resumen | texto completo


The influence of Pt features, such as particle size, dispersion, oxidation state and amount of metal, on the improvement of the photoactivity of TiO2 for phenol and methyl orange degradation was studied.

The size of Pt deposits was precisely controlled by changing deposition time under medium light intensity during the photodeposition, with sizes ranging from 3 to 6 nm. Pt oxidation state was also strongly dependent on the photodeposition time.

Photocatalytic activity results showed that the fraction of metallic platinum (Pt0) was the crucial factor for the improvement of the activity. When the fraction of Pt0 was similar, metal deposit size became the dominant parameter influencing the activity.

The influence of the substrate to be degraded (phenol or methyl orange) was also studied.

Agosto, 2012 | DOI: 10.1016/j.apcatb.2012.07.013

Titulo: Making Photo-selective TiO2 Materials by Cation–Anion Codoping: From Structure and Electronic Properties to Photoactivity
Autores: Marquez, AM; Plata, JJ; Ortega, Y; Sanz, JF; Colon, G; Kubacka, A; Fernandez-Garcia, M
Revista: Journal of Physical Chemistry C, 116 (2012) 18759-18767
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Photoselective oxidation yielding high-added value chemicals appears as a green novel process with potential to be explored. In this study we combine spectroscopic XPS (N 1s and O 1s) and multiwavelength Raman data with density functional theory calculations to explore the structural and electronic properties of W,N-codoped TiO2 anatase surfaces and interpret the outstanding photocatalytic properties of such a system in partial oxidation reactions. Theoretical calculations allow us to examine several substitutional and N-interstitial configurations at different concentrations of the W,N dopants (similar to those experimentally found), as well as their interaction with structural point defects: Ti cation vacant sites and surface wolframyl species that are required to compensate the extra charge of the W6+ and N-containing anions. The joint use of theoretical and experimental XPS and Raman tools renders key structural information of W,N-codoped microcrystalline TiO2 solids. The incorporation of N at substitutional positions of anatase with the concomitant presence of W═O species introduces localized states in the band gap, a result that is critical in interpreting the chemical behavior of the solids. The combination of the electronic and geometric structural information leads to a simple mechanism that rationalizes the experimentally observed photoactivity and selectivity in partial oxidation reactions.

Agosto, 2012 | DOI: 10.1021/jp3045143

Titulo: A CFD study on the effect of the characteristic dimension of catalytic wall microreactors
Autores: Arzamendi, G; Uriz, I; Navajas, A; Dieguez, PM; Gandia, LM; Montes, M; Centeno, MA; Odriozola, JA
Revista: AlChE Journal, 58 (2012) 2785-2797
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A three-dimensional computational fluid dynamics study of the steam methane reforming (SMR) in microreactors is presented. Emphasis has been made on investigating the effects of the characteristic dimension (d: 0.35, 0.70, 1.40, and 2.80 mm) on the performance of two microreactor geometries: square microchannels and microslits. Results have shown that for both geometries the SMR conversion decreases markedly as d increases. Conversely, the microchannels provide a methane conversion slightly higher than that of the microslits. The different performance of the microreactors is only partially due to the different surface-to-volume ratio. Pronounced transverse temperature and concentration gradients develop as the characteristic dimension increases especially for microslits in the first half of the reactor. Therefore, external transport limitations can affect the performance of microreactors for SMR, although the characteristic dimensions are of the order of very few millimeters.

Agosto, 2012 | DOI: 10.1002/aic.12790

Titulo: Evidence of upconversion luminescence contribution to the improved photoactivity of erbium doped TiO2 systems
Autores: Obregon, S; Colon, G
Revista: Chemical Communications, 48 (2012) 7865-7867
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Er3+–TiO2 synthesized by a surfactant free hydrothermal method exhibits good photoactivities under sun-like excitation for the degradation of phenol. The presence of Er3+ does not affect the structural and morphological features of the TiO2 significantly. The best photocatalytic performance was attained for the samples with 2 wt% of Er. Different photocatalytic runs indicated that the incorporation of the Er3+ cation would be responsible for the enhanced photocatalytic activity, which participates in different mechanisms under UV and NIR excitation.

Julio, 2012 | DOI: 10.1039/C2CC33391K

Titulo: Effect of the active metals on the selective H-2 production in glycerol steam reforming
Autores: Araque, M; Martinez, LM; Vargas, JC; Centeno, MA; Roger, AC
Revista: Applied Catalysis B-Environmental, 125 (2012) 556-566
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The production of hydrogen by glycerol steam reforming was studied using CeZr(Co, CoRh) catalysts. The effect of Co and Rh presence on the properties of the mixed oxides and the effect on the catalytic behavior were considered. The catalysts were characterized before and after testing by XRD, Raman, TPR, H 2-TPD, TPD-TPO and HRTEM. It was observed that the presence of Co allowed the selective H 2 production related with the presence of a metallic phase at the beginning of the reaction. The presence of Rh favored even more the H 2 production and also increased the stability of the catalyst. For CeZrCoRh, the presence of both metals enhanced the catalyst reduction capacity, a characteristic that significantly improved the catalytic behavior for glycerol steam reforming. The selective H 2 production was related to the capacity of the catalyst to activate H 2O under the reaction conditions. The progressive loss of this capacity decreases the production of H 2, and glycerol decomposition is actually favored over glycerol steam reforming. According to the initial distribution of products, and its evolution with time on stream, two main reaction pathways were proposed.

Julio, 2012 | DOI: 10.1016/j.apcatb.2012.06.028

Titulo: Influence of the shape of Ni catalysts in the glycerol steam reforming
Autores: Bobadilla, L. F.; Alvarez, A.; Dominguez, M. I.; Romero-Sarria, F.; Centeno, M. A.; Montes, M.; Odriozola, J. A.
Revista: Applied Catalysis B-Environmental, 123-124 (2012) 379-390
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Biomass is an alternative to replace the use of fossil fuels. Glycerol, a byproduct in the biodiesel production, can be used for obtaining hydrogen. The most efficient method for obtaining hydrogen from glycerol is the steam reforming (SR). So far all the published papers report the use of conventional catalyst. In this paper, a structured catalyst has been prepared and compared with the conventional ones (powder and spherical pellets). Results show that the structured catalyst (monolith) is more stable as formation of coke was not observed.

Junio, 2012 | DOI: 10.1016/j.apcatb.2012.05.004

Titulo: LaNiO3 as a precursor of Ni/La2O3 for CO2 reforming of CH4: Effect of the presence of an amorphous NiO phase
Autores: Rosa Pereñiguez , Victor M. Gonzalez-delaCruz, Alfonso Caballero, Juan P. Holgado,
Revista: Applied Catalysis B-Environmental, 123-124 (2012) 324-32
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The objective of the present work has been the study of the physico-chemical and catalytic properties of Ni/La2O3 catalysts obtained by reduction of four LaNiO3 samples prepared by different methods. The LaNiO3 precursors as well as the resulting Ni/La2O3 catalysts, were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray absorption spectroscopy (XAS), temperature programmed reduction and oxidation (TPR, TPO). The catalytic performances of these systems for dry reforming of methane (DRM) were also tested. These samples show different physico-chemical properties resulting from the synthesis method used. The XAS and TPR measurements show that in all four LaNiO3 samples there is, in addition of the crystalline LaNiO3 rhombohedrical phase, a significant amount of an amorphous NiO phase, not detectable by XRD but evidenced by XAS. The amount of this NiO amorphous phase seems to play, together with some other microstructural parameters, an important role in the performance of the Ni/La2O3 samples for the DRM reaction.

Junio, 2012 | DOI: 10.1016/j.apcatb.2012.04.044

Titulo: Cu-modified cryptomelane oxide as active catalyst for CO oxidation reactions
Autores: Hernandez, Willinton Y.; Centeno, Miguel A.; Ivanova, Svetlana; Eloy, Pierre; Gaigneaux, Eric M.; Odriozola, Jose A.
Revista: Applied Catalysis B-Environmental, 123-124 (2012) 27-35
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Manganese oxide octahedral molecular sieves (cryptomelane structure) were synthesized by a solvent-free method and tested in the total oxidation of CO (TOX), and preferential oxidation of CO in presence of hydrogen (PROX). The influence of Cu in the cryptomelane structure was evaluated by several characterization techniques such as: X-ray fluorescence (XRF), thermogravimetric analysis (TGA), hydrogen temperature programmed reduction (TPR-H2) and X-ray photoelectron spectroscopy (XPS). The Cu-modified manganese oxide material (OMS-Cu) showed very high catalytic activity for CO oxidation in comparison to the bare manganese oxide octahedral molecular sieve (OMS). The improved catalytic activity observed in OMS-Cu catalyst was associated to a high lattice oxygen mobility and availability due to the formation of Cusingle bondMnsingle bondO bridges. In addition, under PROX reaction conditions the catalytic activity considerably decreases in the presence of 10% (v/v) CO2 in the feed while the same amount of water provokes an improvement in the CO conversion and O2 selectivity.

Junio, 2012 | DOI: 10.1016/j.apcatb.2012.04.024

Titulo: Sub-ambient CO oxidation over mesoporous Co3O4: Effect of morphology on its reduction behavior and catalytic performance
Autores: Alvarez, A; Ivanova, S; Centeno, MA; Odriozola, JA
Revista: Applied Catalysis A-General, 431 (2012) 9-17
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The influence of the Co 3O 4 morphology on its redox behavior and catalytic performance in the CO oxidation reaction is studied. Three different Co 3O 4 morphologies were synthesized by precipitation and hydrothermal methods. TEM and SEM observations clearly show the different obtained morphologies: rods, wires and a mixture of plates and cubes. The textural properties depend on the morphology and the redox ones on the particle size. XRD analysis reveals a spinel structure in all solids with a preferential exposition of the [1 1 0] plane in the Co 3O 4 rods sample. This preferential exposition, along with its higher specific surface area provides the rods with more efficient oxygen storage capacity resulting in an excellent catalytic performance compared to the other two morphologies.

Junio, 2012 | DOI: 10.1016/j.apcata.2012.04.006

Titulo: Oxidative Dehydrogenation of Ethanol over Au/TiO2 Photocatalysts
Autores: Sannino, Diana; Vaiano, Vincenzo; Ciambelli, Paolo; Carmen Hidalgo, M.; Murcia, Julie J.; Antonio Navio, J.
Revista: Journal of Advanced Oxidation Technologies, 15 (2012) 284-293
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Au/TiO2 photocatalysts were used in ethanol oxidative dehydrogenation. Catalysts at gold loading ranging between 0.5-2 wt.% were synthesized by photodeposition (using different deposition times: 15 and 120 min) over an own-prepared TiO2 by sol-gel method. For reference purposes, a commercial 1 wt.% Au/TiO2 catalyst (AUROlite (TM), Strem Chemicals) was also tested. Photocatalytic reactions were carried out in a gas-solid photocatalytic fluidized bed reactor. Catalytic activity depends strongly both on Au loading and on the material properties, such as particle size and distribution of metal on titania surface. Acetaldehyde was the main reaction product, with ethylene, crotonaldehyde and CO2 as by-products. An important improvement of TiO2 photoactivity was achieved for the catalyst with 0.5 wt.% gold prepared with 120 min deposition time. For an ethanol inlet concentration of 0.2 vol% at 60 degrees C, the maximum conversion and acetaldehyde selectivity were 82% and 95%, respectively. These values are considerably higher than those obtained over pristine TiO2 and over the commercial catalyst.

Junio, 2012 | DOI: ---

Titulo: Hydrothermal synthesis of BiVO4: Structural and morphological influence on the photocatalytic activity
Autores: Obregon, S; Caballero, A; Colon, G
Revista: Applied Catalysis B-Environmental, 117 (2012) 59-66
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BiVO 4 hierarchical heterostructures are synthesized by means of a surfactant free hydrothermal method having good photoactivities for the degradation of methylene blue under UV-vis irradiation. From the structural and morphological characterization it has been stated that BiVO 4 present the monoclinic crystalline phase with different morphologies depending on the pH value, type of precipitating agent and hydrothermal temperature and treatment time. The best photocatalytic performance was attained for the samples with needle-like morphology.

Abril, 2012 | DOI: 10.1016/j.apcatb.2011.12.037

Titulo: Photocatalytic activity of single and mixed nanosheet-like Bi2WO6 and TiO2 for Rhodamine B degradation under sunlike and visible illumination
Autores: Murcia-Lopez, S; Hidalgo, MC; Navio, JA
Revista: Applied Catalysis A-General, 423-424 (2012) 34-41
resumen | texto completo


The photocatalytic activity, under sunlike illumination, for Rhodamine B (RhB) degradation using Bi2WO6-TiO2 samples, is reported. Two different kinds of Bi2WO6-TiO2 samples were studied, obtained by distinct methods: first, a mechanical mixing, by adding to synthesized nanosheet-like Bi2WO6 powder the corresponding amount of TiO2 nanoparticles (P25) in order to obtain physical mixtures of both catalysts with different percentages of TiO2 (5, 10 and 50 wt%); second, a single Bi2WO6-TiO2 heterostructure was prepared by adding commercial TiO2-P25 to the Bi2WO6 precursors (50 wt%) prior to the hydrothermal treatment, thus obtaining a sample with "in situ" TiO2 incorporation. Comparisons between the photocatalytic behaviour of these samples and those exhibited by the single materials Bi2WO6 and TiO2 (P25) were carried out, in order to establish the effect not only of the TiO2 addition but also of the way in which TiO2 (P25) is incorporated. The role of each single photocatalyst in the mixtures in the RhB degradation and mineralization under sunlike and just visible illumination was also studied.

Abril, 2012 | DOI: 10.1016/j.apcata.2012.02.016

Titulo: Gold supported cryptomelane-type manganese dioxide OMS-2 nanomaterials deposited on AISI 304 stainless steels monoliths for CO oxidation
Autores: Martinez, LM; Romero-Sarria, F; Hernandez, WY; Centeno, MA; Odriozola, JA
Revista: Applied Catalysis A-General, 423 (2012) 137-145
resumen | texto completo


Gold supported on cryptomelane-type OMS-2 catalysts deposited on AISI 304 stainless steels monoliths have been prepared for the first time, characterised and tested in the CO oxidation reaction. An easy and non-conventional method of incorporation of gold to the cryptomelane solid is used. This method allows the preparation of the monolithic catalysts without altering the structural and textural characteristics of the parent OMS-2 material. Although these catalysts do not show an optimal performance for the oxidation of CO, the presence of small gold particles enhances the catalytic performances of the cryptomelane producing promissory CO oxidation catalysts. The non-conventional gold deposition favours a partial loss of K + into the channels, resulting in an increment of the average oxidation state of manganese which favours the catalytic behaviour of these kinds of materials. This study can be taken as a starting point to obtain very active gold catalysts supported on OMS-2 materials through the optimisation of the gold-support interaction and the decrease in the gold particle size.

Abril, 2012 | DOI: 10.1016/j.apcata.2012.02.026

Titulo: Study of Oxygen Reactivity in La1-x Sr (x) CoO3-delta Perovskites for Total Oxidation of Toluene
Autores: Pereniguez, R; Hueso, JL; Gaillard, F; Holgado, JP; Caballero, A
Revista: Catalysis Letters, 142 (2012) 408-416
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The total oxidation of toluene is studied over catalytic systems based on perovskite with general formula AA′CoO 3-δ (A = La, A′ = Sr). The systematic and progressive substitution of La 3+ by Sr 2+ cations in the series (La 1-xSr xCoO 3-δ system) of the perovskites have been studied to determine their influence in the final properties of these mixed oxides and their corresponding reactivity performance for the total oxidation of toluene as a model volatile organic compound with detrimental effects for health and environment. The structure and morphology of the samples before and after reaction have been characterized by XRD, BET and FE-SEM techniques. Additional experiments of temperature programmed desorption of O 2 in vacuum and reduction in H 2 were also performed to identify the main surface oxygen species and the reducibility of the different perovskites. It is remarkable that the La 1-xSr xCoO 3-δ series presents better catalytic performance for the oxidation of toluene, with lower values for the T 50 (temperature of 50 % toluene conversion) than the previously studied LaNi 1-yCoyO 3 series.

Marzo, 2012 | DOI: 10.1007/s10562-012-0799-z

Titulo: Advanced nanoarchitectures for solar photocatalytic applications
Autores: Kubacka, A; Fernandez-Garcia, M; Colon, G
Revista: Chemical Reviews, 112 (2012) 1555-1614
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Advanced nanostructured materials that demonstrate useful activity under solar excitation in fields concerned with the elimination of pollutants, partial oxidation and the valorization of chemical compounds, water splitting and CO 2 reduction processes, are discussed. Point defects present in nanoparticulated anatase present both 5-fold- and 6-fold-coordinated titanium atoms, as well as 2-fold- and 3-fold-coordinated oxygens. The requirement of using sunlight as the excitation source for the degradation reaction demands, as a principal requirement, the modification of the electronic characteristics of a UV absorber system such as anatase-TiO 2. Some reports also indicate the need for large doping concentrations for N-doping in specific cases where notable changes in the valence band onset are subsequently observed. The effect of cetyltrimethylammonium bromide (CTAB) on the crystallization is reported by Yin et al. They showed that the presence of CTAB induces the appearance of BiOBr during the synthesis at 80°C using an aqueous method.

Febrero, 2012 | DOI: 10.1021/cr100454n

Titulo: CO-Induced Morphology Changes in Zn-Modified Ceria: A FTIR Spectroscopic Study
Autores: Penkova, A; Laguna, OH; Centeno, MA; Odriozola, JA
Revista: Journal of Physical Chemistry C, 116 (2012) 5747-5756
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A FTIR study of the CO adsorption on a Zn-modified ceria is presented. The results indicate that at lower activation temperatures only Ce 4+ carbonyls were detected, which were reduced with the increase of the activation temperature. At higher activation temperatures, up to three Zn 2+ carbonyls were also identified according to the arrangement of the Zn 2+ cations. The consecutive CO adsorptions demonstrated an irreversible modification of the surface, resulting in an agglomeration of the zinc cations. A stepwise conversion of the isolated Zn 2+ carbonyls into carbonyls of the closely situated zinc cations followed by formation of bigger zinc oxide clusters was observed. The carbon monoxide coordinated on the isolated Zn 2+ cations at the interface with ceria reacts with the lattice oxygen leading to formation of oxygen vacancies. An insight into the origin of the activation during the CO oxidation process is proposed.

Febrero, 2012 | DOI: 10.1021/jp210996b

Titulo: Sub-ambient CO oxidation over Au/MOx/CeO2-Al2O3 (M = Zn or Fe)
Autores: Reina, TR; Ivanova, S; Dominguez, MI; Centeno, MA; Odriozola, JA
Revista: Applied Catalysis A-General, 419-420 (2012) 58-66
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A series of ZnO and Fe 2O 3 modified ceria/alumina supports and their corresponding gold catalyst were prepared and studied in the CO oxidation reaction. ZnO-doped solids show a superior catalytic activity compared to the bare CeO 2-Al 2O 3, which is attributed to the intimate contact of the ZnO and CeO 2 phases, since an exchange of the lattice oxygen occurs at the interface. In a similar way, Fe 2O 3-modified supports increase the ability of the CeO 2-Al 2O 3 solids to eliminate CO caused by both the existence of Ce-Fe contact surface and the Fe 2O 3 intrinsic activity. All of the gold catalysts were very efficient in oxidising CO irrespective of the doping metal oxide or loading, with the ZnO containing systems better than the others. The majority of the systems reached total CO conversion below room temperature with the ZnO and Fe 2O 3 monolayer loaded systems the most efficient within the series.

Febrero, 2012 | DOI: 10.1016/j.apcata.2012.01.012

Titulo: Nanostructured Spark Plasma Sintered Ce-TZP Ceramics
Autores: Cruz, SA; Poyato, R; Cumbrera, FL; Odriozola, JA
Revista: Journal of the American Ceramic Society, 95 (2012) 901-906
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In this work, spark plasma sintering (SPS) of 10 mol% CeO 2-doped ZrO 2 nanocrystalline powders, obtained by a two-step synthesis procedure, allows the preparation of fully densified nanostructured ceramics. The CeO 2-ZrO 2 powders with particle size below 100 nm are obtained after CeO 2 deposition on hydrothermally synthesized ZrO 2 particles by the impregnation method. Tetragonal CeO 2-ZrO 2 ceramics are obtained when sintering at 1200°C without holding time. A graded material containing tetragonal, monoclinic, and pyrochlore phases are obtained when sintering at 1200°C and for 5 min holding time. This is explained in terms of the gradual reduction of Ce 4+ to Ce 3+ species by carbon in the graphite environment during SPS. With the successful combination of the stabilizer coating technique and SPS, we achieve not only the stabilization of the tetragonal phase in the ceramics, but also good control of the grain size, by producing nanostructured ceramics with 40-70 nm grain sizes.

Febrero, 2012 | DOI: 10.1111/j.1551-2916.2011.04978.x

Titulo: In Situ XAS Study of Synergic Effects on Ni-Co/ZrO2 Methane Reforming Catalysts
Autores: Gonzalez-delaCruz, VM; Pereniguez, R; Ternero, F; Holgado, JP; Caballero, A
Revista: Journal of Physical Chemistry C, 116 (2012) 2919-2926
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Four different mono and bimetallic Ni–Co/ZrO2 catalysts have been studied by means of in situ XAS, X-ray diffraction, TPR, and measurements of the catalytic activity in the dry reforming reaction of methane (DRM). Even though the cobalt monometallic system has no activity for the methane reforming reaction, both bimetallic catalysts (with 1:1 and 1:2 Ni/Co ratio, respectively), showed a better activity and stability than the nickel monometallic system. The XRD data indicate that a mixed cobalt–nickel spinel is formed by calcination of the precursor solids, leading to the formation of an alloy of both metals after reduction in hydrogen. In situ XAS experiments showed a much better resistance of metals in the bimetallic systems to be oxidized under reaction conditions at temperatures until 750 °C. After these results, we proposed the formation in the bimetallic systems of a more reducible nickel–cobalt alloy phase, which remains completely metallic in contact with the CO2/CH4 reaction mixture at any temperature. The presence of adjacent nickel and cobalt sites seems to avoid the deactivation of cobalt in the DRM reaction. In the case of cobalt sites, the presence of adjacent nickel atoms seems to prevent the deposition of carbon over the cobalt sites, now showing its higher activity in the dry reforming reaction. Simultaneously, this higher activity of the cobalt sites in the bimetallic system produces more hydrogen as a product, maintaining the nickel atoms completely reduced under reaction conditions. This synergic effect accounts for the better performance of the bimetallic systems and points at both, the oxidation state of nickel particles under reaction conditions and the carbon deposition processes, as important factors responsible for differences in catalytic activities and stabilities in this hydrocarbon reaction.

Enero, 2012 | DOI: 10.1021/jp2092048

Titulo: Operando DRIFTS study of the redox and catalytic properties of CuO/Ce1−xTbxO2−δ (x = 0–0.5) catalysts: evidence of an induction step during CO oxidation
Autores: Martinez-Arias, A.; Hungria, A. B.; Fernandez-Garcia, M.; Iglesias-Juez, A.; Soria, J.; Conesa, J. C.; Anderson, J. A.; Munuera, G.
Revista: Physical Chemistry Chemical Physics, 14 (2012) 2144-2151
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Catalysts of 1 wt% copper oxide supported on cerium oxide or cerium–terbium mixed oxides are comparatively examined with respect to their redox and catalytic properties for CO oxidation. Characterization of the catalysts had shown that they contain highly dispersed CuO-type entities on the corresponding nanostructured fluorite supports with copper dispersion increasing with increasing amounts of terbium in the support. In contrast, the CO oxidation catalytic activity decreases with increasing amounts of terbium in the support. On the basis of operando-DRIFTS experiments, one of the factors that could explain such behaviour is related to the greater difficulty in generating reduced copper sites active for the reaction in the presence of terbium, which in turn is evidenced to constitute an induction stage. Analysis of the redox properties is complemented by XPS which confirms the greater resistance to copper reduction in the presence of terbium.

Enero, 2012 | DOI: 10.1039/C1CP23298C

Titulo: Rapid microwave-assisted synthesis of one-dimensional silver–H2Ti3O7 nanotubes
Autores: Rodriguez-Gonzalez, V; Obregon-Alfaro, S; Lozano-Sanchez, LM; Lee, SW
Revista: Journal of Molecular Catalysis A-Chemical, 353 (2012) 163-170
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The formation of silver hydrogen trititanate nanotubes, based on the controllable microwave-assisted hydrothermal nanocrystalline TiO2 transition, was investigated by means of XRD, UV–vis–DRS, Raman, FESEM and HRTEM. The results show that the rapid formation of H-trititanate nanotubes is achieved by self-assemblage of silver nanoparticles in which the lamellar intermediates react with NaOH in hydrothermal conditions. The presence of Ag° nanoparticles in the precursor promotes rapid and more complete formation of layered H2Ti3O7 nanotubes. After reacting for 4 h without subsequent thermal treatment, the inner diameters of the cylinder-like nanotubes are in the range of 3.6–4.0 nm, while their outer diameters are in the range of 7.6–8 nm. In addition, some straight nanotubes form bundles which are hundreds of nanometers in length. As-synthesized ultrathin nanotubes and crystalline precursors were evaluated by methyl orange dye (MOD) UV photo-oxidation. The complete degradation of MOD is achieved after 3.5 h of UV irradiation in the presence of silver–TiO2 nanocomposites, resulting in 50% of dye mineralization.

Enero, 2012 | DOI: 10.1016/j.molcata.2011.11.020

Titulo: Effect of hydrothermal treatment on structural and photocatalytic properties of TiO2 synthesized by sol-gel method
Autores: Melian, EP; Diaz, OG; Rodriguez, JMD; Colon, G; Navio, JA; Pena, JP
Revista: Applied Catalysis A-General, 411 (2012) 153-159
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TiO 2 nanoparticles have been prepared by sol-gel precipitation and further hydrothermal treatment. In this way, the effect of the hydrothermal treatment on the structural properties and photocatalytic activity of sol-gel synthesized catalysts has been investigated. These catalysts have been produced by hydrolysis of a mixture of isopropanol-titanium tetraisopropoxide (iPrOH-TiiP). The prepared photocatalysts were characterized by means of X-ray diffraction (XRD), surface area analysis (BET), transmission microscopy (TEM), thermogravimetric analysis (TG), scanning electron microscopy (SEM) analysis, diffuse reflectance, sedimentability analysis and aggregate size study. Besides, the structural evolution with the temperature of the photocatalysts treated or not hydrothermally was studied. It was observed that the calcination produces approaching between the characteristics of both sets of photocatalysts. The photocatalytic activity of the obtained photocatalysts was investigated, using phenol as a model pollutant. The calcination temperature is the most remarkable factor that can affect the ultimate photocatalytic activity of the prepared photocatalysts. However, the hydrothermal treatment previous to calcination led to obtain photocatalysts which exhibit larger photocatalytic activity than their homologous photocatalysts without hydrothermal treatment. The obtained photocatalyst TiO 2ht600 exhibits the same photocatalytic activity per surface area than the commercial TiO 2 Degussa P25 but with much faster sedimentability.

Diciembre, 2011 | DOI: 10.1016/j.apcata.2011.10.033

Titulo: Mechanism of complete n-hexane oxidation on silica supported cobalt and manganese catalysts
Autores: Todorova, S; Naydenov, A; Kolev, H; Holgado, JP; Ivanov, G; Kadinov, G; Caballero, A
Revista: Applied Catalysis A-General, 413-414 (2012) 43-51
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Mono- and bi-component cobalt and manganese samples were prepared by impregnation of silica with aqueous solutions of Co(NO3)2·6H2O and/or Mn(NO3)2·6H2O. The bi-component samples were obtained by a common solution of Co- and Mn nitrates (CoMn-MS) or by deposition of cobalt on calcined Mn sample (Co + Mn). The catalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), temperature programmed reduction (TPR), Fourier transformed infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), elemental analysis and tested in reaction of complete n-hexane oxidation. It was observed that the well crystalline cobalt oxide partially covers poorly crystalline manganese oxide in the Co + Mn catalysts, while finely divided oxides (MnO2 and Mn2O3, Co3O4) are present on the surface of the (CoMn-MS) sample. Four Langmuir–Hinshelwood and two Mars–van Krevelen models were fitted with the experimental data from the catalytic tests. According to the model calculations and results from instrumental methods, the reaction pathway over single component manganese and bi-component Co-Mn catalysts proceeds through Mars–van Krevelen mechanism (the oxidation of the catalyst surface being the rate determining step), while Langmuir–Hinshelwood mechanism is more probable for the Co sample. A considerable increase in activity for the sample obtained from a mixed solution is explained by low crystallinity, simultaneous presence of Mn4+–Mn3+ and enrichment of the surface in oxygen species.

Diciembre, 2011 | DOI: 10.1016/j.apcata.2011.10.041

Titulo: Redox and catalytic properties of CuO/CeO2 under CO + O2 + NO: Promoting effect of NO on CO oxidation
Autores: Martinez-Arias, A.; Hungria, A. B.; Iglesias-Juez, A.; Fernandez-Garcia, M.; Anderson, J. A.; Conesa, J. C.; Munuera, G.; Soria, J.
Revista: Catalysis Today, 180 (2012) 81-87
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A CuO/CeO2 catalyst has been studied with respect to its catalytic activity for CO oxidation under stoichiometric conditions employing either O2 or O2–NO mixture as oxidants. The obtained results are rationalised on the basis of analysis of redox properties upon interaction with CO and O2–NO by EPR as well as by redox/catalytic analysis by operando-DRIFTS. These provide useful insight into the processes involved during NO reduction, for which two well differentiated steps associated to a change in the type of active centres during the course of the reaction are evidenced. Nevertheless, the most interesting result is related to observation of a novel promoting effect of NO on CO oxidation. This is explained mainly on the basis of DRIFTS results and appears to be associated with phenomena of adsorption/desorption of NOx species at interfacial positions which apparently activate such interfacial region allowing formation of greater amounts of active reduced copper centres in the presence of NO.

Diciembre, 2011 | DOI: 10.1016/j.cattod.2011.02.014

Titulo: Preferential oxidation of CO (CO-PROX) over CuOx/CeO2 coated microchannel reactor
Autores: Laguna, OH; Ngassa, EM; Oraa, S; Alvarez, A; Dominguez, MI; Romero-Sarria, F; Arzamendi, G; Gandia, LM; Centeno, MA; Odriozola, JA
Revista: Catalysis Today, 180 (2012) 105-110
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The general aspects of the synthesis and characterization results of a CuO x/CeO 2 catalyst were presented. In addition the principal steps for manufacturing a microchannel reactor and for the coating of the CuO x/CeO 2 catalyst onto the microchannels walls, were also summarized. The catalytic activity of this microchannel reactor during the preferential oxidation of CO (CO-PROX) was evaluated employing a feed-stream that simulates a reformate off-gas after the WGS unit. Two activation atmospheres were studied (H 2/N 2 and O 2/N 2). The reducing pretreatment improved the resistance to deactivation by formation of carbonaceous species over the catalyst surface at high temperatures. The presence of H 2O and CO 2 in the feed-stream was also analyzed indicating that the adsorption of CO 2 inhibited the conversion of CO at lower temperatures because these compounds modified the active sites through the formation of carbonaceous species on the catalyst surface. Finally, the experimental results of the microreactor performance were compared with CFD simulations that were carried out using a kinetic for the CuO x/CeO 2 powder catalyst. The experimental results were reasonably well described by the model, thus confirming its validity.

Diciembre, 2011 | DOI: 10.1016/j.cattod.2011.03.024

Titulo: DRIFTS study of methanol adsorption on Mg-Al hydrotalcite catalysts for the transesterification of vegetable oils
Autores: Navajas, A; Arzamendi, G; Romero-Sarria, F; Centeno, MA; Odriozola, JA; Gandia, LM
Revista: Catalysis Communications, 7 (2012) 189-193
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Mg-Al hydrotalcites rehydrated after calcination are promising catalysts for the methanolysis of vegetable oils. To gain insight into the basis of their catalytic action, the adsorption of methanol over some commercial Mg-Al hydrotalcites was studied by diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). Different species formed after methanol adsorption were identified, being the total quantity of methoxy species related to the basic character of the sample. A linear correlation between the amount of adsorbed monodentate methoxy species and the catalytic activity in the biodiesel production was found. Therefore, it is proposed that these species are the mainly involved in the transesterification reaction.

Diciembre, 2011 | DOI: 10.1016/j.catcom.2011.11.005

Titulo: Photocatalytic Ethanol Oxidative Dehydrogenation over Pt/TiO2: Effect of the Addition of Blue Phosphors
Autores: Murcia, JJ; Hidalgo, MC; Navio, JA; Vaiano, V; Ciambelli, P; Sannino, D
Revista: International Journal of Photoenergy, 2012 (2012) 687262
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Ethanol oxidative dehydrogenation over Pt/TiO2 photocatalyst, in the presence and absence of blue phosphors, was performed. The catalyst was prepared by photodeposition of Pt on sulphated TiO2. This material was tested in a gas-solid photocatalytic fluidized bed reactor at high illumination efficiency. The effect of the addition of blue phosphors into the fluidized bed has been evaluated. The synthesized catalysts were extensively characterized by different techniques. Pt/TiO2 with a loading of 0.5 wt% of Pt appeared to be an active photocatalyst in the selective partial oxidation of ethanol to acetaldehyde improving its activity and selectivity compared to pure TiO2. In the same way, a notable enhancement of ethanol conversion in the presence of the blue phosphors has been obtained. The blue phosphors produced an increase in the level of ethanol conversion over the Pt/TiO2 catalyst, keeping at the same time the high selectivity to acetaldehyde.

Diciembre, 2011 | DOI: 10.1155/2012/687262

2011


Titulo: Well-defined negatively charged gold carbonyls on Au/SiO2
Autores: Chakarova, K., Mihaylov, M., Ivanova, S., Centeno, M.A., Hadjiivanov, K.
Revista: Journal of Physical Chemistry C, 115 (2011) 21273-21282
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A Au/SiO2 sample was prepared by ammonia-assisted grafting using HAuCl4 as a gold precursor. Gold on the sample evacuated at 673 K is essentially in metallic form: adsorption of CO at 100 K results in formation of Au0-CO species (IR band at 2122 cm-1 shifting to 2103 cm-1 at high coverage). Coadsorption of CO and O2 even at ambient temperature leads to creation of Auδ+ sites and oxidation of CO. On the contrary, increase of the contact time between CO and the sample leads to a gradual reduction of Au0 to Au δ- species. The process is slightly favored by the presence of water and strongly enhanced in the presence of hydrogen. Back oxidation of Auδ- to Au0 and to Auδ+ occurs in the presence of oxygen. The Auδ- sites strongly adsorb CO and form different interconverting carbonyls observed in the 2080-2050 cm -1 region. On the basis of adsorption of CO-13CO and CO-13C18O isotopic mixtures, it is concluded that all Auδ--CO species are linear, and probably ordered structures are formed. Intensity transfer phenomena are nicely monitored during adsorption of CO isotopic mixtures. The eventual role of negatively charged gold in catalysis is discussed.

Octubre, 2011 | DOI: 10.1021/jp2070562

Titulo: Influence of the strong metal support interaction effect (SMSI) of Pt/TiO(2) and Pd/TiO(2) systems in the photocatalytic biohydrogen production from glucose solution
Autores: Colmenares, JC; Magdziarz, A; Aramendia, MA; Marinas, A; Marinas, JM; Urbano, FJ; Navio, JA
Revista: Catalysis Communications, 16 (2011) 1-6
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Two different catalysts consisting of Pt/TiO2 and Pd/TiO 2 were submitted to diverse oxidative and reductive calcination treatments and tested for photocatalytic reforming of glucose water solution (as a model of biomass component) in H2 production. Oxidation and reduction at 850°C resulted in better photocatalysts for hydrogen production than Degussa P-25 and the ones prepared at 500°C, despite the fact that the former consisted in very low surface area (6-8 m2/g) rutile titania specimens. The platinum-containing systems prepared at 850°C give the most effective catalysts. XPS characterization of the systems showed that thermal treatment at 850°C resulted in electron transfer from titania to metal particles through the so-called strong metal-support interaction (SMSI) effect. Furthermore, the greater the SMSI effect, the better the catalytic performance. Improvement in photocatalytic behavior is explained in terms of avoidance of electron-hole recombination through the electron transfer from titania to metal particles.

Octubre, 2011 | DOI: 10.1016/j.catcom.2011.09.003

Titulo: Structural and catalytic properties of lanthanide (La, Eu, Gd) doped ceria
Autores: Hernandez, WY; Laguna, OH; Centeno, MA; Odriozola, JA
Revista: Journal of Solid State Chemistry, 184 (2011) 3014-3020
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Ce0.9M0.1O2-δ mixed oxides (M=La, Eu and Gd) were synthesized by coprecipitation. Independent of the dopant cation, the obtained solids maintain the F-type crystalline structure, characteristic of CeO2 (fluorite structure) without phase segregation. The ceria lattice expands depending on the ionic radii of the dopant cation, as indicated by X-ray diffraction studies. This effect also agrees with the observed shift of the F2g Raman vibrational mode. The presence of the dopant cations in the ceria lattice increases the concentration of structural oxygen vacancies and the reducibility of the redox pair Ce4/Ce3. All synthesized materials show higher catalytic activity for the CO oxidation reaction than that of bare CeO2, being Eu-doped solid the one with the best catalytic performances despite of its lower surface area.

Octubre, 2011 | DOI: 10.1016/j.jssc.2011.09.018

Titulo: CO oxidation at low temperature on Au/CePO4: Mechanistic aspects
Autores: Romero-Sarria, F., Domínguez, M.I., Centeno, M.A., Odriozola, J.A.
Revista: Applied Catalysis B: Environmental, 107 (2011), 268-273
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This work reports the synthesis and characterization of a cerium phosphate supported gold catalyst as well as its catalytic activity for the oxidation of CO. A precipitation method in the presence of an organic modifier followed by a hydrothermal treatment was used for the support synthesis, resulting in high surface area nanometric particles. Gold/cerium phosphate catalyst with a 1% (w/w) nominal gold content was characterized using XRF, XRD, N2 adsorption-desorption measurements, TEM and DRIFTS-MS. The catalyst shows good catalytic activity at low temperature. The activity is related to the generation of oxygen vacancies in the support caused by the elimination of structural oxygen. In situ studies revealed that the reaction of the oxygen vacancies with gaseous oxygen resulted in the formation of peroxo species. These species are responsible for the activity detected at room temperature in both the catalyst and the support. Moreover, the presence of carbonate and hydrogen carbonate acting as reaction intermediates have been observed.

Agosto, 2011 | DOI: 10.1016/j.apcatb.2011.07.022

Titulo: Synthesis, characterization and photocatalytic activity of Bi-doped TiO2 photocatalysts under simulated solar irradiation
Autores: Murcia-López, S., Hidalgo, M.C., Navío, J.A.
Revista: Applied Catalysis A: General, 404 (2011) 59-67
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A series of Bi3+-doped TiO2 catalysts with a doping concentration up to 2 wt% were prepared by a sol-gel hydrothermal method. The prepared photocatalysts were characterized by different techniques to determine their structure, morphology and light absorption properties. The activities were evaluated in the photocatalytic oxidation of phenol in aqueous solution under UV-vis illumination. The experimental results indicate that the presence of Bi3+ in TiO2 catalysts enhances the photocatalytic reaction of phenol degradation, although the efficiency of the process markedly depends on the nominal content of the Bi3+ and on the calcination temperature. It was found that the optimal dosage of 0.5 wt% Bi3+ in TiO2 and calcinations at 600 °C 4 h achieved the fastest reaction of phenol degradation under the experimental conditions. From the comparison of the initial rates of the photocatalytic degradation of phenol between home prepared undoped and Bi3+-doped TiO2 with commercial TiO2 Degussa P25, it can be inferred that home prepared TiO 2 calcined at temperatures above 500 °C clearly exceed the photocatalytic performance of P25. When bismuth is incorporated, the reaction rate values are even higher, especially at 600 °C. Even when Bi 3+-doped TiO2 (0.5 wt% Bi3+) calcined at 600 °C has almost the same BET surface than P25, its activity is better. In particular, the reaction rate for the sample with a 0.5% mass content of Bi 3+ calcined at 600 °C not only present higher value with respect to the other series but also a degree of mineralization close to 100%.

Agosto, 2011 | DOI: 10.1016/j.apcata.2011.07.008

Titulo: Fe-doped ceria solids synthesized by the microemulsion method for CO oxidation reactions
Autores: O.H. Laguna, M.A. Centeno, M. Boutonnet, J.A. Odriozola
Revista: Applied Catalysis B: Environmental, 106 (2011) 621-629
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A series of Ce-Fe mixed oxides as well as the pure oxides were synthesized by the microemulsions method. The solid solution formation was established for all the Fe-doped systems and only a hardly noticeable segregation of &#945;-Fe2O3 was appreciated for the solid with the maximum iron content (50at.% Fe). The oxygen exchange is improved for all the Fe-doped systems; however the 10at.% Fe appears as the optimal iron content for achieving the maximum oxygen vacancies concentration and the higher reducibility efficiency. The CO oxidation (TOX, PROX) is especially achieved for the solids with the lower iron contents but with a superior oxygen vacancies proportion. These Ce-Fe systems prepared from microemulsions are very attractive to be considered as supports for depositing active phases capable of enhancing oxygen exchange ability of the whole system, allowing higher CO oxidation abilities.

Julio, 2011 | DOI: 10.1016/j.apcatb.2011.06.025

Titulo: Oxidation of CO over gold supported on Zn-modified ceria catalysts
Autores: Laguna, O.H., Centeno, M.A., Romero-Sarria, F., Odriozola, J.A.
Revista: Catalysis Today, 172 (2011) 118-123
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A series of Zn-modified ceria solids were prepared by thermal decomposition of the corresponding metal propionates. The formation of segregated ZnO particles on the ceria surface is evidenced for these solids using X-ray diffraction; in addition to this the characterization data may allow discarding the formation of a ZnO-CeO2 solid solution. On modifying with Zn, the reducibility of the ceria support is enhanced, being the highest reducibility the one obtained for the ZnO-CeO2 solid having a 1:9 Zn:Ce atomic ratio (CeZn10). The activity of this solid in the CO oxidation reaction was the highest among the tested Zn-modified ceria solids. Therefore, catalysts containing 1 wt.% gold, supported on pure ceria and CeZn solids, were prepared, characterized and their catalytic activities tested. The Zn-modified gold catalyst is more active than the un-modified Au/CeO2 catalyst in the oxidation of CO; this behavior is related to the higher metallic dispersion of gold on the CeZn support surface. However, the number of oxygen vacancies acting as nucleation sites for gold, is hardly modified in the Zn-modified ceria support and, therefore, the higher gold dispersion must be related to high electron density sites on the catalyst surface as a result of Au-Ce-Zn interaction, this improved gold dispersion results in higher activities for CO oxidation.

Julio, 2011 | DOI: 10.1016/j.cattod.2011.02.015

Titulo: Ionic liquid protected heteropoly acids for methanol dehydration
Autores: Ivanova, S., Nitsch, X., Romero-Sarria, F., Louis, B., Centeno, M.A., Roger, A.C., Odriozola, J.A.
Revista: Catalysis Today, 171 (2011) 236-241
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We report herein the synthesis of an organic-inorganic hybrid composed by the ionic liquid protected Keggin structure, as a precursor for acid catalyst and its subsequent application in the methanol dehydration reaction. Special attention was paid to the thermal stability of the resulted hybrids as a function of the Keggin anion. The catalytic behaviour of these new materials are also studied and compared to the metal salt Cs2HPW 12O40. The prepared hybrids are less thermally stable than the metal salt, but their partial decomposition results in very active and selective catalysts for the dehydration of methanol to dimethyl ether.

Julio, 2011 | DOI: 10.1016/j.cattod.2011.03.077

Titulo: High-stable mesoporous Ni-Ce/clay catalysts for syngas production
Autores: Daza, C.E., Gamba, O.A., Hernández, Y., Centeno, M.A., Mondragón, F., Moreno, S., Molina, R.
Revista: Catalysis Letters, 141 (2011) 1037-1046
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A mesoporous-type catalytic support was synthesized through the modification of a smectite with polyvinyl alcohol (PVA) and microwaves. Texture and micro-morphology of the support was determined. Several techniques were employed in order to describe the chemical environment of active species on the surface. Ni0 particle sizes were dependent on the structural site of reducible species. High stable Ni-Ce catalysts (calcined at 800 °C) were evaluated in the CO2 reforming of methane reaction at 700 °C (WHSV = 96 L g-1 h-1, without dilution gas and pre-reduction). The catalysts have presented CH4 conversions between 40 and 65%, CO2 conversion between 35 and 65% and H2/CO ratios between 0.2 and 0.4.

Junio, 2011 | DOI: 10.1007/s10562-011-0579-1

Titulo: Photocatalytic coatings of silver–TiO2 nanocomposites on foamed waste-glass prepared by sonochemical process
Autores: Lee, S.W., Obregón-Alfaro, S., Rodríguez-González, V.
Revista: Journal of Photochemistry and Photobiology A: Chemistry, 221 (2011) 71-76
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Silver-TiO2 nanocomposite was prepared by photodeposition of silver nanoparticles on the surface of titanium dioxide. The sonochemical method was used for the deposition of silver-TiO2 powder on commercial foamed waste-glass strips (FWGS). The silver-TiO2 and the coated FWGS was characterized by XRD, DRS, SEM, TEM and nitrogen adsorption. In order to enhance silver-TiO2 deposition, different parameters were evaluated such as the solvent effect and use of stabilizing agents. The best deposition was obtained with an aqueous solution of polyvinyl alcohol (PVA) and an ultrasound irradiation source of 23.3 kHz. The photocatalytic activity of the silver-TiO2 coated FWGS was evaluated in the UV photo-assisted destruction of the noxious microalgae, Tetraselmis suecica. It was found that after the photocatalytic irradiation, for 180 min, the algae cells were deformed, fragmented and annihilated, thereby avoiding its regeneration.2

Mayo, 2011 | DOI: 10.1016/j.jphotochem.2011.04.026

Titulo: Photodeposition of gold on titanium dioxide for photocatalytic phenol oxidation
Autores: Hidalgo, MC; Murcia, JJ; Navio, JA; Colon, G
Revista: Applied Catalysis A-General, 397 (2011) 112-120
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The influence of experimental conditions during the photodeposition in the preparation of supported Au on TiO2 has been studied. Besides preparation pH, light intensity and deposition time showed to have a high influence on the final properties of gold deposits. Photodeposition using illumination with a high light intensity UV-vis lamp (140 W/m2 UVA range) resulted to be an ineffective method for obtaining nanoparticles of gold on the titania, producing very large and poorly distributed gold deposits. Thus obtained materials did not show any important improvement of their photocatalytic activity tested for phenol oxidation. By contrast, photodeposition using a low light intensity of illumination (0.15 W/m 2 UVA range), produced materials with notably improved photocatalytic activity. The illumination with such a low light intensity allowed the control of the amount, aggregation and oxidation state of gold by changing deposition time, enabling a feasible method of tailoring Au-TiO2 with the appropriate properties for a high photocatalytic activity. Best photocatalytic behaviour for phenol photodegradation was obtained for Au-TiO2 samples prepared by photodeposition at low light intensity with 120 min photodeposition time for catalysts with a 0.5% and 1% nominal content of gold and with 60 min photodeposition time for catalyst with a 2% nominal content of gold.

Marzo, 2011 | DOI: 10.1016/j.apcata.2011.02.030

Titulo: Selective CO removal over Au/CeFe and CeCu catalysts in microreactors studied through kinetic analysis and CFD simulations
Autores: Arzamendi, G; Uriz, I; Dieguez, PM; Laguna, OH; Hernandez, WV; Alvarez, A; Centeno, MA; Odriozola, JA; Montes, M; Gandia, LM
Revista: Chemical Engineering Journal, 167 (2011) 588-596
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A kinetic study of the preferential oxidation of CO in H2 rich streams (CO-PrOx) over a cerium-copper oxide (CeCu) and a gold catalyst supported on cerium-iron oxide (Au/CeFe) is presented. The gold catalyst is very active but the CeCu oxide is more selective. A kinetic model describing the CO-PrOx system with CO2 and H2O in the feed has been formulated considering the oxidation of CO and H2 and the reverse water-gas shift reaction. The rate equations have been implemented in computational fluid dynamics codes to study the influence of the operating variables on the CO-PrOx in microchannels and microslits. The CeCu catalyst is the only one capable of achieving final CO contents below 10-100ppmv. Due to the opposite effect of temperature on activity and selectivity there is an optimal temperature at which the CO content is minimal over CeCu. This temperature varies between 170 and 200°C as the GHSV increases from 10,000 to 50,000h-1. Simulations have evidenced the very good heat transfer performance of the microdevices showing that the CO-PrOx temperature can be controlled using air as cooling fluid although the inlet temperature and flow rate should be carefully controlled to avoid reaction extinction. Both microchannels and microslits behaved similarly. The fact that the microslits are much easier to fabricate may be an interesting advantage in favour of that geometry in this case. © 2010 Elsevier B.V.

Febrero, 2011 | DOI: 10.1016/j.cej.2010.08.083

Titulo: Design and testing of a microchannel reactor for the PROX reaction
Autores: Cruz, S; Sanz, O; Poyato, R; Laguna, OH; Echave, FJ; Almeida, LC; Centeno, MA; Arzamendi, G; Gandia, LM; Souza-Aguiar, EF; Montes, M; Odriozola, JA
Revista: Chemical Engineering Journal, 167 (2011) 634-642
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The different steps for manufacturing a microchannel reactor for the PROX reaction are discussed. Transient Liquid Phase bonding (TLP) using a Ni-B-Si amorphous melt spun is used for joining micromilled Al-alloyed ferritic stainless steel plates followed by recrystallization at 1200°C for 5h. A CuOx-CeO2 catalyst synthesized by the coprecipitation method was washcoated on the microchannel block resulting in a homogenous 20-30μm thick layer. The catalytic activity for CO-PROX reaction is similar in both the powder catalyst and the microchannel coated reactor but the selectivity is higher in the microchannel reactor. © 2010 Elsevier B.V.

Febrero, 2011 | DOI: 10.1016/j.cej.2010.08.088

Titulo: Fischer-Tropsch synthesis in microchannels
Autores: Almeida, LC; Echave, FJ; Sanz, O; Centeno, MA; Arzamendi, G; Gandia, LM; Sousa-Aguiar, EF; Odriozola, JA; Montes, M
Revista: Chemical Engineering Journal, 167 (2011) 536-544
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Different metallic supports (aluminum foams of 40ppi, honeycomb monolith and micromonolith of 350 and 1180cpsi, respectively) have been loaded with a 20%Co-0.5%Re/γ-Al2O3 catalyst by the washcoating method. Layers of different thicknesses have been deposited onto the metallic supports. The catalytic coatings were characterized measuring their textural properties, adhesion and morphology. These structured catalysts have been tested in the Fischer-Tropsch synthesis (FTS) and compared with a microchannel block presenting perpendicular channels for reaction and cooling. The selectivity depends on the type of support used and mainly on the thickness of the layer deposited. In general, the C5+ selectivity decreased at increasing CO conversion for all of the systems (powder, monoliths, foams and microchannels block). On the other hand, the selectivity to methane increased with the thickness of the catalytic layer due to the higher effective H2/CO ratio over the active sites resulting from the higher diffusivity of H2 compared with CO in the liquid products filling the pores. The C5+ selectivity of the microchannels reactor is higher than that of the structured supports and the powder catalyst. © 2010 Elsevier B.V.

Febrero, 2011 | DOI: 10.1016/j.cej.2010.09.091

Titulo: Gold nanoparticles on yttrium modified titania: Support properties and catalytic activity
Autores: Plata, JJ; Marquez, AM; Sanz, JF; Avellaneda, RS; Romero-Sarria, F; Dominguez, MI; Centeno, MA; Odriozola, JA
Revista: Topics in Catalysis, 54 (2011) 219-228
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A series of titanium oxide catalysts modified with yttrium has been prepared by sol-gel method and their structural properties have been studied. The incorporation of yttrium in the titania lattice favors the formation of oxygen vacancies while at low Y loadings the anatase structure is preserved. The catalytic activity of these solids for CO oxidation is found to be significantly dependent on their physical properties. In particular the amount of dopant controls the number of surface oxygen vacancies created as well as the gold particle size, which directly affects the catalytic activity. Also, a linear relationship between the catalytic activity and the band gap values, which depend on the Y loading, is observed. Density functional theory based calculations show that Y atoms are incorporated at the TiO2 surface at substitutional positions only, while the preferred oxygen vacancies arise by removing the bridge surface oxygen atoms. These O-vacancies are the preferential adsorption sites for Au atoms and nanoparticles, acting as nucleation centers that favor the dispersion of the catalyst active phase over the support surface. In agreement with experiment, Y doping is found to decrease the band gap of the support due to a destabilization of the valence band of the oxide. © 2011 Springer Science+Business Media, LLC 2011.

Febrero, 2011 | DOI: 10.1007/s11244-011-9639-4

Titulo: Effect of thermal treatments on the catalytic behaviour in the CO preferential oxidation of a CuO-CeO2-ZrO2 catalyst with a flower-like morphology
Autores: Moretti, E; Storaro, L; Talon, A; Lenarda, M; Riello, P; Frattini, R; de Yuso, MDM; Jimenez-Lopez, A; Rodriguez-Castellon, E; Ternero, F; Caballero, A; Holgado, JP
Revista: Applied Catalysis B-Environmental, 102 (2011) 627-637
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A Ce–Zr–Cu oxide system with a flower-like morphology was prepared by a slow co-precipitation method in the absence of any structure directing agent. Four portions of the oxide were thermally treated at four different temperatures (350 °C, 450 °C, 550 °C, 650 °C). The resulting materials samples were characterized by quantitative XRD, adsorption–desorption of N2 at-196 °C, SEM and TEM microscopy, –H2-TPR, XPS and Operando-XANES. All samples were tested in the preferential CO oxidation (CO-PROX) in the 40–190 °C temperature range. Thermal treatments were found to induce slight structural changes without altering the starting morphology of the samples. The samples treated at higher temperature 550–650 °C showed a quite interesting CO-PROX activity and selectivity in a temperature range suitable for a practical use within the FEMFC technology.

Enero, 2011 | DOI: 10.1016/j.apcatb.2011.01.004

Titulo: Modifying the Size of Nickel Metallic Particles by H2/CO Treatment in Ni/ZrO2 Methane Dry Reforming Catalysts
Autores: Gonzalez-Delacruz, VM; Pereñiguez, R; Ternero, F; Holgado, JP; Caballero, A
Revista: ACS Catalysis, 1 (2011) 82-88
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The effect of a reduction process with CO or H-2 on the Size of nickel particles in Ni/ZrO2 dry methane reforming catalysts have been studied by means of in situ X-ray Spectroscopy (XAS) and Diffuse Reflectance FTIR Spectroscopy (DRIFTS). Our results clearly indicate that a high temperature treatment with CO increases the dispersion of the nickel metallic phase. XAS results have shown a lower coordination number of Ni in the sample treated with CO than that reduced with H-2. From the DRIFTS results, it can he established that, under the CO treatment, the formation of Ni(CO)(4) complexes corrodes the nickel particles, decreasing their size. The formation of these gas molecules occurs without measurable losses of nickel from the catalyst which maintains the same nickel content after the hydrogen or the CO treatment at high temperature:Therefore, this airborne nickel compound, by colliding with the zirconia surface, must deposit the nickel metal metal atoms around onto the support. This behavior is evidence of an important interaction b etween nickel and zirconia surface as unlike other supports there is no losses of nickel during the dispersion process on zirconia. Although different effects of CO on nickel catalysts have been previously described, we have found for the first time several experimental evidences demonstrating the whole redispersion phenomenon.

Enero, 2011 | DOI: 10.1021/cs100116m

Titulo: Aluminum anodization in oxalic acid: Controlling the Texture of Al 2O3/Al monoliths for catalytic aplications
Autores: Sanz, O; Echave, FJ; Odriozola, JA; Montes, M
Revista: Industrial and Engineering Chemistry Research, 50 (2011) 2117-2125
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The anodization and postanodization processes of aluminum in order to prepare monoliths for catalytic applications have been studied in this work using oxalic acid as electrolyte. The effect of anodization variables (anodization time, current density, temperature, and electrolyte concentration) and postanodization processes on the surface morphology and textural properties of AAO (anodic aluminum oxide) films is analyzed. The anodization variables affect the two main processes taking part in the Al2O3 layer formation: alumina generation and its dissolution that are controlled by temperature, electrolyte concentration and time. The proper combination of both processes, as a result of the anodization variables choice, produces adherent alumina layers with tailored porosity and surface morphology that show excellent properties to be used as catalyst structured support. Larger pore sizes and the complete absence of sulfur that may poison reduced metal-supported active phases are main differences with the classical, most often used, sulfuric acid anodization process. © 2011 American Chemical Society.

Enero, 2011 | DOI: 10.1021/ie102122x

Titulo: Novel Bi2WO6-TiO2 heterostructures for Rhodamine B degradation under sunlike irradiation
Autores: Lopez, SM; Hidalgo, MC; Navio, JA; Colon, G
Revista: Journal of Hazardous Materials, 185 (2011) 1425-1434
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Highly efficient Bi2WO6-TiO2 heterostructure is synthesized by means of a hydrothermal method having highly photoactivity for the degradation of Rhodamine B under sunlike irradiation. From the structural characterization it has been demonstrated that TiO2 is incorporated on the Aurivillius structure. Interesting synergetic effect between TiO2 and Bi2WO6 leads to an improved charge carrier separation mechanism, causing the excellent photocatalytic performance under sunlike irradiation. The photocatalytic performance of Bi2WO6 and Bi2WO6-TiO2 was compared under different irradiation conditions and using increasing Rhodamine B concentration up to 25ppm. After the photocatalytic analysis of both systems, the mineralization efficiency of the heterostructure appears significantly higher with respect to Bi2WO6.

Diciembre, 2010 | DOI: 10.1016/j.jhazmat.2010.10.065

Titulo: Hydrogen production by methanol steam reforming on NiSn/MgO-Al2O3 catalysts: The role of MgO addition
Autores: Penkova, A; Bobadilla, L; Ivanova, S; Dominguez, MI; Romero-Sarria, F; Roger, AC; Centeno, MA; Odriozola, JA
Revista: Applied Catalysis A-General,392 (2011) 184-191
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The effect of the magnesia loading on the surface structure and catalytic properties of NiSn/MgO-Al2O3 catalysts for hydrogen production by methanol steam reforming has been investigated. The catalysts have been obtained by impregnation of γ-Al2O3 by the incipient wetness method, with variation of the MgO content. X-ray diffraction (XRD), BET surface area and H2-temperature programmed reduction (TPR) have been used to characterise the prepared catalysts. From this, it has been concluded that the incorporation of MgO results in the formation of MgAl2O4 spinel, which modifies the acid-base properties of the catalysts. The formation of Ni-Sn alloys after the reductive pre-treatment has also been evidenced. The influence of the temperature of reaction and of the MgO loading on the hydrogen production by reforming of methanol has been established. Moreover, tests of catalytic stability have been carried out for more than 20 h. The carbonaceous deposits have been examined by temperature-programmed oxidation (TPO). The analysis of the catalysts after reaction has confirmed the low level of carbon formation on these catalysts. In no case, carbon nanotubes have been detected on the solids.

Diciembre, 2010 | DOI: 10.1016/j.apcata.2010.11.016

Titulo: Comparative study of the photodeposition of Pt, Au and Pd on pre-sulphated TiO2 for the photocatalytic decomposition of phenol
Autores: Maicu, M; Hidalgo, MC; Colon, G; Navio, JA
Revista: Journal of Photochemistry and Photobiology A: Chemistry, 217 (2011) 275-283
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A comparative study of the photodeposition of Pt, Au and Pd under the same experimental conditions onto pre-sulphated and non-sulphated TiO2 was performed. Morphological and surface characterisation of the samples as well as photocatalytic activity for phenol photooxidation was studied. The influence of sulphate pre-treatment on the deposits size and dispersion onto the TiO2 surface, and photodeposition yields with the different metals were also analysed. The photocatalytic activity of the doped materials was then investigated, observing that catalytic behaviour can be correlated to physical characteristics of the samples determined by (XRD) X-ray diffraction, (XPS) X-ray photoelectron spectroscopy, (XRF) X-ray fluorescence spectrometry and (TEM) transmission electron microscopy. Sulphate pre-treatment was found to influence both the level of dispersion and the size of metal clusters on the TiO2 surface. Sulphation and metallisation of samples was found to produce a synergistic enhancement in photoactivity for the degradation of phenol. The photoactivity of the catalysts with respect to the doped metal species was ordered Pt > Pd > Au.

Diciembre, 2010 | DOI: 10.1016/j.jphotochem.2010.10.020

2010


Titulo: Gold supported on metal-doped ceria catalysts (M = Zr, Zn and Fe) for the preferential oxidation of CO (PROX)
Autores: Laguna, OH; Sarria, FR; Centeno, MA; Odriozola, JA
Revista: Journal of Catalysis, 276 (2010) 360-370
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A series of ceria oxides doped with 10 mol % of Zr Zn and Fe have been prepared by a pseudo sol-gel method throughout the thermal decomposition of the corresponding metallic propionates With these supports 1 wt % gold catalysts were prepared by the deposition-precipitation method All the solids were characterized by means of XRF N-2 adsorption XRD Raman spectroscopy and SEM techniques and their catalytic activity toward preferential oxidation of CO (PROX) reaction tested The results showed solid solution when doping with Zr and Fe and ZnO surface segregation in the case of Zn We demonstrate that gold dispersion depends on not only the oxygen vacancy concentration but also the nature of the doping agent Finally the catalytic activity was highly promoted by gold in all cases being the doped gold catalysts more active than Au/CeO2 at low temperature.

Noviembre, 2010 | DOI: 10.1016/j.jcat.2010.09.027

Titulo: Study of the stabilization of zinc phthalocyanine in sol-gel TiO2 for photodynamic therapy applications
Autores: Lopez, T; Ortiz, E; Alvarez, M; Navarrete, J; Odriozola, JA; Martinez-Ortega, F; Paez-Mozo, EA; Escobar, P; Espinoza, KA; Rivero, IA
Revista: Nanomedicine-Nanotechnology Biology and Medicine, 6 (2010) 777-785
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Photodynamic therapy (PDT) has emerged as an alternative and promising noninvasive treatment for cancer. It is a two-step procedure that uses a combination of molecular oxygen, visible light, and photosensitizer (PS) agents; phthalocyanine (Pc) was supported over titanium oxide but has not yet been used for cell inactivation. Zinc phthalocyanine (ZnPc) molecules were incorporated into the porous network of titanium dioxide (TiO2) using the sol-gel method. It was prepared from stock solutions of ZnPc and TiO2. ZnPc-TiO2 was tested with four cancer cell lines. The characterization of supported ZnPc showed that phthalocyanine is linked by the N-pyrrole to the support and is stable up to 250 degrees C, leading to testing for PDT. The preferential localization in target organelles such as mitochondria or lysosomes could determine the cell death mechanism after PDT. The results suggest that nanoparticulated TiO2 sensitized with ZnPc is an excellent candidate as sensitizer in PDT against cancer and infectious diseases. From the Clinical Editor: Photodynamic therapy is a two-step procedure that uses a combination of molecular oxygen, visible light and photosensitizer agents as an alternative and promising non-invasive treatment for cancer. The results of this study suggest that nanoparticulated TiO2 sensitized with ZnPc is an excellent photosensitizer candidate against cancer and infectious diseases.

Noviembre, 2010 | DOI: 10.1016/j.nano.2010.04.007

Titulo: Study of nanoporous catalysts in the selective catalytic reduction of NOx
Autores: Rico, MJO; Moreno-Tost, R; Jimenez-Lopez, A; Rodriguez-Castellon, E; Pereniguez, R; Caballero, A; Holgado, JP
Revista: Catalysis Today, 158 (2010) 78-88
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Two SBA-15 type materials were synthesized using a low-cost route, a pure silica SBA-15 and an Al containing SBA-15 (with a Si/Al ratio of 10), where Al was added by a post-synthesis modification. The later solid was achieved without any significant loss in the textural properties of SBA-15, besides improving its properties as support of catalysts. Copper impregnated catalysts were prepared through the incipient wetness impregnation of the two supports. With both supports, the copper weight loading were 1, 3 and 6 wt%. The copper incorporation kept the support mesoporous structures, obtaining a better dispersion of the active phase in the containing aluminium support. All the catalysts showed a moderated catalytic activity in the SCR of NO with propane in presence of an excess of oxygen in the whole studied interval of temperatures and a much better performance was observed when using NH3 instead of propane. The changes of the active phases were studied by operando XAS spectroscopy. Factor analysis of in operando XANES results with sample SiAl_6 indicate that no Cu-0 was detected, but only Cu1+ and Cu2+. The temperature where the Cu1+/Cu2+ ratio is maximum occurs at the reaction temperature where the observed catalytic NO conversion is also maximum.

Noviembre, 2010 | DOI: 10.1016/j.cattod.2010.04.016

Titulo: Physicochemical Characterization and Use of Wastes from Stainless Steel Mill
Autores: Dominguez, MI; Romero-Sarria, F; Centeno, MA; Odriozola, JA
Revista: Environmental Progress & Sustainable Energy, 29 (2010) 471-480
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Several types of wastes are produced during the manufacture of stainless steel (slags, refractory bricks, and dust). Most of these wastes are not recycled but stored in security deposits or landfills depending on their environmental danger This article reports the study of the physicochemical and mineralogical properties of stainless steel wastes. Their possible uses are also discussed.

Noviembre, 2010 | DOI: 10.1002/ep.10435

Titulo: Modified cryptomelane-type manganese dioxide nanomaterials for preferential oxidation of CO in the presence of hydrogen
Autores: Hernandez, WY; Centeno, MA; Romero-Sarria, F; Ivanova, S; Montes, M; Odriozola, JA
Revista: Catalysis Today, 157 (2010) 160-165
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Transition metal (Cu Co Ni and Zn)-modified cryptomelane-type manganese dioxide nanomaterials were synthesized by the milling method The obtained solids have been characterized by means of Xray diffraction (XRD) scanning electron microscopy and transmission electron microscopy (SEM and TEM) N-2 adsorption-desorption measurements at 77 K Raman spectroscopy and temperature programmed reduction (TPR-H-2) showing similar structural and textural properties All the solids were active in the preferential oxidation of CO in the presence of hydrogen (PROX) being the modified with copper the most active The catalytic activity correlates fairly well with the TPR results finding higher CO conversion for the material with higher reducibility (OMS-Cu) The O-2 selectivity measured as ([CO](in)-[CO](out)/2[O-2](in)-[O-2](out)) x 100 is very similar for all synthesized materials.

Octubre, 2010 | DOI: 10.1016/j.cattod.2010.03.010

Titulo: Iron-modified ceria and Au/ceria catalysts for Total and Preferential Oxidation of CO (TOX and PROX)
Autores: Laguna, OH; Centeno, MA; Arzamendi, G; Gandia, LM; Romero-Sarria, F; Odriozola, JA
Revista: Catalysis Today, 157 (2010) 155-159
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Iron-modified ceria supports containing different molar percentages of Fe (0% 10% 25% and 50%) were synthesized by thermal decomposition of the metal propionates The formation of a Ce-Fe oxide solid solution is evidenced through XRF XRD BET and Raman spectroscopy For Iron contents above 25% the formation of alpha-Fe2O3 was detected pointing out the formation of the isolated oxides The catalytic activity of the Fe-modified catalysts in the Total Oxidation of CO reaction (TOX) is higher than for the bare CeO2 material The synergy between Ce and Fe shows a maximum for 10% Fe content (CeFe10) catalyst that shows the highest CO conversion per atom of Fe incorporated Gold catalyst was also prepared on CeFe10 and its catalytic activity compared with Au/CeO2 catalyst The addition of iron to the gold catalyst resulted in an enhancement of the catalytic activity for CO oxidation especially at low temperature This Au/CeFe10 catalyst was also active and selective with excellent stability in the Preferential Oxidation of CO (PROX) showing a higher CO conversion than the Au/CeO2 catalyst at temperatures below 150 C being hardly affected by the presence of CO2 and H2O in the gas stream.

Octubre, 2010 | DOI: 10.1016/j.cattod.2010.04.011

Titulo: Photocatalytic degradation of phenolic compounds with new TiO2 catalysts
Autores: Araña, J; Dona-Rodriguez, JM; Portillo-Carrizo, D; Fernandez-Rodriguez, C; Perez-Pena, J; Diaz, OG; Navio, JA; Macias, M
Revista: Applied Catalysis B-Environmental, 100 (2010) 346-354
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New TiO2 catalysts have been synthesised by means of a sol-gel method in which aggregates have been selected before thermal treatment. Sieving and calcination temperature have been proved to be key factors in obtaining catalysts with greater photoactivity than that of Degussa P-25. These new catalysts have been characterized by means of transmission electron microscopy (TEM), BET surface area, diffuse reflectance spectroscopy (DRS). UV-vis spectroscopy, Fourier transformed infrared (FTIR) and X-ray diffraction (XRD). The different parameters studied were compared to those obtained from two commercial catalysts (Degussa P-25 and Hombikat-UV100). The photocatalytic efficiency of the new catalysts was evaluated by the degradation of various phenolic compounds using UV light (maximum around 365 nm, 9 mW). The catalyst sieved and calcinated at 1023 K, ECT-1023t, showed phenol degradation rates 2.7 times higher than those of Degussa P-25. Also in the degradation of different phenolic compounds, this catalyst showed a higher activity than that of the commercial one. The high photoactivity of this new catalyst has been attributed to the different distribution of surface defects (determined from FTIR studies) and its increased capacity to yield H2O2.

Septiembre, 2010 | DOI: 10.1016/j.apcatb.2010.08.011

Titulo: Synthesis of biodiesel from the methanolysis of sunflower oil using PURAL (R) Mg-Al hydrotalcites as catalyst precursors
Autores: Navajas, A; Campo, I; Arzamendi, G; Hernandez, WY; Bobadilla, LF; Centeno, MA; Odriozola, JA; Gandia, LM
Revista: Applied Catalysis B-Environmental, 100 (2010) 299-309
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A series of commercial Mg-Al hydrotalcites have been used as catalyst precursors for the methanolysis of sunflower oil.The solids were characterized by low Mg/Al molar ratios in the 0.5-2.3 range. Additionally, a solid consisting mainly of Mg(OH)(2) but containing some Al (4.2 wt.%) was also employed. The as-received materials were inactive for biodiesel synthesis so calcination and rehydration in boiling water were considered as activation treatments. Among the calcined solids, only the material consisting of MgO was significantly active, achieving about 50% oil conversion after 24h at 60 degrees C, methanol/oil molar ratio of 12 and 2 wt.% of catalyst. The effects of the calcination temperature in the 350-700 degrees C range have been investigated; calcination at 500 degrees C led to the best catalytic performance. In the case of the rehydrated materials, only the solids with the highest Mg/Al molar ratios recovered a well-ordered layered double hydroxide structure. These samples showed an improved catalytic activity compared with their calcined counterparts. A good correlation between catalytic activity and the basic properties determined using Hammett indicators and benzoic acid titration has been found. Rehydrated hydrotalcites were slightly more selective to biodiesel (75%) at intermediate levels of oil conversion than the calcined counterparts (66%). It has been verified that no Mg or Al leaching in the reaction mixture took place; however, the rehydrated samples deactivated significantly. In the case of MgO, after washing and calcination. the recycled catalyst gave 68% of the original oil conversion.

Septiembre, 2010 | DOI: 10.1016/j.apcatb.2010.08.006

Titulo: Characterisation and photocatalytic properties of titania-silica mixed oxides doped with Ag and Pt
Autores: Llano, B; Restrepo, G; Marin, JM; Navio, JA; Hidalgo, MC
Revista: Applied Catalysis A-General, 387 (2010) 135-140
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TiO2-SiO2 mixed oxides have been synthesised and modified by Ag and Pt deposition. Due to the effect of the silica on the mixed oxide, the prepared materials presented high surface areas and stabilised anatase as the only crystalline phase after calcination at 700 degrees C. Even using the same photodeposition experimental conditions, the yield for metal deposition depended highly on the metal considered, being much lower for Ag deposition. XPS studies permitted to estimate metal dispersion and oxidation state of the different samples, being both factors of high importance regarding photocatalytic improvement by metal deposition.

Septiembre, 2010 | DOI: 10.1016/j.apcata.2010.08.021

Titulo: Operando XAS and Raman study on the structure of a supported vanadium oxide catalyst during the oxidation of H2S to sulphur
Autores: Holgado, JP; Soriano, MD; Jimenez-Jimenez, J; Concepcion, P; Jimenez-Lopez, A; Caballero, A; Rodriguez-Castellon, E; Nieto, JML
Revista: Catalysis Today, 155 (2010) 296-301
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The modification of crystalline phases of a vanadium oxide supported on mesoporous zirconium phosphate during the partial oxidation of H2S to sulphur has been studied by using an operando Raman-GC approach and XAS in reaction conditions. The catalyst, mainly presenting crystalline V2O5, is transformed during the oxidation of H2S at 200 degrees C, presenting crystals of V4O9, which is identified by the presence of a band at ca. 900 cm(-1) in the Raman spectra (using a 785 nm line of an Argon ion laser) and by the presence of a pre-edge at 5469.8 eV (and a main-edge at 5482.2 eV) in XANES spectra. At the same time, it is observed a high conversion of H2S to sulphur (the main reaction product) and SO2 (as minority). Both activity and selectivity depend on the time on stream. In this way, the selectivity to SO2 decreases from ca. 5 to 1% with the time on stream. This change could be explained on the basis of the nature of V-species: the initial presence of V5+-O-V5+ pairs and the appearance of V5+-O-V4+ pairs at high time on stream.

Septiembre, 2010 | DOI: 10.1016/j.cattod.2010.02.050

Titulo: Structure and microstructure of EB-PVD yttria thin films grown on Si (111) substrate
Autores: Hartmanova, M; Jergel, M; Holgado, JP; Espinos, JP
Revista: Vacuum, 85 (2010) 535-540
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Structure and microstructure of yttria thin films grown by electron beam physical vapour deposition on a stationary Si (111) substrate at room temperature (RT), 500 degrees and 700 degrees C, were investigated by the grazing-incidence X-ray diffraction and scanning electron microscopy, respectively. X-ray photoelectron spectroscopy provided information on the surface contamination from the atmosphere and the oxidation state. A strong effect of the deposition temperature and the vapour flux incidence angle was found. The film deposited at RT is polycrystalline with very fine grains of the body-centered cubic (bcc) crystallographic symmetry. An increase of deposition temperature results in a rapid growth of bcc grains with an improved crystalline structure. Moreover, the based-centered monoclinic phase appears for the deposition temperature of 700 degrees C. Preferred grain orientation (texture) with two main components, (400) and (622), was observed in the films deposited at 500 degrees C whereas no texture was found for 700 degrees C. The microstructure exhibits the columnar feather-like structure of different degrees of perfection which can be explained by the shadowing effects caused by an oblique vapour flux incidence angle. Surface morphology of the films is governed by a combination of the triangular and four-sided (square) columns. All films were found to be dense with a little porosity between the columns.

Septiembre, 2010 | DOI: 10.1016/j.vacuum.2010.09.003

Titulo: AISI 304 austenitic stainless steel monoliths: Modification of the oxidation layer and catalytic coatings after deposition and its catalytic implications
Autores: Martinez, LMT; Sanz, O; Centeno, MA; Odriozola, JA
Revista: Chemical Engineering Journal, 162 (2010) 1082-1090
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Monolithic CeO2 and Au/CeO2 catalysts were prepared using austenitic stainless steel (AISI 304) as metallic substrate. Both monolithic and powdered catalysts were characterized before and after CO oxidation reaction by N-2 adsorption desorption, XRD, SEM, TEM and GD-OES. Catalyst deposition on the stainless steel surface results in modifications of the catalyst, the oxide scale and the oxide scale/alloy interface through the interaction between the coating and the steel oxidation layer. Besides this, oxidation of the alloy is also detected. The extension and nature of these modifications depends on the catalyst nature, and on the reaction conditions. As a result of these modifications CO oxidation on Au/CeO2 catalysts is enhanced and gold surface dynamics is modified.

Agosto, 2010 | DOI: 10.1016/j.cej.2010.07.005

Titulo: Study of nanostructured Ni/CeO2 catalysts prepared by combustion synthesis in dry reforming of methane
Autores: Gonzalez-Delacruz, VM; Ternero, F; Pereniguez, R; Caballero, A; Holgado, JP
Revista: Applied Catalysis A-General, 384 (2010) 1-9
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This work reports the study of several catalysts of Ni-CeO2 active for dry methane reforming process (CH4 + CO2 -> 2CO + 2H(2)). The use of Ni as active phase is highly preferred, due to its availability, high activity and low cost, although its main lack is the coke formation on the surface of Ni metal particles, resulting in a severe deactivation. Here we report a new synthesis method that allows a simple, effective and fast way to prepare Ni-CeO2 catalysts, in a wide range of metallic loadings, resulting in all the cases in well-formed NiO crystallites with sizes in the range of 12-18 nm. The use of CeO2 as a support has been based on its massive use in TWC catalysts formulations, where it is recognized to activate CH4 and lower hydrocarbon dissociation. Moreover, CeO2 has been reported to have an intrinsic activity in the CH4 reforming reaction. Besides the metallic loading, several factors that control the preparation method of the catalyst have been varied, in order to optimize their performance. Most of the catalysts prepared show activity and selectivity values close to thermodynamic ones, maintaining a good stability on long periods of time and severe conditions. Nevertheless, formation of some carbon nano-fibers has been observed, which could result in a drawback for their application at large scale.

Julio, 2010 | DOI: 10.1016/j.apcata.2010.05.027

Titulo: Determination of the local structure of a highly dispersed Pd-Nanosystem located on a titanium dioxide carrier
Autores: Kriventsov, VV; Novgorodov, BN; Yakimchuk, EP; Kochubey, DI; Zyuzin, DA; Simakova, IL; Chistyakov, AV; Zhmakin, VV; Bukhtenko, OV; Tsodikov, MV; Kozitsyna, NY; Vargaftik, MN; Moiseev, II; Maksimovskii, EA; Nechepurenko, SF; Navio, JA; Nikitenko, SG
Revista: Journal of Surface Investigation-X-Ray Synchrotron and Neutron Techniques, 4 (2010) 636-639
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This work is devoted to a structural study of a highly dispersed Pd nanosystem, which is stabilized in the TiO2 matrix, by XAFS spectroscopy. Nanocomposite was prepared from bimetallic PdCo(mu-OOCMe)(4)(NCMe) precursor followed by processing in several ways: calcination in air and in argon and microwave irradiation. The local structure of Pd catalysts formed by different methods was studied. Possible structural models were considered in detail.

Julio, 2010 | DOI: 10.1134/S1027451010040166

Titulo: Sunlight highly photoactive Bi2WO6-TiO2 heterostructures for rhodamine B degradation
Autores: Colon, G; Lopez, SM; Hidalgo, MC; Navio, JA
Revista: Chemical Communications, 46 (2010) 4809-4811
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Highly efficient Bi2WO6-TiO2 heterostructures are synthesized by means of a hydrothermal method; they have high photoactivity for the degradation of rhodamine B under sunlike irradiation. An interesting synergetic effect between TiO2 and Bi2WO6 leads to an improved charge carrier separation mechanism, causing the excellent photocatalytic performance.

Junio, 2010 | DOI: 10.1039/c0cc00058b

Titulo: In Situ Characterization of the Dynamic Gold-Support Interaction over Ceria Modified Eu3+. Influence of the Oxygen Vacancies on the CO Oxidation Reaction
Autores: Hernandez, WY; Romero-Sarria, F; Centeno, MA; Odriozola, JA
Revista: Journal of Physical Chemistry C, 114 (2010) 10857-10865
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Gold-supported ceria and europium-doped ceria catalysts were prepared by the deposition-precipitation method. The influence of the pretreatment atmosphere and temperature on the concentration of oxygen vacancies and gold dispersion on the Au/CeEti(10) catalyst under actual reaction conditions was investigated by "in situ" X-ray diffraction and Raman analysis. By Raman spectroscopy, a preferential interaction of the gold with the support across the oxygen vacancies was established and correlated with the gold dispersion. The increase in the concentration of oxygen vacancies in the presence of hydrogen induces changes in the gold crystallite size by breaking-off and migration of gold nanoparticles toward the oxygen vacancies on the CeEu(10) support. The activity of the Au/CeEu(10) solid in the CO oxidation reaction was significantly improved when the catalyst was preactivated in a reducing atmosphere. This trend could be associated with the redispersion of gold together with the increase in the concentration of oxygen vacancies in the support.

Mayo, 2010 | DOI: 10.1021/jp1013225

Titulo: Computational fluid dynamics study of heat transfer in a microchannel reactor for low-temperature Fischer-Tropsch synthesis
Autores: Arzamendi, G; Dieguez, PM; Montes, M; Odriozola, JA; Sousa-Aguiar, EF; Gandia, LM
Revista: Chemical Engineering Journal, 160 (2010) 915-922
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A three-dimensional computational fluid dynamics (CFD) study of heat transfer in a microchannel reactor for the low-temperature Fischer-Tropsch synthesis (FTS) is presented. The microreactor studied is a steel block with 80 square microchannels of 1 mm of side arranged in cross-flow configuration for the transport of syngas and cooling water. Syngas space velocities in the 5000-30,000 h(-1) (SIP) range have been considered. The microreactor exhibited good isothermicity under most simulated conditions. The FTS can be conducted with very low-temperature change between 483 and 523 K within a wide range of CO conversions using boiling water as coolant. To this end the pressure has to be set at the appropriate value between about Sand 35 atm. The pressure would have to be reduced as the CO conversion increases which might have a negative effect on the FTS selectivity to middle distillates. However, adjusting the cooling water flow rate in the range 0.25-250 g min(-1) allows maintaining the FTS temperature at suitable values while avoiding the use of low pressures. Relatively high values of the overall heat transfer coefficient in the 20-320 W m(-2) K-1 range have been obtained. A significant effect of the buoyancy forces on the thermal performance of the microreactor has been found.

Mayo, 2010 | DOI: 10.1016/j.cej.2009.12.028

Titulo: The Effect of Water on Particle Size, Porosity and the Rate of Drug Release From Implanted Titania Reservoirs
Autores: Lopez, T; Ortiz, E; Alexander-Katz, R; Odriozola, JA; Quintana, P; Gonzalez, RD; Lottici, PP; Marino, LG
Revista: Journal of Biomedical Materials Research Part-B Applied Biomaterials, 93B (2010) 401-406
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The implantation of controlled drug release devices represents a new strategy in the treatment of neurodegenerative disorders Sol-gel titania implants filled with valproic acid, have been used for this purpose to treat induced epilepsy in rats The kinetics of the drug release depend on. (a) porosity, (b) chemical interactions between valproic acid and surface hydroxyl groups of titania, (c) particle size, and (d) particle size agglomerates The concentration of water used in the hydrolysis reaction is an important variable in the degree of porosity, hydroxylation, and structural defects of the nanostructured titanium oxide reservoir The titanium n-butoxide/water ratio was systematically varied during the sol-gel synthesis, while maintaining the amount of valproic acid constant. Characterization studies were performed using DTA-TGA, FTIR, Raman, TEM, SEM, BET, and in vitro release kinetic measurements The particle agglomerate size and porosity were found to depend on the amount of water used in the sol-gel reactio.

Abril, 2010 | DOI: 10.1002/jbm.b.31595

Titulo: N- and/or W-(co)doped TiO2-anatase catalysts: Effect of the calcination treatment on photoactivity
Autores: Kubacka, A; Colon, G; Fernandez-Garcia, M
Revista: Applied Catalysis B-Environmental, 95 (2010) 238-244
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A series of nanosized W,N-codoped and single-doped N- and W-anatase-TiO2 catalysts have been prepared by a microemulsion method and calcined at different temperatures. The activity in the sunlight selective photo-oxidation of toluene and styrene has been correlated with structural, electronic, and surface examinations of the catalysts done with the help of XRD-Rietveld, N-2 physisorption, X-ray photoelectron, infrared, electron paramagnetic resonance (EPR) and UV-vis spectroscopies. Irrespective of the reaction, W,N-codoped nanocatalysts showed an enhanced photoactivity with respect to bare anatase and single-doped N-TiO2 and W-TiO2 materials. A strong W-N synergistic interaction appears to play a decisive role in driving the excellent photoactivity performance of W,N-codoped materials by affecting (i) electronic properties, particularly maximizing the anatase band gap decrease and enhancing the subsequent visible light photon absorption, and (ii) surface properties, in turn related to the formation of OH radicals upon light excitation. The maximum photoactivity is reached by calcination at 450 degrees C and is concomitantly observed with a near complete selectivity to partial oxidation products. Higher calcination temperatures yielded solids with significantly inferior photocatalytic performance. The properties of the W-N interaction are discussed as a function of the calcination temperature.

Marzo, 2010 | DOI: 10.1016/j.apcatb.2009.12.028

Titulo: Gas phase photocatalytic oxidation of toluene using highly active Pt doped TiO2
Autores: Colon, G; Maicu, M; Hidalgo, MC; Navio, JA; Kubacka, A; Fernandez-Garcia, M
Revista: Journal of Molecular Catalysis A-Chemical, 320 (2010) 14-18
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Platinum doped TiO2 materials were studied for the gas phase photocatalytic degradation of toluene. Platinum deposition was achieved by photodeposition method over TiO2 prepared by means of a sol-gel route. The effect of sulphuric acid pretreatment on the further platinisation process has been extensively studied. From the wide structural and surface analysis of the catalysts an interesting synergetic effect has been demonstrated. The previous sulphate treatment over TiO2 leads to improved dispersion of the Pt which presents a lower aggregation and homogeneous cluster size. This fact, together with the adequate control of anatase structural and surface parameter due to the sulphate treatment, renders a good photocatalytic performance for toluene oxidation reaction. The highest reaction rates and CO2 selectivities have been obtained for Pt-S-TiO2 samples.

Marzo, 2010 | DOI: 10.1016/j.molcata.2009.12.009

Titulo: Catalytic nanomedicine: Functionalisation of nanostructured cryptomelane
Autores: Lopez, T; Ortiz, E; Alvarez, M; Manjarrez, J; Montes, M; Navarro, P; Odriozola, JA
Revista: Materials Chemistry and Physics, 120 (2010) 518-525
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Nanostructured cryptomelanes (KMn8O16) were synthesized from manganese sulphate and manganese acetate precursors by the reflux method. The respectively obtained samples, CRYSO4 and CRYAc, were functionalised with hydroxyl, ammonium, sulphate and phosphate groups in order to modify the biocompatibility and surface properties of cryptomelane. Characterization by FTIR and XRD confirmed bond formation of CRY-NH, CRY=S=O, CRY-NH, and CRY=PO4. In both functionalise samples (CRYSO4-F and CRYAc-F), IR bands occurred at 1399 cm(-1), corresponding to the sulphate species, and 1106 cm(-1), related to phosphate vibrations; along with the OH and NH characteristic vibration bands in the high energy region. Biocompatibility of functionalised samples was tested by implantation of cryptomelane reservoir in the basolateral amygdala and caudal nucleus of Wistar rats using stereotactic surgery. The brains of the rats were processed in order to evaluate any damage associated with the implant. The results showed that functionalised cryptomelanes did not cause tissue damage or inflammation while not functionalised cryptomelanes caused cell death.

Marzo, 2010 | DOI: 10.1016/j.matchemphys.2009.11.049

Titulo: Room-Temperature Reaction of Oxygen with Gold: An In situ Ambient-Pressure X-ray Photoelectron Spectroscopy Investigation
Autores: Jiang, P; Porsgaard, S; Borondics, F; Kober, M; Caballero, A; Bluhm, H; Besenbacher, F; Salmeron, M
Revista: Journal of the American Chemical Society, 132 (2010) 2858-2859
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The interaction of O-2 with gold foil and gold nanoparticles grown by thermal deposition on TiO2(110) was studied by in situ ambient pressure X-ray photoelectron spectroscopy at room temperature. No spontaneous dissociation of O-2 was observed either on Au foil or oil Au nanoparticles up to 1 Torr of O-2. X-ray irradiation, however, is very effective in promoting gold oxidation on both surfaces in the presence of O-2. Our results help reconcile recent conflicting experimental observations regarding the activation of molecular oxygen, which is a crucial issue in Au catalyzed oxidation reactions.

Febrero, 2010 | DOI: 10.1021/ja909987j

Titulo: In situ spectroscopic detection of SMSI effect in a Ni/CeO2 system: hydrogen-induced burial and dig out of metallic nickel
Autores: Caballero, A; Holgado, JP; Gonzalez-delaCruz, VM; Habas, SE; Herranz, T; Salmeron, M
Revista: Chemical Communications, 46 (2010) 1097-1099
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In situ APPES technique demonstrates that the strong metal support interaction effect (SMSI) in the Ni-ceria system is associated with the decoration and burial of metallic particles by the partially reduced support, a phenomenon reversible by evacuation at high temperature of the previously absorbed hydrogen.

Enero, 2010 | DOI: 10.1039/b920803h

Titulo: Complete n-hexane oxidation over supported Mn-Co catalysts
Autores: Todorova, S; Kolev, H; Holgado, JP; Kadinov, G; Bonev, C; Pereniguez, R; Caballero, A
Revista: Applied Catalysis B-Environmental, 94 (2010) 46-54
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Two series of Co-Mn samples were prepared by impregnation of silica with aqueous solutions or Co(NO3)(2)center dot 6H(2)O and/or Mn(NO3)(2)center dot 6H(2)O. Cobalt oxide was the predominant phase in one of the series and manganese was used as the promoter. The major component in the second series was manganese oxide and Co was the promoter. The prepared samples were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), temperature-programmed reduction (TPR), and X-ray photoelectron spectroscopy (XPS) and tested in the reaction of complete n-hexane oxidation. The catalytic activity of both single component cobalt and manganese samples was similar, however, a combination between the two elements changed significantly the activity and this depended on the method of preparation. Catalysts prepared by a common solution of Co- and Mn nitrates manifested a considerable increase in activity as a result of very low crystallinity of the supported metal oxide phases, partial enrichment of the surface with cobalt and uniform distribution of oxide agglomerates on the support.

Enero, 2010 | DOI: 10.1016/j.apcatb.2009.10.019

Titulo: Doping level effect on sunlight-driven W,N-co-doped TiO2-anatase photo-catalysts for aromatic hydrocarbon partial oxidation
Autores: Kubacka, A; Bachiller-Baeza, B; Colon, G; Fernandez-Garcia, M
Revista: Applied Catalysis B-Environmental, 93 (2010) 274-281
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A series of nanosized W,N-co-doped anatase TiO2 catalysts with different dopant contents has been prepared by a microemulsion method and examined in the sunlight selective photo-oxidation of toluene and styrene. The activity results have been correlated with structural, electronic, and surface examinations of the catalysts done with the help of XRD-Rietveld, N-2 physisorption and NH3 chemisorption-calorimetry, XPS, Infrared, and UV-visible spectroscopies. Irrespective of the reaction, a consistent reaction rate enhancement with respect to titania (nano-TiO2, P25) references and W-doped TiO2 systems is observed for single-phase anatase W,N-co-doped samples. This is likely linked with the decrease of the band gap energy decrease and results from a combined W-N cooperative effect on structural properties of the anatase network. W,N simultaneous presence also makes a drastic effect on selectivity, maximizing the yield to partial oxidation products. This appears related with surface properties of the materials.

Diciembre, 2009 | DOI: 10.1016/j.apcatb.2009.09.039

Titulo: Synthesis and characterization of a LaNiO3 perovskite as precursor for methane reforming reactions catalysts
Autores: Pereñiguez, R; Gonzalez-DelaCruz, VM; Holgado, JP; Caballero, A
Revista: Applied Catalysis B-Environmental, 93 (2010) 346-353
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The objective of the present work has been the study of the physicochemical and catalytic properties of a Ni/La2O3 catalyst obtained by reduction of a lanthanum nickelite, LaNiO3, with perovskite structure. The perovskite, obtained by means of a spray pyrolysis method, provides a Ni/La2O3 system active in different methane reforming reactions. The catalyst was characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray absorption spectroscopy (XAS), X-Ray photoemission spectroscopy (XPS), temperature-programmed reduction and oxidation (TPR, TPO) and catalytic activity tests. Although not evidenced by XRD data, XAS and TPR measurements show the presence of an amorphous NiO phase in the original sample, together with the crystalline LaNiO3 phase. Upon reoxidation treatment of the reduced Ni/La2O3 catalyst, the LaNiO3 structure is partly recovered which provides a convenient way to regenerate a waste catalyst (reoxidation and new reduction in hydrogen). The catalyst is active in several reactions of methane with oxygen, water and CO2, showing a remarkable stability specially under dry reforming of methane (DRM) reaction conditions. This quite great catalytic performance has been explained by the high resistance of the nickel particles to be oxidized, as detected by in situ XAS. In the presence of water, as in steam reforming of methane (SRM) reaction conditions, these metallic particles are gradually oxidized, which explains the linear decreasing of the catalytic performance observed for the SRM reaction.

Diciembre, 2009 | DOI: 10.1016/j.apcatb.2009.09.040

Titulo: Supported nickel catalysts with a controlled molecular architecture for the catalytic reformation of methane
Autores: Hufschmidt, D; Bobadilla, LF; Romero-Sarria, F; Centeno, MA; Odriozola, JA; Montes, M; Falabella, E
Revista: Catalysis Today, 149 (2010) 394-400
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In this work a lanthanum and nickel catalyst having perovskite structure, grown on a gamma-alumina carrier, is being presented. The structure of the catalyst was confirmed by XRD. The behaviour of this material under the conditions of steam reforming has been studied and the influence of the temperature, the space velocity and the steam/carbon ratio on the conversion of methane and the product distribution in the process was determined. In all cases at higher temperatures conversions of more than 90% and high selectivities were achieved. The experiments to determine the stability of the catalyst demonstrated that no deactivation in experimental runs of more than 17h occurred. Additionally a study of the catalyst after the reaction showed that only lowly structured carbonaceous species were formed on the catalyst surface, which is not expected to inhibit strongly the initial catalytic activity.

Diciembre, 2009 | DOI: 10.1016/j.cattod.2009.06.002

Titulo: Chemical and electronic characterization of cobalt in a lanthanum perovskite. Effects of strontium substitution
Autores: Hueso, JL; Holgado, JP; Pereniguez, R; Mun, S; Salmeron, M; Caballero, A
Revista: Journal of Solid State Chemistry, 183 (2010) 27-32
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Two different cobaltites, LaCoO3 and La0.5Sr0.5CoO3-delta, have been prepared and characterized by means of high energy Co K-edge and low energy O K-edge X-ray absorption spectroscopy (XAS). Even though half of the La(III) is substituted by Sr(II), little or no changes call be detected in the formal oxidation state of cobalt atoms. The presence of strontium cations induces two main effects in the chemical and electronic state of the perovskite. The charge balance with Sr(II) species is reached by the formation of oxygen vacancies throughout the network, which explains the well-known increase in the reactivity of this Substituted perovskite. O K-edge XAS experiments show that the Sr(II) species induce the transitions of d electrons of cobalt cations from low to high Spill Configuration. We propose that this change in Spill Multiplicity is induced by two cooperative effects: the oxygen vacancies. creating five coordinated cobalt atoms, and the bigger size of Sr(II) cations, aligning the Co-O-Co atoms, and favoring the overlapping of pi-symmetry cobalt and oxygen orbitals, reducing the splitting energy of e(g) and t(2g) levels.

Diciembre, 2009 | DOI: 10.1016/j.jssc.2009.10.008

2009


Titulo: CO-TPR-DRIFTS-MS in situ study of CuO/Ce 1-xTbxO 2-y (x = 0, 0.2 and 0.5) catalysts: Support effects on redox properties and CO oxidation catalysis
Autores: Hornes, A; Bera, P; Camara, AL; Gamarra, D; Munuera, G; Martinez-Arias, A
Revista: Journal of Catalysis, 268 (2009) 367-375
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Catalysts of copper oxide supported on CeO2 and Ce1−xTbxO2−y have been studied by temperature-programmed reduction employing CO as a reductant (CO-TPR) using a diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) cell as well as conventional tubular reactors in order to get insights into redox changes occurring in the course of interaction of the systems with CO. CO-TPR results collected in the classical way, i.e. starting the temperature ramp after reactant gas equilibration at room temperature, suggest that the reduction of the copper species occurs at temperatures which decrease with the terbium content of the support. However, such result contrasts with CO oxidation activity of the systems under CO-PROX condition which follows just the opposite trend. DRIFTS results and analysis of low temperature redox processes, typically disregarded during recording of classical TPR tests, show that catalytic activity can be correlated to the magnitude of reduction achieved already at room temperature, which is related to reduction of interfacial copper oxide species.

Noviembre, 2009 | DOI: 10.1016/j.jcat.2009.10.007

Titulo: Self-Assembling of Er2O3-TiO2 Mixed Oxide Nanoplatelets by a Template-Free Solvothermal Route
Autores: Julian-Lopez, B; Martos, M; Ulldemolins, N; Odriozola, JA; Cordoncillo, E; Escribano, P
Revista: Chemistry-A European Journal, 15 (2009) 12426-12434
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An easy solvothermal route has been developed to synthesize the first mesoporous Er2O3-TiO2 mixed oxide spherical particles composed of crystalline nanoplatelets, with high surface area and narrow pore size distribution. This synthetic strategy allows the preparation of materials at low temperature with interesting textural properties without the use of surfactants, as well as the control of particle size and shape. TEM and Raman analysis confirm the formation of nanocrystalline Er2O 3-TiO2 mixed oxide. Mesoscopic ordered porosity is reached through the thermal decomposition of organic moieties during the synthetic process, thus leading to a template-free methodology that can be extended to other nanostructured materials. High specific surface areas (up to 313 m 2g-1) and narrow pore size distributions are achieved in comparison to the micrometric material synthesized by the traditional sol-gel route. This study opens new perspectives in the development, by solvothermal methodologies, of multifunctional materials for advanced applications by improving the classical pyrochlore properties (magnetization, heat capacity, catalysis, conductivity, etc.). In particular, since catalytic reactions take place on the surface of catalysts, the high surface area of these materials makes them promising candidates for catalysts. Furthermore, their spherical morphology makes them appropriate for advanced technologies in, for instance, ceramic inkjet printers.

Octubre, 2009 | DOI: 10.1002/chem.200901423

Titulo: Ionic liquid templated TiO2 nanoparticles as a support in gold environmental catalysis
Autores: Avellaneda, RS; Ivanova, S; Sanz, O; Romero-Sarria, F; Centeno, MA; Odriozola, JA
Revista: Applied Catalysis B-Environmental, 93 (2009) 140-148
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This work presents the synthesis of a nanostructured titania support and its subsequent utilization for the gold particles deposition and application in the reaction of the CO oxidation. A functionalized ionic liquid has been used as a templating agent for the titanium oxide synthesis resulting in a high specific surface nanostructured titania anatase. The as prepared support was then used for gold nanoparticles deposition without ionic liquid removal in order to study the possible role of the latter in the stabilization of the gold particles. The presence of ionic liquid in the catalysts results in an unusual catalytic behaviour—strong dependence on the presence of CO and changed kinetics and rate of oxidation.

Octubre, 2009 | DOI: 10.1016/j.apcatb.2009.09.023

Titulo: Methane steam reforming in a microchannel reactor for GTL intensification: A computational fluid dynamics simulation study
Autores: Arzamendia, G; Dieguez, PM; Montes, M; Odriozola, JA; Sousa-Aguiar, EF; Gandia, LM
Revista: Chemical Engineering Journal, 154 (2009) 168-173
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The integration of the steam reforming and combustion of methane in a catalytic microchannel reactor has been simulated by computational fluid dynamics (CFD). Two models including 4 or 20 square microchannels of 20 mm of length and 0.7 mm of side have been developed. It has been assumed that a thin and homogeneous layer of an appropriate catalyst has been uniformly deposited onto the channels walls. The kinetics of the steam reforming of methane (SRM), water-gas shift (WGS) and methane combustion in air have been incorporated into the models. This has allowed simulating the effect of the gas streams space velocities, catalyst load, steam-to-carbon (S/C) ratio and flow arrangement on the microreformer performance. The results obtained illustrate the potential of microreactors for process intensification: complete combustion of methane is achieved at gas hourly space velocities (GHSV) as high as 130,000 h−1. As concerns the SRM, methane conversions above 97% can be obtained at high GHSV of 30,000 h−1 and temperatures of 900–950 °C. Under these conditions selectivity for syngas is controlled by the WGS equilibrium.

Octubre, 2009 | DOI: 10.1016/j.cej.2009.01.035

Titulo: Manganese and iron oxides as combustion catalysts of volatile organic compounds
Autores: Duran, FG; Barbero, BP; Cadus, LE; Rojas, C; Centeno, MA; Odriozola, JA
Revista: Applied Catalysis B-Environmental, 92 (2009) 194-201
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FeMn mixed oxides were prepared by the citrate method with Fe:Mn atomic ratio equal to 1:1, 1:3 and 3:1. The sample was characterized by means of specific surface area measurements, X-ray diffractometry (XRD), temperature programmed desorption of oxygen (O2-DTP), temperature programmed reduction (TPR), X-ray fluorescence (XRF), transmission electron microscopy (TEM and SAED) and high resolution TEM (HREM). The characterization results demonstrated the formation of a Mn2O3–Fe2O3 solid solution. The catalytic performance in ethanol, ethyl acetate and toluene total oxidation on these samples was better than on Fe2O3 and Mn2O3 pure oxides.

Septiembre, 2009 | DOI: 10.1016/j.apcatb.2009.07.010

Titulo: Influence of sulfur on the structural, surface properties and photocatalytic activity of sulfated TiO2
Autores: Colon, G; Hidalgo, MC; Navio, JA; Kubacka, A; Fernandez-Garcia, M
Revista: Applied Catalysis B-Environmental, 90 (2009) 633-641
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TiO2 materials were prepared by sol–gel method and then impregnated with sulfuric acid and calcined using different temperatures and atmosphere (air and nitrogen). Systematic variation of these two experimental parameters makes possible to modulate the amount of surface sulfur from the impregnation procedure. The best photocatalyst for liquid phenol degradation was obtained after calcination at 700 °C in air, while gas toluene degradation optimum performance is obtained by calcination at 700 °C in nitrogen from 500 °C. Structural analysis of these materials by XRD, micro-Raman spectroscopy and FE-SEM shows that once calcined at 700 °C the material was a well-crystallized, high surface area anatase structure in all cases. The surface characterization by FTIR and XPS confirms the presence of a higher amount of sulfur species and acidic OH groups in samples partially calcined in nitrogen, and a low XPS O/Ti-atomic ratio with the O 1s peak shifted to higher binding energies (1.8 vs. 2 ± 0.1 and 530.4 eV vs. 529.8 eV, respectively, against the reference materials) for samples calcined at 700 °C, temperature at which most of sulfate species have been evolved. The paper presents an attempt to correlate the contribution of the observed structural defects within the anatase sub-surface layers and surface acidity to the different photoactivity behaviour exhibited for phenol liquid phase and toluene gas phase photodegradation.

Julio, 2009 | DOI: 10.1016/j.apcatb.2009.04.026

Titulo: Near-ambient X-ray photoemission spectroscopy and kinetic approach to the mechanism of carbon monoxide oxidation over lanthanum substituted cobaltites
Autores: Hueso, JL; Martinez-Martinez, D; Caballero, A; Gonzalez-Elipe, AR; Mun, BS; Salmeron, M
Revista: Catalysis Communications, 10 (2009) 1898-1902
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We have studied the oxidation of carbon monoxide over a lanthanum substituted perovskite (La0.5Sr0.5CoO3−d) catalyst prepared by spray pyrolysis. Under the assumption of a first-order kinetics mechanism for CO, it has been found that the activation energy barrier of the reaction changes from ∼80 to ∼40 kJ mol−1 at a threshold temperature of ca. 320 °C. In situ XPS near-ambient pressure (∼0.2 torr) shows that the gas phase oxygen concentration over the sample decreases sharply at ca. 300 °C. These two observations suggest that the oxidation of CO undergoes a change of mechanism at temperatures higher than 300 °C.

Julio, 2009 | DOI: 10.1016/j.catcom.2009.06.022

Titulo: Aluminium anodisation for Au-CeO2/Al2O3-Al monoliths preparation
Autores: Sanz, O; Martinez, LM; Echave, FJ; Dominguez, MI; Centeno, MA; Odriozola, JA; Montes, M
Revista: Chemical Engineering Journal, 151 (2009) 324-332
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The anodisation of aluminium monoliths was performed in order to generate an alumina layer that ensures a good adherence of the catalysts. In this study, it is demonstrated that the morphology of the produced alumina layer depends on time, temperature, current density and concentration of the selected electrolyte. When anodisation process with the extreme conditions was applied (30 °C, 50 min, 2 A dm−2 and 2.6 M of sulphuric acid) a significant cracks were obtained and used to fix the subsequent catalytic coatings. The washcoating method was used to cover the monoliths with colloidal solutions of CeO2 and/or Au-CeO2 catalysts. The resulting monolithic catalysts were tested in the CO oxidation reaction being 1%Au-CeO2 containing system the most active. The structured catalyst prepared this way changed neither the textural nor the catalytic properties of the deposited catalytic powders.

Julio, 2009 | DOI: 10.1016/j.cej.2009.03.062

Titulo: Reactivity of LaNi1−y Co y O3−δ Perovskite Systems in the Deep Oxidation of Toluene
Autores: Pereniguez, R; Hueso, JL; Holgado, JP; Gaillard, F; Caballero, A
Revista: Catalysis Letters, 131 (2009) 164-169
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In the present work we have evaluated the oxidation of toluene over different lanthanum perovskites with a general composition of LaNi1−y Co y O3−δ. These catalysts, prepared by a spray pyrolysis method, have been characterised by XRD, BET and FE-SEM techniques. Additional experiments of temperature programmed desorption of O2, reduction in H2 and X-ray absorption spectroscopy were also performed in order to identify the main surface oxygen species and the reducibility of the different perovskites. The catalytic behaviour toward the oxidation of toluene (as a model for VOCs compounds) was evaluated in the range 100–600 °C, detecting a total conversion for all the samples below 400 °C and higher activities for the cobalt-containing perovskites. The catalytic behaviour of these samples is consistent with a suprafacial mechanism, with the α-type oxygen playing an active role in the oxidation reaction.

Julio, 2009 | DOI: 10.1007/s10562-009-9968-0

Titulo: Structural characteristics and morphology of SmxCe1−xO2−x/2 thin films
Autores: Hartmanova, M; Jergel, M; Mansilla, C; Holgado, JP; Zemek, J; Jurek, K; Kundracik, F
Revista: Applied Surface Science, 255 (2009) 9085-9091
resumen | texto completo


Effect of the deposition temperature (200 and 500 °C) and composition of SmxCe1−xO2−x/2 (x = 0, 10.9–15.9 mol%) thin films prepared by electron beam physical vapor deposition (EB-PVD) and Ar+ ion beam assisted deposition (IBAD) combined with EB-PVD on structural characteristics and morphology/microstructure was investigated. The X-ray photoelectron spectroscopy (XPS) of the surface and electron probe microanalysis (EPMA) of the bulk of the film revealed the dominant occurrence of Ce4+ oxidation state, suggesting the presence of CeO2 phase, which was confirmed by X-ray diffraction (XRD). The Ce3+ oxidation states corresponding to Ce2O3 phase were in minority. The XRD and scanning electron microscopy (SEM) showed the polycrystalline columnar structure and a rooftop morphology of the surface. Effects of the preparation conditions (temperature, composition, IBAD) on the lattice parameter, grain size, perfection of the columnar growth and its impact on the surface morphology are analyzed and discussed.

Julio, 2009 | DOI: 10.1016/j.apsusc.2009.06.108

Titulo: FTIR study of photocatalytic degradation of 2-propanol in gas phase with different TiO2 catalysts
Autores: Arana, J; Alonso, AP; Rodriguez, JMD; Colon, G; Navio, JA; Pena, JP
Revista: Applied Catalysis B-Environmental, 89 (2009) 204-213
resumen | texto completo


The photocatalytic efficiency of different TiO 2 catalysts in the degradation of 2-propanol in gas phase has been studied. The obtained efficiencies have been compared considering the distribution of rutile-anatase phases, surface area, particle size, distribution of surface hydroxyl groups and Brönsted or Lewis acid centres. The catalysts used were Degussa-P25 (TiO 2-P25), Hombikat, Millennium, Kemira and s/g-TiO 2, a catalyst prepared by a sol-gel method. The best photocatalytic behaviours have been obtained with those catalysts with higher surface area and the presence of only anatase phase (Hombikat and Millennium). A progressive deactivation of TiO 2-P25 and s/g-TiO 2 has been observed during the photocatalytic process. FTIR studies indicated that degradation mechanisms depended on the catalyst employed. Deactivation processes observed in TiO 2-P25 have been correlated with the formation of carboxylates.

Junio, 2009 | DOI: 10.1016/j.apcatb.2008.11.027

Titulo: Effect of Sulfate Pretreatment on Gold-Modified TiO2 for Photocatalytic Applications
Autores: Hidalgo, MC; Maicu, M; Navio, JA; Colon, G
Revista: Journal of Physical Chemistry C, 113 (2009) 12840-12847
resumen | texto completo


The influence of sulfated pretreatment of TiO2 on the structure, morphology, and dispersion of gold and photocatalytic properties of Au/TiO2 were studied. Notable enhancements in the photocatalytic activity of TiO2 were achieved by deposition of gold onto samples that had previously undergone sulfate treatment followed by high temperature calcination. The enhancement in activity can be attributed to the stronger bonding and improved electronic communication between gold particles and TiO2 on defect rich surfaces as are found on sulfated samples after calcination at 700 °C. Two different methods for gold deposition were evaluated: chemical reduction by citrate and photodeposition. The citrate method produced more homogeneous and smaller gold particles with a better dispersion than photodeposition, which lead to greater increases in activity in the photocatalytic degradation of phenol when the former method was used for deposition on both sulfated and nonsulfated TiO2. The combination of sulfate pretreatment and gold deposition by chemical reduction was shown to be a good strategy to obtain gold/titania catalysts possessing homogeneous particle size and dispersion of the metal and a strong bonding between the Au and the TiO2 surface.

Junio, 2009 | DOI: 10.1021/jp903432p

Titulo: Deposition of Al-Fe pillared bentonites and gold supported Al-Fe pillared bentonites on metallic monoliths for catalytic oxidation reactions
Autores: Martinez, LM; Dominguez, MI; Sanabria, N; Hernandez, WY; Moreno, S; Molina, R; Odriozola, JA; Centeno, MA
Revista: Applied Catalysis A-General, 364 (2009) 166-173
resumen | texto completo


Al-Fe pillared bentonite and gold supported on Al-Fe pillared bentonite catalysts deposed on Fecralloy monoliths have been prepared, characterized and tested in two oxidation reactions: gaseous oxidation of CO and phenol oxidation in aqueous medium. The deposition of the solid on the metallic substrate does not alter its structural characteristics. The use of monoliths improves the activity in both reactions and offers the additional advantage to facilitate the separation of the catalyst from the reaction medium.

Junio, 2009 | DOI: 10.1016/j.apcata.2009.05.046

Titulo: ZnO activation by using activated carbon as a support: Characterisation and photoreactivity
Autores: Melian, EP; Diaz, OG; Rodriguez, JMD; Colon, G; Arana, J; Melian, JH; Navio, JA; Pena, JP
Revista: Applied Catalysis A-General, 364 (2009) 176-181
resumen | texto completo


The effect of the mixing ZnO with different portions of activated carbon (AC) has been studied. The resulting catalysts were characterised and evaluated in the photocatalytic decomposition of aqueous pollutants. Changes in the catalyst colour and in the FTIR vibration bands of the surface hydroxyl groups were recorded. νOH vibrations were shifted to lower wavenumbers as AC loading increased, demonstrating modification of the acid-base character of the catalysts. Laser scattering studies showed that AC loading leads to smaller ZnO particles. BET surface area measurements and scanning electron micrograph (SEM) analysis showed agglomeration of ZnO particle pores in the AC structure.

Results showed that in addition to a synergistic effect of the AC-ZnO combination, AC content modifies the ZnO particle properties and consequently photocatalytic behaviour. This was evident in phenol degradation experiments where changes in the concentration profiles of the catechol and hydroquinone degradation intermediates, were observed. However, the AC-ZnO catalysts were less efficient than pure ZnO in the degradation of 2,4-dichlorophenol (DCP). This seems to be due to the strong adsorption of the DCP molecule on AC, resulting in lower diffusion to the catalytic ZnO and thus a lower rate of photocatalysis.

Junio, 2009 | DOI: 10.1016/j.apcata.2009.05.042

Titulo: Degradation of n-Butyl tin Chlorides in Waters. A Comparative Assessment of the Process by Photo-assisted and Chemical- treatment Methods
Autores: Navio, JA; Cerrillos, C; Macias, M
Revista: Journal of Advanced Oxidation Technologies, 12 (2009) 158-163
resumen | texto completo


Titulo: Fibrous MnO2 Nanoparticles with (2 × 2) Tunnel Structures. Catalytic Activity in the Total Oxidation of Volatile Organic Compounds
Autores: Dominguez, MI; Navarro, P; Romero-Sarria, F; Frias, D; Cruz, SA; Delgado, JJ; Centeno, MA; Montes, M; Odriozola, JA
Revista: Journal of Nanoscience and Nanotechnology, 9 (2009) 3837-3842
resumen | texto completo


Manganese oxides having 2 × 2 tunnel structures (cryptomelanes) have been synthesized by a milling method in order to test their efficiency as catalysts for the abatement of volatile organic compounds, using toluene as probe molecule. These materials present excellent textural properties, arising from the nanofiber morphology and were active for toluene total oxidation. DRIFTS of the adsorbed phase allow proposing the role of lattice oxygen in the catalytic reaction.

Mayo, 2009 | DOI: 10.1166/jnn.2009.NS76

Titulo: Determination of nitrogen partitioning coefficients in superduplex stainless steels by NRA using a nuclear microprobe
Autores: Munoz, C; Morilla, Y; Lopez, JG; Paul, A; Odriozola, JA
Revista: Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 267 (2009) 2208-2211
resumen | texto completo


Superduplex stainless steels (SDSSs) combine the good mechanical behavior and the high corrosion resistance of the ferrite (α-Fe) and austenite (γ-Fe) phases. The SDSSs properties depend strongly on the partitioning of the elements that form the alloy. The ferrite is generally enriched in P, Si, Cr and Mo while the content of Ni, Mn, Cu and N in the austenite phase is higher. Nitrogen is known to be a strong austenite stabilizer and its presence increases the strength and the pitting corrosion resistance of the stainless steels. While the global nitrogen content in SDSSs can be readily determined using elemental analyzers, it cannot be measured at a microscopic scale.

In this work, the nuclear microprobe of the Centro Nacional de Aceleradores (Sevilla) was used to obtain the quantitative distribution of nitrogen in SDSSs. A deuteron beam of 1.8 MeV was employed to determine the overall elemental concentration of the matrix by deuteron-induced X-ray emission, whereas the nitrogen partitioning coefficients were obtained by using the 14N(d, α0)12C nuclear reaction. Mappings of this element show that the nitrogen ratio between the ferrite and austenite phases ranges from 0.3 to 0.6 in the analyzed samples.

Mayo, 2009 | DOI: 10.1016/j.nimb.2009.03.093

Titulo: W,N-Codoped TiO2-Anatase: A Sunlight-Operated Catalyst for Efficient and Selective Aromatic Hydrocarbons Photo-Oxidation
Autores: Kubacka, A; Bachiller-Baeza, B; Colon, G; Fernandez-Garcia, M
Revista: Journal of Physical Chemistry C, 113 (2009) 8553-8555
resumen | texto completo


New W,N-doped TiO2 anatase-based materials are synthesized having both unprecedent high activity and selectivity in the gas-phase partial oxidation of aromatic hydrocarbons using sunlight as excitation energy and molecular oxygen as oxidant.

Abril, 2009 | DOI: 10.1021/jp902618g

Titulo: Integration of methanol steam reforming and combustion in a microchannel reactor for H2 production: A CFD simulation study
Autores: Arzamendi, G; Dieguez, PM; Montes, M; Centeno, MA; Odriozola, JA; Gandia, LM
Revista: Catalysis Today, 143 (2009) 25-31
resumen | texto completo


A computational fluid dynamics (CFD) study of the thermal integration of the steam reforming of methanol (SRM) and the combustion of methanol in a catalytic microchannel reactor is presented. This issue is of interest for in situ H2 production for portable power units based on low-temperature PEM fuel cells. Three-dimensional simulations have been carried out under relevant conditions for the SRM reaction that have shown that microreactors allow achieving complete methanol reforming and combustion at space velocities as high as 50,000 h−1, with selectivities for H2 above 99% at relatively low temperatures in the 270–290 °C range.

Abril, 2009 | DOI: 10.1016/j.cattod.2008.09.034

Titulo: Cationic (V, Mo, Nb, W) doping of TiO2–anatase: A real alternative for visible light-driven photocatalysts
Autores: Kubacka, A; Colon, G; Fernandez-Garcia, M
Revista: Catalysis Today, 143 (2009) 286-292
resumen | texto completo


In this article we investigate the structure–activity link of anatase-type Ti–M (M = V, Mo, Nb, and W) mixed oxides used for toluene photo-oxidation under sunlight-type excitation. An analysis of the local and long-range structural and electronic characteristics of the mixed oxides show that only structurally highly homogeneous anatase-type oxides with electronic properties exclusively leading to a band gap decrease drive to efficient visible light-driven photocatalysts. Within our microemulsion preparation method, this only occurs for Ti–V and Ti–W series of samples. The isoelectronic (V4+) substitution of Ti4+ ions at the anatase lattice is characterized by a low solubility limit (ca. 2.5 at. %), and drives to a limited modification of the band gap and to a moderate enhancement of the photo-activity with respect to bare titania reference systems. W presence at anatase cation positions occurs with concomitant presence of cation vacancies derived by the charge imbalance between the W6+ and Ti4+ species. A unique W-vacancy local arrangement is detected by the structural characterization, leading to both an important band gap decrease and enhancement of the photo-activity upon sunlight excitation.

Abril, 2009 | DOI: 10.1016/j.cattod.2008.09.028

Titulo: AISI 304 Austenitic stainless steels monoliths for catalytic applications
Autores: Martinez, LM; Sanz, O; Dominguez, MI; Centeno, MA; Odriozola, JA
Revista: Chemical Engineering Journal, 148 (2009) 191-200
resumen | texto completo


The thermal treatments of austenitic stainless steels monoliths were studied in order to generate a highly homogeneous and rough oxide scale strongly attached to the base alloy, which will subsequently ensure the good adherence of the catalysts. In this work it has been shown that the morphology, integrity and homogeneity of the scale are strongly influenced by the temperature and time of treatment. Washcoating method was used to deposit on the monolith surface a Au/CeO2 catalyst. The drying procedure turned out to be the most critical variable for the adherence and homogeneity of the catalytic ceria layer, while the ceria colloid concentrations in the starting aqueous dispersion seems to have only a threshold effect. The monolithic reactors containing Au/CeO2 layers are active in the oxidation of CO.

Abril, 2009 | DOI: 10.1016/j.cej.2008.12.030

Titulo: Gold/hydroxyapatite catalysts: Synthesis, characterization and catalytic activity to CO oxidation
Autores: Dominguez, MI; Romero-Sarria, F; Centeno, MA; Odriozola, JA
Revista: Applied Catalysis B-Environmental, 87 (2009) 245-251
resumen | texto completo


This work reports the synthesis, characterization and catalytic activity for CO oxidation of gold catalysts supported on calcium hydroxyapatite. On both, the hydroxyapatite support and the gold-supported hydroxyapatite catalyst, the CO conversion shows a peak near 100% of conversion at room temperature. The generation of structural vacancies by interaction of CO with the solid provokes the formation of peroxide species in the presence of gaseous oxygen, which seems to be responsible of this high conversion of CO at room temperature. Moreover, the influence of the pre-treatment temperature on the activity has been observed and related with the elimination of carbonate species and the generation of structural defects in the apatite structure, which are able to modify the gold oxidation state.

Marzo, 2009 | DOI: 10.1016/j.apcatb.2008.09.016

Titulo: Synthesis and Characterization of Ce1−xEuxO2−x/2 Mixed Oxides and Their Catalytic Activities for CO Oxidation
Autores: Hernandez, WY; Centeno, MA; Romero-Sarria, F; Odriozola, JA
Revista: Journal of Physical Chemistry C, 113 (2012) 5629-5635
resumen | texto completo


A series of Ce1−xEuxO2−x/2 mixed oxides was synthesized by coprecipitation. The solids were characterized by means of XRF, SBET, XRD, UV−vis, and Raman techniques, and their catalytic activities toward CO oxidation were tested. A solid solution, with CeO2 F-type structure, is formed for europium contents (measured as Eu2O3 by XRF) ≤20% wt. For higher contents, the solid solution is not formed, but a physical mixture is detected. The existence of oxygen vacancies in the solids with Eu2O3 contents between 3 and 17% wt was demonstrated by the presence of bands at 532 and 1275 cm−1 in their Raman spectra. The catalytic performances of the solids correlate with the amount of these punctual defects in the solid solution.

Marzo, 2009 | DOI: 10.1021/jp8092989

Titulo: Co3O4 + CeO2/SiO2 Catalysts for n-Hexane and CO Oxidation
Autores: Todorova, S; Kadinov, G; Tenchev, K; Caballero, A; Holgado, JP; Pereniguez, R
Revista: Catalysis Letters, 129 (2009) 149-155
resumen | texto completo


Two-component Co–Ce samples deposited onto SiO2 have been prepared, characterized and tested in the reaction of complete n-hexane and CO oxidation. It was established that cerium enhanced the catalytic activity of cobalt in the reaction of n-hexane oxidation, although this depended on the sequence of cobalt and cerium introduction. Co-impregnation of Co and Ce resulted in a close interaction between Co3O4 and CeO2 leading to more surface oxygen species available and, therefore, a better reactivity.

Marzo, 2009 | DOI: 10.1007/s10562-008-9805-x

Titulo: Pillared clays with Al–Fe and Al–Ce–Fe in concentrated medium: Synthesis and catalytic activity
Autores: Sanabria, NR; Centeno, MA; Molina, R; Moreno, S
Revista: Applied Catalysis A-General, 356 (2009) 243-249
resumen | texto completo


This paper proposes a new methodology for the modification of clays with the mixed Al–Fe and Al–Ce–Fe systems, which involves the synthesis of solid polymeric precursors and their use as pillaring agents in the modification of clays. The process of intercalation of clay with Al13, Al13 + Fe and Al13 + Ce + Fe nitrate was performed using ultrasound. The pillaring agents Al13, Al13 + Fe and Al13 + Ce + Fe were characterized by XRF, XRD, SEM and 27Al NMR techniques, and pillared clays were characterized by XRF, XRD and N2 adsorption to 77 K. The catalytic properties of pillared clays were evaluated using catalytic wet peroxide oxidation of phenol in dilute aqueous medium, demonstrating activity comparable to that of solids modified by the conventional method.

Febrero, 2009 | DOI: 10.1016/j.apcata.2009.01.013

Titulo: Redox chemistry of gold in a Au/FeOx/CeO2 CO oxidation catalyst
Autores: Penkova, A; Chakarova, K; Laguna, OH; Hadjiivanov, K; Saria, FR; Centeno, MA; Odriozola, JA
Revista: Catalysis Communications, 10 (2009) 1196-1202
resumen | texto completo


Calcination and evacuation of a Au/FeOx/CeO2 catalyst at 573 K leads to reduction of the deposited gold to metal. This metal state is stable under oxygen and only at 573 K some metal atoms are oxidized to Auδ+ sites (Au+ cations situated on metal gold particles). However, even at room temperature, gold is readily oxidized in a CO + O2 mixture producing, in addition to the Auδ+ sites, some isolated Au+ cations.

Febrero, 2009 | DOI: 10.1016/j.catcom.2009.01.014

Titulo: Gold nanoparticles on silica monospheres modified by amino groups
Autores: Penkova, A; Blanes, JMM; Cruz, SA; Centeno, MA; Hadjiivanov, K; Odriozola, JA
Revista: Microporous and Mesoporous Materials, 117 (2009) 530-534
resumen | texto completo


Silica monospheres with a diameter of 330 nm modified with aminosilane compounds of three different basicities have been prepared. Surface coverage of the silica with an organic compound leads to an increase of the point of zero charge (PZC) of the silica surface from 2.1 to 5.1, 6.5 and 7.2 values, depending on the amine used. From these silicas, gold-containing catalysts have been prepared by a deposition–precipitation method at the same pH as the PZC of the support. The best results have been obtained using 3-(Diethoxymethylsilyl) propylamine as a modifying agent, which has allowed obtaining a good dispersion of the gold particles with an average size of 3.8 nm.

Diciembre, 2008 | DOI: 10.1016/j.micromeso.2008.07.041



Cristina Megías Sayago
Catalizadores híbridos bifuncionales para la valorización química de biomasa

Director/es: Svetlana Ivanova y José Antonio Odriozola
Universidad de Sevilla
Viernes, 29 Septiembre, 2017




Paola Zambrano Chacón
Desarrollo de materiales fotocatalizadores basados en Bi, Ti y O con alta actividad en el visible para la eliminación de contaminantes en agua

Director/es: José Antonio Navío Santos y Maria Del Carmen Hidalgo López
Universidad de Sevilla
Viernes, 22 Septiembre, 2017




Mayra Anabel Lara Angulo
Desarrollo de Materiales Basados en TIO2 Modificado con Funcionalidad Fotocatalítica para Aplicaciones Medioambientales

Director/es: José Antonio Navío Santos y Maria Del Carmen Hidalgo López
Universidad de Sevilla
Viernes, 7 Julio, 2017




Miriam González Castaño
Design, Characterization and Structuring of Pt based Catalysts for Water Gas Shift Reaction

Director/es: José Antonio Odriozola Gordón y Svetlana Ivanova
Universidad de Sevilla
Jueves, 10 Diciembre, 2015




José María Martínez Blanes
Obtención de Zeolitas utilizando Líquidos Iónicos como Agentes Directores de Estructura

Director/es: José Antonio Odriozola Gordón y Svetlana Ivanova
Universidad de Sevilla
Miércoles, 2 Diciembre, 2015




Sergio Alberto Obregón Alfaro
Síntesis y Optimización de Sistemas Fotocatalíticos basados en BiVO4 mediante Incorporación de Iones a Tierras Raras

Director/es: Gerardo Colón Ibáñez
Universidad de Sevilla
Viernes, 20 Febrero, 2015




Andrea Álvarez Moreno
Reformado Catalítico de Biomasa. Ajuste de la estequiometría de los productos para la reacción de Fischer-Tropsch

Director/es: Miguel Angel Centeno Gallego y José Antonio Odriozola Gordón
Universidad de Sevilla
Viernes, 13 Febrero, 2015




Sandra Palma del Valle
Producción de hidrógeno a partir de metanol: diseño, síntesis y caracterización de un catalizador de PROX

Director/es: Francisca Romero-Sarria y José Antonio Odriozola Gordón
Universidad de Sevilla
Viernes, 7 Noviembre, 2014




Victor Manuel González de la Cruz
Estudio de la actividad catalítica y de la interacción metal-soporte en sistemas de níquel soportados en ZrO2 y CeO2, activos en las reacciones de reformado de metano

Director/es: Alfonso Caballero Martínez y Juan Pedro Holgado Vázquez
Universidad de Sevilla
Jueves, 17 Julio, 2014




Tomás Ramírez Reina
Diseño y caracterización de cataliazadores basados en oro para la reacción de water gas shift

Director/es: José Antonio Odriozola Gordón y Svetlana Ivanova
Universidad de Sevilla
Lunes, 30 Junio, 2014




Ara Muñoz Murillo
Catalizadores de Ru/TiO2 para la metanación selectiva de CO

Director/es: José Antonio Odriozola Gordón y Miguel Angel Centeno Gallego
Universidad de Sevilla
Viernes, 31 Enero, 2014




Julie Joseane Murcia Mesa
Control de la nanoestructura de sistemas M-TiO2 (M=Pt y Au) preparados por fotodeposición con propiedades fotocatalíticas optimizadas

Director/es: Carmen Hidalgo López y José Antonio Navío Santos
Universidad de Sevilla
Viernes, 12 Julio, 2013




Sebastián Murcia López
Desarrollo de Materiales basados en Bismuto con Alta Eficiencia Fotocatalítica para Aplicaciones de Química Verde

Director/es: José Antonio Navío Santos y M. Carmen Hidalgo López
Universidad de Sevilla
Martes, 9 Abril, 2013




Fátima A. Ternero Fernández
Sistemas Catalíticos Basados en Nanopartículas Mono y Bimetálicas Activos en Procesos de Interés Medioambiental

Director/es: Alfonso Caballero Martínez y Juan Pedro Holgado Vázquez
Universidad de Sevilla
Miércoles, 27 Febrero, 2013




Oscar Hernando Laguna Espitia
Oxidación preferencial de CO en presencia de H2: diseño de catalizadores basados en CeO2 y aplicación a microrreactores

Director/es: José Antonio Odriozola Gordón y Miguel Angel Centeno Gallego
Universidad de Sevilla
Viernes, 30 Septiembre, 2011




Luis F. Bobadilla Baladrón
Obtención de hidrógeno a partir de la biomasa. Reformado catalítico de glicerina

Director/es: José Antonio Odriozola Gordon y Francisca Romero Sarria
Universidad de Sevilla
Viernes, 15 Abril, 2011




Willinton Yesid Hernández Enciso
Relación estructura de defectos – actividad catalítica en sistemas sólidos tipo Au/Ce1-xEuxO2-x/2 y MnOx. Aplicación en la reacción de oxidación preferencial de CO en presencia de H2.

Director/es: José Antonio Odriozola Gordón y Miguel Angel Centeno Gallego
Universidad de Sevilla
Viernes, 26 Noviembre, 2010




Sylvia Andrea Cruz Torres
Aplicaciones de la Técnica “Spark Plasma Sintering” a la Obtención de Materiales y Dispositivos de Interés en Catálisis

Director/es: José Antonio Odriozola Gordón
Universidad de Sevilla
Viernes, 17 Septiembre, 2010




Rosa Pereñíguez Rodríguez
Obtención de H2 mediante reformado de CH4 sobre sólidos con estructura perovskita: LaNi1-xCoxO3

Director/es: Alfonso Caballero Martínez y Juan Pedro Holgado Vázquez
Universidad de Sevilla
Viernes, 21 Mayo, 2010




Marina Maicu
Estudio de la actividad fotocatalítica de sistemas basados en TiO2, sulfatado y no sulfatado, y modificado con Pt, Au y Pd

Director/es: José Antonio Navío Santos, Gerardo Colón Ibáñez, Maria del Carmen Hidalgo López
Universidad de Sevilla
Martes, 16 Febrero, 2010




Rafael Sánchez Avellaneda
Estudio e influencia de itrio y otros modificadores superficiales en el comportamiento de catalizadores soportados en TiO2

Director/es: José Antonio Odriozola, Miguel Angel Centeno, Francisca Romero Sarria
Universidad de Sevilla
Viernes, 5 Febrero, 2010




Leidy Marcela Martínez Tejada
Deposición de catalizadores sobre superficies metálicas para aplicaciones catalíticas

Director/es: José Antonio Odriozola y Miguel Angel Centeno
Universidad de Sevilla
Viernes, 4 Abril, 2008




José Luis Hueso Martos
Eliminación de contaminantes mediante procesos de plasma-catalizador

Director/es: Alfonso Caballero Martínez y Agustín R. González-Elipe
Universidad de Sevilla
Miércoles, 19 Septiembre, 2007




Catalina Mansilla Sánchez
Síntesis, caracterización y determinación de propiedades ópticas y eléctricas de capas finas de materiales basados en óxido de cerio

Director/es: Juan Pedro Holgado Vázquez y Francisco Yubero Valencia
Universidad de Sevilla
Viernes, 13 Julio, 2007




Ana María Cordón Rodríguez
Estudio de sistemas catalíticos basados en ZrO2 para la reducción catalítica selectiva de NOx usando hidrocarburos como agentes reductores

Director/es: Alfonso Caballero Martínez y Juan Pedro Holgado Vázquez
Universidad de Sevilla
Viernes, 15 Septiembre, 2006




María Isabel Domínguez Leal
Diseño de materiales a partir de residuos industriales. Aplicaciones catalíticas

Director/es: José Antonio Odriozola y Miguel Angel Centeno
Universidad de Sevilla
Viernes, 21 Abril, 2006




Francisco Gracia Torres
Películas delgadas basadas en TiO2 y MxO2 con aplicaciones fotoelectroquímicas y ópticas

Director/es: Agustín R. González-Elipe y Juan Pedro Holgado Vázquez
Universidad de Sevilla
Lunes, 30 Mayo, 2005




José Jorge Morales Domingo
Estudio del sistema CuOx/ZrO2 en procesos de eliminación catalítica de óxidos de nitrógeno

Director/es: Alfonso Caballero Martínez y Juan Pedro Espinós Manzorro
Universidad de Sevilla
Viernes, 4 Marzo, 2005




Said El Mrabet
Diseño de aceros inoxidables austeníticos resistentes a la oxidación a alta temperatura. Efectos de la composición de la matriz y de las modificaciones superficiales

Director/es: José Antonio Odriozola Gordón y Antonio Paúl Escolano
Universidad de Sevilla
Lunes, 3 Febrero, 2003


Rosa Pereñíguez, Premio Real Maestranza de Caballería 2015


Fuente: CicCartuja

Rosa Pereñíguez Rodríguez, Investigadora del Instituto de Ciencia de Materiales de Sevilla (ICMS) perteneciente al cicCartuja, ha sido galardonada con uno de los dos Premios para Investigadores Jóvenes que cada año entrega la Fundación Real Maestranza de Caballería.

Los estudios llevados a cabo por esta joven científica se centran en la preparación y caracterización de materiales catalíticos nanoestructurados, aplicados a la descontaminación ambiental y a la búsqueda de fuentes alternativas de energía, por ejemplo, mediante la producción de hidrógeno empleando sistemas basados en perovskitas.

Rosa es Doctora en Ciencias Químicas por la Universidad de Sevilla y trabaja como investigadora en el grupo “Materiales y Procesos Catalíticos de Interés Ambiental y Energético” del ICMS. Además, compagina esta labor con su actividad docente en el Departamento de Química Inorgánica de la Universidad de Sevilla.

Los Premios para Investigadores Jóvenes de la Real Maestranza se entregan con la colaboración de la Real Academia Sevillana de Ciencias y están dotados con 6.000 euros. Su propósito es recompensar cada año los méritos científicos de investigadores jóvenes destacados y estimular su vocación y dedicación a la ciencia.


Óscar H. Laguna gana el Premio de Tesis Doctoral del Ayuntamiento de Sevilla 2012


El investigador colombiano Óscar Hernando Laguna Espitia ha obtenido uno de los siete premios que concede el Área de Cultura, Educación, Juventud y Deportes del Ayuntamiento de Sevilla a las mejores tesis doctorales defendidas en la Universidad de Sevilla y en la Universidad Pablo de Olavide durante el curso académico 2010-2011. El galardón le ha sido otorgado por su trabajo “Oxidación preferencial de CO en presencia de H2: diseño de catalizadores basados en CeO2 y aplicación a microrreactores”, presentado en la Universidad de Sevilla y realizado, en su mayor parte, en el Instituto de Ciencia de Materiales de Sevilla (ICMS). Esta tesis ha sido dirigida por el Catedrático de Química Inorgánica de la Universidad de Sevilla José Antonio Odriozola y el Investigador Científico del CSIC Miguel Ángel Centeno.

Óscar Hernando Laguna, que actualmente amplía su formación en la Universidad del País Vasco, fue becario FPI entre septiembre de 2007 y octubre de 2011 en el grupo de investigación dirigido por el Profesor Odriozola (Departamento de Química Inorgánica de la Universidad de Sevilla-ICMS). En este período participó en proyectos encaminados a desarrollar procesadores de combustible para aplicaciones móviles basados en la producción de energía a partir de hidrógeno (H2). Guiado por los profesores Odriozola y Centeno, Óscar Hernando Laguna desarrolló su tesis doctoral sobre la eliminación del monóxido de carbono (CO) remanente en las corrientes de hidrógeno producidas al transformar alcoholes. Estas corrientes son las utilizadas para alimentar las celdas de combustible, que, a su vez, producirán electricidad.

Al premiar esta tesis, el Área de Cultura, Educación, Juventud y Deportes del Ayuntamiento de Sevilla ha valorado la relevancia de las aportaciones teóricas y prácticas del trabajo, que cuenta con una amplia proyección en el sector energético. El estudio de la purificación de las corrientes de hidrógeno contribuye, principalmente, a optimizar la utilización del hidrógeno como fuente de energía alternativa, con menores residuos contaminantes. La aplicación de este tipo de investigaciones repercute en un mejor rendimiento de las celdas de combustible, las baterías eléctricas que funcionan a partir del hidrógeno y que, por su versatilidad, pueden usarse con prometedores resultados en dispositivos móviles o en la industria automovilística, por citar un par de ejemplos.

Como señala el propio autor, desde un principio esta tesis se diseñó desde un enfoque integrador, contemplando desde los principios fundamentales hasta las aplicaciones finales. “En primer lugar, se han diseñado catalizadores para la oxidación de CO. Esto implica concebir los sistemas desde escalas atómicas para entender los principios a partir de los cuales se favorece la reacción de oxidación de CO”, describe Óscar Hernando Laguna. Para ello, se han utilizado sistemas basados en óxido de cerio modificado con diferentes metales de transición. “Posteriormente, se ha llevado a cabo un análisis cinético de los sistemas más prometedores en la reacción de oxidación preferencial de CO en presencia de H2 (PROX), pensando en el futuro escalado del proceso”.

Según el investigador, uno de los aspectos más llamativos del trabajo se produjo al considerar la aplicación final. En esta última fase, se puso en funcionamiento un prototipo de microrreactor (o reactor de microcanales), diseñado y fabricado en los laboratorios del ICMS para la reacción PROX, que se saldó con éxito. En palabras de Óscar Hernando Laguna, “estos dispositivos favorecen lo que se denomina ‘intensificación de procesos’, que conduce a un aumento de la eficiencia energética y la producción de menor cantidad de subproductos. Tanto la industria como la comunidad científica están convencidas de que su desarrollo ofrece un atractivo panorama para este tipo de reacciones a nivel industrial”. No en vano, son tales las posibles aplicaciones de este tipo de estudios relacionados con la purificación de las corrientes de hidrógeno que algunos de los proyectos en los que ha participado este investigador se han desarrollado junto a empresas líderes del sector energético, como la multinacional Petróleos de Brasil (Petrobas).

El enfoque integrador de esta tesis doctoral ha permitido no sólo que destaque por su proyección industrial, sino también en el ámbito académico, donde ha cosechado un notable impacto. Hasta la fecha, se han publicado once artículos en revistas internacionales a raíz de esta investigación. Asimismo, Óscar Hernando Laguna ha tenido la oportunidad de participar en diversos congresos internacionales relacionados con el tema de catálisis o los microrreactores, en los que ha realizado presentaciones exponiendo parte de los resultados obtenidos.

El acto de entrega de los premios a las mejores tesis –dotadas económicamente con 2.000 euros cada una– se celebrará en el Salón Colón del Ayuntamiento de Sevilla el 4 de diciembre de 2012, a las 11:00 h. Dicho acto estará presidido por el Alcalde de Sevilla, Juan Ignacio Zoido, y los rectores de la Universidad de Sevilla y la Universidad Pablo de Olavide.


Soporte para catalizador de oro para la generación de H2 que alcanza un 100% de conversión del CO

El CSIC y la Universidad de Sevilla han patentado un nuevo catalizador de oro de la reacción de WGSR (water gas shift reaction) útil para la producción y/o purificación de H2 para aplicaciones en las celdas de combustible. Se trata de un catalizador capaz de trabajar a bajas temperaturas, en el rango en el que la reacción es termodinámicamente más eficiente y que presenta gran estabilidad y facilidad de regeneración.

Se buscan socios industriales para la licencia de la patente

Icono PDF Catalizador.pdf