Artículos SCI
2020
2020
Química de Superficies y Catálisis
Time-resolved operando DRIFTS-MS study of the moisture tolerance of small-pore SAPO-34 molecular sieves during CH4/CO2 separation
Romero, M; Navarro, JC; Bobadilla, LF; Dominguez, MI; Ivanova, S; Romero-Sarria, F; Centeno, MA; Odriozola, JAMicroporous and Mesoporous Materials, 298 (2020) 110071
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This study pretends to evaluate and understand the effect of moisture presence during CO2/CH4 separation on small-pore SAPO-34 molecular sieves. Two SAPO-34 samples with different physicochemical properties (composition, crystal size and texture) were prepared by hydrothermal synthesis using either one or a mixture of two templates. Transient operando DRIFTS-MS measurements revealed that the sample's hydrophobic character is associated to the presence of Si islands, which enhanced sample's moisture tolerance during repetitive adsorption/desorption cycles. This knowledge is fundamental to achieve the rational design of efficient SAPO-34 membranes under realistic conditions.
Mayo, 2020 | DOI: 10.1016/j.micromeso.2020.110071
Materiales y Procesos Catalíticos de Interés Ambiental y Energético
Structural and surface considerations on Mo/ZSM-5 systems for methane dehydroaromatization reaction
Lopez-Martin, A; Caballero, A; Colon, GMolecular Catalysis, 486 (2020) 110787
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We have prepared a series of Mo/ZSM-5 systems by impregnation method with different metal loading. The optimum performance has been attained for 4% metal loading, yielding to ca. 2 mmol(benzene)/g(ca)(t) at the end of the reaction. The obtained catalysts were widely structural and surface characterized. As Mo content increases, the surface feature of the support is affected specially its mesoporosity. It has been stated the enormous complexity of Mo species present in the studied system. In situ characterization by XPS reveals different reduction and carburization behaviour depending on the Mo content.
Mayo, 2020 | DOI: 10.1016/j.mcat.2020.110787
Fotocatálisis Heterogénea: Aplicaciones
Microwave-assisted sol-gel synthesis of TiO2 in the presence of halogenhydric acids. Characterization and photocatalytic activity
Puga,F.;Navío,J.A.;Jaramillo-Páez,C.;Sánchez-Cid,P.;Hidalgo,M.C.Journal of Photochemistry and Photobiology A: Chemistry, 394 (2020) 112457
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The synthesis of mesoporous TiO2 nanosheets is reported using Ti(IV) Isopropoxide as Ti(IV) precursor. A sol-gel process combined with microwave activation is used. Three different halogenhydric acids (HX), were used to peptise the sol: HF(ac), HCl (ac) and HBr (ac). The three obtained TiO2-I(HX) samples were characterized by XRD, XRF, N2-adsorption, SEM, TEM, DRS and XPS. The three synthesized samples have high values of specific surfaces (between 100 m2/g and 200 m2/g) and similar band gap values (3.2–3.3 eV). The analysis of the surface composition by XPS confirms the presence of the halogenated species (F, Cl or Br) on the surface of each ones of the samples. The nanometric size (ca 5 nm) of the particles for each of the three samples was confirmed by XRD and by TEM. On the other hand, the nature of the halogenated acid used plays a role in the composition of the phases. While the TiO2-I (HF) sample was 100 % anatase, the other samples turned out to be biphasic, showing anatase/rutile in the TiO2-I(HCl) sample and anatase/brookite in the TiO2-I(HBr) sample. The samples were tested under two illumination conditions (UV and visible light) using rhodamine B and caffeine. The indirect role of the halide agent on the photocatalytic activities thereof is discussed.
Mayo, 2020 | DOI: 10.1016/j.jphotochem.2020.112457
Nanotecnología en Superficies y Plasma
Optical properties of molybdenum in the ultraviolet and extreme ultraviolet by reflection electron energy loss spectroscopy
Pauly, N; Yubero, F; Tougaard, SApplied Optics, 59 (2020) 4527-4532
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Optical properties of polycrystalline molybdenum are determined from ultraviolet up to extreme ultraviolet by reflection electron energy loss spectroscopy (REELS). Calculations are performed within the dielectric response theory by means of the quantitative analysis of electron energy losses at surfaces QUEELS-epsilon (k, omega)-REELS software [Surf. Interface Anal. 36, 824 (2004)] that allows the simulation of inelastic scattering cross sections, using a parametric energy loss function describing the optical response of the material. From this energy loss function, the real and imaginary parts of the dielectric function, the refractive index, and the extinction coefficient are deduced and compared with previously published results.
Mayo, 2020 | DOI: 10.1364/AO.391014
Materiales Ópticos Multifuncionales
Premelting of ice adsorbed on a rock surface
Esteso, V; Palacios, SC; MacDowell, LG; Fiedler, J; Parsons, DF; Spallek, F; Miguez, H; Persson, C; Buhmann, SY; Brevik, I; Bostrom, MPhysical Chemistry Chemical Physics, 22 (2020) 11362-11373
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Considering ice-premelting on a quartz rock surface (i.e. silica) we calculate the Lifshitz excess pressures in a four layer system with rock-ice-water-air. Our calculations give excess pressures across (1) ice layer, (2) water layer, and (3) ice-water interface for different ice and water layer thicknesses. We analyse equilibrium conditions where the different excess pressures take zero value, stabilized in part by repulsive Lifshitz interactions. In contrast to previous investigations which considered varying thickness of only one layer (ice or water), here we present theory allowing for simultaneous variation of both layer thicknesses. For a given total thickness of ice and water, this allows multiple alternative equilibrium solutions. Consequently the final state of a system will depend on initial conditions and may explain variation in experimental measurements of the thicknesses of water and ice layers.
Mayo, 2020 | DOI: 10.1039/c9cp06836h
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