Artículos SCI

Stainless steels slags are mainly composed of low specific surface area calcium silicates together with a variable amount of metallic cations dispersed in such silicate matrix. These silicates due to their heavy metals content have to be considered as hazardous wastes that cannot be reclaimed easily. An alternative to reclamation is the production of valuable materials designed to accomplish processes without economic profit as the abatement of VOCs. In this paper we describe a method for obtaining high specific surface area (up to 290 m(2) g(-1)) metal-doped SiO2 and SiO2/ Al2O3 supports for catalytic applications using as raw materials stainless steel slags. The acid digestion of these slags followed by a hydrothermal treatment results in transition metal oxides doped silicas and silica-aluminas that are used as support for platinum catalysts. The prepared catalysts are active in the total oxidation of CO and toluene, showing comparable activities to those shown by Pt catalysts supported on commercial SiO2.(

Two different solids consisting of Pd or Zn-containing titania systems (metal/titanium nominal ratio of 1%) were submitted to diverse oxidative and reductive calcination treatments and tested for gas-phase selective photooxidation of 2-propanol. As regards the Pd system, reduction at low temperature (<= 500 degrees) resulted in a gradual increase in catalytic activity which was ascribed to the gradual reduction of bulk palladium to Pd-0. Thermal treatment of the system at high temperature (850 degrees C) in static air, air flow or hydrogen flow led to a decrease in activity as the result of the sharp decrease in surface area. Nevertheless, those systems containing Pd-0 only were more active than the one consisting of Pd + PdO. Finally, Pd-system overcame I'd migration to the surface on reduction at 850 degrees C which resulted in a significant increase in selectivity to acetone up to 97% for a time on stream of 5 h. As regards the Zn-containing system, none of the applied treatments resulted in improvement in photocatalytic activity. It seems that the most favourable situation for photocatalysis is that on which Zn atoms are substituting titanium ones in the lattice, whereas segregation of Zn to form small ZnO clusters is especially detrimental to activity.