An Alternative Method for the Incorporation of Silver in Ag-VOx/TiO2 Catalysts for the Total Oxidation of Benzene

An alternative way of synthesis, the "onion" method, was used to deposit silver nanoparticles on a VOx/TiO2 catalyst. This synthesis method consists in the impregnation of organic vesicles containing the metallic silver nanoparticles. In situ calcination is needed to remove the organic vesicles and to offer an access of the reactants to the silver nanoparticles. This removal is easier in presence of vanadium. The addition of silver induces a higher proportion of V5+. The Ag-VOx/TiO2 catalysts prepared with this method exhibit better performances in the total oxidation of benzene after moderate in situ calcination at 350 A degrees C than at 450 A degrees C. A synergy between silver and vanadium is evidenced after both kinds of calcination with a silver loading of 0.125 and 0.25 wt%. The extent of this synergy is higher after a moderate calcination. This effect is likely due to the fact that small nanoparticles prepared via the "onions" sinter less after in situ calcination at 350 A degrees C than at 450 A degrees C. A clear link between the extent of the synergy and the size of the silver nanoparticles is evidenced. A decrease of the nanoparticle size induces a higher extent for the synergy.