Characterization of vanadium sites on vanadium-containing mesoporous silica catalysts and their catalytic behaviour in propane ODH

Abstract

Parameters that affect the catalytic behaviour of vanadium-containing mesoporous silicas in oxidative dehydrogenation reaction of propane are mainly aggregation state of surface VOx species and reducibility of vanadium species. Type and conditions of synthesis have big impact on the nature of vanadium species and, therefore, influence significantly catalytic properties. Two vanadiumcontaining mesoporous silica catalysts were synthesized by different techniques (including direct synthesis from hydrogel containing vanadium precursor and wet impregnation of SBA-15 mesoporous silica by vanadyl acetylacetonate) and their physico-chemical and catalytic properties were studied and compared. Direct synthesis of vanadosilicate led to catalysts with non-uniform mesoporosity, but exhibiting better spreading of vanadium on the surface resulting in species with lower degree of polymerization compared to impregnated catalyst. It is reflected in higher iso-conversional selectivity of directly synthesized catalyst towards propene.