Synergetic effect of VO_x and TeO_x species in mesoporous SiO₂ on selective oxidation of propane to acrolein

A mesoporous silica with incorporated vanadium (V) and tellurium (Te) (3%VTe_zO_x-MS; z = 0-0.33), synthesized by an evaporation-induced self-assembly route, was used as a model catalyst to investigate the synergetic effect of VO_x and TeO_x species on propane oxidation to acrolein. It was found that V in the catalyst was predominantly present as a highly dispersed VO₄ species, while Te existed as a highly dispersed TeO_x species when the Te/V atomic ratio was below 0.2. Acrolein formation rate was positively correlated with TeO _x content when both VO_x and TeO_x in the catalysts were in a highly dispersed state. Study of the propane oxidation pathways further indicated that highly dispersed VO₄ in close contact with highly dispersed TeO_x constituted the active sites for direct oxidation of propane to acrolein. These binary sites satisfied all the required functions for the reactions, including consecutive sequence of activation of propane and propylene intermediate followed by inserting oxygen into the as-formed allylic species.