Selective oxidation of toluene on V2O5/TiO2/SiO2 catalysts modified with Te, Al, Mg, and K2SO4

The effect of the modification of vanadia catalysts supported on TiO2/SiO2 by the oxides of Al, Mg and Te, and K2SO4 on the selective oxidation of toluene in the vapor phase has been studied. The catalysts were prepared by successive impregnation and characterized by BET surface measurements, XRD, XPS, and TPR. Addition of the second component decreased specific activity in all cases, except Al, mainly due to the decrease of surface area. Intrinsic activity was increased with addition of Te and Al, and decreased by that of Mg, while K2SO4, had little effect. These differences could be explained by the observed changes in either vanadium surface dispersion or reducibility. Selectivity to benzaldehyde increased markedly with addition of Te or K2SO4, that caused the formation of new oxide phases, V3Ti6O17 and TiV2O6, in which vanadium is in a partially reduced state.