Effect of vanadium dispersion and support properties on the catalytic activity of V-SBA-15 and V-MCF mesoporous materials prepared by direct synthesis

Two V-SBA-15 and V-MCF materials (V content ca. 2.5 wt.%) were prepd. by direct synthesis and tested in the catalytic decompn. of dichloromethane. Their catalytic properties were compared to those of other materials with the same vanadium content, namely two mesoporous materials prepd. by impregnation (V-SBA-15-i and V-MCF-i) and a non-porous one prepd. by flame pyrolysis (V-SiO2). Both direct synthesis and flame pyrolysis methods allowed a better vanadium dispersion that lead to better catalytic properties above 350 °C, due to the presence of well dispersed V species partially incorporated into silica. The higher dichloromethane conversion achieved with both V-SBA-15 and V-SBA-15-i samples, as compared to MCF samples, are ascribed to longer residence times of both reactants and products within SBA-15 mesoporous channels, in contrast to three-dimensional MCF ultra large pores facilitating diffusion. Below 350 °C, both V-SBA-15-i and V-MCF-i samples showed higher dichloromethane conversion, basically due to the presence of micro-cryst. V2O5 formed at the external surface of both materials