Effect of silica on the catalytic destruction of chlorinated organics over V2O5/TiO2 catalysts

In the present work, the contribution of silica doping to the catalytic activity of V2O5/TiO2 based catalysts in the decomposition of chlorinated organic materials and on the formation of possible by by-products was investigated. The influence of vanadium loading on surface structures of differently supported materials has been systematically investigated by XRD, BET, Raman spectroscopy and H2-TPR. These studies demonstrated that the V2O5 supported on either TiO2/WO3 or TiO2/WO3/SiO2 is very active for the oxidation of o-DCB, a probe molecule for aromatic compounds which is present in flue gas. Silica was found to form a highly dispersed amorphous phase on the support surface, which strongly affects the structural degradation phenomena, delaying the collapse of surface area, that is particularly significant at high vanadium content. The presence of silica on the support influences the distribution of VOx species. Since it was demonstrated that support surfaces predominantly covered with highly dispersed vanadium lead to high activity, in spite of the lower ability of SiO2 to spread metal oxides, the higher stability of silica containing materials, while preserving surface area, favors vanadium dispersion and leads to superior catalytic performance.