Preparation of highly loaded vanadium oxide-silica catalysts

A technique for the application of vanadium oxide onto silica supports starting from trivalent vanadium precursors is described. At loadings up to 30 wt.%, transmission electron microscopy and X-ray diffraction show the presence of highly dispersed vanadium oxide particles in calcined samples, which is very unusual for silica-supported vanadium oxide. Combined with recorded precipitation curves and temperature-programmed reduction profiles, these results indicate a good interaction between the silica support and the vanadium oxide precursor. The kinetic parameters of the catalytic oxidation of carbon monoxide are significantly different from those of both bulk V₂O₅ and impregnated silica-supported vanadium oxide on the one hand and from TiO₂- and Al₂O₃-supported vanadium oxide on the other. X-ray photoelectron spectroscopic and IR data indicate that a considerable concentration of vanadium (IV) remains after calcination. Selectivity profiles of this catalyst in the selective catalytic reduction of nitric oxide with ammonia proved to be significantly different from those of both TiO₂- and Al₂O₃-supported vanadium oxide and bulk V₂O₅. The typical selectivity profiles, the deviating activity in the carbon monoxide oxidation and the spectroscopic results for these catalysts all indicate a strong interaction between the active vanadium oxide and the silica support.