Design of stable and reactive vanadium oxide catalysts supported on binary oxides

Abstract

A series of titania based mixed oxides viz., TiO2-SiO2, TiO2-Al2O3, TiO2-ZrO2, and TiO2-Ga2O3 were prepared by a coprecipitation method. These mixed oxides were impregnated with V2O5 ranging from 2 to 30 wt% by using ammonium metavanadate as source of vanadium oxide. The mixed oxide supports and the vanadia impregnated catalysts were then subjected to thermal treatments from 773 to 1073 K and were investigated by XRD, FTIR, O2 uptake and BET surface area methods to establish the effects of vanadia loading and thermal treatments on the surface structure of dispersed vanadia species and thermal stability of the catalysts. Calcination of coprecipitated support hydroxides at 773 K resulted in the formation of an amorphous phase, and further heating to 1073 K resulted in the formation of titania anatase phase, except with TiO2-ZrO2 support where a ZrTiO4 compound was observed. All these mixed oxides exhibited a high thermal stability. Oxygen uptake results suggested a high dispersion of vanadia on these mixed oxide supports when calcined at 773 K. The mixed oxide based V2O5 catalysts studied are found to be very active and selective for the synthesis of isobutyraldehyde from methanol and ethanol, and for the selective oxidation of 4-methylanisole to anisaldehyde.