Characterization of V2O5/TiO2−ZrO2 Catalysts by XPS and Other Techniques

Abstract

A high surface area titania-zirconia mixed oxide support was prepared by the technique of precipitation from homogeneous solutions. Vanadia (12 wt %) was impregnated on TiO2−ZrO2 support by using an oxalic acid solution of NH4VO3. The TiO2−ZrO2 binary oxide support and the V2O5/TiO2−ZrO2 catalyst were then subjected to thermal treatments from 500 to 800 °C. The influence of thermal treatments on the dispersion and stability of the catalyst was investigated by X-ray diffraction (XRD), FT infrared (FTIR), UV−vis absorption, and X-ray photoelectron spectroscopy (XPS) techniques. The characterization results suggest that the TiO2−ZrO2 binary oxide support is thermally quite stable up to 800 °C. Calcination of the coprecipitated titanium−zirconium hydroxides at 500 °C result in the formation of an amorphous phase, and further heating at 600 °C converts this amorphous phase into a crystalline ZrTiO4 compound. Impregnation of V2O5 and heating of the V2O5/TiO2−ZrO2 catalyst beyond 600 °C results in the formation of ZrV2O7, with the simultaneous presence of the TiO2 rutile phase. However, the vanadia is in a highly dispersed state on the TiO2−ZrO2 mixed oxide support when calcined at less than 600 °C.