Study of Dispersion and Thermal Stability of V₂O₅/TiO₂−SiO₂ Catalysts by XPS and Other Techniques

A high surface area titania−silica binary oxide support was prepared according to the homogeneous precipitation method and was coated with a monolayer of vanadium oxide. The TiO 2 −SiO 2 support and the V 2 O 5 /TiO 2 −SiO 2 catalyst were then subjected to thermal treatments from 773 to 1073 K. The influence of heat treatments on the dispersion and thermal stability was investigated by X-ray diffraction, FT infrared, X-ray photoelectron spectroscopy, oxygen uptake, and BET surface area methods. The results suggest that TiO 2 −SiO 2 is quite thermally stable even up to 1073 K calcination temperature. However, the V 2 O 5 /TiO 2 −SiO 2 catalyst is stable, in terms of dispersion and surface area, only up to a calcination temperature of 873 K. Thermal treatments beyond this temperature transformed vanadia and titania into crystalline phases and then titania anatase into rutile phase.