STUDY OF DISPERSION AND THERMAL-STABILITY OF V2O5 TIO2-SIO2 CATALYSTSBY XPS AND OTHER TECHNIQUES/

A high surface area titania-silica binary oxide support was prepared a ccording to the homogeneous precipitation method and was coated with a monolayer of vanadium oxide. The TiO2-SiO2 support and the V2O5/TiO2- SiO2 catalyst were then subjected to thermal treatments from 773 to 10 73 K. The influence of heat treatments on the dispersion and thermal s tability was investigated by X-ray diffraction, FT infrared, X-ray pho toelectron spectroscopy, oxygen uptake, and BET surface area methods. The results suggest that TiO2-SiO2 is quite thermally stable even up t o 1073 K calcination temperature. However, the V2O5/TiO2-SiO2 catalyst is stable, in terms of dispersion and surface area, only up to a calc ination temperature of 873 K. Thermal treatments beyond this temperatu re transformed vanadia and titania into crystalline phases and then ti tania anatase into rutile phase.