SODIUM-DOPED V2O5/TIO2 SYSTEMS - AN XRD, DTA, TG/DTG, IR, V-UV, TPR, AND XANES STUDY

Vanadia-titania samples doped with different amounts of sodium have been prepared by impregnation of titania (P-25) with aqueous solutions of ammonium vanadate and calcination at 770 K, and have been characterized by X-ray diffraction, differential thermal analysis, thermogravimetric analysis, Fourier Transform-infrared spectroscopy, visible-ultraviolet (diffuse reflectance) spectroscopy, temperature-programmed reduction, and X-ray absorption near-edge structure spectroscopy. The results obtained indicate that doping the vanadia-titania system with increasing amounts of sodium leads initially to formation of VNaO compounds with a Na/V ratio close to 0.5 that are reduced at a higher temperature than V2O5, formed in the absence of sodium. If the amount of sodium is increased up to 3%, formation of Na3VO4 has been found. © 1992.