Langmuir, Vol.18, No.16, 6280-6288, 2002
Spectroscopic study of V2O5 supported on zirconia and modified with WO3
Vanadium oxide-tungsten oxide supported on zirconia was prepared by adding Zr(OH)(4) powder into a mixed aqueous solution of ammonium metavanadate and ammonium metatungstate followed by drying and calcining at high temperatures. The characterization of prepared catalysts was performed using Fourier transform infrared (FTIR) and Raman spectroscopies, solid-state V-51 NMR, X-ray diffraction (XRD), and differential scanning calorimetry (DSC). In the case of a calcination temperature of 773 K for samples containing a low loading of V2O5, below 18 wt%, vanadium oxide was in a highly dispersed state, while for samples containing a high loading of V2O5, equal to or above 18 wt%, vanadium oxide was well crystallized because the V2O5 loading exceeded the formation of a monolayer on the surface of ZrO2. The experimental results indicate that the presence of WO3 and V2O5 retards the crystallization of the zirconia and stabilizes the tetragonal ZrO2 phase. The ZrV2O7 compound was formed through the reaction of V2O5 and ZrO2 at 873 K and the compound decomposed into V2O5 and ZrO2 at 1073 K; these results were confirmed by FTIR spectroscopy, solid-state V-51 NMR, and XRD. The catalytic tests for 2-propanol dehydration have shown that the addition of WO3 to V2O5/ZrO2 enhanced both catalytic activity and acidity of V2O5-WO3/ZrO2 catalysts.