Spectroscopic Study of V<INF>2</INF>O<INF>5</INF> Supported on Zirconia and Modified with WO<INF>3</INF>

Vanadium oxide−tungsten oxide supported on zirconia was prepared by adding Zr(OH)<INF>4</INF> 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 ⁵¹V 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 V<INF>2</INF>O<INF>5</INF>, below 18 wt %, vanadium oxide was in a highly dispersed state, while for samples containing a high loading of V<INF>2</INF>O<INF>5</INF>, equal to or above 18 wt %, vanadium oxide was well crystallized because the V<INF>2</INF>O<INF>5</INF> loading exceeded the formation of a monolayer on the surface of ZrO<INF>2</INF>. The experimental results indicate that the presence of WO<INF>3</INF> and V<INF>2</INF>O<INF>5</INF> retards the crystallization of the zirconia and stabilizes the tetragonal ZrO<INF>2</INF> phase. The ZrV<INF>2</INF>O<INF>7</INF> compound was formed through the reaction of V<INF>2</INF>O<INF>5</INF> and ZrO<INF>2</INF> at 873 K and the compound decomposed into V<INF>2</INF>O<INF>5</INF> and ZrO<INF>2</INF> at 1073 K; these results were confirmed by FTIR spectroscopy, solid-state ⁵¹V NMR, and XRD. The catalytic tests for 2-propanol dehydration have shown that the addition of WO<INF>3</INF> to V<INF>2</INF>O<INF>5</INF>/ZrO<INF>2</INF> enhanced both catalytic activity and acidity of V<INF>2</INF>O<INF>5</INF><INF>-</INF>WO<INF>3</INF>/ZrO<INF>2</INF> catalysts.