Spectroscopic study of V 2O 5 supported on zirconia and modified with MoO 3

Abstract

Vanadium oxide supported on zirconia and modified with MoO 3 was prepared by adding Zr(OH) 4 powder into a mixed aqueous solution of ammonium metavanadate and ammonium molybdate followed by drying and calcining at high temperatures. In the case of calcination temperature at 773 K, for samples containing low loading V 2O 5 below 15 wt.%, vanadium oxide was in a highly dispersed state, while for samples containing high-loading V 2O 5 equal to or above 15 wt.%, vanadium oxide was well crystallized due to the V 2O 5 loading exceeding the formation of a monolayer on the surface of ZrO 2. The experimental results indicate that the presence of MoO 3 and V 2O 5 retards the crystallization of the zirconia and stabilizes the tetragonal ZrO 2 phase without phase transition to cubic ZrO 2 phase. The ZrV 2O 7 and Zr(MoO 4) 2 compounds were formed through the reaction of V 2O 5 and ZrO 2 or MoO 3 and ZrO 2 at 873 K and the compound decomposed into V 2O 5, MoO 3, and ZrO 2 at high temperatures, which were confirmed by Fourier transform infrared (FTIR) and Raman spectroscopies, solid-state 51V nuclear magnetic resonance (NMR), and X-ray diffraction (XRD). IR spectroscopic studies of ammonia adsorbed on V 2O 5–ZrO 2/MoO 3 showed the presence of both Lewis and Brönsted acids.