Synthesis, characterization, and activity studies of vanadia supported on zirconia and phosphorus-modified zirconia

A series of catalysts with vanadia contents varying between 1 and 14 wt % w ere prepared by the wet impregnation technique on zirconia and phosphorus-m odified zirconia. The catalysts were characterized by employing X-ray diffr action (XRD), electron spin resonance (ESR) spectroscopy, V-51, P-31, and H -1 solid-state magic angle spinning nuclear magnetic resonance (MAS NMR), F ourier transform Raman spectroscopy (FT-Raman), diffuse reflectance Fourier transform infrared spectroscopy (DRIFTS), and Brunauer-Emmett-Teller (BET) surface area measurements. The activities of the catalysts were determined by an ethanol partial oxidation reaction. V-51 solid-state NMR studies of both series of catalysts indicated the presence of tetrahedral vanadate spe cies at lower loadings, and octahedrally coordinated vanadium species at hi gher concentrations. DRIFTS studies of the catalysts were in conformity wit h NMR studies as the vibrations corresponding to tetrahedral vanadate speci es were observed at low V2O5 loadings and at higher vanadia contents the vi brations corresponding to polymeric decavanadate species were seen. All of the XRD, ESR, V-51 solid-state NMR, FT-Raman, and DRIFTS results indicated weaker interaction of vanadia with zirconia support upon phosphate modifica tion. Activity studies were in agreement with spectroscopic data, as reflec ted in higher ethanol partial oxidation activities of the V2O5/ZrO2 catalys ts.