Synthesis, characterization and ethanol partial oxidation studies of V2O5 catalysts supported on TiO2-SiO2 and TiO2-ZrO2 sol-gel mixed oxides

Sol-gel derived titania based mixed oxides TiO2-SiO2 and TiO2-ZrO2 were use d as supports for preparing a series of catalysts with vanadia contents var ying between 1-25 wt.%. The supports and the catalysts were characterized b y employing V-51 and H-1 solid-state MAS NMR, diffuse reflectance FT-IR, an d BET surface area measurements. The partial oxidation activities of the ca talysts were tested using ethanol oxidation as the model reaction. V-51 sol id-state NMR studies of the calcined catalysts showed the peaks correspondi ng to the presence of polymeric tetrahedral vanadia species at low vanadia loadings and V-51 chemical shifts corresponding to amorphous V2O5 like phas es were observed in the catalysts with high V2O5 contents. After outgassing the catalysts, a broadening of the peaks was observed indicating a change in the coordination environment around vanadium. DRIFTS studies of the cata lysts indicated the vibrations corresponding to V=O bonds of V2O5 agglomera tes, in the catalysts with high vanadia loadings. Acetaldehyde was obtained as the major product with traces of ethylene, ether, acetic acid, ethyl ac etate, and COx during the ethanol partial oxidation activity studies of mix ed oxide supported vanadia catalysts. (C) 2001 Elsevier Science B.V. All ri ghts reserved.