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 used as supports for preparing a series of catalysts with vanadia contents varying between 1-25 wt.%. The supports and the catalysts were characterized by employing V-51 and H-1 solid-state MAS NMR, diffuse reflectance FT-IR, and BET surface area measurements. The partial oxidation activities of the catalysts were tested using ethanol oxidation as the model reaction. V-51 solid-state NMR studies of the calcined catalysts showed the peaks corresponding to the presence of polymeric tetrahedral vanadia species at low vanadia loadings and V-51 chemical shifts corresponding to amorphous V2O5 like phases 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 catalysts indicated the vibrations corresponding to V=O bonds of V2O5 agglomerates, in the catalysts with high vanadia loadings. Acetaldehyde was obtained as the major product with traces of ethylene, ether, acetic acid, ethyl acetate, and COx during the ethanol partial oxidation activity studies of mixed oxide supported vanadia catalysts. (C) 2001 Elsevier Science B.V. All rights reserved.