Hledat publikace

SBA-15 and fumed-silica-supported vanadium catalysts prepared by impregnation to contain 1, 5 and 10 wt% of vanadia were characterized by XRF, N2-BET, SEM, H2-TPR, DR UV–vis and Raman spectroscopy to determine the key vanadium species present in these catalysts. These catalysts were then used in the oxidation of ethanol by oxygen at 250 and 300 °C. The comparison of the catalytic performances of individual catalysts with their physico-chemical characteristics led to the conclusion that oligomeric tetrahedrally coordinated vanadium species have the highest potential for the selective oxidation of ethanol reaching high intrinsic catalytic activity and high selectivity to acetaldehyde. They differ significantly from catalysts with a high population of monomeric species, which exhibit low activity, especially at 250 °C, and high selectivity to ethylene as a product of ethanol dehydration. The observed changes in the isothermal dependence of selectivity to ethene on the conversion degree were ascribed to the auto-inhibition effect of water vapor.