Normalization by Oxygen Uptake of the Rates of Oxidative Dehydrogenation of Methanol and Ethanol

摘要

Silica-supported, V-substitued polyoxometalates containing V_1, V_3 and V_(14) ensembles were characterized by the oxygen uptake protocol developed by Oyama and co-workers. Rates of methanol and ethanol oxidation catalyzed by these samples scaled well with the number of exposed vanadiums and almost as well with he number of oxygens taken up. The results confirm the weak dependence on the local concentration of redox centers of the catalytic oxidative dehydrogenations. A slight, residual variation in turnover frequencies when normalized by oxygen uptake is interpreted as an adjacency dependence in the number of oxygen vacancies created by the reduction step or, equivalently, as an adjacency dependence in the average degree of reduction of the samples.