A new concept related to selectivity in mild oxidation catalysis of hydrocarbons: the optical basicity of catalyst oxygen

Semi-empirical correlations are drawn between properties of the gas phase accounting for selectivity in mild oxidation and oxidative dehydrogenation of hydrocarbons, and the mean basicity of oxygen of the selective catalysts. The optical basicity, Lambda, defined as the electron donor power of the catalyst lattice oxygen, can be calculated for any oxide (A. Lebouteiller and P. Courtine, J. Solid State Chem., 1998, 137, 94) or more complex formula. Selectivity is accounted for by the difference, Delta I, between the ionization potential of the reactant and that of the product. Two linear relationships are found by plotting Delta I of reactions against the optical basicity Lambda of the respectively selective oxides. The model discriminates between paraffinic and olefinic bonds because two distinct lines are obtained for each kind of reactant. This quantitative trend could be used as a predictive tool to iind new selective materials.