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 a ccounting for selectivity in mild oxidation and oxidative dehydrogenation o f hydrocarbons, and the mean basicity of oxygen of the selective catalysts. The optical basicity, Lambda, defined as the electron donor power of the c atalyst lattice oxygen, can be calculated for any oxide (A. Lebouteiller an d P. Courtine, J. Solid State Chem., 1998, 137, 94) or more complex formula . Selectivity is accounted for by the difference, Delta I, between the ioni zation potential of the reactant and that of the product. Two linear relati onships are found by plotting Delta I of reactions against the optical basi city Lambda of the respectively selective oxides. The model discriminates b etween paraffinic and olefinic bonds because two distinct lines are obtaine d for each kind of reactant. This quantitative trend could be used as a pre dictive tool to iind new selective materials.