Modification of kinetic parameters by action of oxygen spillover in selective oxidation of isobutene to methacrolein

A kinetic study of the oxidation of isobutene to methacrolein was carried out by varying the reaction temperature and the oxygen and isobutene partial pressure. Catalysts were prepared by mechanically mixing, in different propositions, alpha-Sb2O4 and MoO3, synthesized separately. Pure oxides and their mechanical mixtures were tested under identical experimental reaction conditions. The presence of alpha-Sb2O4 changes the reaction orders and the activation energy of the reaction. The changes in the kinetic parameters are explained by a remote control mechanism via spillover oxygen (RCM). A new model which incorporates both the mechanism of site creation (via RCM) and the catalytic reaction at the thus created (or controlled) active sites fits well the experimental data. All the parameters of the new model have a precise physical meaning.