Proposal of a new kinetic model based on the remote control mechanism to fit experimental data during the selective oxidation of isobutene to methacrolein on biphasic catalysts

摘要

A new kinetic model based on the classical Mars-van Krevelen mechanism is proposed. The new model incorporates both the mechanism of site creation (via a remote control) and the catalytic reaction at the thus created (or controlled) active site. The model has been tested in the selective oxidation of isobutene to methacrolein on catalysts made of mechanical mixtures of α-Sb_2O_4 + MoO_3. The good fitting of the model with the experimental results shows that the remote control mechanism can explain the difficulties to represent the kinetics of allylic oxidation reactions by the traditional Mars-van Krevelen mechanism. The fraction of the surface of MoO_3 which selectively realises the oxidation via the oxidoreduction process depends on the degree of irrigation of MoO_3 by spillover oxygen produced on α-Sb_2O_4 and cannot be considered as constant. The possible use of the model for further progress in the kinetic description of selective oxidation reactions is briefly outlined.