Unravelling the Mechanism and Kinetics of Aerobic Baeyer-Villiger
Oxidation of Cyclohexanone
Abstract
This study explores the aerobic Baeyer-Villiger oxidation of
cyclohexanone into ε-caprolactone using metalloporphyrin and
benzaldehyde, a greener process to replace hazardous concentrated
peroxyacid. The reaction mechanism involves a series of free radical
reactions, identified through in-situ EPR. In this complex
three-component reaction, we developed an intrinsic kinetic model based
on the proposed mechanism. Utilizing a hyperbolic equation, the model
well fits experimental data, describing biomimetic catalytic behavior of
the aerobic Baeyer-Villiger oxidation. The reaction orders for the three
reactants corroborate the kinetic model, with the activation energy of
oxygen (130.27 kJ/mol) surpassing cyclohexanone (94.85 kJ/mol) and
benzaldehyde (40.73 kJ/mol), implying slow initial oxygen activation
while rapid subsequent benzaldehyde oxidation, making oxygen transfer
and activation key steps. This unified approach to elementary reaction,
mechanism, and intrinsic kinetics provides robust forecasts and lays the
groundwork for additional studies, such as side reactions control and
mass transfer enhancement and reactor design.