A kinetic study of liquid-phase catalytic oxidation of styrene to benzaldehyde with Wilkinson complex

Liquid-phase homogeneous catalytic oxidation of styrene with Wilkinson complex by molecular oxygen in toluene medium gave selectively benzaldehyde and formaldehyde as the primary products. Higher temperatures and styrene conversions eventually led to acid formation due to co-oxidation of aldehyde.A reaction induction period and an initiation period, typical of free-radical reactions, characterized the oxidation process. The effects of temperature and catalyst and styrene concentrations on the conversion of styrene to benzaldehyde and acid formation have been studied. The optimum reaction parameters have been determined as a styrene-to-solvent mole ratio of 0.5, a catalyst-to-styrene mole ratio of 5.0 X lo4, and a reaction temperature of 75 "C. A reaction scheme based upon free-radical mechanism yielded a pseudo-first-order model which agreed well with the observed kinetic data in the absence of co-oxidation of aldehyde. A second-order model was found to fit the experimental data better in the case of aldehyde conversion to acid.