Kinetic Model of Ethyl Benzene Oxidation Catalysed by Manganese Salts

A practical model was developed for liquid-phase Mn3+-catalysed oxidation of ethyl benzene by O2. The model describes time profiles of concentrations of ethyl benzene and two intermediate oxidation products (methyl phenyl carbinol and acetophenone). The kinetic model of acetophenone oxidation to benzoic acid was also obtained. The influence of the main products of the ethyl benzene oxidation on the reaction kinetics is discussed. It was established that the addition of ethyl benzene hydroperoxide does not affect the reaction rate; the addition of methyl phenyl carbinol inhibits the reaction. The addition of acetophenone promotes the reaction and neutralises the inhibiting effect of methyl phenyl carbinol. The proposed reaction mechanism includes free-radical ethyl benzene oxidation. The process is initiated by the acetophenone interaction with Mn3+ ion, and the chain is propagated due to the hydroperoxide interaction with ethyl benzene. The chain termination is quadratic. The length of the oxidation chain was calculated. The inhibition is caused by the manganese bonding to form an inactive complex. The obtained system of differential rate equations adequately describes the process.