Reaction mechanism and kinetics for the liquid-phase catalytic oxidation of meta-xylene to meta-phthalic acid

A detailed radical chain elementary reaction mechanism for the liquid-phase catalytic oxidation of meta-xylene to meta-phthalic acid catalyzed by cobalt acetate and manganese acetate and promoted by hydrogen bromide was proposed. Using several reasonable assumptions a simple fractional-like kinetic model was derived from the assumed reaction mechanism. Several batch oxidation experiments were carried out to study the oxidation kinetics. The experiments included three values of the initial concentration of meta-xylene and four values of reaction temperature. The developed model parameters were determined in a nonlinear optimization, minimizing the difference between the simulated and experimental time evolutions of the product compostions obtained in a batch oxidation reactor, where the gas and liquid phases were well mixed. The experimental results cannot be interpreted by the empirical n-th order kinetics, but can be interpreted by the kinetic model proposed in this work. It means the kinetic model proposed in this work reveals the reaction mechanism. (C) 2008 American Institute of Chemical Engineers.