KINETIC MODELS FOR LIQUID-PHASE CATALYTIC OXIDATION OF TOLUENE TO BENZOIC ACID WITH PURE OXYGEN

The liquid phase oxidation of toluene to benzoic acid by pure oxygen has been performed in a bubble reactor by using cobalt acetate tetrahydrate as catalyst. The influence of the oxygen partial pressures on the reaction kinetics were first investigated, and the results showed that the influence was neglectable in the high oxygen pressure range (>0.5 MPa) under 155°C. Thereby, the reaction rates in the oxidation using pure oxygen are independent of the oxygen partial pressure and expressed as the first order to liquid reactants. Based on a kinetic scheme that involves both benzyl alcohol and benzaldehyde, the kinetic models can well describe the reaction process. Furthermore, the results indicated that the production of benzyl alcohol is much slower than its consumption to form benzaldehyde and the scheme can be further simplified to a kinetic equation, which involves only benzaldehyde as intermediate. The simplified reaction scheme also well describes the reaction, and, thus, the derived kinetic models agree well with the experimental data. The reaction constants follow the Arrhenius law. The estimated activation energies are in the range from 92.63 kJ·mol−1 to 67.81 kJ·mol−1.