A Study On The Kinetics Of Liquid Phase Oxidation Of Toluene

Both benzoic acid and benzaldehyde are important organic raw materials in the industry. Benzoic acid can be used to produce phenol, caprolactam, terephthalic acid, while benzaldehyde is the raw material to produce Malachite Green, lauraldehyde, lauric acid. Liquid-phase oxidation of toluene by air is a green process to produce benzoic acid and benzaldehyde because of mild reaction condition, high yield and safety.This work was to study the liquid-phase air oxidation of toluene in a in a stirred tank reactor by using cobalt/manganese/nickel in naphthenic acid as catalyst and benzaldehyde as initiator. The experiments were conducted to investigate the catalytic activity of catalyst and to determine the content and metal ratio of catalysts under experimental condition: 160°C of reaction temperature, 0.65MPa of pressure, 0.06m~3/h of air input, 500rpm of stirred rate, 4 h of reaction time. The experimental results of different catalyst contents showed that 150ppm of catalyst content offered the higher conversion of toluene and selectivity. 3:1 of manganese/nickel ratio in catalyst could lead to higher conversion of toluene and selectivity under 150ppm of catalyst content. Therefore an optimal catalyst can be proposed to be 110ppm cobalt/30ppm manganese/10ppm nickel because of higher conversion and selectivity.In order to clarify the reaction mechanism of liquid-phase oxidation of toluene, the initiation and transfer of chain reaction, and effects of intermediate product on oxidation reaction, it is necessary to study the reaction kinetics of toluene oxidation. The experiment of different stirred rate was carried out to eliminate the influence of mass transfer and mixing. Then under reaction temperature of 155, 160, 165, 170°C , the variation of reactant and product concentration with reaction time was investigated by using the obtained catalyst system. Kinetic curves of liquid-phase oxidation of toluene at different reaction temperatures are gained. The oxidation reaction behavior of toluene was discussed and a suitable reaction network and the kinetic modeling was proposed.