Burning of p-xylene and solvent during oxidation is the critical side reaction.In this paper the burning mechanism is analyzed and the kinetics model is developed on the basis of the radical chains reaction mechanism.Model parameters were determined by data fitting of the CO x transient response curves.The experimental results showed that, the CO x generating rates increased remarkably with increasing Co/Mn ratio and catalyst concentration.As compared with the main reaction, the burning rate was more sensitive to the change of the ratio of cobalt vs manganese, but less to bromine concentration.
p -Xylene liquid phase oxidation at different temperatures of 186-197 ℃ was carried out to investigate the temperature effect. The kinetics model developed in Part(Ⅰ) was used to fit the data.The rate constants obtained can be well represented by the Arrhenius relationship.The obtained activation energy of different reaction steps ranged from 54 kJ·mol -1 to 93 kJ·mol -1 , among them the activation energy of p -toluic acid to 4-carboxybenzaldehyde step was the highest (92.8 kJ·mol -1 ) and that of 4-carboxybenzaldehyde to terephthalic acid step was the second(84.9 kJ·mol -1 ).They are remarkably higher than the values of the other steps (54.94-67.53 kJ·mol -1 ). This fact showed that oxidation of the second methyl group of p -xylene was more sensitive to the temperature variation than the first one.
