Study Of The Liquid Phase Oxidation Of 2,6-dimethylnaphthalene

2,6-naphthalenedicarboxylic acid is an important raw material in the polyester industry.At present,2,6-naphthalenedicarboxylic acid is mainly produced by liquid phase catalytic oxidation of 2,6-dimethylnaphthalene,with acetic acid being solvent,cobalt/manganese/bromide being catalyst and air being oxidant.The oxidation process is a typical free radical chain reaction.In this paper,research and analysis of the oxidation of 2,6-dimethylnaphthalene is conducted.In order to determine the appropriate solvent ratio in the kinetic experiments,solubility data of 2,6-dimethylnaphthalene are essential.Experiments are conducted from 30? to 80? in aqueous acetic acid at solvent compositions covering industrial operating range.Experimental solubilities are correlated by ?-h equation and NRTL equation so as to calculate and predict solubilities of 2,6-dimethylnaphthalene at different temperatures.In this paper,the main and side reaction schemes of the 2,6-dimethylnaphthalene oxidation process are proposed.Kinetics experiments are carried out in a batch reactor.Several analytical methods are used together to determine the concentration of each intermediate and by-product,which is a significant base for the kinetics study.The effects of reactant concentration,temperature and catalyst concentration on the oxidation are investigated.It shows that reaction rate increases with decreasing reactant concentration.Since order of side reactions are higher than that of the main reactions,low reactant concentration is better for main reactions.Experimental data are correlated by hyperbolic kinetics model and kinetic parameters are obtained.The activation energies of main reactions are between 45?70kJ·mol-1,and those of side reactions are between 70?120kJ·mol-1,most of which are above 70kJ·mol-1.Thus,low temperature is favored for main reactions.The effect of catalyst concentration to reaction rate is almost linear at given range,both for main and side reactions.On the basis of solubility data and kinetics data,mathematic models of 2,6-dimethylnaphthalene industrial oxidation reactor is developed,with which reaction results are calculated.Besides,industrial continuous reactor for 2,6-dimethylnaphthalene to 2,6-naphthalenedicarboxylic acid by liquid phase catalytic oxidation is designed,and the effects of solvent ratio,pressure and catalyst concentration on the reaction process are comprehensively compared,...