MX和PX混合氧化工艺条件研究

以间二甲苯(MX)和对二甲苯(PX)为原料,使用500 mL高压氧化反应釜MX和PX混合氧化,制备粗混合苯二甲酸(TA-IA)。考察了催化剂中促进剂溴的含量、空气流速、反应温度和压力、MX与PX的质量比、体系含水量、溶剂比对MX和PX混合氧化反应的影响,并对最佳工艺条件下的产物TA-IA进行加氢精制。结果表明:最优混合氧化工艺条件为空气流速2 000～2 500 mL/min,温度187℃,压力1. 1 MPa,醋酸∶二甲苯的质量比为10∶1、体系含水质量分数7%,MX∶PX质量比69∶31,四溴乙烷为促进剂,三元催化体系中钴含量为545μg/g、锰含量为250μg/g,溴含量为955μg/g,在此工艺条件下反应物的转化率为99. 92%,目标产物TA-IA的收率为88. 81%;所得混合氧化产物在反应温度286℃、反应压力7. 86 MPa、TA-IA浆料质量分数为25%的条件下进行加氢精制,加氢精制后产物中对羧基苯甲醛和间羧基苯甲醛的总含量为2μg/g。

Study on MX and PX mixed oxidation conditions

Coarse mixing phthalic acid(TA-IA)was prepared by using m-xylene(MX)and p-xylene(PX)as raw material on a 500-mL high-pressure oxidation reactor via mixed oxidation.The effects of the bromine content of catalyst promoter,air velocity,reaction temperature and pressure,MX-and-PX mass ratio,water content of reaction system and solvent ratio on the MX and PX mixed oxidation were investigated.And the product TA-IA prepared under the optimized process conditions was subjected to hydrofining.The results showed that the mixed oxidation conditions were optimized as followed:air velocity 2 000-2 500 mL/min,temperature 187℃,pressure 1.1 MPa,acetic acid-and-xylene mass ratio 10 1,7%water in the reaction system by mass fraction,MX-and-PX mass ratio 69 31,tetrabromoethane promoter,a ternary catalyst system of 545μg/g cobalt,250μg/g manganese and 955μg/g bromine;the conversion rate of the reaction system was 99.92%and the yield of the target product TA-IA was 88.81%under the optimized conditions;and the total content of 4-carboxybenzaldehyde and 3-carboxyl benzaldehyde was 2μg/g in the obtained product when the obtained mixed oxidized product was subjected to the hydrofining under the conditions as followed:reaction temperature 286℃,reaction pressure 7.86 MPa,25%TA-IA slurry by mass fraction.