煤酸异构化制对苯二甲酸

进行了煤氧化产物煤酸（水溶酸WSA）钾在催化剂碳酸镉的存在下，异构化制对苯二甲酸(TPA)的研究。主要考察了催化剂用量、二氧化碳初压、反应温度和反应时间对TPA产率的影响。结果表明，在催化剂存在下煤酸可以转化成TPA。单独煤酸钾异构化时，较佳反应条件：温度430 ℃～450 ℃，压力4.0 MPa，催化剂CdCO3用量4%，反应时间2 h。煤酸钾与苯甲酸（BA）钾混合异构化时，较佳反应条件与单独煤酸钾时基本相同。单独煤酸钾在较佳条件下异构化时，粗TPA产率达34%左右，相当于根据其中有效成分苯多羧酸（BPCA）计算的理论产率的75%左右，选择性较好。煤酸钾加苯甲酸钾在较佳条件下异构化时,粗TPA产率可达68%，扣除假定BA自身岐化生成TPA理论产量之后，则煤酸的TPA产率高达70%，比煤酸单独异构化TPA产率(34%)高1倍。粗TPA经精制可得纯度99%以上的精TPA。

SYNTHESIS OF TEREPHTHALIC ACID BY ISOMERIZATION OF COAL ACID

Terephthalic acid can be obtained in the presence of a catalyst CdCO3 by isomerization of potassium salt of coal acid (water-soluble acids, WSA) produced from coal oxidation. Effects of the amount of catalyst, initial pressure of CO2, reaction temperature and reaction time were investigated. It was confirmed that WSA can be converted to terephthalic acid in the presence of a catalyst. In case of isomerizing the potassium salt of coal acids alone, the optimum conditions of isomerization were found to be: temperature 430 ℃～450 ℃, initial pressure of CO2 4.0 MPa, catalyst CdCO3 4% and reaction time 2 h. Such optimum conditions were similar to those of the isomerization by a mixture of potassium coal acids (WSA) and potassium benzoic acid (BA). The yield of crude TPA by isomerization of potassium salt of coal acid was about 34%, which was equivalent to 75% of BPCA(theoretical yield), and was the effective composition of WSA. It has shown that the selectivity was good. The yield of crude TPA was about 68% if isomerization was carried out with a mixture of potassium salts of coal acid and benzoic acid at its optimum conditions. The yield of TPA was as high as 70% after being deducted from the theoretical yield of BA dismutation, and about two times of WSA isomerization alone.The purity of the refined TPA was ≥ 99%.