Study On Refining Of The Crude Terephthalic Acid

Purified terephthalic acid is one of the most important raw materials to synthesize polyester.With the development of polymer industry, the methods of refining crude terephthalic acid are improved continuously. A process with mider operating condition and shorter procedure is developed in this work.Electrochemistry method, absorption method and extraction-crystallization method were focused on in this work. 4-CBA was oxidized with Mn3+ prepared by electrolyse, the optimum process condition was studyed, and the content of 4-CBA was reduced from 2200ppm to 1700ppm; 4-CBA was absorbed in its solution by sorbent, compared with PU, PU modified and cation exchange resin, the cation exchange resin modified was able to reduce the content of 4-CBA from 3000ppm to 1770ppm; The solution of sodium sulfite was used to dissolve crude terephthalic acid, and sulfur dioxide got in touch with the solution to react with the terephthalic acid sodium in the solution, the terephthalic acid was deposited as the product, the content of 4-CBA was reduced from 3700ppm to less than 25ppm , and the yield reach 35%, and the final prcess based on the extraction-crystallization method was developed.The content of 4-CBA was analyzed by HPLC, and the solubility of terephthalic acid sodium under the different temperature in water was determined, the optimum content of solution of sodium sulfite was also studyed in this work. The effect of pH value and supersonic on the purity and yield of product was also studyed. The results show that the quality of terephthalic acid refined under the condition of optimum process meets the standard of polymer-grade.