PRODUCTION OF HIGH-PURITY TEREPHTHALIC ACID

摘要

PURPOSE: To provide a process for continuously producing high-purity terephthalic acid having stable quality over a long period, capable of minimizing the initial variation in the catalytic activity caused by the exchange of the catalyst and the quality variation caused by the lowering of the catalytic activity after a long-term operation and effective for avoiding the pause of the reaction operation in the case of the exchange of the catalyst. CONSTITUTION: Crude terephthalic acid obtained by the oxidation of p-xylene is dissolved in an aqueous medium under high temperature and pressure condition and the obtained aqueous solution of crude terephthalic acid is brought into contact with a platinum-group metal catalyst under the supply of hydrogen to purify the crude terephthalic acid and obtain a high-purity terephthalic acid. The above process is carried out by using a column-type reactor having a packed catalyst layer and a space and the space is replenished with a fresh catalyst.