RECOVERY OF TEREPHTHALIC ACID

摘要

PROBLEM TO BE SOLVED: To provide a method for recovering terephthalic acid by which a highly pure terephthalic acid is continuously produced. SOLUTION: This method for recovering terephthalic acid by dissolving a crude terephthalic acid obtained by subjecting p-xylene to a liquid phase oxidation, in water at a temperature at which the terephthalic acid can be completely dissolved, bringing the obtained aqueous solution into contact with a group VIII metal catalyst to purify the terephthalic acid and recovering the purified terephthalic acid dissolved in the aqueous solution by using a flash vaporization is carried out by regulating the cperation temperature ranges of each crystallizing vessel so as to satisfy the approximation formula y=266 exp(-0.61x)±5 [(x) is a value obtained by dividing 1 by the total number of steps and multiplying the step number to the divided value; (y) is a crystallizing vessel-operating temperature ( deg.C) with the proviso that 140<=(y)<=240] to provide the terephthalic acid crystal containing a small amount of impurities.