PURPOSE: To recover methyl acetate in the form of acetic acid, produced as a by-product in the preparation of an aromatic carboxylic acid using acetic acid as a solvent, economically, by concentrating a part of the column top liquid of the distillatin column for the separation of water and acetic acid, hydrolyzing the concentrated liquid, and contacting with exhaust gas from the oxidation reactor, etc.
CONSTITUTION: In the preparation of a carboxylic acid by the catalytic oxidation of an aromatic compound having alkyl substituent group in acetic acid under specific condition, the reaction mixture 2 extracted from the oxidation reactor 1 is separated into solid and liquid 3, and the mother liquor 4 of the reaction is evaporated. The evaporated component 7 is supplied to the first distillation column 8, and water and methyl acetate are obtained from the top 10 of the column. A part of the distillate is condensd 11 and recycled 12 to the distillation column 8, and the remaining part 13 is supplied to the second distiallation column 14 and concetrated. The distillate 16 obtained from the top of the column is condensed 17. A part of the condensate is recycled to the distillation column 14, and the remaining part 19 is hydrolyzed with a solid acid catalyst, brought into contact 22 with the exhaust gas from the reactor 1 or the crystallizer, and recycled to the distillation column 8. The by-produced methyl acetate can be recovered economically by this process without consuming additional energy.
MORITA KOUICHI
NAKAJIMA YASUE
