Process for producing highly purified benzenedicarboxylic acid i

Details Process for producing highly purified benzenedicarboxylic acid i Process for producing highly purified benzenedicarboxylic acid i

1993-10-27

1994-10-25

Shippen, Michael L.

Organic compounds -- part of the class 532-570 series

Organic compounds

Carboxylic acids and salts thereof

562487, C07C 5116

Patent

active

053591330

ABSTRACT:
Disclosed herein is a process for producing highly purified benzenedicarboxylic acid isomers without an additional catalytic reductive purification step, which comprises (a) an oxidation step wherein xylene isomer is oxidized with molecular oxygen or molecular oxygen containing gas in the presence of a catalyst system composed of cobalt, manganese, bromine and at least one selected from nickel, chromium, zirconium and cerium in lower aliphatic carboxylic acid; and (b) an extraction/post-oxidation step wherein the oxidation product is crystallized to give cake of crude benzenedicarboxylic acid isomer, the cake is reslurried by adding lower aliphatic carboxylic acid solvent thereto followed by heating in order to extract impurities contained therein into the solvent, and the resulting slurry is oxidized with said catalyst system at a temperature of 2.degree.-80.degree. C. lower than that of said heating, each of said oxidation and extraction/post-oxidation being carried out once or twice, provided that any one or both of said steps should be carried out twice. According to the invention, the solvent employed to extract impurities is recycled from the subsequent oxidation steps.

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