Asahi Kasei Kogyo Kabushiki Kaisha

Hiroshi Takeuchi

Masatoshi Tanouchi

Tetsuya Miyake

Kazuki Ban

Maomi Seko

Shinsaku Ogawa

Yoshiyuki Asahina

Tatsushi Saeki

Yoshiaki Yamazaki

A process for recovering heavy metal ions or heavy metal ions and halogen values from a solution comprising a lower aliphatic monocarboxylic acid, which comprises the steps of:

Process for recovering heavy metal ions or heavy metal ions and halogen

An improved process for the production of a high purity terephthalic acid by a liquid phase oxidation reaction of para-xylene by means of molecular oxygen or a molecular oxygen-containing gas in an aliphatic monocarboxylic acid solvent in the presence of a cobalt-manganese-bromine catalyst system, characterized in that as the cobalt-manganese-bromine catalyst system there is used a catalyst system of a specific composition at a specific concentration, and the liquid phase oxidation reaction is effected in the presence of acetaldehyde in addition to the cobalt-manganese-bromine catalyst system under relatively mild temperature (170.degree.-190.degree. C.) and pressure conditions while maintaining the water concentration in the reaction system at a specified low level. The terephthalic acid produced according to the process of the present invention is of so high a quality that it can be used for the direct production of a polyalkylene terephthalate from the acid and an alkylene glycol or ethylene oxide, which direct production does not need the preparation of an intermediate such as a methyl ester of terephthalic acid.

Process for the production of a high purity terephthalic acid

This invention relates to an improved process for recovering highly pure terephthalic acid crystals from a suspension containing terephthalic acid product obtained by the liquid phase oxidation of para-substituted aromatic compounds in the presence of oxidizing catalyst. The improvement comprises bringing said suspension into continuous countercurrent contact with ascending hot acetic acid containing water in a single tower under the conditions of specified temperature, specified ascending rate of the acetic acid containing water and specified residence time of the suspension, to replace the mother liquor of the suspension with said acetic acid, and recovering the mother liquor as an overflow, while recovering terephthalic acid as an underflow in the form of suspension of highly purified crystals and, if necessary, allowing the suspension to stay in a stirring tank.

Process for recovering terephthalic acid

A process for precipitating a crystalline diamine dicarboxylate which comprises dissolving the corresponding dicarboxylic acid in the aqueous liquid containing diamine dicarboxylate and adding the sufficient amount of the corresponding diamine to precipitate the desired product by neutralization.

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Nobeoka, Japan

Hiroshi Takeuchi