Mitsubishi Gas Chemical Company, Inc.

Other

Toyobo Co., Ltd.

Mizushima Aroma Company, Ltd.

Nirou Hoshishima

Fumiya Zaima

Hideaki Fujita

Fumio Ohkoshi

Ikuo Tsuboi

Kazutoshi Uozumi

Provided is a simple filtering operation method capable of conducting a filtering operation without clogging in a ceramic filter for a long period of time, in the operation of filtering fine crystals of terephthalic acid in an oxidation reaction mother liquor obtained in a process of terephthalic acid production by a cross-flow filtration using the ceramic filter. The present invention can be accomplished by conducting an operation for filtering the fine crystals and a back washing operation with a filtrate while maintaining a flowing circulation operation of the oxidation reaction mother liquor under predetermined conditions.

Crossflow type filtering operation method using ceramic filter

The present invention relates to a multi-stage crystallization process which comprises the steps of feeding a solution of terephthalic acid or a slurry (raw slurry) containing terephthalic acid partially precipitated to a first crystallization vessel to precipitate the terephthalic acid therein; and feeding a slurry (crystallization slurry) containing the thus precipitated terephthalic acid sequentially to second and subsequent crystallization vessels, wherein while continuously supplying a cleaning solvent to a delivery conduit connecting the former-stage crystallization vessel and the next latter-stage crystallization vessel to each other, the crystallization slurry is fed through the delivery conduit. There is provided a multi-stage crystallization process using a solution of terephthalic acid or a slurry containing terephthalic acid partially precipitated as a raw material in which even when the process is operated for a period as long as several months, the delivery conduit is free from occurrence of clogging.

Method of crystallization

There is disclosed a process for continuously producing an aromatic carboxylic acid comprising the steps of (A) subjecting a poly-alkyl aromatic hydrocarbon to a liquid-phase oxidation by continuously supplying an oxidation reactor with said hydrocarbon, a catalyst, a reaction accelerator, acetic acid containing water and a gas containing molecular oxygen; (B) continuously taking out from the oxidation reactor, the reaction products containing aromatic carboxylic acids, and separating the same into crude aromatic carboxylic acids and acetic acid containing water; and (C) continuously taking out from the oxidation reactor, the oxidative reaction exhaust gas containing evaporated acetic acid containing water, introducing the above gas in a condenser, and condensing the above evaporated acid, wherein acetic acid containing water is supplied to an oxidative reaction exhaust gas inlet line leading to the condenser. The process enables to almost perfectly eliminate the occurrence of troubles in the condenser which is caused by solid matters accompanying the oxidative reaction exhaust gas, and to proceed with stable operation of aromatic carboxylic acid production equipment.

Process for producing aromatic carboxylic acid

Growing community of inventors

Okayama, Japan

Nirou Hoshishima