Mitsubishi Gas Chemical Company, Inc.

Toyo Boseki Kabushiki Kaisha

Mizushima Aroma Company, Ltd.

Hiroshi Machida

Fumiya Zaima

Masato Inari

Kazuo Tanaka

Hideaki Fujita

Nobuo Namiki

Yoshio Waguri

Takafumi Abe

Shuji Ebata

Koichi Kida

Hiroshi Ogawa

Shinichi Nagao

Jitsuo Oishi

Rieko Nakano

Ryuji Hasemi

Ko Kedo

Fumio Ohkoshi

Seiji Uchiyama

Emiko Yokose

Kenji Nakaya

Kengi Nakaya

Hiroshi Watanabe

In the washing process of the invention, the solid particles in a high-concentration zone, which is formed in a washing tank by a gravitational sedimentation of solid particles, are continuously washed by a counter-current contact with upward flow of a washing liquid which is fed from the bottom portion of the washing tank. With this process, the impurities in the solid particles are sufficiently removed by a simple apparatus. Since the used washing liquid can be recycled as the disperse medium for feeding the solid particles and as the washing liquid, the amount of used washing liquid to be discharged as the waste from the system is reduced.

Method of washing solid grain

A process for producing a high purity aromatic polycarboxylic acid (APA) by purification of a crude APA comprises: (I) aging a slurry of the crude APA in a first dispersion medium at 180 to 300&#xb0; C. for 10 minutes or longer under stirring; (II) introducing the aged slurry of the APA into a column for substituting dispersion media, bringing the slurry into contact with a second dispersion medium and separating the resultant fluid into a fluid of the first dispersion medium containing impurities and a slurry of the second dispersion medium containing crystals of the high purity APA; and (III) separating the crystals of the high purity APA from the slurry of the second dispersion medium. A high purity APA having excellent hue and particle diameter can be industrially advantageously produced while the construction of the process is simplified and the consumption of energy is decreased.

Process for producing a high purity aromatic polycarboxylic acid

A method for producing high purity terephthalic acid wherein a slurry having an acetic acid solvent and, dispersed therein, crude terephthalic acid crystals which has been prepared by subjecting a p-alkyl benzene to a liquid phase oxidation in a solvent of acetic acid is continuously converted to a water slurry by the mother liquid exchange, and then the resultant water slurry is subjected to a hydrogenation treatment, which comprises introducing the above acetic acid slurry to a tower having a center axis having a plurality of agitating blades at the top thereof, to form a region having a high concentration of terephthalic acid crystals in the tower through the sedimentation of the terephthalic acid crystals, supplying the water for substitution to the bottom of the tower in such a manner to form an upward water flow while generating a revolving flow of the high concentration region by the rotation of the agitation blade, to thereby subject said terephthalic acid crystals and said upward water flow to a counter-flow contact, and taking out the acetic acid from a portion being upper than the supply port for the acetic acid slurry while withdrawing the terephthalic acid crystals having contacted with the upward water flow together with the water for substitution from the tower bottom. The above method allows the substitution of the acetic acid solvent of the acetic acid slurry with water, with a high substitution percentage.

Method for producing high purity terephthalic acid

Process for producing a hydrogenation product of an aromatic carboxylic acid

Dialkylnaphthalene is oxidized to naphthalenedicarboxylic acid in a lower aliphatic carboxylic acid solvent in the presence of a catalyst comprising a cobalt compound, a manganese compound and a bromine compound having an atomic ratio of manganese to cobalt of 0.03 to 0.5. The catalyst is supplied to the oxidation reaction zone so that the total amount of cobalt and manganese is 0.025 to 0.1 gram atom based on 1 gram mol of the dialkylnaphthalene. An oxidation product slurry is subjected to solid-liquid separation when the concentration of the naphthalenedicarboxylic acid in the slurry is 8 to 30% by weight. The process prevents the by-production of benzotricarboxylic acid such as trimellitic acid, thereby drastically reducing the incorporation of heavy metal complexes with trimellitic acid into naphthalenedicarboxylic acid crystals. The process optionally includes the addition of a polymer flocculant, this forming crystal aggregates with a large particle size and facilitating the separation of the crystals from the mother liquor.

Method of producing naphthalenedicarboxylic acid

A process for producing 2,6-naphthalenedicarboxylic acid comprising oxidizing 2,6-dimethylnaphthalene with a gas containing oxygen in a solvent comprising a lower aliphatic carboxylic acid in the presence of a catalyst comprising cobalt, manganese, and bromine, wherein the total amount of cobalt and manganese in the catalyst is 50 to 300 mg atom per 1 g mol of 2,6-dimethylnaphthalene, a ratio by g atom of manganese to cobalt in the catalyst is 20:1 to 4:1, and the oxidation is conducted at a temperature of 200 to 250.degree. C.; and a process as described above, wherein a mother liquor which is obtained from a slurry of a product of the oxidation via a step of solid-liquid separation is recyled to a step of oxidation after heat treatment at a temperature of 150.degree. C. or higher. In accordance with the processes, accumulation of substances which affect the oxidation adversely is prevented. Moreover, a large fraction of a mother liquor of oxidation can be recycled without decrease in the yield of the reaction, and the catalyst components and the solvent components in the mother liquor of oxidation can be utilized efficiently.

Process for producing 2,6-naphthalenedicarboxylic acid

A process for the production of high-purity dimethyl 2,6-naphthalenedicarboxylate, which comprises esterifying 2,6-naphthalenedicarboxylic acid obtained by liquid phase oxidation of 2,6-dialkylnaphthalene with molecular oxygen in the presence of an oxidation catalyst, with methanol and then purifying a crude ester formed by the esterification, the crude ester being purified in the presence of an aromatic hydrocarbon as a solvent, in which impurities contained in a reaction product obtained by the esterification of 2,6-naphthalenedicarboxylic acid prepared by the liquid phase oxidation of 2,6-dialkylnaphthalene are effectively removed with simple procedures, oxidation catalyst metals are recovered, a crystal of naphthalenedicarboxylic acid formed by the oxidation of dialkylnaphthalene and/or its oxide derivative can be easily separated, and the oxidation catalyst to be brought into the step of producing dimethyl naphthalenedicarboxylate is recovered in the process of the production of naphthalenedicarboxylic acid and effectively used in the process of the production of naphthalenedicarboxylic acid.

Processes for the production of high-purity dimethyl 2,

A process for producing 2,6-naphthalenedicarboxylic acid (NDCA) is disclosed. This process comprises oxidizing a 2,6-dialkylnaphthalene with a gas containing molecular oxygen in a solvent containing a lower aliphatic carboxylic acid in the presence of a catalyst comprising heavy metal compounds and a bromine compound, and is characterized in that an ester mixture containing dimethyl 2,6-naphthalenedicarboxylate (NDCM) is added to the oxidation reaction. The low boiling distillate, the high boiling still residue, and the residue of the mother liquor after recrystallization, occurring during purification of the crude NDCM, are also used as additives to the oxidation reaction. According to the present invention, NDCA with large particle size and bulk density can be obtained. Therefore, solid-liquid separation of the crystals, drying of the separated crystals and transportation of the dried crystals are made easier.

Process for producing 2,6-naphthalenedicarboxylic acid and ester thereof

A process for producing dimethyl 2,6-naphthalene-dicarboxylate by reacting 2,6-naphthalene-dicarboxylic acid with methanol which comprises effecting the reaction at 200.degree. to 350.degree. C. in the presence of trimethyl trimellitate as an essential solvent and optionally, at least one solvent selected from methyl benzoate, methyl toluate and dimethyl o-phthalate preferably by at least two-stage continuous reaction method. The above process is capable of enhancing the rate of esterification reaction and producing purified objective product in high yield for a long period of time in a stable operation without causing any operational trouble such as corrosion and clogging the production equipment.

Process for producing dimethyl 2,6-naphthalene-dicarboxylate

A process for production of 2,6-dimethylnaphthalene is disclosed; comprising the steps: (1) an acylation step where 2,4-dimethylisobutyrophenone is produced from m-xylene, propylene and carbon monoxide: (2) a hydrogenation step where the carbonyl group of the above 2,4-dimethylisobutyrophenone is hydrogenated: and (3) a dehydrogenation and cyclization step where the above hydrogenated product is subjected to dehydrogenation and cyclization to produce the desired 2,6-dimethylnaphthalene. The process enables efficiently producing high quality or high purity 2,6-dimethylnaphthalene.

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Okayama, Japan

Hiroshi Machida