Process for producing aromatic polycarboxylic acid

Abstract

A process for producing a polycarboxylic acid which comprises performing liquid phase oxidation of polyalkyl-substituted aromatic aldehyde and / or oxide derivative of polyalkyl-substituted aromatic aldehyde as raw material for oxidation with molecular oxygen at two stages in water solvent in the presence of a catalyst comprising bromine or both bromine and a heavy metal(s) at a temperature of 180 to 280 ° C., thereby producing trimellitic acid or pyromellitic acid, wherein said liquid phase oxidation is performed in a continuous operation at the first stage and in a continuous operation or in a batch operation at the second stage and a total amount of bromine in said catalyst is divided to add separately at each the first stage and the second stage.

Description

[0001] 1. Field of the Invention[0002] The present invention relates to a process for producing an aromatic polycarboxylic acid by liquid phase oxidation of polyalkyl-substituted aromatic aldehyde and / or oxide derivative thereof, and specifically, to process for producing trimellitic acid or pyromellitic acid.[0003] 2. Prior Art[0004] As industrial processes for producing trimellitic acid, a process comprising air-oxidizing psuedocumene as a raw material in an acetic acid solvent in the presence of a cobalt-manganese-bromine catalyst and a process comprising air-oxidizing 2,4-dimethyl benzaldehyde, 2,5-dimethyl benzaldehyde and 3,4-dimethyl benzaldehyde or 2,4-dimethyl benzoic acid, 2,5-dimethyl benzoic acid and 3,4-dimethyl benzoic acid of oxide derivative thereof as raw materials in water solvent in the presence of a catalyst containing bromine and manganese or cerium are widely known. As industrial processes for producing pyromellitic acid, a process comprising air-oxidizing dure...

AI Technical Summary

Benefits of technology

[0029] The reaction can be performed in a continuous operation at the first stage and in a continuous operation or in a batch operation at the second stage. Particularly, in order to display the advantageous effects of the present invention, continuous two stage type oxidation process to perform the reaction in a continuous operation at both the first stage and the second stage is most preferable.

[0030] After the completion of oxidation, the reaction liquid is subjected to known purifying treatments such as filtration and distillation, whereby trimellitic acid or pyromellitic acid can be obtained as a product.PREFERRED

Problems solved by technology

In contrast, oxidation of psuedocumene has a defect that the metal catalyst forms a salt with trimellitic acid of a product to deposit, so that activity of the catalyst is degraded and the reaction does not readily progress.

The process for producing trimellitic acid disclosed in Japanese Patent No. 2939346 comprising air-oxidizing psuedocumene in an acetic acid solvent has defects that the operation is complicated since it is necessary to control carefully and change a temperature and a water concentration in the reaction liquid; a high price catalysts such as cobalt zirconium and cerium are used; there is combustion of acetic acid as solvent and a recovery equipment of acetic acid as solvent is necessary.

The process for producing pyromellitic acid disclosed in Japanese Patent Publication No.7-55917 comprising air-oxidizing durene in an acetic acid solvent is not economical from the aspects that a high price is imposed on durene of the raw material since it is difficult to obtain it and the yield of pyromellitic acid is about 60 mol% since the oxidation reaction is more difficult than that in the process for producing trimellitic acid comprising air-oxidizing psuedocumene in an acetic acid solvent.