Process for producing pyromellitic acid

Abstract

A process for producing pyromellitic acid which comprises oxidizing 2,4,5-trimethylbenzealdehyde and/or its oxidized derivative in the presence of a catalyst containing iron, manganese and bromine, or additionally containing zirconium or cerium continuously or semi-continuously using aqueous acetic acid solvent and 0.05-2% by weight of bromide ion. The catalyst used in the present invention has high activity, and the catalyst solution has low corrosive because the reaction is performed at low bromide concentration by using a solvent of aqueous acetic acid. So pyromellitic acid is produced industrially advantageously in high yield continuously or semi-continuously which has been a major difficulty up to now.

What is claimed is:  
     
         1 . A process for producing pyromellitic acid which comprises oxidizing 2,4,5-trimethylbenzaldehyde and/or its oxidized derivative in the presence of a catalyst containing iron, manganese and bromine, and which may additionally contain zirconium or cerium continuously or semi-continuously by using aqueous acetic acid solvent.  
     
     
         2 . A process for producing pyromellitic acid according to  claim 1 , wherein 2,4,5-trimethylbenzealdehyde and/or its oxidized derivative is oxidized continuously at 180-240° C. using an acetic acid solvent containing 10-90% by weight of water.  
     
     
         3 . A process for producing pyromellitic acid according to  claim 2 , wherein total concentration of metal atom of iron, manganese, zirconium and cerium is 0.03-2% by weight in solvent, and atomic ratio of bromide ion to total of the metal is 0.5-15.  
     
     
         4 . A process for producing pyromellitic acid according to  claim 2 , wherein the catalyst has on the base of total metals, a manganese content of 55-99.9% by weight, an iron content of 0.1-15% by weight, zirconium content of 0-15% by weight and cerium content of 0-15% by weight.  
     
     
         5 . A process for producing pyromellitic acid according to  claim 2 , wherein iron content is 1-200 ppm, zirconium content is 0-500 ppm and cerium content is 0-500 ppm in solvent.  
     
     
         6 . A process for producing pyromellitic acid according to  claim 1 , wherein 2,4,5-trimethylbenzaldehyde and/or its oxidized derivative is oxidized semi-continuously at through-put of 0.6-1.3 mol/hr-kg.  
     
     
         7 . A process for producing pyromellitic acid according to  claim 6 , wherein the catalyst has on the base of basis of total metals, a manganese content of 50-99.9% by weight, an iron content of 0.1-15% by weight, a zirconium content of 0-15% by weight and cerium content of 0-15% by weight.  
     
     
         8 . A process for producing pyromellitic acid according to  claim 7 , wherein iron content is 1-200 ppm, zirconium content is 0-500 ppm and cerium content is 0-500 ppm in solvent.  
     
     
         9 . A process for producing pyromellitic acid according to claim 6, wherein 2,4,5-trimethylbenzaldehyde and/or its oxidized derivative is oxidized semi-continuously at 180-240° C. using an acetic acid solvent containing 10-90% by weight of water.