US Patent No. 9,932,287

PROCESS FOR OXIDATION OF ALKYL AROMATIC COMPOUND TO AROMATIC CARBOXYLIC ACID


Patent No. 9,932,287
Issue Date April 03, 2018
Title Process For Oxidation Of Alkyl Aromatic Compound To Aromatic Carboxylic Acid
Inventorship Vivek Shankaranarayanan, Hyderabad (IN)
Suresh Shantilal Jain, Thane (IN)
Pavankumar Aduri, Thane (IN)
Rajesh Ratnakar Terdalkar, Thane (IN)
Nitin Haribhau Patil, Old Panvel (IN)
Parasuveera Uppara, Mumbai (IN)
Assignee Reliance Industries Limited, Mumbai (IN)

Claim of US Patent No. 9,932,287

1. A process for the oxidation of p-xylene to terephthalic acid comprising the following steps:a) oxidizing p-xylene using at least one oxidizing agent in the presence of at least one metal salt as a catalyst and at least one promoter in at least one aliphatic carboxylic acid as a fluid medium to obtain a reaction mixture comprising terephthalic acid, oxidation intermediates of terephthalic acid, trimellitic acid, at least one metal salt, the promoter, the aliphatic carboxylic acid and water; wherein the oxidation intermediates of terephthalic acid comprise at least one compound selected from the group consisting of p-tolualdehyde, p-toluic acid and 4-carboxy benzaldehyde;
b) separating a partial amount of the terephthalic acid from the reaction mixture by crystallization and filtration to obtain crude terephthalic acid and a mother liquor; wherein the mother liquor comprises trimellitic acid, the promoter, at least one metal salt, water and the aliphatic carboxylic acid;
c) dividing the mother liquor into a recycle stream and a purge stream; wherein the ratio of the amount of the recycle stream and the purge stream is in the range from 19:1 to 4:1; and recycling the recycle stream to step (a);
d) extracting p-xylene soluble chemicals from the purge stream by adding p-xylene to the purge stream and mixing at a predetermined temperature to obtain a biphasic mixture, which after separation, provides an organic stream and an aqueous stream; wherein the organic stream comprises p-xylene, the aliphatic carboxylic acid and the oxidation intermediates of terephthalic acid, and the aqueous stream comprises the aliphatic carboxylic acid, trimellitic acid, the promoter and at least one metal salt;
e) recycling the organic stream comprising p-xylene, the aliphatic carboxylic acid and the oxidation intermediates of terephthalic acid to step (a); and
f) recovering at least one metal salt from the aqueous stream and recycling the recovered metal salt to step (a);
wherein, the concentration of trimellitic acid in the reaction mixture is below 2000 ppm.