Process for the purification of terephthalic acid
AssigneeEastman Kodak Company
InventorsJudy E. Kiefer, William V. Phillips, Thomas E. Woodruff
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Abstract
The present invention provides an improved process for the purification of crude terephthalic acid which has been produced by the oxidation of para-xylene. The process comprises contacting the crude terephthalic acid with oxygen-containing gas at a temperature of about 190.degree. to 230.degree. C. and a pressure of about 1500 to 3600 kPa in the presence of a solvent comprising an alkanoic acid which is preferably acetic acid. The process further comprises the use of a novel and surprisingly effective catalyst system. The catalyst system comprises cobalt, a bromine source, and pyridine.
Claims20
In a process for the purification of crude terephthalic acid, said purification process comprising contacting said crude terephthalic acid with oxygen-containing gas at elevated temperature and pressure in the presence of a solvent containing at least one lower alkanoic acid and a catalyst system comprising cobalt, the improvement comprising employing in said catalyst system a bromine source and pyridine.
In a process for the purification of crude terephthalic acid, said purification process comprising contacting said crude terephthalic acid with oxygen-containing gas at a temperature of about 190.degree. C. to 230.degree. C. and a pressure of about 1500 to 3600 kPa in the presence of a solvent containing acetic acid and a catalyst system comprising about 200 to 500 ppm cobalt, the improvement comprising employing in said catalyst system about 100 to 400 ppm bromine and about 0.1 to 5 moles of pyridine per gram-atom of bromine.
A process for the purification of crude terephthalic acid, said purification process comprising contacting said crude terephthalic acid with a mixture of nitrogen and oxygen comprising about 5 to 20% oxygen at a temperature of about 190.degree. C. to 230.degree. C. and a pressure of about 1500 to 3600 kPa in the presence of (1) a solvent comprising a mixture of water and acetic acid having a water content of about 5% and (ii) a catalyst system comprising about 200 to 500 ppm Co, about 100 to 400 ppm bromine, and about 0.1 to 5 moles of pyridine per gram-atom of bromine.
A process for the purification of crude terephthalic acid, said purification process comprising contacting said crude terephthalic acid with a mixture of nitrogen and oxygen comprising about 5 to 20% oxygen at a temperature of about 190.degree. C. to 230.degree. C. and a pressure of about 1500 to 3600 kPa in the presence of (1) a solvent comprising a mixture of water and acetic acid having a water content of about 5% and (ii) a catalyst system comprising about 200 to 500 ppm Co and 4-bromopyridine in an amount such that about 100 to 400 ppm bromine is present in the reaction system.
Dependencies are inferred from the claim text.