Patent ID: 6034269
Filing Date: 2000-03-07
Classification: C07C

Abstract:
A process for producing a pure carboxylic acid by catalytic liquid phase oxidation of a corresponding precursor in a solvent selected from an aliphatic carboxylic acid or a non-aliphatic organic acid and optionally including water which comprises:(a) forming a feed stream comprising solvent and oxidation catalyst at a pressure in the range of from 2,000 to 10,000 kPa;(b) dissolving gaseous oxygen in the feed stream to achieve an oxygen concentration in the range of from 0.5% to 3.0% w/w and optionally preheating the feed stream to a temperature in the range of from 120.degree. C. to 180.degree. C.;(c) continuously and simultaneously feeding the feed stream and said precursor to a plug flow reaction zone to form a reaction medium in which the solvent:precursor ratio is at least about 30:1 and resulting carboxylic acid is maintained in solution as it is formed;(d) systematically reducing the pressure of the reaction medium from step (c) while cooling it to a temperature in the range of from 120.degree. C. to 180.degree. C. thereby precipitating carboxylic acid crystals to form a slurry;(e) optionally concentrating the slurry; and(f) recovering the carboxylic acid crystals from the slurry.