| 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° to 230° C. and a pressure of about 1,850 to 3,600 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 bromide compound, and samarium, with the samarium being employed at a concentration of about 0.005 to 500 ppm. |