| abstract |
1,152,575. Purifying aromatic polycarboxylic acids. STANDARD OIL CO. 16 May, 1966 [17 May, 1965], No. 21654/66. Heading C2C. Aromatic polycarboxylic acids, particularly those containing aldehyde impurities which are produced by catalytic liquid phase oxidation of polyalkylaromatic hydrocarbons, are purified by contacting an aqueous solution of such acid at elevated temperature and pressure and in presence of H 2 -containing gas with a Pt-group metal-containing catalyst under mild hydrogenation conditions, the purified acid being recovered from the solution by crystallization employing controlled-rate evaporative cooling. Details are given for the purification of terephthalic acid, but the process is said to be also applicable to isophthalic, trimesic, trimellitic, mellitic and naphthalenedicarboxylic acids. |