GB1275865A - Process for purifying isophthalic acid - Google Patents

Abstract

1275865 Purification of isophthalic acid ATLANTIC RICHFIELD CO 5 May 1970 [23 May 1969] 21599/70 Heading C2C Isophthalic acid is recovered from a crude solid oxidation product, obtained by the oxidation of m-xylene with an O 2 -containing gas followed by cooling and separation of the crude solid oxidation product, by (1) feeding to a first crystallization zone a solution of the said crude solid oxidation product in a mixture of water and acetic acid, the mixture containing 75 to 99% by wt. acetic acid; (2) maintaining the first crystallization zone at a temperature of 250-375‹ F. and at a pressure of about 15 to 110 p.s.i.a.. while withdrawing vaporized acetic acid from the zone, thus producing a slurry of isophthalic acid crystals; (3) passing the said slurry to a second crystallization zone; (4) maintaining the second crystallization zone at a temperature of 220-265‹ F. and at a pressure of 15 to 28 p.s.i.a., while withdrawing vaporized acetic acid from the zone; (5) withdrawing a slurry of isophthalic acid crystals from the second crystallization zone; and either (6) recovering isophthalic acid from the slurry withdrawn in step (5); or (7) passing at least part of the slurry withdrawn in step (5) to a third crystallization zone; (8) maintaining the third crystallization zone at a temperature of 105- 170‹ F. and at a pressure below atmospheric pressure; and (9) passing the resulting slurry to a solid-liquid separation zone wherein isophthalic acid crystals are separated from the slurry. An example is given which illustrates the process.