Patent ID: 7501537

Claim:
A process for making a terephthalic acid composition, said process comprising: (a) introducing a solvent feed into a primary oxidation zone, wherein at least 20 weight percent of said solvent feed is recycled solvent; (b) subjecting an oxidizable compound to oxidation in said primary oxidation zone to thereby produce an initial slurry comprising an initial solid comprising terephthalic acid and an initial liquid, wherein a representative sample of said slurry has at least three of the following characteristics based on the combined solid and liquid slurry components: (i) contains a quantity of isophthalic acid (IPA) in an amount up to 9,000 ppmw, (ii) contains a quantity of 4,4′-dicarboxybiphenyl (4,4′-DCB), in an amount op to 64 ppmw, (iv) contains a quantity of 2,6-dicarboxyfluorenone (2,6-DCF), in an amount up to 70 ppmw. (v) contains a quantity of 2,7-dicarboxyfluorenone (2,7-DCF) in an amount up to 12 ppmw, (vi) contains a quantity of 9-fluorenone-2-carboxylic acid (9F-2CA) in an amount up to 12 ppmw, (vii) contains a quantity of 4,4′-dicarboxystilbene (4,4′-DCS) in an amount up to, (viii) contains a quantity of 4,4′-dicarboxyanthraquinone (4,4′-DCA) in an amount up to 6 ppmw; and (c) subjecting at least a portion of said initial slurry to oxidative digestion in at least one digestion zone, wherein less than 70 weight percent of said initial liquid is removed from said initial slurry prior to introducing said initial slurry into said digestion zones wherein the weight ratio of the amount of benzoic acid and/or cobalt present in a digestion feed slurry entering said digestion zone to the amount of the same component or components present in said initial slurry produced from said primary oxidation zone is at least 0.3.