Patent ID: 7863481

Claim:
In a process for producing a terephthalic acid via at least one liquid phase oxidation step of paraxylene, that employs a recycled liquid, wherein said recycled liquid comprises at least a portion of a recovered mother liquor that has been recovered downstream of said liquid phase oxidation step, the improvement comprising: (a) introducing at least a portion of said recovered mother liquor into a purge treatment zone as a purge feed stream, wherein said purge feed stream comprises oxidation byproducts from said liquid phase oxidation step and one or more catalyst components, wherein said oxidation byproducts include benzoic acid (BA) and non-BA byproducts; wherein said non-BA byproducts comprise IPA, PA, trimellitic acid, 2,5,4â€²-tricarboxybiphenyl, 2,5,4â€²-tricarboxybenzophenone, 4-carboxybenzaldehyde (4-CBA), naphthalene dicarboxylic acid, monocarboxyfluorenones, and/or dicarboxyfluorenones; (b) separating at least a portion of said purge feed stream into (i) a BA rich stream and (ii) a catalyst and non-BA byproduct rich stream, wherein the concentration of BA in said BA rich stream is at least about 1.5 times the concentration of BA in said purge feed stream on a weight basis; and (c) separating at least a portion of said (ii) catalyst and non-BA byproduct rich stream into a catalyst rich stream and a non-BA byproduct rich stream, wherein the cumulative concentration of all of said catalyst components in said catalyst rich stream is at least about 1.5 times the cumulative concentration of all of said catalyst components in said purge feed stream on a weight basis, wherein the concentration of said non-BA byproducts in said non-BA byproduct rich stream is at least about 1.5 times the concentration of said non-BA byproducts in said purge feed stream on a weight basis; wherein a portion of said non-BA byproduct rich stream is subsequently combined with a TPA product stream to form a combined stream.