Patent ID: 8709376

Claim:
A process for recovering an acid catalyst from aqueous glycolic acid, comprising (A) extracting an aqueous glycolic acid mixture, comprising (i) about 50 to about 95 weight percent glycolic acid, based on the total weight of the aqueous glycolic acid mixture, and (ii) about 0.2 to about 12 weight percent, based on the total weight of the aqueous glycolic acid mixture, of an acid catalyst comprising sulfuric acid, an alkyl sulfonic acid containing from 1 to 5 carbon atoms, a fluoroalkyl sulfonic acid containing from 1 to 5 carbon atoms, or a combination thereof; with an extraction solvent, comprising (i) about 5 to about 45 weight percent, based on the total weight of the extraction solvent, of at least one tertiary amine containing from 12 to 40 carbon atoms, at least one onium carboxylate compound, or a combination thereof; (ii) about 5 to about 45 weight percent of at least one modifier comprising an aliphatic carboxylic acid containing from 5 to 16 carbon atoms, a fluoroalkyl carboxylic acid containing 5 to 16 carbon atoms, an organophosphorus acid containing from 5 to 16 carbon atoms, or a combination thereof; and (iii) about 10 to about 90 weight percent of at least one diluent comprising carbon dioxide, an aliphatic hydrocarbon containing from 3 to 25 carbon atoms, an aromatic hydrocarbon containing 6 to 25 carbon atom, a halogenated hydrocarbon containing 6 to 25 carbon atoms, or a combination thereof; to form an aqueous raffinate phase comprising a major amount of the glycolic acid contained in the aqueous glycolic acid mixture and an organic extract phase comprising a major amount of the acid catalyst contained in the aqueous glycolic acid mixture; (B) separating the aqueous raffinate and organic extract phases; and (C) extracting the organic extract phase from step (B) with an aqueous formaldehyde solution to form an aqueous formaldehyde extract comprising a major amount of the acid catalyst contained in the organic extract phase from step (B) and an organic raffinate phase comprising a minor amount of the acid catalyst contained in the organic extract phase.