Process for recovering and recycling an acid catalyst

A process for the preparation of glycolic acid, comprising

• (A) contacting carbon monoxide with an aqueous formaldehyde reactant in the presence of an acid catalyst comprising methanesulfonic acid, methanedisulfonic acid, methanetrisulfonic acid, bis(methylsulfonyl)methanesulfonic acid, or a combination thereof to produce an aqueous glycolic acid mixture comprising about 70 to about 90 weight percent glycolic acid, based on the total weight of the aqueous glycolic acid mixture, and about 1 to about 10 weight percent of the acid catalyst;
• (B) extracting the aqueous glycolic acid mixture with an extraction solvent, comprising
• (i) about 5 to about 45 weight percent, based on the total weight of the extraction solvent, of a tertiary amine comprising tris(2-ethylhexyl)amine, tris(2-ethylbutyl)amine, trioctylamine, triisooctylamine, triisodecyl amine, tridodecylamine, tridecylamine, dioctyldecylamine, didecyloctylamine, or a combination thereof;
• (ii) about 5 to about 45 weight percent, based on the total weight of the extraction solvent, of a modifier comprising 2-ethylhexanoic acid, lauric acid, bis(2-ethylhexyl)hydrogen phosphate, perfluorooctanoic acid, or a combination thereof, wherein the weight ratio of the modifier to the tertiary amine is about 1:1 to about 5:1;
• and
• (iii) about 10 to about 90 weight percent of a diluent, based on the total weight of the extraction solvent, comprising hexane, heptane, decane, methylcyclohexane, benzene, toluene, xylene, isoparaffinic mixed hydrocarbons having a boiling range between 90 and 325° C., 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;
• (C) separating the aqueous raffinate and organic extract phases;
• and
• (D) extracting the organic extract phase from step (C) with an aqueous formaldehyde solution, comprising about 35 to about 85 weight percent formaldehyde, based on the total weight of the 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 (C) and an organic raffinate phase comprising a minor amount of the acid catalyst contained in the organic extract phase.