step can be effectively used to recover the tertiary amine and/or onium carboxylate compound and modifier from the glycolic acid raffinate to control their potential loss. Accord› ingly, in another embodiment of the invention, our recovery process may further comprise: 

extracting the aqueous raffinate phase from step (B) with a wash solvent comprising about 80 to about 100 weight per› cent, based on the total weight of the wash solvent, of a wash diluent comprising carbon dioxide, an aliphatic hydrocarbon containing from 3 to 25 carbon atoms, an aromatic hydrocar- bon containing 6 to 25 carbon atoms, a halogenated hydro› carbon containing 6 to 25 carbon atoms, or a combination thereof; and about O to about 20 weight percent of a wash modifier comprising an aliphatic carboxylic acid containing from 5 to 16 carbon atoms, an organophosphorus acid con- taining from 5 to 16 carbon atoms, an alkanol containing 6 to 12 carbon atoms, or a combination thereof, to form a washed aqueous raffinate phase and an organic wash extract phase, wherein the weight ratio of the wash solvent to the aqueous raffinate phase is about 0.1:1 to about 1:1; 

separating the washed aqueous raffinate and organic wash extract phases, and 

combining the organic wash extract phase with the extrac› tion solvent of step (A) or with the organic extract phase of step (B). 

The acid catalysts that are extracted into the organic extract phase can be back extracted into aqueous formaldehyde and recycled into the hydrocarboxylation reaction. Hence, another embodiment of our invention is a process for recov› ering an acid catalyst from aqueous glycolic acid, comprising 

(A) extracting an aqueous glycolic acid mixture, comprising 

(i) about 70 to about 90 weight percent glycolic acid, based on the total weight of the aqueous glycolic acid mixture, and 

(ii) about 1 to about 10 weight percent of an acid catalyst comprising sulfuric acid, methanesulfonic acid, meth› anedisulfonic acid, methanetrisulfonic acid, bis(methyl› sulfonyl)methanesulfonic acid, trifluoromethane› sulfonic acid, 1, 1,2,2-tetrafluoroethanesulfonic acid 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, a tertiary amine com› prising tris(2-ethylhexyl)amine, tris(2-ethylbutyl) amine, trioctylamine, triisooctylamine, triisodecyl amine, tridodecylamine, tridecylamine, dioctyldecy› lamine, didecyloctylamine, or a combination thereof; 

(ii) about 5 to about 45 weight percent of a modifier com› prising 2-ethylhexanoic acid, !auric acid, perfluorooc› tanoic acid, bis(2-ethylhexyl)hydrogen phosphate, or a combination thereof, wherein the weight ratio of the modifier to the tertiary amine is about 1: 1 to about 5: 1; 

(iii) about 10 to about 90 weight percent of a diluent com› prising hexane, heptane, decane, methylcyclohexane, benzene, toluene, xylene, 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 con› tained in the aqueous glycolic acid mixture; 

(B) separating the aqueous raffinate and organic extract phases; 

(C) extracting the organic extract phase from step (B) 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 (B) and an organic raffinate phase comprising a minor amount of the acid catalyst contained in the organic extract phase; 

(D) contacting the aqueous raffinate phase from step (B) with a wash solvent comprising about 80 to about 100 weight percent, based on the total weight of the wash solvent, of a wash diluent comprising hexane, heptane, decane, meth- ylcyclohexane, benzene, toluene, xylene, or a combination thereof; and about O to about 20 weight percent of a wash modifier comprising 2-ethylhexanoic acid, !auric acid, bis (2-ethylhexyl)hydrogen phosphate, 2-ethylhexanol, 2-eth› ylbutanol, n-hexanol, n-octanol, n-decanol, or a combina› tion thereof, to form a washed aqueous raffinate phase and an organic wash extract phase, wherein the weight ratio of the wash solvent to the aqueous raffinate phase is about 0.1:1 to about 1:1; 

(E) separating the washed aqueous raffinate and organic wash extract phases; and 

(F) combining the organic wash extract phase with the extrac› tion solvent of step (A) or with the organic extract phase of step (B). 

The present invention provides a means to recover and, optionally, recycle homogeneous, strong acid catalysts from aqueous glycolic acid mixtures that are prepared by the hydrocarboxylation of aqueous formaldehyde solutions. In a general embodiment, therefore, our invention provides a pro› cess 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 sul› fonic 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 con› taining from 5 to 16 carbon atoms, a fluoroalkyl car› boxylic acid containing 5 to 16 carbon atoms, an orga› nophosphorus 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 hydro› carbon containing from 3 to 25 carbon atoms, an aro› matic 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 com› prising a major amount of the acid catalyst contained in the aqueous glycolic acid mixture; 

(B) separating the aqueous raffinate and organic extract phases; and 

## DETAILED DESCRIPTION 

