US 8,785,686 B2  4  3  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;  (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;  with an extraction solvent, comprising  (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  (B) separating the aqueous raffinate and organic extract  phases; and  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;  (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;  (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  (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 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;  (i) about 50 to about 95 weight percent glycolic acid, based  on the total weight of the aqueous glycolic acid mixture,  and  (A) extracting an aqueous glycolic acid mixture, comprising  with an extraction solvent, comprising  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:  (F) combining the organic wash extract phase with the extrac› tion solvent of step (A) or with the organic extract phase of  step (B).  (E) separating the washed aqueous raffinate and organic wash  extract phases; and  (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;  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;  DETAILED DESCRIPTION 