Process for the recovery of organic acids from aqueous solutions

Abstract

A process for recovering a desired organic acid from a solution includes the steps of: providing an aqueous solution including at least one desired organic acid or its acid anion; adjusting the proton concentration in the aqueous solution to a desired level, with the desired proton concentration being selected, at least in part, by the amount of available protons needed to associate with the acid anions of the desired organic acid(s) to be recovered and/or acid anions that are weaker than the desired organic acids; and recovering at least a portion of the at least one desired organic acid from the aqueous phase. The desired proton concentration can be based on the amount of available protons being greater than, less than or substantially equal, to the amount of protons needed to associate with the anion of the desired organic acid(s) and acid anions that are weaker than the desired organic acid(s). Specific examples of suitable organic acids include, but are not limited to, ascorbic, succinic, tartaric, glyconic, gulonic, citric, lactic, malic, maleic, acetic, formic, gluconic pyruvic, propionic, butyric, itaconic acids and mixtures thereof. One embodiment of the present invention relates to the recovery of 2-keto-L-gulonic acid (KLG) from aqueous solutions such as fermentation baths.

What is claimed is:  
     
         1 . A process for recovering a desired organic acid from a solution comprising the steps of: 
 (a) providing an aqueous solution comprising at least one desired organic acid or its acid anion;    (b) adjusting the proton concentration in the aqueous solution to a desired level, with the desired proton concentration being selected, at least in part, by the amount of available protons needed to associate with the acid anions of the desired organic acid(s) and/or acid anions that are weaker than the desired organic acids; and    (c) recovering at least a portion of the at least one desired organic acid from the aqueous phase.    
     
     
         2 . The process according to  claim 1  wherein the desired proton concentration is based on the amount of available protons being substantially equal to the amount of protons needed to associate with the anion of the desired organic acid(s) and acid anions that are weaker than the desired organic acid(s).  
     
     
         3 . The process according to  claim 1  wherein the desired proton concentration is based on the amount of available protons being greater than the amount of protons needed to associate with the anions of the desired organic acid(s) and acid anions that are weaker than the desired organic acid(s).  
     
     
         4 . The process according to  claim 3  wherein the desired proton concentration is based on an amount of protons that is about 1 to about 10% greater than the amount of protons needed to associate with the desired organic acid(s) and acid anions that are weaker than the desired organic acid(s).  
     
     
         5 . The process according to  claim 1  wherein the desired proton concentration is based on the amount of available protons being less than the amount of protons needed to associate with the anions of the desired organic acid(s) and acid anions that are weaker than the desired organic acid(s).  
     
     
         6 . The process according to  claim 5  wherein the desired proton concentration is based on an amount of protons that is about 1 to about 10% less than the amount of protons needed to associate with the desired organic acid(s) and acid anions that are weaker than the desired organic acid(s).  
     
     
         7 . The process according to  claim 1  wherein the at least one desired organic acid is an acid in which the salt form of the organic acid is more soluble in water than the acid itself.  
     
     
         8 . The process according to  claim 1  wherein the at least one desired organic acid is susceptible to acid catalyzed decomposition.  
     
     
         9 . The process according to  claim 1  wherein the at least one desired organic acid is selected from the group consisting of ascorbic, succinic, tartaric, glyconic, gluconic gulonic, citric, lactic, malic, maleic, acetic, formic, pyruvic, propionic, butyric, itaconic acids and mixtures thereof.  
     
     
         10 . The process according to  claim 1  wherein the at least one desired organic acid is a carboxylic acid.  
     
     
         11 . The process according to  claim 1  wherein the at least one desired organic acid is an alkali or alkaline earth salt form.  
     
     
         12 . The process according to  claim 11  wherein a counter ion is sodium, potassium or calcium.  
     
     
         13 . The process according to  claim 1  wherein the at least one desired organic acid is at least partially present in an ammonium form.  
     
     
         14 . The process according to  claim 1  wherein the at least one desired organic acid is at least partially present in its anionic form.  
     
     
         15 . The process according to  claim 1  wherein the aqueous solution further includes additional acid anions.  
     
     
         16 . The process according to  claim 1  wherein the additional acid anions are selected from among phosphates, sulfates, nitrates, and chlorides.  
     
     
         17 . The process according to  claim 1  wherein the aqueous solution comprises a fermentation broth that includes unreacted sugar.  
     
     
         18 . The process according to  claim 1  wherein the adjusting step (b) comprises (i) introducing at least one acid into the aqueous solution.  
     
     
         19 . The process according to  claim 18  wherein the at least one acid is a strong acid as compared to the organic acid(s) being recovered.  
     
     
         20 . The process according to  claim 18  wherein the acid is selected from among sulfuric, hydrochloric, nitric and phosphoric acids.  
     
     
         21 . The process according to  claim 18  wherein the amount of acid introduced in step (b), (i) is that amount effective to convert at least a portion of any organic acid salt(s) present in the aqueous solution to their acid form.  
     
     
         22 . The process according to  claim 21  further comprising step (b) (ii) removing at least a portion of any precipitated salts produced in step (i).  
     
     
         23 . The process according to  claim 22  further comprising step (b) (iii) contacting the aqueous solution with a cation exchange resin in its hydrogen or acid form.  
     
     
         24 . The process according to  claim 23  wherein the cation exchange resin comprises a sulfonated polystyrene resin.  
     
     
         25 . The process according to  claim 23  wherein the adjusting step further comprises step (b) (iv) introducing at least one base in an amount effective to neutralize at least a portion of any strong acid(s) formed by step (iii).  
     
     
         26 . The process according to  claim 25  wherein the base is selected from among sodium hydroxide and potassium hydroxide.  
     
     
         27 . The process according to  claim 25  wherein the base is the salt form of the organic acid(s) to be recovered.  
     
     
         28 . The method according to  claim 1  further comprising recycling at least a portion of a stream recovered from step (c) to a point before or during step (b).  
     
     
         29 . The process according to  claim 27  wherein the recycle is contacted with an anion exchange resin before introduction into the aqueous solution.  
     
     
         30 . The method according to  claim 28  further comprising recycling at least a portion of a stream recovered from step (c) to a point after step (b) (i).  
     
     
         31 . The method according to  claim 22  further comprising recycling at least a portion of a stream recovered from step (c) to a point after step (b) (ii).  
     
     
         32 . The process according to  claim 1  wherein the adjusting step comprises (i) contacting the aqueous solution with a cation exchange resin in its hydrogen or acid form.  
     
     
         33 . The process according to  claim 31  wherein the cation exchange resin comprises a sulfonated polystyrene resin.  
     
     
         34 . The process according to  claim 31  wherein the adjusting step further comprises (ii) introducing at least one base in an amount effective to neutralize at least a portion of any strong acid(s) formed by step (i).  
     
     
         35 . The process according to  claim 33  wherein the base is selected from among sodium hydroxide and potassium hydroxide.  
     
     
         36 . The process according to  claim 33  wherein the base is the salt form of the organic acid(s) to be recovered.  
     
     
         37 . The process according to  claim 33  further comprising recycling at least a portion of a stream recovered from step (c) to a point after step (b) (i).  
     
     
         38 . The process according to  claim 36  wherein the recycle is contacted with an anion exchange resin before introduction into the aqueous phase.  
     
     
         39 . The process according to  claim 1  wherein step (c) comprises isolating the at least one desired organic acid(s).  
     
     
         40 . The process according to  claim 39  wherein the isolation step comprises both (i) crystallizing the desired organic acid(s) from the aqueous solution, and (ii) at least one of filtration, decantation, centrifugation, extraction, and/or spray drying.  
     
     
         41 . The process according to  claim 40  further comprising recycling at least a portion of a stream recovered from step (c) (ii) for introduction into the aqueous solution.  
     
     
         42 . The process according to  claim 41  wherein the recycle is contacted with an anion exchange resin before introduction into the aqueous solution.  
     
     
         43 . The process according to  claim 1  wherein the organic acid is 2-keto-L-gulonic acid or 2-keto-D-gluconic acid.  
     
     
         44 . The process according to  claim 43  wherein step (a) comprises producing the 2-keto-L-gulonic acid or 2-keto-D-gluconic acid by a fermentation reaction.  
     
     
         45 . The process according to  claim 44  wherein the fermentation reaction is performed in the presence of at least one organism and/or enzyme.  
     
     
         46 . The process according to  claim 43  further comprising (d) converting the 2-keto-L-gulonic acid or 2-keto-D-gluconic acid to ascorbic acid and/or erythorbic acid.  
     
     
         47 . The process according to  claim 1  wherein the process does not include contacting the aqueous solution with an anion exchange resin.  
     
     
         48 . The process according to  claim 1  wherein determination of the desired proton concentration includes titration in an aprotic solvent.  
     
     
         49 . The process according to  claim 48  wherein the aprotic solvent is DMSO.  
     
     
         50 . The process according to  claim 49  further comprising the addition of at least one salt which can precipitate at least a portion of sulfate present in the solution while replacing the sulfates with an acid anion stronger than the at least one desired organic acids.  
     
     
         51 . The process according to  claim 50  wherein the at least one salt is a barium, magnesium or strontium salt.  
     
     
         52 . The process according to  claim 51  wherein the salt is barium chloride, barium perchlorate, barium bromide; magnesium perchlorate, or mixtures thereof.  
     
     
         53 . An organic acid produced by the process of  claim 1 .  
     
     
         54 . A composition comprising an aqueous solution containing 2-keto-L-gulonic acid and a predetermined proton concentration that is substantially equal to the amount of protons needed to associate with the 2-keto-L-gulonic acid and acid anions that are weaker than 2-keto-L-gulonic acid.  
     
     
         55 . A composition comprising an aqueous solution containing 2-keto-L-gulonic acid and a predetermined proton concentration that is greater than the amount of protons needed to associate with the 2-keto-L-gulonic acid and acid anions that are weaker than 2-keto-L-gulonic acid.  
     
     
         56 . The composition according to  claim 55  wherein the predetermined proton concentration is about 1 to about 10% greater than the amount of protons needed to associate with the 2-keto-L-gulonic acid and acid anions that are weaker than 2-keto-L-gulonic acid.  
     
     
         57 . A composition comprising an aqueous phase containing 2-keto-L-gulonic acid and a predetermined proton concentration that is less than the amount of protons needed to associate with the 2-keto-L-gulonic acid and acid anions that are weaker than 2-keto-L-gulonic acid.  
     
     
         58 . The composition according to  claim 57  wherein the predetermined proton concentration is about 1 to about 10% less than the amount of protons needed to associate with the 2-keto-L-gulonic acid and acid anions that are weaker than 2-keto-L-gulonic acid.