Process for producing glycolic acid

Abstract

Glycolic acid having a high purity is obtained by subjecting glycolic acid or a glycolic acid solution containing contaminants to double-chamber electrodialysis combined with one or more treatments selected from among treatment with an activated carbon, treatment with an ion exchange resin, concentration treatment and cooling crystallization.

1 . A glycolic acid obtained by a production process comprising carrying out 3 to 5 kinds of steps selected from the group consisting of the following steps (a1), (a2), (b), (c) and (d) (but, the step (a2) must be employed) for a solution containing a glycolate one or two or more times in any order,
 (a1) step for electrodialyzing with an anion exchange membrane and a cation exchange membrane;   (a2) step for water-splitting electrodialysis;   (b) step for cooling crystallization;   (c) step for treatment with an activated carbon; and   (d) step for treatment with an ion exchange resin.   
     
     
         2 . The glycolic acid according to  claim 1 , wherein the kinds and order of the following steps are any one of (a1) (a2) (b), (c) (a2) (b), (c) (a2) (d) (c) or (c) (a2) (c) (d) for the solution containing the glycolate,
 (a1) step for electrodialyzing with anion exchange membrane and cation exchange membrane;   (a2) step for water-splitting electrodialysis;   (b) step for cooling crystallization;   (c) step for treatment with an activated carbon; and   (d) step for treatment with an ion exchange resin.   
     
     
         3 . The glycolic acid according to  claim 1 , wherein 3 to 5 kinds of steps selected from the group consisting of following steps (a1), (a2), (b), (c) and (d) (but, the step (a2) must be employed) are carried out one or two or more times in any order, and the step (b) is subsequently carried out one or two or more times for a solution containing a glycolate,
 (a1) step for electrodialyzing with an anion exchange membrane and a cation exchange membrane;   (a2) step for water-splitting electrodialysis;   (b) step for cooling crystallization;   (c) step for treatment with an activated carbon; and   (d) step for treatment with an ion exchange resin.   
     
     
         4 . The glycolic acid according to  claim 3 , wherein the kinds and order of the following steps are any one of (a1) (c) (a2) (b), (a1) (a2) (d) (b), (a1) (c) (a2) (d) (b) or (c) (a2) (d) (b) for the solution containing the glycolate,
 (a1) step for electrodialyzing with the anion exchange membrane and the cation exchange membrane;   (a2) step for water-splitting electrodialysis;   (b) step for cooling crystallization;   (c) step for treatment with an activated carbon; and   (d) step for treatment with an ion exchange resin.   
     
     
         5 . The glycolic acid according to  claim 1 , wherein
 the step (a1) is a step for obtaining the glycolate solution by supplying the glycolate solution to a desalination chamber of an electrodialysis device having desalination chambers and concentrating chambers formed by alternately arranging anion exchange membranes and cation exchange membranes between electrodes for conducting electrodialysis, and transmitting a glycolic acid anion and a monovalent cation from said ion exchange membrane; and   the step (a2) is a step for obtaining the glycolic acid solution by supplying the glycolate solution after the step (a1) treatment or after the step (c) treatment as it is or via an optional step to the acid chamber of a water-splitting electrodialysis device having acid chambers and base chambers formed by alternately arranging a bipolar membranes and a cation exchange membranes, and acidifying the glycolic acid anion by electrolysis of water through the bipolar membrane.   
     
     
         6 . The glycolic acid according to  claim 1 , wherein a step (e) for concentration is carried out just before the step (b). 
     
     
         7 . The glycolic acid according to  claim 1 , wherein the process contains a step for obtaining the solution containing the glycolate by oxidizing an ethylene glycol. 
     
     
         8 . The glycolic acid according  claim 1 , wherein the solution containing the glycolate is obtained by bringing a microorganism having the ability to produce glycolic acid by oxidizing ethylene glycol into contact with the ethylene glycol in the presence of oxygen. 
     
     
         9 . The glycolic acid according to  claim 8 , wherein the microorganism belongs to the genus  Escherichia.    
     
     
         10 . The glycolic acid according to  claim 1 , wherein the molar ratio of the ethylene glycol to a purified glycolic acid is less than 0.1%. 
     
     
         11 . The glycolic acid according to  claim 1 , wherein the concentration of the ethylene glycol in the solution containing the glycolate is less than 5% as a molar ratio based on the glycolate. 
     
     
         12 . The glycolic acid according to  claim 1 , wherein the glycolic acid has the total concentration of the counter cation to the glycolic acid other than hydrogen ion of from 0 to 5 ppm is obtained. 
     
     
         13 . The glycolic acid according to  claim 1 , wherein the step (a1) is a step for electrodialyzing with a double-chambered electrodialysis device comprised an anion exchange membrane and a cation exchange membrane, and the step (a2) is a step for water-splitting electrodialysis with a double-chambered water-splitting electrodialysis device. 
     
     
         14 . A polyglycolic acid made from the glycolic acid according to  claim 1 . 
     
     
         15 . A polyglycolic acid obtained by ring-opening polymerization or polycondensation via cyclic ester using the glycolic acid according to  claim 1  as a raw material. 
     
     
         16 . A glycolic acid copolymer obtained by polycondensation of the glycolic acid according to  claim 1  with a compound having one each of a hydroxyl group and a carboxylic acid group or any two of hydroxyl groups or carboxylic acid groups as a functional group in a molecule as raw materials. 
     
     
         17 . An aqueous glycolic acid solution obtained by acidifying ammonium glycolate using an aqueous solution of an ammonium glycolate as a starting material, wherein the concentration of an ammonium ion in the aqueous solution is not more than 5 ppm based on the glycolic acid. 
     
     
         18 . The aqueous glycolic acid solution according to  claim 17 , wherein the aqueous solution of the ammonium glycolate is obtained by the microorganism having the ability to produce the glycolic acid by oxidizing the ethylene glycol. 
     
     
         19 . The aqueous glycolic acid solution according to  claim 18 , wherein said microorganism belongs to the genus  Escherichia.    
     
     
         20 . The aqueous glycolic acid solution according to  claim 17 , wherein the acidification of the ammonium glycolate is conducted by a water-splitting electrodialysis treatment of the aqueous solution of the ammonium glycolate. 
     
     
         21 . A glycolic acid obtained from an aqueous glycolic acid solution obtained by acidifying an ammonium glycolate using an aqueous solution of an ammonium glycolate as a starting material, wherein the concentration of ammonium ion in the glycolic acid is not more than 5 ppm based on the glycolic acid. 
     
     
         22 . The glycolic acid according to  claim 21 , wherein the aqueous solution of ammonium glycolate is obtained by the microorganism having the ability to produce glycolic acid by oxidizing ethylene glycol. 
     
     
         23 . The glycolic acid according to  claim 22 , wherein said microorganism belongs to the genus  Escherichia.    
     
     
         24 . The glycolic acid according to  claim 21 , wherein the acidification of the ammonium glycolate is conducted by a water-splitting electrodialysis treatment of the aqueous solution of the ammonium glycolate.