Process for producing taurine

Abstract

There is disclosed a process for producing taurine by the ammonolysis of alkali isethionate in the presence of alkali ditaurinate or alkali tritaurinate, or their mixture, to inhibit the formation of byproducts and to continuously convert the byproducts of the ammonolysis reaction to alkali taurinate. The production yield is increased to from 90% to nearly quantitative. The ammonolysis reaction is catalyzed by alkali salts of hydroxide, sulfate, sulfite, phosphate, or carbonate.

What is claimed is: 
     
       1. A process for producing taurine from alkali isethionate, comprising:
 (a) mixing alkali isethionate with a solution of alkali ditaurinate, alkali tritaurinate, or their mixture in the presence of one or more catalysts;   (b) adding an excess of ammonia to the (a) and subjecting the solution to ammonolysis reaction to yield a mixture of alkali taurinate, alkali ditaurinate, and alkali tritaurinate;   (c) removing excess ammonia and neutralizing with an acid to obtain a crystalline suspension of taurine; and   (d) separating taurine by means of solid-liquid separation.   
     
     
       2. The process according to  claim 1 , wherein alkali taurinate and alkali tritaurinate are produced from diethanolamine and triethanolamine, respectively. 
     
     
       3. The process according to  claim 1 , wherein a mixture of alkali ditaurinate and alkali tritaurinate is the byproduct of the ammonolysis reaction of alkali isethionate. 
     
     
       4. The process according to  claim 1 , wherein an acid is selected from hydrochloric acid, hydrobromic acid, sulfuric acid, nitric acid, and organic carboxylic acids. 
     
     
       5. The process according to  claim 1 , wherein the mother liquor after separating taurine and alkali salt is continuously recycled and mixed with a new batch of alkali isethionate for the ammonolysis reaction. 
     
     
       6. The process according to  claim 1 , one or a combination of two or more catalysts for the ammonolysis reaction is selected from alkali salts of hydroxide, carbonate, sulfate, sulfite, phosphate, and nitrate. 
     
     
       7. The process according to  claim 1 , wherein the production yield of taurine is greater than 95%, to nearly quantitative. 
     
     
       8. The process according to  claim 1 , wherein the alkali metals are lithium, sodium, or potassium. 
     
     
       9. The process according to  claim 1 , wherein the production yield of taurine is greater than 85%. 
     
     
       10. The process according to  claim 1 , wherein the production yield of taurine is greater than 90%. 
     
     
       11. A process for producing taurine from alkali isethionate in an overall molar yield of at least 85% on the basis of alkali isethionate, comprising:
 (a) mixing alkali isethionate with a solution comprised of alkali ditaurinate, or with a solution comprised of alkali tritaurinate, or with a solution comprised of alkali ditaurinate and alkali tritaurinate, in the presence of at least one catalyst, and adding an alkali hydroxide to the solution wherein the molar amount of the alkali hydroxide is at least equal to the molar amount of total taurinates in the solution;   (b) adding excess ammonia to the solution of step (a) and subjecting the solution to ammonolysis to yield a mixture of alkali taurinate, alkali ditaurinate and alkali tritaurinate;   (c) removing excess ammonia and neutralizing the mixture of step (b) with an acid to obtain a crystalline suspension of taurine;   (d) recovering taurine by means of solid-liquid separation to obtain a mother liquor solution comprised of alkali ditaurinate and alkali tritaurinate; and   (e) returning the mother liquor solution of step (d) to step (a) and performing steps (a), (b), (c), and (d).   
     
     
       12. The process according to claim 11, wherein for step (a) the solution comprised of the alkali ditaurinate and the solution comprised of the alkali tritaurinate are produced from diethanolamine and triethanolamine, respectively. 
     
     
       13. The process according to claim 11, wherein the solution comprised of the alkali ditaurinate and alkali tritaurinate for step (a) is produced from alkali isethionate by a process comprising the steps of:
 (1) adding excess ammonia and optionally a catalyst to a solution comprised of alkali isethionate and subjecting the solution to ammonolysis;   (2) removing excess ammonia from the solution of step (1) and neutralizing the solution with an acid to form a crystalline taurine suspension; and   (3) recovering taurine to obtain a solution comprised of alkali ditaurinate and alkali tritaurinate.   
     
     
       14. The process according to claim 11, wherein the acid is selected from the group consisting of hydrochloric acid, hydrobromic acid, sulfuric acid, nitric acid, and organic carboxylic acids. 
     
     
       15. The process according to claim 11, wherein the catalyst is selected from the group consisting of alkali salts of hydroxide, carbonate, sulfate, sulfite, phosphate, and nitrate. 
     
     
       16. The process according to claim 11, wherein the alkali is lithium, sodium, or potassium. 
     
     
       17. The process according to claim 11, wherein the overall molar production yield of taurine from the alkali isethionate is greater than 85%. 
     
     
       18. The process according to claim 11, wherein the overall molar production yield of taurine from the alkali isethionate is greater than 90%. 
     
     
       19. The process according to claim 11, wherein the overall molar production yield of taurine from the alkali isethionate is greater than 95%, to nearly quantitative.