Cyclic process for producing alkali taurinate

Abstract

There is disclosed a cyclic process for producing alkali taurinate from a solution comprising alkali ditaurinate and alkali tritaurinate by the ammonolysis in the presence of one or more catalysts. The ammonolysis reaction is catalyzed by alkali salts of hydroxide, sulfate, sulfite, phosphate, or carbonate. Taurine or alkali taurinate is prepared in a yield from 90% to quantitative by successive ammonolysis.

What is claimed is: 
     
         1 . A cyclic process for producing alkali taurinate, comprising:
 (a) adding an excess of ammonia and at least one catalyst to a solution comprising alkali ditaurinate and alkali tritaurinate;   (b) subjecting the solution of step (a) to an ammonolysis reaction; and   (c) removing excess ammonia to obtain a solution comprising alkali taurinate.   
     
     
         2 . The cyclic process according to  claim 1 , further comprising the steps of:
 (d) neutralizing the strongly basic solution comprising alkali taurinate with an acid to form a neutralized solution containing a crystalline suspension of taurine, wherein the neutralized solution has a pH of 5-9;   (e) separating the taurine from the neutralized solution;   (f) returning the neutralized solution of step (e) to step (a) for further ammonolysis.   
     
     
         3 . The process according to  claim 1 , wherein the solution comprising alkali ditaurinate and alkali tritaurinate is prepared from diethanolamine and triethanolamine. 
     
     
         4 . The process according to  claim 1 , wherein the solution comprising alkali ditaurinate and alkali tritaurinate is the neutralized solution after separating taurine in the production of taurine by a prior ammonolysis reaction of alkali isethionate. 
     
     
         5 . The process according to  claim 1 , wherein the solution comprising alkali ditaurinate and alkali tritaurinate is the neutralized solution after separating taurine in the production of taurine by a prior ammonolysis reaction of the solution comprising alkali ditaurinate and alkali tritaurinate. 
     
     
         6 . The process according to  claim 1 , wherein the at least one catalyst is selected from the group of alkali salts of hydroxide, carbonate, sulfate, sulfite, phosphate, nitrate, and carboxylate. 
     
     
         7 . The process according to  claim 1 , wherein the at least one catalyst is alkali salt of hydroxide. 
     
     
         8 . The process according to  claim 1 , wherein the at least one catalyst is sodium hydroxide. 
     
     
         9 . The process according to  claim 1 , wherein alkali ditaurinate and alkali tritaurinate in the neutralized solution are converted to dialkali ditaurinate and trialkali tritaurinate, respectively, by adding sufficient amount of alkali hydroxide. 
     
     
         10 . The process according to  claim 2 , wherein the acid is selected from hydrochloric acid, hydrobromic acid, sulfuric acid, nitric acid, phosphoric acid, and organic carboxylic acids. 
     
     
         11 . The process according to  claim 2 , wherein the acid is sulfuric acid. 
     
     
         12 . The process according to  claim 1 , wherein the overall yield of taurine or alkali taurinate from alkali ditaurinate and alkali tritaurinate is from 90% to quantitative from successive ammonolysis. 
     
     
         13 . The process according to  claim 1 , wherein the alkali is lithium, sodium, or potassium.