Process for producing taurine from alkali taurinates

Abstract

A process for producing taurine from alkali ditaurinate or alkali tritaurinate, or their mixture, comprising the conversion of alkali ditaurinate to dialkali ditaurinate or alkali tritaurinate to trialkali tritaurinate, or their mixture, the ammonolysis reaction of ammonia added to a solution of dialkali ditaurinate or trialkali tritaurinate, or their mixture, to yield alkali taurinate, removing excess ammonia from the foregoing and neutralizing alkali taurinates with an acid to form a crystalline suspension of taurine, and recovering taurine by means of solid-liquid separation.

What is claimed is: 
     
       1. A process for the production of taurine from alkali ditaurinate or alkali tritaurinate, or their mixture, comprising,
 (a) adding an alkali hydroxide to a solution of alkali ditaurinate, or alkali tritaurinate or their mixture, to prepare a solution of dialkali ditaurinate, or trialkali tritauriante or their mixture,   (b) adding an excess amount of ammonia to a solution of dialkali ditaurinate, or dialkali tritaurinate, or their mixture, and subjecting the solution to ammonolysis reaction to yield a mixture of alkali taurinates,   (c) removing excess ammonia from (b) and neutralizing alkali taurinates with an acid to form a crystalline suspension of taurine, and   (d) recovering taurine by means of solid-liquid separation.   
     
     
       2. The process according to  claim 1 , wherein alkali ditaurinate and alkali tritaurinate are prepared from diethanolamine and triethanolamine, respectively. 
     
     
       3. The process according to  claim 1 , wherein alkali ditaurinate, alkali tritaurinate, and their mixture are the byproducts in the production of taurine by the ammonolysis reaction of alkali isethionate or alkali vinyl sulfonate. 
     
     
       4. The process according to  claim 1 , wherein the catalysts for the ammonolysis reaction are sodium hydroxide, potassium hydroxide, lithium hydroxide, sodium carbonate, potassium carbonate, lithium carbonate, sodium sulfate, sodium sulfite, potassium sulfate, and potassium sulfite. 
     
     
       5. The process according to  claim 1 , wherein alkali metals are lithium, sodium, and potassium. 
     
     
       6. The process according to  claim 1 , wherein the acids are sulfuric acid, hydrochloric acid, nitric acid, hydrobromic acid, sulfurous acid, sulfur dioxide, and carbon dioxide. 
     
     
       7. The process according to  claim 1 , wherein the ammonolysis reaction is carried out at a temperature from 150 to 280° C. and under a pressure from autogenous to 260 bar. 
     
     
       8. A cyclic process for the production of taurine from alkali ditaurinate, alkali tritaurinate, and alkali isethionate in an overall molar yield of at least 85% as calculated from the molar mass of alkali isethionate, comprising:
 (a) adding excess ammonia to a solution comprised of alkali isethionate and subjecting the solution to ammonolysis,   (b) removing excess ammonia from the solution of step (a), neutralizing the solution with an acid to form taurine, and separating the taurine to yield a mother liquor solution comprised of alkali ditaurinate and alkali tritaurinate,   (c) adding an alkali hydroxide to the mother liquor solution of step (b) comprised of alkali ditaurinate and alkali tritaurinate to prepare a solution comprised of dialkali ditaurinate and trialkali tritaurinate, wherein the molar amount of the alkali hydroxide is at least equal to the molar amount of total taurinates in the mother liquor solution of step (b);   (d) adding excess ammonia to the solution comprised of the dialkali ditaurinate and trialkali tritaurinate, and subjecting the solution to ammonolysis,   (e) removing excess ammonia from the solution of step (d) and neutralizing the solution with an acid to form a crystalline suspension of taurine, and   (f) recovering taurine by means of solid-liquid separation to obtain a mother liquor solution comprised of alkali ditaurinate and alkali tritaurinate.   
     
     
       9. The cyclic process according to claim 8, wherein the alkali metals are lithium, sodium, or potassium. 
     
     
       10. The cyclic process according to claim 8, wherein the acid is selected from the group consisting of sulfuric acid, hydrochloric acid, nitric acid, hydrobromic acid, sulfurous acid, sulfur dioxide, and carbon dioxide. 
     
     
       11. The cyclic process according to claim 8, wherein the ammonolysis reaction is carried out at a temperature from 150 to 280° C. and under a pressure from autogenous to 260 bar. 
     
     
       12. The cyclic process according to claim 8, wherein the mother liquor solution comprised of alkali ditaurinate and alkali tritaurinate in step (c) further comprises added alkali isethionate. 
     
     
       13. The cyclic process according to claim 8, further comprising adding an alkali hydroxide to the mother liquor solution of step (f) comprised of alkali ditaurinate and dialkali tritaurinate to prepare a solution comprised of alkali tritaurinate and trialkali tritaurinate, wherein the molar amount of the alkali hydroxide is at least equal to the molar amount of total taurinates comprised of the alkali ditaurinate and alkali tritaurinate, and recycling the solution to the ammonolysis in step (a).