Cyclic process for producing taurine
There is disclosed a process for producing taurine from ammonium isethionate 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. Alkali taurinate is reacted with ammonium isethionate to obtain taurine and to regenerate alkali isethionate. 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.
1. A cyclic process for producing taurine from ammonium isethionate, comprising:
(a) adding ammonium isethionate to a solution of a mixture of alkali taurinate, alkali ditaurinate, and alkali tritaurinate to react with alkali taurinates;
(b) removing ammonia from (a) to obtain a solution or crystalline suspension of taurine in a solution of alkali isethionate, alkali ditaurinate, and alkali tritaurinate;
(c) adding art acid or an acidic ion exchanger to adjust the pH of the solution or crystalline suspension of step (b) to a range from 5 to 9;
(d) separating taurine by means of solid-liquid separation to provide a mother liquor containing alkali isethionate, alkali ditaurinate, and alkali tritaurinate; and
(e) adding ammonia or ammonium hydroxide to the mother liquor of step (d) and subjecting the solution to an ammonolysis reaction to produce a solution of a mixture of alkali taurinate, alkali ditaurinate, and alkali tritaurinate.
2. The process according to claim 1 , wherein the acid is selected from the group of sulfuric acid, hydrochloric acid, hydrobromic acid, nitric acid, phosphoric acid, organic carboxylic acids, alkyl sulfonic acids, and aryl sulfonic acids.
3. The process according to claim 1 , wherein the acid is isethionic acid.
4. The process according to claim 1 , herein the acid is a mixture of isethionic acid, ditaurine, and tritaurine.
5. The process according to claim 1 , wherein the acid is produced by a process of bipolar membrane electrodialysis of a solution of alkali isethionate or a mixture of alkali isethionate, alkali ditaurinate, and alkali tritaurinate.
6. The process according to claim 1 , wherein an acid is used to adjust the pH of taurine solution or crystalline suspension to a range of 6 to 8.
7. The process according to claim 1 , wherein the taurine solution is passed through a bed of acidic ion exchanger.
8. The process according to claim 1 , wherein the yield of taurine from ammonium isethionate is from 90% to nearly quantitative.
9. The process according to claim 1 , wherein the alkali metals are lithium, sodium, or potassium.