PROCESS FOR PRODUCING TAURINE
The present invention is directed to an improved process for producing taurine from ammonium isethionate without generating or using any acid within the cyclic process as recited in the claims appended hereto.
1 . A process for producing taurine, comprising:
(a) adding excess ammonia and a catalytic amount of alkali hydroxide to a mother liquor solution comprising alkali isethionate; wherein the catalytic amount of alkali hydroxide is produced in a bipolar membrane electrodialysis of step (c) and wherein the mother liquor solution comprising alkali isethionate is produced in step (d);
(b) subjecting the solution of step (a) to an ammonolysis, and optionally removing excess ammonia, to yield a solution comprising alkali taurinate;
(c) passing the solution comprising alkali taurinate of step (b) through a bipolar membrane electrodialysis to produce a catalytic amount of alkali hydroxide and a solution comprising taurine and alkali taurinate; and
(d) adding ammonium isethionate to the solution comprising taurine and alkali taurinate of step (c) to obtain taurine and a mother liquor solution comprising alkali isethionate.
2 . The process according to claim 1 , wherein the bipolar membrane electrodialysis is carried out in a three-chamber configuration of taurine, alkali taurinate, and alkali hydroxide, respectively.
3 . The process according to claim 1 , wherein the bipolar membrane electrodialysis is carried out in a two-chamber configuration of alkali hydroxide and alkali taurinate.
4 . The process according to claim 1 , wherein the catalytic amount of alkali hydroxide produced in the bipolar membrane electrodialysis of step (c) is at least equal to the total molar amount of taurinates in the mother liquor solution of step (a).
5 . The process according to claim 1 , wherein the catalytic amount of alkali hydroxide produced in the bipolar membrane electrodialysis of step (c) is from 15% to 35% of the molar amount of alkali isethionate in the mother liquor solution.
6 . The process according to claim 1 , wherein the molar yield of taurine is greater than 90% on the basis of ammonium isethionate.
7 . The process according to claim 1 , wherein the taurine does not contain salt of sulfate or chloride as impurity.
8 . A process for producing taurine, comprising:
(a) adding excess ammonia and a catalytic amount of alkali hydroxide to a mother liquor solution comprising alkali isethionate; wherein the catalytic amount of alkali hydroxide is produced in a bipolar membrane electrodialysis of step (c) and wherein the mother liquor solution is produced in step (d);
(b) subjecting the solution of step (a) to an ammonolysis, and optionally removing excess ammonia, to yield a solution comprising alkali taurinate;
(c) passing part of the solution comprising alkali taurinate of step (b) through a bipolar membrane electrodialysis to produce a catalytic amount of alkali hydroxide and a solution comprising taurine; and
(d) adding ammonium isethionate to the other part of the solution comprising alkali taurinate of step (b) to obtain taurine and a mother liquor solution comprising alkali isethionate.
9 . The process according to claim 8 , wherein the bipolar membrane electrodialysis is carried out in a three-chamber configuration of taurine, alkali taurinate, and alkali hydroxide, respectively.
10 . The process according to claim 8 , wherein the bipolar membrane electrodialysis is carried out in a two-chamber configuration of alkali hydroxide and alkali taurinate.
11 . The process according to claim 8 , wherein the amount of the solution comprising alkali taurinate passing through the bipolar membrane electrodialysis is from 15% to 35% of the solution comprising alkali taurinate.
12 . The process according to claim 8 , wherein the solution comprising taurine of step (c) has a pH of greater than 4.
13 . The process according to claim 8 , wherein the catalytic amount of alkali hydroxide produced in the bipolar membrane electrodialysis of step (c) is at least equal to the total molar amount of taurinates in the mother liquor solution of step (a).
14 . The process according to claim 8 , wherein the catalytic amount of alkali hydroxide produced in the bipolar membrane electrodialysis of step (c) is from 15% to 35% of the molar amount of alkali isethionate in the mother liquor solution.
15 . The process according to claim 8 , wherein the molar yield of taurine is greater than 90% on the basis of ammonium isethionate.