Cyclic process for producing taurine from monoethanolamine

1. A process for producing monoethanolamine sulfate, comprising:

(a) adding monoethanolamine to an aqueous solution comprised of ammonium sulfate to form an aqueous solution comprised of monoethanolamine sulfate and ammonia; and

(b) heating the aqueous solution to remove the ammonia to yield an aqueous solution comprised of the monoethanolamine sulfate.

2. The process according to claim 1 , wherein the molar ratio of the monoethanolamine to the ammonium sulfate in the aqueous solution is from 0.5:1 to 5.0:1.

3. The process according to claim 1 , wherein the molar ratio of the monoethanolamine to the ammonium sulfate in the aqueous solution is from 1.9:1 to 2.1:1.

4. The process according to claim 1 , wherein the temperature for heating the aqueous solution comprised of the monoethanolamine sulfate and ammonia to remove the ammonia from the aqueous solution is from 50° to 150° C.

5. A cyclic process for producing taurine from monoethanolamine, comprising:

(a) adding monoethanolamine to an aqueous solution comprised of ammonium sulfate and monoethanolamine sulfate to form an aqueous solution comprised of monoethanolamine sulfate and ammonia and heating the aqueous solution to remove the ammonia to yield an aqueous solution comprised of the monoethanolamine sulfate;

(b) adding sulfuric acid to the aqueous solution comprised of the monoethanolamine sulfate of step (a) to form an aqueous solution comprised of monoethanolamine bisulfate;

(c) heating the aqueous solution comprised of the monoethanolamine bisulfate of step (b) and optionally added monoethanolamine bisulfate prepared from the reaction of monoethanolamine and sulfuric acid to yield 2-aminoethyl hydrogen sulfate ester;

(d) reacting the 2-aminoethyl hydrogen sulfate ester with ammonium sulfite in an aqueous solution to yield an aqueous solution comprised of taurine and ammonium sulfate;

(e) separating the taurine and the ammonium sulfate by means of cooling crystallization and a solid-liquid separation to give an aqueous mother liquor solution comprised of monoethanolamine sulfate, ammonium sulfite, and the dissolved ammonium sulfate; and

(f) removing the ammonium sulfite from the aqueous mother liquor solution to obtain an aqueous solution comprised of the ammonium sulfate and monoethanolamine sulfate and returning the aqueous solution to step (a).

6. The process according to claim 5 , wherein the ammonium sulfite in the aqueous mother liquor is removed by oxidation to ammonium sulfate by using at least one oxidant selected from the group consisting of air, oxygen, hydrogen peroxide, ammonium persulfate, sodium persulfate, potassium persulfate, sodium percarbonate, potassium percarbonate, ammonium perborate, sodium perborate, potassium perborate, sodium hypochlorite, and potassium hypochlorite.

7. The process according to claim 6 , wherein the oxidant is hydrogen peroxide.

8. The process according to claim 5 , wherein the ammonium sulfite is removed from the aqueous mother liquor solution by adding an acid to the aqueous mother liquor solution to form ammonium sulfate and to remove sulfur dioxide, wherein the acid is selected from the group consisting of sulfuric acid, hydrochloric acid, nitric acid, and phosphoric acid.

9. The process according to claim 5 , wherein the ammonium sulfite in the aqueous mother liquor solution is removed by using at least one precipitating agent selected from the group consisting of calcium chloride, calcium bromide, calcium oxide, calcium hydroxide, calcium sulfate, barium oxide, barium hydroxide, and barium chloride.

10. The process according to claim 5 , wherein the molar ratio of the sulfuric acid to the monoethanolamine sulfate is from 0.5:1 to 5.0:1.

11. The process according to claim 5 , wherein the molar ratio of the sulfuric acid to the monoethanolamine sulfate is from 0.9:1 to 1.0:1.