Cyclic process for producing taurine from monoethanolamine

A process for recovering monoethanolamine sulfate from an aqueous mother liquor solution, comprising:

• (a) removing alkali sulfite from an aqueous mother liquor solution comprised of monoethanolamine sulfate, alkali sulfate, and alkali sulfite to yield an aqueous solution comprised of the monoethanolamine sulfate and alkali sulfate, wherein the alkali is lithium, sodium, potassium, or a mixture thereof;
• (b) concentrating the aqueous solution of step (a) to crystallize the alkali sulfate;
• and
• (c) separating the alkali sulfate of step (b) by solid-liquid separation to yield an aqueous solution comprised of the monoethanolamine sulfate, wherein the concentration of the monoethanolamine sulfate is at least 50% by weight.

A process for producing taurine, comprising:

• (a) removing ammonium sulfite from an aqueous mother liquor solution comprised of monoethanolamine sulfate, ammonium sulfate, and ammonium sulfite to yield an aqueous solution comprised of the monoethanolamine sulfate and ammonium sulfate;
• (b) concentrating the aqueous solution of step (a) to crystallize the ammonium sulfate;
• (c) separating the ammonium sulfate of step (b) by solid-liquid separation to yield an aqueous solution comprised of the monoethanolamine sulfate;
• (d) adding sulfuric acid to the aqueous solution comprised of the monoethanolamine sulfate of step (c) to form an aqueous solution comprised of monoethanolamine bisulfate, and optionally mixing the aqueous solution comprised of the monoethanolamine bisulfate with additional monoethanolamine bisulfate prepared by reacting monoethanolamine and sulfuric acid;
• (e) heating the aqueous solution comprised of the monoethanolamine bisulfate of step (d) to yield 2-aminoethyl hydrogen sulfate ester;
• (f) reacting the 2-aminoethyl hydrogen sulfate ester of step (e) with ammonium sulfite in an aqueous solution to yield taurine;
• and
• (g) separating the taurine by cooling crystallization and solid-liquid separation to yield an aqueous mother liquor solution comprised of monoethanolamine sulfate, ammonium sulfate, residual taurine, and ammonium sulfite.

A process for producing taurine, comprising:

• (a) removing alkali sulfite from an aqueous mother liquor solution comprised of monoethanolamine sulfate, alkali sulfate, and alkali sulfite to yield an aqueous solution comprised of the monoethanolamine sulfate and alkali sulfate, wherein the alkali is lithium, sodium, potassium, or a mixture thereof;
• (b) concentrating the aqueous solution of step (a) to crystallize the alkali sulfate;
• (c) separating the alkali sulfate of step (b) by solid-liquid separation to yield an aqueous solution comprised of the monoethanolamine sulfate;
• (d) adding sulfuric acid to the aqueous solution of step (c) to form an aqueous solution comprised of monoethanolamine bisulfate, and optionally mixing the aqueous solution comprised of the monoethanolamine bisulfate with additional monoethanolamine sulfate prepared by reacting monoethanolamine and sulfuric acid;
• (e) heating the aqueous solution comprised of the monoethanolamine bisulfate of step (d) to yield 2-aminoethyl hydrogen sulfate ester;
• (f) reacting the 2-aminoethyl hydrogen sulfate ester of step (e) with an alkali sulfite in an aqueous solution to yield taurine;
• and
• (g) separating the taurine of step (f) by cooling crystallization and solid-liquid separation to yield an aqueous mother liquor solution comprised of monoethanolamine sulfate, alkali sulfate, residual taurine, and alkali sulfite.