Continuous hydrolysis process for the preparation of 2-hydroxy-4-methylthiobutanoic acid

A process for the preparation of 2-hydroxy-4-methlthiobutanoic acid comprising:

• introducing sulfuric acid into a first reactor comprising a continuous stirred tank reactor;
• introducing 2-hydroxy-4-methylthiobutanenitrile into said first reactor;
• continuously hydrolyzing 2-hydroxy-4-methyl-thiobutanenitrile within said first reactor to produce an intermediate aqueous hydrolysis solution containing 2-hydroxy-4-methylthiobutanamide;
• continuously introducing the intermediate aqueous hydrolysis solution exiting said first reactor and a water stream into a second continuous stirred tank reactor such that a substantial portion of 2-hydroxy-4-methylthiobutanamide contained in said intermediate solution is hydrolyzed in the second continuous stirred tank reactor to form a finishing reaction solution;
• continuously introducing the finishing reaction solution into a plug flow reactor;
• and
• continuously hydrolyzing 2-hydroxy-4-methylthiobutanamide within said plug flow reactor to produce an aqueous hydrolyzate product solution containing 2-hydroxy-4-methylthiobutanoic acid.

A process for the preparation of 2-hydroxy-4-methylthiobutanoic acid comprising:

• concurrently introducing 2-hydroxy-4-methylthiobutyanenitrile, concentrated sulfuric acid stream having a strength of between about 70% by weight and about 99% by weight, and water into a vessel in which 2-hydroxy-4-methylthiobutanenitrile is hydrolyzed;
• hydrolyzing 2-hydroxy-4-methylthiobutanenitrile within said vessel to produce an intermediate aqueous hydrolysis solution containing 2-hydroxy-4-methylthiobutanamide;
• and
• hydrolyzing 2-hydroxy-4-methylthiobutanamide to produce an aqueous hydrolyzate product solution containing 2-hydroxy-4-methylthiobutanoic acid.