Continuous hydrolysis process for preparing 2-hydroxy-4-methylthiobutanioc acid or salts thereof

A process for the preparation of 2-hydroxy-4-methylthiobutanoic acid or a salt thereof comprising:

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

A process for the preparation of 2-hydroxy-4-methylthiobutanoic acid or a salt thereof comprising:

• introducing an aqueous mineral acid and 2-hydroxy-4-methylthiobutanenitrile into a nitrile hydrolysis reactor;
• continuously hydrolyzing 2-hydroxy-4-methylthiobutanenitrile within said nitrile hydrolysis reactor to produce a nitrile hydrolysis reactor product stream containing 2-hydroxy-4-methylthiobutanamide;
• continuously introducing water, aqueous mineral acid, and said nitrile hydrolysis reactor product stream into an amide hydrolysis flow reactor;
• and
• continuously hydrolyzing 2-hydroxy-4-methylthiobutanamide within said nitrile hydrolysis reactor to produce a finished aqueous hydrolyzate product containing 2-hydroxy-4-methylthiobutanoic acid.

A process for the preparation of 2-hydroxy-4-methylthiobutanoic acid or a salt thereof comprising:

• concurrently introducing 2-hydroxy-4-methylthiobutanenitrile, a 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, water and sulfuric acid being added in such relative proportions so as to provide a mixture comprising sulfuric acid having a strength between about 50% and about 70% by weight on an organic-free basis;
• hydrolyzing 2-hydroxy-4-methylthiobutanenitrile within said vessel to produce a nitrile hydrolysis product stream containing 2-hydroxy-4-methylthiobutanamide;
• and
• hydrolyzing 2-hydroxy-4-methylthiobutanamide to produce a finished aqueous hydrolyzate product containing 2-hydroxy-4-methylthiobutanoic acid.

A process for the preparation of 2-hydroxy4-methylthiobutanoic acid comprising:

• introducing a mineral 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-methylthiobutyronitrile within said first reactor while continuously removing heat of nitrile hydrolysis from the reacting mixture in said first reactor to produce an intermediate aqueous hydrolysis solution containing 2-hydroxy-4-methylthiobutanamide, the conversion of 2-hydroxy-4-methylthiobutanenitrile to 2-methylthiobutanamide in said first reactor being at least about 90%;
• continuously introducing water and the intermediate aqueous hydrolysis solution into a flow reactor;
• and
• continuously hydrolyzing 2-hydroxy-4-methylthiobutanamide within said flow reactor to produce an aqueous hydrolyzate product solution containing 2-hydroxy-4-methylthiobutanoic acid.

A process for the preparation of 2-hydroxy4-methylthiobutanoic acid comprising:

• introducing a mineral 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-methylthiobutanenitrile within said first reactor while continuously removing heat of nitrile hydrolysis from the reacting mixture in said first reactor to produce an intermediate aqueous hydrolysis solution containing 2-hydroxy-4-methylthiobutanamide, the conversion of 2-hydroxy-4-methylthiobutanenitrile to 2-methylthiobutanamide in said first reactor being at least about 90%;
• 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 flow reactor;
• and
• continuously hydrolyzing 2-hydroxy-4-methylthiobutanamide within said flow reactor while maintaining a substantially single phase reaction mixture substantially throughout said flow reactor to produce an aqueous hydrolyzate product solution containing 2-hydroxy-4-methylthiobutanoic acid.