Method of production of a methionine salt

1. A method for continuous production of a methionine salt, comprising:

supplying a solution comprising 5-(2-methylmercaptoethyl)-hydantoin to a topmost plate of a reactive rectification column;

conducting an alkaline hydrolysis of the 5-(2-methylmercaptoethyl)-hydantoin to obtain a methionine salt in the reactive rectification column;

wherein an alkaline circulating solution is supplied to the reactive rectification column on a plate located under the topmost plate,

the reactive rectification column comprises from 15 to 25 vertically stacked plates,

each of the vertically stacked plates comprises an area permeable to a gas a downcomer and a weir separating the gas permeable area from the downcomer,

a temperature of a gas phase at a top of the reactive-rectification column is from 160° C. to 170° C., and

a basicity value of the methionine salt solution at a bottom outlet of the reactive rectification column is from 2.2 to 2.8 mol base per kg of the methionine salt solution.

2. The method according to claim 1 , wherein the alkaline circulating solution comprises an alkali metal carbonate.

3. The method according to claim 1 , further comprising: removing water, ammonia and CO 2 from the top of the reactive rectification column;

condensing the ammonia (NH 3 ); and employing the ammonia in a synthesis of 5-(2-methylmercaptoethyl)-hydantoin.

4. The method according to claim 1 , wherein a concentration of ammonia at the bottom of the rectification column is less than 120 ppm.

5. The method according to claim 1 , wherein the 5-(2-methylmercaptoethyl)-hydantoin is obtained by reacting 3-methylmercaptopropionaldehyde and hydrogen cyanide in a reactive absorber and then in a second reactor.

6. The method according to claim 5 , wherein the second reactor comprises a flow tube.

7. The method according to claim 1 , wherein the temperature of the reaction mixture at the bottom outlet of the reactive-rectification column is from 180° C. to 190° C.

8. The method according to claim 1 , a pressure of the alkaline hydrolysis is from 8 bar(excess) to 10 bar(excess).

9. The method according to claim 1 , wherein a heating and stripping medium in the reactive-rectification column comprises steam.

10. The method according to claim 1 ,

a height of the weir is 100 mm or more.

11. The method according to claim 1 , wherein the alkaline circulating solution is fed on a 2nd vertically stacked plate from the top.

12. The method according to claim 1 , wherein the alkaline circulating solution comprises potassium carbonate.

13. The method according to claim 1 , further comprising removing allyl alcohol at the top of the reactive rectification column.