Process for preparing esters of α-hydroxy methionine from sugars
A continuous flow process for the preparation of one or more esters of lactic acid and 2-hydroxy-3-butenoic acid or α-hydroxy methionine analogs from a sugar in the presence of a solid Lewis acid catalyst and a solvent comprising an organic solvent and water. The invention provides a stabilized Lewis acid catalyst for use in a continuous reaction process, where the water is present in an amount of up to or equal to 10 vol. % of the organic solvent.
1. A continuous flow process for the preparation of an α-hydroxy methionine analogue from a sugar selected from one or more of the group consisting of glucose, fructose, mannose, sucrose, xylose, erythrose, erythrulose, threose and glycolaldehyde, in the presence of a compound comprising sulphur, solid Lewis acid catalyst and a solvent comprising an organic solvent and water, wherein the water is present in an amount of up to or equal to 10 vol. % of the organic solvent, and wherein the solid Lewis acid catalyst has a framework structure, which is selected from the group consisting of BEA, MFI, FAU, MOR, FER, MWW, MCM-41 and SBA-15.
2. The process according to claim 1 , wherein the compound comprising sulfur is selected from the group consisting of C 1 -C 5 alkyl thiol, C 1 -C 5 alkyl thiol salts, dimethylmercaptan and dimethyl disulfide.
3. The process according to claim 1 , wherein the vol. % of water present in the organic solvent is from 0.25 to 10 vol. %.
4. A process according to claim 1 , wherein the solid Lewis acid catalyst is calcined after 450 hours.
5. A process according to claim 1 , wherein the solid Lewis acid comprises an active metal selected from one or more of the group consisting of Sn, Ti, Pb, Zr, Ge and Hf.
6. A process according to claim 1 , wherein the solid Lewis acid catalyst is selected from the group consisting of Sn-BEA, Sn-MFI, Sn-FAU, Sn-MOR, Sn-MWW, Sn-MCM-41 and Sn-SBA-15.
7. A process according to claim 1 , wherein the solid Lewis acid catalyst comprises Sn and the loss of Sn from the solid Lewis acid catalyst is less than or equal to 0.11% of the initial amount of Sn per hour on stream.
8. A process according to claim 1 , wherein the solid Lewis acid catalyst comprises Sn and the loss of Sn from the solid Lewis acid catalyst is less than 8% of the initial amount of Sn after 50 hours on stream.
9. A process according to claim 1 , wherein the yield of α-hydroxy methionine analogue ester is greater than 20% after 10 hours on stream.
10. A process according to claim 1 , wherein an alkaline earth metal or alkali metal ion is present in the process.
11. A process according to claim 1 , wherein the solvent is selected from one or more of the group consisting of methanol, ethanol, 1-propanol, 1-butanol and isopropanol.
12. A process according to claim 1 , wherein the temperature of the process is from 140° C. to 200° C.
13. A process according to claim 1 , wherein at least a fraction of the water is introduced to the solvent by mixing the organic solvent with an aqueous sugar solution.
14. A process according to claim 1 , wherein the aqueous sugar solution is a sugar syrup with a sugar dry matter content of 30% or higher.
15. A continuous flow process for the preparation of an alpha-hydroxy methionine analogue from a sugar selected from one or more of the group consisting of glucose, fructose, mannose, sucrose, xylose, erythrose, erythrulose, threose and glycolaldehyde, in the presence of a compound comprising Sulphur, a solid Lewis acid catalyst and a solvent comprising an organic solvent and water, wherein the vol. % of water present in the organic solvent is from 0.25 to 10 vol. % and at least a fraction of the water is introduced to the solvent by mixing the organic solvent with an aqueous sugar solution, and wherein the solid Lewis acid catalyst is Sn-BEA.
16. A process according to claim 15 , wherein the alpha-hydroxy methionine analogue is 2-hydroxy-4-(methylthio)butanoic acid.
17. A process according to claim 15 , wherein the alpha-hydroxy methionine analogue is selected from the group consisting of 2-hydroxy-4-(methylthio)butanoic acid methyl ester, 2-hydroxy-4-(methylthio)butanoic acid ethyl ester, 2-hydroxy-4-(methylthio)butanoic acid propyl ester, 2-hydroxy-4-(methylthio)butanoic acid butyl ester, 2-hydroxy-4-(methylthio)butanoic acid isopropyl ester, 2-hydroxy-4-(methylthio)butanoic acid pentyl ester, 2-hydroxy-4-(methylthio)butanoic acid hexyl ester, and 2-hydroxy-4-(methylthio)butanoic acid heptyl ester, 2-hydroxy-4-(methylthio)butanoic acid octyl ester and 2-hydroxy-4-(methylthio)butanoic acid 2-ethylhexyl ester.