Process for preparing esters of lactic acid, and 2-hydroxy-3-butenoic acid or α-hydroxy methionine analogues 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 means for stabilizing a Lewis acid catalyst for use in a continuous reaction process wherein 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 one or more esters of lactic acid and 2-hydroxy-3-butenoic acid 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 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, 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. A process according to claim 1 , wherein the yield of the one or more lactic acid esters decreases by up to 0.25% per hour on stream on average, wherein the yield is amount of ester relative to the amount of sugar.
3. A process according to claim 1 , wherein the yield of the one or more lactic acid esters decreases by up to 0.10% per hour on average, wherein the yield is amount of ester relative to the amount of sugar.
4. A process according to claim 1 , wherein the yield of the one or more lactic acid esters decreases by up to 5% after 50 hours on stream, wherein the yield is amount of ester relative to the amount of sugar.
5. A process according to claim 1 , wherein the yield of the one or more lactic acid esters is greater than 40% after 50 hours on stream, wherein the yield is amount of ester relative to the amount of sugar.
6. A process according to claim 1 , wherein the solid Lewis acid catalyst is calcined after 450 hours of continuous flow process.
7. A process according to claim 1 , wherein the solid Lewis acid catalyst comprises an active metal selected from one or more of the group consisting of Sn, Ti, Pb, Zr, Ge and Hf.
8. 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.
9. 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.
10. 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.
11. A process according to claim 1 , wherein the yield of 2-hydroxy-3-butenoic acid ester is greater than 12% after 50 hours on stream, wherein the yield is amount of ester relative to the amount of sugar.
12. A process according to claim 1 , wherein an alkaline earth metal or alkali metal ion is present in the process.
13. 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.
14. A process according to claim 1 , wherein the temperature of the process is from 140° C. to 200° C.
15. 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.
16. 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.