Process for the preparation of ethylene glycol from sugars

Abstract

A process for the preparation of ethylene glycol comprising the steps of pyrolyzing a monosaccharide and hydrogenating the product composition in the presence of a catalyst and a solvent, wherein the pressure of the hydrogenation reaction is 40 bar or greater.

Claims

1. A process for the preparation of ethylene glycol comprising the steps of: a. pyrolysing a sugar to obtain a pyrolysis product composition comprising formaldehyde; and b. hydrogenating the pyrolysis product composition in the presence of a catalyst and a solvent, wherein hydrogenation pressure of the reaction of step b. is 40 bar or greater.

2. A process according to claim 1, wherein the product of hydrogenation reaction is purified.

3. A process according to claim 1, wherein the sugar comprises one or more sugars selected from the group consisting of glucose, sucrose, fructose, xylose, mannose, arabinose and galactose.

4. A process according to claim 1, wherein the solvent is selected from the group consisting of water, alcohol and water and alcohol.

5. A process according to claim 4, wherein the alcohol is selected from one or more of the group consisting of methanol, ethanol, ethylene glycol and propylene glycol.

6. A process according to claim 1, wherein the pyrolysis product composition comprises one or more C.sub.2-3 oxygenate compounds selected from the group consisting of glycolaldehyde, glyoxal, pyruvaldehyde and acetol.

7. A process according to claim 1, wherein the catalyst comprises a metal component selected from the group consisting of ruthenium, ruthenium alloy, palladium, platinum and nickel.

8. A process according to claim 1, wherein the catalyst metal component is present in a ratio of formaldehyde:catalyst metal component of from 1:1 to 1:15.

9. A process according to claim 1, wherein the hydrogenation is carried out at a pressure of from 40 bar to 120 bar.

10. A process according to claim 1, wherein the hydrogenation is carried out at a temperature of from 40? C. to 160? C.

11. A process according to claim 1, wherein the conversion of C.sub.2 oxygenate compounds to ethylene glycol of the hydrogenation is at least 70%.

12. A process according to claim 1, wherein the selectivity of C.sub.2 oxygenate compounds to ethylene glycol of step b. is at least 75%.

13. A process according to claim 1, wherein the pyrolysis product composition of step a. comprises formaldehyde in a ratio of formaldehyde:glycolaldehyde of from 1:2 to 1:20.

14. A process according to claim 1, wherein the product of the hydrogenation comprises a 1, 2-butanediol:ethylene glycol wt/wt ratio of equal to or less than 0.01:1.

15. A process according to claim 1, wherein the process is a two-step process and the pyrolysis product composition of step a. is directly hydrogenated in step b.

16. A process according to claim 1, wherein the pyrolysis product composition comprises one or more C.sub.2 oxygenate compounds selected from the group consisting of glycolaldehyde, glyoxal and acetic acid.

17. A process according to claim 8, wherein the C.sub.2-oxygenate compound of the composition comprising C.sub.1-C.sub.3 oxygenate compounds is 10 wt % or greater.

Description

EXAMPLES

Example 1

(1) A pyrolysis product composition comprising C.sub.1-C.sub.3 oxygenate compounds was obtained by pyrolysis of a 10 wt % aqueous glucose (D-glucose monohydrate; Sigma Aldrich) solution as described in U.S. Pat. No. 7,094,932 B2. The composition of the pyrolysis product composition is given in Table 1.

(2) TABLE-US-00001 TABLE 1 Composition of the pyrolysis product composition of Example 1. Glycolaldehyde Glyoxal Pyruvaldehyde Formaldehyde Acetol 63.4 g/l 4.7 g/l 8.6 g/l 7.7 g/l 2.3 g/l

Examples 2-4

(3) The pyrolysis product composition of Example 1 and described in Table 1 (15.5 g) was loaded into an autoclave along with 5% Ru on carbon catalyst (Sigma Aldrich, 0.20 g). The autoclave was purged 3 times with hydrogen and subsequently pressurized with hydrogen to the respective pressures given in Table 2. The mixture was heated to 80? C. from room temperature over the course of 15 min and stirred for 6 hours. The autoclave was then cooled to room temperature and the decrease in hydrogen pressure was noted.

(4) The hydrogenated product mixture was isolated from the catalyst by filtration and analyzed by HPLC and GC.

(5) The maximum theoretical yield of ethylene glycol was based on hydrogenation of both glyoxal and glycolaldehyde to ethylene glycol.

(6) TABLE-US-00002 TABLE 2 Yield Formalde- H.sub.2 Tem- Cata- of hyde/ 1,2- pres- pera- lyst ethylene catalyst BDO/ sure ture Time load- glycol ratio ethylene (bar) (? C.) (h) ing (%) (wt/wt) glycol Ex 2 15 80 6 0.2 g 12.3% 0.6 Ex 3 30 80 6 0.2 g 18.9% 0.6 Ex 4 90 80 6 0.2 g 88.8% 0.6 0.0021

(7) Examples 2-4 illustrate the significantly increased yield of ethylene glycol with an increase in reaction pressure. Additionally Example 4 demonstrates the low yield of 1,2-BDO produced by the process of the present invention in comparison to the preparation of ethylene glycol via the hydrogenolysis route as illustrated by US 20080228014 A1 [1,2-BDO:ethylene glycol ratio of 0.08].

Examples 5-8

(8) The method as described in Examples 2-4 was repeated using either ethylene glycol or propylene glycol as the substrate [pyrolysis product composition of Example 1] with a pressure of either 30 or 90 bar, a temperature of either 120? C. or 140? C. and a reaction duration of 3 hours. Results are provided in Table 3.

(9) TABLE-US-00003 TABLE 3 H.sub.2 pres- Tempera- Recov- sure ture Time ery of (bar) ? C. (h) glycol Ex 5 Ethylene gly- 30 140 3 59.4% col Ex 6 Ethylene gly- 90 140 3 87.7% col Ex 7 Propylene 30 120 3 87.8% glycol Ex 8 Propylene 90 120 3 96.0% glycol

(10) Table 3 shows an increased stability of ethylene glycol and propylene glycol with an increase in pressure under hydrogenation reaction conditions.

Example 9

(11) Glycol aldehyde dimer (1.0 g) was dissolved in demineralized water (14.5 g). The solution was loaded into an autoclave along with 5% Ru on carbon catalyst (Sigma Aldrich, 0.20 g). The autoclave was purged 3 times with hydrogen and subsequently pressurized with hydrogen to the respective pressures given in Table 2. The mixture was heated to 80? C. from room temperature in the course of 15 min and stirred for 3 hours. The autoclave was then cooled to room temperature and the decrease in hydrogen pressure was noted.

(12) The product mixture was isolated from the catalyst by filtration and analyzed by HPLC and GC.

Example 10

(13) The method of Example 9 was repeated under a pressure of 90 bar.

Example 11

(14) The method of Example 9 was repeated at a temperature of 100? C.

(15) Results of Examples 9 to 11 are provided in Table 4. The amount of 1,2-butanediol (1,2-BDO) present in relation to ethylene glycol is provided. It can be seen that an increase in pressure of the reaction results in a reduction of 1,2-butanediol (1,2-BDO) formed, resulting in an increased purity of the ethylene glycol product in milder conditions.

(16) TABLE-US-00004 TABLE 4 H.sub.2 Yield of pres- Catalyst ethylene 1,2-BDO/ sure Temp. Time loading glycol ethylene (bar) (? C.) (h) (g) (wt %) glycol Ex 9 90 80? C. 3 0.2 g >98% 0.000045 Ex 10 30 80? C. 3 0.2 g 95% 0.00025 Ex 11 30 100? C. 3 0.2 g 90% 0.00098