Process for the preparation of ethylene glycol from sugars

Abstract

A process for the preparation of ethylene glycol and other C.sub.1-C.sub.3 hydroxy compounds comprising the steps of hydrogenating a composition comprising C.sub.1-C.sub.3 oxygenate compounds. In particular the process is suitable for hydrogenating a composition comprising different C.sub.1-C.sub.3 oxygenate compounds, such as the product from a thermolytic fragmentation of a sugar composition.

Claims

1. A process for the preparation of a C.sub.1-C.sub.3 hydroxy compound, comprising the steps of: a) providing an oxygenate feed composition comprising a C.sub.1-C.sub.3 oxygenate compound in a total concentration of at least 20% by weight of oxygenate feed composition; and b) providing a chemical reactor comprising i. an inlet zone in fluid communication with ii. a reaction zone comprising a heterogeneous hydrogenation catalyst material in fluid communication with iii. an outlet zone; then c) feeding the oxygenate feed composition of step a) to the reactor inlet zone i) of step b) to obtain an initial total concentration of C.sub.1-C.sub.3 oxygenate compound of less than 20% by weight of reactor fluid in the reaction zone ii) of step b), wherein change in the total concentration of C.sub.1-C.sub.3 oxygenate compound from greater than 20% by weight to less than 20% by weight is due to dilution by the reactor fluid; and d) in the reaction zone ii) reacting the C.sub.1-C.sub.3-oxygenate compound with hydrogen in the presence of the catalyst material to obtain a C.sub.1-C.sub.3 hydroxy compound; and then e) recovering from the outlet zone iii) the hydroxy product composition comprising the C.sub.1-C.sub.3 hydroxy compound, wherein the oxygenate feed composition of step a) comprises two or more C.sub.1-C.sub.3 oxygenate compounds selected from the group consisting of glycolaldehyde, glyoxal, pyruvaldehyde, acetol and formaldehyde.

2. The process according to claim 1, wherein the total concentration of C.sub.1-C.sub.3 oxygenate compound in the oxygenate feed composition is at least 25% by weight of oxygenate feed composition.

3. The process according to claim 1, wherein the oxygenate feed composition of step a) comprises at least 20% by weight of glycolaldehyde and at least 5% by weight of pyruvaldehyde.

4. The process according to claim 1, wherein the total concentration by weight of C.sub.1-C.sub.3 hydroxy compound in the hydroxy product composition is at least 50% by weight of the total concentration C.sub.1-C.sub.3 oxygenate compound in the oxygenate feed composition.

5. The process according to claim 1, wherein the selectivity of ethylene glycol (mol/mol C.sub.2) is at least 80%.

6. A process for the preparation of a C1-C3 hydroxy compound, comprising the steps of: a) providing an oxygenate feed composition comprising a C1-C3 oxygenate compound in a total concentration of at least 20% by weight of oxygenate feed composition; and b) providing a chemical reactor, wherein the chemical reactor is a continuously stirred tank reactor, comprising i. an inlet zone in fluid communication with ii. a reaction zone comprising a heterogeneous hydrogenation catalyst material in fluid communication with iii. an outlet zone; then c) feeding the oxygenate feed composition of step a) to the reactor inlet zone i) of step b) to obtain an initial total concentration of C1-C3 oxygenate compound of less than 20% by weight of reactor fluid in the reaction zone ii) of step b); and d) in the reaction zone ii) reacting the C1-C3-oxygenate compound with hydrogen in the presence of the catalyst material to obtain a C1-C3 hydroxy compound; and then e) recovering from the outlet zone iii) the hydroxy product composition comprising the C1-C3 hydroxy compound, wherein the oxygenate feed composition of step a) comprises two or more C1-C3 oxygenate compounds selected from the group consisting of glycolaldehyde, glyoxal, pyruvaldehyde, acetol and formaldehyde, and wherein, the selectivity of propylene glycol (mol/mol C.sub.3) is at least 60%.

7. The process according to claim 1, wherein the hydroxy product composition of step e) comprises one or more C.sub.1-C.sub.3 hydroxy compounds selected from the group consisting of methanol, ethylene glycol and propylene glycol.

8. The process according to claim 1, wherein the C.sub.1-C.sub.3 oxygenate compound is a C.sub.2-C.sub.3 oxygenate compound.

9. The process according to claim 1, wherein the C.sub.1-C.sub.3 hydroxy compound is a C.sub.2-C.sub.3 hydroxy compound.

10. The process according to claim 1, wherein the catalyst material of step b) comprises a metal component selected from the group consisting of ruthenium, ruthenium alloy, rhenium, rhodium, iridium, palladium, platinum, copper and nickel.

11. The process according to claim 1, wherein the catalyst material of step b) comprises a support material.

12. The process according to claim 1, wherein the catalyst material of step b) comprises ruthenium on carbon or copper on carbon.

13. The process according to claim 1, wherein the catalytic reaction of step d) is conducted under an initial hydrogen partial pressure of at least 0.5 bar.

14. The process according to claim 1, wherein the reaction of step d) is conducted at a temperature in the range of from 50-350 C.

15. The process according to claim 1, wherein the reaction of step d) is conducted at a temperature in the range of from 200-250 C. and a hydrogen partial pressure in the range of from 0.5 to 5 bar.

16. The process according to claim 1, wherein the reaction of step d) is conducted at a temperature in the range of from 60-120 C. and a hydrogen partial pressure in the range of from 60 to 140 bar.

17. The process according to claim 1, wherein step d) is conducted under conditions to provide liquid phase hydrogenation of the oxygenate compound and a solvent is present in the reaction zone of step d).

18. The process according to claim 17, wherein the solvent comprises one or more of the compounds selected from the group consisting of water, methanol, ethanol, ethylene glycol and propylene glycol.

19. The process according to claim 1, wherein the process is performed under continuous conditions.

20. The process according to claim 1, wherein the reactor of step c) is a plug flow reactor.

21. The process according to claim 1, wherein a fraction of the hydroxy product composition recovered in step e) is transferred to the reaction zone ii) of step b).

22. The process according to claim 1, wherein the reactor of step c) is a stirred tank reactor.

23. The process according to claim 1, wherein the hydrogenation product composition of step e) is subjected to a purification step to recover the C.sub.1-C.sub.3 hydroxy compound.

24. The process according to claim 23, wherein unreacted hydrogen recovered in the purification step, is recycled to the reaction zone ii) of step b).

25. A process for the preparation of a C.sub.1-C.sub.3 hydroxy compound, comprising the steps of: i. providing a feedstock solution of a sugar composition; ii. exposing the feedstock of a) to thermolytic fragmentation to produce a fragmentation product composition comprising a C.sub.1-C.sub.3 oxygenate compound; and iii. optionally conditioning the fragmentation product composition; and then iv. subjecting the fragmentation product composition of step ii) or iii) to the process according to claim 1, wherein the fragmentation product composition is the oxygenate feed composition of step a).

26. The process according to claim 25, wherein the sugar composition is selected from one or more of the monosaccharides fructose, xylose, glucose, mannose, galactose, arabinose; and/or the disaccharides sucrose, lactose, maltose.

27. The process according to claim 25, wherein the feedstock solution of step i) is a solution of a sugar in a solvent comprising from 20-95 wt. % of sugar.

28. The process according to claim 25, wherein the solvent comprises one or more of the compounds selected from the group consisting of water, methanol, ethanol, ethylene glycol and propylene glycol.

29. The process according to claim 1, wherein the oxygenate feed of step a) comprises a C.sub.1-C.sub.3 oxygenate compound in a total concentration of at least 50% by weight of oxygenate feed composition.

30. The process according to claim 29, wherein a change in the total concentration of C.sub.1-C.sub.3 oxygenate compound from greater than 50% by weight to less than 20% by weight is due to dilution by the reactor fluid.

31. The process according to claim 1, wherein the chemical reactor is a continuously stirred tank reactor.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1: C.sub.3/C.sub.6 ratio plotted as a function of initial pyruvaldehyde concentration (40 mg of Ru/C added as catalyst). C.sub.3 comprises acetol and propylene glycol and C.sub.6 comprises all C.sub.6 byproducts formed by aldol condensation of pyruvaldehyde.

DEFINITIONS

(2) The term oxygenate feed composition is meant to refer to the oxygenate containing fluid passing through the inlet of the reactor used for conducting the hydrogenation. When the oxygenate composition is obtained from a thermolytic fragmentation of a sugar composition, it may in addition to the C.sub.1-C.sub.3 oxygenate compounds, contain other compounds e.g. organic acids such as acetic acid, formic acid, glycolic acid and/or lactic acid; furans such as furfural and/or 5-(hydroxymethyl)furfural; and solvents such as water.

(3) In the present context, the term C.sub.1-C.sub.3 oxygenate compound is meant to refer to an organic compound containing between 1 and 3 carbon atoms and at least one carbonyl bond (ketone or aldehyde).

(4) The term oxygenate feed composition comprising a C.sub.1-C.sub.3 oxygenate compound is meant to refer to an oxygenate feed composition comprising one or more C.sub.1-C.sub.3 oxygenate compounds. It may also comprise minor amounts of other organic compounds.

(5) In the present context, a gas phase hydrogenation is meant to refer to a hydrogenation wherein the substrate (here the C.sub.1-C.sub.3 oxygenate compound) is essentially in a gaseous form in the reaction zone of the catalytic material. For example, at least 80 wt. %, such as at least 90, 92, 94 or 96 wt. %, is in the gaseous form. Accordingly, this means that 80-100 wt. %, such as 90-100, 92-100, 94-100 or 96-100 wt %, is in the gaseous form.

(6) In the present context, a liquid phase hydrogenation is meant to refer to a hydrogenation wherein the substrate (here the C.sub.1-C.sub.3 oxygenate compound) is essentially in liquid solution in the reaction zone of the catalytic material. For example, at least 80 wt. %, such as at least 90, 92, 94 or 96 wt. %, is in the liquid form. Accordingly, this means that 80-100 wt. %, such as 90-100, 92-100, 94-100 or 96-100 wt. %, is in the liquid form.

(7) In the present context, a reaction zone is meant to refer to the area around the catalyst wherein the oxygenate feed composition is brought into contact with the hydrogenation catalyst. In certain embodiments the reaction zone may be defined by the walls of the chemical reactor. In a continuous reactor, the reaction zone may be defined by the reactor walls and the inlet and the outlet. In liquid hydrogenation the reaction zone is the liquid reactor fluid. In gaseous hydrogenation the reaction zone is defined by the reactor walls and if inlet and outlet is present, by the end of the inlet and the beginning of the outlet.

(8) The term hydrogenation product composition is meant to refer to the hydroxy containing fluid resulting from the hydrogenation reaction. When the hydrogenation product composition is obtained from hydrogenating the fragmentation product of a thermolytic fragmentation of a sugar composition, it may in addition to the C.sub.1-C.sub.3 hydroxy compounds, contain other compounds e.g. organic acids such as acetic acid, formic acid, glycolic acid and/or lactic acid; furans such as furfural and/or 5-(hydroxymethyl)furfural; and solvents such as water.

(9) Concentrations given in percentages are to be understood as weight % (i.e. weight of x per total weight), where nothing else is stated.

(10) In the present context, the term C.sub.1-C.sub.3 hydroxy compound is meant to refer to an organic compound which contains between 1 and 3 carbon atoms and at least one hydroxyl group (alcohol) and which may be produced by hydrogenation of a C.sub.1-C.sub.3 oxygenate compound.

(11) The term hydrogenation product composition comprising a C.sub.1-C.sub.3 hydroxy compound is meant to refer a hydrogenation product composition comprising one or more C.sub.1-C.sub.3 hydroxy compounds.

(12) The term catalytic material is to be understood as any material which is catalytically active. This is also the meaning of the term catalyst. All terms may be used interchangeably.

(13) The terms Cu on carbon and Cu/C are meant to refer to a catalytically active material having a support of carbon (such as activated carbon/carbon nanotubes/graphene/fullerenes) with copper particles deposited on the support. As the skilled person will know, it is mainly the surface of the Cu particles which provide the catalytic activity. Accordingly, a large Cu particle surface area is desirable.

(14) The term Recovering is meant to refer either to collecting the hydrogenation product composition or to directing the hydrogenation product composition to a subsequent step, such as to a purification unit.

(15) The term yield is in the present context meant to refer to the molar fraction of C.sub.1-C.sub.3 oxygenate compound which is converted into its corresponding C.sub.1-C.sub.3 hydroxy compound (i.e. C.sub.1 to C.sub.1; C.sub.2 to C.sub.2; and C.sub.3 to C.sub.3).

(16) The term conversion is in the present context meant to refer to the molar fraction of C.sub.1-C.sub.3 oxygenate compound which has reacted during the hydrogenation process to form either the desired C.sub.1-C.sub.3 hydroxy compound or other products.

(17) The term selectivity is meant to refer to the molar fraction of desired product formed per substrate converted. In the present context the substrate for a C.sub.1 hydroxy compound is only considered to be the C.sub.1 oxygenate compounds present in the oxygenate feed composition; for a C.sub.2 hydroxy compound the substrate is only considered to be the C.sub.2 oxygenate compounds present in the oxygenate feed composition; and for a C.sub.3 hydroxy compound the substrate is only considered to be the C.sub.3 oxygenate compounds present in the oxygenate feed composition. The selectivity may be calculated as yield divided by conversion.

(18) The term initial (hydrogen partial pressure/oxygenate molar fraction/oxygenate concentration etc.) is meant to refer to the partial pressure or molar fraction at the time when it first meets the catalytic material.

(19) The term continuous conditions is meant to refer to truly continuous conditions (such as in a fluid bed reactor or packed bed reactor, optionally with recycle of the hydrogenation product composition to the feed stream or to the reactor inlet) but it is also meant to refer to semi-continuous conditions such as repeatedly feeding small portions of the oxygenate feed composition to the reactor fluid and repeatedly collecting small portions of the hydroxy product composition from the reactor outlet.

(20) The reactor fluid is meant to refer to the fluid present in the reaction zone, including both unreacted oxygenate compounds, the hydroxy compounds formed and any solvent or diluent present.

EXAMPLE

Example 1: Effect of Initial C.SUB.1.-C.SUB.3 .Oxygenerate Concentration

(21) The experiment was performed in an autoclave. 3.1 g C.sub.1-C.sub.3 oxygenate feed composition was fed to the autoclave. The concentration of C.sub.1-C.sub.3 oxygenates in the C.sub.1-C.sub.3 oxygenate feed composition varied according to Table 1 below. The C.sub.1 oxygenates present in the C.sub.1-C.sub.3 oxygenate feed composition were mainly formaldehyde (FA). The C.sub.2 oxygenates present in the C.sub.1-C.sub.3 oxygenate feed composition were mainly glycolaldehyde (GA) and glyoxal. The C.sub.3 oxygenates present in the C.sub.1-C.sub.3 oxygenate feed composition were mainly pyruvaldehyde (PA) and acetol. Accordingly the initial glycolaldehyde (GA) concentration ranged from 16 g/l to 264 g/l. The C.sub.1-C.sub.3 oxygenate feed composition was hydrogenated for 16 hours at 80 C. and 90 bar H.sub.2 with 0.040 g of 5% Ru/C catalyst. The catalyst amount was kept constant in all experiments meaning that the relative amount of catalyst compared to substrate increased with decreasing oxygenate concentration. After hydrogenation, the hydrogenation product composition was recovered and the content of ethylene glycol (EG) and propylene glycol (PG) was determined using standard methods. The yield of EG was calculated as moles of EG formed per mole of glycolaldehyde and glyoxal in the feed composition. The yield of PG was calculated as moles of PG formed per mole of pyruvaldehyde and acetol in the feed composition. Table 1 presents an overview of the results. Full conversion of GA was obtained at GA concentrations up to 129 g/l (entry 1-4). From these experiments it can be seen that the yield of ethylene glycol (EG) decreased with increasing oxygenate concentration. The higher GA concentrations of 196 g/l and 264 g/l did not reach full conversion after 16 hours (entry 5 and 6), the drop in EG selectivity was seen to continue to 82% and 74%, respectively. The trend observed with respect to EG yield was similar for the PG yield.

(22) TABLE-US-00001 TABLE 1 Hydrogenation of C.sub.1-C.sub.3 oxygenate feed compositions of different oxygenate concentrations C.sub.3 in C.sub.2 in C.sub.1 in C.sub.2 EG EG PG Entry feed feed feed conversion yield selectivity yield 1 2.4 g/l 16 g/l 1.4 g/l 100% 96% 96% 71% 2 4.7 g/l 31 g/l 2.7 g/l 100% 95% 95% 68% 3 9 g/l 62 g/l 5.4 g/l 100% 93% 93% 61% 4 20 g/l 129 g/l 11 g/l 100% 85% 85% 50% 5 29 g/l 196 g/l 17 g/l 96% 78% 82% 45% 6 40 g/l 264 g/l 23 g/l 44% 33% 74% n.a.

Example 2: Continuous Process

(23) A continuously stirred tank reactor (CSTR) setup was used to perform the hydrogenation of an oxygenate mixture. The CSTR consisted of a 500 ml autoclave, with the possibility of feeding liquid and gas to the reactor, as well as withdrawing reaction liquid and gas from the reactor. The hydrogenation was performed by loading 20 g of a 5 wt. % Ru/C catalyst in a Robinson-Mahoney catalyst basket, which was mounted in the autoclave. The autoclave was then filled with 300 ml of water, sealed, and flushed with nitrogen. The reactor was pressurized to 80 bar, using hydrogen, and the temperature increased to 90 C. Hydrogen was supplied to the reactor at a rate of 80 Nml/min, while gas was withdrawn from the reactor at a rate sufficient to keep the pressure constant. An oxygenate feed with the composition given in Table 2 was fed to the reactor at a rate of 0.1 g/min, while liquid product was withdrawn at the same rate to give a constant amount of reaction liquid in the reactor. Due to the vigorous stirring of the reactor, the feed being supplied to the reactor was almost immediately completely mixed with the liquid in the reactor upon entering the reactor, essentially diluting the feed with the product composition. As the reactor, under these conditions, operate at high conversion (i.e. >95%), this means that the substrate concentration in the reaction zone is constantly low. When steady state had been achieved, the content of ethylene glycol (EG) and propylene glycol (PG) in the recovered hydrogenation product composition was determined using standard methods. A yield of EG of 85% was achieved. A yield of PG of 70% was achieved.

(24) TABLE-US-00002 TABLE 2 Concentration of oxygenates in feed. Compound Concentration [g/L] Glycolaldehyde 244 Formaldehyde 38 Pyruvaldehyde 22 Glyoxal 16 Acetol 14