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 the gas phase in the presence of a copper on carbon catalyst.

Claims

1. A process for the preparation of ethylene glycol, comprising the steps of: a) providing an oxygenate feed composition comprising a C.sub.1-C.sub.3 oxygenate compound, wherein the composition comprising C.sub.1-3-oxygenate compounds comprises glycolaldehyde and at least one of glyoxal and carboxylic acid, and b) providing a hydrogenation catalyst material comprising Cu on carbon, then c) reacting the composition of step a) with hydrogen in the presence of the catalyst of step b) and under conditions to provide gas phase hydrogenation of the oxygenate compound to obtain a hydrogenation product composition comprising ethylene glycol, and then d) recovering the hydrogenation product composition.

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

3. The process according to claim 1, wherein the oxygenate feed composition of step a) is brought into the gas phase by atomizing the oxygenate feed using an atomization nozzle.

4. The process according to claim 1, wherein the oxygenate feed composition comprises glycolaldehyde, glyoxal and at least one of the C.sub.1-C.sub.3 oxygenate compounds selected from the group consisting of pyruvaldehyde, acetol and formaldehyde.

5. The process according to claim 1, wherein the oxygenate feed composition of step a) is brought into the gas phase prior to step c).

6. The process according to claim 1, wherein the hydrogenation catalyst material of step b) has a loading of Cu on carbon in the range of from 0.1 to 70 weight percent.

7. The process according to claim 1, wherein step c) is conducted under an initial hydrogen partial pressure of at least 0.5 bar.

8. The process according to claim 1, wherein the initial oxygenate molar fraction in step c) is from 0.01 to 0.5.

9. The process according to claim 1, wherein step c) is conducted under a total pressure of from 0.8-500 bar.

10. The process according to claim 1, wherein step c) is conducted under a temperature in the range of from 100-400° C.

11. The process according to claim 1, wherein step c) of reacting the oxygenate feed composition with hydrogen in the presence of the hydrogenation catalyst material is conducted in a chemical reactor.

12. The process according to claim 11, wherein the oxygenate feed composition is fed to the chemical reactor at a ratio of flow rate by weight of oxygenate feed composition of step a) to weight of catalytic material of step b) in the range of from 0.001 to 1000 g C.sub.1-C.sub.3 oxygenate compounds per g catalyst per hour.

13. The process according to claim 1, wherein the hydrogenation product composition of d) is subjected to a purification step.

14. The process according to claim 1, wherein unreacted hydrogen recovered after step d), is recycled to step c).

15. The process according to claim 1, wherein the process is conducted in a Berty reactor, a packed bed reactor, a fixed bed reactor, a multi-tubular reactor or a fluid bed reactor.

16. A process for the preparation of ethylene glycol, 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).

17. The process according to claim 16, wherein the sugar composition is selected from fructose, xylose, glucose, mannose, galactose, sucrose, and lactose.

18. The process according to claim 16, wherein the feedstock solution of step i) is a solution of a sugar in a solvent comprising from 20-95 wt % of sugar.

19. The process according to claim 16, wherein the solvent comprises one or more of the compounds selected from the group consisting of water, methanol, ethanol, ethylene glycol and propylene glycol.

20. The process according to claim 1, wherein step c) is conducted under a total pressure of from 0.8-10 bar, wherein step c) is conducted under a temperature in the range of from 150-400° C., wherein the hydrogenation product composition of step d) comprises ethylene glycol.

21. The process according to claim 1, wherein the oxygenate feed composition comprises glycolaldehyde and glyoxal.

22. The process according to claim 1, wherein the oxygenate feed composition comprises glycolaldehyde and a carboxylic acid.

23. The process according to claim 1, wherein the oxygenate feed composition comprises glycolaldehyde and a carboxylic acid selected from the group consisting of acetic acid, formic acid, lactic acid and glycolic acid.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1: Selectivity towards ethylene glycol and productivity obtained in the hydrogenation of a C.sub.1-C.sub.3 oxygenate feed composition over a Cu/C catalyst at 220° C.

(2) FIG. 2: Selectivity towards ethylene glycol and productivity obtained in the hydrogenation of a C.sub.1-C.sub.3 oxygenate feed composition over a commercial Cu/ZnO/Al.sub.2O.sub.3 catalyst at 220° C.

DEFINITIONS

(3) 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 feed 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-hydroxymethylfurfural; and solvents such as water.

(4) 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).

(5) 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.

(6) 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 reactor. 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.

(7) The term “hydrogenation product composition” is meant to refer to the hydroxy compound 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-hydroxymethylfurfural; and solvents such as water.

(8) 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.

(9) 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.

(10) 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.

(11) 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.

(12) 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.

(13) 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).

(14) 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.

(15) 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.

(16) The term “productivity” is meant to refer to the amount by weight of product produced over the catalyst per weight of catalyst per hour. So if ethylene glycol (EG) is the desired product, the productivity is considered the amount by weight of EG produced over the catalyst per weight of catalyst per hour. If propylene glycol (PG) is the desired product, the productivity is considered the amount by weight of PG produced over the catalyst per weight of catalyst per hour. If both EG and PG are the desired products, the productivity is considered the amount by weight of EG and PG produced over the catalyst per weight of catalyst per hour.

(17) The term “initial hydrogen partial pressure” and the term “initial oxygenate molar fraction” are meant to refer to the partial pressure or molar fraction at the time when it first meets the catalytic material.

(18) 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 hydroxyl product composition from the reactor outlet.

EXAMPLE

Example 1: Gas Phase Hydrogenation of Oxygenate Feed Composition in the Presence of Cu/C

(19) An aqueous fragmentation mixture (fragmentation product composition) containing 80 g/L of glycolaldehyde, 7 g/L of formaldehyde, 5 g/L of pyruvaldehyde, 1 g/L of acetol and 1 g/L of glyoxal was prepared as described in U.S. Pat. No. 7,094,932: A bed of sand was fluidized with nitrogen and heated to 520° C. A 10 wt. % solution of glucose in water was injected into the bed through an atomization nozzle. After passing through the bed, the product was cooled in a condenser and the liquid product collected. The mixture was distilled to remove high boiling impurities and was subjected to the hydrogenation by the process described below without any further pretreatment.

(20) The hydrogenation was performed as follows: 25 g of the catalyst was loaded in a fixed bed reactor (I.D. 22 mm) and reduced in situ at 220° C. for 6 hours in a flow of 5% hydrogen in nitrogen. The temperature was maintained at the same level after reduction. The flow was changed to 100% hydrogen and increased to 6.5 Nl/min. The substrate (fragmentation product composition/oxygenate feed composition) was injected into the reactor, at a rate of 0.25 g/min, from the top through a two fluid nozzle, using the hydrogen stream to atomize the liquid. The pressure at the reactor inlet was at these conditions 1.05 bar, giving a hydrogen partial pressure at the reactor inlet of 1.0 bar.

(21) After passing through the catalyst bed, the product was cooled in a condenser and the liquid product collected (hydrogenation product composition). In FIG. 1 the selectivity towards ethylene glycol is shown for the gas phase hydrogenation of the fragmentation mixture over Cu/C catalyst. As can be seen the selectivity is 90-100% towards ethylene glycol.

Example 2: Gas Phase Hydrogenation of Oxygenate Feed Composition in the Presence of Cu/ZnO/Al.SUB.2.O.SUB.3

(22) A commercial Cu/ZnO/Al.sub.2O.sub.3 gas phase hydrogenation catalyst was used for hydrogenating the oxygenates (aldehydes) of the fragmentation mixture according to the same procedure as described above. The yields are not as good. In FIG. 2 the selectivity towards ethylene glycol is shown for the gas phase hydrogenation of the fragmentation mixture over a commercial Cu/ZnO/Al.sub.2O.sub.3 catalyst. As can be seen the selectivity is only 75-80% towards ethylene glycol.

(23) The hydrogenation of an C.sub.1-C.sub.3 oxygenate feed composition over catalysts based on copper supported on active carbon gives significantly improved yields. In fact, nearly quantitative yields of ethylene glycol are obtainable as shown here. The productivity of ethylene glycol (EG) of the active carbon based catalyst is approx. 30% higher than the conventional catalyst; a very surprising discovery considering the copper loading is 10 times higher for the conventional catalyst. Thus the activity on a metal basis is 13 times higher for the active carbon based catalyst. As the metal costs constitute a significant portion of the total catalyst cost, such a dramatic reduction in the required amount of metal translates into a significantly cheaper catalyst.

Example 3: Direct Gas Phase Hydrogenation of the Gaseous Fragmentation Product Composition

(24) During the fragmentation process, a high-boiling, black, and highly viscous byproduct is formed, which must be removed from the fragmentation product composition. The byproduct is a complex mixture of various oxygenates and saccharides, which has partly oligomerized forming a tar-like substance. This tar-like product is considered an unwanted byproduct and an object of the current invention is to minimize the formation of this.

(25) The tar-like substance can be removed by vacuum distillation. Heating an oxygenate feed composition or a hydrogenation product composition to 150° C. at 20 mbar in a rotary evaporator allows for the collection of the desired C.sub.1-C.sub.3 oxygenate compounds or C.sub.1-C.sub.3 hydroxy compounds as the distillate, while the tar-like substance is collected as the residue.

(26) Removing the tar-like substance by vacuum distillation from a fragmentation product composition/oxygenate feed composition produced by a method similar to the first step of example 1 yields approx. 5 wt. % of the total dry matter content of the oxygenate feed composition as a tar-like substance.

(27) The C.sub.1-C.sub.3 oxygenate feed composition produced in a manner similar to the first step of example 1 may be hydrogenated in the liquid phase over a Ru/C catalyst as described in WO 2016/001169 A1. The tar-like substance may then be removed by vacuum distillation of the hydrogenation product composition, which yields approx. 19 wt. % of the total drymatter content of the hydrogenation product composition as a tar-like substance.

(28) The oxygenate feed composition produced in a manner similar to the first step in example 1 may alternatively be hydrogenated in the gas phase by the procedure described in part 2 of example 1 without an intermediate step of condensing and subsequently evaporating the oxygenate feed composition. This can be performed by directing the C.sub.1-C.sub.3 oxygenate compound containing gas stream leaving the fragmentation reactor directly to the hydrogenation reactor. A hydrogenation product composition is collected by condensing the products leaving the hydrogenation reactor. The tar-like substance may then be removed by vacuum distillation of the hydrogenation product composition, which yields approx. 3 wt. % of the total dry matter content of the hydrogenation product composition as a tar-like substance.

(29) As can be seen, performing the hydrogenation directly after the fragmentation reaction, without an intermediate step of condensing and optionally evaporating the oxygenate feed composition prior to conducting a gas phase hydrogenation leads to a significant reduction of the amount of produced tar-like substance.