Background : Ethylene glycol can be prepared by a variety of routes in ^¬ cluding from monosaccharides, e.g. sugars, via fermentation and hydrogenolysis processes, or by hydroformylation .

The fermentation route is a five-step process wherein glu- cose is fermented to ethanol and carbon dioxide, followed by conversion of ethanol to ethylene, ethylene to ethylene oxide and ethylene oxide to ethylene glycol. One disad ^¬ vantage of this method is that per mole of glucose ferment ^¬ ed, two moles of carbon dioxide are produced together with two moles of ethanol; this has the effect that a theoreti ^¬ cal maximum of 67% of the carbon present in the glucose can be transformed to ethanol.

The hydrogenolysis route is a two-step process wherein glu- cose is reduced to sorbitol followed by hydrogenolysis of sorbitol to ethylene glycol, as illustrated by US 6,297,409 Bl and US 2008/0228014 Al . Significant quantities of pro ^¬ pylene glycol, compared to ethylene glycol, are formed via the hydrogenolysis process. Additionally, the amount of catalyst used is significant and appears difficult to reac ^¬ tivate once spent. Furthermore, the byproducts formed, in particular butanediols, are difficult to separate from the desired product. In particular, the industrially favorable method of distillation for separation (purification) pur- poses is extremely difficult to apply as the byproducts have very similar boiling points to the final product, and the desired product may react further, as illustrated in US2014/0039224 Al and US 5,393,542 Bl .

The hydroformylation route is a two-step route wherein gly- colaldehyde is prepared from formaldehyde, carbon monoxide and hydrogen, followed by hydrogenation of the glycolalde- hyde to ethylene glycol, as illustrated in US 4,496,781 Bl . There appears to be several extraction steps present in or- der to separate formaldehyde from glycolaldehyde and pro ^¬ ceed with the hydrogenation reaction.

Therefore it is desirable to provide an alternative, im ^¬ proved, high yielding and industrially feasible process for the preparation of ethylene glycol from sugars. An addi ^¬ tional advantage would be the use of greater than 67% of the sugar carbon atoms present in the final product or a commercially valuable byproduct. It could be conceived that ethylene glycol may be prepared via a process comprising two steps; such as the preparation of glycolaldehyde from sugars and its subsequent hydrogena ^¬ tion to glycols. The two steps of the proposed processes appear to be independently successful as illustrated in the following paragraphs.

It is known that sugars may be pyrolysed to obtain a pyrol- ysis product composition comprising oxygenate compounds such as glycolaldehyde US 7,094,932 B2; the pyrolysis prod- uct composition typically comprises C1-C3 oxygenate com ^¬ pounds, including formaldehyde, glycolaldehyde, glyoxal, pyruvaldehyde and acetol. The main product of this reaction is glycolaldehyde (US 7,094,932 B2). Water is the solvent of the reaction.

It is also known that pure glycolaldehyde may be hydrogen- ated to ethylene glycol. US 4,200,765 Bl discloses hydro- genation of glycolaldehyde under severe conditions: at high pressure [3000 psi (ca. 345 bar)], high temperature [150 °C] , with an organic solvent [N-methyl pyrrolidine] and a palladium on carbon [Pd/C] catalyst for a prolonged period [5 h] . US 4,321,414 Bl and US 4,317,946 Bl disclose the hy- drogenation of glycolaldehyde with a homogenous ruthenium catalyst and US 4,496,781 Bl discloses a continuous flow hydrogenation at low pressure [500 psi (ca. 35 bar)], at high temperature [160 °C] with a ruthenium on carbon cata- lyst [Ru/C] in ethylene glycol and trace acetonitrile as solvent .

As illustrated, the two steps, pyrolysis of glucose to ob ^¬ tain, inter alia glycolaldehyde, and hydrogenation of pure glycolaldehyde, appear to be independently possible. Howev ^¬ er, in order for the pyrolysis product composition to be hydrogenated, laborious separation processes must be em ^¬ ployed to remove formaldehyde from the pyrolysis product composition as formaldehyde is a known poison of hydrogena- tion catalysts US 5,210,337 Bl . US 5,393,542 Bl discloses an exemplary purification process comprising multiple distillation steps followed by a solvent-induced precipitation to obtain glycolaldehyde. Therefore, it is not possible to hydrogenate the product of the pyrolysis step (the pyroly- sis product composition) directly, as formaldehyde is pre ^¬ sent in the composition in a significant amount. In addition to the requirement of removing formaldehyde, which would increase the number of process steps required, it would also be a great advantage industrially to use a solvent that is non-toxic, for example water. Therefore it would be a significant advantage to be able to carry out the hydrogenation step in the presence of formaldehyde, us ^¬ ing a non-toxic solvent and in the solvent of the previous (pyrolysis) reaction. With regard to hydrogenation of glycolaldehyde, although there is the provision of suitable reaction conditions to obtain a high yield in organic solvents, the reaction with water as a solvent appears to be less successful. US

5,393,542 Bl discloses thermal degradation of glycolalde- hyde (2-hydroxyacetaldehyde) when subjected to temperatures of 90 °C or higher and where water is the solvent.

EP 0 002 908 Bl discloses the variation in yield (conversion and selectivity) of the hydrogenation of glycolalde- hyde reaction with the use of various catalysts in an aque ^¬ ous solution at 110 °C : Raney Nickel [100% conversion 49.4% selectivity], 10% Pd/C [62% conversion, 61% selectivity] and 10% Pt/C [100% conversion, 73% selectivity] . An addi ^¬ tional disadvantage of catalysts used in liquid water is the strain on the catalyst. In particular, at high tempera ^¬ tures (>160 °C) many supports are not stable and will dis ^¬ solve, degrade or the surface area is reduced; Energy & Fuels 2006, 20, 2337-2343. Hence, special catalysts are needed and the long-term catalyst performance is often problematic, consequently, the catalyst must be replaced frequently (ca. 3-6 months). Consequently, mild reaction conditions are favorable in order to ensure longevity of the catalyst, in particular on an industrial scale and in industrial conditions.

In addition, the choice of catalyst may affect the decompo- sition of glycolaldehyde when in the presence of the cata ^¬ lyst; US 5,210,337 Bl discloses the problem of glycolalde ^¬ hyde ^x unzipping' to form formaldehyde and consequently poi ^¬ soning the hydrogenation catalyst. It is also possible that glycolaldehyde may self-condense or condense with another C1-C3 oxygenate compound, also illustrated in US 5,210,337 Bl . Additionally, the choice of catalyst and stability of the glycol product may affect the degree of reduction of the glycolaldehyde. It is possible that a catalyst may re ^¬ duce the glycolaldehyde to ethanol or ethane, i.e. over re- duce the glycolaldehyde.

Additionally, it is known that an increase in temperature, concentration of the substrate and amount and identity of catalyst present affects the yield (conversion and selec- tivity) of hydrogenation reactions of glycolaldehyde. Hand ^¬ book of Heterogeneous Catalytic Hydrogenation for Organic Synthesis, Shigeo Nishimura, ISBN: 978-0-471-39698-7, April 2001. As demonstrated, an industrial scale process for preparing ethylene glycol from sugars via pyrolysis of sugars and subsequent hydrogenation is hindered from two perspectives. The first is the requirement to remove formaldehyde from the pyrolysis product composition in order to enable suc- cessful hydrogenation. The second is the provision of mild reaction conditions that are high yielding. Furthermore, in order to provide a process that is industrially and commer- cially feasible, it is desirable to provide a high yielding two-step process that utilizes non-toxic solvents and pro ^¬ duces a minimal amount of byproducts that are separable from the ethylene glycol product using industrially feasi- ble techniques. The ability to separate byproducts from the ethylene glycol product enables the ethylene glycol to be used in processes such as polymer production. Polymer production requires substrates to be in a highly pure form.

It has now been discovered that the pyrolysis product com ^¬ position obtainable from the pyrolysis of sugars may be hy- drogenated in a high yield, in mild conditions, with mini ^¬ mal byproducts and directly from a pyrolysis product compo- sition comprising formaldehyde.

Disclosure of the Invention:

It has been discovered that it is possible to subject the pyrolysis product composition obtainable from the pyrolysis of sugars to hydrogenation conditions and to obtain a high yield (high conversion and high selectivity) in mild reac ^¬ tion conditions and with minimal byproducts and without re ^¬ moving formaldehyde (i.e. Ci-oxygenate compounds) prior to the hydrogenation reaction. Furthermore, it has been dis ^¬ covered that ethylene glycol is more stable at higher pres ^¬ sures and temperatures and a smaller amount of the byprod ^¬ uct 1 , 2-butanediol is produced. The present invention provides a process for the prepara ^¬ tion of a composition comprising ethylene glycol comprising the steps of: a. Pyrolysing a sugar to obtain a pyrolysis product composition; and

b. Hydrogenating the pyrolysis product composi ^¬ tion of step a. in the presence of a catalyst, hydrogen and a solvent to obtain a (hydrogen- ated) product composition.

c. Optionally separating (purifying) ethylene

glycol from the (hydrogenated) product compo ^¬ sition obtained in step b.

An aspect of the present invention is the presence of Ci- oxygenates present in Step a. Step a. may read: Pyrolysing a sugar to obtain a pyrolysis product composition compris ^¬ ing Ci-oxygenates . Alternatively, step a. may read: Pyro- lysing a sugar to obtain a pyrolysis product composition comprising formaldehyde.

The product of the present invention may be the (hydrogen ^¬ ated) product composition of step b. comprising ethylene glycol. (Hydrogenated) product composition means the prod ^¬ uct of step b. comprising ethylene glycol. The (hydrogenat ^¬ ed) product composition of step b. may further comprise un- reacted substrate. Alternatively, the product of the pre ^¬ sent invention may be the product of step b. that has been purified, i.e. the product of step c.

Sugar means one or more sugars selected from the group con ^¬ sisting of monosaccharides and disaccharides ; preferably, sugar means one or more sugars selected from the group con- sisting of glucose, sucrose, fructose, xylose, mannose, arabinose and galactose. Preferably the sugar is a monosac ^¬ charide and is glucose. The sugar may be in the form of a solution, wherein the sugar solution comprises a sugar and a solvent.

The solvent of the sugar solution is a solvent selected from the group consisting of: water or water and alcohol. Alcohol means one or more alcohol selected from the group consisting of methanol and ethanol. For example, the sugar solution may be present as an aqueous sugar solution, pref ^¬ erably an aqueous glucose solution.

The solvent of step b. is a solvent selected from the group consisting of: water; alcohol or water and alcohol. Alcohol means one or more alcohol selected from the group consist ^¬ ing of methanol, ethanol, ethylene glycol and propylene glycol.

The solvent of step b. may be a mixture of water and alco ^¬ hol. Where the solvent is water and alcohol, the water and alcohol are in a ratio of equal to or greater than 95:5, 90:10, 80:20, 70:30, 60:40, 50:50, 40:60 and 30:70.

The pyrolysis product composition of step a. may also be known as a crude pyrolysis product composition. The pyroly ^¬ sis product composition comprises oxygenate compounds such as glycolaldehyde and may be prepared according to US

7,094,932 B2. The pyrolysis product composition comprises C ₁ -C3 oxygenate compounds. C ₁ -C3 oxygenate compounds means oxygenated compounds comprising a carbon chain length of one, two or three carbon atoms. For example, Ci oxygenate compounds comprise a carbon chain length of one carbon at ^¬ om, such as formaldehyde and formic acid; C2 oxygenate com ^¬ pounds comprise a carbon chain length of two carbon atoms, such as glycolaldehyde, glyoxal and acetic acid; C3 oxygen ^¬ ate compounds comprise a carbon chain length of three car ^¬ bon atom, such as pyruvaldehyde and acetol. C ₁ -C3 oxygen ^¬ ate compound composition means a composition comprising one or more compounds selected from the group consisting of formaldehyde, glycolaldehyde, glyoxal, pyruvaldehyde and acetol. Preferably the pyrolysis product composition com ^¬ prises C2 oxygenate compounds. Typically, the C2~oxygenate compound component of the composition comprising C ₁ -C3 oxy- genate compounds is for example 10 wt% or greater, 30 wt % or greater. Where the pyrolysis product composition of step a. comprises formaldehyde and glycolaldehyde, the wt/wt ra ^¬ tio of the formaldehyde to glycolaldehyde present in the pyrolysis product composition of step a. may be from about 1:2 to about 1:20; from 1:2 to 1:20; from 1:7 to 1:14; from 1:8 to 1:12; from 1:9 to 1:10. The range from 1:2 to 1:20 may comprise the range from 1:2 to 1.69; from 1:2 to about 1:7; from 1:2 to 1:7. The range from 1:2 to 1:20 may comprise the range from 1:14 to 1:20; from about 1:14 to 1:20; from 1:14.1 to 1:20. The wt/wt ratio of the formaldehyde to glycolaldehyde present in the pyrolysis product composition of step a. may be from 1:2 to 1:20, for example for pyroly ^¬ sis product compositions obtainable from xylose and fruc ^¬ tose sugar substrates.

The hydrogenation of step b. is carried out in the presence of a catalyst comprising a catalyst metal component such as ruthenium, ruthenium alloy, palladium, platinum or nickel. The catalyst metal component is supported by a support such as carbon. Known catalysts include ruthenium on a carbon support. For example, the hydrogenation of step b. may be carried out in the presence of a catalyst such as ruthenium on a carbon support catalyst. For example, the hydrogena- tion of step b. may be carried out in the presence of cata ^¬ lyst such as a 5% or 10% ruthenium on a carbon support cat ^¬ alyst. Examples of ruthenium alloy catalysts comprising 0.5 - 2% ruthenium are disclosed in WO 2014/066052 Al .

The catalyst of step b. may be present in the reaction so ^¬ lution in a wt/wt ratio of formaldehyde : catalyst metal com ^¬ ponent of from 1:1 to 15:1, from 1:1 to 11:1; from 1:1 to 10:1; from 1:1 to 7:1; from 1:1 to 5:1; from 3.0:1 to 15:1; from 3.1:1 to 15:1; from 3.2:1 to 15:1.

The hydrogenation of step b. may be carried out at a pres ^¬ sure of from about 30 bar to 90 bar, from 30 bar to 120 bar, from 40 bar to 120 bar, from 40 bar to 140 bar, from about 90 bar to 150 bar, preferably from 50 bar to 150 bar. Pressure means hydrogen partial pressure.

The hydrogenation of step b. may be carried out at a tem- perature of from 40 to 160 °C, from 50 to 140 °C, from 60 to 130 °C, preferably from 80 to 120 °C .

The yield (conversion and selectivity) of ethylene glycol from C ₂ ~oxygenate compounds of the pyrolysis product of step a. is greater than 40%, greater than 50%, greater than 70%.

The conversion of C ₂ ~oxygenate compounds of the pyrolysis product composition of step a. to ethylene glycol (step b.) may be 70% or greater; 80% or greater. Conversion means the transformation of C2-oxygenate compounds of the pyrolysis product composition to another com ^¬ pound or compounds . The selectivity of C2~oxygenate of the pyrolysis product composition of step a. to ethylene glycol may be 75% or greater, 85% or greater, preferably 95% or greater.

Selectivity means the transformation of C2~oxygenate com- pounds of the pyrolysis product composition to ethylene glycol rather than other compounds such as ethanol or ethane .

The product of step b. comprises a 1 , 2-butanediol (1,2- BDO) :ethylene glycol wt/wt ratio may be equal to or less than 0.01:1, 0.005:1, 0.004:1, 0.003:1.

The process of the present invention is two steps. 'Two step' process means the conversion of sugars to ethylene glycol via two chemical transformations: the pyrolysis of sugars and the hydrogenation of glycolaldehyde obtainable from the pyrolysis of glucose. A further embodiment of the present invention is a two-step process wherein the pyroly ^¬ sis product composition of step a. is directly hydrogenated in step b.. For example the pyrolysis product composition of step a. comprising C ₁ -C3 oxygenate compounds is used as the starting composition for the hydrogenation step (step b.) . For example, the product of step a. is hydrogenated. Purifying means separating the specific chemical products of the (hydrogenated) product composition of step b., e.g. separating ethylene glycol, propylene glycol and other com- ponents. Exemplary separation processes are disclosed in US 8, 177, 980 B2 and US 2014/0039224 Al . Such separation (purification) processes may be chromatography and distillation. Ethylene glycol prepared according to the present invention may be used as a chemical. For example, ethylene glycol may be used as a monomer in the preparation of polymers includ ^¬ ing polyethylene terephthalate (PET) , polyester resins, fi ^¬ bers and films. Ethylene glycol may also be used as a de- icing agent, coolant, in particular in refrigeration apparatus, antifreeze agent or solvent. As described on:

http : //www . dow . com/ethyleneglycol /prod/meg . htm

Examples :

Example 1 :

A pyrolysis product composition comprising C1-C3 oxygenate compounds was obtained by pyrolysis of a 10 wt% agueous glucose (D-glucose monohydrate ; Sigma Aldrich) solution as described in US 7,094,932 B2. The composition of the pyrol ^¬ ysis product composition is given in Table 1.

Table 1: Composition of the pyrolysis product composition of Example 1.

Examples 2-4 : The pyrolysis product composition of Example 1 and de ^¬ scribed 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 sub- sequently pressurized with hydrogen to the respective pres ^¬ sures 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 tempera ^¬ ture and the decrease in hydrogen pressure was noted.

The hydrogenated product mixture was isolated from the cat ^¬ alyst by filtration and analyzed by HPLC and GC .

The maximum theoretical yield of ethylene glycol was based on hydrogenation of both glyoxal and glycolaldehyde to eth ^¬ ylene glycol.

Table 2.

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 Al [1, 2-BDO:ethylene glycol ratio of 0.08].

Examples 5-8 :

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 pres ^¬ sure 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.

Table 3.

Table 3 shows an increased stability of ethylene glycol and propylene glycol with an increase in pressure under hydro- genation reaction conditions. Example 9: Glycol aldehyde dimer (1.0 g) was dissolved in demineral- ized water (14.5 g) . The solution was loaded into an auto ^¬ clave 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 tempera- ture and the decrease in hydrogen pressure was noted.

The product mixture was isolated from the catalyst by fil ^¬ tration and analyzed by HPLC and GC . Example 10 :

The method of Example 9 was repeated under a pressure of 90 bar . Example 11 :

The method of Example 9 was repeated at a temperature of 100 °C. 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 in ^¬ crease in pressure of the reaction results in a reduction of 1 , 2-butanediol (1,2-BDO) formed, resulting in an in- creased purity of the ethylene glycol product in milder conditions . Table 4.

Yield of

H ₂ presTemp. Catalyst

Time ethylene 1,2- sure (°C) loading

( ) glycol BDO/ethylene (bar) (g)

(wt%) glycol

Ex 9 90 80 °C 3 0.2 g >98% 0.000045

Ex 80 °C 3 95% 0.00025

30 0.2 g

10

Ex 100 3 90% 0.00098

30 0.2 g

11 °C