TWI735409B - Selective conversion of a saccharide containing feedstock to ethylene glycol - Google Patents

Abstract

The present invention relates to a catalytic process for the preparation ethylene glycol from a saccharide containing feedstock. More specifically, the invention relates to a process for the selective conversion of saccharide to ethylene glycol using a catalyst system under acidic conditions, the process comprising conversion of a feedstock comprising at least one saccharide and comprising the steps of: i) contacting the feedstock comprising at least one saccharide with a catalyst system in the presence of hydrogen and a reaction medium; and ii) obtaining ethylene glycol from the reaction mixture; wherein the catalyst system comprises: a) tungsten, molybdenum, or a combination thereof; and b) one or more transition metals selected from IUPAC Groups 8, 9 and 10, and combinations thereof; and wherein step i) is conducted at a pH of from 2.0 to 6.5.

Description

Selective conversion of raw materials containing sugars into ethylene glycol Field of invention

The present invention relates to a catalytic method for preparing ethylene glycol from raw materials containing sugars. More specifically, the present invention relates to a method for selectively converting sugars into ethylene glycol using a catalyst system under acidic conditions.

Background of the invention

Ethylene glycol is a useful polyol, which is primarily used as a raw material for the production of polyethylene terephthalate (PET) and polyethylene naphthalate (PEN) resins. It has also been found to be used in antifreeze, lubricants, plasticizers and surfactants. Historically, ethylene glycol has been prepared from ethylene typically derived from the petroleum industry via ethylene oxide intermediates. With increasing emphasis on the use of renewable raw materials, such as biomass, several alternative methods have emerged to convert biomass-derived sugars into ethylene glycol.

Biomass, more specifically lignocellulosic biomass, is one of the most abundant raw materials on earth. It is mainly composed of cellulose and hemicellulose carbohydrate polymers and lignin. The lignin is an aromatic polymer, and the cellulose and hemicellulose components can be tightly bonded to the aromatic polymer. It is generally believed that there are three different types of lignocellulosic biomass: i) initial biomass; ii) Waste biomass; and iii) energy crops. The initial biomass includes naturally occurring plants and vegetation. Waste biomass corresponds to low-value industrial by-products, usually from agricultural and forestry areas, examples of which include oil palm fronds (OPF), empty fruit bushes (EFB), corn stover, bagasse, And straw, as well as waste from sawmills and paper mills. Energy crops are known to provide high-yield lignocellulosic biomass and are used as raw materials for the production of second-generation biofuels. Examples of these include switch grass and elephant grass.

For example, it is known from US 2010/0255983 that cellulose (the main component of biomass) can be converted into ethylene glycol through a heterogeneous catalytic reaction under hydrogen atmosphere and hydrothermal conditions. When a nickel-tungsten carbide bimetallic catalyst on activated carbon is used as a catalyst and combined with the same pure cellulose starting material, the system achieves 100% cellulose conversion and the ethylene glycol yield is reported to be as high as 62% . However, as reported in CN102731254, when a similar heterogeneous catalytic reaction is applied to corn stover/sorghum stalk biomass raw material instead of pure cellulose, both conversion and ethylene glycol yield are significantly reduced. More specifically, when using corn stover, only 70% of the raw material conversion was achieved and the ethylene glycol yield was only 18%. In addition, in this case, a significant proportion of the second-choice polyol, namely 1,2-propanediol, is formed. Only by extensive pretreatment of the raw material of corn stover, including continuous exposure to steam, strong alkali conditions and H ₂ O ₂ , can the cellulosic material be obtained. When it is used as a raw material, it can lead to the conversion of raw materials and the production of ethylene glycol. The rate has improved significantly. The extensive pretreatment described is time consuming and significantly energy and labor intensive.

US 4,404,411 discloses a method for hydrogenolysis of polyols into ethylene glycol, which uses at least 10 mol% of a strong base in a non-aqueous solvent for Increase the yield of ethylene glycol. US 4,404,411 pointed out that the strong alkali method taught by it may be suitable for in-situ reduction of sugars to polyols. For this consideration, xylitol and sorbitol are pointed out as the preferred polyols because they can be easily obtained from cellulose and hemicellulose which can be derived from biomass.

There is still a need for an alternative method for the selective production of ethylene glycol from sugars relative to other polyols such as 1,2-propanediol, especially when the sugars are contained in raw materials that have not undergone any extensive chemical pretreatment. Under the condition of quality raw materials.

Summary of the invention

The present invention is based on the surprising discovery: when the catalytic reaction is performed at an acidic pH, specifically at a pH from 2.0 to 6.5, the heterogeneous catalytic conversion of sugars can be improved, compared to other multi-components, especially 1,2-propanediol The yield of alcohol and ethylene glycol.

Therefore, in the first aspect, the present invention provides a method for preparing ethylene glycol from a raw material containing at least one sugar, which comprises the following steps: i) making the raw material containing at least one sugar and a catalyst system in hydrogen And contacting in the presence of a reaction medium; and ii) obtaining ethylene glycol from the reaction mixture; wherein the catalyst system contains: a) tungsten, molybdenum, or a combination thereof; and b) one or more transition metals, selected from IUPAC Groups 8, 9 and 10 and several combinations thereof; and wherein step i) is carried out at a pH of from 2.0 to 6.5, preferably at a pH of from 2.0 to 6.5. A pH of 2.25 to 5, more preferably a pH of from 2.5 to 4, still more preferably a pH of from 2.5 to 3.5, and most preferably a pH of from 2.75 to 3.25, such as pH 3.0.

"Sugar", when used here with regard to the ingredients of raw materials, means all kinds of sugars, including monosaccharides, disaccharides, oligosaccharides, and polysaccharides, any of which can be edible or non- Edible, amorphous or crystalline. Examples of monosaccharides include glucose, fructose, galactose, xylose, arabinose, and mannose. Examples of polysaccharides include cellulose, hemicellulose, glycogen, starch, and chitin.

In a preferred embodiment, the sugar contains cellulose, hemicellulose or a combination thereof. More preferably, the sugar contains cellulose. The sugars contained in the raw materials may be amorphous, crystalline, or a combination thereof.

The sugars used in the present invention can be derived from biomass. As used herein, "biomass" means all forms of lignocellulosic biomass. Examples of biomass include oil palm biomass, such as oil palm leaves (OPF) and empty fruit bushes (EFB), corn wormwood, bagasse, straw, energy crops, such as switchgrass and elephant grass, and sawmills and paper Waste from the factory. The biomass according to the present invention may contain cellulose, hemicellulose and lignin as the main components of varying levels. In a preferred embodiment, the biomass is oil palm biomass, more preferably empty fruit bunch (EFB).

The term "biomass" as used herein is intended to cover "primitive biomass" or "coarse biomass", which has not undergone any refining, or only physical refining, such as through shredding / shredding ( chipping and/or dewatering. For the purpose of the present invention, a further form of biomass that is also intended to be covered is "chemically processed biomass" or "pretreated biomass", in which the original or crude biomass has been processed in a certain form, so that it is not intended to be To remove a small amount of lignin and/or hemicellulose is to partially depolymerize any of its polymeric components. Examples of pretreatment include hot water treatment, steam treatment, chemical treatment, biological treatment, catalytic treatment, heat treatment, hydrolysis, and/or thermal cracking.

It has surprisingly been found that the method of the present invention is particularly advantageous for the production of ethylene glycol directly from raw or crude biomass that has not been subjected to any pretreatment, so that it has a good yield and high selectivity relative to 1,2-propanediol. Therefore, in a preferred embodiment, the raw material containing at least one sugar is derived from raw or crude biomass that has not undergone any pretreatment. More preferably, the raw or crude biomass that has not been subjected to any pretreatment is mainly oil palm, such as empty fruit bunch (EFB).

As mentioned above, step i) of the method of the present invention is carried out under acidic conditions, specifically at a pH ranging from 2.0 to 6.5. It has surprisingly been discovered that in terms of hydrogenolysis/hydrogenation of raw materials containing sugars, there are multiple advantages to operating the reaction in this specific pH range. It has been found that this pH level can achieve high-level raw material conversion and ethylene glycol yield. This has the advantage that it eliminates the need for intensive pretreatment of biomass before hydrogenolysis/hydrogenation. For example, the conversion level of the original biomass material has been found to be as high as 85% (the remaining unconverted material mainly contains lignin and ash), and the ethylene glycol yield from the original biomass material has been found to exceed 40%. In the past, high conversion of raw materials and high yields of ethylene glycol were only related to methods performed with purified cellulose raw materials (such as those obtained after continuous exposure to steam, strong alkaline conditions and H ₂ O ₂ ), but were related to the original production process. The quality of raw materials is irrelevant.

In addition, it has also been found that the hydrogenolysis/hydrogenation reaction can be promoted in the aforementioned pH range. Compared with other polyols such as 1,2-propanediol, ethylene two The formation of alcohol. For example, it has been found that the ratio of ethylene glycol to 1,2-propanediol exceeds 4:1 in the embodiments of the present invention. This system is particularly advantageous because ethylene glycol is the preferred precursor for several commercial methods, such as PET preparation, and ethylene glycol has a wider range of polyols than other polyols that can be prepared by hydrogenolysis/hydrogenation of raw materials derived from biomass. application.

Preferably, step i) of the method of the present invention is carried out in the presence of an organic or inorganic acid. Therefore, in one embodiment, step i) of the method of the present invention is carried out in the presence of an inorganic acid selected from hydrochloric acid, sulfuric acid, nitric acid and phosphoric acid, preferably selected from hydrochloric acid and sulfuric acid. In another embodiment, step i) of the method of the present invention is carried out in the presence of an organic acid selected from the group consisting of acetic acid, maleic acid, butyric acid, benzenesulfonic acid, terephthalic acid, Benzoic acid, phthalic acid and salicylic acid. Preferably, the organic acid used is benzenesulfonic acid. When present, the amount of the organic or inorganic acid based on the total weight of the reaction mixture may be from 0.0001 to 2.0 wt.%, preferably 0.001 to 0.1 wt.%, or its amount may be 1 ppm to 20,000 ppm, preferably 10ppm to 1000ppm.

As mentioned above, the catalyst system used in the method of the present invention contains: a) tungsten, molybdenum, or a combination thereof; and b) one or more transition metals selected from IUPAC groups 8, 9 and 10 and several of them combination.

In one embodiment of the present invention, the component a) of the catalyst system contains molybdenum in elemental form or molybdic acid form.

In a preferred embodiment, the component a) of the catalyst system contains tungsten, which is in elemental form or a compound form selected from the following: sodium tungstate, tungsten nitride, tungsten carbide, tungsten phosphide, tungsten oxide, Tungsten sulfide, tungsten chloride, tungsten hydroxide, tungsten bronze, tungstic acid, tungstate, metatungstic acid, metatungstate (e.g. For example, ammonium metatungstate), paratungstate, paratungstate, peroxotungstic acid, peroxotungstate, heteropolytungstic acid, or several combinations thereof.

In a more preferred embodiment, the component a) of the catalyst system contains tungsten in the form of a compound selected from sodium tungstate, tungsten carbide, tungsten bronze, tungstic acid, or combinations thereof. In a still more preferred embodiment, the catalyst system contains tungsten in the form of a compound selected from sodium tungstate, tungstic acid, or combinations thereof.

In one embodiment of the present invention, the component b) of the catalyst system contains a metal selected from iron, cobalt, nickel, ruthenium, rhodium, palladium, iridium, platinum, or combinations thereof. In a preferred embodiment, the component b) of the catalyst system contains a metal selected from nickel, ruthenium, platinum or a combination thereof. In a more preferred embodiment, the component b) of the catalyst system contains nickel.

As mentioned above, the catalyst system used in the method of the present invention contains metallic components a) and b). Without being bound by any particular theory, it is believed that the component a) of the catalyst system, which contains tungsten, molybdenum, or a combination thereof, can promote the hydrogenolysis of sugars contained in the raw material. At the same time, ingredient b), which contains one or more transition metals selected from IUPAC Groups 8, 9 and 10 and several combinations thereof, is believed to promote hydrogenation to form polyols. Both components are therefore active in promoting the formation of ethylene glycol directly from raw materials containing sugars.

The amount of the catalyst system used in the method of the present invention is measured on the basis of elemental tungsten or molybdenum, based on the weight of the raw material containing sugars and the catalytic system, and can range from 0.1 to 10wt.%, preferably 0.3 to 7wt. %. The active metal ratio of each of the catalyst components a) and b), measured on an element basis, is preferably 1:100 to 100:1, more preferably 1:10 to 10:1.

Step i) of the method is carried out at a temperature and pressure suitable for the occurrence of a catalytic reaction and avoiding the thermal decomposition of sugars. Preferably, step i) of the method of the present invention is carried out at a temperature of at least 150°C, more preferably at a temperature of from 200 to 300°C, for example, at a temperature of 245°C. Preferably, step i) of the method of the present invention is carried out under a pressure of 1 to 15 MPa, more preferably under a pressure of 1 to 7 MPa, for example, under a pressure of 5 MPa.

Step i) of the method is carried out in the presence of a reaction medium, which is compatible with the catalytic reaction and typically contains water and/or an organic solvent. In one aspect, the reaction medium contains a solvent selected from water, methanol, ethanol, propanol, butanol, ethylene glycol, glycerol, or a combination thereof. In a preferred embodiment, the reaction medium contains an aqueous solvent. Preferably, the amount of the reaction medium is such that, based on the combined weight of the reaction medium and the raw materials, the raw materials account for between 1 and 30 wt.%. More preferably, the amount of the reaction medium is such that, based on the combined weight of the reaction medium and the raw materials, the raw materials account for between 5 and 15 wt.%.

In some embodiments of the present invention, the raw material containing at least one sugar is derived from pretreated biomass, that is, biomass that has been pretreated before use. The pretreatment may include any of the aforementioned pretreatments known to those skilled in the art.

In a preferred embodiment, the carbohydrate-containing raw material is derived from the biomass that has been pretreated, and the pretreatment includes treating the raw or crude biomass with an alkaline solution at a temperature from 20°C to 110°C The temperature is preferably from 30°C to 80°C. The pretreatment can be carried out within a period of time suitable to achieve the desired level of depolymerization and/or removal of lignin and/or hemicellulose, which can be monitored intermittently. Preferably, the pretreatment is performed on a time scale from 30 minutes to 48 hours, and more preferably on a time scale from 1 to 24 hours. The ratio of the raw material to the alkaline solution is preferably 1:10-1:100.

Preferably, the alkaline solution contains alkali or alkaline earth metal hydroxides, such as sodium hydroxide, lithium hydroxide, potassium hydroxide, calcium hydroxide and/or magnesium hydroxide, and/or the alkaline solution contains hydroxide Ammonium. More preferably, the alkaline solution contains sodium hydroxide. For the purpose of processing biomass, the alkaline solution may contain any appropriate amount of alkali or alkaline earth metal hydroxide or ammonium hydroxide. Preferably, the alkaline solution contains 0.1 to 30 wt.%, more preferably 0.3 to 5 wt.%, of alkali or alkaline earth metal hydroxide or ammonium hydroxide.

The alkaline solution may contain any suitable solvents known to be used for the purpose of processing biomass, including water, methanol and/or ethanol. Preferably, the alkaline solution is aqueous. Once the pretreatment has been performed, the pretreatment biomass can be washed and dried before being fed to the acidic hydrogenolysis/hydrogenation reaction according to the present invention. For example, the pretreated biomass can be washed with water before being heated and dried. The pretreated biomass can be washed with water before being supplied to the acidic hydrogenolysis/hydrogenation reaction according to the present invention and converted into an acidic mixture without any drying step. Alternatively, the pretreated biomass together with the alkaline solution can be directly supplied to the reaction, neutralized and converted into an acidic mixture before being subjected to the hydrogenolysis/hydrogenation according to the method of the present invention.

As the aforementioned pretreatment using alkaline solution, when the acid hydrogenolysis/hydrogenation reaction according to the method of the present invention is continued, it has surprisingly been found that the ethylene glycol yield from biomass-derived raw materials can be further improved. This special biomass pretreatment has also been shown to further improve the option of subsequent hydrogenolysis/hydrogenation reactions Optional for the production of ethylene glycol, rather than alternative polyols. In addition, the pretreatment using alkaline solution followed by the combination of acidic hydrogenolysis/hydrogenation according to the present invention has been found to be particularly good for the selective preparation of ethylene glycol.

In another preferred embodiment, the raw material containing sugars is derived from biomass that has been pretreated. The pretreatment includes treating the raw or crude biomass with a hydrogenation catalyst at a temperature of at least 120°C and To a hydrogen partial pressure of 12MPa. Preferably, the pretreatment using a hydrogenation catalyst is performed at at least 150°C, more preferably from 180 to 270°C. Preferably, the pretreatment using a hydrogenation catalyst is performed under a hydrogen partial pressure of 3 to 7 MPa.

The hydrogenation catalyst used for the pretreatment may be the same as the component b) of the aforementioned catalyst system, and therefore may contain one or more transition metals selected from IUPAC Groups 8, 9 and 10, and several combinations thereof. Preferably, the hydrogenation catalyst used for pretreatment is selected from platinum or palladium. The hydrogenation catalyst may be in an unsupported form or, preferably, in a supported form. Suitable supports for hydrogenation catalysts for pretreatment include carbon, activated carbon, silica, zirconia, alumina, alumina-silica, silicon carbide, zeolite, zirconium oxide, magnesium oxide, zinc oxide, titanium oxide, Several combinations of clay and others. Preferably, the support system is carbon or activated carbon. Preferably, the weight loading of the metal active component on the catalyst is 0.05 to 50%, more preferably 1 to 20%.

The pretreatment can be carried out within a period of time suitable to achieve the desired level of depolymerization and/or removal of lignin and/or hemicellulose, which can be monitored intermittently. Preferably, the pretreatment is performed on a time scale from 10 minutes to 48 hours, and more preferably on a time scale from 30 minutes to 4 hours. The quality ratio of catalyst and raw material is preferably 1:1 to 1:100. The hydrogenation pretreatment is carried out in the presence of a reaction medium that is compatible with the catalytic reaction and typically contains water and/or an organic solvent. The reaction medium may contain a solvent selected from water, methanol, ethanol, propanol, butanol, ethylene glycol, glycerol, or a combination thereof. In a preferred embodiment, the reaction medium contains water.

Once the pretreatment has been performed, the solid product can be collected by vacuum filtration before drying in an oven and sieving to separate the pretreatment feedstock and the catalyst. The pretreatment feedstock can then be fed to the acidic hydrogenolysis/hydrogenation reaction according to the present invention.

As mentioned above, the hydrogenation pretreatment in the presence of a hydrogenation catalyst has surprisingly been found that when the acid hydrogenolysis/hydrogenation reaction according to the method of the present invention is continued, the ethylene glycol yield from biomass-derived raw materials can be further improved. This special biomass pretreatment has also been shown to further improve the selectivity of subsequent hydrogenolysis/hydrogenation reactions for the production of ethylene glycol, rather than alternative polyols. In addition, the hydrogenation pretreatment using a hydrogenation catalyst followed by the acid hydrogenolysis/hydrogenation combination according to the present invention has been found to be particularly good for the selective preparation of ethylene glycol.

According to the present invention, the contacting step i) of the method typically includes: mixing the raw materials, reaction medium, and catalyst system in a sealed reaction vessel; adjusting the pH of the reaction mixture if necessary; introducing hydrogen; and using, for example, a mechanical stirrer, Ultrasonic stirrer or electromagnetic stirrer to stir the resulting mixture. Thereafter, the reaction mixture is left for a suitable period of time to allow the catalytic reaction to continue. A sufficient detention time is not less than 5 minutes Bell. In a preferred embodiment, the residence time is from 30 minutes to 3 hours, for example, 2 hours.

The catalyst system used in the method of the present invention can be partially or fully supported or unsupported. Therefore, the components a) and/or b) of the catalyst system can be supported or unsupported. In the case where one of the components of the catalyst system is utilized in a supported form, it is preferable that the component b) of the catalyst system is supported. Suitable supports for use in the present invention include carbon, activated carbon, silica, zirconia, alumina, alumina-silica, silicon carbide, zeolite, zirconium oxide, magnesium oxide, zinc oxide, titanium oxide, clay, and Several combinations and so on. Preferably, the support is selected from silicon oxide, titanium oxide and activated carbon.

Those skilled in the art know that any method for generating a supported metallic catalyst can be used to generate a supported catalyst component. For example, a supported catalyst can be prepared by first dissolving the selected catalyst components in a suitable solvent, such as water, ethers, alcohols, carboxylic acids, ketones and aldehydes, preferably water Or alcohols. This mixture can then be added to the support of choice, or alternatively, the support system can be immersed in the mixture.

An impregnated support can then be retrieved using any conventional separation technique, including, for example, decantation and/or filtration. Once retrieved, the impregnated support can be dried, preferably by placing the support in a heating oven. Alternatively or additionally, a dehumidifier can be used. For the purpose of the present invention, the components a) and/or b) can be adsorbed on the support, so that the amount of the metal active components of the components a) and/or b) is based on the supported catalyst The weight of the ingredients is 0.05-50wt.%.

The method according to the invention can be carried out via a batch or continuous mode of operation. Operating in a batch mode, the raw materials, reaction medium and catalyst are typically combined in the presence of hydrogen, stirred and allowed to react for an appropriate amount of time. A sufficient contact time for the catalytic reaction to be sufficiently continued is at least 5 minutes. Following this contacting step, the reaction mixture is removed from the reaction vessel, its constituents are separated, and the product ethylene glycol is retrieved.

In a continuous mode of operation, a stream containing raw materials is continuously fed to a reaction zone, and the ethylene glycol product/effluent stream is continuously drawn. The reaction zone may include separate feed streams of raw materials and hydrogen. The feed stream of the raw material may also contain the reaction medium, any acidic species necessary for changing the pH of the reaction, and the components of the catalyst system; or alternatively, they may be separately fed into the reaction zone. One or more components of the catalyst system may be immobilized in the reaction zone, for example, as part of a catalyst bed reactor system.

Therefore, under the condition that the components a) and/or b) of the catalyst system are supported, the contacting step (i) may include passing the raw materials and the reaction medium through a column filled with (several) supported catalyst system components ( That is, a packed bed configuration). Therefore, the raw material containing at least one sugar can pass through a tubular column containing the supported catalyst system component(s). The sugars will therefore undergo a catalytic reaction in the presence of at least partially supported catalysts and hydrogen, and then the effluent stream can be removed from the column to contain ethylene glycol. In addition, or alternatively, a fixed bed configuration with a plurality of plates and/or trays can be used.

The reaction mixture removed from the reaction vessel except for the product ethylene glycol The effluent/effluent stream may also contain by-product polyols such as 1,2-propanediol and glycerol, other alcohols, aldehydes, unreacted sugars, phenolic compounds, and any acidic species used to change the pH of the reaction mixture. The solid components of the reaction mixture, especially the components of the catalyst system, can be separated by, for example, filtration, centrifugation, fluid cyclone, fractionation, extraction, evaporation, or several combinations thereof. In this way, the components of the catalyst system can be isolated so that they can be recycled and reused. Therefore, in one embodiment, the method of the present invention further includes a step of recycling one or more of the catalyst system components.

Under the condition that the raw material containing sugar is derived from biomass, the ethylene glycol prepared by the method of the present invention preferably has a ^{carbon-14 to carbon-12 ratio of at least 0.5 x 10 -13} , or in other words, at least 1:2 x 10 ^{13 is} the ratio of carbon-14 to carbon-12. The ratio of carbon-14 to carbon-12 can be appropriately measured using radiometric dating or accelerator mass spectrometry.

The present invention will now be exemplified by the following examples and with reference to the following diagrams: Figure 1: Graphical representation of the effect of the pH of the catalytic reaction according to the method of the present invention on the yield of polyols (1wt.% of treated EFB loading).

Figure 2: Graphical representation of the effect of the pH of the catalytic reaction according to the method of the present invention on the yield of polyols (10wt.% of treated EFB loading).

Figure 3: Graphical representation of the effect of ammonium metatungstate and HCl acid addition on the yield of polyols (10wt.% treated EFB loading, 700ppm HCl).

Detailed description of the preferred embodiment Preparation of raw materials

The original biomass, specifically the empty fruit cluster (oil palm biomass), is physically refined by milling with a knife mill and sorting with a sieve. The obtained untreated EFB fiber was then dried at 100°C for 12 hours.

Preparation of ethylene glycol from biomass containing sugars without chemical pretreatment

Comparative Example 1

In a pressure vessel, 50ml of deionized water, 0.05g of Raleigh's nickel and 0.05g of sodium tungstate were added to 0.5g of untreated empty fruit bunch (EFB) raw material. Dilute sulfuric acid was added until the reaction mixture formed to have a pH of 7. At ambient temperature, hydrogen is pumped into the pressure vessel with stirring (500 rpm), and before the temperature is increased to 245°C, the pressure is as high as 2 MPa for a reaction time of 2 hours. When the reaction is complete, before the sample is drawn for high-performance liquid chromatography (HPLC) analysis, the temperature is lowered to ambient temperature and the hydrogen system is evacuated through the exhaust system. The yield of polyol was then calculated and the results are presented in Table 1.

Example 1

The method of Comparative Example 1 was repeated, but the difference was that a 1 wt.% sulfuric acid solution was added until the reaction mixture was formed to have a pH of 6.

Example 2

The method of Comparative Example 1 was repeated, but the difference was that a 1 wt.% sulfuric acid solution was added until the reaction mixture was formed to have a pH of 5.

It can be seen from the results in Table 1 that when the pH is neutral, the ratio of ethylene glycol to 1,2-propanediol obtained is 2.48. Using inorganic acid to adjust to pH 6, it can be seen that the ratio of ethylene glycol to 1,2-propanediol increases to 3.30. At the same time, using inorganic acid to adjust the pH from pH 7 to pH 5, it can be seen that the ratio of ethylene glycol to 1,2-propanediol is even more greatly increased to 4.34. The yield reported in the above table is calculated based on the whole raw material, which has about 15wt.% lignin and/or ash content.

Preparation of ethylene glycol from biomass containing sugars with alkaline pretreatment

Example 3

The 1 wt.% sodium hydroxide solution was added to a container containing 10 g of empty fruit bunch (EFB) raw materials so that the weight ratio of the raw materials to the sodium hydroxide solution was 1:10. The container was then heated to 60°C and pre-treated for 12 hours before the pre-treated raw materials were separated. Following the completion of the pretreatment, the pretreatment EFB is separated by filtration before washing with water. The volume ratio of the pretreatment EFB to water during washing is 1:10. This cleaning step is repeated twice.

In separate pressure vessels, 50ml of deionized water, 0.05g of Raleigh's nickel, and 0.05g of tungstic acid were added to 0.5g of pretreatment raw material samples, together with varying amounts of hydrochloric acid (0-200ppm). The catalytic reaction was followed by the phase described in Comparative Example 1. Execute under the same conditions. The results of the yields of ethylene glycol and 1,2-propanediol in different hydrochloric acid concentrations according to this example are graphically shown in FIG. 1.

The following Table 2 is a corresponding table, which shows the amount of HCl added in this example and the pH of the resulting reaction mixture.

Example 4

The 1 wt.% sodium hydroxide solution was added to a container containing 10 g of empty fruit bunch (EFB) raw materials so that the weight ratio of the raw materials to the sodium hydroxide solution was 1:10. The container was then heated to 60°C and pre-treated for 12 hours before the pre-treated raw materials were separated.

In separate pressure vessels, 50ml of deionized water, 0.5g of Raleigh's nickel and 0.5g of tungstic acid are added to 5g of pretreated raw material samples, together with different amounts of hydrochloric acid (0-1100ppm; the corresponding pH value is between 3.0 and 7.0 ). The catalytic reaction was then performed under the same conditions as described in Comparative Example 1. The results of the yields of ethylene glycol and 1,2-propanediol in different hydrochloric acid concentrations according to this example are graphically shown in FIG. 2.

Example 5

The 1 wt.% sodium hydroxide solution was added to a container containing 10 g of empty fruit bunch (EFB) raw materials so that the weight ratio of the raw materials to the sodium hydroxide solution was 1:10. The container was then heated to 60°C and pre-treated for 12 hours before the pre-treated raw materials were separated.

In a separate pressure vessel, 40ml of deionized water, 0.5g of Raleigh’s nickel and 700ppm HCl were added to 4.4g of pretreatment raw material samples, together with different amounts of ammonium metatungstate (AMT) (0-1100ppm; the corresponding pH value was at Between 3.0 and 7.0). The catalytic reaction was then performed under the same conditions as described in Comparative Example 1. The results of the yields of ethylene glycol and 1,2-propanediol in different AMT concentrations according to this example are graphically shown in FIG. 3.

It can be seen from Figures 1 and 2 that increasing the amount of HCl in the catalytic reaction and lowering the pH to about 3 can reduce the yield of 1,2-propanediol while increasing the yield of better ethylene glycol to a certain extent. At the same time, FIG. 3 illustrates that when acidic conditions are used in the catalytic reaction, increasing the concentration of the hydrogenation catalyst (AMT) can increase the yield of ethylene glycol while also slightly reducing the yield of 1,2-propanediol.

The yields of ethylene glycol to 1,2-propanediol in FIGS. 1 to 3 also exemplify the further improvement of the pretreatment of biomass-derived raw materials using an alkaline solution before the acidic hydrogenolysis/hydrogenation according to the present invention. This particular combination of process steps has surprisingly been found to optimize the yield of ethylene glycol relative to other polyols including 1,2-propanediol.

Claims (34)

A method for preparing ethylene glycol from a raw material containing at least one sugar, comprising the following steps: i) contacting the raw material containing at least one sugar with a catalyst system in the presence of hydrogen and a reaction medium; And ii) obtaining ethylene glycol from the reaction mixture; wherein the catalyst system contains: a) tungsten, molybdenum, or a combination thereof; and b) one or more transition metals selected from groups 8, 9 and 10 of IUPAC , And several combinations thereof; wherein step i) is carried out at a pH ranging from 2.5 to 4; wherein the raw material is derived from biomass; and wherein the biomass is pretreated biomass, which is used as a raw material It has been subjected to pretreatment, wherein the pretreatment involves treating the raw or crude biomass with an alkaline solution at a temperature of from 20°C to 110°C, wherein the biomass is empty fruit bush (EFB). Such as the method of claim 1, wherein step i) is carried out at a pH between 2.75 and 3.25. Such as the method of claim 1, wherein step i) is carried out in the presence of an organic or inorganic acid. The method of claim 3, wherein the acid is an inorganic acid selected from hydrochloric acid, sulfuric acid, nitric acid, and phosphoric acid. The method of claim 4, wherein the acid is hydrochloric acid or sulfuric acid. The method of claim 3, wherein the acid is an organic acid selected from the group consisting of acetic acid, maleic acid, butyric acid, benzenesulfonic acid, terephthalic acid, benzoic acid, phthalic acid and salicylic acid. The method of claim 6, wherein the acid is benzenesulfonic acid. The method of claim 3, wherein the amount of the acid present is from 0.001 to 0.1 wt.% based on the total weight of the reaction mixture. The method of claim 3, wherein the amount of the acid present is from 10 ppm to 1000 ppm. The method according to any one of claims 1 to 9, wherein the reaction medium contains a solvent selected from water, methanol, ethanol, propanol, butanol, ethylene glycol and glycerol, or a combination thereof. The method according to any one of claims 1 to 9, wherein the reaction medium contains an aqueous solvent. The method according to any one of claims 1 to 9, wherein step i) is performed at a temperature of at least 150°C. Such as the method of claim 12, wherein step i) is performed at a temperature ranging from 200 to 300°C. Such as the method of any one of claims 1 to 9, wherein step i) is performed at a pressure of 0.1 to 15 MPa. Such as the method of claim 14, wherein step i) is performed at a pressure of 1 to 7 MPa. The method according to any one of claims 1 to 9, wherein the amount of the raw material present is 1 to 30 wt% based on the total weight of the reaction mixture. Such as the method of any one of claims 1 to 9, wherein the catalyst system is Suba) Containing tungsten, which is in elemental form or in the form of compounds selected from the following: sodium tungstate, tungsten nitride, tungsten carbide, tungsten phosphide, tungsten oxide, tungsten sulfide, tungsten chloride, tungsten hydroxide, tungsten bronze , Tungstic acid, tungstate, metatungstic acid, metatungstate, paratungstic acid, paratungstic acid, peroxytungstic acid, peroxytungstic acid, heterogeneous polymeric tungstic acid. The method of claim 17, wherein the component a) of the catalyst system contains tungsten in the form of a compound selected from sodium tungstate, tungsten carbide, tungsten bronze, ammonium metatungstate and tungstic acid. The method of claim 18, wherein the component a) of the catalyst system contains tungsten in the form of a compound selected from sodium tungstate, ammonium metatungstate and tungstic acid. The method according to any one of claims 1 to 9, wherein the component a) of the catalyst system contains molybdenum in elemental form or molybdic acid form. The method according to any one of claims 1 to 9, wherein the component b) of the catalyst system contains a metal selected from iron, cobalt, nickel, ruthenium, rhodium, palladium, iridium and platinum. The method of claim 21, wherein the component b) of the catalyst system contains a metal selected from nickel, ruthenium or platinum. The method of claim 22, wherein the component b) of the catalyst system contains nickel. The method of claim 1, wherein the temperature is from 30°C to 80°C. Such as the method of claim 1, wherein the pre-processing is performed in a time scale ranging from 30 minutes to 48 hours. Such as the method of claim 1, wherein the pretreatment is performed within a time scale of from 1 hour to 24 hours. Such as the method of claim 1, wherein the alkaline solution contains 0.1 to 30 wt.% Ammonium hydroxide, an alkali or alkaline earth metal hydroxide. The method of claim 1, wherein the alkaline solution is an aqueous sodium hydroxide solution. The method of claim 1, wherein the ethylene glycol product obtained has a ratio of carbon-14 to carbon-12 of ^{at least 0.5 x 10 -13.} Such as the method of any one of claims 1 to 9, wherein the catalyst system containing components a) and b) is unsupported. The method according to any one of claims 1 to 9, wherein component a) and/or component b) of the catalyst system is supported by a carrier material. The method of claim 31, wherein the support material is selected from carbon, activated carbon, silica, zirconia, alumina, alumina-silica, silicon carbide, zeolite, zirconium oxide, magnesium oxide, zinc oxide, oxide Any of several combinations of titanium, clay and others. The method of claim 32, wherein the carrier material is selected from silicon oxide, titanium oxide, and activated carbon. Such as the method of claim 31, wherein the amount of the metal active component of component a) and/or component b) is 0.05-50wt.% based on the total weight of the supported catalyst component.

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