Process for the preparation of ethylene glycol

Abstract

The present application relates to the field of ethylene glycol preparation, and discloses a method for preparing ethylene glycol. The method comprises the following steps: in the presence of water, a polyhydroxy compound and hydrogen are reacted with a catalyst; the catalyst comprises a metal / COFs material and a tungsten-containing compound; wherein the COFs material in the metal / COFs material is selected from at least one of nitrogen-containing organic framework materials; and the metal in the metal / COFs material is selected from at least one of noble metal elements and nickel elements. The method for preparing ethylene glycol has high ethylene glycol selectivity and yield; and the catalyst used in the method has good cycle stability.

Description

Technical Field

[0001] This invention relates to the field of ethylene glycol preparation, and more specifically to a method for preparing ethylene glycol. Background Technology

[0002] Ethylene glycol is an important basic chemical raw material with wide applications and a large market size. However, current ethylene glycol production processes are almost entirely based on fossil fuels such as oil, natural gas, and coal, resulting in drawbacks such as fossil fuel dependence, high energy consumption, and high carbon dioxide emissions. Producing bio-based ethylene glycol from biomass resources can circumvent these drawbacks while offering advantages such as: 1. good atom economy; 2. readily available raw materials; 3. renewable resources; and 4. low carbon dioxide emissions. Currently, polyhydroxyl biomass catalytic ethylene glycol production technology is not yet mature. Therefore, developing new catalysts and processes can advance the industrialization of this technology, thereby generating significant environmental and economic benefits.

[0003] CN105523890A discloses a method for producing diols from sugar. Diols are prepared directly from sugar through hydrolysis and hydrogenation in the presence of tungstate and alloy hydrogenation catalysts. CN102190562A, CN101735014A, and CN102731258A mainly utilize supported catalysts containing metal active components (such as Ni, Fe, Co, Ru, etc.) and tungsten-containing compounds to convert polyhydroxy compounds into ethylene glycol.

[0004] The catalysts and their preparation methods used in the above reactions have the following main drawbacks: poor stability due to the loss of metal active sites; high metal consumption and high cost; and demanding catalyst synthesis conditions, which basically require high temperature synthesis. Summary of the Invention

[0005] The purpose of this invention is to overcome the problems existing in the prior art and provide a method for preparing ethylene glycol. The method of this invention produces ethylene glycol with high selectivity and yield; moreover, the catalyst used in this method has good cycle stability.

[0006] To achieve the above objectives, the present invention provides a method for preparing ethylene glycol, the method comprising: reacting a polyhydroxy compound and hydrogen with a catalyst in the presence of water; wherein the catalyst comprises a metal / COFs material and a tungsten-containing compound;

[0007] Wherein, the COFs material in the metal / COFs material is selected from at least one of nitrogen-containing organic framework materials;

[0008] The metal in the metal / COFs material is selected from at least one of noble metal elements and nickel.

[0009] The beneficial effects of the present invention through the above technical solution include:

[0010] The method provided by this invention prepares ethylene glycol using polyhydroxy compounds as reactants. It employs a catalytic system composed of specific types of metal / COFs materials and tungsten-containing compounds to achieve highly efficient conversion of polyhydroxy compounds, exhibiting high product selectivity and yield. Furthermore, the metal / COFs material in the catalyst system described in this invention maintains good stability during the reaction. This is presumably due to the covalent bonds between the metal in the metal / COFs material and the nitrogen in the nitrogen-containing organic framework material, enhancing the metal's binding force, effectively reducing metal loss during the reaction, stabilizing the metal active sites, and thus increasing cycle stability. Additionally, the metal content in the metal / COFs material described in this invention is low, reducing catalyst costs.

[0011] The method provided by this invention is a one-step reaction, which is simple and has a very broad prospect for industrial application. Attached Figure Description

[0012] Figure 1 Here is a SEM image of the metal / COFs material prepared in Example 1;

[0013] Figure 2 This is a STEM image of the metal / COFs material prepared in Example 1;

[0014] Figure 3 This is a powder X-ray diffraction pattern of the metal / COFs material prepared in Example 1. Detailed Implementation

[0015] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0016] In this invention, the terms "first" and "second" do not limit the substances and operations, but are only used to distinguish the substances introduced in different steps and the operations performed in different stages.

[0017] The present invention provides a method for preparing ethylene glycol, the method comprising: reacting a polyhydroxy compound and hydrogen with a catalyst in the presence of water; the catalyst comprising a metal / COFs material and a tungsten-containing compound;

[0018] Wherein, the COFs material in the metal / COFs material is selected from at least one of nitrogen-containing organic framework materials;

[0019] The metal in the metal / COFs material is selected from at least one of noble metal elements and nickel.

[0020] The catalytic system used in the method described in this invention is employed to produce ethylene glycol from polyhydroxy compounds, exhibiting high selectivity and yield. Furthermore, the catalyst system described in this invention maintains good stability during the reaction process, presumably because the metal in the metal / COFs material is covalently bonded to the nitrogen in the nitrogen-containing organic framework material. This enhanced metal binding force effectively reduces metal loss during the reaction, stabilizes the metal active sites, and thus increases cycle stability.

[0021] According to the present invention, preferably, based on the total mass of the metal / COFs material, the mass fraction of the metal element is 1-20%, specifically 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, and any two of these values ​​forming a range, preferably 3-10%. This preferred embodiment is beneficial for the formation of the target product in the reaction.

[0022] In this invention, the metal content in the metal / COFs material is determined by plasma emission spectroscopy.

[0023] The present invention has a wide range of choices for the precious metal element. Preferably, the precious metal element is selected from at least one of ruthenium, platinum, palladium and rhodium, and more preferably ruthenium.

[0024] According to the present invention, preferably, the specific surface area of ​​the nitrogen-containing organic framework material is 200-2000 m². 2 / g, preferably 500-1500m 2 / g.

[0025] According to the present invention, preferably, the pore volume of the nitrogen-containing organic framework material is 0.5-2 cm³. 3 / g, preferably 0.7-1.5cm 3 / g.

[0026] Using nitrogen-containing organic framework materials with the above characteristics is beneficial to improving reaction efficiency, and using nitrogen-containing organic framework materials is beneficial to improving the thermal stability of catalysts.

[0027] The present invention allows for a wide range of choices of nitrogen-containing organic framework materials, and any materials whose specific surface area and pore volume meet the above conditions can be used.

[0028] Preferably, the first organic ligand in the nitrogen-containing organic framework is an organic compound containing two or more amino groups, and is preferably selected from at least one of p-phenylenediamine, p-diaminoazobenzene, and 4,4-diamino-2,2-bipyridine.

[0029] Preferably, the second organic ligand in the nitrogen-containing organic framework is trialdehyde phloroglucinol.

[0030] The present invention does not have any particular limitation on the source of the nitrogen-containing organic framework material, which can be prepared by conventional methods in the art.

[0031] According to the present invention, preferably, the molar ratio of the metal / COFs material (calculated as metal element) to the tungsten-containing compound (calculated as tungsten element) is 1-10, specifically 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, and any two of these values ​​within a range, preferably 2-7. This preferred embodiment is beneficial for the formation of the target product, ethylene glycol.

[0032] The tungsten-containing compound described in this invention can be selected from a wide range of types, as long as it contains tungsten. Preferably, the tungsten-containing compound is selected from at least one of tungstic acid, ammonium metatungstate, and tungsten trioxide.

[0033] To more clearly illustrate the preparation of the catalyst described in this invention, a specific preparation method is provided, but this invention is not limited thereto.

[0034] According to the present invention, preferably, the method for preparing the catalyst includes:

[0035] (1) In the presence of a solvent, a metal-containing compound is subjected to a coordination reaction with a nitrogen-containing organic framework material, and then dried to obtain a metal / COFs material;

[0036] (2) Mix the metal / COFs material with a tungsten-containing compound.

[0037] According to the present invention, preferably, the conditions for the coordination reaction in step (1) include: a temperature of 20-150°C, preferably 60-150°C; and a time of 1-48h, preferably 4-20h.

[0038] The present invention does not have a particular limitation on the amount of the metal-containing compound and the nitrogen-containing organic framework material used, as long as the metal / COFs material with the above-mentioned metal mass content is 1-20%.

[0039] Preferably, the mass ratio of the metal-containing compound to the nitrogen-containing organic framework material is 0.1-18:1, more preferably 0.25-8:1.

[0040] The present invention allows for a wide range of metal-containing compounds, including various metal-containing compounds commonly found in the art. Preferably, the metal-containing compound is selected from at least one of nitrates, acetates, chlorides, and sulfates.

[0041] This invention allows for a wide range of choices regarding the types of nitrogen-containing organic framework materials, as long as the specific surface area and pore volume meet the above-mentioned conditions. This invention does not particularly limit the source of the nitrogen-containing organic framework materials; they can be prepared using conventional methods in the art.

[0042] The present invention allows for a wide range of solvent choices, including conventional choices in the field, such as methanol, N,N-dimethylformamide, etc.

[0043] The present invention does not have a particular limitation on the amount of solvent used, as long as the other components are mixed evenly.

[0044] The present invention does not have any particular limitation on the drying process described in step (1), and can be carried out with reference to conventional methods in the art.

[0045] Preferably, the method for preparing the catalyst further includes washing the product of the coordination reaction in step (1) before drying.

[0046] The present invention does not have any particular limitation on the washing method, and conventional methods in the art can be used.

[0047] The present invention does not have any particular limitation on the mixing process described in step (2), but the mixing of the metal / COFs material and the tungsten-containing compound is considered to be uniform.

[0048] This invention employs a catalytic system composed of specific types of metals / COFs and tungsten-containing compounds. This catalytic system is used to produce ethylene glycol from polyhydroxy compounds, exhibiting high selectivity for ethylene glycol and a simple reaction process.

[0049] The present invention has a wide range of choices for the types of polyhydroxy compounds used as reaction substrates. Preferably, the polyhydroxy compounds are selected from at least one of starch, cellulose, glucose, fructose, sucrose and sorbitol.

[0050] According to the present invention, preferably, the reaction conditions include: a reaction temperature of 150-300℃, more preferably 200-245℃; and a reaction pressure of 0.5-10MPa, more preferably 1-6MPa.

[0051] According to the present invention, preferably, the mass ratio of water to polyhydroxy compound is 4-1000:1, more preferably 10-100:1.

[0052] According to the present invention, preferably, the mass ratio of the polyhydroxy compound to the catalyst is 10-0.1, more preferably 5-0.5.

[0053] The present invention will be described in detail below through embodiments.

[0054] In the following preparation examples, the nitrogen-containing organic framework material used was a 2D COFs prepared according to the literature (Qiu J, Guan P, Zhao Y, et al. Syntheses of two-and three-dimensional covalent organic frameworks in deepeutectic solvents[J]. Green Chemistry, 2020, 22(21):7537-7542), denoted as TpPa-Gly, with a specific surface area of ​​747 m². 2 / g, pore volume 1.2cm³ 3 / g;

[0055] The valence state of the metal in the metal / COF material was characterized by X-ray photoelectron spectroscopy.

[0056] In the following examples, the reaction products (e.g., ethylene glycol, propylene glycol, butanediol) were qualitatively analyzed by gas chromatography-mass spectrometry (GC-MS), and the yields of the products (e.g., ethylene glycol, propylene glycol, butanediol) and the conversion rates of the polyhydroxy compounds of the reaction substrates were analyzed by gas chromatography (GC). The GC-MS system was an Agilent 7890A from Agilent Technologies, USA, with an HP-5 nonpolar capillary column (30m, 0.53mm). The gas chromatograph was an Agilent 7890B, with a flame ionization detector (FID) and an SE-54 capillary column (30m, 0.53mm).

[0057] The formula for calculating the conversion rate of polyhydroxy compounds is:

[0058] Conversion rate of polyhydroxy compounds = (molar amount of polyhydroxy compounds participating in the reaction) / (molar amount of polyhydroxy compounds as initial reaction substrates) × 100%;

[0059] The formula for calculating the selectivity of the product ethylene glycol is:

[0060] The selectivity of the product ethylene glycol = (the number of carbon atoms corresponding to the molar amount of ethylene glycol produced in the reaction) / (the number of carbon atoms corresponding to the molar amount of the initial reaction substrate polyhydroxy compound) × 100%.

[0061] The preparation examples described in this invention are used to illustrate the preparation of catalysts.

[0062] Preparation Example 1

[0063] 2g of nitrogen-containing organic framework material and 2g of nickel chloride were added to 50mL of DMF solution and refluxed at 140℃ for 8 hours. After cooling, the mixture was washed sequentially with DMF and water, and then dried to obtain Ni / COFs material, the composition of which is shown in Table 1. The Ni / COFs material was mixed with tungstic acid, wherein the molar ratio of Ni / COFs material (based on nickel) to tungstic acid (based on tungsten) was 5:1.

[0064] An exemplary SEM image of the Ni / COFs material prepared in Example 1 is provided, as follows: Figure 1 As shown. From Figure 1 It can be seen that the material exhibits a porous structure at the nanoscale and microscale, and the obtained Ni / COFs material is a porous structure.

[0065] The STEM spectrum of the Ni / COFs material prepared in Example 1 is shown as an example. Figure 2 As shown. From Figure 2 It can be seen that Ni is uniformly distributed in Ni / COFs materials.

[0066] The XRD pattern of the Ni / COFs material prepared in Example 1 is shown as an example. Figure 3 As shown. From Figure 3 It can be seen that the catalyst exhibits characteristic peaks consistent with those of the COF material, indicating that the support is a nitrogen-containing organic framework material.

[0067] Preparation Example 2

[0068] 2g of nitrogen-containing organic framework material and 2g of nickel acetate were added to 50mL of DMF solution and refluxed at 140℃ for 8 hours. After cooling, the mixture was washed sequentially with DMF and water, and then dried to obtain Ni / COFs material, the composition of which is shown in Table 1. The Ni / COFs were mixed with tungstic acid, wherein the molar ratio of Ni / COFs material (based on nickel) to tungstic acid (based on tungsten) was 3:1.

[0069] Preparation Example 3

[0070] 2g of nitrogen-containing organic framework material and 1g of nickel nitrate were added to 50mL of DMF solution and refluxed at 140℃ for 6 hours. After cooling, the mixture was washed sequentially with DMF and water, and then dried to obtain Ni / COFs material, the composition of which is shown in Table 1. The Ni / COFs were mixed with tungstic acid, wherein the molar ratio of Ni / COFs material (based on nickel) to tungsten-containing compound (based on tungsten) was 4:1.

[0071] Preparation Example 4

[0072] 2g of nitrogen-containing organic framework material and 2g of nickel sulfate were added to 50mL of DMF solution and refluxed at 140℃ for 6 hours. After cooling, the mixture was washed sequentially with DMF and water, and then dried to obtain Ni / COFs material, the composition of which is shown in Table 1. The Ni / COFs material was mixed with tungstic acid, wherein the molar ratio of Ni / COFs material (based on nickel) to tungsten-containing compound (based on tungsten) was 2:1.

[0073] Preparation Example 5

[0074] 2g of nitrogen-containing organic framework material and 2g of nickel chloride were added to 50mL of methanol solution, refluxed at 70℃ for 4 hours, cooled, washed successively with methanol and water, and then dried to obtain Ni / COFs material, the composition of which is shown in Table 1. The Ni / COFs material was mixed with tungstic acid, wherein the molar ratio of Ni / COFs material (based on nickel content) to tungsten-containing compound (based on tungsten content) was 5:1.

[0075] Preparation Example 6

[0076] 2g of nitrogen-containing organic framework material and 5g of nickel chloride were added to 50mL of DMF solution and refluxed at 140℃ for 6 hours. After cooling, the mixture was washed sequentially with DMF and water, and then dried to obtain Ni / COFs material, the composition of which is shown in Table 1. The Ni / COFs material was mixed with tungstic acid, wherein the molar ratio of Ni / COFs material (based on nickel content) to tungsten-containing compound (based on tungsten content) was 3:1.

[0077] Preparation Example 7

[0078] 5g of nitrogen-containing organic framework material and 5g of nickel chloride were added to 50mL of DMF solution and refluxed at 140℃ for 8 hours. After cooling, the mixture was washed sequentially with DMF and water, and then dried to obtain Ni / COFs material, the composition of which is shown in Table 1. The Ni / COFs material was mixed with tungstic acid, wherein the molar ratio of Ni / COFs material (based on nickel content) to tungsten-containing compound (based on tungsten content) was 6:1.

[0079] Preparation Example 8

[0080] The preparation method of Example 1 was followed, except that 0.2 g of ruthenium chloride was used instead of nickel chloride. The Ru / COFs material was obtained, and its composition is shown in Table 1.

[0081] Preparation Example 9

[0082] The preparation method was followed as in Example 1, except that the amount of nickel chloride was adjusted to 200 mg.

[0083] Comparative Preparation Example 1

[0084] 2g of nitrogen-containing organic framework material and 2g of cobalt chloride were added to 50mL of DMF solution and refluxed at 140℃ for 8 hours. After cooling, the mixture was washed sequentially with DMF and water, and then dried to obtain Ni / COFs material, the composition of which is shown in Table 1. The Ni / COFs material was mixed with tungstic acid, wherein the molar ratio of Ni / COFs material (based on nickel) to tungstic acid (based on tungsten) was 5:1.

[0085] Comparative Preparation Example 2

[0086] The preparation method was followed as in Example 1, except that activated carbon was used instead of COF material. Specifically, 2g of activated carbon and 200mg of nickel chloride were added to 50mL of aqueous solution, stirred at 60°C for 1 hour, cooled, dried, and then reduced at 450°C for 2 hours under a hydrogen atmosphere to obtain 5wt% Ni / AC. The Ni / AC material was then mixed with tungstic acid, wherein the molar ratio of Ni / AC material (based on nickel) to tungstic acid (based on tungsten) was 5:1.

[0087] Table 1

[0088]

[0089] Example 1

[0090] The catalytic conversion of glucose to ethylene glycol was carried out in a closed reactor. 0.12 g of the catalyst from Preparation Example 1, 0.25 g of glucose, and 25 mL of deionized water were added to a stirred high-pressure reactor. Hydrogen gas was purged three times, and then the reactor was purged with hydrogen to 4 MPa and sealed. The temperature was raised to 240 °C using a programmed heating mantle, and the reaction was carried out at 240 °C for 2 h. Gas chromatography was used to quantitatively analyze the products in the reaction solution, and liquid chromatography was used to quantitatively analyze the raw materials in the reaction solution. The reaction results are shown in Table 2.

[0091] Examples 2-9, Comparative Examples 1-2

[0092] The reaction was carried out according to the method of Example 1, except that the catalysts used in Preparation Examples 2-9 and Comparative Preparation Examples 1-2 were employed. The reaction results are shown in Table 2.

[0093] Example 10

[0094] The catalytic conversion of glucose to ethylene glycol was carried out in a closed reactor. 0.2 g of the catalyst from Preparation Example 1, 0.25 g of glucose, and 25 mL of deionized water were added to a stirred high-pressure reactor. Hydrogen gas was purged three times, and then the reactor was purged with hydrogen to 4 MPa and sealed. The temperature was raised to 230 °C using a programmed heating mantle, and the reaction was carried out at 230 °C for 2 h. Gas chromatography was used to quantitatively analyze the products in the reaction solution, and liquid chromatography was used to quantitatively analyze the raw materials in the reaction solution. The reaction results are shown in Table 2.

[0095] Table 2

[0096] Example number Glucose conversion (%) Ethylene glycol selectivity (%) Ethylene glycol yield (%) Example 1 >99 31.2 31.2 Example 2 >99 30.3 30.3 Example 3 >99 33.6 33.6 Example 4 >99 31.5 31.5 Example 5 >99 29.8 29.8 Example 6 >99 35.9 35.9 Example 7 >99 30.5 30.5 Example 8 >99 20.4 20.4 Example 9 >99 18.5 18.5 Example 10 >99 28.6 28.6 Comparative Example 1 >99 5.6 5.6 Comparative Example 2 >99 15.3 15.3

[0097] As can be seen from the results in Table 2, the method described in this invention produces ethylene glycol with significantly higher selectivity and yield. This demonstrates that the catalyst provided by this invention possesses excellent catalytic performance.

[0098] Example 11

[0099] The reaction was carried out according to the method of Example 1. After the reaction, the Ni / COFs material in the catalyst was washed sequentially with ethanol and water, dried, and then recycled. During recycling, the dried Ni / COFs material was mixed with tungstic acid, wherein the molar ratio of Ni / COFs material (based on nickel) to tungstic acid (based on tungsten) was 5:1. The results are shown in Table 3.

[0100] Table 3

[0101]

[0102] As can be seen from Table 3, the metal / COFs material in the catalyst system described in this invention can maintain good stability during the reaction process.

[0103] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for preparing ethylene glycol, characterized in that, The method includes: contacting a polyhydroxy compound and hydrogen with a catalyst in the presence of water; the catalyst includes a metal / COFs material and a tungsten-containing compound; Wherein, the COFs material in the metal / COFs material is selected from at least one of nitrogen-containing organic framework materials; The metal in the metal / COFs material is selected from at least one of noble metal elements and nickel.

2. The method according to claim 1, wherein, Based on the total mass of the metal / COFs material, the mass fraction of the metal element is 1-20%, preferably 3-10%; Preferably, the precious metal element is selected from at least one of ruthenium, platinum, palladium and rhodium, and is preferably ruthenium.

3. The method according to claim 1, wherein, The specific surface area of ​​the nitrogen-containing organic framework material is 200-2000 m². 2 / g, preferably 500-1500m 2 / g; Preferably, the pore volume of the nitrogen-containing organic framework material is 0.5-2 cm³. 3 / g, preferably 0.7-1.5cm 3 / g; Preferably, the first organic ligand in the nitrogen-containing organic framework is an organic compound containing two or more amino groups, and is preferably selected from at least one of p-phenylenediamine, p-diaminoazobenzene, and 4,4-diamino-2,2-bipyridine; Preferably, the second organic ligand in the nitrogen-containing organic framework is trialdehyde phloroglucinol.

4. The method according to any one of claims 1-3, wherein, The molar ratio of the metal / COFs material (calculated as metal element) to the tungsten-containing compound (calculated as tungsten element) is 1-10, preferably 2-7.

5. The method according to any one of claims 1-4, wherein, The tungsten-containing compound is selected from at least one of tungstic acid, ammonium metatungstate, and tungsten trioxide.

6. The method according to any one of claims 1-5, wherein, The method for preparing the catalyst includes: (1) In the presence of a solvent, a metal-containing compound is subjected to a coordination reaction with a nitrogen-containing organic framework material, and then dried to obtain a metal / COFs material; (2) Mix the metal / COFs material with a tungsten-containing compound.

7. The method according to claim 6, wherein, The conditions for the coordination reaction in step (1) include: a temperature of 20-150℃, preferably 60-150℃; and a time of 1-48h, preferably 4-20h. Preferably, the mass ratio of the metal-containing compound to the nitrogen-containing organic framework material is 0.1-18:1, more preferably 0.25-8:

1.

8. The method according to any one of claims 1-7, wherein, The polyhydroxy compound is selected from at least one of starch, cellulose, hemicellulose, glucose, fructose, fructan, sucrose, and sorbitol.

9. The method according to any one of claims 1-8, wherein, The reaction conditions include: a reaction temperature of 150-300℃, preferably 200-245℃; and a reaction pressure of 0.5-10MPa, preferably 1-6MPa.

10. The method according to any one of claims 1-9, wherein, The mass ratio of the polyhydroxy compound to the catalyst is 10-0.1, preferably 5-0.5; more preferably, the mass ratio of water to the polyhydroxy compound is 4-1000:1, preferably 10-100:1.

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