A method for directly preparing 5-hydroxymethylfurfural from glucose by using a eutectic solvent

Abstract

The application discloses a method for directly preparing 5-hydroxymethylfurfural from glucose by using a deep eutectic solvent, which comprises the following steps: S1, synthesizing a deep eutectic solvent; S2, mixing glucose and the deep eutectic solvent sufficiently and sealing, heating and continuously stirring the mixed solution to carry out reaction; when the reaction is finished, rapidly cooling the reactor, and extracting 5-hydroxymethylfurfural in the reaction product by using a solvent; S3, recycling and utilizing the deep eutectic solvent in the reaction product after the 5-hydroxymethylfurfural is extracted. The deep eutectic solvent (DES) of the application retains high catalytic activity of organic acid and metal ions, realizes proportion regulation of Lewis acid and acid in the organic acid DES system, is simple to prepare and good in stability; the DES can provide a reaction environment required by sugar conversion as a solvent and catalyze sugar conversion into HMF as a catalyst, so that the yield of HMF is remarkably improved; and the product HMF can be separated by organic solvent extraction, so that the DES can be recycled.

Description

Technical Field

[0001] This invention relates to the field of biomass conversion technology, and in particular to a method for directly producing 5-hydroxymethylfurfural from glucose using a eutectic solvent. Background Technology

[0002] Biomass conversion provides the chemical industry with sustainable chemical derivatives and important intermediates. 5-Hydroxymethylfurfural (HMF) is a versatile bio-based platform compound that can be converted into a variety of high-value-added products, including long-chain alkanes, furan-2,5-dicarboxylic acids, and 2,5-dicarbonylfurans. Acid-catalyzed dehydration of fructose to high-methane furan (HMF) yields relatively high HMF production and is the main route for HMF production. However, fructose is economically expensive. Compared to fructose, glucose is more abundant, and using glucose as a raw material to convert to HMF can effectively reduce the economic cost of HMF production. However, the six-carbon cyclopyran structure of glucose is more stable than the five-carbon furan structure of fructose, making it difficult to convert to five-carbon ring HMF through direct dehydration. Therefore, the conversion of glucose to HMF is more challenging. Furthermore, the harsh reaction conditions significantly reduce the yield and selectivity of the HMF product. Summary of the Invention

[0003] The purpose of this invention is to solve the problem of difficulty in converting glucose into 5-hydroxymethylfurfural (HMF) in the prior art, and to provide a method for directly producing 5-hydroxymethylfurfural from glucose using a eutectic solvent.

[0004] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: a method for directly preparing 5-hydroxymethylfurfural from glucose using a eutectic solvent, comprising the following steps:

[0005] S1, Synthesizing eutectic solvents;

[0006] S2. Mix glucose and eutectic solvent thoroughly and seal. Heat the mixture and stir continuously to carry out the reaction. When the reaction is complete, cool rapidly and extract 5-hydroxymethylfurfural from the reaction product using a solvent.

[0007] S3. The eutectic solvent in the reaction product after extraction of 5-hydroxymethylfurfural is recovered and recycled.

[0008] Preferably, the eutectic solvent comprises hydrogen bond acceptors, Acidic hydrogen bond donor, viscosity-reducing hydrogen bond donor, and Lewis acidic component; the hydrogen bond acceptor is choline chloride; the... The acidic hydrogen bond donor is maleic acid; the viscosity-reducing hydrogen bond donor is one or more of ethylene glycol, 1,3-propanediol, 1,2-propanediol, 1,4-butanediol, and 1,3-butanediol; the Lewis acidic component is one or more of chromium trichloride, stannous chloride, and stannous tetrachloride.

[0009] Preferably, in the eutectic solvent, the hydrogen bond donor, The molar ratio of acidic hydrogen bond donors to viscosity-reducing hydrogen bond donors is 1:1:1 to 5:1:1; The molar ratio of the acidic hydrogen bond donor to the Lewis acidic component is 10:1 to 50:1.

[0010] Preferably, the hydrogen bond donor, The molar ratio of acidic hydrogen bond donor to viscosity-reducing hydrogen bond donor is 3:1:1; The molar ratio of the acidic hydrogen bond donor to the Lewis acidic component is 10:1.

[0011] Preferably, in step S1, a eutectic solvent is synthesized by heating at a temperature of 60–150°C for 10–120 minutes to obtain the eutectic solvent.

[0012] Preferably, in S2, the temperature of the mixture reaction of glucose and eutectic solvent is 110℃~150℃, the reaction time is 10 minutes~60 minutes, and the reaction pressure is ≤2 atmospheres.

[0013] Further preferably, the reaction temperature is 140°C and the reaction time is 30 minutes.

[0014] Further preferably, in step S2, 5% molar glucose and a eutectic solvent are added and mixed for reaction; ethyl acetate is used to extract 5-hydroxymethylfurfural from the reaction product.

[0015] In a further preferred embodiment, in step S3, the extraction solvent is removed by evaporation, and the eutectic solvent is recovered and recycled.

[0016] The beneficial effects of this invention are as follows:

[0017] (I) This invention utilizes Lewis acid to catalyze the isomerization of glucose to produce a fructose intermediate, and then... Acid-catalyzed dehydration of fructose intermediates yields HMF; in the eutectic solvent (DES) of this invention, choline chloride is the hydroxyl-activating component of the sugar, organic alcohol is the viscosity-reducing component, and organic acid components have… Acidity: Metal chlorides possess Lewis acidity. This invention, by adjusting the ratio of these four components, can alter the catalytic effect of DES on the conversion of sugars to HMF, thereby improving the yield and selectivity of HMF. Therefore, the DES proposed in this invention retains the high catalytic activity of both organic acids and metal ions, and achieves Lewis acid and metal ion catalytic activity in the organic acid DES system. The acid ratio can be controlled, and it has the advantages of simple preparation and good stability.

[0018] (ii) In this invention, the conversion of sugar to HMF is a homogeneous acid-catalyzed reaction. DES can be used as a solvent to provide the reaction environment required for sugar conversion, and it can also be used as a catalyst to catalyze the conversion of sugar to HMF, which significantly improves the yield of HMF. Furthermore, the product HMF can be separated by organic solvent extraction, and DES can be recovered by evaporation to remove the organic solvent, thus realizing the recycling of DES.

[0019] (III) The reaction system involved in this invention does not require the addition of water, which can suppress the byproducts such as levulinic acid and formic acid produced by the rehydration reaction during the reaction process, improve the yield of HMF product, and reduce the generation of subsequent wastewater.

[0020] (iv) The process of this invention is simple, the raw materials of DES are green and environmentally friendly, the reaction conditions are mild, and the amount of waste emissions is small, which is conducive to the industrial application of biomass sugar to prepare HMF. Attached Figure Description

[0021] Figure 1 Photographs of the product separation and DES regeneration process achieved by extracting HMF with ethyl acetate during a single-cycle experiment in a eutectic solvent system;

[0022] Figure 2 Photographs of the eutectic solvent after the first to sixth cycles of glucose reaction in the eutectic solvent system; Detailed Implementation

[0023] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0024] Example 1: Preparation of Eutectic Solvent

[0025] A eutectic solvent was prepared using a heating method. First, 4.18 g of choline chloride (ChCl), 0.62 g of ethylene glycol (EG), and 1.16 g of maleic acid (maleic acid, MalA) were added to a reactor (molar ratio of the three components = 3:1:1). Then, SnCl2 was added, resulting in a choline chloride:ethylene glycol:maleic acid:stannous chloride ratio of 3:1:1:0.1, forming a solid mixture at room temperature. The mixture was heated in a constant-temperature oil bath at 140°C using a magnetic stirrer, with magnetic stirring maintained at 300 rpm for 30 min to ensure thorough mixing of the components. After the reaction, the raw material changed from a solid mixture to a homogeneous, stable, transparent liquid, labeled as: ChCl-EG-MalA+SnCl2.

[0026] Example 2: Direct preparation of 5-hydroxymethylfurfural from glucose using a eutectic solvent

[0027] In the eutectic solvent ChCl-EG-MalA+SnCl2 prepared in Example 1, 0.09 g of glucose was added, and the reaction was carried out at 140 °C for 30 minutes. After heating was stopped, the liquid was cooled to 25 °C and extracted 5 times with ethyl acetate each time, with 5 mL of ethyl acetate used each time. The upper phase solution and the lower phase DES were separated. The DES was regenerated by heating.

[0028] The glucose conversion rate and HMF yield in the upper phase extract were analyzed by high performance liquid chromatography (HPLC). The Prevail@ES column was used at 30°C, with a 1.0 mL / min acetonitrile-water mixture (acetonitrile:water = 80:20, v / v) as the mobile phase. An Eult 119ELSD 2000ES detector was used at 95°C with 3 mL / min of dry air. The HMF content was determined using an AluTeV-UV-1000 detector (La = 285 nm) and an Authima™ C18 column at 35°C with a 1.0 mL / min acetonitrile-water mixture (acetonitrile:water = 10:90, v / v). Specific evaluation methods and index calculation methods are shown below:

[0029] The main performance evaluation indicators for ternary eutectic solvents include: glucose conversion rate (X). Glu HMF yield (Y) HMF HMF selectivity (S) HMF ) and HMF production yield (R HMF The following formulas are used to calculate the values ​​of each:

[0030]

[0031]

[0032]

[0033]

[0034] In the formula, [Glu] and [HMF] are the mass concentrations of unreacted glucose and HMF, respectively, and [Glu]0 is the initial concentration of glucose. HMF and n ChCl The values ​​represent the molar amounts of HMF and ChCl, respectively, and t represents the reaction time. The concentration of each product was analyzed using the external standard method.

[0035] The results showed that the Lewis acid + formed in the ratio of choline chloride: ethylene glycol: maleic acid: stannous chloride = 3:1:1:0.1 In the acid-bifunctional DES, the glucose conversion rate was 99.9% and the HMF yield was 59.2% after reacting at 140℃ for 30 minutes. The experimental procedure is attached. Figure 1 As shown.

[0036] Example 3

[0037] This embodiment prepares Lewis acid+ composed of choline chloride, ethylene glycol, maleic acid, and stannous chloride. The acid bifunctional DES was prepared using the same method as the eutectic solvent synthesis method in Example 1, except that in this example, the ratio of choline chloride:ethylene glycol:maleic acid:stannous chloride was 3:1:1:0.05. 5-Hydroxymethylfurfural was prepared according to the method in Example 2, and the glucose conversion rate and HMF yield were tested. The reaction was carried out at 140°C for 30 minutes, resulting in a glucose conversion rate of 99.9% and an HMF yield of 45.4%.

[0038] Example 4

[0039] This embodiment prepares Lewis acid+ composed of choline chloride, ethylene glycol, maleic acid, and stannous chloride. The acid-bifunctional DES was prepared using the same method as the eutectic solvent synthesis method in Example 1, except that in this example, the ratio of choline chloride:ethylene glycol:maleic acid:stannous chloride was 3:1:2:0.04. 5-Hydroxymethylfurfural was prepared according to the method in Example 2, and the glucose conversion rate and HMF yield were tested. The reaction was carried out at 140°C for 30 minutes, resulting in a glucose conversion rate of 99.9% and an HMF yield of 35.9%.

[0040] Example 5

[0041] This embodiment prepares Lewis acid+ composed of choline chloride, ethylene glycol, maleic acid, and stannous chloride. The acid-bifunctional DES was prepared using the same method as the eutectic solvent synthesis method in Example 1, except that in this example, the ratio of choline chloride:ethylene glycol:maleic acid:stannous chloride was 3:1:4:0.2. 5-Hydroxymethylfurfural was prepared according to the method in Example 2, and the glucose conversion rate and HMF yield were tested. The reaction was carried out at 140°C for 30 minutes, resulting in a glucose conversion rate of 99.9% and an HMF yield of 38.7%.

[0042] Example 6

[0043] This embodiment prepares Lewis acid+ composed of choline chloride, ethylene glycol, maleic acid, and stannous chloride. The acid-bifunctional DES was prepared using the same method as the eutectic solvent synthesis method in Example 1, except that in this example, the ratio of choline chloride:ethylene glycol:maleic acid:stannous chloride was 3:1:2:0.1. 5-Hydroxymethylfurfural (HMF) was prepared according to the method in Example 2, and the glucose conversion rate and HMF yield were tested. The reaction was carried out at 140°C for 30 minutes, resulting in a glucose conversion rate of 99.9% and an HMF yield of 46.5%.

[0044] Example 7

[0045] This embodiment prepares Lewis acid+ composed of choline chloride, ethylene glycol, maleic acid, and stannous chloride. The acid bifunctional DES was prepared using the same method as the eutectic solvent synthesis method in Example 1, except that in this example, the ratio of choline chloride:ethylene glycol:maleic acid:stannous chloride was 3:1:0.5:0.05. 5-Hydroxymethylfurfural (HMF) was prepared according to the method in Example 2, and the glucose conversion rate and HMF yield were tested. The reaction was carried out at 140°C for 30 minutes, resulting in a glucose conversion rate of 99.9% and an HMF yield of 49.7%.

[0046] Example 8

[0047] This embodiment prepares Lewis acid+ composed of choline chloride, ethylene glycol, maleic acid, and stannous chloride. The acid bifunctional DES was prepared using the same method as the eutectic solvent synthesis method in Example 1, except that in this example, the ratio of choline chloride:ethylene glycol:maleic acid:stannous chloride was 3:1:0.25:0.025. 5-Hydroxymethylfurfural (HMF) was prepared according to the method in Example 2, and the glucose conversion rate and HMF yield were tested. The reaction was carried out at 140°C for 30 minutes, resulting in a glucose conversion rate of 99.9% and an HMF yield of 43.5%.

[0048] Example 9

[0049] This embodiment prepares Lewis acid+ composed of choline chloride, ethylene glycol, maleic acid, and stannous chloride. The acid-bifunctional DES was prepared using the same method as the eutectic solvent synthesis method in Example 1, except that in this example, the ratio of choline chloride:ethylene glycol:maleic acid:stannous chloride was 5:1:1:0.1. 5-Hydroxymethylfurfural (HMF) was prepared according to the method in Example 2, and the glucose conversion rate and HMF yield were tested. The reaction was carried out at 140°C for 30 minutes, resulting in a glucose conversion rate of 99.9% and an HMF yield of 54.2%.

[0050] Example 10

[0051] This embodiment prepares Lewis acid+ composed of choline chloride, ethylene glycol, maleic acid, and stannous chloride. The acid-bifunctional DES was prepared using the same method as the eutectic solvent synthesis method in Example 1, except that in this example, the ratio of choline chloride:ethylene glycol:maleic acid:stannous chloride was 8:1:1:0.1. 5-Hydroxymethylfurfural (HMF) was prepared according to the method in Example 2, and the glucose conversion rate and HMF yield were tested. The reaction was carried out at 140°C for 30 minutes, resulting in a glucose conversion rate of 99.9% and an HMF yield of 44.8%.

[0052] Example 11

[0053] This embodiment prepares Lewis acid+ composed of choline chloride, ethylene glycol, maleic acid, and stannous chloride. The acid-bifunctional DES was prepared using the same method as the eutectic solvent synthesis method in Example 1, except that in this example, the ratio of choline chloride:ethylene glycol:maleic acid:stannous chloride was 2:1:1:0.1. 5-Hydroxymethylfurfural was prepared according to the method in Example 2, and the glucose conversion rate and HMF yield were tested. The reaction was carried out at 140°C for 30 minutes, resulting in a glucose conversion rate of 99.9% and an HMF yield of 37.1%.

[0054] Example 12

[0055] This embodiment prepares Lewis acid+ composed of choline chloride, ethylene glycol, maleic acid, and stannous chloride. The acid-bifunctional DES was prepared using the same method as the eutectic solvent synthesis method in Example 1, except that in this example, the ratio of choline chloride:ethylene glycol:maleic acid:stannous chloride was 3:0:1:0.1. 5-Hydroxymethylfurfural was prepared according to the method in Example 2, and the glucose conversion rate and HMF yield were tested. The reaction was carried out at 140°C for 30 minutes, resulting in a glucose conversion rate of 99.9% and an HMF yield of 46.7%.

[0056] Example 13

[0057] This embodiment prepares Lewis acid+ composed of choline chloride, ethylene glycol, maleic acid, and stannous chloride. The bifunctional acid DES was prepared using the same method as the eutectic solvent synthesis method in Example 1, except that in this example, the ratio of choline chloride:ethylene glycol:maleic acid:stannous chloride was 3:0.5:1:0.1. 5-Hydroxymethylfurfural was prepared according to the method in Example 2, and the glucose conversion rate and HMF yield were tested. The reaction was carried out at 140°C for 30 minutes, resulting in a glucose conversion rate of 99.9% and an HMF yield of 46.7%.

[0058] Example 14

[0059] This embodiment prepares Lewis acid+ composed of choline chloride, ethylene glycol, maleic acid, and stannous chloride. The acid-bifunctional DES was prepared using the same method as the eutectic solvent synthesis method in Example 1, except that in this example, the ratio of choline chloride:ethylene glycol:maleic acid:stannous chloride was 3:2:1:0.1. 5-Hydroxymethylfurfural was prepared according to the method in Example 2, and the glucose conversion rate and HMF yield were tested. The reaction was carried out at 140°C for 30 minutes, resulting in a glucose conversion rate of 99.9% and an HMF yield of 31.9%.

[0060] Comparative Example 1

[0061] This comparative example prepared a single component consisting of choline chloride, ethylene glycol, and maleic acid. The preparation method of the acid DES was the same as that of the eutectic solvent synthesis method in Example 1, except that in this comparative example, the ratio of choline chloride: ethylene glycol: maleic acid was 3:1:1. 5-Hydroxymethylfurfural was prepared according to the method in Example 2, and the glucose conversion rate and HMF yield were tested. The reaction was carried out at 140°C for 150 minutes, and the glucose conversion rate was 99.9%, while the HMF yield was 3.6%.

[0062] Comparative Example 2

[0063] This comparative example prepared a single Lewis acid DES composed of choline chloride, ethylene glycol, and stannous chloride. The preparation method was consistent with the eutectic solvent synthesis method in Example 1, except that the ratio of choline chloride:ethylene glycol:stannous chloride in this comparative example was 3:1:0.1. 5-Hydroxymethylfurfural was prepared according to the method in Example 2, and the glucose conversion rate and HMF yield were tested. The reaction was carried out at 140°C for 45 minutes, and the glucose conversion rate was 99.9%, while the HMF yield was 0.99%.

[0064] Example 15

[0065] Using ChCl-EG-MalA+SnCl2 prepared in Example 1 as a eutectic solvent, 5-hydroxymethylfurfural was prepared according to the method in Example 2, except that glucose was replaced with fructose. The fructose conversion rate and HMF yield were tested. The reaction was carried out at 140°C for 150 minutes, and the fructose conversion rate was 99.9% and the HMF yield was 77.2%.

[0066] Example 16

[0067] The method for preparing the eutectic solvent in this embodiment is consistent with the synthesis method of the eutectic solvent in Example 1, the difference being that stannous chloride is replaced with chromium trichloride, and the ratio of choline chloride:ethylene glycol:maleic acid:chromium trichloride is 3:1:1:0.1. 5-Hydroxymethylfurfural (HMF) was prepared according to the method in Example 2, and the glucose conversion rate and HMF yield were tested. The reaction was carried out at 140°C for 30 minutes, and the glucose conversion rate was 99.9%, while the HMF yield was 26.6%.

[0068] Comparative Example 3

[0069] The method for preparing the eutectic solvent in this embodiment is consistent with the synthesis method of the eutectic solvent in Example 1, the difference being that stannous chloride is replaced with aluminum trichloride, and the ratio of choline chloride:ethylene glycol:maleic acid:aluminum trichloride is 3:1:1:0.1. 5-Hydroxymethylfurfural (HMF) was prepared according to the method in Example 2, and the glucose conversion rate and HMF yield were tested. The reaction was carried out at 140°C for 30 minutes, and the glucose conversion rate was 99.9%, while the HMF yield was 14.8%.

[0070] Comparative Example 4

[0071] The method for preparing the eutectic solvent in this embodiment is consistent with the synthesis method of the eutectic solvent in Example 1, the difference being that stannous chloride is replaced with ferric chloride, and the ratio of choline chloride:ethylene glycol:maleic acid:ferric chloride is 3:1:1:0.1. 5-Hydroxymethylfurfural (HMF) was prepared according to the method in Example 2, and the glucose conversion rate and HMF yield were tested. The reaction was carried out at 140°C for 30 minutes, and the glucose conversion rate was 99.9%, and the HMF yield was 12.1%.

[0072] Comparative Example 5

[0073] The method for preparing the eutectic solvent in this embodiment is consistent with the synthesis method of the eutectic solvent in Example 1, the difference being that stannous chloride is replaced with copper dichloride, and the ratio of choline chloride:ethylene glycol:maleic acid:copper dichloride is 3:1:1:0.1. 5-Hydroxymethylfurfural (HMF) was prepared according to the method in Example 2, and the glucose conversion rate and HMF yield were tested. The reaction was carried out at 140°C for 30 minutes, and the glucose conversion rate was 99.9%, while the HMF yield was 6.7%.

[0074] Comparative Example 6

[0075] The method for preparing the eutectic solvent in this embodiment is consistent with the synthesis method of the eutectic solvent in Example 1, the difference being that maleic acid is replaced with citric acid, and the ratio of choline chloride:ethylene glycol:citric acid:stannous chloride is 3:1:1:0.1. 5-Hydroxymethylfurfural (HMF) was prepared according to the method in Example 2, and the glucose conversion rate and HMF yield were tested. The reaction was carried out at 140°C for 30 minutes, and the glucose conversion rate was 99.9%, and the HMF yield was 11.4%.

[0076] Comparative Example 7

[0077] The method for preparing the eutectic solvent in this embodiment is consistent with the synthesis method of the eutectic solvent in Example 1, the difference being that maleic acid is replaced with formic acid, and the ratio of choline chloride:ethylene glycol:formic acid:stannous chloride is 3:1:1:0.1. 5-Hydroxymethylfurfural (HMF) was prepared according to the method in Example 2, and the glucose conversion rate and HMF yield were tested. The reaction was carried out at 140°C for 30 minutes, and the glucose conversion rate was 99.9%, while the HMF yield was 23.9%.

[0078] Comparative Example 8

[0079] The method for preparing the eutectic solvent in this embodiment is consistent with the synthesis method of the eutectic solvent in Example 1, the difference being that maleic acid is replaced with hydrochloric acid, and the ratio of choline chloride:ethylene glycol:hydrochloric acid:stannous chloride is 3:1:1:0.1. 5-Hydroxymethylfurfural (HMF) was prepared according to the method in Example 2, and the glucose conversion rate and HMF yield were tested. The reaction was carried out at 140°C for 30 minutes, and the glucose conversion rate was 99.9%, while the HMF yield was 1.6%.

[0080] Example 17

[0081] This embodiment prepares Lewis acid+ composed of choline chloride, ethylene glycol, maleic acid, and stannous chloride. The acid bifunctional DES was prepared using the same method as the eutectic solvent synthesis method in Example 1, except that the reaction temperature was adjusted to 130°C. 5-Hydroxymethylfurfural was prepared according to the method in Example 2, and the glucose conversion rate and HMF yield were tested. At 130°C for 30 minutes, the glucose conversion rate was 99.9%, and the HMF yield was 51.2%.

[0082] Example 18

[0083] This embodiment prepares Lewis acid+ composed of choline chloride, ethylene glycol, maleic acid, and stannous chloride. The acid bifunctional DES was prepared using the same method as the eutectic solvent synthesis method in Example 1, except that the reaction temperature was adjusted to 120°C. 5-Hydroxymethylfurfural was prepared according to the method in Example 2, and the glucose conversion rate and HMF yield were tested. At 120°C for 30 minutes, the glucose conversion rate was 99.9%, and the HMF yield was 41.3%.

[0084] Example 19

[0085] This embodiment prepares Lewis acid+ composed of choline chloride, ethylene glycol, maleic acid, and stannous chloride. The acid bifunctional DES was prepared using the same method as the eutectic solvent synthesis method in Example 1, except that the reaction temperature was adjusted to 150°C. 5-Hydroxymethylfurfural was prepared according to the method in Example 2, and the glucose conversion rate and HMF yield were tested. At 150°C for 30 minutes, the glucose conversion rate was 99.9%, and the HMF yield was 49.4%.

[0086] Example 20

[0087] This embodiment prepares Lewis acid+ composed of choline chloride, ethylene glycol, maleic acid, and stannous chloride. The acid bifunctional DES was prepared using the same method as the eutectic solvent synthesis method in Example 1, except that the reaction time was adjusted to 10 minutes. 5-Hydroxymethylfurfural was prepared according to the method in Example 2, and the glucose conversion rate and HMF yield were tested. The reaction was carried out at 130°C for 10 minutes, resulting in a glucose conversion rate of 99.9% and an HMF yield of 36.4%.

[0088] Example 21

[0089] This embodiment prepares Lewis acid+ composed of choline chloride, ethylene glycol, maleic acid, and stannous chloride. The acid bifunctional DES was prepared using the same method as the eutectic solvent synthesis method in Example 1, except that the reaction time was adjusted to 20 minutes. 5-Hydroxymethylfurfural was prepared according to the method in Example 2, and the glucose conversion rate and HMF yield were tested. The reaction was carried out at 130°C for 20 minutes, resulting in a glucose conversion rate of 99.9% and an HMF yield of 54.8%.

[0090] Example 22

[0091] This embodiment prepares Lewis acid+ composed of choline chloride, ethylene glycol, maleic acid, and stannous chloride. The acid bifunctional DES was prepared using the same method as the eutectic solvent synthesis method in Example 1, except that the reaction time was adjusted to 60 minutes. 5-Hydroxymethylfurfural was prepared according to the method in Example 2, and the glucose conversion rate and HMF yield were tested. The reaction was carried out at 130°C for 60 minutes, resulting in a glucose conversion rate of 99.9% and an HMF yield of 36.3%.

[0092] Example 23

[0093] Using ChCl-EG-MalA+SnCl2 prepared in Example 1 as the eutectic solvent, a cyclic test was conducted according to the method in Example 2. After 6 cycles, 0.09 g of glucose was added each time, and the reaction was carried out at 140°C for 30 minutes. Heating was then stopped, and the liquid was allowed to cool to 25°C. The mixture was extracted 6 times with 5 mL of ethyl acetate each time, separating the upper phase solution and the lower phase DES. The DES was regenerated by heat treatment and directly used in the next cycle. Simultaneously, the glucose conversion rate and HMF yield in the upper phase extract of each cycle were analyzed by high-performance liquid chromatography (HPLC). After 6 cycles, the HMF yield decreased from 59.2% (first reaction) to 54.8% (6th cycle), a decrease of 7.4%. The glucose conversion rate remained at 99.9% throughout the 6 cycles, and there was no significant loss in the volume and mass of the DES. This indicates that the bifunctional DES prepared in Example 1 has good stability in catalyzing the conversion of glucose to HMF.

[0094] The appearance of the dual-function DES after each cycle of experiment is shown in the attached figure. Figure 2 As shown in the figure, as the number of reaction cycles increases, the color of DES gradually deepens from yellow to black. The polymerization of sugars and HMF in DES produces dark humic substances, which gradually accumulate with the increase of the number of cycles, leading to a darker color of DES and a decrease in HMF yield.

[0095] The specification and drawings of this invention are intended to be illustrative rather than restrictive. Based on this invention, those skilled in the art can make substitutions and modifications to some of the technical features without creative effort, and all such modifications are within the scope of protection of this invention.

Claims

1. A method for directly preparing 5-hydroxymethylfurfural from glucose using a eutectic solvent, characterized in that, Includes the following steps: S1. A eutectic solvent is synthesized using a heating method at 140°C for 30 minutes; the eutectic solvent contains hydrogen bond acceptors, Acidic hydrogen bond donor, viscosity-reducing hydrogen bond donor, and Lewis acidic component; the hydrogen bond acceptor is choline chloride; the... The acidic hydrogen bond donor is maleic acid; the viscosity-reducing hydrogen bond donor is one or more of ethylene glycol, 1,3-propanediol, 1,2-propanediol, 1,4-butanediol, and 1,3-butanediol; the Lewis acidic component is one or more of chromium trichloride, stannous chloride, and stannous tetrachloride; the hydrogen bond donor, The molar ratio of acidic hydrogen bond donors to viscosity-reducing hydrogen bond donors is 1:1:1 to 5:1:1; The molar ratio of acidic hydrogen bond donor to Lewis acidic component is 10:1 to 50:1; S2. Glucose and eutectic solvent are thoroughly mixed and sealed. The mixture is heated and continuously stirred to carry out the reaction. The reaction temperature is 140°C and the reaction time is 30 minutes. When the reaction is finished, the mixture is rapidly cooled and the 5-hydroxymethylfurfural in the reaction product is extracted with a solvent. S3. The eutectic solvent in the reaction product after extraction of 5-hydroxymethylfurfural is recovered and recycled.

2. The method according to claim 1, characterized in that, The hydrogen bond donor, The molar ratio of acidic hydrogen bond donor to viscosity-reducing hydrogen bond donor is 3:1:1; The molar ratio of the acidic hydrogen bond donor to the Lewis acidic component is 10:

1.

3. The method according to claim 1, characterized in that, In step S2, 5% molar glucose and a eutectic solvent are added and mixed for reaction; ethyl acetate is used to extract 5-hydroxymethylfurfural from the reaction product.

4. The method according to claim 1, characterized in that, In step S3, the extraction solvent is removed by evaporation, and the eutectic solvent is recovered for recycling.

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