Method for preparing 5-hydroxymethylfurfural by rapidly converting high-concentration biomass derived sugar

Abstract

The invention discloses a method for preparing 5-hydroxymethylfurfural by rapidly converting high-concentration biomass derived sugar, and belongs to the field of biomass catalytic conversion. The method comprises the following steps: mixing biomass derived sugar with a deep eutectic solvent, and carrying out closed reaction to obtain 5-hydroxymethylfurfural; the eutectic solvent comprises benzyl quaternary ammonium salt, organic acid and a cosolvent, and the organic acid is benzenesulfonic acid or organic dicarboxylic acid with 2-5 carbon atoms; the molar ratio of the benzyl quaternary ammonium salt to the organic acid to the cosolvent is (1-3): (0.5-1.5): (0-5); the concentration of the biomass derived sugar is 5 to 50 weight percent. The benzyl quaternary ammonium salt with a benzene ring is used as a hydrogen bond acceptor, the organic acid and the cosolvent are used as hydrogen bond donors to form the eutectic solvent, and a hydrogen bond network and an acid environment around the biomass derived sugar can be properly regulated and controlled by adjusting the proportion of the benzyl quaternary ammonium salt, the organic acid and the cosolvent, so that high-substrate sugar is efficiently and quickly converted into 5-hydroxymethylfurfural.

Description

Technical Field

[0001] The invention relates to the field of biomass catalytic conversion, and in particular to a method for rapidly converting high-concentration biomass-derived sugars to prepare 5-hydroxymethylfurfural. Background Art

[0002] 5-Hydroxymethylfurfural (5-HMF) is a key biomass-based compound with aldehyde, hydroxyl and furan ring structures. It can be converted into high value-added products through a variety of chemical reactions and used in fuels, coatings, biodegradable materials and drug synthesis. It is known as the bridge between biomass refining and petrochemical refining. The current industrial 5-HMF production process mainly includes water system, organic solvent system and ionic liquid system. Deep eutectic solvent (DES) is regarded as an effective alternative to overcome the shortcomings of ionic liquids and is known as a new generation of designed solvents that can simplify preparation and reduce costs while maintaining their advantages.

[0003] Patent CN116813579A discloses a method for preparing HMF by catalyzing the conversion of fructose and sucrose with a low eutectic solvent system, using a ternary low eutectic solvent of choline chloride / ethylene glycol / maleic acid (3:1:1), however, the above-mentioned ternary low eutectic solvent has a complex composition, containing choline chloride and ethylene glycol components that are easily soluble in organic solvents, which is not conducive to subsequent separation, and the yield of 5-HMF prepared by conversion is low (79.73%). CN118724846A discloses a method for preparing 5-hydroxymethylfurfural by catalyzing fructose with a low eutectic solvent, using a low eutectic solvent of triethylbenzyl ammonium chloride / acetic acid (2:3), the yield of 5-HMF of the low eutectic solvent is low under the condition of high bottom sugar concentration, and the reaction time is too long. Summary of the invention

[0004] In order to solve the problems existing in the above-mentioned prior art, the object of the present invention is to provide a method for rapidly converting high-concentration biomass-derived sugars to prepare 5-hydroxymethylfurfural.

[0005] Another object of the present invention is to provide application of the method in preparing 5-hydroxymethylfurfural.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] A method for rapidly converting high-concentration biomass-derived sugars to prepare 5-hydroxymethylfurfural, wherein the biomass-derived sugars are mixed with a deep eutectic solvent for a closed reaction to obtain 5-hydroxymethylfurfural;

[0008] The low eutectic solvent comprises a benzyl quaternary ammonium salt, an organic acid and a cosolvent, wherein the organic acid is benzenesulfonic acid or an organic dicarboxylic acid having 2 to 5 carbon atoms;

[0009] The molar ratio of the benzyl quaternary ammonium salt, the organic acid, and the cosolvent is (1-3):(0.5-1.5):(0-5);

[0010] The concentration of the biomass-derived sugar is 5 to 50 wt %.

[0011] The present invention adopts benzyl quaternary ammonium salt, organic acid and cosolvent as low eutectic solvent, which can be used as reaction solvent for preparing 5-hydroxymethyl furfural from biomass-derived sugar, and can also be used as catalyst for biomass-derived sugar. Benzyl quaternary ammonium salt is a hydrogen bond acceptor, organic acid and cosolvent are hydrogen bond donors, benzyl quaternary ammonium salt contains benzene ring structure, has excellent phase transfer ability, can be used as catalyst for organic reaction itself, benzene ring and fructose furan ring π-π stacking, its interaction makes reaction faster and substrate sugar concentration is increased at the same time. The strong electronegative structure of quaternary ammonium salt chloride ion can provide stronger hydrogen bond acceptor site, can form stronger hydrogen bond network with organic acid and cosolvent, improve the solubility of biomass-derived sugar, and then improve substrate sugar concentration. The organic acid of the present invention mainly adopts polyacid, polyacid can provide more hydrogen protons, build hydrogen bond network and provide acidic environment for reaction. Cosolvent regulates hydrogen bond network and acidic environment, and the three act together, thereby realizing efficient and rapid conversion of high substrate sugar into 5-hydroxymethyl furfural (5-HMF).

[0012] DES has a large number of hydrogen bond networks and an appropriate amount of acid protons, and has high solubility and reactivity for biomass-derived sugars, solving the problems of low raw sugar concentration, slow reaction rate, and low 5-HMF yield. The low eutectic solvent is used as a catalyst with moderate production cost, convenient production and storage, and can effectively reduce the energy consumption of the later reaction. DES as a catalyst has the advantages of being green, cheap, economical, and safe.

[0013] The hydrogen bond network of the deep eutectic solvent forms a hydrogen bond force with the product 5-HMF, which can effectively prevent the further reaction of 5-HMF and increase the yield of 5-HMF.

[0014] The aldehyde group and hydroxyl group on the product 5-hydroxymethylfurfural can also act as hydrogen bond donors and acceptors, forming a hydrogen bond network together with the DES solvent.

[0015] Preferably, the molar ratio of the benzyl quaternary ammonium salt, the organic acid and the co-solvent is (1-3):(0.5-1.5):(1-5).

[0016] In the present invention, the molar ratio of benzyl quaternary ammonium salt, organic acid and cosolvent is (1-3):(0.5-1.5):(1-5). By adjusting the ratio of benzyl quaternary ammonium salt, organic acid and cosolvent, the hydrogen bond network and acidic environment around the biomass-derived sugar can be properly regulated, thereby achieving efficient and rapid conversion of high-substrate sugar into 5-hydroxymethylfurfural (5-HMF).

[0017] In the present invention, the concentration of biomass-derived sugar is within the range of 5-50 wt%, which neither causes fructose accumulation to cause side reactions nor causes excess hydrogen protons in the low eutectic solvent to promote side reactions and reduce the yield of 5-hydroxymethylfurfural.

[0018] Preferably, the molar ratio of the benzyl quaternary ammonium salt, the organic acid and the cosolvent is 3:1.2:4.5. The present invention has found through research that 5-hydroxymethylfurfural has a better yield at this molar ratio.

[0019] Preferably, the concentration of the biomass-derived sugars is 5-35 wt%.

[0020] Specifically, the organic acid is at least one of anhydrous oxalic acid, oxalic acid containing two crystal waters, malonic acid, succinic acid, glutaric acid, maleic acid, fumaric acid, and p-toluenesulfonic acid.

[0021] It should be noted that the benzenesulfonic acid used in the present invention is p-toluenesulfonic acid. Because of the presence of hydrogen bond donors (hydrogen protons) and hydrogen bond acceptors (sulfur-oxygen double bonds) in its molecular structure, the hydrogen bond network constructed by p-toluenesulfonic acid for the reaction may be different from that of polyacids.

[0022] The organic acid selected in the present invention is an organic dicarboxylic acid or benzenesulfonic acid, which has a small acidity coefficient and weak corrosion to equipment. A part of the hydrogen protons released by the weakly acidic organic acid can form a hydrogen bond network with the benzyl quaternary ammonium salt, and the other part of the hydrogen protons provides an acidic environment, thereby catalyzing the reaction of biomass-derived sugars to generate 5-hydroxymethylfurfural.

[0023] Preferably, the organic acid is oxalic acid or malonic acid containing two crystal waters.

[0024] In the present invention, although the yield is the best using the malonic acid system, thermal decomposition occurs during use and the reaction system is unstable.

[0025] More preferably, the organic acid is oxalic acid containing 2 crystal waters.

[0026] Specifically, the co-solvent is at least one of water, ethylene glycol, propylene glycol, butylene glycol, and glycerol.

[0027] Preferably, the cosolvent is water or butanediol.

[0028] In the present invention, although the yield is the best using the butanediol system, it is not conducive to the subsequent extraction and separation of the product.

[0029] More preferably, the co-solvent is water.

[0030] Specifically, the biomass-derived sugar is at least one of fructose, glucose, sucrose, cellobiose, and microcrystalline cellulose.

[0031] Preferably, the biomass-derived sugar is fructose.

[0032] Specifically, the temperature of the closed reaction is 50-110°C.

[0033] Preferably, the temperature of the closed reaction is 90°C.

[0034] Specifically, the closed reaction time is 2.5min to 143h.

[0035] Preferably, the closed reaction time is 10 min to 23 h.

[0036] More preferably, the closed reaction time is 40 to 90 minutes.

[0037] Specifically, the benzyl quaternary ammonium salt is triethylbenzylammonium chloride.

[0038] Specifically, the preparation method of the low eutectic solvent comprises: mixing benzyl quaternary ammonium salt, organic acid and co-solvent to obtain the low eutectic solvent.

[0039] Specifically, the mixing temperature is 40 to 80°C.

[0040] Specifically, the mixing time is 0.5 to 4 hours.

[0041] The present invention also protects the application of the method in preparing 5-hydroxymethylfurfural.

[0042] Compared with the prior art, the present invention has the following beneficial effects:

[0043] (1) The present invention uses a benzyl quaternary ammonium salt with a benzene ring as a hydrogen bond acceptor, an organic acid and a cosolvent as a low eutectic solvent of a hydrogen bond donor, which can be used as a reaction solvent for preparing 5-hydroxymethylfurfural from fructose, and can also be used as a catalyst for catalyzing fructose. By adjusting the ratio of the benzyl quaternary ammonium salt, the organic acid and the cosolvent, the hydrogen bond network and the acidic environment around the biomass-derived sugar can be appropriately regulated, thereby achieving efficient and rapid conversion of high-substrate sugar into 5-hydroxymethylfurfural.

[0044] (2) The present invention does not require the addition of additional catalysts, reduces the steps of recovering the catalyst, and avoids the negative impact of adding catalysts to corrode the equipment. At the same time, the DES preparation process is simple and low in cost, which is economical, simple, and green and environmentally friendly.

[0045] (3) The low eutectic solvent system selected in the present invention can be used to prepare 5-hydroxymethylfurfural from biomass-derived sugars such as glucose, sucrose, cellobiose, and microcrystalline cellulose.

[0046] (4) Under the condition of high initial fructose concentration, the yield of 5-hydroxymethylfurfural can reach 87.80% (initial fructose concentration 10wt%) and 81.06% (initial fructose concentration 20wt%). Even at an ultra-high initial concentration of 50wt%, a high 5-hydroxymethylfurfural yield of 63.93% can be obtained by reacting at 90°C for 5h.

[0047] (5) The low eutectic solvent used in the present invention has a 5-hydroxymethylfurfural yield of 67.91% when the initial fructose concentration is 10wt%, the reaction temperature is 110°C, and the reaction time is 2.5min; and has a yield of 85.41% when the initial fructose concentration is 10wt%, the reaction temperature is 90°C, and the reaction time is 60min. The reaction rate is fast and the reaction time is short. DETAILED DESCRIPTION

[0048] The present invention is further described below in conjunction with examples. These examples are only used to illustrate the present invention and are not intended to limit the scope of the present invention. The experimental methods in the following examples that do not specify specific conditions are usually carried out according to conventional conditions in the art or according to the conditions recommended by the manufacturer; the raw materials, reagents, etc. used, unless otherwise specified, are all raw materials and reagents that can be obtained from commercial channels such as conventional markets. Any non-substantial changes and substitutions made by those skilled in the art on the basis of the present invention belong to the scope of protection claimed by the present invention.

[0049] The detection method of 5-HMF of the present invention is: high performance liquid chromatography detection method.

[0050] The specific test conditions are as follows: the mobile phase used in the test is 5mmol / L dilute sulfuric acid solution with a flow rate of 0.5mL / min; the chromatographic column is HPX-87H; the test temperature is 55°C; and the injection volume is 20μL.

[0051] The yield of 5-HMF was calculated according to the following formula: 5-HMF (%) = [(5-HMF concentration*reaction solution volume / 126.11 g / mol) / (mass of biomass-derived sugar converted to fructose / 180.16 g / mol)]*100.

[0052] Example 1 Composition of different organic acids in DES system

[0053] This embodiment provides a method for rapidly converting high-concentration biomass-derived sugars to prepare 5-hydroxymethylfurfural, comprising the following steps:

[0054] S1. Triethylbenzyl ammonium chloride (TEBAC) and an organic acid are mixed in a molar ratio of 1:1, and stirred in a three-necked flask at 60° C. for 2 h until the liquid becomes clear. The stirring speed may be 600 rpm to obtain a low eutectic solvent;

[0055] S2. mixing fructose and the low eutectic solvent in S1 and reacting them in a closed manner to obtain 5-hydroxymethylfurfural;

[0056] The organic acid in S1 is anhydrous oxalic acid, oxalic acid containing two crystal waters, malonic acid, succinic acid, glutaric acid, maleic acid, fumaric acid, and p-toluenesulfonic acid in Table 1.

[0057] In S2, the reaction temperature is 90°C, the reaction time is 10 min to 23 h, and the concentration of the fructose solution is 10 wt%.

[0058] In this embodiment, the mass of the deep eutectic solvent is 27 g, and the mass of fructose is 3 g, that is, the fructose concentration is 10 wt %. Specific condition parameters are shown in Table 1.

[0059] Table 1 Yield changes of 5-HMF yield under different organic acid conditions

[0060]

[0061] As can be seen from Table 1, under the same reaction conditions, the DES systems composed of different organic acids and TEBAC all have good effects in catalyzing fructose to produce 5-HMF. Among them, the 5-HMF yield of the TEBAC / malonic acid system is the best. However, the TEBAC / malonic acid system undergoes thermal decomposition during use, and the reaction system is unstable. Therefore, the TEBAC / oxalic acid system is used as the best system for catalyzing fructose to produce 5-HMF.

[0062] The 5-HMF yield of oxalic acid containing two crystal waters is higher than that of anhydrous oxalic acid system, probably because the crystal water in organic acid regulates the hydrogen bond network of DES system.

[0063] Composition of cosolvent in Example 2DES system

[0064] This embodiment provides a method for rapidly converting high-concentration biomass-derived sugars to prepare 5-hydroxymethylfurfural, and the implementation steps are the same as those of Example 1, except that in S1, triethylbenzyl ammonium chloride, oxalic acid and a cosolvent are mixed in a molar ratio of 1:1:1. See Table 2 for specific condition parameters.

[0065] Table 2 shows the yield changes of 5-HMF yield under different molar ratios

[0066]

[0067] As can be seen from Table 2, among these co-solvents, water, ethylene glycol and propylene glycol reduced the time and increased the 5-HMF yield to varying degrees compared to when no co-solvent was added. Glycerol reduced the reaction time compared to when no flux was added, but reduced the yield of 5-HMF. Butanediol did not reduce the reaction time compared to when no flux was added, but greatly increased the yield of 5-HMF. Among them, the addition of water and butanediol increased significantly, but in comparison, water has a lower cost and is easier to separate by extraction, so water should be selected as a co-solvent.

[0068] Example 3

[0069] This example provides a method for rapidly converting high-concentration biomass-derived sugars to prepare 5-hydroxymethylfurfural. The specific implementation steps are the same as those in Example 1. The difference from Example 1 is that the molar ratio of triethylbenzylammonium chloride, oxalic acid and co-solvent in S1 is different. See Table 3 for specific condition parameters.

[0070] Table 3 Yield changes of 5-HMF yield under different experimental conditions

[0071]

[0072]

[0073] As can be seen from Table 3, the molar ratio of triethylbenzylammonium chloride, oxalic acid and cosolvent has a significant effect on the yield of 5-HMF. The response surface analysis was performed on the test data (serial numbers 14 to 26). Through model fitting, it was found that the DES formed by the TEBAC / oxalic acid / water molar ratio of 3:1.2:4.5 can obtain a 5-HMF yield of 85.7% at 90°C for 60 minutes. This result was verified by a test, and it was found that the DES formed by the TEBAC / oxalic acid / water molar ratio of 3:1.2:4.5 can obtain a 5-HMF yield of 85.41% at 90°C for 60 minutes.

[0074] Example 4

[0075] This embodiment provides a method for rapidly converting high-concentration biomass-derived sugars to prepare 5-hydroxymethylfurfural, comprising the following steps:

[0076] S1. Triethylbenzyl ammonium chloride, oxalic acid (containing two molecules of crystal water) and water were mixed in a molar ratio of 3:1.2:4.5, and stirred in a three-necked flask at 60° C. for 2 h until the liquid became clear. The stirring speed may be 600 rpm to obtain a low eutectic solvent;

[0077] S2. mixing fructose and the low eutectic solvent in S1 and reacting them in a closed manner to obtain 5-hydroxymethylfurfural;

[0078] In S2, the reaction temperature is 50-110°C, the reaction time is 20min-143h, and the concentration of the fructose solution is 10wt%.

[0079] In this embodiment, when the mass of the deep eutectic solvent is 27 g, the mass of fructose is 3 g, that is, the fructose concentration is 10 wt %.

[0080] Table 4 Yield changes of 5-HMF yield under different experimental conditions

[0081]

[0082] As can be seen from Table 4, when TEBAC / oxalic acid / water (3:1.2:4.5), the closed mixed reaction at 50-110°C for 20min-143h has a good 5-HMF yield. The 5-HMF yields reached 88.62% and 87.80% at 70°C and 90°C for 23h and 1.5h, respectively; the reaction rate was faster at 90°C, and the 5-HMF yield was higher. Continuing to increase the temperature to 110°C, the reaction rate increased sharply, but it was not conducive to precise control of the reaction. Therefore, 90°C was selected as the optimal reaction temperature. It is worth noting that the system reacted at 110°C for 2.5min, and the 5-HMF yield was 67.91%, which shows that the system can achieve a higher 5-HMF yield in a short time, and the early reaction rate is fast.

[0083] Example 5

[0084] This example provides a method for rapidly converting high-concentration biomass-derived sugars to prepare 5-hydroxymethylfurfural, and the specific implementation steps are the same as those of Example 4, except that the reaction temperature in S2 is 90° C., and the initial fructose concentration is 5-50 wt %. See Table 5 for specific condition parameters.

[0085] Table 5 Yield changes of 5-HMF yield under different experimental conditions

[0086]

[0087] It can be seen from Table 5 that as the initial raw material concentration of fructose increases, its 5-HMF yield decreases accordingly. This is because the addition of a large amount of fructose leads to a large amount of accumulation of raw materials to generate by-products, and at the same time, the addition of a large amount of fructose destroys the composition of DES, resulting in a decrease in the 5-HMF yield. However, under the condition of high initial fructose concentration, the yield of 5-hydroxymethylfurfural can reach 87.80% (initial fructose concentration 10wt%) and 81.06% (initial fructose concentration 20wt%). Even at an ultra-high initial concentration of 50wt%, a high 5-hydroxymethylfurfural yield of 63.93% can be obtained by reacting at 90°C for 5h.

[0088] Example 6

[0089] This embodiment provides a method for rapidly converting high-concentration biomass-derived sugars to prepare 5-hydroxymethylfurfural. The specific implementation steps are the same as those in Example 4, except that the reaction temperature in S2 is 90° C., the reaction time is 1.5-35 h, and the concentration of the biomass-derived sugar is 10 wt %.

[0090] The biomass-derived sugar is glucose, sucrose, cellobiose or microcrystalline cellulose as shown in Table 6.

[0091] Table 6 Yield changes of 5-HMF yield under different experimental conditions

[0092]

[0093] It can be seen from Table 6 that glucose, sucrose, cellobiose and microcrystalline cellulose can all react in this system to produce 5-HMF. The 5-HMF yield of biomass derived sugars containing glucose or glucose in the hydrolyzate is relatively low.

[0094] Comparative Example 1

[0095] This comparative example provides a method for preparing 5-hydroxymethylfurfural from fructose, comprising the following steps:

[0096] S1. Choline chloride, oxalic acid (containing two molecules of crystal water) and water were mixed in a molar ratio of 3:1.2:4.5, and stirred in a three-necked flask at 60° C. for 2 h until the liquid was clear. The stirring speed may be 600 rpm to obtain a low eutectic solvent;

[0097] S2. mixing fructose and the low eutectic solvent in S1 and reacting them in a closed manner to obtain 5-hydroxymethylfurfural;

[0098] In S2, the reaction temperature is 90° C., the reaction time is 1.5 h, and the concentration of the fructose solution is 10 wt %. See Table 7 for specific condition parameters.

[0099] Comparative Example 2

[0100] This comparative example provides a method for preparing 5-hydroxymethylfurfural from fructose. The specific implementation steps are the same as those in comparative example 1. The difference from comparative example 1 is that the concentration of the fructose solution is 20wt%

[0101] Comparative Example 3

[0102] This comparative example provides a method for preparing 5-hydroxymethylfurfural from fructose. The specific implementation steps are the same as those of comparative example 1, except that: a low eutectic solvent is prepared according to CN116813579A, choline chloride, maleic acid and water are in a molar ratio of 3:1:1, the fructose concentration is 10wt%, and the reaction temperature is 90°C.

[0103] Table 7 Changes in the yield of 5-HMF under different experimental conditions in Comparative Examples 1 to 3

[0104]

[0105] As can be seen from Table 7, compared with the 72.3% 5-HMF yield obtained by reacting 1.5h at 90°C for choline chloride-based DES, the DES of the TEBAC system exhibits a better catalytic effect, and a 5-HMF yield of 87.8% is obtained under the same conditions. When the fructose concentration is increased to 20wt%, the TEBAC in the TEBAC / oxalic acid / water system is replaced with choline chloride, and the experimental results are as described in Comparative Example 2, and its 5-HMF yield is 63.7%, which is 17.3% lower than the 81.0% of the TEBAC / oxalic acid / water system under the same experimental conditions. This shows that the DES of the TEBAC system can not only convert high-concentration initial fructose into 5-HMF, but also obtain a high 5-HMF yield. It can be seen from Comparative Example 3 that, compared with the choline chloride / maleic acid / water system, the yield of 5-HMF increased by 11.9% using the TEBAC / oxalic acid / water system under the same conditions, which once again proved the excellent performance of the TEBAC / oxalic acid / water system at high initial sugar concentration, achieving the goal of efficiently and quickly converting high-substrate sugar into 5-hydroxymethylfurfural.

[0106] Obviously, the above embodiments of the present invention are only examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A method for rapidly converting high-concentration biomass-derived sugars to prepare 5-hydroxymethylfurfural, characterized in that: The biomass-derived sugar is mixed with a deep eutectic solvent to react in a closed manner to obtain 5-hydroxymethylfurfural; The low eutectic solvent comprises a benzyl quaternary ammonium salt, an organic acid and a cosolvent, wherein the organic acid is benzenesulfonic acid or an organic dicarboxylic acid having 2 to 5 carbon atoms; The molar ratio of the benzyl quaternary ammonium salt, the organic acid, and the cosolvent is (1-3):(0.5-1.5):(0-5); The concentration of the biomass-derived sugar is 5 to 50 wt %.

2. The method according to claim 1, characterized in that: The molar ratio of the benzyl quaternary ammonium salt, the organic acid and the co-solvent is (1-3):(0.5-1.5):(1-5).

3. The method according to claim 1, characterized in that: The organic acid is at least one of anhydrous oxalic acid, oxalic acid containing two crystal waters, malonic acid, succinic acid, glutaric acid, maleic acid, fumaric acid, and p-toluenesulfonic acid.

4. The method according to claim 1, characterized in that: The co-solvent is at least one of water, ethylene glycol, propylene glycol, butylene glycol and glycerol.

5. The method according to claim 1, characterized in that: The biomass-derived sugar is at least one of fructose, glucose, sucrose, cellobiose, and microcrystalline cellulose.

6. The method according to claim 1, characterized in that: The temperature of the closed reaction is 50-110°C.

7. The method according to claim 1, characterized in that: The closed reaction time is 2.5min to 143h.

8. The method according to claim 1, characterized in that: The benzyl quaternary ammonium salt is triethylbenzylammonium chloride.

9. The method according to claim 1, characterized in that: The preparation method of the low eutectic solvent comprises: mixing benzyl quaternary ammonium salt, organic acid and co-solvent to obtain the low eutectic solvent.

10. Use of the method according to any one of claims 1 to 9 in the preparation of 5-hydroxymethylfurfural.

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