Ion-pair-bound homogeneous catalytic system, and method for synthesizing 5-hydroxymethylfurfural

Abstract

An ion-pair-bound homogeneous catalytic system, and a method for synthesizing 5-hydroxymethylfurfural. The homogeneous catalytic system comprises a quaternary ammonium salt, a homogeneous acid and water. The method comprises: mixing fructose with an ion-pair-bound homogeneous catalytic system to form a homogeneous catalytic reaction system; reacting the homogeneous catalytic reaction system under reduced pressure, and after the completion of the reaction, adding a quenching agent to quench the reaction; extracting the obtained reaction mixture; and then respectively separating 5-hydroxymethylfurfural and the ion-pair-bound homogeneous catalytic system from a light phase and a heavy phase formed after the extraction. The reaction can achieve the simple, safe and efficient synthesis of 5-hydroxymethylfurfural under mild conditions; the conversion rate of the raw material fructose is high; the yield of the target product, i.e., 5-hydroxymethylfurfural, is high; and the separation operation can be conveniently conducted. Moreover, the used ion-pair-bound homogeneous catalytic system that is formed from a quaternary ammonium salt, a homogeneous acid and water is convenient to recover and reuse. Therefore, the method is environmentally friendly and economical, and has broad application prospects.

Description

Ionic pair-bound homogeneous catalytic system and method for synthesizing 5-hydroxymethylfurfural

[0001] This application claims priority to Chinese Patent Application No. CN202411134688.2, filed on August 15, 2024, entitled "Ionic pair-bound homogeneous catalytic system and method for synthesizing 5-hydroxymethylfurfural", which is incorporated by reference in its entirety. TECHNICAL FIELD

[0002] The present application specifically relates to an ionic pair-bound homogeneous catalytic system for synthesizing 5-hydroxymethylfurfural (HMF) and its application in a process for synthesizing 5-hydroxymethylfurfural from fructose, belonging to the technical field of chemical industry. BACKGROUND

[0003] The six-carbon furfural central route based on the sugar platform has always been a focus of scientific research and industry. Specifically, it is to use non-food biomass to scale up the preparation of fructose or glucose as raw material, catalytically dehydrate to obtain the key intermediate 5-hydroxymethylfurfural, and then obtain various important furan derivatives through oxidation, hydrogenation, etherification, esterification and other reactions. In the process of preparing 5-hydroxymethylfurfural from fructose, there are many types of side reactions, and the structures of the generated by-products are complex. Various by-products, fructose and 5-hydroxymethylfurfural generated during the reaction process will polymerize to form humin, which is difficult to handle, and it is easy to adhere to the reaction container, affecting the reaction process. At the same time, 5-hydroxymethylfurfural has the characteristics of low melting point, high boiling point, and good compatibility, making it difficult to separate 5-hydroxymethylfurfural from by-products by means of crystallization, distillation and extraction. Moreover, 5-hydroxymethylfurfural molecules are very sensitive and can easily degrade under the action of various components. Only when 5-hydroxymethylfurfural is purified to more than 98% can it be stably stored. How to improve the yield of 5-hydroxymethylfurfural and achieve its efficient separation and purification has always been an important problem in the field.

[0004] For the process route of synthesizing 5-hydroxymethylfurfural from fructose dehydration, the matching degree between the solvent and the acid catalyst is required to be high. A method for synthesizing 5-hydroxymethylfurfural proposed by a researcher is to use an organic solvent to extract the HMF product generated in the fructose dehydration in situ, so as to separate the HMF and the acid catalyst into two phases, avoid the acid catalytic degradation of the HMF, and improve the HMF yield in the fructose conversion process. However, the boiling point of the additional organic extractant is high, the reaction temperature is high, the extractant is difficult to recover, and it is difficult to separate 5-hydroxymethylfurfural subsequently. A researcher uses a eutectic solvent system formed by choline chloride, p-hydroxybenzoic acid and anhydrous aluminum chloride to catalyze the dehydration of xylose to furfural. Compared with the organic solvent and ionic liquid system, the reaction condition is mild and the price is low by using the eutectic system, but the choline chloride and the catalyst are still difficult to recover, and the sugar treatment amount in this method is low, which is not conducive to the industrial production mode. For the acid catalyst, the common fructose dehydration catalysts include homogeneous acid and heterogeneous acid. Because a large amount of humin is generated in the fructose dehydration process to cover the active sites of the heterogeneous acid, the activity of the heterogeneous acid catalyst will decrease rapidly with the reuse times. The homogeneous acid is more suitable for the fructose dehydration process because of the similar polarity between the homogeneous acid and fructose. However, in the conventional solvent system, the homogeneous acid will cause the rapid decomposition of HMF while catalyzing the fructose dehydration. Therefore, it is necessary to select a suitable solvent system and acid catalyst to form a suitable reaction system of fructose, solvent and acid catalyst at the same time, so as to improve the yield of HMF prepared from fructose dehydration. This is also a long-cherished goal of the skilled person in the field that has not been achieved for a long time.

[0005] SUMMARY

[0006] The main purpose of the present application is to provide an ion pair bound homogeneous catalytic system and a method for synthesizing 5-hydroxymethylfurfural, so as to overcome the shortcomings of the prior art.

[0007] In order to achieve the above-mentioned purpose, the following technical solutions are adopted in the present application:

[0008] The first aspect of the present application provides an ion pair bound homogeneous catalytic system, which comprises a quaternary ammonium salt, a homogeneous acid and water.

[0009] In one embodiment, the mass ratio of the quaternary ammonium salt, the homogeneous acid and water contained in the ion pair bound homogeneous catalytic system is 25-80: 0.1-5: 4-15.

[0010] In one embodiment, the chemical formula of the quaternary ammonium salt is R4NX, wherein the hydrocarbon group R comprises substituted and / or unsubstituted alkyl and / or aryl, and the substituted and / or unsubstituted alkyl is preferably substituted or unsubstituted C1-C20 alkyl, more preferably substituted or unsubstituted C1-C10 alkyl, and even more preferably substituted or unsubstituted C1-C6 alkyl. 18 The alkyl group X includes but is not limited to F - , Cl - , Br -I - , NO2 - , NO3 - or SO4 2- . Among them, the four hydrocarbon groups R can be consistent or inconsistent. Illustratively, the quaternary ammonium salt can be selected from, but not limited to, tetraethylammonium bromide, tetraethylammonium chloride, tetramethylammonium iodide, tetrabutylammonium fluoride, tetrapropylammonium chloride, trimethylhexadecylammonium bromide, trimethyloctadecylammonium chloride, tetraethylammonium nitrate, tetraethylammonium nitrite, choline bromide, etc.

[0011] In one embodiment, the homogeneous acid comprises HF, HCl, HBr, HI, H2SO4, HNO3, trifluoromethanesulfonic acid, benzenesulfonic acid, methanesulfonic acid, p-toluenesulfonic acid or dodecylbenzenesulfonic acid, and the like. Preferably, the homogeneous acid can be selected from HCl, HBr, methanesulfonic acid or H2SO4, which have moderate acidity and strong interaction with the quaternary ammonium salt, and are more likely to form ion pair constraints with the quaternary ammonium salt in the aqueous phase.

[0012] The second aspect of the present application provides the use of the ion pair constrained homogeneous catalytic system in the method for synthesizing 5-hydroxymethylfurfural from fructose.

[0013] The third aspect of the present application provides a method for synthesizing 5-hydroxymethylfurfural, comprising:

[0014] providing an ion pair constrained homogeneous catalytic system comprising a quaternary ammonium salt, a homogeneous acid and water;

[0015] mixing fructose with the ion pair constrained homogeneous catalytic system to form a homogeneous catalytic reaction system;

[0016] reacting the homogeneous catalytic reaction system under reduced pressure, adding a quenching agent to quench the reaction after the reaction is completed, and then separating 5-hydroxymethylfurfural and the ion pair constrained homogeneous catalytic system from the obtained reaction mixture.

[0017] In one embodiment, the mass ratio of the quaternary ammonium salt, the homogeneous acid and water in the ion pair constrained homogeneous catalytic system is 25-80: 0.1-5: 4-15.

[0018] In one embodiment, the construction process of the homogeneous catalytic reaction system comprises the following two steps:

[0019] (a) mixing the quaternary ammonium salt, the homogeneous acid and water uniformly to form the ion pair constrained homogeneous catalytic system;

[0020] (b) adding fructose to the ion pair constrained homogeneous catalytic system and mixing uniformly to form a homogeneous single-phase mixture, i.e. the homogeneous catalytic reaction system.

[0021] Exemplarily, the quaternary ammonium salt, the homogeneous acid and water can be mixed in any manner, for example, mixed uniformly by stirring or the like to form a paste-like mixture with poor fluidity. Then, fructose is added to the paste-like mixture and mixed uniformly, preferably at 20-100°C, to form a uniform transparent single-phase liquid, i.e. the homogeneous catalytic reaction system.

[0022] In the present application, the reaction is mainly a dehydration reaction of fructose.

[0023] In one embodiment, the method comprises:

[0024] The reaction mixture is subjected to extraction treatment with an extractant, and then separated to obtain a light phase and a heavy phase;

[0025] 5-hydroxymethylfurfural is separated from at least the light phase;

[0026] and the ion pair bound homogeneous catalytic system is separated from at least the heavy phase.

[0027] Further, the quenching agent comprises water. The extractant comprises an organic solvent.

[0028] Further, the light phase is an organic phase containing 5-hydroxymethylfurfural and the extractant. The heavy phase is an aqueous phase containing the quaternary ammonium salt, the homogeneous acid, the quenching agent and the residual extractant.

[0029] When the ion pair bound homogeneous catalytic system provided by the present application is applied to the process for synthesizing 5-hydroxymethylfurfural from fructose, on the one hand, the quaternary ammonium salt can be combined with fructose through intermolecular hydrogen bonds, destroying the hydrogen bond interaction between fructose molecules and the positive-negative ion interaction between quaternary ammonium salt molecules, promoting the melting of both at a temperature lower than their respective melting points to form a viscous liquid. By adding a small amount of water, it can act as a medium to promote the formation of intermolecular hydrogen bonds between fructose and quaternary ammonium salt, accelerate the formation of intermolecular hydrogen bonds, so that fructose and the catalytic system can more efficiently form a eutectic system, and finally form a uniform transparent single-phase liquid. In addition, the presence of intermolecular hydrogen bonds greatly improves the solubility of fructose in the system, increasing the processing capacity of the system for fructose. Especially, the ion pair bound homogeneous catalytic system activates each hydroxyl group of fructose, improves the reaction performance of fructose, thereby accelerating the rate of fructose dehydration reaction, improving the selectivity and reducing the side reactions, and finally promoting the efficient and selective dehydration reaction of fructose. On the other hand, after the reaction is completed, when 5-hydroxymethylfurfural is separated by extraction with an organic solvent, the quaternary ammonium salt and the homogeneous acid form an ion pair binding with high stability in the aqueous phase, so it will not be extracted into the organic phase. Moreover, the quaternary ammonium salt and the homogeneous acid are relatively stable in the aqueous phase and will not be decomposed in the subsequent separation process, so that the ion pair bound homogeneous catalytic system and the organic solvent for extraction are more easily recycled and reused.

[0030] In one embodiment, the chemical formula of the quaternary ammonium salt is R4NX, wherein the hydrocarbon group R comprises substituted and / or unsubstituted alkyl and / or aryl, wherein the substituted and / or unsubstituted alkyl is preferably substituted or unsubstituted C1-C20 alkyl, and the substituted and / or unsubstituted aryl is preferably substituted or unsubstituted C6-C20 aryl. 18 alkyl, X includes but is not limited to F - , Cl - , Br - , I - , NO2 - , NO3 - or SO4 2- . Among them, the four hydrocarbon groups R can be consistent or inconsistent. For example, the quaternary ammonium salt can be selected from but not limited to tetraethylammonium bromide, tetraethylammonium chloride, tetramethylammonium iodide, tetrabutylammonium fluoride, tetrapropylammonium chloride, trimethylhexadecylammonium bromide, trimethyloctadecylammonium chloride, tetraethylammonium nitrate, tetraethylammonium nitrite, choline bromide, etc.

[0031] In one embodiment, the homogeneous acid includes but is not limited to HF, HCl, HBr, HI, H2SO4, HNO3, trifluoromethanesulfonic acid, benzene sulfonic acid, methanesulfonic acid, p-toluenesulfonic acid or dodecylbenzenesulfonic acid, etc.

[0032] In one embodiment, the form of the fructose includes but is not limited to crystalline fructose, liquid fructose, fructose syrup, high fructose syrup or fructose-glucose syrup, etc., wherein the content of fructose in the dry matter is > 85wt%.

[0033] In one embodiment, the homogeneous catalytic reaction system comprises fructose, quaternary ammonium salt, homogeneous acid and water in a mass ratio of 5-80:5-90:0.05-10:4-50.

[0034] More preferably, the homogeneous catalytic reaction system comprises fructose, quaternary ammonium salt, homogeneous acid and water in a mass ratio of 20-50:25-80:0.1-5:4-15.

[0035] More preferably, the homogeneous catalytic reaction system comprises fructose, quaternary ammonium salt, homogeneous acid and water in a mass ratio of 20-50:25-80:0.1-5:4-15.

[0036] In one embodiment, the method comprises: uniformly mixing the quaternary ammonium salt, the homogeneous acid and water to form the ion pair bound homogeneous catalytic system; and the ion pair bound homogeneous catalytic system and the homogeneous catalytic reaction system are both prepared at a temperature of 20-100°C.

[0037] In one embodiment, the reaction temperature of the reaction can be 50-200°C, preferably 50-150°C, more preferably 60-120°C. Too low or too high reaction temperature will result in a decreased yield of the target product 5-hydroxymethylfurfural.

[0038] In one embodiment, the reaction time of the reaction is 5-240 min.

[0039] In one embodiment, the reaction pressure of the reaction is -0.1 MPa to -0.015 MPa, preferably -0.1 MPa to -0.03 MPa, preferably -0.1 MPa to -0.05 MPa, preferably -0.1 MPa to -0.075 MPa, preferably -0.1 MPa to -0.08 MPa, so as to make the reaction more complete.

[0040] In one embodiment, the pH value of the reaction system is maintained at 0-1 during the reaction.

[0041] In one embodiment, the method comprises: after the reaction, adding a quenching agent with a mass of 1-5 times the total mass of the reaction system to quench the reaction.

[0042] In one embodiment, the extractant comprises, but is not limited to, one or more combinations of organic solvents such as petroleum ether, cyclohexane, n-hexane, diethyl ether, ethyl acetate, acetonitrile, dichloroethane, tetrahydrofuran, etc.

[0043] In one embodiment, the extractant is added in an amount of 1-5 times the mass of the reaction mixture.

[0044] In one embodiment, the extraction process includes any one of single-stage extraction, multi-stage countercurrent extraction, or multi-stage crossflow extraction.

[0045] In one embodiment, the method comprises: separating and recovering the extractant from the light phase by at least a reduced pressure distillation method, and obtaining 5-hydroxymethylfurfural.

[0046] Further, in some of the above embodiments, the conversion rate of fructose in the reaction of preparing 5-hydroxymethylfurfural from fructose is >98%, the yield of 5-hydroxymethylfurfural is >85%, and the purity of the separated 5-hydroxymethylfurfural is >98%.

[0047] In one embodiment, the method comprises: separating and recovering the extractant and part of the water in the heavy phase by at least a reduced pressure distillation method, so as to recover the ion pair bound homogeneous catalytic system.

[0048] Specifically, for the heavy phase, different temperature fractions can be collected, for example, the residual organic extractant in the heavy phase is recovered first, then the water in the heavy phase is separated, by controlling the amount of water separated, the water added in the quenching stage and the water generated in the dehydration reaction can be removed, and a mixed system of quaternary ammonium salt, homogeneous acid and water corresponding to the ion pair bound homogeneous catalytic system can be obtained, that is, the ion pair bound homogeneous catalytic system is recovered.

[0049] In one embodiment, the method further comprises mixing the recovered ion pair bound homogeneous catalytic system with fructose to form a homogeneous catalytic reaction system, and performing the reaction again.

[0050] In a more specific embodiment, the method can comprise the following steps:

[0051] (1) The homogeneous catalytic reaction system is placed in a sealed reaction container and heated, and is allowed to react under reduced pressure;

[0052] (2) After the reaction is completed, the pressure in the reaction container is restored to normal pressure, a quenching agent is added to quench the reaction, then an extractant is used to extract 5-hydroxymethylfurfural, and after the extraction is completed, the light phase and the heavy phase are separated;

[0053] (3) The light phase is separated by reduced pressure distillation to recover the extractant, and 5-hydroxymethylfurfural with a purity of > 98% is obtained;

[0054] (4) The heavy phase is separated by reduced pressure distillation to remove the residual extractant and excess water (including byproduct water generated in the reaction and water as a quenching agent), and a reusable ion pair bound homogeneous catalytic system is obtained.

[0055] Further, the ion pair bound homogeneous catalytic system recovered in the present application can be repeatedly used in the reaction of fructose dehydration to prepare 5-hydroxymethylfurfural, and can be used for more than 30 times while maintaining a catalytic efficiency of more than 90%.

[0056] Compared with the prior art, the present application has at least the following advantages:

[0057] (1) The method for synthesizing 5-hydroxymethylfurfural provided in the present application uses an ion pair bound homogeneous catalytic system containing quaternary ammonium salt and homogeneous acid to perform fructose dehydration reaction. From the reaction mechanism, quaternary ammonium salt and fructose can form rich intermolecular hydrogen bonds in the presence of water, thereby reducing the melting point of the two, forming a low eutectic system, and the two are mutually soluble in a wide mass ratio range, which can increase the concentration of fructose in the reaction, thereby effectively increasing the generation rate of 5-hydroxymethylfurfural.

[0058] (2) The method for synthesizing 5-hydroxymethylfurfural provided in the application forms a stable ion pair binding homogeneous catalytic system through "quaternary ammonium salt binding homogeneous acid", which improves the ability of acid-catalyzed dehydration reaction, and can simply, safely and efficiently synthesize 5-hydroxymethylfurfural under mild conditions. On the one hand, the treatment amount of fructose is large, and the yield of the target product is high. On the other hand, due to the large difference in polarity between the quaternary ammonium salt and 5-hydroxymethylfurfural, the quaternary ammonium salt and 5-hydroxymethylfurfural generated in the reaction can be simply separated by using an organic solvent. Moreover, due to the formation of a bound ion pair through ionic bonding between the quaternary ammonium salt and the homogeneous acid, the loss amount of the two is extremely low. The quaternary ammonium salt and the homogeneous acid can be used for recycling after distillation dehydration, which greatly reduces the cost of solvents and catalysts in the production of 5-hydroxymethylfurfural.

[0059] (3) In the method for synthesizing 5-hydroxymethylfurfural provided in the application, the ion pair binding homogeneous catalytic system is adopted, and the reaction is carried out under reduced pressure, which helps to make the dehydration reaction more fully, and the time of the reaction under reduced pressure can be 1 / 2 to 1 / 4 of that under normal pressure at the same fructose conversion rate, while the selectivity of the product can also be significantly improved. The reduced pressure condition accelerates the dehydration reaction, reduces the duration of high-concentration 5-hydroxymethylfurfural in the reaction process, and reduces the amount of humin generated in the reaction process, which is beneficial to the subsequent product separation and solvent recycling process.

[0060] (4) In the method for synthesizing 5-hydroxymethylfurfural provided in the application, the yield and purity of 5-hydroxymethylfurfural are relatively high, and the preparation process is simple, the energy consumption is low, the manufacturing cost is low, and it is extremely suitable for large-scale industrial promotion.

[0061] (5) In the method for synthesizing 5-hydroxymethylfurfural provided in the application, the amount of water separated in the dehydration reaction under reduced pressure can be used to judge the degree of reaction, so as to avoid overreaction, thereby preventing the over-dehydration of the product 5-hydroxymethylfurfural to form humin.

[0062] (6) In the method for synthesizing 5-hydroxymethylfurfural provided in the application, a small amount of homogeneous acid can be used to obtain a relatively high yield of 5-hydroxymethylfurfural (the yield can be as high as 95%, and the purity can be more than 99%), and the catalytic system does not contain metal, which reduces the impact on the environment, is green and environmentally friendly, and meets the requirements of sustainable development. DETAILED DESCRIPTION

[0063] As described above, in view of the deficiencies of the prior art, the inventors of the present application propose a method for synthesizing 5-hydroxymethylfurfural by using an ion pair binding homogeneous catalytic system, which includes the construction of the ion pair binding homogeneous catalytic system and the reaction of fructose dehydration to prepare 5-hydroxymethylfurfural.

[0064] In some more specific embodiments, the method for synthesizing 5-hydroxymethylfurfural provided by the present application comprises the following steps:

[0065] S1, construction of the homogeneous catalytic reaction system, comprising:

[0066] S11) mixing the quaternary ammonium salt, the homogeneous acid and water uniformly to form an ion pair binding homogeneous catalytic system.

[0067] S12) mixing the fructose with the ion pair binding homogeneous catalytic system to form a homogeneous single-phase mixture, i.e. the homogeneous catalytic reaction system.

[0068] S2, dehydration of fructose to prepare 5-hydroxymethylfurfural, comprising:

[0069] S21) heating the homogeneous catalytic reaction system and performing the dehydration reaction under reduced pressure.

[0070] S22) after the dehydration reaction is completed, restoring the pressure of the reaction system to normal pressure, adding a quenching agent to quench the reaction, then using an extractant to extract 5-hydroxymethylfurfural, and separating the light phase and the heavy phase after the extraction is completed.

[0071] S23) separating and recovering the extractant from the light phase by reduced pressure distillation, and obtaining 5-hydroxymethylfurfural with a purity of > 98%.

[0072] S24) separating the residual extractant and excess water from the heavy phase by reduced pressure distillation to obtain a reusable ion pair binding homogeneous catalytic system.

[0073] Wherein, the execution order of steps S23 and S24 can be reversed, or they can be performed simultaneously.

[0074] In one embodiment, the homogeneous catalytic reaction system comprises fructose, quaternary ammonium salt, homogeneous acid and water in a mass ratio of 5-80:5-90:0.05-10:4-50, wherein the total content of all components is 100wt%. Preferably, the homogeneous catalytic reaction system comprises fructose, quaternary ammonium salt, homogeneous acid and water in a mass ratio of 10-70:25-80:0.1-5:4-15. The types of fructose, quaternary ammonium salt and homogeneous acid are as described above.

[0075] In one embodiment, the preparation temperature of the homogeneous catalytic reaction system is 20-100°C.

[0076] In one embodiment, the reaction is carried out at a pressure of -0.1Mpa to -0.015MPa and a temperature of 50-200°C, the reaction time can be 5-240min, and the pH value of the reaction system is maintained at 0-1 during the dehydration reaction.

[0077] In one embodiment, the quenching agent comprises water, and the quenching agent is added in an amount of 1-5 times the total mass of the reaction system.

[0078] In one embodiment, the extraction agent is added in an amount of 1-5 times the total mass of the system after quenching.

[0079] In the method for synthesizing 5-hydroxymethylfurfural according to the present application, by using the above ion pair bound homogeneous catalytic system, especially under the reduced pressure reaction condition, the reactivity and conversion rate of fructose can be significantly improved, thereby improving the production efficiency and yield of 5-hydroxymethylfurfural. Meanwhile, the quenching and extraction methods used are matched with the homogeneous catalytic reaction system used for performing the dehydration reaction, so that the highly sensitive product 5-hydroxymethylfurfural can be quickly stabilized and separated to obtain a pure product at the end of the reaction. Moreover, due to the interaction between the quaternary ammonium salt and the homogeneous acid, the homogeneous catalytic system in the present application is easy to separate from the product, has good recycling performance, and can be repeatedly used for more than 30 times under industrial conditions, thereby greatly reducing the solvent and catalyst cost in the production process of 5-hydroxymethylfurfural.

[0080] The present application will be described in detail below with reference to the examples, but the embodiments of the present application are not limited thereto. Obviously, the examples described below are only some of the embodiments of the present application, and other similar embodiments obtained by those skilled in the art without creative effort fall within the protection scope of the present application.

[0081] Unless otherwise specified, the raw materials used in the following examples can be obtained from the market or self-made according to the references, and the production equipment, test equipment and test methods used can also be common equipment or methods in the art.

[0082] In the following examples, the yield calculation formula is as follows:

[0083] Yield = (actual yield / theoretical yield) x 100%.

[0084] Example 1: The preparation method of a homogeneous catalytic reaction system provided in the present embodiment comprises:

[0085] Step a: tetraethylammonium bromide, methanesulfonic acid and water are added to a reaction container and mixed uniformly, and heated to 50°C and stirred at constant temperature.

[0086] Step b: crystalline fructose is added to the above mixture, and stirring is continued to form a uniform single-phase mixture.

[0087] The mass ratio of the quaternary ammonium salt, crystalline fructose, methanesulfonic acid and water contained in the homogeneous catalytic reaction system is 60:30:1:9.

[0088] Embodiment 2: A preparation method of a homogeneous catalytic reaction system provided in the embodiment comprises:

[0089] Step a, tetraethylammonium chloride, trifluoromethyl sulfonic acid and water are added into a reaction container and mixed uniformly, heated to 100°C, and constant temperature stirring.

[0090] Step b, crystalline fructose is added into the above mixture, and continues to stir to form a uniform single-phase mixture.

[0091] The homogeneous catalytic reaction system contains quaternary ammonium salt, crystalline fructose, trifluoromethyl sulfonic acid and water in a mass ratio of 80:25:3:5.

[0092] Embodiment 3: A preparation method of a homogeneous catalytic reaction system provided in the embodiment comprises:

[0093] Step a, tetramethylammonium iodide, benzenesulfonic acid and water are added into a reaction container and mixed uniformly, heated to 20°C, and constant temperature stirring.

[0094] Step b, liquid fructose is added into the above mixture, and continues to stir to form a uniform single-phase mixture.

[0095] The homogeneous catalytic reaction system contains quaternary ammonium salt, liquid fructose, benzenesulfonic acid and water in a mass ratio of 42:40:3:15.

[0096] Embodiment 4: A preparation method of a homogeneous catalytic reaction system provided in the embodiment comprises:

[0097] Step a, tetraethylammonium bromide, hydrofluoric acid and water are added into a reaction container and mixed uniformly, heated to 50°C, and constant temperature stirring.

[0098] Step b, fructose syrup is added into the above mixture, and continues to stir to form a uniform single-phase mixture.

[0099] The homogeneous catalytic reaction system contains quaternary ammonium salt, fructose syrup, hydrofluoric acid and water in a mass ratio of 50:43:2:5.

[0100] Embodiment 5: A preparation method of a homogeneous catalytic reaction system provided in the embodiment comprises:

[0101] Step a, tetrabutylammonium fluoride, sulfuric acid and water are added into a reaction container and mixed uniformly, heated to 50°C, and constant temperature stirring.

[0102] Step b, high fructose syrup is added into the above mixture, and continues to stir to form a uniform single-phase mixture.

[0103] The homogeneous catalytic reaction system contains quaternary ammonium salt, high fructose syrup, sulfuric acid and water in a mass ratio of 60:25:5:10.

[0104] Embodiment 6: A preparation method of a homogeneous catalytic reaction system provided in the embodiment comprises:

[0105] Step a, tetrapropylammonium chloride, nitric acid and water are added into a reaction container and mixed uniformly, heated to 80℃, and constant temperature stirring.

[0106] Step b, fructose syrup (F90 type) is added into the above mixture, and continues to stir to form a uniform single-phase mixture.

[0107] The homogeneous catalytic reaction system contains quaternary ammonium salt, fructose syrup, nitric acid and water in a mass ratio of 70:20:4:6.

[0108] Embodiment 7: A preparation method of a homogeneous catalytic reaction system provided in the embodiment comprises:

[0109] Step a, trimethylhexadecylammonium bromide, methanesulfonic acid and water are added into a reaction container and mixed uniformly, and constant temperature stirring at 20℃.

[0110] Step b, crystalline fructose is added into the above mixture, and continues to stir to form a uniform single-phase mixture.

[0111] The homogeneous catalytic reaction system contains quaternary ammonium salt, crystalline fructose, methanesulfonic acid and water in a mass ratio of 35:50:5:10.

[0112] Embodiment 8: A preparation method of a homogeneous catalytic reaction system provided in the embodiment comprises:

[0113] Step a, trimethyloctadecylammonium chloride, p-toluenesulfonic acid and water are added into a reaction container and mixed uniformly, heated to 80℃, and constant temperature stirring.

[0114] Step b, crystalline fructose is added into the above mixture, and continues to stir to form a uniform single-phase mixture.

[0115] The homogeneous catalytic reaction system contains quaternary ammonium salt, crystalline fructose, p-toluenesulfonic acid and water in a mass ratio of 35:25:5:35.

[0116] Embodiment 9: A preparation method of a homogeneous catalytic reaction system provided in the embodiment comprises:

[0117] Step a, tetraethylammonium nitrate, hydrochloric acid and water are added into a reaction container and mixed uniformly, heated to 50℃, and constant temperature stirring.

[0118] Step b, crystalline fructose is added into the above mixture, and continues to stir to form a uniform single-phase mixture.

[0119] The homogeneous catalytic reaction system contains quaternary ammonium salt, crystalline fructose, hydrochloric acid and water in a mass ratio of 60:30:2:8.

[0120] Embodiment 10: A preparation method of a homogeneous catalytic reaction system provided in the embodiment comprises:

[0121] Step a, tetraethylammonium nitrite, HI and water are added into a reaction container and mixed uniformly, heated to 30°C, and constant temperature stirring.

[0122] Step b, crystalline fructose is added into the above mixture, and continues to stir to form a uniform single-phase mixture.

[0123] The homogeneous catalytic reaction system contains quaternary ammonium salt, crystalline fructose, HI and water in a mass ratio of 70:20:2:10.

[0124] Embodiment 11: A preparation method of a homogeneous catalytic reaction system provided in the embodiment comprises:

[0125] Step a, tetraethylammonium fluoride, p-toluenesulfonic acid and water are added into a reaction container and mixed uniformly, heated to 40°C, and constant temperature stirring.

[0126] Step b, liquid fructose is added into the above mixture, and continues to stir to form a uniform single-phase mixture.

[0127] The homogeneous catalytic reaction system contains quaternary ammonium salt, liquid fructose, p-toluenesulfonic acid and water in a mass ratio of 80:25:1:8.

[0128] Embodiment 12: A preparation method of a homogeneous catalytic reaction system provided in the embodiment comprises:

[0129] Step a, choline bromide, dodecylbenzenesulfonic acid and water are added into a reaction container and mixed uniformly, heated to 40°C, and constant temperature stirring.

[0130] Step b, crystalline fructose is added into the above mixture, and continues to stir to form a uniform single-phase mixture.

[0131] The homogeneous catalytic reaction system contains quaternary ammonium salt, crystalline fructose, dodecylbenzenesulfonic acid and water in a mass ratio of 40:40:5:15.

[0132] Embodiment 13: A preparation method of a homogeneous catalytic reaction system provided in the embodiment comprises:

[0133] Step a, choline chloride, nitric acid and water are added into a reaction container and mixed uniformly, heated to 70°C, and constant temperature stirring.

[0134] Step b, crystalline fructose is added into the above mixture, and continues to stir to form a uniform single-phase mixture.

[0135] The homogeneous catalytic reaction system contains quaternary ammonium salt, crystalline fructose, nitric acid and water in a mass ratio of 60:30:3:7.

[0136] Embodiment 14: The embodiment provides a preparation method of a homogeneous catalytic reaction system, which comprises the following steps:

[0137] In step a, tetraethylammonium bromide, HBr and water are added into a reaction container and uniformly mixed, and then heated to 50 DEG C and stirred at constant temperature.

[0138] In step b, crystalline fructose is added into the mixture, and the stirring is continued to form a uniform single-phase mixture.

[0139] The homogeneous catalytic reaction system contains the quaternary ammonium salt, the crystalline fructose, the HBr and the water in a mass ratio of 55:30:5:10.

[0140] Embodiment 15: The embodiment provides a method for synthesizing 5-hydroxymethylfurfural, which comprises the following steps:

[0141] The homogeneous catalytic reaction system obtained in Embodiment 1 is transferred into a closed reaction container for reaction, the reaction pressure of the reaction system is adjusted to-0.09 MPa, the reaction temperature is 80 DEG C, the reaction time is 60 min, after the reaction is completed, the pressure of the reaction container is restored to normal pressure, water is added as a quenching agent to quench the reaction, the reaction mixture is analyzed by liquid chromatography, then 5-hydroxymethylfurfural is extracted by using ethyl acetate as an extractant and adopting cross-flow extraction, after the extraction is completed, the light phase and the heavy phase are separated, the extractant is separated and recovered by reduced pressure distillation from the light phase, 5-hydroxymethylfurfural is obtained, and the residual extractant and excess H2O are separated by reduced pressure distillation from the heavy phase, and the ion pair bound homogeneous catalytic system can be reused. In the above process, the mass ratio of the quenching agent to the reaction system is 2:1, and the mass ratio of the extractant to the total system after quenching is 4:1. The results show that in the embodiment, the fructose conversion rate is 99%, the yield of 5-hydroxymethylfurfural is 93%, and the purity is 99%. After the recycled ion pair bound homogeneous catalytic system is used for 30 times, the yield of 5-hydroxymethylfurfural still maintains 91%.

[0142] Embodiment 16: The embodiment provides a method for synthesizing 5-hydroxymethylfurfural, which comprises the following steps:

[0143] The homogeneous catalytic reaction system obtained in Example 2 was transferred to a closed reaction container for reaction, the reaction pressure of the reaction system was adjusted to -0.08 MPa, the reaction temperature was 120°C, the reaction time was 240 min, after the reaction was completed, the pressure of the reaction container was restored to normal pressure, water was added as a quenching agent to quench the reaction, the reaction mixture was analyzed by liquid chromatography, then n-hexane was used as an extractant to extract 5-hydroxymethylfurfural by cross-flow extraction, after the extraction was completed, the light phase and the heavy phase were separated; the light phase was separated and the extractant was recovered by vacuum distillation to obtain 5-hydroxymethylfurfural; the heavy phase was separated and the residual extractant and excess H2O were removed by vacuum distillation to obtain a reusable ion pair bound homogeneous catalytic system. The mass ratio of the quenching agent to the reaction system in the above process was 5:1, and the mass ratio of the extractant to the total system after quenching was 3:1. The results showed that in this example, the conversion rate of fructose was 99%, the yield of 5-hydroxymethylfurfural was 87%, and the purity was 99%. The yield of 5-hydroxymethylfurfural still maintained at 84% after the recycled ion pair bound homogeneous catalytic system was used for 30 times.

[0144] Example 17: A method for synthesizing 5-hydroxymethylfurfural provided in this example includes the following steps:

[0145] The homogeneous catalytic reaction system obtained in Example 3 was transferred to a closed reaction container for reaction, the reaction pressure of the reaction system was adjusted to -0.03 MPa, the reaction temperature was 120°C, the reaction time was 60 min, after the reaction was completed, the pressure of the reaction container was restored to normal pressure, water was added as a quenching agent to quench the reaction, the reaction mixture was analyzed by liquid chromatography, then cyclohexane was used as an extractant to extract 5-hydroxymethylfurfural by countercurrent extraction, after the extraction was completed, the light phase and the heavy phase were separated; the light phase was separated and the extractant was recovered by vacuum distillation to obtain 5-hydroxymethylfurfural; the heavy phase was separated and the residual extractant and excess H2O were removed by vacuum distillation to obtain a reusable ion pair bound homogeneous catalytic system. The mass ratio of the quenching agent to the reaction system in the above process was 1:1, and the mass ratio of the extractant to the total system after quenching was 2:1. The results showed that in this example, the conversion rate of fructose was 98%, the yield of 5-hydroxymethylfurfural was 91%, and the purity was 99%. The yield of 5-hydroxymethylfurfural still maintained at 87% after the recycled ion pair bound homogeneous catalytic system was used for 30 times.

[0146] Example 18: A method for synthesizing 5-hydroxymethylfurfural provided in this example includes the following steps:

[0147] The homogeneous catalytic reaction system obtained in Example 4 was transferred to a closed reaction container for reaction, the reaction pressure of the reaction system was adjusted to -0.08 MPa, the reaction temperature was 150°C, the reaction time was 45 min, after the reaction was completed, the pressure of the reaction container was restored to normal pressure, water was added as a quenching agent to quench the reaction, the reaction mixture was analyzed by liquid chromatography, then petroleum ether was used as an extractant to extract 5-hydroxymethylfurfural by countercurrent extraction, after the extraction was completed, the light phase and the heavy phase were separated; the light phase was separated and the extractant was recovered by vacuum distillation to obtain 5-hydroxymethylfurfural; the heavy phase was separated and the residual extractant and excess H2O were removed by vacuum distillation to obtain a reusable ion pair bound homogeneous catalytic system. The mass ratio of the quenching agent to the reaction system in the above process was 3:1, and the mass ratio of the extractant to the total system after quenching was 5:1. The results showed that in this example, the conversion rate of fructose was 99%, the yield of 5-hydroxymethylfurfural was 90%, and the purity was 98%. The yield of 5-hydroxymethylfurfural still maintained at 88% after the recycled ion pair bound homogeneous catalytic system was used for 30 times.

[0148] Example 19: A method for synthesizing 5-hydroxymethylfurfural provided in this example includes the following steps:

[0149] The homogeneous catalytic reaction system obtained in Example 5 was transferred to a closed reaction container for reaction, the reaction pressure of the reaction system was adjusted to -0.05 MPa, the reaction temperature was 200°C, the reaction time was 30 min, after the reaction was completed, the pressure of the reaction container was restored to normal pressure, water was added as a quenching agent to quench the reaction, the reaction mixture was analyzed by liquid chromatography, then diethyl ether was used as an extractant to extract 5-hydroxymethylfurfural by countercurrent extraction, after the extraction was completed, the light phase and the heavy phase were separated; the light phase was separated and the extractant was recovered by vacuum distillation to obtain 5-hydroxymethylfurfural; the heavy phase was separated and the residual extractant and excess H2O were removed by vacuum distillation to obtain a reusable ion pair bound homogeneous catalytic system. The mass ratio of the quenching agent to the reaction system in the above process was 1:1, and the mass ratio of the extractant to the total system after quenching was 1:1. The results showed that in this example, the conversion rate of fructose was 100%, the yield of 5-hydroxymethylfurfural was 86%, and the purity was 98%. The yield of 5-hydroxymethylfurfural still maintained at 84% after the recycled ion pair bound homogeneous catalytic system was used for 30 times.

[0150] Example 20: A method for synthesizing 5-hydroxymethylfurfural provided in this example includes the following steps:

[0151] The homogeneous catalytic reaction system obtained in Example 6 was transferred to a closed reaction container for reaction, the reaction pressure of the reaction system was adjusted to -0.05 MPa, the reaction temperature was 180°C, the reaction time was 20 min, after the reaction was completed, the pressure of the reaction container was restored to normal pressure, water was added as a quenching agent to quench the reaction, the reaction mixture was analyzed by liquid chromatography, then acetonitrile was used as an extractant to extract 5-hydroxymethylfurfural by countercurrent extraction, after the extraction was completed, the light phase and the heavy phase were separated; the light phase was separated and the extractant was recovered by vacuum distillation to obtain 5-hydroxymethylfurfural; the heavy phase was separated and the residual extractant and excess H2O were removed by vacuum distillation to obtain a reusable ion pair bound homogeneous catalytic system. The mass ratio of the quenching agent to the reaction system in the above process was 5:1, and the mass ratio of the extractant to the total system after quenching was 4:1. The results showed that the conversion rate of fructose in this example was 100%, the yield of 5-hydroxymethylfurfural was 87%, and the purity was 98%. The yield of 5-hydroxymethylfurfural still maintained at 83% after the recycled ion pair bound homogeneous catalytic system was used for 30 times.

[0152] Example 21: A method for synthesizing 5-hydroxymethylfurfural provided in this example includes the following steps:

[0153] The homogeneous catalytic reaction system obtained in Example 7 was transferred to a closed reaction container for reaction, the reaction pressure of the reaction system was adjusted to -0.08 MPa, the reaction temperature was 50°C, the reaction time was 240 min, after the reaction was completed, the pressure of the reaction container was restored to normal pressure, water was added as a quenching agent to quench the reaction, the reaction mixture was analyzed by liquid chromatography, then dichloromethane was used as an extractant to extract 5-hydroxymethylfurfural by single-stage extraction, after the extraction was completed, the light phase and the heavy phase were separated; the light phase was separated and the extractant was recovered by vacuum distillation to obtain 5-hydroxymethylfurfural; the heavy phase was separated and the residual extractant and excess H2O were removed by vacuum distillation to obtain a reusable ion pair bound homogeneous catalytic system. The mass ratio of the quenching agent to the reaction system in the above process was 4:1, and the mass ratio of the extractant to the total system after quenching was 3:1. The results showed that the conversion rate of fructose in this example was 98%, the yield of 5-hydroxymethylfurfural was 92%, and the purity was 98%. The yield of 5-hydroxymethylfurfural still maintained at 89% after the recycled ion pair bound homogeneous catalytic system was used for 30 times.

[0154] Example 22: A method for synthesizing 5-hydroxymethylfurfural provided in this example includes the following steps:

[0155] The homogeneous catalytic reaction system obtained in Example 8 was transferred to a closed reaction container for reaction, the reaction pressure of the reaction system was adjusted to -0.08 MPa, the reaction temperature was 80°C, the reaction time was 60 min, after the reaction was completed, the pressure of the reaction container was restored to normal pressure, water was added as a quenching agent to quench the reaction, the reaction mixture was analyzed by liquid chromatography, then tetrahydrofuran was used as an extractant, 5-hydroxymethylfurfural was extracted by countercurrent extraction, after the extraction was completed, the light phase and the heavy phase were separated; the light phase was separated and the extractant was recovered by reduced pressure distillation to obtain 5-hydroxymethylfurfural; the heavy phase was separated and the residual extractant and excess H2O were removed by reduced pressure distillation to obtain a reusable ion pair bound homogeneous catalytic system. The mass ratio of the quenching agent to the reaction system in the above process was 1:1, and the mass ratio of the extractant to the total system after quenching was 2:1. The results showed that in this example, the conversion rate of fructose was 99%, the yield of 5-hydroxymethylfurfural was 91%, and the purity was 99%. The yield of 5-hydroxymethylfurfural still maintained at 87% after the recycled ion pair bound homogeneous catalytic system was used for 30 times.

[0156] Example 23: A method for synthesizing 5-hydroxymethylfurfural provided in this example includes the following steps:

[0157] The homogeneous catalytic reaction system obtained in Example 9 was transferred to a closed reaction container for reaction, the reaction pressure of the reaction system was adjusted to -0.09 MPa, the reaction temperature was 200°C, the reaction time was 5 min, after the reaction was completed, the pressure of the reaction container was restored to normal pressure, water was added as a quenching agent to quench the reaction, the reaction mixture was analyzed by liquid chromatography, then n-hexane was used as an extractant, 5-hydroxymethylfurfural was extracted by cross-flow extraction, after the extraction was completed, the light phase and the heavy phase were separated; the light phase was separated and the extractant was recovered by reduced pressure distillation to obtain 5-hydroxymethylfurfural; the heavy phase was separated and the residual extractant and excess H2O were removed by reduced pressure distillation to obtain a reusable ion pair bound homogeneous catalytic system. The mass ratio of the quenching agent to the reaction system in the above process was 3:1, and the mass ratio of the extractant to the total system after quenching was 4:1. The results showed that in this example, the conversion rate of fructose was 100%, the yield of 5-hydroxymethylfurfural was 87%, and the purity was 98%. The yield of 5-hydroxymethylfurfural still maintained at 85% after the recycled ion pair bound homogeneous catalytic system was used for 30 times.

[0158] Example 24: A method for synthesizing 5-hydroxymethylfurfural provided in this example includes the following steps:

[0159] The homogeneous catalytic reaction system obtained in Example 10 was transferred to a closed reaction container for reaction, the reaction pressure of the reaction system was adjusted to -0.1 MPa, the reaction temperature was 120°C, the reaction time was 30 min, after the reaction was completed, the pressure of the reaction container was restored to normal pressure, water was added as a quenching agent to quench the reaction, the reaction mixture was analyzed by liquid chromatography, then n-hexane was used as an extractant, 5-hydroxymethylfurfural was extracted by cross-flow extraction, after the extraction was completed, the light phase and the heavy phase were separated; the light phase was separated and the extractant was recovered by vacuum distillation, and 5-hydroxymethylfurfural was obtained; the heavy phase was separated and the residual extractant and excess H2O were removed by vacuum distillation, and the reusable ion pair bound homogeneous catalytic system was obtained. The mass ratio of the quenching agent to the reaction system in the above process was 1:1, and the mass ratio of the extractant to the total system after quenching was 2:1. The results showed that in this example, the conversion rate of fructose was 99%, the yield of 5-hydroxymethylfurfural was 90%, and the purity was 99%. The yield of 5-hydroxymethylfurfural still maintained at 87% after the recycled ion pair bound homogeneous catalytic system was used for 30 times.

[0160] Example 25: A method for synthesizing 5-hydroxymethylfurfural provided in this example includes the following steps:

[0161] The homogeneous catalytic reaction system obtained in Example 11 was transferred to a closed reaction container for reaction, the reaction pressure of the reaction system was adjusted to -0.015 MPa, the reaction temperature was 100°C, the reaction time was 180 min, after the reaction was completed, the pressure of the reaction container was restored to normal pressure, water was added as a quenching agent to quench the reaction, the reaction mixture was analyzed by liquid chromatography, then ethyl acetate was used as an extractant, 5-hydroxymethylfurfural was extracted by single-stage extraction, after the extraction was completed, the light phase and the heavy phase were separated; the light phase was separated and the extractant was recovered by vacuum distillation, and 5-hydroxymethylfurfural was obtained; the heavy phase was separated and the residual extractant and excess H2O were removed by vacuum distillation, and the reusable ion pair bound homogeneous catalytic system was obtained. The mass ratio of the quenching agent to the reaction system in the above process was 1:1, and the mass ratio of the extractant to the total system after quenching was 1:1. The results showed that in this example, the conversion rate of fructose was 99%, the yield of 5-hydroxymethylfurfural was 85%, and the purity was 99%. The yield of 5-hydroxymethylfurfural still maintained at 82% after the recycled ion pair bound homogeneous catalytic system was used for 30 times.

[0162] Example 26: A method for synthesizing 5-hydroxymethylfurfural provided in this example includes the following steps:

[0163] The homogeneous catalytic reaction system obtained in Example 12 was transferred to a closed reaction container for reaction, the reaction pressure of the reaction system was adjusted to -0.08 MPa, the reaction temperature was 100°C, the reaction time was 60 min, after the reaction was completed, the pressure of the reaction container was restored to normal pressure, water was added as a quenching agent to quench the reaction, the reaction mixture was analyzed by liquid chromatography, then tetrahydrofuran was used as an extractant, 5-hydroxymethylfurfural was extracted by cross-flow extraction, after the extraction was completed, the light phase and the heavy phase were separated; the light phase was separated and the extractant was recovered by reduced pressure distillation to obtain 5-hydroxymethylfurfural; the heavy phase was separated and the residual extractant and excess H2O were removed by reduced pressure distillation to obtain a reusable ion pair bound homogeneous catalytic system. The mass ratio of the quenching agent to the reaction system in the above process was 3:1, and the mass ratio of the extractant to the total system after quenching was 4:1. The results showed that in this example, the conversion rate of fructose was 99%, the yield of 5-hydroxymethylfurfural was 90%, and the purity was 98%. The yield of 5-hydroxymethylfurfural remained at 87% after the recovered ion pair bound homogeneous catalytic system was recycled for 30 times.

[0164] Example 27: A method for synthesizing 5-hydroxymethylfurfural provided in this example includes the following steps:

[0165] The homogeneous catalytic reaction system obtained in Example 13 was transferred to a closed reaction container for reaction, the reaction pressure of the reaction system was adjusted to -0.05 MPa, the reaction temperature was 100°C, the reaction time was 120 min, after the reaction was completed, the pressure of the reaction container was restored to normal pressure, water was added as a quenching agent to quench the reaction, the reaction mixture was analyzed by liquid chromatography, then cyclohexane was used as an extractant, 5-hydroxymethylfurfural was extracted by countercurrent extraction, after the extraction was completed, the light phase and the heavy phase were separated; the light phase was separated and the extractant was recovered by reduced pressure distillation to obtain 5-hydroxymethylfurfural; the heavy phase was separated and the residual extractant and excess H2O were removed by reduced pressure distillation to obtain a reusable ion pair bound homogeneous catalytic system. The mass ratio of the quenching agent to the reaction system in the above process was 4:1, and the mass ratio of the extractant to the total system after quenching was 5:1. The results showed that in this example, the conversion rate of fructose was 99%, the yield of 5-hydroxymethylfurfural was 89%, and the purity was 99%. The yield of 5-hydroxymethylfurfural remained at 86% after the recovered ion pair bound homogeneous catalytic system was recycled for 30 times.

[0166] Example 28: A method for synthesizing 5-hydroxymethylfurfural provided in this example includes the following steps:

[0167] The homogeneous catalytic reaction system obtained in Example 14 was transferred to a closed reaction vessel for reaction, the reaction pressure of the reaction system was adjusted to -0.09 MPa, the reaction temperature was 120°C, the reaction time was 60 min, after the reaction was completed, the pressure of the reaction vessel was restored to normal pressure, water was added as a quenching agent to quench the reaction, the reaction mixture was analyzed by liquid chromatography, then tetrahydrofuran was used as an extractant, countercurrent extraction was used to extract 5-hydroxymethylfurfural, after the extraction was completed, the light phase and the heavy phase were separated; the light phase was separated and recovered by vacuum distillation to separate the extractant, and 5-hydroxymethylfurfural was obtained; the heavy phase was separated by vacuum distillation to separate the residual extractant and excess H2O, and a reusable ion pair bound homogeneous catalytic system was obtained. The mass ratio of the quenching agent to the reaction system in the above process was 3:1, and the mass ratio of the extractant to the total system after quenching was 3:1. The results show that in this example, the conversion rate of fructose is 99%, the yield of 5-hydroxymethylfurfural is 91%, and the purity is 99%. The recycled ion pair bound homogeneous catalytic system is recycled for 30 times, and the yield of 5-hydroxymethylfurfural still maintains 88%.

[0168] Comparative Example 1: The method for synthesizing 5-hydroxymethylfurfural provided in this comparative example is basically the same as that in Example 15, the difference is only in the composition of the catalytic reaction system. Specifically, in this comparative example, the methanesulfonic acid in the homogeneous catalytic reaction system in Example 15 is replaced with an equal amount of a heterogeneous sulfonic acid resin (Amberlyst-15). The results show that the recycling effect of the catalyst system in this comparative example is not ideal, and after three recycles, the conversion rate of fructose decreases from the initial 85% to 27%.

[0169] Comparative Example 2: The method for synthesizing 5-hydroxymethylfurfural provided in this comparative example is basically the same as that in Example 15, the difference is only in the composition of the catalytic reaction system. Specifically, in this comparative example, the tetraethylammonium bromide in the homogeneous catalytic reaction system in Example 15 is replaced with an equal amount of DMSO. The results show that the conversion rate of fructose in this comparative example is 99%, and the yield of 5-hydroxymethylfurfural before separation is 85%. The separation of 5-hydroxymethylfurfural cannot be directly extracted, but needs to use vacuum distillation to remove water and DMSO. Due to the high temperature damage to 5-hydroxymethylfurfural, the yield of 5-hydroxymethylfurfural after separation is 71%, and the homogeneous acid cannot be recovered.

[0170] Comparative Example 3: The method for synthesizing 5-hydroxymethylfurfural provided in this comparative example is basically the same as that in Example 15, the difference is only in the composition of the catalytic reaction system. Specifically, in this comparative example, the tetraethylammonium bromide in the homogeneous catalytic reaction system in Example 15 is replaced with an equal amount of water (9wt% of the total mass of the reaction system). The results show that the conversion rate of fructose in this comparative example is 99%, and the yield of 5-hydroxymethylfurfural is only 24%.

[0171] Comparative Example 4: The method for synthesizing 5-hydroxymethylfurfural provided in this comparative example is substantially identical to that of Example 15, except that the composition of the catalytic reaction system is different. Specifically, in this comparative example, the fructose in the homogeneous catalytic reaction system of Example 15 is replaced with an equal amount of glucose (30 wt% of the total mass of the reaction system). The results show that the conversion rate of glucose in this comparative example is only 72%, and the yield of 5-hydroxymethylfurfural is 27%.

[0172] Comparative Example 5: The method for synthesizing 5-hydroxymethylfurfural provided in this comparative example is substantially identical to that of Example 15, except that the reaction pressure and reaction time are different. Specifically, in this comparative example, the reaction pressure is set to atmospheric pressure, and the reaction time is increased to 120 min. The results show that the conversion rate of fructose in this comparative example is 92%, and the yield of 5-hydroxymethylfurfural is 85%.

[0173] Comparative Example 6: The method for synthesizing 5-hydroxymethylfurfural provided in this comparative example is substantially identical to that of Example 15, except that no quenching agent is used, and the reaction system is naturally cooled after the reaction is completed. The results show that the conversion rate of fructose in this comparative example is 99%, and the yield of 5-hydroxymethylfurfural is 72%.

[0174] Comparative Example 7: The method for synthesizing 5-hydroxymethylfurfural provided in this comparative example is substantially identical to that of Example 15, except that no quenching agent is used, and the reaction system is forcibly convection-cooled after the reaction is completed. The results show that the conversion rate of fructose in this comparative example is 99%, and the yield of 5-hydroxymethylfurfural is 85%.

[0175] Comparative Example 8: The method for synthesizing 5-hydroxymethylfurfural provided in this comparative example is substantially identical to that of Example 15, except that in the preparation of the homogeneous catalytic reaction system, instead of first mixing tetraethylammonium bromide, methanesulfonic acid, and water uniformly and then adding fructose, tetraethylammonium bromide, methanesulfonic acid, water, and fructose are directly mixed. The results show that the conversion rate of fructose in this comparative example is 89%, and the yield of 5-hydroxymethylfurfural is 78%.

[0176] Comparative Example 9: The method for synthesizing 5-hydroxymethylfurfural provided in this comparative example is substantially identical to that of Example 15, except that the dehydration reaction is carried out under atmospheric pressure, and the reaction time is 180 min. After the reaction is completed, the quenching agent is quenched and extracted with ethyl acetate in the same manner as in Example 15. The results show that the conversion rate of fructose in this comparative example is 96%, the yield of 5-hydroxymethylfurfural is 85%, and the purity is 99%. However, the recycling effect of the catalyst system in this comparative example is not ideal, and after three cycles, the yield of 5-hydroxymethylfurfural is reduced to 57%.

[0177] It should be noted that each of the technical features described in the above embodiments can be combined in any manner, without contradiction, and the various possible combinations are not described again in the present application to avoid unnecessary repetition.

[0178] Furthermore, any combination of the various embodiments of the present application can also be made, as long as it does not deviate from the idea of the present application, and it should also be considered as disclosed in the present application.

Claims

1. An ion pair bound homogeneous catalytic system, characterized in that, The homogeneous acid comprises HF, HCl, HBr, HI, H2SO4, HNO3, trifluoromethanesulfonic acid, benzene sulfonic acid, methanesulfonic acid, p-toluene sulfonic acid or dodecyl benzene sulfonic acid.

2. The ion pair bound homogeneous catalytic system according to claim 1, characterized in that: The chemical formula of the quaternary ammonium salt is R4NX, wherein the hydrocarbon radical R comprises substituted and / or unsubstituted alkyl and / or aryl groups, and X comprises F - , Cl - , Br - , I - , NO2 - , NO3 - , or SO4 2- .

3. The ion pair bound homogeneous catalytic system according to claim 1, characterized in that: The homogeneous acid comprises HF, HCl, HBr, HI, H2SO4, HNO3, trifluoromethanesulfonic acid, benzene sulfonic acid, methanesulfonic acid, p-toluene sulfonic acid or dodecyl benzene sulfonic acid.

4. The ion pair bound homogeneous catalytic system according to claim 3, characterized in that: The homogeneous acid is selected from HCl, HBr, methanesulfonic acid or H2SO4.

5. A method of synthesizing 5-hydroxymethylfurfural, characterized by, The homogeneous acid comprises HF, HCl, HBr, HI, H2SO4, HNO3, trifluoromethanesulfonic acid, benzene sulfonic acid, methanesulfonic acid, p-toluene sulfonic acid or dodecyl benzene sulfonic acid. The ion pair bound homogeneous catalytic system comprises a quaternary ammonium salt, a homogeneous acid and water; The ion pair bound homogeneous catalytic system comprises a quaternary ammonium salt, a homogeneous acid and water; The ion pair bound homogeneous catalytic system comprises a quaternary ammonium salt, a homogeneous acid and water; 6. The method of claim 5, wherein: The ion pair bound homogeneous catalytic system comprises a quaternary ammonium salt, a homogeneous acid and water; and / or the chemical formula of the quaternary ammonium salt is R4NX, wherein the hydrocarbon group R comprises substituted and / or unsubstituted alkyl and / or aryl groups and X comprises F - , Cl - , Br - , I - , NO2 - , NO3 - or SO4 2- ; The ion pair bound homogeneous catalytic system comprises a quaternary ammonium salt, a homogeneous acid and water; The ion pair bound homogeneous catalytic system comprises a quaternary ammonium salt, a homogeneous acid and water; The ion pair bound homogeneous catalytic system comprises a quaternary ammonium salt, a homogeneous acid and water; 7. The method of claim 6, wherein: The ion pair bound homogeneous catalytic system comprises a quaternary ammonium salt, a homogeneous acid and water; The ion pair bound homogeneous catalytic system comprises a quaternary ammonium salt, a homogeneous acid and water; 8. The method of claim 7, wherein: The ion pair bound homogeneous catalytic system comprises a quaternary ammonium salt, a homogeneous acid and water; 9. The method of claim 5, wherein, The ion pair bound homogeneous catalytic system comprises a quaternary ammonium salt, a homogeneous acid and water; The ion pair bound homogeneous catalytic system comprises a quaternary ammonium salt, a homogeneous acid and water; 10. The method of claim 5, wherein: The ion pair bound homogeneous catalytic system comprises a quaternary ammonium salt, a homogeneous acid and water; 11. The method of claim 10, wherein: The ion pair bound homogeneous catalytic system comprises a quaternary ammonium salt, a homogeneous acid and water; 12. The method of claim 11, wherein: The ion pair bound homogeneous catalytic system comprises a quaternary ammonium salt, a homogeneous acid and water; 13. The method of claim 5, wherein, The ion pair bound homogeneous catalytic system comprises a quaternary ammonium salt, a homogeneous acid and water; The ion pair bound homogeneous catalytic system comprises a quaternary ammonium salt, a homogeneous acid and water; The ion pair bound homogeneous catalytic system comprises a quaternary ammonium salt, a homogeneous acid and water; 14. 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The ion pair bound homogeneous catalytic system comprises a quaternary ammonium salt, a homogeneous acid and water; The ion pair bound homogeneous catalytic system comprises a quaternary ammonium salt, a homogeneous acid and water; The ion pair bound homogeneous catalytic system comprises a quaternary ammonium salt, a homogeneous acid and water; The ion pair bound homogeneous catalytic system comprises a quaternary ammonium salt, a homogeneous acid and water; The ion pair bound homogeneous catalytic system comprises a quaternary ammonium salt, a homogeneous acid and water; The ion pair bound homogeneous catalytic system comprises a quaternary ammonium salt, a homogeneous acid and water; The ion pair bound homogeneous catalytic system comprises a quaternary ammonium salt, a homogeneous acid and water; The ion pair bound homogeneous catalytic system comprises a quaternary ammonium salt, a homogeneous acid and water; The ion pair bound homogeneous catalytic system comprises a quaternary ammonium salt, a homogeneous acid and water; The ion pair bound homogeneous catalytic system comprises a quaternary ammonium salt, a homogeneous acid and water; The ion pair bound homogeneous catalytic system comprises a quaternary ammonium salt, a homogeneous acid and water; The ion pair bound homogeneous catalytic system comprises a quaternary ammonium salt, a homogeneous acid and water; The ion pair bound homogeneous catalytic system comprises a quaternary ammonium salt, a homogeneous acid and water; The ion pair bound homogeneous catalytic system comprises a quaternary ammonium salt, a homogeneous acid and water; The ion pair bound homogeneous catalytic system comprises a quaternary ammonium salt, a homogeneous acid and water; The ion pair bound homogeneous catalytic system comprises a quaternary ammonium salt, a homogeneous acid and water; The ion pair bound homogeneous catalytic system comprises a quaternary ammonium salt, a homogeneous separating 5-hydroxymethylfurfural from the light phase; and, separating the ion-pair bound homogeneous catalytic system from the heavy phase.

15. The method of claim 14, wherein: The extractant comprises an organic solvent, which comprises a combination of one or more of petroleum ether, cyclohexane, n-hexane, diethyl ether, ethyl acetate, acetonitrile, dichloroethane, and tetrahydrofuran; and / or, the extractant is added in an amount of 1-5 times the mass of the reaction mixture; and / or, the extractive treatment is performed by any one of single-stage extraction, multi-stage countercurrent extraction, or multi-stage crossflow extraction.

16. The method of claim 14, wherein, comprising: recovery of the extractant from the light phase by means of reduced pressure distillation, and obtaining 5-hydroxymethylfurfural; and / or, separation of the extractant and part of the water from the heavy phase by means of reduced pressure distillation, thereby recovering the ion-pair bound homogeneous catalytic system.

17. The method of claim 16, wherein, further comprising: mixing the recovered ion-pair bound homogeneous catalytic system with fructose to form a homogeneous catalytic reaction system, and performing the reaction again.