Method for preparing 5-hydroxymethylfurfural

Abstract

The invention relates to the field of catalytic chemistry, and discloses a method for preparing 5-hydroxymethylfurfural, which comprises the following steps: mixing organic quaternary ammonium salt, water, a catalyst, fructosyl carbohydrate and an organic solvent, and then carrying out dehydration reaction to obtain the 5-hydroxymethylfurfural. According to the method, the organic quaternary ammonium salt with a specific structure is added into the fructose-based carbohydrate, and in the dehydration reaction process of the fructose-based carbohydrate, the organic quaternary ammonium salt realizes in-situ extraction of impurities in a reaction system, so that the high-purity 5-hydroxymethylfurfural product is prepared.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of catalytic chemistry, in particular to a method for preparing 5-hydroxymethyl furfural. BACKGROUND

[0002] 5-hydroxymethyl furfural (HMF) is a multifunctional molecule with aromatic five-ring system, aldehyde and alcohol groups, which is a biomass-based platform molecule with high added value. Through its aldehyde group, hydroxyl group and carbon-carbon double bond active group, it can undergo hydrogenation, oxidative dehydrogenation, esterification, halogenation, polymerization and hydrolysis reactions, and be used to synthesize important materials such as polymers, drugs, resins, plastics and fuel additives. Therefore, HMF is considered as an important bridge for the transition from fossil energy economy to sustainable energy economy.

[0003] In the related art, fructose, water, acid catalyst and at least one other solvent are mixed in a reaction zone to undergo a dehydration reaction to form HMF; and humin is the main by-product in the dehydration reaction, which has good solubility in the reaction solvent and is difficult to separate from the reaction solvent and the target product; resulting in low purity of the HMF product.

[0004] To further improve the purity of the HMF product, the following methods are often used to separate humin in the related art: membrane separation and activated carbon adsorption separation. The membrane separation process is easy to block, and the membrane material needs to be frequently treated or replaced, which is high in cost. Although activated carbon can effectively adsorb humin, it will also adsorb the target product HMF in the solvent, resulting in yield loss, which is not worth the cost. In addition, humin is also easy to block the pore structure of activated carbon, causing the adsorption performance of activated carbon to decrease, and frequent regeneration of activated carbon is required, which increases energy consumption and complicates the process. SUMMARY

[0005] The purpose of the present application is to overcome the problem of low purity of directly prepared 5-hydroxymethyl furfural in the prior art, and to provide a method for preparing 5-hydroxymethyl furfural, which directly prepares high-purity 5-hydroxymethyl furfural by selecting a specific structure of organic quaternary ammonium salt to control the reaction medium of the dehydration reaction system.

[0006] To achieve the above purpose, the present application provides a method for preparing 5-hydroxymethyl furfural, comprising the following steps:

[0007] mixing the organic quaternary ammonium salt, water, catalyst, fructose-based carbohydrate and organic solvent to perform a dehydration reaction to prepare 5-hydroxymethyl furfural;

[0008] The structure of the organic quaternary ammonium salt is as shown in the following formula:

[0009]

[0010] wherein R1, R2, R3 and R4 are each independently selected from one of alkyl and epoxy group;

[0011] at least one of R1, R2, R3 and R4 is an epoxy group;

[0012] the alkyl group comprises C1-C4 alkyl group;

[0013] the epoxy group comprises C2-C4 epoxy group;

[0014] X - is halide ion.

[0015] Preferably, the alkyl group comprises one of methyl, ethyl, 1-propyl, 2-propyl, 1-butyl, 2-butyl, 2-methyl-1-propyl and 2-methyl-2-propyl.

[0016] Preferably, the epoxy group comprises one of epoxy ethyl, 2,3-epoxy propyl and epoxy butyl.

[0017] Preferably, the halide ion comprises one of fluoride ion, chloride ion, bromide ion and iodide ion.

[0018] Preferably, the organic quaternary ammonium salt is 2,3-epoxy propyl trimethyl ammonium chloride.

[0019] Preferably, the organic solvent comprises at least one of acetone, butanone, methyl isobutyl ketone, 1,4-dioxane, tetrahydrofuran and acetonitrile.

[0020] According to one of the embodiments of the present application, at least the following advantages are achieved:

[0021] The present application adds the organic quaternary ammonium salt with specific structure into fructosyl carbohydrate, and the organic quaternary ammonium salt realizes in-situ extraction of impurities in the reaction system during the dehydration reaction of fructosyl carbohydrate, thereby obtaining high-purity 5-hydroxymethyl furfural product (purity between 95% and 99.9%).

[0022] The epoxy group structure exists in the organic quaternary ammonium salt in the present application, thereby controlling the purity of 5-hydroxymethyl furfural product. The preparation method of the present application only needs to add the organic quaternary ammonium salt with specific structure into the dehydration reaction system of fructosyl carbohydrate, without increasing the complex post-treatment process and without increasing the process complexity; that is, the preparation method of the present application is simple in operation and high-purity 5-hydroxymethyl furfural product is obtained. BRIEF DESCRIPTION OF DRAWINGS

[0023] In order to more clearly illustrate the technical solutions of the embodiments or the prior art, the drawings needed in the following embodiment or prior art description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the drawings, and those skilled in the art can also obtain other drawings according to the structures shown in the drawings without any creative effort.

[0024] Figure 1 is a liquid chromatography detection result of 5-hydroxymethylfurfural prepared in Example 1;

[0025] Figure 2 is a picture of the appearance of the reaction system after the reaction of Example 1;

[0026] Figure 3 is a picture of the appearance of the reaction system after the reaction of Comparative Example 1. DETAILED DESCRIPTION

[0027] Hereinafter, the embodiments of the technical solutions of the present application will be described in detail. However, there will be cases where unnecessary detailed descriptions are omitted. For example, there will be cases where detailed descriptions of matters known to those skilled in the art, repeated descriptions of substantially identical structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. In addition, the following description is provided in order for those skilled in the art to fully understand the present application, and is not intended to limit the subject matter recited in the claims.

[0028] The "range" disclosed in the present application is defined in the form of lower limit and upper limit, a given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of a particular range. The range defined in this way can include or not include the end value, and can be arbitrarily combined, i.e. any lower limit can be combined with any upper limit to form a range. For example, if the ranges of 60-120 and 80-110 are listed for a particular parameter, it is understood that the ranges of 60-110 and 80-120 are also contemplated. In addition, if the minimum range values of 1 and 2 are listed, and if the maximum range values of 3, 4 and 5 are listed, the following ranges are all contemplated: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In the present application, unless otherwise specified, the numerical range "a-b" represents a shorthand notation for any real number combination between a and b, where a and b are both real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" have been listed herein, and "0-5" is only a shorthand notation for these numerical combinations. In addition, when a parameter is expressed as ≥2 integers, it is equivalent to disclose that the parameter is, for example, integer 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0029] All embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions if no special instructions are given.

[0030] All technical features and optional technical features of the present application can be combined with each other to form new technical solutions if no special instructions are given.

[0031] All steps of the present application can be performed in sequence or randomly if no special instructions are given, and preferably are performed in sequence. For example, the method comprises steps (a) and (b), which means that the method can comprise steps (a) and (b) performed in sequence, or steps (b) and (a) performed in sequence. For example, the method mentioned can further comprise step (c), which means that step (c) can be added to the method in any order, for example, the method can comprise steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0032] If no special instructions are given, the "including" and "containing" mentioned in the present application means open type, and can also be closed type. For example, the "including" and "containing" can mean that other components not listed can also be included or contained, or only the listed components can be included or contained.

[0033] If no special instructions are given, in the present application, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, any one of the following conditions satisfies the condition "A or B": A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or A and B are both true (or exist).

[0034] 5-hydroxymethylfurfural is synthesized by dehydration of fructose or glucose catalyzed by liquid acid such as inorganic acid. However, 5-hydroxymethylfurfural will not only hydrate and decompose and condense under the action of inorganic acid, but also increase the by-products and reduce the selectivity of the product, thereby resulting in low purity of 5-hydroxymethylfurfural product.

[0035] In view of this, a method for preparing 5-hydroxymethylfurfural is disclosed in the present application, comprising the following steps:

[0036] The organic quaternary ammonium salt, water, catalyst, fructose-based carbohydrate and organic solvent are mixed and then subjected to a dehydration reaction to prepare 5-hydroxymethylfurfural;

[0037] The structure of the organic quaternary ammonium salt is shown in the following formula:

[0038]

[0039] R1, R2, R3 and R4 are independently selected from one of alkyl and epoxy group;

[0040] R1, R2, R3 and R4 are independently selected from one of alkyl and epoxy group;

[0041] The alkyl includes C1-C4 alkyl.

[0042] The epoxy group includes C2-C4 epoxy group.

[0043] X - is halogen ion.

[0044] According to one of the technical solutions in the embodiments of the present application, at least the following beneficial effects are achieved:

[0045] The organic quaternary ammonium salt, water and catalyst are mixed to form a reaction phase, and after the fructosyl carbohydrate and the reaction phase are mixed, intramolecular dehydration reaction is carried out under the action of the catalyst to obtain the 5-hydroxymethylfurfural product.

[0046] In the present application, the organic quaternary ammonium salt with specific structure is added to the fructosyl carbohydrate, and during the dehydration reaction of the fructosyl carbohydrate, the organic quaternary ammonium salt realizes in-situ extraction of impurities in the reaction system by improving the similar solubility with the impurities, and the 5-hydroxymethylfurfural is retained in the organic solvent, so that the separation of the impurities and the 5-hydroxymethylfurfural is realized, thereby obtaining the 5-hydroxymethylfurfural product with high purity (the purity is between 95% and 99.9%).

[0047] In the present application, the epoxy group structure exists in the organic quaternary ammonium salt, so that the purity of the 5-hydroxymethylfurfural product is controlled. The preparation method of the present application only needs to add the organic quaternary ammonium salt with specific structure to the dehydration reaction system of the fructosyl carbohydrate, does not need to increase the complex post-treatment process, and will not increase the process complexity; that is, the preparation method of the present application is simple in operation and the 5-hydroxymethylfurfural product with high purity is obtained.

[0048] According to some embodiments of the present application, the alkyl includes C1-C4 alkyl.

[0049] According to some embodiments of the present application, the alkyl includes one of methyl, ethyl, 1-propyl, 2-propyl, 1-butyl, 2-butyl, 2-methyl-1-propyl and 2-methyl-2-propyl.

[0050] In the present application, the length of the alkyl is controlled, which is conducive to reducing the cost of the organic quaternary ammonium salt compound.

[0051] According to some embodiments of the present application, the epoxy group includes C2-C4 epoxy group.

[0052] According to some embodiments of the present application, the epoxy group comprises one of an epoxyethyl group, a 2,3-epoxypropyl group and an epoxybutyl group.

[0053] According to some embodiments of the present application, the epoxy group comprises a 2,3-epoxypropyl group.

[0054] According to some embodiments of the present application, the halide ion comprises one of a fluoride ion, a chloride ion, a bromide ion and an iodide ion.

[0055] According to some embodiments of the present application, the halide ion is a chloride ion.

[0056] According to some embodiments of the present application, by controlling the halide ion, the solubility of the organic quaternary ammonium salt is controlled, and the reaction system is further controlled.

[0057] According to some embodiments of the present application, the organic quaternary ammonium salt comprises a 2,3-epoxypropyl trimethylammonium chloride.

[0058] The structural formula of the 2,3-epoxypropyl trimethylammonium chloride is as follows:

[0059]

[0060] The 2,3-epoxypropyl trimethylammonium chloride contains oxygen in the ring structure, which is beneficial to improve the purity of the 5-hydroxymethylfurfural product.

[0061] According to some embodiments of the present application, the catalyst comprises a sulfonic acid catalyst.

[0062] According to some embodiments of the present application, the sulfonic acid catalyst comprises at least one of sulfuric acid, methylsulfonic acid, ethylsulfonic acid and benzenesulfonic acid.

[0063] According to some embodiments of the present application, the sulfonic acid catalyst comprises sulfuric acid and / or methylsulfonic acid.

[0064] According to some embodiments of the present application, the water and the catalyst are first formed into a catalyst solution, and then mixed with the organic quaternary ammonium salt.

[0065] According to some embodiments of the present application, the content of the catalyst is 1wt% to 20wt%, for example, any value in the range consisting of 1wt%, 2wt%, 4wt%, 6wt%, 8wt%, 10wt%, 12wt%, 14wt%, 16wt%, 18wt%, 20wt% and any two values.

[0066] According to some embodiments of the present application, the content of the organic quaternary ammonium salt is 60wt%-75wt%, for example, 60wt%, 62wt%, 64wt%, 67wt%, 70wt%, 72wt%, 74wt%, 75wt%, and any value in the range between any two of the values.

[0067] The organic quaternary ammonium salt is used to construct the reaction phase, thus, the upper limit of the amount of the organic quaternary ammonium salt is determined by its solubility; to avoid the generation of unsoluble organic quaternary ammonium salt which cannot completely form a solution with water.

[0068] According to some embodiments of the present application, the organic solvent comprises at least one of acetone, butanone, methyl isobutyl ketone, 1,4-dioxane, tetrahydrofuran and acetonitrile.

[0069] According to some embodiments of the present application, the organic solvent comprises 1,4-dioxane.

[0070] According to some embodiments of the present application, the content of the reaction phase is 10wt%-20wt%, for example, 10wt%, 12wt%, 14wt%, 16wt%, 18wt%, 20wt%, and any value in the range between any two of the values, based on the total amount of the reaction phase and the extraction phase, wherein the reaction phase comprises the organic quaternary ammonium salt, water and the catalyst, and the extraction phase comprises the organic solvent.

[0071] The selected organic solvent in the present application has good solubility in water, thus, can only form a single liquid phase reaction system with water; and the selected organic quaternary ammonium salt in the present application provides salting-out effect, reduces the mutual solubility of water and the organic solvent, forms the required double liquid phase reaction system (reaction phase + extraction phase) in the present application, i.e., the organic solvent is the extraction phase, and realizes in-situ extraction of 5-hydroxymethylfurfural.

[0072] According to some embodiments of the present application, the temperature of the dehydration reaction is 80℃-200℃.

[0073] According to some embodiments of the present application, the temperature of the dehydration reaction is 110℃-140℃.

[0074] According to some embodiments of the present application, the temperature of the dehydration reaction is 110℃-130℃.

[0075] If the temperature is too low, the rate of the dehydration reaction is too slow; if the temperature is too high, the production cost is increased, thus, controlling the temperature within a certain range is beneficial to taking into account the reaction rate and the production cost.

[0076] According to some embodiments of the present application, the time of the dehydration reaction is 0.2h-1h.

[0077] The reaction time will depend on the reaction temperature, and lower reaction temperatures will generally result in longer reaction times.

[0078] According to some embodiments of the present application, the fructose-based carbohydrates account for 1% to 50% of the total mass of the reaction phase and the extraction phase.

[0079] According to some embodiments of the present application, the fructose-based carbohydrates account for 1% to 30% of the total mass of the reaction phase and the extraction phase.

[0080] According to some embodiments of the present application, the fructose-based carbohydrates account for 4% to 10% of the total mass of the reaction phase and the extraction phase.

[0081] If the content of the fructose-based carbohydrates is too low, the economic efficiency of the preparation method will be poor; and if the mass fraction is too high, the reaction difficulty will be increased.

[0082] According to some embodiments of the present application, the fructose-based carbohydrates include at least one of crude fructose, purified fructose, polyfructose and fructose syrup.

[0083] The crude fructose and the purified fructose are products in the industrial fructose production process.

[0084] The polyfructose is formed by connecting α-fructose with β-1, 2 glycosidic bond, and connecting a glucose residue at the end thereof, and has a molecular formula of (C6H 12 O6)-(C6H 10 O5)n (n = 2-60), an average polymerization degree ≥ 23, and a relative molecular mass of 344-11400.

[0085] The fructose syrup contains fructose and is commonly used for the production of 5-hydroxymethylfurfural.

[0086] According to some embodiments of the present application, the phase separation is performed after the dehydration reaction is completed, to obtain a dehydration reaction phase and an extraction phase.

[0087] The organic solvent in the extraction phase is then removed to obtain a 5-hydroxymethylfurfural product.

[0088] According to some embodiments of the present application, the reactor selected for the dehydration reaction can be a thick-walled pressure-resistant bottle, a stainless steel reaction kettle with a polytetrafluoroethylene lining, and a reactor that can be easily thought of by those skilled in the art.

[0089] According to some embodiments of the present application, the reactor is a thick-walled pressure-resistant bottle.

[0090] The thick-walled pressure-resistant bottle is beneficial for observing the phase interface between the reaction phase and the extraction phase and further beneficial for the phase separation operation.

[0091] According to some embodiments of the present application, the stirring is performed during the dehydration reaction.

[0092] According to some embodiments of the present application, the stirring rate is 500 r / min to 1000 r / min.

[0093] According to some embodiments of the present application, the stirring rate is 500 r / min to 600 r / min.

[0094] According to some embodiments of the present application, the stirring is stopped after the dehydration reaction, and the reaction system is divided into two phases, the upper phase is the extraction phase (5-hydroxymethylfurfural phase) containing the product 5-hydroxymethylfurfural, and the lower phase is the dehydration reaction phase of the aqueous solution of the organic quaternary ammonium salt and the catalyst, and there is a clear phase interface between the two phases, which can be separated by conventional methods, such as extraction by a syringe, separation by a separatory funnel, or other methods easily thought of by those skilled in the art.

[0095] According to some embodiments of the present application, the extraction phase (5-hydroxymethylfurfural phase) can be separated and purified to obtain the 5-hydroxymethylfurfural product.

[0096] According to some embodiments of the present application, the separation and purification method is rotary evaporation.

[0097] The preparation method of the present application uses a water-soluble sulfonic acid as a catalyst to catalyze the dehydration of fructosyl carbohydrates to prepare 5-hydroxymethylfurfural in a reaction phase composed of the catalyst, water, and an organic quaternary ammonium salt; during the dehydration reaction of fructosyl carbohydrates, an organic solvent is used as an extractant to realize in-situ extraction separation of 5-hydroxymethylfurfural; by adjusting the composition and structure of the organic quaternary ammonium salt in the reaction phase, high-purity 5-hydroxymethylfurfural can be directly obtained after separation of the organic solvent.

[0098] In the dehydration reaction of the present application, by adjusting the structure of the organic quaternary ammonium salt, the organic quaternary ammonium salt with an epoxy group structure is used to almost completely retain the impurities generated in the reaction in the reaction phase, and coupled with the extraction of the organic solvent for 5-hydroxymethylfurfural, high-purity products are obtained. That is, after the dehydration reaction is completed, 5-hydroxymethylfurfural enters the extraction phase, while the generated impurities and other reactants basically do not enter the extraction phase, which improves the purity of 5-hydroxymethylfurfural in the extraction phase, and high-purity 5-hydroxymethylfurfural products can be directly obtained after separation of the extraction agent.

[0099] In the present application, the reaction system refers to the aforementioned reaction phase and extraction phase unless otherwise specified.

[0100] According to a preferred embodiment of the present application, the preparation method of 5-hydroxymethylfurfural comprises the following steps:

[0101] After mixing the organic quaternary ammonium salt, water, catalyst, fructosyl carbohydrate and 1,4-dioxane, the fructosyl carbohydrate undergoes a dehydration reaction, and is extracted in situ during the dehydration reaction; after the dehydration reaction is completed, the phases are separated, and the extraction phase is collected;

[0102] The organic solvent in the extraction phase is removed to obtain 5-hydroxymethylfurfural;

[0103] The organic quaternary ammonium salt is 2,3-epoxypropyltrimethylammonium chloride;

[0104] The content of the catalyst is 1wt% to 20wt% based on the total amount of the catalyst and water;

[0105] The content of the organic quaternary ammonium salt is 60wt% to 75wt% based on the total amount of the catalyst, water and organic quaternary ammonium salt;

[0106] The content of the reaction phase is 10wt% to 20wt% based on the total amount of the reaction phase and extraction phase, with the reaction phase being the organic quaternary ammonium salt, water and catalyst, and the extraction phase being the organic solvent;

[0107] The fructosyl carbohydrate accounts for 1% to 50% of the total mass of the reaction phase and extraction phase.

[0108] The application will be described in detail below through examples.

[0109] In the following examples and comparative examples, the purity of the product is tested by high performance liquid chromatography; specifically, the mass of 5-hydroxymethylfurfural in the finally obtained 5-hydroxymethylfurfural product is tested by external standard method, so as to calculate the purity of the 5-hydroxymethylfurfural product.

[0110] The fructose in the examples is crystalline fructose (CAS No. 7660-25-5; purity greater than 99%), which is purchased from Tereos (Shanghai) Chemical Industry Development Co., Ltd.

[0111] The other raw materials are all commercially available products.

[0112] Example 1

[0113] The present example is a method for preparing 5-hydroxymethylfurfural, which comprises the following steps:

[0114] Sulfuric acid aqueous solution (0.33g, sulfuric acid mass concentration of 1%), 2,3-epoxypropyltrimethylammonium chloride (0.67g), fructose (1.0g) and 1,4-dioxane (9.0g) are added to a pressure-resistant bottle to form a two-liquid-phase reaction system, at this time the mass of the reaction phase accounts for 10% of the total mass of the reaction system (reaction phase and extraction phase), and the pressure-resistant bottle is sealed;

[0115] After the multi-channel heater was heated to 120°C, the sealed pressure-resistant bottle was placed in the multi-channel heater and stirred at a rotation speed of 600 r / min for 50 min;

[0116] After the reaction was completed, the pressure-resistant bottle was taken out of the multi-channel heater and naturally cooled to room temperature (about 25°C). The reaction solution was analyzed by high performance liquid chromatography. The conversion rate of fructose was 99.8% and the yield of 5-hydroxymethylfurfural was 85.8%.

[0117] After the reaction was completed, the two phases were separated. The upper extraction phase was light yellow close to colorless (see Figure 2 , the lower layer was very dark, the upper layer was close to colorless; the impurities generated during the reaction were dark, and the 5-hydroxymethylfurfural product was colorless in 1,4-dioxane; therefore, from the figure, it can be seen that the 5-hydroxymethylfurfural product prepared in this embodiment has high purity.

[0118] After the upper extraction phase was extracted and the solvent was removed in a rotary evaporator, a light yellow product (5-hydroxymethylfurfural product) 0.58 g was obtained. The purity of 5-hydroxymethylfurfural in it was 99.1% measured by high performance liquid chromatography (the liquid chromatography detection results are shown in Figure 1 , Figure 1 The horizontal coordinate in the figure is the retention time (unit: min), and the peak corresponding to a retention time of 15 min is 5-hydroxymethylfurfural. From Figure 1 , it can be seen that no other impurity peaks appear in the liquid chromatogram, thus indirectly indicating that a high-purity 5-hydroxymethylfurfural product is prepared.

[0119] Example 2

[0120] This embodiment is a method for preparing 5-hydroxymethylfurfural, which differs from Example 1 in that:

[0121] The aqueous sulfuric acid solution of equal mass is replaced with an aqueous methyl sulfonic acid solution (the mass concentration of methyl sulfonic acid is 2%), and the reaction time is shortened to 40 min.

[0122] In this embodiment, the conversion rate of fructose is 99.9%, the yield of 5-hydroxymethylfurfural is 86%, and after the solvent is removed, a light yellow product (5-hydroxymethylfurfural product) 0.59 g is obtained, in which the purity of 5-hydroxymethylfurfural is 99%.

[0123] Example 3

[0124] This embodiment is a method for preparing 5-hydroxymethylfurfural, which differs from Example 1 in that:

[0125] The aqueous sulfuric acid solution with a mass concentration of 1% is replaced with an aqueous sulfuric acid solution with a mass concentration of 20%, and the reaction temperature is lowered to 110°C, and the reaction time is shortened to 12 min.

[0126] The fructose conversion rate in this embodiment is 99.8%, the 5-hydroxymethylfurfural yield is 85.5%, and after removing the solvent, 0.58 g of a light yellow product (5-hydroxymethylfurfural product) is obtained, wherein the purity of 5-hydroxymethylfurfural is 98.9%.

[0127] Embodiment 4

[0128] This embodiment is a method for preparing 5-hydroxymethylfurfural, which differs from Embodiment 1 in that:

[0129] The mass of the aqueous sulfuric acid solution (mass concentration of 1%) and 2,3-epoxypropyltrimethylammonium chloride is doubled, which is 0.66 g and 1.34 g, respectively, and the mass of 1,4-dioxane is reduced from 9 g to 8 g, at this time, the mass of the reaction phase accounts for 20% of the total mass of the reaction system (reaction phase and extraction phase), and then the reaction temperature is increased to 130°C.

[0130] The fructose conversion rate in this embodiment is 99.8%, the 5-hydroxymethylfurfural yield is 85.6%, and after removing the solvent, 0.52 g of a light yellow product (5-hydroxymethylfurfural product) is obtained, wherein the purity of 5-hydroxymethylfurfural is 99%.

[0131] Embodiment 5

[0132] This embodiment is a method for preparing 5-hydroxymethylfurfural, which differs from Embodiment 1 in that:

[0133] The equal mass of 2,3-epoxypropyltrimethylammonium chloride in the reaction phase is replaced by epoxyethyltrimethylammonium chloride.

[0134] The fructose conversion rate in this embodiment is 99.7%, the 5-hydroxymethylfurfural yield is 85.4%, and after removing the solvent, 0.57 g of a light yellow product is obtained, wherein the purity of 5-hydroxymethylfurfural is 99.1%.

[0135] Embodiment 6

[0136] This embodiment is a method for preparing 5-hydroxymethylfurfural, which differs from Embodiment 1 in that:

[0137] The equal mass of 2,3-epoxypropyltrimethylammonium chloride in the reaction phase is replaced by 1,2-epoxybutyltrimethylammonium chloride.

[0138] The fructose conversion rate in this embodiment is 99.8%, the 5-hydroxymethylfurfural yield is 85.2%, and after removing the solvent, 0.56 g of a light yellow product is obtained, wherein the purity of 5-hydroxymethylfurfural is 98.9%.

[0139] Embodiment 7

[0140] The embodiment is a preparation method of 5-hydroxymethylfurfural, which is different from the embodiment 1 in that:

[0141] The mass of the aqueous sulfuric acid solution (1% in mass concentration) is increased to 0.4 g, and the mass of the 2,3-epoxypropyl trimethylammonium chloride is decreased to 0.6 g, and the reaction temperature is increased to 130 °C.

[0142] In the embodiment, the conversion rate of fructose is 99.7%, the yield of 5-hydroxymethylfurfural is 85.4%, and after removing the solvent, a light yellow product of 0.59 g is obtained, in which the purity of 5-hydroxymethylfurfural is 98.5%.

[0143] Embodiment 8

[0144] The embodiment is a preparation method of 5-hydroxymethylfurfural, which is different from the embodiment 1 in that:

[0145] The mass of the aqueous sulfuric acid solution (1% in mass concentration) is decreased to 0.25 g, and the mass of the 2,3-epoxypropyl trimethylammonium chloride is increased to 0.75 g, and the reaction temperature is decreased to 110 °C.

[0146] In the embodiment, the conversion rate of fructose is 99.9%, the yield of 5-hydroxymethylfurfural is 85.7%, and after removing the solvent, a light yellow product of 0.53 g is obtained, in which the purity of 5-hydroxymethylfurfural is 99.3%.

[0147] Embodiment 9

[0148] The embodiment is a preparation method of 5-hydroxymethylfurfural, which is different from the embodiment 1 in that:

[0149] The mass of the aqueous sulfuric acid solution (1% in mass concentration) is increased to 0.6 g, and the mass of the 2,3-epoxypropyl trimethylammonium chloride is decreased to 0.4 g, and the reaction temperature is increased to 140 °C.

[0150] In the embodiment, the conversion rate of fructose is 99.7%, the yield of 5-hydroxymethylfurfural is 85.6%, and after removing the solvent, a light yellow product of 0.61 g is obtained, in which the purity of 5-hydroxymethylfurfural is 92.3%.

[0151] Comparative Example 1

[0152] The comparative example is a preparation method of 5-hydroxymethylfurfural, which is different from the embodiment 1 in that:

[0153] The 2,3-epoxypropyl trimethylammonium chloride is replaced by an equal mass of tetramethylammonium chloride.

[0154] In the comparative example, the conversion rate of fructose is 99.8%, and the yield of 5-hydroxymethylfurfural is 86.0%. The upper extraction phase is brownish red (see Figure 3The impurity content in the upper layer extraction phase is higher, and the purity of the final 5-hydroxymethylfurfural product is lower. After removing the solvent, a brown-red product (5-hydroxymethylfurfural product) 0.68 g is obtained, wherein the purity of 5-hydroxymethylfurfural is 83.5%.

[0155] Comparative Example 2

[0156] This comparative example is a method for preparing 5-hydroxymethylfurfural, which differs from Example 1 in that:

[0157] 2,3-epoxypropyl trimethylammonium chloride is replaced with an equal amount of choline chloride.

[0158] In this comparative example, the conversion rate of fructose is 99.6%, the yield of 5-hydroxymethylfurfural is 85.4%, and after removing the solvent, a brown-red product (5-hydroxymethylfurfural product) 0.67 g is obtained, wherein the purity of 5-hydroxymethylfurfural is 83.2%.

[0159] Comparative Example 3

[0160] This comparative example is a method for preparing 5-hydroxymethylfurfural, which differs from Example 1 in that:

[0161] 2,3-epoxypropyl trimethylammonium chloride is replaced with an equal amount of phenyl trimethylammonium chloride.

[0162] In this comparative example, the conversion rate of fructose is 99.7%, the yield of 5-hydroxymethylfurfural is 85.7%, and after removing the solvent, a brown-red product (5-hydroxymethylfurfural product) 0.64 g is obtained, wherein the purity of 5-hydroxymethylfurfural is 90.7%.

[0163] Comparative Example 4

[0164] This comparative example is a method for preparing 5-hydroxymethylfurfural, which differs from Example 1 in that:

[0165] 2,3-epoxypropyl trimethylammonium chloride is replaced with an equal amount of benzyl trimethylammonium chloride.

[0166] In this comparative example, the conversion rate of fructose is 99.7%, the yield of 5-hydroxymethylfurfural is 85.5%, and after removing the solvent, a brown-red product (5-hydroxymethylfurfural product) 0.63 g is obtained, wherein the purity of 5-hydroxymethylfurfural is 90.1%.

[0167] Comparing the results of Example 1 and Example 2, when the catalyst is replaced with methyl sulfonic acid, the activity of fructose dehydration increases slightly, and the reaction time required to achieve the same effect is slightly reduced.

[0168] Comparing the results of Example 1 and Example 3, when the catalyst concentration is increased, the activity of fructose dehydration increases, and the same effect can be achieved at a lower reaction temperature and a shorter reaction time.

[0169] Comparing the results of Example 1 and Example 4, it can be seen that when the proportion of the reaction phase is increased, the purity of the obtained 5-hydroxymethylfurfural product is still high, but the mass of 5-hydroxymethylfurfural in the extraction phase is reduced. Therefore, in order to further increase the single extraction amount of the organic solvent for 5-hydroxymethylfurfural, the mass fraction of the reaction phase in the total reaction system (reaction phase and extraction phase) is generally not higher than 20%.

[0170] Comparing the results of Example 1, Example 5-6 and Comparative Examples 1-2, it can be seen that when the four substituents of the organic quaternary ammonium chloride salt are straight-chain hydrocarbon groups without cyclic structure, the impurities generated during the reaction are more likely to enter the extraction phase at the same time, causing the color to deepen, and thus the purity of the obtained 5-hydroxymethylfurfural product is reduced.

[0171] Comparing the results of Example 1, Example 5-6 and Comparative Examples 3-4, it can be seen that when one of the substituents of the organic quaternary ammonium chloride salt has a cyclic structure, such as a phenyl group or a benzyl group, the purity of the finally obtained 5-hydroxymethylfurfural product is increased, indicating that the use of an organic quaternary ammonium chloride salt containing a cyclic structure substituent can obtain a 5-hydroxymethylfurfural product with higher purity, but if the cyclic structure substituent contains an oxygen atom, the purity of the 5-hydroxymethylfurfural product can be further greatly improved, therefore the preferred organic quaternary ammonium salt used in the present application should have a side chain with an oxygen-containing cyclic structure.

[0172] Comparing the results of Example 1, Example 7-9, it can be seen that when the amount of the organic quaternary ammonium chloride salt in the reaction phase is reduced, the purity of the obtained 5-hydroxymethylfurfural begins to decrease; when the amount of the organic quaternary ammonium chloride salt in the reaction phase is increased, although the purity of the obtained 5-hydroxymethylfurfural can be slightly improved, the mass of 5-hydroxymethylfurfural in the extraction phase is reduced. Therefore, in order to improve the single extraction amount and purity of the organic solvent for 5-hydroxymethylfurfural, the mass fraction of the organic quaternary ammonium salt in the reaction phase is between 60% and 75%.

[0173] The above describes the preferred embodiments of the present application, but the present application is not limited thereto. Within the technical concept of the present application, various simple modifications can be made to the technical solutions of the present application, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be considered as disclosed by the present application, and all fall within the protection scope of the present application.

Claims

1. A process for the preparation of 5-hydroxymethylfurfural, characterized in that, The method comprises the following steps: The organic quaternary ammonium salt, water, catalyst, fructose-based carbohydrate and organic solvent are mixed to carry out a dehydration reaction to obtain 5-hydroxymethylfurfural; The structure of the organic quaternary ammonium salt is shown in the following formula: R1, R2, R3 and R4 are independently selected from one of alkyl and epoxy group; At least one of R1, R2, R3 and R4 is epoxy group; The alkyl includes C1-C4 alkyl; The epoxy group includes C2-C4 epoxy group; X - is a halogen ion.

2. The method of claim 1, wherein, The alkyl includes one of methyl, ethyl, 1-propyl, 2-propyl, 1-butyl, 2-butyl, 2-methyl-1-propyl and 2-methyl-2-propyl; Preferably, the epoxy group includes one of epoxy ethyl, 2,3-epoxy propyl and epoxy butyl; Preferably, the epoxy group includes 2,3-epoxy propyl.

3. The method of claim 1 or 2, wherein, The halogen ion includes one of fluoride ion, chloride ion, bromide ion and iodide ion; Preferably, the halogen ion is chloride ion; Preferably, the organic quaternary ammonium salt includes 2,3-epoxy propyl trimethyl ammonium chloride.

4. The method according to any one of claims 1 to 3, wherein, The catalyst includes sulfonic acid catalyst; Preferably, the sulfonic acid catalyst includes at least one of sulfuric acid, methyl sulfonic acid, ethyl sulfonic acid and benzene sulfonic acid.

5. The method according to any one of claims 1 to 4, wherein, The content of the catalyst is 1wt%-20wt% based on the total amount of the catalyst and water; Preferably, the content of the organic quaternary ammonium salt is 60wt%-75wt% based on the total amount of the catalyst, water and organic quaternary ammonium salt; Preferably, the content of the reaction phase is 10wt%-20wt% based on the total amount of the reaction phase and extraction phase.

6. The method according to any one of claims 1 to 5, wherein, The organic solvent includes at least one of acetone, butanone, methyl isobutyl ketone, 1,4-dioxane, tetrahydrofuran and acetonitrile; Preferably, the organic solvent includes 1,4-dioxane.

7. The method according to any one of claims 1 to 6, wherein, The content of the fructose-based carbohydrate is 1%-50% based on the total mass of the reaction phase and extraction phase; Preferably, the content of the fructose-based carbohydrate is 1%-30% based on the total mass of the reaction phase and extraction phase; Preferably, the content of the fructose-based carbohydrate is 4%-10% based on the total mass of the reaction phase and extraction phase.

8. The method according to any one of claims 1 to 7, wherein, The temperature of the dehydration reaction is 80°C-200°C; Preferably, the temperature of the dehydration reaction is 110°C-130°C; Preferably, the time of the dehydration reaction is 0.2h-1h.

9. The method according to any one of claims 1 to 8, wherein, The fructose-based carbohydrate includes at least one of crude fructose, purified fructose, polyfructose and fructose syrup.

10. The method according to any one of claims 1 to 9, wherein, The dehydration reaction is completed to separate the phases to obtain a dehydration reaction phase and an extraction phase; The organic solvent in the extraction phase is removed to obtain 5-hydroxymethylfurfural.

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