Method for preparing 5-hydroxymethylfurfural by dehydrating fructose in low-boiling-point organic solvent

Abstract

The invention belongs to the field of organic synthesis, and discloses a method for preparing 5-hydroxymethylfurfural by dehydrating fructose in a low-boiling-point organic solvent, which comprises the following steps: mixing fructose, a thienyl super-crosslinked polymer, # imgabs0 acid and the low-boiling-point organic solvent, and reacting at the reaction temperature of 80-120 DEG C and normal pressure to prepare the 5-hydroxymethylfurfural, wherein the boiling point of the low-boiling-point organic solvent does not exceed 130 DEG C. According to the method, the low-boiling-point organic solvent with the boiling point not exceeding 130 DEG C is used as the reaction solution, meanwhile, the thienyl super-crosslinked polymer is added as the auxiliary agent, the fructose is heated and dehydrated to obtain the HMF in cooperation with the # imgabs1 # acid catalyst, the conversion rate of the fructose and the selectivity of the HMF can be remarkably improved, and a novel method is provided for preparing the 5-hydroxymethylfurfural (HMF) through dehydration of the fructose.

Description

Technical Field

[0001] The present invention belongs to the field of organic synthesis, and more specifically, relates to a method for preparing 5-hydroxymethylfurfural by dehydrating fructose in a low-boiling organic solvent. Background Art

[0002] 5-Hydroxymethylfurfural (HMF) is an important chemical raw material. Its molecule contains an aldehyde group and a hydroxymethyl group, and through hydrogenation, oxidative dehydrogenation, esterification, halogenation, polymerization, hydrolysis and other chemical reactions, it can synthesize high-value-added chemicals and new polymer materials, including pharmaceuticals, resin plastics, diesel fuel additives, etc. HMF itself has pharmaceutical activity and is an active ingredient in many traditional Chinese medicines. A series of furan derivatives prepared from HMF also have different functions, including synthesizing lead compounds in the fields of medicine and pesticides; synthesizing polymer materials with optical activity, biodegradability and other characteristics as monomers, and can also synthesize macrocyclic compounds with strong coordination ability.

[0003] As a platform compound for the efficient conversion of biomass resources, HMF can be prepared by the acid-catalyzed dehydration of carbohydrates such as fructose and glucose. The acid-catalyzed dehydration of fructose to prepare HMF has the characteristics of high reaction raw material conversion rate and good reaction selectivity, but usually uses high-boiling polar aprotic solvents such as DMSO and DMF as reaction media, which leads to difficulties in product separation and purification and generates a large amount of wastewater containing organic solvents. Although the traditional homogeneous catalytic system has high catalytic activity, the above problems seriously restrict its industrial application. Summary of the Invention

[0004] Aiming at the above defects or improvement requirements of the prior art, the purpose of the present invention is to provide a method for preparing 5-hydroxymethylfurfural by dehydrating fructose in a low-boiling organic solvent. A low-boiling organic solvent with a boiling point not exceeding 130°C is used as the reaction solution, and at the same time, a thiophene-based hypercrosslinked polymer is added as an auxiliary agent, in combination with an acid catalyst, fructose is dehydrated by heating to obtain HMF, and the conversion rate of fructose and the selectivity of HMF can be significantly improved, providing a new method for preparing 5-hydroxymethylfurfural (HMF) by dehydrating fructose.

[0005] To achieve the above object, according to the present invention, there is provided a method for preparing 5-hydroxymethylfurfural by dehydrating fructose in a low-boiling organic solvent, characterized in that the method is to mix fructose, a thiophene-based hypercrosslinked polymer, an acid and a low-boiling organic solvent, and carry out an atmospheric reaction at a reaction temperature of 80-120°C to prepare 5-hydroxymethylfurfural;

[0006] wherein, the boiling point of the low-boiling organic solvent does not exceed 130°C.

[0007] As a further preference of the present invention, the low-boiling organic solvent is one or a mixture of several of acetonitrile, ethanol, 1,2-dichloroethane, ethyl acetate, n-butyl acetate, dimethyl carbonate, tetrahydrofuran, 1,4-dioxane; preferably n-butyl acetate.

[0008] As a further preference of the present invention, the mass ratio of the thiophene-based hypercrosslinked polymer to the fructose is 1:1 to 1:10, preferably 1:1.3;

[0009] The thiophene-based hypercrosslinked polymer is prepared by using thiophene as a monomer and one or several of p-dichlorobenzyl, p-dibromobenzyl, dimethoxymethane, glyoxal, dimethyl acetal of glyoxal as a crosslinking agent, and heating and refluxing for 12 to 24 h in the presence of a Lewis acid and an oxidant to polymerize to obtain a thiophene-based hypercrosslinked polymer containing thiophene sulfoxide and thiophene sulfone fragments; wherein, the mass ratio of the thiophene to the crosslinking agent is preferably 1:1 to 1:50;

[0010] Preferably, the Lewis acid is one or several of ferric chloride, ferric bromide, aluminum chloride, manganese chloride, copper chloride, zinc bromide, stannic chloride, zirconium chloride, and the mass ratio of the thiophene to the Lewis acid is 1:1 to 1:80;

[0011] The oxidant is one or several of hydrogen peroxide, tert-butyl hydroperoxide, peroxyacetone, m-chloroperoxybenzoic acid, peracetic acid, trifluoroperacetic acid, and the mass ratio of the thiophene to the oxidant is 1:1 to 1:60;

[0012] The polymerized thiophene-based hypercrosslinked polymer is obtained by first pickling, then alcohol washing, and finally drying;

[0013] Among them, the acid used for pickling is one or several of hydrochloric acid, sulfuric acid, nitric acid, hydrobromic acid, phosphoric acid, formic acid, acetic acid, the concentration of the acid is an aqueous solution of 0.1 to 5 mol / L, the pickling temperature is 40 to 80 °C, and the pickling time is 2 to 6 h;

[0014] The alcohol washing is by Soxhlet extraction method, and the alcohol used is one or several of methanol, ethanol, n-propanol, isopropanol, n-butanol, the alcohol washing temperature is 60 to 120 °C, and the alcohol washing time is 12 to 24 h.

[0015] As a further preference of the present invention, the acid is one or a mixed acid of several of hydrochloric acid, sulfuric acid, hydrogen bromide, periodic acid, p-toluenesulfonic acid, dodecylbenzenesulfonic acid, trifluoromethanesulfonic acid, methanesulfonic acid, sulfamic acid, phosphotungstic acid;

[0016] The mass ratio of the acid component in the acid to the fructose is 1:10 to 1:100.

[0017] As a further preference of the present invention, the reaction time of the atmospheric pressure reaction is 12 to 24 h.

[0018] As a further preference of the present invention, the product 5-hydroxymethylfurfural is obtained by centrifuging the reaction system to obtain the supernatant, then concentrating the supernatant by rotary evaporation, and finally separating the concentrated solution by thin layer chromatography to obtain 5-hydroxymethylfurfural;

[0019] Preferably, the low-boiling organic solvent separated by rotary evaporation and concentration can be reused.

[0020] As a further preference of the present invention, the product 5-hydroxymethylfurfural is obtained by centrifuging the reaction system to obtain the supernatant, then concentrating the supernatant by rotary evaporation, and finally purifying the concentrated solution by recrystallization;

[0021] Preferably, the low-boiling organic solvent separated by rotary evaporation and concentration can be reused.

[0022] As a further preference of the present invention, the method further includes: recovering the thiophene-based hypercrosslinked polymer from the reaction system, and reusing the recovered thiophene-based hypercrosslinked polymer for the dehydration of fructose to prepare 5-hydroxymethylfurfural in a low-boiling organic solvent.

[0023] As a further preference of the present invention, the thiophene-based hypercrosslinked polymer is recovered by centrifuging to separate the solid in the reaction system, then repeatedly washing the solid with a low-boiling organic solvent, and then drying, thereby completing the recovery;

[0024] Preferably, the repeated washing is carried out 3 to 5 times; in each washing process, for every 30 mg of the thiophene-based hypercrosslinked polymer, the amount of the low-boiling organic solvent used is 3 to 5 mL.

[0025] As a further preference of the present invention, the low-boiling organic solvent used in the washing process can be reused by rotary evaporation recovery.

[0026] Through the above technical solutions conceived by the present invention, compared with the prior art, the present invention provides a new method for the dehydration of fructose to prepare 5-hydroxymethylfurfural (HMF), constructs a composite heterogeneous catalytic system of "dipolar catalytic material + acid", uses the thiophene-based hypercrosslinked polymer as an auxiliary agent, and the acid forms a composite catalytic system ( The acid can be a common acid), and by using a low-boiling organic solvent with a boiling point not exceeding 130°C, in the low-boiling solvent, fructose is dehydrated by heating to obtain HMF, and the conversion rate of fructose and the yield of HMF can be significantly improved (the HMF yield is 60% - 92%, and can reach more than 90%). After the reaction, the thiophene-based hypercrosslinked polymer can be reused after centrifugal separation and washing. The reaction solvent can be recovered by distillation, and the product HMF can be purified by recrystallization.

[0027] In the present invention, by using a thiophene-based hypercrosslinked polymer as an auxiliary agent, which uses thiophene as a monomer and is obtained by Friedel-Crafts reaction under oxidation conditions to obtain a thiophene-based hypercrosslinked polymer containing sulfone fragments, and the sulfone fragments therein can form a dipole microenvironment, which The regulation of the acid catalyst activity will have a positive impact on the catalytic reaction. The present invention provides a polar aprotic solvent environment similar to DMSO and DMF through a dipolar catalytic material, and realizes the dehydration of fructose to prepare HMF in a low-boiling solvent, providing a new solution for the high-value conversion of biomass resources. The thiophene-based hypercrosslinked polymer has good chemical stability, low cost, and a simple preparation method. The preparation method of the present invention uses a simple strategy based on sulfone fragments to construct a dipole microenvironment, and realizes the regulation of the microenvironment of the acid-catalyzed reaction through the dipole microenvironment, improving the catalytic activity of the catalyst and the selectivity of the reaction. Moreover, after the synthesis reaction is completed, the thiophene-based hypercrosslinked polymer auxiliary agent can be recycled and reused for the dehydration of fructose to prepare 5-hydroxymethylfurfural in a low-boiling organic solvent again.

[0028] The present invention solves the problems of low catalyst efficiency, many waste products, high energy consumption, and difficult separation and purification of products in the existing HMF preparation methods. It has the characteristics of mild reaction conditions, environmental friendliness, high industrialization potential, etc. Moreover, after the reaction, the separation and purification of the product 5-hydroxymethylfurfural are friendly, and at the same time, the recovery of thiophene-based hypercrosslinked polymer and low-boiling organic solvent is also friendly, which is suitable for the efficient conversion of biomass resources. Different from the difficult separation and purification of products, the need to use a large amount of organic solvents, and the generation of a large amount of wastewater containing organic solvents when using high-boiling polar aprotic solvents such as DMSO and DMF as the reaction medium, the present invention uses a low-boiling organic solvent as the reaction medium. In the subsequent product separation stage, only a small amount of low-boiling organic solvent is required (at this time, in addition to the supernatant obtained by centrifuging the reaction system, for the solid obtained by centrifugation, the solid is repeatedly washed with a low-boiling organic solvent, and the organic phase generated during the washing process is combined with the supernatant to achieve the full enrichment of the product; in each washing process, for every 30 mg of thiophene-based hypercrosslinked polymer, the amount of low-boiling organic solvent used can be preferably 3-5 mL), or even no additional low-boiling organic solvent is required (at this time, only for the supernatant obtained by centrifuging the reaction system), to achieve the separation and purification of the product; at the same time, the low-boiling organic solvent used in the preparation and washing processes can be recovered by rotary evaporation, and has the characteristics of low toxicity, easy separation, and recyclability. Moreover, the auxiliary agent and the product can be quickly separated by centrifugation, simplifying the post-treatment process and reducing the production cost.

[0029] The present invention solves the problem that heterogeneous catalysts in the existing HMF preparation methods require precise design and complex preparation processes. Currently, there are two widely used strategies for constructing a dipole microenvironment at the acid sites. The first method is to directly immobilize the acidic sites on a porous material containing a large number of dipole groups; the second method is to anchor the acidic sites on a carrier and then introduce it into a porous material with dipole groups on its surface. However, to ensure the effective interaction between the dipolar groups and the catalytic sites and achieve the best catalytic effect, precise design and complex preparation of the catalyst structure are still required. The present invention prepares a thiophene-based hypercrosslinked polymer in one step and realizes the regulation of the acid-catalyzed reaction microenvironment based on the dipole microenvironment regulation strategy, without the need for complex modification of the acid, improving the catalytic activity of the catalyst and the selectivity of the reaction. Detailed implementation mode

[0030] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below in conjunction with embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0031] Example 1

[0032] The preparation method of the thiophene-based hypercrosslinked polymer can be as follows: Dissolve thiophene in a polar aprotic solvent, add a crosslinking agent, a Lewis acid, and an oxidizing agent, and heat under reflux for 12 to 24 hours. After the reaction is completed, filter, wash with acid, wash with alcohol, and dry to obtain the thiophene-based hypercrosslinked polymer. Among them, the polar aprotic solvent can be one or more of dichloromethane, dibromomethane, chloroform, 1,2-dichloroethane, acetonitrile, and nitromethane; the crosslinking agent can be one or more of p-dichlorobenzyl, p-dibromobenzyl, dimethoxymethane, glyoxal, and glyoxal dimethyl acetal; the Lewis acid can be one or more of ferric chloride, ferric bromide, aluminum chloride, manganese chloride, copper chloride, zinc bromide, tin tetrachloride, and zirconium chloride; the oxidizing agent can be one or more of hydrogen peroxide, tert-butyl hydroperoxide, peroxyacetone, m-chloroperbenzoic acid, peracetic acid, and trifluoroperacetic acid; the mass ratio of thiophene to the crosslinking agent can be 1:1 to 1:50, the mass ratio of thiophene to the Lewis acid can be 1:1 to 1:80, and the mass ratio of thiophene to the oxidizing agent can be 1:1 to 1:60.

[0033] The preparation of the Th-FDA-O dipolar auxiliary in Example 1 is specifically as follows: The thiophene-based hypercrosslinked polymer can be prepared according to the following steps. Add 841.4 mg of thiophene, 2282.7 mg of dimethoxymethane, 4866 mg of ferric chloride, and 3451.4 mg of m-chloroperbenzoic acid to 50 mL of 1,2-dichloroethane, heat under reflux for 12 hours, stir the generated solid in 50 mL of 1 M dilute hydrochloric acid at 40 °C for 3 hours, filter, and perform Soxhlet extraction on the solid with ethanol at 100 °C for 12 hours. Finally, dry to obtain the solid dipolar auxiliary Th-FDA-O.

[0034] The Th-FDA-O prepared in Example 1 will be used in the subsequent examples.

[0035] Examples 2 and 3

[0036] Taking trifluoromethanesulfonic acid and sulfuric acid as examples, Examples 2 and 3 discuss the influence of different acids on the HMF preparation method of the present invention:

[0037] Preparation of HMF: Add 40 mg of fructose and 20 mg of Th-FDA-O to a 10 mL reaction tube. 20 mg of acid (when using trifluoromethanesulfonic acid, 20 mg of analytically pure trifluoromethanesulfonic acid was used in Example 2; when using sulfuric acid, 20.41 mg of concentrated sulfuric acid solution with a concentration of 98% was used in Example 3, containing 20 mg of H2SO4 solute), 1 mL of n-butyl acetate, and the reaction was carried out at 120 °C under atmospheric pressure for 20 h, and then cooled to room temperature. After the reaction was completed, the mixture was centrifuged and the supernatant was collected.

[0038] Meanwhile, the precipitate obtained by centrifugation (mainly Th-FDA-O) was extracted 5 times with 3 mL of n-butyl acetate, and the organic phase was collected.

[0039] The collected organic phase and supernatant were dried over anhydrous Na2SO4, then concentrated by rotary evaporation to separate the solvent therein, and the remaining mixture was separated by thin-layer chromatography to obtain the product.

[0040] The acids used The yields of HMF with the acids are shown in the following table:

[0041]

[0042] Examples 4 and 5

[0043] Except that n-butyl acetate was used as the low-boiling solvent in Examples 2 and 3, Examples 4 and 5 also discussed the influence of different low-boiling solvents on the preparation method of HMF of the present invention (the solvents used in the synthesis reaction process and extraction process were the same low-boiling solvent):

[0044] Preparation of HMF: 40 mg of fructose, 20 mg of Th-FDA-O, 20 mg of trifluoromethanesulfonic acid, and 1 mL of solvent were added to a 10 mL reaction tube, and the reaction was carried out at 120 °C under atmospheric pressure for 20 h, and then cooled to room temperature. After the reaction was completed, the mixture was centrifuged and the supernatant was collected.

[0045] Meanwhile, the precipitate obtained by centrifugation (mainly Th-FDA-O) was extracted 5 times with 3 mL of the solvent, and the organic phase was collected.

[0046] The collected organic phase and supernatant were dried over anhydrous Na2SO4, then concentrated by rotary evaporation to separate the solvent therein, and the remaining mixture was separated by thin-layer chromatography to obtain the product.

[0047] The solvents used and the yields of HMF are shown in the following table:

[0048]

[0049] Examples 6 and 7

[0050] Examples 6 and 7 discussed the influence of different dosages of the dipolar auxiliary agent Th-FDA-O on the preparation method of HMF of the present invention:

[0051] Preparation of HMF: Add 40 mg of fructose, a certain amount of Th-FDA-O (see the following table for details), 20 mg of trifluoromethanesulfonic acid, and 1 mL of n-butyl acetate into a 10 mL reaction tube, and react at 120 °C under normal pressure for 20 h, then cool to room temperature. After the reaction is completed, centrifuge the mixture and collect the supernatant.

[0052] Meanwhile, extract the precipitate (mainly Th-FDA-O) obtained by centrifugation with 3 mL of n-butyl acetate for 5 times, and collect the organic phase.

[0053] Dry the collected organic phase and supernatant with anhydrous Na2SO4, then rotary evaporate and concentrate to separate the solvent, and separate the remaining mixture by thin layer chromatography to obtain the product.

[0054] The yields of HMF with different dosages of Th-FDA-O are shown in the following table:

[0055]

[0056] Taking n-butyl acetate as an example of a low-boiling solvent, the recyclability of the solvent was tested in Examples 8 and 9 as follows:

[0057] Example 8

[0058] Preparation of HMF: Add 40 mg of fructose, 30 mg of Th-FDA-O, 20 mg of trifluoromethanesulfonic acid, and 1 mL of n-butyl acetate into a 10 mL reaction tube, and react at 120 °C under normal pressure for 20 h, then cool to room temperature. After the reaction is completed, centrifuge the mixture and collect the supernatant.

[0059] Meanwhile, extract the precipitate (mainly Th-FDA-O) obtained by centrifugation with 3 mL of n-butyl acetate for 5 times, and collect the organic phase.

[0060] Dry the collected organic phase and supernatant with anhydrous Na2SO4, then rotary evaporate and concentrate to recover the solvent. In this example, 86% of the solvent can be recovered (a total of 16 mL of n-butyl acetate was used in the synthesis reaction process and extraction process in this example, and 13.76 mL of n-butyl acetate can be recovered).

[0061] Meanwhile, dissolve the remaining mixture after rotary evaporation and concentration in hot ethanol (60 °C), slowly cool to room temperature for crystallization, filter and dry in vacuum to obtain 24.4 mg of HMF.

[0062] In this example, the conversion rate of fructose is 99%, and the yield of HMF is 87%.

[0063] Example 9

[0064] Preparation of HMF: Add 40 mg of fructose, 30 mg of Th-FDA-O, 20.41 mg of concentrated sulfuric acid solution with a concentration of 98%, and 1 mL of n-butyl acetate into a 10 mL reaction tube, and react at 120 °C under normal pressure for 20 h, then cool to room temperature. After the reaction is completed, centrifuge the mixture and collect the supernatant.

[0065] Meanwhile, extract the precipitate obtained by centrifugation (mainly Th-FDA-O) 5 times with 3 mL of n-butyl acetate, and collect the organic phase.

[0066] After drying the collected organic phase and supernatant with anhydrous Na2SO4, rotary evaporate and concentrate them to recover the solvent. In this example, 88% of the solvent can be recovered (in this example, a total of 16 mL of n-butyl acetate was used in the synthesis reaction process and extraction process, and 14.08 mL of n-butyl acetate can be recovered).

[0067] Meanwhile, dissolve the remaining mixture after rotary evaporation and concentration in hot ethanol (60 °C), slowly cool to room temperature for crystallization, filter and then dry in vacuum to obtain 25.8 mg of HMF.

[0068] In this example, the conversion rate of fructose is 99% and the yield of HMF is 92%.

[0069] Example 10

[0070] This example discusses the reuse of the Th-FDA-O dipolar assistant, specifically:

[0071] The first cycle: Add 40 mg of fructose, 30 mg of Th-FDA-O, 20 mg of trifluoromethanesulfonic acid, and 1 mL of n-butyl acetate into a 10 mL reaction tube, and react at 120 °C under normal pressure for 20 h, then cool to room temperature. After the reaction is completed, centrifuge the mixture and collect the supernatant.

[0072] Meanwhile, add 3 mL of n-butyl acetate to the precipitate obtained by centrifugation (mainly Th-FDA-O), stir for 5 minutes and then centrifuge, and collect the supernatant.

[0073] After repeating the washing 5 times, the precipitate can be directly used for the next cycle after drying (starting from the second cycle, the Th-FDA-O used in each cycle is the whole precipitate recovered in the previous cycle, and the dosages of other raw materials and reaction conditions remain unchanged). Meanwhile, after drying the collected organic phase and supernatant with anhydrous Na2SO4, rotary evaporate and concentrate them to separate the solvent, and the remaining mixture can be separated by thin layer chromatography to obtain the product generated in this cycle.

[0074] The HMF yield can still remain >85% after 10 cycles, as shown in the following table. This is mainly because as the number of cycles increases, the additive will inevitably be lost, affecting the HMF yield.

[0075]

[0076] Comparative Example 1

[0077] This comparative example does not use the Th-FDA-O dipolar additive:

[0078] Preparation of HMF: Add 40 mg of fructose, 20 mg of trifluoromethanesulfonic acid, and 1 mL of n-butyl acetate to a 10 mL reaction tube, and react at 120 °C under normal pressure for 20 h, then cool to room temperature. After the reaction is completed, the obtained homogeneous system is separated by thin layer chromatography to obtain 1.2 mg of the product, and the HMF yield is <10%.

[0079] Comparative Example 2

[0080] This comparative example is synthesized using DMSO as the solvent according to the traditional method:

[0081] Preparation of HMF: Add 40 mg of fructose, 20.41 mg of 98% concentrated sulfuric acid solution, and 1 mL of dimethyl sulfoxide to a 10 mL reaction tube, and react at 120 °C under normal pressure for 20 h, then cool to room temperature. After the reaction is completed, the obtained homogeneous system is extracted three times with 150 mL of ethyl acetate and water (1 / 2 (v / v)). The ethyl acetate phase is collected, dried over anhydrous Na2SO4, and then concentrated by rotary evaporation under reduced pressure. The mixture is separated by thin layer chromatography to obtain 19.6 mg of the product, and the HMF yield is 70%.

[0082] In this comparative example, 150 mL * 3 = 450 mL of ethyl acetate and water (where 150 mL is ethyl acetate) was used in the extraction process, with a large amount, much higher than the amount of low-boiling organic solvents used in Examples 2 - 10 in the extraction stage. However, since DMSO with a high boiling point was used in the synthesis reaction process, although the HMF yield was not low, a large amount of DMSO-containing wastewater would be formed during the extraction process and could not be recycled.

[0083] Comparative Example 3

[0084] This comparative example is synthesized using DMSO as the solvent according to the traditional method, but the extraction is insufficient:

[0085] Preparation of HMF: Add 40 mg of fructose, 20.41 mg of concentrated sulfuric acid solution with a concentration of 98%, and 1 mL of dimethyl sulfoxide into a 10 mL reaction tube, and react at 120 °C under normal pressure for 20 h, then cool to room temperature. After the reaction is completed, the obtained homogeneous system is extracted three times with 3 mL of ethyl acetate and water (1 / 2 (v / v)). The ethyl acetate phase is collected, dried over anhydrous Na2SO4, and then concentrated by rotary evaporation under reduced pressure. The mixture is separated by thin layer chromatography to obtain 1.7 mg of the product, and the HMF yield is <10%.

[0086] The above embodiments are only examples. For example, in addition to using a temperature of 120 °C in the reaction of the present invention, the reaction can also be carried out at other temperatures in the range of 80 - 120 °C under normal pressure, and it is also possible to dehydrate fructose to prepare 5-hydroxymethylfurfural in a low-boiling organic solvent; for another example, The specific type of acid can also be flexibly adjusted. For example, other common acids (such as hydrochloric acid, hydrogen bromide, periodic acid, p-toluenesulfonic acid, dodecylbenzenesulfonic acid, methanesulfonic acid, sulfamic acid, phosphotungstic acid) can be used; taking sulfuric acid as an example, in addition to using 98% concentrated sulfuric acid, sulfuric acid solutions with other concentrations can also be used based on the present invention, as long as the amount of acid solute contained meets the pre-requirements.

[0087] It is easy for those skilled in the art to understand that the above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principles of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing 5-hydroxymethylfurfural by dehydrating fructose in a low boiling point organic solvent, characterized in that: The method is to combine fructose, thienyl super cross-linked polymer, The acid is mixed with a low boiling point organic solvent and reacted at a reaction temperature of 80 to 120°C under normal pressure to prepare 5-hydroxymethylfurfural; Wherein, the boiling point of the low boiling point organic solvent does not exceed 130°C.

2. The method according to claim 1, characterized in that: The low boiling point organic solvent is one or a mixed solvent of acetonitrile, ethanol, 1,2-dichloroethane, ethyl acetate, n-butyl acetate, dimethyl carbonate, tetrahydrofuran, 1,4-dioxane, and preferably n-butyl acetate.

3. The method according to claim 1, characterized in that: The mass ratio of the thienyl hyper-crosslinked polymer to the fructose is 1:1 to 1:10, preferably 1:1.3; The thiophene-based hyper-crosslinked polymer is prepared by using thiophene as a monomer and one or more of p-dichlorobenzyl, p-dibromobenzyl, dimethoxymethane, glyoxal, and glyoxal dimethyl acetal as a crosslinking agent, and heating and refluxing for 12 to 24 hours in the presence of a Lewis acid and an oxidant, thereby polymerizing to obtain a thiophene-based hyper-crosslinked polymer containing thiophene sulfoxide and thiophene sulfone fragments; wherein the mass ratio of the thiophene to the crosslinking agent is preferably 1:1 to 1:50; Preferably, the Lewis acid is one or more of ferric chloride, ferric bromide, aluminum chloride, manganese chloride, copper chloride, zinc bromide, tin tetrachloride, and zirconium chloride, and the mass ratio of thiophene to the Lewis acid is 1:1 to 1:80; The oxidant is one or more of hydrogen peroxide, tert-butyl hydroperoxide, peracetone, m-chloroperbenzoic acid, peracetic acid, and trifluoroperacetic acid, and the mass ratio of the thiophene to the oxidant is 1:1 to 1:60; The thiophene-based hyper-crosslinked polymer generated by polymerization is obtained by first washing with acid, then washing with alcohol, and finally drying; The acid used for pickling is one or more of hydrochloric acid, sulfuric acid, nitric acid, hydrobromic acid, phosphoric acid, formic acid, and acetic acid, the concentration of the acid is 0.1 to 5 mol / L aqueous solution, the pickling temperature is 40 to 80° C., and the pickling time is 2 to 6 hours; The alcohol washing is a Soxhlet extraction method, and the alcohol used is one or more of methanol, ethanol, n-propanol, isopropanol, and n-butanol. The alcohol washing temperature is 60-120° C. and the alcohol washing time is 12-24 hours.

4. The method according to claim 1, characterized in that: Said The acid is one or a mixture of hydrochloric acid, sulfuric acid, hydrogen bromide, periodic acid, p-toluenesulfonic acid, dodecylbenzenesulfonic acid, trifluoromethanesulfonic acid, methanesulfonic acid, aminosulfonic acid, and phosphotungstic acid; Said The mass ratio of the acid component in the acid to the fructose is 1:10 to 1:

100.

5. The method according to claim 1, characterized in that: The reaction time of normal pressure reaction is 12 to 24 hours.

6. The method according to claim 1, characterized in that: The product 5-hydroxymethylfurfural is obtained by centrifuging the reaction system to obtain a supernatant, then the supernatant is concentrated by rotary evaporation, and finally the concentrated solution is separated by thin layer chromatography to obtain 5-hydroxymethylfurfural; Preferably, the low boiling point organic solvent separated by rotary evaporation can be reused.

7. The method according to claim 1, characterized in that: The product 5-hydroxymethylfurfural is separated by centrifugation of the reaction system to obtain a supernatant, the supernatant is concentrated by rotary evaporation, and finally the concentrate is purified by recrystallization; Preferably, the low boiling point organic solvent separated by rotary evaporation can be reused.

8. The method according to claim 1, characterized in that: The method further comprises: recovering the thienyl hyper-crosslinked polymer from the reaction system, and using the recovered thienyl hyper-crosslinked polymer again to dehydrate fructose in a low-boiling point organic solvent to prepare 5-hydroxymethylfurfural.

9. The method according to claim 8, characterized in that The thienyl hyper-crosslinked polymer is recovered by centrifugation to recover the solid in the reaction system, and then the solid is repeatedly washed with a low-boiling point organic solvent and then dried to complete the recovery; Preferably, the repeated washing is 3 to 5 times; in each washing process, the amount of the low boiling point organic solvent used is 3 to 5 mL for every 30 mg of the thienyl hyper-crosslinked polymer.

10. The method according to claim 9, characterized in that The low boiling point organic solvent used in the washing process can be recycled by rotary evaporation.

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