A method for preparing bis-(5-formylfurfuryl) ether by catalyzing 5-hydroxymethylfurfural with an ionic liquid catalyst

Abstract

The present invention discloses a method for preparing bis-(5-formyl furfural) ether from 5-hydroxymethyl furfural by catalysis of an ionic liquid catalyst, and belongs to the technical field of polymer precursor preparation. The method of the present invention comprises the steps of: dehydrating 5-hydroxymethyl furfural in the presence of a catalyst to obtain bis-(5-formyl furfural) ether, wherein the catalyst is an ionic liquid comprising a trifluoromethanesulfonate radical. The method for preparing bis-(5-formyl furfural) ether from 5-hydroxymethyl furfural by catalysis of an ionic liquid catalyst provided by the present invention can significantly improve the production efficiency and yield of bis-(5-formyl furfural) ether, thereby reducing energy consumption, simplifying the preparation process, cutting manufacturing costs, and optimizing the industrial production rhythm.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer precursor preparation, and in particular relates to a method for preparing bis-(5-formylfurfuryl) ether by catalyzing 5-hydroxymethylfurfural with an ionic liquid catalyst. Background Art

[0002] In recent years, bis-(5-formylfurfuryl) ether (OBMF) has attracted considerable attention as a promising biochemical. OBMF can be used to synthesize crown ethers, polyurethanes, polyamides, and imine-based polymers. It can also be combined with 1,4-diaminobenzene to synthesize polar solvent-soluble polymers with high glass transition temperatures, thermal and electrical conductivities. OBMF can also be used as a precursor for drugs, such as hepatitis B virus drugs.

[0003] Currently, the existing technology for preparing OBMF typically uses metal trifluoromethanesulfonates to catalyze the etherification of 5-hydroxymethylfurfural (hereinafter referred to as HMF) to produce OBMF. However, the production efficiency and final yield of OBMF prepared using metal trifluoromethanesulfonates are very low, and they cannot meet the industrial manufacturing needs of OBMF. Therefore, how to improve the production efficiency and yield of OBMF preparation has become an important research topic. Summary of the Invention

[0004] In view of this, the object of the present invention is to provide a method for preparing bis-(5-formylfurfuryl) ether by catalyzing 5-hydroxymethylfurfural with an ionic liquid catalyst. The preparation method of the present invention can significantly improve the production efficiency and yield of preparing OBMF.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] The present invention provides a method for preparing bis-(5-formylfurfuryl) ether from 5-hydroxymethylfurfural by using an ionic liquid catalyst, comprising the following steps: dehydrating 5-hydroxymethylfurfural in the presence of a catalyst to obtain bis-(5-formylfurfuryl) ether, wherein the catalyst is an ionic liquid containing a non-metallic cation and a trifluoromethanesulfonic acid anion.

[0007] In some embodiments, the catalyst is selected from at least one of trifluoromethanesulfonic acid N-methylpyrrolidone ionic liquid, N-butylpyridinium bis(trifluoromethanesulfonyl)imide salt ionic liquid, 1-butylsulfonic acid-3-methylimidazolium trifluoromethanesulfonate salt ionic liquid, and trifluoromethanesulfonic acid inner salt ionic liquid.

[0008] The preparation process of trifluoromethanesulfonic acid N-methylpyrrolidone ionic liquid is as follows: slowly add N-methylpyrrolidone dropwise to trifluoromethanesulfonic acid, the molar ratio of trifluoromethanesulfonic acid to N-methylpyrrolidone is 1:1, stir at room temperature for 3 to 8 hours, and vacuum dry at 25 to 45°C for 2 to 8 hours to obtain the product.

[0009] In some embodiments, the catalyst is a combination of N-methylpyrrolidone trifluoromethanesulfonate ionic liquid and 1-butyl-3-methylimidazolium trifluoromethanesulfonate ionic liquid, or a combination of 1-butylsulfonic acid-3-methylimidazolium trifluoromethanesulfonate ionic liquid and N-butylpyridinium bis(trifluoromethanesulfonyl)imide salt ionic liquid.

[0010] In some embodiments, the reaction is carried out in a solvent selected from at least one of toluene, dichloromethane, chloroform, tetrahydrofuran, 2-methyltetrahydrofuran, dimethyl carbonate, dichloroethane, 1,4-dioxane, γ-valerolactone, isopropyl alcohol, diethyl carbonate, and N,N-dimethylformamide (DMF).

[0011] In some embodiments, the concentration of HMF in the solvent is 5 g / L to 100 g / L.

[0012] In some embodiments, the mass ratio of 5-hydroxymethylfurfural to the catalyst is 1:1 to 25:1, preferably 20:1.

[0013] In some embodiments, the reaction temperature is 30-140°C, preferably 80°C.

[0014] In some embodiments, the reaction time is 3 to 24 hours, preferably 3 hours.

[0015] In some embodiments, after the dehydration reaction of 5-hydroxymethylfurfural is completed, the solvent and the product are removed, 5-hydroxymethylfurfural is added again and the dehydration reaction is carried out to obtain bis-(5-formylfurfuryl) ether.

[0016] Compared with the prior art, the present invention has the following technical effects:

[0017] (1) The OBMF preparation method of the present invention uses an ionic liquid containing a non-metallic cation and a triflate anion as a catalyst, which is significantly superior to the OBMF preparation method using a metal triflate as a catalyst. The reason is that, based on the reaction mechanism, the ionic liquid of the present invention contains a non-metallic cation and a triflate anion, and the anion and cation form an ion pair, which is extremely stable and suitable for recycling. In addition, the non-metallic cation and the triflate anion have a synergistic effect, which accelerates the etherification of HMF. The metal cation in the metal triflate does not have a substantial effect on the etherification reaction of HMF. Therefore, the OBMF preparation method of the present invention can improve selectivity, significantly improve the production efficiency (up to 200%) and yield of OBMF, thereby reducing energy consumption, simplifying the preparation process, cutting manufacturing costs, and optimizing the industrial production rhythm.

[0018] (2) The OBMF preparation method of the present invention can use multiple ionic liquids to form a composite catalyst. The multiple ionic liquid catalysts interact with each other, which can further improve the yield of OBMF.

[0019] (3) The non-metallic trifluoromethanesulfonic acid ionic liquid catalyst used in the present invention has strong water resistance, effectively overcoming the shortcoming of traditional Lewis acid instability in water, so it can well maintain catalytic activity, and only needs a catalyst to promote the reaction and obtain a higher yield. At the same time, the catalyst is easy to recycle after the reaction and can be reused without reducing the catalytic activity, which has a good application prospect in the field of catalysts. In addition, the catalyst is simple to prepare and can be obtained without high temperature and high pressure. Finally, the absence of metal can further reduce the impact on the environment. These characteristics cater to the trend of green chemistry development and meet the requirements of sustainable development. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the embodiments of the present invention, the drawings related to the embodiments are briefly introduced below.

[0021] Figure 1 is the OBMF prepared in the embodiment 1 H NMR spectrum.

[0022] Figure 2 is the OBMF prepared in the embodiment 13 C NMR spectrum.

[0023] Figure 3 HPLC chart of OBMF prepared in the examples. DETAILED DESCRIPTION

[0024] The present invention is described in detail below with reference to the embodiments, but the embodiments of the present invention are not limited thereto. Obviously, the embodiments described below are only some embodiments of the present invention. For those skilled in the art, other similar embodiments obtained without creative work all fall within the scope of protection of the present invention.

[0025] The present invention provides a method for preparing bis-(5-formylfurfuryl) ether (hereinafter referred to as OBMF) by catalyzing 5-hydroxymethylfurfural (hereinafter referred to as HMF) with an ionic liquid catalyst. The method can simplify the process for manufacturing ONMF, improve the yield of preparing OBMF, and reduce the manufacturing cost of OBMF.

[0026] The present method for preparing OBMF utilizes an etherification process. Specifically, an ionic liquid catalyst is used to dehydrate two molecules of 5-hydroxymethylfurfural, resulting in an etherification reaction to produce OBMF. Since the present method utilizes only HMF and a catalyst to prepare OBMF, the reaction materials are simple and easy to prepare. Furthermore, the reactants can be easily removed after the reaction, simplifying the preparation process and facilitating catalyst recycling.

[0027] The HMF of the present invention is a biomass resource that can be obtained based on biomass, including: agricultural and forestry wastes such as straw, rice husks, corn stalks, grass, Jerusalem artichoke, wood chips or bagasse; carbohydrate-containing crops such as potatoes, cassava, sweet potatoes, potatoes, Jerusalem artichoke, sugarcane or beets; and carbohydrates such as starch, sucrose, fructose, inulin or glucose.

[0028] The catalyst of the present invention is an ionic liquid catalyst comprising a non-metallic cation and a trifluoromethanesulfonic acid anion. - ) refers to an anion derived from a trifluoromethanesulfonic acid molecule. An ionic liquid refers to a pure ion or ion-containing substance that is liquid at room temperature. In the ionic liquid of the present invention, the trifluoromethanesulfonate anion coexists with the cation to form an ion pair, resulting in a stable structure of the ionic liquid catalyst, high solubility, and low volatility. It reacts well with reactants, thereby accelerating the reaction rate, improving selectivity, and reducing side reactions.

[0029] Specifically, the ionic liquid catalyst containing trifluoromethanesulfonate can be a single catalyst, for example, it can be at least one selected from trifluoromethanesulfonic acid N-methylpyrrolidone ionic liquid, p-toluenesulfonic acid ionic liquid, N-butylpyridine bis(trifluoromethanesulfonyl)imide salt ionic liquid, 1-butylsulfonic acid-3-methylimidazolium trifluoromethanesulfonate salt ionic liquid, 3-(1-methyl-1H-imidazol-3-ium-3-yl)propane-1-sulfonic acid inner salt ionic liquid, 1-hydroxyethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt ionic liquid, 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide salt ionic liquid, and 1-butyl-2,3-dimethylimidazolium bis(trifluoromethanesulfonyl)imide salt acidic ionic liquid.

[0030] The ionic liquid catalyst containing trifluoromethanesulfonate may also be a composite catalyst, which is composed of at least two of the above catalysts.

[0031] In some embodiments, the composite catalyst is a combination of N-methylpyrrolidone trifluoromethanesulfonate and 1-butyl-3-methylimidazolium trifluoromethanesulfonate, a combination of N-methylpyrrolidone trifluoromethanesulfonate and 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, or a combination of 1-butylsulfonic acid-3-methylimidazolium trifluoromethanesulfonate and N-butylpyridine bis(trifluoromethanesulfonyl)imide.

[0032] Among the above catalysts, N-butylpyridinium bis(trifluoromethanesulfonyl)imide, 1-butylsulfonic acid-3-methylimidazolium trifluoromethanesulfonate, 1-hydroxyethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, 3-(1-methyl-1H-imidazol-3-ium-3-yl)propane-1-sulfonic acid inner salt, 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, and 1-butyl-2,3-dimethylimidazolium bis(trifluoromethanesulfonyl)imide hydrochloric acid ionic liquids can all be obtained commercially.

[0033] N-methylpyrrolidone trifluoromethanesulfonate is obtained by the following preparation method: trifluoromethanesulfonic acid and NMP are reacted in a molar ratio of 1:1, NMP is slowly added dropwise to the trifluoromethanesulfonic acid, stirred at room temperature for 4 hours, and then placed in a vacuum drying oven at 35° C. and dried under vacuum for 4 hours.

[0034] In the reaction of the present invention, the mass ratio of HMF to catalyst ranges from 1:1 to 25:1. A mass ratio of HMF to catalyst above this lower limit can significantly increase the HMF concentration and improve the yield. A mass ratio below this upper limit ensures catalyst quality while maintaining yield. Even if catalyst is lost during the production cycle, sufficient reaction rate can be maintained, ultimately improving the yield of OBMF. A mass ratio of HMF to catalyst of 20:1 is preferred.

[0035] In the present invention, the preparation method of bis-(5-formylfurfuryl) ether is carried out in a solvent, and the HMF concentration relative to the solvent is 5 g / L to 100 g / L. This is because when the HMF concentration is above the lower limit, the raw material concentration is sufficiently high, thereby maximizing the reaction rate. On the other hand, when the HMF concentration is below the upper limit, the reaction is sufficient, and the presence of reactants after the reaction is suppressed, ultimately increasing the yield of OBMF and reducing the production cost of the fibrous carbon nanostructure.

[0036] The solvent used in the present invention is at least one selected from toluene, dichloromethane, chloroform, tetrahydrofuran, 2-methyltetrahydrofuran, dimethyl carbonate, dichloroethane, 1,4-dioxane, γ-valerolactone, isopropyl alcohol, diethyl carbonate, and N,N-dimethylformamide (DMF).

[0037] In the OBMF production method of the present invention, the reaction temperature is not particularly limited and can be appropriately set based on the concentration of the reactants, the type of catalyst, the target yield, and other factors. For example, the reaction temperature can be between 30°C and 140°C. When the reaction temperature is above the lower limit, the catalyst maintains sufficiently high activity, thereby increasing the yield of OBMF. However, when the reaction temperature is below the upper limit, decomposition of the raw materials and catalyst is suppressed. The reaction temperature is preferably 80°C.

[0038] In the method for preparing OBMF of the present invention, the reaction time is not particularly limited and can be appropriately adjusted according to the concentration of the reactants, the type of catalyst, the target yield, etc. As an example, the reaction time can be 1 to 24 hours, preferably 3 hours.

[0039] In the OBMF production method of the present invention, after the HMF dehydration reaction, the solvent can be removed from the reactor. Alternatively, the solvent and product can be removed, leaving the catalyst in the reactor, and then HMF can be added to the reactor again to continue the dehydration reaction, thereby performing a cycle. This method of recycling the catalyst can simplify the OBMF production process and reduce catalyst consumption, thereby reducing costs.

[0040] The OBMF preparation method of the present invention, which uses an ionic liquid containing a non-metallic cation and a triflate anion as a catalyst, is significantly superior to the OBMF preparation method using a metal triflate as a catalyst. This is because, based on the reaction mechanism, the metal cations in the metal triflate do not substantially affect the etherification reaction of HMF. In contrast, the non-metallic cations in the ionic liquid containing a non-metallic cation and a triflate anion employed in the present invention not only form ion pairs with the triflate anion to ensure a stable catalyst structure, but also create a synergistic effect with the triflate anion in the etherification reaction of HMF, accelerating the etherification of HMF and improving selectivity. This, in turn, increases the yield and production efficiency of OBMF, simplifies the process, and reduces costs.

[0041] The following are specific examples of preparing OBMF using the OBMF preparation method of the present invention. Unless otherwise specified, the raw materials in the following examples were purchased from Lanzhou Institute of Chemical Physics and Beijing Inotech Technology Co., Ltd., and the solvents were purchased from Dalian Bono Biochemical Reagent Factory.

[0042] In the following examples, the products of the bis-(5-formylfurfuryl) ether synthesis reaction were analyzed using Agilent's 1260 Infinity II high performance liquid chromatograph, and quantified using an external standard method.

[0043] HMF and OBMF standard solutions of different concentrations were prepared and diluted to volume with tetrahydrofuran. The resulting UV spectra were integrated and quantified, and a standard curve was prepared using Origin. The experimental product was then diluted with tetrahydrofuran and its UV spectrum peak area was measured by liquid chromatography. The peak area was then inserted into the standard curve to obtain the HMF conversion rate, OBMF yield, and HMF to OBMF selectivity.

[0044] In the following examples, the yields were calculated as follows:

[0045] Yield = (actual yield / theoretical yield) × 100%.

[0046] The OBMF prepared in the following examples 1 H NMR spectrum, 13 C NMR and HPLC patterns Figure 1-3 shown.

[0047] [Examples 1-4]

[0048] To a 35 mL reaction tube, add 100 mg of 5-hydroxymethylfurfural and 10 mL of dichloromethane. Heat to 80°C under reflux. Add 5 mg of catalyst and allow to react for 3 hours with continuous stirring. After the reaction is complete, cool to room temperature, take a sample, and analyze by HPLC. The specific catalyst and analysis results are shown in Table 1.

[0049] Table 1. Reaction conditions and OBMF yields of Examples 1-4

[0050]

[0051] [Examples 5-6]

[0052] To a 35 mL reaction tube, add 100 mg of 5-hydroxymethylfurfural and 10 mL of dichloromethane. Heat to 80°C under reflux. Add 5 mg of catalyst and allow to react for 3 hours with continuous stirring. After the reaction is complete, cool to room temperature, take a sample, and analyze by HPLC. The specific catalyst and analysis results are shown in Table 2.

[0053] Table 2. Reaction conditions and OBMF yields of Examples 5-6

[0054]

[0055]

[0056] [Examples 7-10]

[0057] 100 mg of HMF and 10 mL of dichloromethane were added to a 35 mL reaction tube, heated to a certain temperature under reflux, 5 mg of trifluoromethanesulfonic acid N-methylpyrrolidone ionic liquid was added, and the reaction was continued for 3 hours with stirring. After completion of the reaction, the mixture was cooled to room temperature, sampled, and sent to HPLC for detection. The specific reaction temperature and test results are shown in Table 3.

[0058] Table 3. Reaction conditions and OBMF yields of Examples 7-10

[0059] Example Mass ratio of HMF to catalyst Reaction temperature / ℃ OBMF yield / % 7 20:1 60 80 8 20:1 80 95 9 20:1 100 72 10 20:1 120 51

[0060] [Examples 11-15]

[0061] To a 35 mL reaction tube, 100 mg of HMF and 10 mL of dichloromethane were added. The mixture was heated to 80°C under reflux. 5 mg of N-methylpyrrolidone trifluoromethanesulfonate was added and the mixture was stirred for a predetermined time. After the reaction, the mixture was cooled to room temperature, sampled, and analyzed by HPLC. The specific reaction time and test results are shown in Table 4.

[0062] Table 4. Reaction conditions and OBMF yields of Examples 11-15

[0063] Example Mass ratio of HMF to catalyst Reaction time / h OBMF yield / % 11 20:1 1 71 12 20:1 3 95 13 20:1 9 95 14 20:1 18 95 15 20:1 24 95

[0064] [Examples 16-19]

[0065] To a 35 mL reaction tube, add 100 mg of HMF and 10 mL of solvent. Heat to 80°C under reflux. Add 5 mg of N-methylpyrrolidone trifluoromethanesulfonate and allow to react for 3 hours with continuous stirring. After the reaction, cool to room temperature, sample, and analyze by HPLC. The specific solvent and analysis results are shown in Table 5.

[0066] Table 5. Reaction conditions and OBMF yields of Examples 16-19

[0067] Example Mass ratio of HMF to catalyst solvent OBMF yield / % 16 20:1 dichloromethane 95 17 20:1 1,2-Dichloroethane 90 18 20:1 Dimethyl carbonate 87 19 20:1 Solvent-free reaction 90

[0068] [Examples 20-24]

[0069] To a 35 mL reaction tube, add 100 mg of HMF and 10 mL of dichloromethane. Heat to 80°C under reflux. Add a predetermined amount of N-methylpyrrolidone trifluoromethanesulfonate and continue stirring for 3 hours. After the reaction is complete, cool to room temperature, sample, and analyze by HPLC. The specific HMF to catalyst mass ratio and analysis results are shown in Table 6.

[0070] Table 6. Reaction conditions and OBMF yields of Examples 20-24

[0071] Example Mass ratio of HMF to catalyst OBMF yield / % 20 5:1 90 21 10:1 94 22 15:1 95 23 20:1 95 24 25:1 94

[0072] The above examples demonstrate that HMF can be readily converted to OBMF under the catalysis of an ionic liquid containing a trifluoromethanesulfonate anion and a non-metallic cation. Specifically, Examples 1, 5, 6, 8, 12, and 23 demonstrate that the highest OBMF yield occurs at a reaction temperature of 80°C, a reaction time of 3 hours, and a HMF-to-catalyst mass ratio of 20:1. Among individual catalysts, N-methylpyrrolidone trifluoromethanesulfonate exhibits the highest OBMF yield, at 95%. Among composite catalysts, the combination of N-methylpyrrolidone trifluoromethanesulfonate and 1-butyl-3-methylimidazolium trifluoromethanesulfonate exhibits the highest yield, at 98%.

[0073] [Comparative Examples 1-5]

[0074] To a 35 mL reaction tube, add 100 mg of HMF and 10 mL of dichloromethane. Heat to 80°C under reflux. Add a predetermined amount of catalyst and allow the reaction to proceed with stirring for a predetermined time. After the reaction is complete, cool to room temperature, sample, and analyze by HPLC. The specific catalyst, reaction time, and analysis results are shown in Table 7.

[0075] Table 7. Reaction conditions and OBMF yields of Comparative Examples 1-5

[0076] Comparative Example Mass ratio of HMF to catalyst catalyst Reaction time / h OBMF yield / % 1 20:1 <![CDATA[Yb(OTf)3]]> 3 75 2 20:1 <![CDATA[Yb(OTf)3]]> 6 82 3 20:1 <![CDATA[Yb(OTf)3]]> 12 83 4 20:1 <![CDATA[Sc(Otf)3]]> 12 80 5 20:1 <![CDATA[W(Otf)6]]> 12 76

[0077] According to the above embodiments and comparative examples, the following conclusions can be obtained:

[0078] Comparing Examples 1-6 with Comparative Examples 3-5, in Comparative Examples 3-5, metal triflate was used as the catalyst, and the maximum OBMF yield was 83%, while in Examples 1-4 using a single catalyst, the maximum OBMF yield was 95%, and in Examples 5-6 using the composite catalyst, the maximum OBMF yield was 98%. It can be seen that the OBMF preparation method of the present invention significantly improves the OBMF yield.

[0079] Comparing Examples 11-15 with Comparative Examples 1-3, the OBMF yield in Comparative Examples 1-3, using a metal triflate as the catalyst, reached its highest after 12 hours of reaction, whereas in Examples 11-15, using an ionic liquid as the catalyst, the OBMF yield reached its highest after 3 hours of reaction. This demonstrates that the OBMF production method of the present invention significantly shortens OBMF production time and increases OBMF production efficiency by 200%. Therefore, the OBMF production method of the present invention can reduce energy consumption and lower manufacturing costs.

[0080] Comparing Example 22 with Comparative Examples 1 and 3, even with extended reaction times using metal triflate as the catalyst, the OBMF yield in Comparative Examples 1 and 3 did not significantly increase, remaining lower than the OBMF yield of the present invention. In other words, the OBMF preparation method of the present invention achieves peak OBMF yield in a shorter time.

[0081] This demonstrates that the OBMF preparation method of the present invention is significantly superior to methods using metal trifluoromethanesulfonates as catalysts. This is because, based on the reaction mechanism, the metal cations in the metal trifluoromethanesulfonates do not substantially affect the etherification reaction of HMF. In contrast, the non-metallic cations in the ionic liquid catalyst employed in the present invention not only form ion pairs with the trifluoromethanesulfonate anion to ensure a stable catalyst structure, but also create a synergistic effect with the trifluoromethanesulfonate anion in the etherification reaction of HMF, accelerating the etherification of HMF. Therefore, the OBMF production method of the present invention can improve selectivity, thereby increasing both the yield and production efficiency of OBMF, simplifying the process, and reducing costs.

[0082] In addition, since the catalyst used in the present invention does not contain metal cations, it can also suppress pollution to the environment and facilitate the treatment of waste materials. It is not only environmentally friendly but also can further reduce costs.

[0083] [Example 25]

[0084] Add 100 mg of HMF and 10 mL of dichloromethane to a 35 mL reaction tube. Heat to 80°C under reflux. Add 5 mg of N-methylpyrrolidone trifluoromethanesulfonate and stir for 3 hours. After the reaction is complete, cool to room temperature, take a sample, and analyze it by HPLC to calculate the yield of OBMF.

[0085] After the first reaction, the solvent and product were distilled off, the catalyst was retained, 100 mg of HMF and 10 mL of dichloromethane were added again, and the same reaction was carried out. Samples were taken and sent for HPLC detection to calculate the yield of OBMF.

[0086] Repeat the above experimental steps twice, take samples respectively, send them to HPLC for detection, and calculate the yield of OBMF

[0087] The recycling effect of the catalyst was investigated through the above examples, and the reaction results of the catalyst recycling are shown in Table 8.

[0088] Table 8. Catalyst recycling times and OBMF yields of Example 25

[0089] Number of times catalyst is used OBMF yield / % 1 95 2 95 3 94 4 93 5 90

[0090] Table 8 shows that the yield of OBMF remains above 90%, demonstrating that the catalyst exhibits no significant decrease in activity after repeated use and exhibits strong stability. Therefore, the OBFM preparation method of the present invention allows for the reuse of the catalyst, further simplifies the OBMF preparation process, and further reduces catalyst costs, thus promising promising applications.

[0091] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing bis-(5-formylfurfuryl) ether by catalyzing 5-hydroxymethylfurfural with an ionic liquid catalyst, characterized in that: The method comprises the following steps: subjecting 5-hydroxymethylfurfural to a dehydration reaction in the presence of a catalyst to obtain bis-(5-formylfurfuryl) ether; The catalyst is selected from at least one of trifluoromethanesulfonic acid N-methylpyrrolidone ionic liquid, N-butylpyridine bis(trifluoromethanesulfonyl)imide salt ionic liquid, 1-butylsulfonic acid-3-methylimidazolium trifluoromethanesulfonate salt ionic liquid and trifluoromethanesulfonic acid inner salt ionic liquid; The reaction is carried out in a solvent, and the solvent is selected from at least one of dichloromethane, chloroform, dimethyl carbonate, dichloroethane, 1,4-dioxane, and diethyl carbonate.

2. The method according to claim 1, characterized in that The preparation process of trifluoromethanesulfonic acid N-methylpyrrolidone ionic liquid is as follows: slowly add N-methylpyrrolidone dropwise to trifluoromethanesulfonic acid, with the molar ratio of trifluoromethanesulfonic acid to N-methylpyrrolidone being 1:1, stir at room temperature for 3-8 hours, and vacuum dry at 25-45°C for 2-8 hours to obtain the product.

3. The method according to claim 1, characterized in that The catalyst is a combination of N-methylpyrrolidone trifluoromethanesulfonate ionic liquid and 1-butyl-3-methylimidazolium trifluoromethanesulfonate ionic liquid, or a combination of 1-butylsulfonic acid-3-methylimidazolium trifluoromethanesulfonate ionic liquid and N-butylpyridinium bis(trifluoromethanesulfonyl)imide salt ionic liquid.

4. The method according to claim 1, wherein The concentration of 5-hydroxymethylfurfural in the solvent is 5 g / L~100 g / L.

5. The method according to any one of claims 1 to 4, characterized in that The mass ratio of the 5-hydroxymethylfurfural to the catalyst is 1:1 to 25:

1.

6. The method according to claim 5, characterized in that The reaction temperature is 30~140℃.

7. The method according to claim 6, characterized in that The reaction time is 1~24 h.

8. The method according to claim 7, characterized in that The mass ratio of the 5-hydroxymethylfurfural to the catalyst is 20:1, the reaction temperature is 80° C., and the reaction time is 3 h.

9. The method according to any one of claims 1 to 4, characterized in that After the dehydration reaction of 5-hydroxymethylfurfural is completed, the solvent and the product are removed, 5-hydroxymethylfurfural is added again and dehydration reaction is carried out to obtain bis-(5-formylfurfuryl) ether.

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