Preparation method and application of double-acid imidazolyl polyion liquid
By preparing a bis-acid imidazole-based polyionic liquid catalyst, the problems of high energy consumption, low yield and difficult separation in the process of biomass conversion to HMF were solved, and an efficient and green catalytic effect was achieved.
Patent Information
- Application Number
- CN202510875442.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-06-27
- Publication Date
- 2025-09-23
Smart Images
Figure CN120682415A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to a preparation method of a polyionic liquid and application thereof. Background Art
[0002] Among the numerous biomass-derived platform compounds, 5-hydroxymethylfurfural (HMF) has attracted considerable attention due to its potential conversion into a variety of organic chemicals, including 2,5-dimethylfuran, 2,5-furandicarboxylic acid, and 2,5-diformylfuran. Therefore, developing efficient strategies for converting biomass to HMF is crucial for achieving high-value utilization of biomass resources.
[0003] Corn straw is a typical inexpensive lignocellulosic biomass feedstock, and the process of directly converting it into HMF has significant economic advantages. The process of acid-catalyzed degradation of corn straw to produce HMF involves key steps such as hydrolysis, isomerization, and dehydration, in which acidic site catalysts play a core role. Currently, a variety of liquid-phase catalytic thermochemical processes have been used for biomass conversion to HMF. For example, Zhu et al. used AlCl3 as an inorganic acid catalyst to achieve the conversion of straw to HMF with a yield of 9.47%; Mankar et al. used oxalic acid as an organic acid catalyst to promote the conversion of chitosan to HMF with a yield of 27.5%.
[0004] Subsequently, Marullo et al. developed an acidic ionic liquid catalytic system, achieving the conversion of inulin to HMF with a yield of 71%. Ionic liquids have become a novel catalyst due to their structural designability, low volatility, high thermal stability, adjustable acidity, and recyclability. However, in liquid-phase catalytic systems, efficient separation of the catalyst and product after the reaction is difficult, severely restricting their industrial application. To address these issues, solid catalysts have been widely used. For example, Vasudevan et al. synthesized a dendritic fiber silica solid catalyst encapsulated with phosphotungstic acid, achieving the conversion of cellulose to HMF with a yield of 16.2%. Xing et al. prepared a dendritic macromolecular β-zeolite solid catalyst containing -SO3H, which degraded wheat straw to HMF with a yield of 19.3%. Although these supported catalysts are easily separated and recovered from the product, their limited loading limits the density of active sites, and the high-temperature calcination required during the preparation of supported solid catalysts increases production costs.
[0005] Therefore, designing and synthesizing catalysts with multiple catalytic active sites, easy separation from products and low cost remains a key issue in the process of biomass conversion to HMF. Summary of the Invention
[0006] The purpose of the present invention is to solve the technical problems of high energy consumption, low yield and difficult separation in catalyst degradation of straw, and provides a preparation method of a bis-acid type imidazole-based polyionic liquid and its application.
[0007] The preparation method of the bis-acid type imidazole-based polyionic liquid is as follows:
[0008] 1. Synthesis of 1-vinyl-3-(3-sulfopropyl)imidazolium salt (VIM-PS):
[0009] In a 50 mL round-bottom flask, add 2.50 g of 1-vinylimidazole and 20 mL of acetonitrile and stir until completely dissolved. Place the flask in an ice-water bath and maintain the reaction system temperature at 0°C. Under continuous stirring, slowly add 3.20 g of 1,3-propanesultone dropwise to the reaction solution, controlling the addition rate to avoid violent exotherm. After the addition is complete, transfer the reaction system to a 60°C water bath and stir at this constant temperature for 12 h. After the reaction is complete, cool the reaction solution to room temperature and filter it. The resulting solid is washed three times with 10 mL of ether each time and dried in a vacuum drying oven at 80°C for 6 h to obtain a white solid product, 1-vinyl-3-(3-sulfopropyl)imidazolium salt (VIM-PS).
[0010] 2. Synthesis of 1-vinyl-3-(3-sulfopropyl)imidazolium chloride ([VIM-PS][Cl]):
[0011] 3.00 g of dried 1-vinyl-3-(3-sulfopropyl)imidazolium salt was weighed, dissolved in 10 mL of deionized water, and transferred to a 50 mL round-bottom flask. 1.3 mL of concentrated hydrochloric acid was slowly added dropwise to the solution under continuous stirring. After the addition was complete, the reaction system was heated to 60°C and stirred at this constant temperature for 12 h. After the reaction was completed, the solvent was removed by vacuum distillation. The crude product was washed three times with 10 mL of diethyl ether each time and dried in a vacuum drying oven at 80°C for 6 h to obtain 1-vinyl-3-(3-sulfopropyl)imidazolium chloride ([VIM-PS][Cl]).
[0012] 3. Synthesis of 1-vinyl-3-(3-sulfopropyl) imidazole aluminum tetrachloride ([VIM-PS][AlCl4]):
[0013] 3.00 g of 1-vinyl-3-(3-sulfopropyl)imidazolium chloride and 1.60 g of anhydrous aluminum chloride were weighed and placed in a 50 mL round-bottom flask. 10 mL of deionized water was added and stirred continuously until the reaction substrate was completely dissolved. The reaction system was transferred to an 80°C water bath and stirred at this constant temperature for 12 h. After the reaction, the solvent was removed by vacuum distillation. The crude product was washed three times with 10 mL of ether each time and dried in a vacuum drying oven at 80°C for 6 h to obtain 1-vinyl-3-(3-sulfopropyl)imidazolium aluminum chloride ([VIM-PS][AlCl4]).
[0014] 4. Synthesis of bis(vinyl imidazole) dibromide ([DVIM][Br2]):
[0015] Weigh 2.50 g of 1-vinylimidazole and 2.20 g of 1,2-dibromoethane into a 50 mL round-bottom flask; add 20 mL of toluene and continue stirring until the reaction mixture is completely dissolved. Transfer the reaction system to a 90 °C water bath and stir at this constant temperature for 24 h. After the reaction is completed, cool the system to room temperature and filter. Wash the resulting solid three times with 10 mL of ether each time, and then dry it in a vacuum drying oven at 40 °C for 6 h to obtain bis(vinylimidazole) dibromide ([DVIM][Br2]).
[0016] 5. Polyionic Liquid ([VIM-PS][AlCl4]) n -([DVIM][Br2]) m Synthesis of:
[0017] 1.00 g of 1-vinyl-3-(3-sulfopropyl)imidazolium tetrachloride as a polymerization monomer and 0.30 g of bis(vinylimidazole) dibromide as a cross-linking agent were weighed and added to a 25 mL round-bottom flask equipped with a reflux condenser containing 5 mL of methanol. 50 mg of azobisisobutyronitrile was then added as an initiator. After nitrogen was introduced to deoxygenate, nitrogen protection was maintained and the reaction was carried out in a constant temperature water bath at 60 °C for 24 h. After the reaction was completed, the mixture was cooled to room temperature and filtered. The resulting solid polymer was washed three times with 10 mL of ether each time and dried in a vacuum drying oven at 80 °C for 6 h. The resulting white solid product was a bis-acid type imidazole-based polyionic liquid ([VIM-PS][AlCl4]). n -([DVIM][Br2]) m .
[0018] The bis-acid type imidazole-based polyionic liquid is used as a catalyst for degrading biomass and converting it into 5-hydroxymethylfurfural.
[0019] The application method of the bis-acid type imidazole-based polyionic liquid is as follows:
[0020] 300 mg of bis-acid-type imidazole-based polyionic liquid was added to a 20 mL high-pressure reactor containing 2 g of dry biomass powder and 16 mL of solvent, and then reacted at 180 °C for 2 h. After the reaction was terminated, it was cooled to room temperature, filtered, and the filter cake was washed with ethanol several times. The filtrate was used for solvent recovery, and the residue obtained was 5-hydroxymethylfurfural.
[0021] The biomass comprises cellulose, wheat straw or corn straw.
[0022] The solvent includes water, ethanol, N,N-dimethylformamide, 1,4-dioxane or tetrahydrofuran.
[0023] The present invention provides a preparation method of an imidazole-based polyionic liquid catalyst and its application in catalyzing biomass degradation into 5-hydroxymethylfurfural, alleviating the problems of high energy consumption, low yield and difficult separation in catalyst-degrading straw.
[0024] The present invention uses 1-vinylimidazole as a raw material and carries out a quaternization reaction with 1,3-propane sultone to introduce a sulfonic acid group to synthesize 1-vinyl-3-(3-sulfopropyl)imidazolium salt (VIM-PS), which is then protonated with hydrochloric acid to obtain ([VIM-PS][Cl]), and then uses AlCl3 for anion exchange to obtain an ionic liquid monomer ([VIM-PS][AlCl4]) with Brønsted-Lewis bisacidity. At the same time, bis(vinylimidazole) dibromide ([DVIM][Br2]) is synthesized using 1-vinylimidazole and 1,2-dibromoethane as substrates. Finally, using [VIM-PS][AlCl4] as a polymerization monomer, [DVIM][Br2] as a cross-linking agent, and azobisisobutyronitrile as an initiator, an imidazole-based polyionic liquid ([VIM-PS][AlCl4]) with bisacidity and using polybisimidazole as an isolation group is obtained through copolymerization. n -([DVIM][Br2]) m The solid, the synthetic route is as follows:
[0025]
[0026] Advantages of the present invention:
[0027] (1) As the building blocks of the catalyst, the di-acidic ionic liquid can provide far more catalytic sites than supported solid catalysts, thereby improving the catalytic efficiency of the catalytic system.
[0028] (2) The introduction of Lewis acid (AlCl3) effectively promoted the isomerization of glucose and improved the selectivity of HMF during biomass conversion, thereby increasing the HMF yield of the catalytic system.
[0029] (3) A solid catalyst was synthesized, and its separation efficiency during the recovery process is much higher than that of a liquid catalyst, making the catalytic system greener and more efficient. BRIEF DESCRIPTION OF THE DRAWINGS
[0030] Figure 1 is the 1-vinyl-3-(3-sulfopropyl)imidazolium salt (VIM-PS) in Example 1 1 H NMR spectrum;
[0031] Figure 2is the 1-vinyl-3-(3-sulfopropyl)imidazolium chloride ([VIM-PS][Cl]) in Example 2 1 H NMR spectrum;
[0032] Figure 3 is the 1-vinyl-3-(3-sulfopropyl) imidazole aluminum tetrachloride ([VIM-PS][AlCl4]) in Example 3 1 HNMR spectrum;
[0033] Figure 4 is the bis(vinyl imidazole) dibromide ([DVIM][Br2]) in Example 4 1 H NMR spectrum;
[0034] Figure 5 The catalyst in Example 5 ([VIM-PS][AlCl4]) n -([DVIM][Br2]) m Infrared spectra before and after recovery. DETAILED DESCRIPTION
[0035] Example 1: Synthesis of 1-vinyl-3-(3-sulfopropyl)imidazolium salt (VIM-PS):
[0036] To a 50 mL round-bottom flask, 1-vinylimidazole (2.50 g, 26.56 mmol) and acetonitrile (20 mL) were added and stirred until completely dissolved. The flask was placed in an ice-water bath and the reaction system temperature was maintained at 0°C. With continuous stirring, 1,3-propanesultone (3.20 g, 26.20 mmol) was slowly added dropwise to the reaction solution, controlling the addition rate to avoid excessive exotherm. After the addition was complete, the reaction system was transferred to a 60°C water bath and stirred at this constant temperature for 12 h. After the reaction was complete, the reaction solution was cooled to room temperature and filtered. The resulting solid was washed thoroughly with diethyl ether (3 × 10 mL) and dried in a vacuum oven at 80°C for 6 h to obtain 1-vinyl-3-(3-sulfopropyl)imidazolium salt (VIM-PS) as a white solid in a yield of 96%.
[0037] 1H NMR (400 MHz, D2O) δ 7.62–7.59 (m, 1H), 7.45–7.43 (m, 1H), 6.95 (dd, J = 15.6, 8.7 Hz, 1H), 5.61 (d, J = 15.6 Hz, 1H), 5.23 (d, J = 8.6 Hz,1H), 4.22 (t, J = 7.1 Hz, 2H), 2.75 (t, J = 7.4 Hz, 2H), 2.18–2.12 (m, 2H). Figure 1 shown.
[0038] Example 2: Synthesis of 1-vinyl-3-(3-sulfopropyl)imidazolium chloride ([VIM-PS][Cl]):
[0039] 3.00 g (13.88 mmol) of dried VIM-PS was weighed and dissolved in 10 mL of deionized water. The mixture was then transferred to a 50 mL round-bottom flask. 1.3 mL of concentrated hydrochloric acid was slowly added dropwise to the solution with continuous stirring. After the addition was complete, the reaction system was heated to 60°C and stirred for 12 h. After the reaction, the solvent was removed by vacuum distillation. The crude product was washed with diethyl ether (3 × 10 mL) and dried in a vacuum oven at 80°C for 6 h. 1-vinyl-3-(3-sulfopropyl)imidazolium chloride ([VIM-PS][Cl]) was obtained as a viscous liquid in a yield of 98%.
[0040] 1H NMR (400 MHz, D2O) δ 8.69 (s, 1H), 7.40 (s, 1H), 7.20 (s, 1H),6.86 – 6.55 (m, 1H), 5.39 (d, J = 14.1 Hz, 1H), 4.99 (d, J = 24.0 Hz, 1H),4.12 – 3.85 (m, 2H), 2.62 – 2.36 (m, 2H), 2.02 – 1.76 (m, 2H). Figure 2 shown.
[0041] Example 3: Synthesis of 1-vinyl-3-(3-sulfopropyl)imidazolium tetrachloride ([VIM-PS][AlCl4]):
[0042] [VIM-PS][Cl] (3.00 g, 10.00 mmol) and anhydrous aluminum chloride (AlCl₃, 1.60 g, 12.00 mmol) were weighed and placed in a 50 mL round-bottom flask. 10 mL of deionized water was added and stirred continuously until the substrate was completely dissolved. The reaction system was then transferred to an 80°C water bath and stirred for 12 h. After completion of the reaction, the solvent was removed by vacuum distillation. The crude product was washed thoroughly with diethyl ether (3 × 10 mL) and dried in a vacuum oven at 80°C for 6 h to obtain 1-vinyl-3-(3-sulfopropyl)imidazolium tetrachloride ([VIM-PS][AlCl₄]) as a yellow solid in a yield of 97%.
[0043] 1 H NMR (400 MHz, D2O) δ 8.66 (s, 1H), 7.38 (s, 1H), 7.20 (s, 1H), 6.72 (dd, J = 15.6, 8.7 Hz, 1H), 5.38 (d, J = 13.0 Hz, 1H), 5.00 (d, J = 6.1 Hz,1H), 3.98 (t, J = 7.1 Hz, 2H), 2.53 (t, J = 7.4 Hz, 2H), 1.91 (p, J = 7.2 Hz,2H). Figure 3 shown.
[0044] Example 4: Synthesis of bis(vinyl imidazole) dibromide ([DVIM][Br2]):
[0045] 1-Vinyl imidazole (2.50 g, 26.56 mmol) and 1,2-dibromoethane (2.20 g, 11.58 mmol) were weighed and placed in a 50 mL round-bottom flask. Toluene (20 mL) was added and stirred continuously until the reaction mixture was completely dissolved. The reaction system was then transferred to a 90°C water bath and stirred for 24 h. After the reaction was completed, the system was cooled to room temperature and filtered. The resulting solid was washed with diethyl ether (3 × 10 mL) and dried in a vacuum oven at 40°C for 6 h to obtain bis(vinylimidazole) dibromide ([DVIM][Br2]) as a white solid in 88% yield.
[0046] 1H NMR (400 MHz, DMSO-d6) δ 9.65 (s, 1H), 8.28 (s, 1H), 7.91 (s, 1H),7.37 (dd, J = 15.6, 8.7 Hz, 1H), 6.00 (d, J = 15.6 Hz, 1H), 5.46 (d, J = 8.6Hz, 1H), 4.84 (s, 2H). Figure 4 shown.
[0047] Example 5: Polyionic Liquid ([VIM-PS][AlCl4]) n -([DVIM][Br2]) m Synthesis
[0048] 1.00 g of [[VIM-PS][AlCl4]] as the polymerization monomer and 0.30 g of [DVIM][Br2] as the cross-linker were weighed and added to a 25 mL round-bottom flask equipped with a reflux condenser and 5 mL of methanol. 50 mg of azobisisobutyronitrile was then added as the initiator. After nitrogen was introduced to remove oxygen, the mixture was maintained under nitrogen protection and reacted in a water bath at 60°C for 24 h. After completion of the reaction, the mixture was cooled to room temperature and filtered. The resulting solid polymer was washed with methanol (3 × 10 mL) and dried in a vacuum oven at 80°C for 6 h. The resulting white solid product was the polyionic liquid ([VIM-PS][AlCl4]). n -([DVIM][Br2]) m The yield is 93%, and its infrared spectrum is as shown in FIG. Figure 5 shown.
[0049] Example 6: ([VIM-PS][AlCl4]) n -([DVIM][Br2]) m Catalyst degradation of corn straw
[0050] In a 20 mL autoclave, dry corn straw powder (2 g), THF (16 mL) and ([VIM-PS][AlCl4]) were added in sequence. n -([DVIM][Br2]) m Catalyst (300 mg) was added and reacted at 180 °C for 2 h. After the reaction was terminated, the mixture was cooled to room temperature, filtered, and the filter cake was washed with ethanol (3 × 10 mL).
[0051] The filtrate was subjected to solvent recovery, and the residue was determined by high performance liquid chromatography (HPLC) to have an HMF yield of 43.5%.
[0052] The filter cake is used to separate the catalyst from the degradation residue. Due to the significant density difference between the catalyst and the residue, the catalyst quickly settles to the bottom. The upper suspension containing the residue is removed by decantation. The resulting lower solid layer is washed multiple times with ethanol, filtered, and the catalyst is recovered and dried at 80°C, with a recovery rate of up to 91%.
Claims
1. A method for preparing a polyionic liquid of a bis-acid type imidazole group, characterized in that The preparation method of the bis-acid type imidazole-based polyionic liquid is as follows:
1. Synthesis of 1-vinyl-3-(3-sulfopropyl)imidazolium salt: To a 50 mL round-bottom flask, add 2.50 g of 1-vinylimidazole and 20 mL of acetonitrile and stir until completely dissolved. Place the flask in an ice-water bath and maintain the reaction system at 0°C. Slowly add 3.20 g of 1,3-propanesultone dropwise to the reaction solution while stirring continuously. Control the addition rate to avoid excessive heat release. After the addition is complete, transfer the reaction system to a 60°C water bath and stir at this constant temperature for 12 h. After the reaction is complete, cool the reaction solution to room temperature and filter. Wash the resulting solid three times with 10 mL of ether each time and dry it in a vacuum oven at 80°C for 6 h to obtain a white solid product, 1-vinyl-3-(3-sulfopropyl)imidazolium salt.
2. Synthesis of 1-vinyl-3-(3-sulfopropyl)imidazolium chloride: Weigh 3.00 g of dried 1-vinyl-3-(3-sulfopropyl)imidazolium salt, dissolve it in 10 mL of deionized water, and transfer it to a 50 mL round-bottom flask. Slowly add 1.3 mL of concentrated hydrochloric acid dropwise to the solution while stirring. After the addition is complete, heat the reaction system to 60°C and stir at this constant temperature for 12 h. After the reaction is complete, remove the solvent by vacuum distillation. The crude product is washed three times with 10 mL of ether each time and dried in a vacuum drying oven at 80°C for 6 h to obtain 1-vinyl-3-(3-sulfopropyl)imidazolium chloride.
3. Synthesis of 1-vinyl-3-(3-sulfopropyl) imidazole aluminum chloride: Weigh 3.00 g of 1-vinyl-3-(3-sulfopropyl)imidazolium chloride and 1.60 g of anhydrous aluminum chloride into a 50 mL round-bottom flask. Add 10 mL of deionized water and continue stirring until the reaction substrate is completely dissolved. Transfer the reaction system to an 80°C water bath and stir at this constant temperature for 12 h. After the reaction is complete, remove the solvent by vacuum distillation. Wash the crude product three times with 10 mL of ether each time and dry it in a vacuum drying oven at 80°C for 6 h to obtain 1-vinyl-3-(3-sulfopropyl)imidazolium tetrachloride.
4. Synthesis of bis(vinyl imidazole) dibromide: Weigh 2.50 g of 1-vinylimidazole and 2.20 g of 1,2-dibromoethane into a 50 mL round-bottom flask; add 20 mL of toluene and continue stirring until the reaction mixture is completely dissolved. Transfer the reaction system to a 90°C water bath and stir at this constant temperature for 24 h. After the reaction is complete, cool the system to room temperature and filter. Wash the resulting solid three times with 10 mL of ether each time, then dry it in a 40°C vacuum drying oven for 6 h to obtain bis(vinylimidazole) dibromide.
5. Polyionic Liquid ([VIM-PS][AlCl4]) n -([DVIM][Br2]) m Synthesis of: 1.00 g of 1-vinyl-3-(3-sulfopropyl)imidazolium tetrachloride as a polymerization monomer and 0.30 g of bis(vinylimidazole) dibromide as a cross-linking agent were weighed and added to a 25 mL round-bottom flask equipped with a reflux condenser containing 5 mL of methanol. 50 mg of azobisisobutyronitrile was then added as an initiator. After nitrogen was introduced to deoxygenate, nitrogen protection was maintained and the reaction was carried out in a constant temperature water bath at 60 °C for 24 h. After completion of the reaction, the mixture was cooled to room temperature and filtered. The obtained solid polymer was washed three times with 10 mL of ether each time and dried in a vacuum drying oven at 80 °C for 6 h. Finally, a white solid product was obtained, which was a bis(acid-type) imidazole-based polyionic liquid.
2. The use of the bis-acid type imidazole-based polyionic liquid according to claim 1, characterized in that The bis-acid type imidazole-based polyionic liquid is used as a catalyst for degrading biomass and converting it into 5-hydroxymethylfurfural.
3. The use of a polyionic liquid of bis-acid type imidazoles according to claim 2, characterized in that The application method of the bis-acid type imidazole-based polyionic liquid is as follows: 300 mg of bis-acid-type imidazole-based polyionic liquid was added to a 20 mL high-pressure reactor containing 2 g of dry biomass powder and 16 mL of solvent, and then reacted at 180 °C for 2 h. After the reaction was terminated, it was cooled to room temperature, filtered, and the filter cake was washed with ethanol several times. The filtrate was used for solvent recovery, and the residue obtained was 5-hydroxymethylfurfural.
4. The use of a polyionic liquid of bis-acid type imidazoles according to claim 3, characterized in that The biomass comprises cellulose, wheat straw or corn straw.
5. The use of the polyionic liquid of bis-acid type imidazole group according to claim 3, characterized in that The solvent includes water, ethanol, N,N-dimethylformamide, 1,4-dioxane or tetrahydrofuran.