Preparation of a fluorinated ionic liquid catalyst and its application in efficient CO 2 Application in transformation

Abstract

The present invention discloses the preparation of a fluorine-containing ionic liquid catalyst and its application in efficient CO2 conversion. First, an ionic liquid containing fluorine functional groups is synthesized by introducing an organic phosphine ligand or imidazole into tetrafluoro-1,4-bis(bromomethyl)benzene. Subsequently, control experiments are carried out to explore the influence of fluorine functional groups on the cycloaddition reaction of CO2 with epoxides. Meanwhile, the influence of reaction parameters such as reaction temperature, time, and low-concentration CO2 conditions on the performance of the fluorine-containing ionic liquid catalyst is also studied, and the catalytic mechanism of the fluorine-containing ionic liquid catalyst is understood. At the same time, epoxides with different structures are also studied, indicating that the catalyst has good substrate adaptability, and the fluorine-containing ionic liquid catalyst still has high catalytic activity after being recycled 5 times, broadening the scope of use of the catalyst and providing a reliable technical means for the reuse of CO2.

Description

Technical Field

[0001] The present invention belongs to the field of industrial catalysts and relates to an ionic liquid catalyst, and in particular to the preparation of a fluorine-containing ionic liquid catalyst and its reaction in CO 2 Application in cycloaddition reactions with epoxides. Background Art

[0002] At present, people have paid more and more attention to the treatment of environmental problems. How to develop a method to capture CO 2 The technology is particularly critical. 2 As a non-toxic, abundant, cheap and renewable carbon resource, CO 2 Efficient catalytic reaction of carbon raw materials into high value-added compounds is an important way to reduce atmospheric CO 2 One of the effective methods to measure the concentration of CO is 2 CO capture and storage (CCS). Aqueous amine solutions (usually monoethanolamine and methyldiethylamine) can be used as CO 2 However, these solvents have the disadvantages of high volatility, high cost, large energy consumption and corrosiveness. 2 The cycloaddition reaction with epoxides produces cyclic carbonates, which have an atomic utilization efficiency of 100%, are economical and environmentally friendly, and meet the requirements of green chemistry. At the same time, cyclic carbonates are widely used in aprotic polar solvents, lubricants, and battery electrolytes. However, due to CO 2 Due to the inherent thermodynamic stability and kinetic inertness, a highly active catalyst needs to be introduced during the reaction to promote the reaction. In previous studies, ionic liquids (ILS) were used as a new type of green medium to regulate the structure of cations and anions to promote the reaction of CO. 2 Ionic liquids are widely used in the catalysis of CO due to their excellent performance in absorption and conversion. 2 For example, Zhang et al. used thiourea-functionalized ionic liquids as effective catalysts for the synthesis of cyclic carbonates, showing a 99% propylene oxide conversion rate and a 99% selectivity for propylene carbonate at an atmospheric pressure of 1.5 MPa and a temperature of 130 °C. Dae et al. successfully synthesized a series of catalysts by incorporating various metal ions into silica-grafted ionic liquids, showing a 95.8% cyclic carbonate conversion rate at a temperature of 110 °C and an atmospheric pressure of 1.76 MPa. Although ionic liquids (ILS) are widely used in CO 2 However, most catalytic reactions involve metals, co-catalysts, and harsh environmental conditions (high temperature and high pressure). Therefore, efforts are still needed to catalyze CO under mild conditions. 2Studies on the formation of cyclic carbonates.

[0003] Fluorine has a large electronegativity and has the strongest electron-withdrawing effect. Fluorine functional groups can be attached to chelating agents, surfactants, and catalyst ligands to study CO 2 Special interactions with fluorinated compounds to design CO 2 -soluble catalyst. Therefore, fluorine-containing materials have the potential to act as CO 2 Through the literature review, we found that the synthesis and application of fluorinated functional group ionic liquids in the catalysis of CO 2 Reports on cycloaddition reactions are very rare. Therefore, it is necessary to design a fluorinated ionic liquid composed of a quaternary phosphonium salt, an imidazolium cation, and a bromide anion to synthesize CO 2 It provides a new idea for recycling and sustainable development. Summary of the invention

[0004] The purpose of the present invention is to disclose a fluorine-containing ionic liquid catalyst and a preparation method thereof.

[0005] Another object of the present invention is to disclose the above-mentioned fluorine-containing ionic liquid catalyst in CO 2 Application in the cycloaddition reaction with epoxides to generate cyclic carbonates.

[0006] 1. Preparation of fluorine-containing ionic liquid catalyst

[0007] The fluorine-containing ionic liquid catalyst of the present invention has a structural formula of one of the following four:

[0008] Ⅰ, II, III, IV.

[0009] The preparation method is as follows:

[0010] (1) Synthesis of tetrafluoro-1,4-di(bromomethyl)benzene

[0011] Using dichloromethane as solvent and triphenylphosphine as initiator, tetrafluoro-1,4-di(hydroxymethyl)benzene and carbon tetrabromide are stirred and reacted at room temperature for 20-24 hours, washed, filtered, and vacuum dried to obtain tetrafluoro-1,4-di(bromomethyl)benzene; the molar ratio of tetrafluoro-1,4-di(hydroxymethyl)benzene to carbon tetrabromide is 1:2-1:5. The molar ratio of triphenylphosphine to carbon tetrabromide is 0.8:1-1:1.2.

[0012] (2) Synthesis of fluorine-containing ionic liquid catalysts

[0013] Tetrafluoro-1,4-di(bromomethyl)benzene and an organic phosphine ligand are co-dissolved in a solvent, stirred and mixed for reaction at room temperature for 20 to 24 hours, washed and filtered, and vacuum dried to obtain a quaternary phosphonium ionic liquid; the molar ratio of tetrafluoro-1,4-di(bromomethyl)benzene to the organic phosphine ligand is 0.5:1 to 1:2.5, and the organic phosphine ligand is one of triphenylphosphine, tributylphosphine or tricyclohexylphosphine.

[0014] Alternatively, tetrafluoro-1,4-di(bromomethyl)benzene and imidazole are co-dissolved in a solvent, refluxed at 40°C to 80°C for 10h to 24h, the precipitate is filtered, washed and dried to obtain an imidazole ionic liquid. The molar ratio of tetrafluoro-1,4-di(bromomethyl)benzene to imidazole is 1:2 to 1:5, and the imidazole is N-methylimidazole.

[0015] The solvent is one of methanol, dichloromethane or N,N-dimethylformamide.

[0016] 2. Characterization of fluorinated ionic liquid catalysts

[0017] The fluorine-containing ionic liquid catalysts (I to IV) of the present invention are compared and characterized in combination with comparative experiments.

[0018] Firstly, using 1,4-di(bromomethyl)benzene as a precursor, N-methylimidazole, triphenylphosphine, tributylphosphine and tricyclohexylphosphine were introduced respectively, and four different ionic liquids were designed and synthesized as control samples.

[0019] Synthesis of catalyst IL-IM: 2.64 g (10 mmol) of 1,4-di(bromomethyl)benzene and 1.85 g (22.5 mmol) of N-methylimidazole were added to a 100 ml round-bottom flask, followed by 60 ml of distilled dichloromethane. The mixture was stirred at room temperature for 24 h, and the reaction progress was monitored by TLC plates during the reaction. After stirring was stopped, the crude product was subjected to a rotary evaporator to remove the solvent, the residue was collected and washed with acetone to remove unreacted substances, filtered, and vacuum dried at 40 °C overnight to obtain a white solid. (Yield 3.34 g, 85%)

[0020] Synthesis of catalyst IL-PP: 1.05 g (4 mmol) of 1,4-di(bromomethyl)benzene and 2.0 g (8 mmol) of triphenylphosphine were added to a 100 ml round-bottom flask, followed by 60 ml of distilled dichloromethane. The mixture was stirred at room temperature for 24 h, and the reaction progress was monitored by TLC plates during the reaction. After stirring was stopped, the crude product was subjected to a rotary evaporator to remove the solvent, the residue was collected and washed with ether three times to remove unreacted substances, filtered, and vacuum dried at 45 °C overnight to obtain a white solid. (Yield 2.6 g, 86%)

[0021] Synthesis of catalyst IL-PB: 0.528 g (2 mmol) of 1,4-di(bromomethyl)benzene and 0.8 g (4 mmol) of tributylphosphine were added to a 50 ml round-bottom flask, and then 30 ml of N,N-dimethylformamide was slowly added dropwise and refluxed for 2 hours, during which a white precipitate was generated. The mixture was then cooled to room temperature, washed with ether (100 ml) three times, filtered, and vacuum dried overnight to obtain white crystals. (Yield 1.03 g, 83%)

[0022] Synthesis of catalyst IL-CP: 1.05 g (4 mmol) of 1,4-di(bromomethyl)benzene and 1.12 g (4 mmol) of tricyclohexylphosphine were added to a 100 ml round-bottom flask, followed by 60 ml of distilled dichloromethane. The mixture was stirred at room temperature for 24 h, and the reaction progress was monitored by TLC plates during the reaction. After stirring was stopped, the crude product was subjected to a rotary evaporator to remove the solvent, the residue was collected and washed with ether three times to remove unreacted substances, filtered, and vacuum dried at 50 °C overnight to obtain a white solid. (Yield 2.84 g, 72%)

[0023] Secondly, tetrafluoro-1,4-di(bromomethyl)benzene was used as a precursor, and N-methylimidazole, triphenylphosphine, tributylphosphine and tricyclohexylphosphine were introduced respectively to synthesize four different fluorine-containing ionic liquids of the present invention (structural formulas Ⅰ to Ⅳ).

[0024] Synthesis of tetrafluoro-1,4-di(bromomethyl)benzene: Place 1.2 g (5.71 mmol) of tetrafluoro-1,4-di(hydroxymethyl)benzene in a 100 ml round-bottom flask, add 50 ml of dichloromethane after distillation, and cool in an ice bath. Slowly add 3.74 g (14.26 mmol) of triphenylphosphine and 4.73 g (14.26 mmol) of carbon tetrabromide, remove from the ice bath and heat to room temperature, stir slowly, observe the color change from orange to black to light yellow, then stir at high speed, stir at room temperature for 24 h, and monitor the reaction progress with a TLC plate during the reaction. After stirring stops, the crude product is removed from the solvent by a rotary evaporator, and then the crude product is purified by column chromatography, the developing solvent is pure petroleum ether, and the product is repeatedly rinsed with dichloromethane, filtered, and vacuum dried overnight to obtain white crystals. (Yield: 1.4 g, 76%)

[0025] Synthesis of catalyst F-IL-IM (Structural Formula I): 1.23 g (10 mmol) of tetrafluoro-1,4-di(bromomethyl)benzene and 3.4 g (50 mmol) of N-methylimidazole were added to a 100 ml round-bottom flask, and then 60 ml of methanol was added and heated to reflux for 24 h. After reflux, the unreacted methanol was removed by rotary evaporation, and the mixture was dissolved in potassium carbonate aqueous solution (6.5 g 100 ml). Crystals were found to be generated. After filtration, it was washed with deionized water 3 times and placed in an oven for vacuum drying for 24 h to obtain a white solid. (Yield: 3.3 g, 82%)

[0026] Synthesis of catalyst F-IL-PP (Structural Formula II): 1.34 g (4 mmol) of tetrafluoro-1,4-di(bromomethyl)benzene and 2.0 g (8 mmol) of triphenylphosphine were added to a 100 ml round-bottom flask, followed by 60 ml of distilled dichloromethane. The mixture was stirred at room temperature for 24 h, and the reaction progress was monitored by TLC plates during the reaction. After stirring was stopped, the crude product was subjected to a rotary evaporator to remove the solvent, the residue was collected and washed with ether three times to remove unreacted substances, filtered, and vacuum dried at 45 ° C overnight to obtain a white solid. (Yield: 2.8 g, 81%)

[0027] Synthesis of catalyst F-IL-PB (Structural Formula III): 1.34 g (4 mmol) of tetrafluoro-1,4-di(bromomethyl)benzene and 1.6 g (8 mmol) of tributylphosphine were added to a 50 ml round-bottom flask, and then 30 ml of N,N-dimethylformamide was slowly added dropwise and refluxed for 2 h, during which a white precipitate was generated. The mixture was then cooled to room temperature, washed three times with ether (100 ml), filtered, and vacuum dried overnight to obtain white crystals. (Yield: 2 g, 70%)

[0028] Synthesis of catalyst F-IL-CP (Structural Formula IV): 1.34 g (4 mmol) of 1,4-di(bromomethyl)benzene and 2.24 g (8 mmol) of tricyclohexylphosphine were added to a 100 ml round-bottom flask, followed by 60 ml of distilled dichloromethane. The mixture was stirred at room temperature for 24 h, and the reaction progress was monitored by TLC plates during the reaction. After stirring was stopped, the crude product was subjected to a rotary evaporator to remove the solvent, the residue was collected and washed with ether three times to remove the unreacted substances, filtered, and dried overnight under vacuum at 50 °C to obtain a white solid.

[0029] The structures of the eight ionic liquids synthesized above are as follows:

[0030]

[0031] For all the synthesized ionic liquid catalysts mentioned above, Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), mass spectrometry (ESI), and nuclear magnetic resonance characterization were respectively carried out.

[0032] 1. Fourier transform infrared spectroscopy

[0033] Using the KBr pellet method, Fourier transform infrared spectroscopy was performed on the synthesized ionic liquids and fluorinated ionic liquids as shown in Figure 1. By comparing Figure 1(a) and Figure 1(b), it can be seen that at 1560 cm -1 (C=C) and 1160 cm -1 (C–N + ) prove the existence of the imidazole ring. The stretching vibration peaks of C-H corresponding to methyl and methylene near 2873 cm -1 and 2959 cm -1 indicate the success of the ionic liquid skeleton. The formation of the quaternary phosphonium salt structure is also indicated between 1580 cm -1 and 1620 cm -1 . The appearance of the C=F bond at 1085 cm -1 indicates the presence of fluorine element, which shows the successful synthesis of the fluorinated ionic liquid catalyst.

[0034] 2. Thermogravimetric analysis

[0035] Under N 2 atmosphere, TGA analysis was carried out on the synthesized catalysts to investigate the thermal stability of the catalysts. As Figure 2 shown, it was found that the initial thermal decomposition temperature of all catalysts reached above 250 °C, indicating that the thermal decomposition temperature of the catalysts is higher than the cycloaddition reaction temperature and they have good thermal stability.

[0036] 3. Mass spectrometry

[0037] ESI mass spectrometry test was carried out on the synthesized fluorinated functional group F-IL-CP catalyst as shown in Figure 3. It was found that the main obvious peaks in the cation mode were at 736.4 and 737.9, which were the peaks of the fluorinated ionic liquid cation; the peak at 163 in the anion mode was the peak of 2 Br ions, and the results showed the successful synthesis of this type of fluorinated ionic liquid.

[0038] III. Exploration of the cycloaddition reaction of CO 2 with epoxides

[0039] CO 2The specific experimental process of the cycloaddition reaction with epoxides is as follows: take the required amount of ionic liquid catalyst and add it to the Schlenk tube. Then, evacuate the tube three times to exhaust the gas in the tube. Slowly add epichlorohydrin (0.925 g, 10 mmol) to the Schlenk tube. Connect the tube mouth to a flask filled with CO. 2 After the reaction, remove the Schlenk tube from the oil bath, cool it to room temperature, and discharge the remaining CO. 2 , take out the product, perform quantitative analysis by NMR peak area, and calculate the cyclic carbonate conversion rate.

[0040] 1. Comparison of catalytic performance of different ionic liquid catalysts

[0041] In order to explore the catalytic performance of the catalyst, CO 2 With epichlorohydrin (ECH) as model compounds, a cycloaddition reaction was carried out in the absence of any solvent, metal, or co-catalyst to screen out the catalyst with the best performance. The catalytic activity is shown in Table 1 below.

[0042] CO 2 The general reaction formula with epichlorohydrin (ECH) is as follows:

[0043]

[0044] Table 1 Comparison of catalytic performance of different ionic liquid catalysts

[0045]

[0046] In Table 1, a represents the reaction conditions: epichlorohydrin (0.925 g, 10 mmol), catalyst (1 mol%), CO 2 Pressure: 0.1 MPa, reaction temperature: 60°C, reaction time: 48 h. b represents the reaction conditions: epichlorohydrin (0.925 g, 10 mmol), catalyst (1 mol%), CO 2 Pressure: 0.1 MPa, reaction temperature: 40℃, reaction time: 48 h.

[0047] As shown in Table 1, when no catalyst was added, the conversion rate of cyclic carbonate was 0 and almost no product was produced (the first row). When the ionic liquid catalyst was added, it was found that the eight ionic liquid catalysts were active at a reaction temperature of 60°C, and the catalytic performance of the reaction system was improved. The conversion rate of cyclic carbonate could reach 97%~99%, showing excellent catalytic performance (the second row to the ninth row). When the temperature was appropriately lowered to 40°C, it was found that the catalytic activity of the catalysts was reduced. The ionic liquid with methylimidazole had the highest decrease, while the ionic liquid with tricyclohexylphosphine had a smaller decrease in activity than other ionic liquids, and had a higher catalytic activity. Therefore, IL-CP and F-IL-CP were selected as the next research objects to optimize the reaction conditions.

[0048] 2. Effect of different reaction conditions on catalytic performance

[0049] The ionic liquid catalysts IL-CP and F-IL-CP were used as research objects to investigate the changes in catalytic effects at 40℃, 50℃, 60℃, and 12h, 24h, 36h, and 48h to explore the optimal reaction conditions. The results are as follows Figure 4 As shown. Figure 4 It can be seen that with the increase of temperature, the conversion rate of ECH has been significantly improved. This is because the increase in temperature leads to an increase in vapor pressure, which promotes the cycloaddition reaction. As the reaction time increases, it is found that although the conversion rate of epichlorohydrin has increased, its growth rate has decreased overall. Through data sorting, it is found that at 50°C and 36h, the conversion efficiency is close to 99%. By continuing to extend the time and increase the temperature, the conversion efficiency remains stable. Therefore, 50°C and 36h are determined to be the optimal reaction conditions for the catalyst.

[0050] 3. Effect of fluorine functional groups on catalytic performance

[0051] In the IL-CP and F-IL-CP catalytic tests, it was found that the conversion rate of ionic liquids containing fluorine functional groups during the catalytic reaction was higher than that of ionic liquids without fluorine. Under the same temperature and reaction time conditions, the catalytic performance of ionic liquids containing fluorine was improved to a certain extent until the conversion rate reached the maximum. Therefore, we also investigated the other 6 ionic liquids, and the results are shown in Table 2 below.

[0052] Table 2 Effect of fluorine functional groups on CO 2 Effect of cycloaddition reaction with epichlorohydrin

[0053]

[0054] In Table 2, a represents the reaction conditions: epichlorohydrin (0.925 g, 10 mmol), catalyst (1 mol%), CO2 Pressure: 0.1 MPa, reaction temperature: 60 °C, reaction time: 24 h; b represents the reaction conditions: epichlorohydrin (0.925 g 10 mmol), catalyst (1 mol%), CO 2 Pressure: 0.1 MPa, reaction temperature: 50 °C, reaction time: 24 h; c represents the reaction conditions: epichlorohydrin (0.925 g, 10 mmol), catalyst (1 mol%), CO 2 Pressure: 0.1 MPa, reaction temperature: 50 ℃, reaction time: 48 h.

[0055] As shown in Table 2, the catalytic activity of F-IL-IM is 26% higher than that of IL-IM, the catalytic activity of F-IL-PP is 11% higher than that of IL-PP, and the catalytic activity of F-IL-PB is 12% higher than that of IL-PB. As the temperature and time change, the catalytic activity of fluorine-functionalized ionic liquids is still higher than that of non-functionalized ionic liquids, which also shows that the introduction of fluorine atoms has a positive effect on the CO 2 The activation of CO 2 The subsequent conversion was promoted. From the above results, it can be inferred that the fluorine in the prepared catalyst played a role in promoting the activity of the catalyst. This may be due to the strong negative charge of fluorine atoms and CO 2 The carbonyl carbon atom (positive charge) interacts with the carbonyl carbon atom, causing CO 2 Activation and CO 2 Increase in concentration

[0056] 4. Low concentration CO 2 Effect of atmosphere on catalytic performance

[0057] As we all know, CO in industrial waste gas 2 The concentration is about 7%-15% (v / v), so how to achieve low concentration CO 2 The conversion of CO is a topic worthy of study. Under this premise, we synthesized ionic liquid catalysts and used them in low concentration CO 2 atmosphere (15% CO 2 and 85% N 2 , v / v) for cycloaddition reaction, reaction conditions: epichlorohydrin (0.925 g, 10 mmol), catalyst (1 mol%), CO 2 Pressure 0.1MPa, reaction temperature: 60℃, the results are as follows Figure 5 shown.

[0058] Depend on Figure 5 It can be seen that after 96 hours at a reaction temperature of 60 °C, the conversion rate of epichlorohydrin reached an optimal 78% when the catalyst F-IL-CP was used, indicating that the catalyst has good performance in low CO concentration.2 The catalytic activity of fluorinated ionic liquids is also improved in different ways compared to non-fluorinated ionic liquids. The results show that in CO 2 Under low concentration conditions, the fluorine functional group has a 2 Still maintain high adsorption capacity and affinity.

[0059] 5. Study on the applicability of different epoxide substrates

[0060] Through screening of the above eight catalysts and optimization of various reaction conditions, F-IL-CP was selected as the best catalyst. Five different epoxides, including oxirane, butylene oxide, phenyl glycidyl ether, butyl glycidyl ether, and styrene oxide, were reacted with CO to produce a novel catalyst. 2 The experiment of cycloaddition reaction to generate cyclic carbonate was conducted to explore the substrate adaptability of the catalyst. The results are shown in Table 3. Specific experimental conditions: substrate 10 mmol, catalyst (1 mol%), CO 2 Pressure: 0.1 MPa.

[0061] Table 3 Effect of F-IL-CP catalyst on CO 2 Effect of cycloaddition reactions with different epoxides

[0062]

[0063] The experimental results show that the catalytic performance is excellent for all epoxides, with a yield of more than 86%, indicating that the F-IL-CP catalyst has good substrate adaptability.

[0064] 6. Study on catalyst stability

[0065] For homogeneous catalysts, it is very difficult to recycle the catalyst. Based on this study, we envisioned testing the recycling performance by placing the catalyst in ethyl acetate for sedimentation to precipitate the catalyst for recycling. We found that the F-IL-CP catalyst can be precipitated in ethyl acetate, so we recovered the catalyst from the reaction solution by centrifugation, washed it with ethyl acetate, vacuum dried it, and reused it. The results are as follows: Figure 6 shown.

[0066] Depend on Figure 6 It can be seen that the catalytic activity of F-IL-CP catalyst did not decrease significantly after being reused for more than 5 times, and the conversion rate of cyclic carbonate reached 88%. The reason for the decrease in activity may be due to the loss of part of the catalyst during the transfer process during recycling.

[0067] The catalytic mechanism of the fluorine-containing functional group F-IL-CP catalyst of the present invention is as follows:

[0068]

[0069] First, the halogen Br anion attacks the epoxide ring and causes the Br anion to coordinate with the O atom of the epoxide to form a complex. 2 After introduction, due to the strong electronegativity of fluorine atoms and CO 2 The interaction between the carbonyl carbon atoms (positively charged) leads to CO 2 activation and the CO 2 Increased concentration promotes CO 2 The conversion of CO 2 The cycloaddition reaction to the complex generates an intermediate. Then, as the intramolecular cyclization generates the cyclic carbonate, it is separated from the intermediate, and the remaining catalyst is used for the next reaction.

[0070] In summary, the present invention prepares fluorine-functionalized ionic liquids by a relatively simple synthesis method and applies them to CO 2 Research on the generation of cyclic carbonates by cycloaddition reaction with epoxides. By comparing the performance of different types of ionic liquids, it was found that the quaternary phosphonium salt type F-IL-CP ionic liquid catalyst with tricyclohexylphosphine has the best activity effect, showing excellent conversion rate of cyclic carbonates under the conditions of no solvent, metal, and co-catalyst. At the same time, the reaction conditions can be carried out at room temperature and pressure, avoiding the loss of high temperature and high pressure energy. Through experimental control, it was found that ionic liquids containing fluorine functional groups have better catalytic performance, which may be due to the strong electronegativity of fluorine atoms and CO 2 The interaction between the carbonyl carbon atoms (positively charged) leads to CO 2 The activation of epoxides improves the catalytic performance. At the same time, epoxides with different structures are also studied, which shows that the catalyst has good substrate adaptability and broadens the scope of application of the catalyst. The catalyst is recovered by settling in ethyl acetate and still has good catalytic activity after 5 cycles, indicating good stability. 2 atmosphere, still has good catalytic activity for CO 2 It provides a good resource for reuse and sustainable development. BRIEF DESCRIPTION OF THE DRAWINGS

[0071] FIG1 (a) is a Fourier transform infrared spectra of four fluorine-containing ionic liquid catalysts synthesized by the method of the present invention.

[0072] FIG1( b ) is a Fourier transform infrared spectra of four ionic liquid catalysts synthesized in the control experiment of the present invention;

[0073] Figure 2Thermogravimetric spectra of all ionic liquid catalysts synthesized in the present invention;

[0074] FIG3 (a) is an ESI mass spectrum of the fluorine-containing functional group F-IL-CP catalyst synthesized in the present invention in negative ion mode.

[0075] FIG3 (b) is an ESI mass spectrum of the fluorine-containing functional group F-IL-CP catalyst synthesized in the present invention in the positive ion mode;

[0076] Figure 4 It is a comparison diagram of the catalytic effects of the IL-CP ionic liquid catalyst and the F-IL-CP ionic liquid catalyst synthesized in the present invention under different reaction conditions;

[0077] Figure 5 All ionic liquid catalysts synthesized in the present invention can be used in low concentration CO 2 Comparison of catalytic performance under atmosphere;

[0078] Figure 6 A bar graph showing the cyclic test results of the fluorine-containing functional group F-IL-CP catalyst synthesized in the present invention; DETAILED DESCRIPTION

[0079] The present invention is further explained below with reference to specific embodiments.

[0080] Take the synthetic catalyst F-IL-CP as an example:

[0081] The structural formula of catalyst F-IL-CP is: .

[0082] The catalyst F-IL-CP was synthesized by the method of the present invention: 1.34 g (4 mmol) of tetrafluoro-1,4-di(bromomethyl)benzene and 2.24 g (8 mmol) of tricyclohexylphosphine were added to a 100 ml round-bottom flask, and then 60 ml of distilled dichloromethane was added, and the mixture was stirred at room temperature for 24 hours. During the reaction, the reaction progress was monitored by a TLC plate. After the stirring was stopped, the crude product was subjected to a rotary evaporator to remove the solvent, and the residue was collected and washed with ether three times to remove the unreacted substances, filtered, and vacuum dried at 50°C overnight to obtain a white solid.

[0083] The catalyst F-IL-CP synthesized above was structurally characterized, and the results are shown in FIG1 .

[0084] As shown in Figure 1, at 1580 cm -1 To 1620 cm -1 The characteristic peak indicates the formation of the structure of quaternary phosphonium salt at 1085 cm -1The appearance of the C=F bond indicates the presence of fluorine element, which illustrates the successful synthesis of the fluorine-containing ionic liquid catalyst.

Claims

1. A fluorine-containing ionic liquid catalyst having a structural formula of one of the following four: ， ， ， 。 2. A method for preparing a fluorine-containing ionic liquid catalyst as claimed in claim 1, It is characterized in that The following steps are involved: (1) Synthesis of tetrafluoro-1,4-di(bromomethyl)benzene Using dichloromethane as solvent and triphenylphosphine as initiator, tetrafluoro-1,4-di(hydroxymethyl)benzene and carbon tetrabromide were stirred and reacted at room temperature for 20-24 hours, washed, filtered, and vacuum dried to obtain tetrafluoro-1,4-di(bromomethyl)benzene; (2) Synthesis of fluorine-containing ionic liquid catalysts The tetrafluoro-1,4-di(bromomethyl)benzene and the organic phosphine ligand are co-dissolved in a solvent, stirred and mixed for reaction at room temperature for 20 to 24 hours, washed and filtered, and vacuum dried to obtain a quaternary phosphonium ionic liquid; the molar ratio of the tetrafluoro-1,4-di(bromomethyl)benzene to the organic phosphine ligand is 0.5:1 to 1:2.5, and the organic phosphine ligand is one of triphenylphosphine, tributylphosphine or tricyclohexylphosphine; Alternatively, tetrafluoro-1,4-di(bromomethyl)benzene and imidazole are co-dissolved in a solvent, refluxed at 40°C to 80°C for 8h to 24h, the precipitate is filtered, washed and dried to obtain an imidazole ionic liquid; the molar ratio of tetrafluoro-1,4-di(bromomethyl)benzene to imidazole is 1:2 to 1:5, and the imidazole is N-methylimidazole.

3. A method for preparing a fluorine-containing ionic liquid catalyst as claimed in claim 2, It is characterized in that In step 1), the molar ratio of tetrafluoro-1,4-di(hydroxymethyl)benzene to carbon tetrabromide is 1:2 to 1:

5.

4. A method for preparing a fluorine-containing ionic liquid catalyst as claimed in claim 2, It is characterized in that In step 1), the molar ratio of triphenylphosphine to carbon tetrabromide is 0.8:1 to 1:1.

2.

5. A method for preparing a fluorine-containing ionic liquid catalyst as claimed in claim 2, It is characterized in that In step 2), the solvent is one of methanol, dichloromethane or N,N-dimethylformamide.

6. A fluorine-containing ionic liquid catalyst as claimed in claim 1 in CO 2 Application in the cycloaddition reaction with epoxides to generate cyclic carbonates.

Images