Imidazolyl polymeric ionic liquid as well as preparation method and application thereof

Abstract

The invention discloses imidazolyl polymeric ionic liquid as well as a preparation method and application thereof. The preparation method of the imidazolyl polymerized ionic liquid comprises the following steps: (1) dispersing a bismaleimide compound and 1-allyl-3-vinyl imidazole halogenated salt in a solvent, adding an initiator, and carrying out polymerization reaction at 65-85 DEG C, so as to obtain an imidazolyl polymerized ionic liquid crude product after the reaction is finished; and (2) washing the imidazolyl polymerized ionic liquid crude product with ethyl acetate for multiple times, and then carrying out vacuum drying to prepare the imidazolyl polymerized ionic liquid. The preparation process of the imidazolyl polymeric ionic liquid is simple, high-temperature and high-pressure conditions are not needed, and the imidazolyl polymeric ionic liquid is suitable for industrial production. As a green catalyst, the solid catalyst can catalyze an epoxy compound and carbon dioxide to synthesize cyclic carbonate, after the catalytic reaction is completed, the solid catalyst can be easily recycled through simple filtration, and the complex recycling step of a traditional heterogeneous catalyst is avoided.

Description

Technical Field

[0001] The present application belongs to the field of material synthesis catalysis, and in particular relates to a class of imidazole-based polymeric ionic liquids and preparation methods and applications thereof. Background Art

[0002] As the times progress and science and technology develop, humans are paying more and more attention to the importance of protecting the environment. Carbon dioxide is a greenhouse gas, and its emissions directly affect the earth's temperature and climate change. It is the main cause of a series of environmental problems such as sea level rise and glacier melting. At the same time, carbon dioxide is also a relatively abundant C1 resource on the earth. The chemical conversion of captured CO2 into high-value-added chemicals is an effective way to achieve CO2 emission reduction and resource utilization. Among them, the synthesized cyclic carbonate is a very important chemical product with excellent physical and chemical properties, such as high boiling point, high polarity, low volatility, and good biodegradability and solubility. It is widely used in green aprotic solvents, lithium-ion battery electrolytes, additives, plastics, medicines and fine chemicals.

[0003] Porous organic polymer materials have the advantages of pore structure, excellent adsorption performance and highly adjustable chemical composition. They are widely used in many fields such as gas adsorption and separation, catalysis, sensing, drug delivery, etc. The porous organic polymers reported so far for catalytic conversion of CO2 to synthesize cyclic carbonates include: metal organic framework polymers, hypercrosslinked ionic polymers, covalent triazine-based porous organic frameworks, diamine functionalized porous organic polymers, imidazolate organic frameworks and pyridine zinc-based porous organic polymers. The various types of porous organics reported above still require co-catalysts or harsh reaction conditions when catalyzing the cycloaddition reaction of CO2 and epoxides. Patent document No. 201711274506.1 discloses a method for using metal organic framework materials as catalysts to achieve the conversion of carbon dioxide into cyclic carbonates. Although the conversion rate of this method can reach more than 90%, the synthesis process of metal organic framework materials is relatively complicated and usually requires the addition of co-catalysts. Patent document No. 201910850696.X discloses a method for catalyzing the conversion of carbon dioxide into a target product using a polymerized ionic liquid as a catalyst. After reacting for 5 hours at a temperature of 100°C under a pressure of 1.2 MPa, the conversion rate of propylene oxide reached 75%. Patent document No. 201610714850.7 discloses a method for catalyzing the conversion of carbon dioxide using amine organic matter as a catalyst. Under the condition of 100°C, the method can achieve a carbon dioxide conversion rate of more than 90%; however, at room temperature, even after reacting for 24 hours, the conversion rate can only reach 10%, showing the problem of low conversion efficiency and long time required at lower temperatures. Therefore, it is of great significance to develop a green, simple to prepare, low-cost, high-activity site polymer synthesis method, and the material is also of great significance for the efficient catalytic conversion of carbon dioxide under solvent-free and catalyst-free conditions. Summary of the invention

[0004] In view of the shortcomings of the prior art, the purpose of the present application is to provide a class of imidazole-based polymerized ionic liquids and their preparation methods and applications. The present application provides an imidazole-based ionic liquid that is simple to prepare, novel in structure, has excellent catalytic performance and can be recycled, and provides the application of the ionic liquid as a catalyst for the cycloaddition reaction of carbon dioxide and epoxide; at the same time, the present application also provides a method for preparing cyclic carbonates by catalyzing the reaction of carbon dioxide and epoxide under mild conditions without the need for solvents and co-catalysts using the ionic liquid.

[0005] The purpose of this application is achieved through the following technical solutions: A type of imidazole-based polymeric ionic liquid, the structural formula of which is shown in Formula I:

[0006] Formula I Wherein, X = Cl, Br or I; R is selected from the following groups: substituted or unsubstituted C1-30 alkyl, substituted or unsubstituted C1-30 aryl, substituted or unsubstituted C2-C30 aryl-alkyl, substituted or unsubstituted C3-C30 aryl-alkyl-aryl, substituted or unsubstituted C3-C30 aryl-carbonyl-aryl, substituted or unsubstituted C2-C30 aryl-oxy-aryl, substituted or unsubstituted C2-C30 aryl-thio-aryl, substituted or unsubstituted C2-C30 aryl-sulfone-aryl.

[0007] The preparation method of the above-mentioned imidazole-based polymeric ionic liquid comprises the following steps: (1) dispersing a bismaleimide compound and a 1-allyl-3-vinyl imidazole halide in a solvent, adding an initiator and performing a polymerization reaction at 65 to 85° C., and obtaining a crude imidazole-based polymerized ionic liquid after the reaction is completed; (2) The crude imidazole-based polymerized ionic liquid is washed with ethyl acetate for multiple times and then vacuum dried to prepare the imidazole-based polymerized ionic liquid.

[0008] Preferably, in step (1), the structural formula of the bismaleimide compound is as follows:

[0009] Wherein, R1 is selected from the following groups: substituted or unsubstituted C1-30 alkyl, substituted or unsubstituted C1-30 aryl, substituted or unsubstituted C2-C30 aryl-alkyl, substituted or unsubstituted C3-C30 aryl-alkyl-aryl, substituted or unsubstituted C3-C30 aryl-carbonyl-aryl, substituted or unsubstituted C2-C30 aryl-oxy-aryl, substituted or unsubstituted C2-C30 aryl-sulfur-aryl, substituted or unsubstituted C2-C30 aryl-sulfone-aryl; the "substituted" here means replaced by one or more groups selected from the following groups: C1-C4 alkyl, C1-C4 haloalkyl, C1-C10 aryl-oxy.

[0010] Preferably, the bismaleimide compound is at least one selected from N,N'-(4,4'-methylenediphenyl)bismaleimide, N,N'-(1,4-phenylene)bismaleimide and N,N'-1,3-phenylenebismaleimide.

[0011] Preferably, in step (1), the structural formula of the 1-allyl-3-vinylimidazole halide salt is as follows:

[0012] Wherein, X=Cl, Br or I.

[0013] Preferably, the 1-allyl-3-vinylimidazole halide salt is at least one selected from 1-allyl-3-vinylimidazole bromide and 1-allyl-3-vinylimidazole chloride.

[0014] Preferably, in step (1), the molar ratio of the 1-allyl-3-vinylimidazole halide salt to the bismaleimide compound is 1:1-6; more preferably, the molar ratio of the 1-allyl-3-vinylimidazole halide salt to the bismaleimide compound is 1:1-4.

[0015] Preferably, in step (1), the polymerization reaction time is 18 to 24 hours.

[0016] Preferably, in step (1), the amount of solvent added is 1 to 34 times the mass of the 1-allyl-3-vinylimidazole halide salt; more preferably, the amount of solvent added is 26 to 34 times the mass of the 1-allyl-3-vinylimidazole halide salt.

[0017] Preferably, in step (1), the amount of the initiator added is 18-23% of the mass of the 1-allyl-3-vinylimidazole halide salt.

[0018] Preferably, in step (1), the solvent is at least one of N,N-dimethylformamide, tetrahydrofuran, acetone, 1,4-dioxane and ethyl acetate.

[0019] Preferably, in step (1), the initiator is at least one of azobisisobutyronitrile, azobisisoheptanenitrile, dimethyl azobisisobutyrate and benzoyl peroxide.

[0020] Preferably, in step (2), the crude imidazole-based polymerized ionic liquid is washed multiple times with ethyl acetate in the following manner: washing three times with 300-600 mL of ethyl acetate, each washing for 1-3 h, and the washing temperature is 30-60°C; more preferably, washing three times with 300-400 mL of ethyl acetate, each washing for 1 h-2 h, and the washing temperature is 40-60°C.

[0021] Preferably, in step (2), the vacuum drying temperature is 70-90° C., and the vacuum drying time is 12-24 h.

[0022] The use of the above-mentioned imidazole-based polymerized ionic liquid as a catalyst for the cycloaddition reaction of carbon dioxide and epoxide comprises the following steps: using carbon dioxide and epoxide as raw materials, the imidazole-based polymerized ionic liquid as a catalyst, reacting at a temperature of 30-120° C. and a pressure of 0.1-3 MPa for 2-12 h to synthesize a cyclic carbonate.

[0023] Preferably, the epoxy compound is at least one of ethylene oxide, propylene oxide butyl ether, propylene oxide, butylene oxide, epichlorohydrin, epibromohydrin and styrene oxide.

[0024] Preferably, the amount of the imidazole-based polymeric ionic liquid used is 0.5 to 5 mol% of the epoxy compound.

[0025] Compared with the prior art, the beneficial effects of this application include: The preparation process of the imidazole-based polymerized ionic liquid of the present invention is simple, the reaction steps are easy to operate, high temperature and high pressure conditions are not required, it meets the requirements of green chemical industry, and is suitable for industrial production. The imidazole-based polymerized ionic liquid prepared by the present invention is a green catalyst that can be used to catalyze the synthesis of cyclic carbonates from epoxy compounds and carbon dioxide. Specifically, the catalyst has an excellent catalytic effect, the selectivity can reach more than 98%, and the yield exceeds 95%. The reaction conditions are mild, and the catalytic synthesis of cyclic carbonates can be achieved at a temperature of 50°C. The pressure requirement is not high, and the catalytic reaction can be carried out at a lower pressure. The catalyst exists in the form of solid tiny particles, which is easy to fully contact with the reactants, thereby accelerating the reaction rate. After the catalytic reaction is completed, these solid particles can be easily recovered by simple physical filtration, avoiding the trouble of traditional heterogeneous catalysts that need to be recovered by complex distillation methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is the FT-IR spectrum of the imidazole-based polymeric ionic liquid prepared in Example 1.

[0027] Figure 2 This is the XPS electron energy spectrum of the imidazole-based polymeric ionic liquid prepared in Example 1. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solution and advantages of the present application more clear, the present application is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described here are only used to explain the present application and are not used to limit the present application.

[0029] Example 1 A method for preparing an imidazole-based polymeric ionic liquid comprises the following steps: 5.375 g of N,N'-(4,4'-methylenediphenyl)bismaleimide, 1.087 g of 1-allyl-3-vinylimidazole bromide and 0.196 g of 2,2-azobisisobutyronitrile were added to 30 mL of N,N-dimethylformamide and ultrasonically dissolved. Then, the mixture was transferred to a 50 mL polytetrafluoroethylene reaction tank and placed in a drying oven at 80° C. to react for 24 h to obtain a crude imidazole-based polymerized ionic liquid. The crude polymer was first washed three times with 300 mL of ethyl acetate at a washing temperature of 60° C.; then, the mixture was vacuum dried at 80° C. for 12 h to obtain the imidazole-based polymerized ionic liquid, which was referred to as imidazole-based polymerized ionic liquid a.

[0030] Example 2 5.375 g of N,N'-(4,4'-methylenediphenyl)bismaleimide, 0.853 g of 1-allyl-3-vinylimidazolium chloride and 0.196 g of 2,2-azobisisobutyronitrile were added to 30 mL of N,N-dimethylformamide and ultrasonically dissolved. Then, the mixture was transferred to a 50 mL polytetrafluoroethylene reaction tank and placed in a drying oven at 80° C. to react for 24 h to obtain a crude imidazole-based polymerized ionic liquid. The crude polymer was first washed three times with 300 mL of ethyl acetate at a washing temperature of 60° C.; then, the mixture was vacuum dried at 80° C. for 12 h to obtain the imidazole-based polymerized ionic liquid, which was recorded as imidazole-based polymerized ionic liquid b.

[0031] Example 3 A method for preparing a cyclic carbonate, comprising the following steps:

[0032] The catalyst imidazole-based polymerized ionic liquid a and ethylene oxide prepared in Example 1 were added into a 20 mL Schlenk tube in sequence, wherein 0.5 mL of ethylene oxide and the catalyst imidazole-based polymerized ionic liquid a accounted for 3 mol% of the molar content of ethylene oxide. When the temperature was stabilized to 50° C. by a temperature controller, a bladder filled with carbon dioxide was connected to the Schlenk tube, CO2 was introduced, and the reaction was carried out at a pressure of 0.1 MPa for 6 hours. The reaction was cooled to room temperature, the carbon dioxide bladder was removed for standby use, the catalyst was separated by filtration, and the product was quantitatively analyzed by gas chromatography. The selectivity of cyclic carbonate 2a was greater than or equal to 99%, and the yield was 85%.

[0033] Example 4 This example provides a method for preparing a cyclic carbonate, which is different from Example 3 in that the reaction time is changed to 12 h, and the yield of the product 2a is 99%, and the selectivity is greater than or equal to 99%.

[0034] Example 5 This embodiment provides a method for preparing a cyclic carbonate, which is different from that of embodiment 4 in that the catalyst is changed to imidazole-based polymeric ionic liquid b, and the yield of product 2a is 88%, and the selectivity is greater than or equal to 99%.

[0035] Example 6 This embodiment provides a method for preparing a cyclic carbonate, which is different from that of embodiment 4 in that the amount of imidazole-based polymeric ionic liquid a is changed to 2 mol% of ethylene oxide, and the yield of product 2a is 80%, and the selectivity is greater than or equal to 99%.

[0036] Example 7 A method for preparing a cyclic carbonate, comprising the following steps:

[0037] The catalyst imidazole-based polymerized ionic liquid a and epibromopropane prepared in Example 1 were added into a 20 mL Schlenk tube in sequence, wherein epibromopropane was 0.5 mL, and the catalyst imidazole-based polymerized ionic liquid a accounted for 3 mol% of the molar content of epibromopropane. When the temperature was controlled by a temperature controller to stabilize at 50°C, the ball filled with carbon dioxide was connected to the Schlenk tube, CO2 was introduced, and the reaction was carried out at a pressure of 0.1 MPa for 6 hours, and then cooled to room temperature. The carbon dioxide ball was removed for standby use, and the catalyst was separated by filtration. The product was quantitatively analyzed by gas chromatography, and the yield of cyclic carbonate 2b was 97%. The selectivity was greater than or equal to 99%.

[0038] Example 8 A method for preparing a cyclic carbonate, comprising the following steps:

[0039] The catalyst imidazole-based polymerized ionic liquid a and propylene oxide butyl ether prepared in Example 1 were added into a 20 mL Schlenk tube in sequence, wherein propylene oxide butyl ether was 0.5 mL, and the catalyst imidazole-based polymerized ionic liquid a accounted for 3 mol% of the molar content of propylene oxide butyl ether. When the temperature was controlled by a temperature controller to stabilize at 50°C, the ball bladder filled with carbon dioxide was connected to the Schlenk tube, CO2 was introduced, and the reaction was carried out at a pressure of 0.1 MPa for 6 hours, and then cooled to room temperature. The carbon dioxide ball bladder was removed for standby use, and the catalyst was separated by filtration. The product was quantitatively analyzed by gas chromatography, and the yield of cyclic carbonate 2c was 97%. The selectivity was greater than or equal to 99%.

[0040] Example 9 A method for preparing a cyclic carbonate, comprising the following steps:

[0041] The catalyst imidazole-based polymerized ionic liquid a and epoxystyrene prepared in Example 1 were added into a 20 mL Schlenk tube in sequence, wherein epoxystyrene 0.5 mL, the catalyst imidazole-based polymerized ionic liquid a accounted for 3 mol% of the molar content of epoxystyrene, and when the temperature was controlled by a temperature controller to stabilize at 50° C., the ball bladder filled with carbon dioxide was connected to the Schlenk tube, CO2 was introduced, and the reaction was carried out at a pressure of 0.1 MPa for 6 hours, and then cooled to room temperature, the carbon dioxide ball bladder was removed for standby use, and the catalyst was separated by filtration. The product was quantitatively analyzed by gas chromatography, and the yield of cyclic carbonate 2d was 98%. The selectivity was greater than or equal to 99%.

[0042] Example 10 The specific experimental conditions and steps were the same as those in Example 4. The imidazole-based polymeric ionic liquid a was recovered by centrifugation, then washed with ethyl acetate and dried. The recovered catalyst was used to perform 8 cycles under the same conditions. The results of the cycles are shown in Table 1.

[0043] Table 1 Experimental results of catalyst recycling in Example 10

[0044] From Table 1, we can see that the imidazole-based polymeric ionic liquid prepared in the present invention can be easily recovered through a simple filtration step, and after recovery, a cyclic catalytic experiment can be carried out, and its catalytic effect remains good.

[0045] Figure 1 This is the FT-IR spectrum of the imidazole-based polymeric ionic liquid prepared in Example 1. It can be seen from the figure that: 1701cm -1 、1654cm -1 、1511cm -1 、1388cm -1 The four obvious characteristic peaks are the stretching vibrations of the benzene ring, indicating that the polymer contains a large number of benzene ring structures. -1 There is an obvious absorption peak, which is caused by the NC stretching vibration of imidazole. The above results indicate that the imidazole-based polymeric ionic liquid was successfully synthesized.

[0046] Figure 2 This is the XPS electron spectrum of the imidazole-based polymeric ionic liquid prepared in Example 1. C1s, N 1s, O 1s, Br3p and Br3d peaks appear in the spectrum. The characteristic peak of N1 is clearly visible at 400ev, the characteristic peak of O1 is clearly visible at 532ev, and the characteristic peaks of Br3p and Br3d are 68ev and 181ev, respectively. The above test information shows that heteroatom nitrogen, oxygen and bromine anions have successfully functionalized the framework of the imidazole-based polymeric ionic liquid.

[0047] The specific implementation methods of the present application described above do not constitute a limitation on the protection scope of the present application. Any other corresponding changes and modifications made according to the technical concept of the present application should be included in the protection scope of the claims of the present application.

Claims

1. A class of imidazole-based polymeric ionic liquids, characterized in that: The structural formula is shown in Formula I: Formula I Wherein, X = Cl, Br or I; R is selected from the following groups: substituted or unsubstituted C1-30 alkyl, substituted or unsubstituted C1-30 aryl, substituted or unsubstituted C2-C30 aryl-alkyl, substituted or unsubstituted C3-C30 aryl-alkyl-aryl, substituted or unsubstituted C3-C30 aryl-carbonyl-aryl, substituted or unsubstituted C2-C30 aryl-oxy-aryl, substituted or unsubstituted C2-C30 aryl-thio-aryl, substituted or unsubstituted C2-C30 aryl-sulfone-aryl.

2. The method for preparing the imidazole-based polymeric ionic liquid according to claim 1, characterized in that: The steps include: (1) dispersing a bismaleimide compound and a 1-allyl-3-vinyl imidazole halide in a solvent, adding an initiator and performing a polymerization reaction at 65 to 85° C., and obtaining a crude imidazole-based polymerized ionic liquid after the reaction is completed; (2) The crude imidazole-based polymerized ionic liquid is washed with ethyl acetate for multiple times and then vacuum dried to obtain the imidazole-based polymerized ionic liquid.

3. The method for preparing the imidazole-based polymeric ionic liquid according to claim 2, characterized in that: The structural formula of the bismaleimide compound in step (1) is as follows: Wherein, the R1 is selected from the following groups: substituted or unsubstituted C1-30 alkyl, substituted or unsubstituted C1-30 aryl, substituted or unsubstituted C2-C30 aryl-alkyl, substituted or unsubstituted C3-C30 aryl-alkyl-aryl, substituted or unsubstituted C3-C30 aryl-carbonyl-aryl, substituted or unsubstituted C2-C30 aryl-oxy-aryl, substituted or unsubstituted C2-C30 aryl-sulfur-aryl, substituted or unsubstituted C2-C30 aryl-sulfone-aryl; the "substituted" refers to replacement by one or more groups selected from the following groups: C1-C4 alkyl, C1-C4 haloalkyl, C1-C10 aryl-oxy.

4. The method for preparing the imidazole-based polymeric ionic liquid according to claim 3, characterized in that: The structural formula of the 1-allyl-3-vinylimidazole halide salt in step (1) is as follows: Wherein, X=Cl, Br or I.

5. The method for preparing the imidazole-based polymeric ionic liquid according to claim 4, characterized in that: The bismaleimide compound is selected from at least one of N,N'-(4,4'-methylenediphenyl)bismaleimide, N,N'-(1,4-phenylene)bismaleimide and N,N'-1,3-phenylenebismaleimide; The 1-allyl-3-vinylimidazole halogenated salt is selected from at least one of 1-allyl-3-vinylimidazole bromide and 1-allyl-3-vinylimidazole chloride.

6. The method for preparing the imidazole-based polymeric ionic liquid according to claim 2, characterized in that: In step (1), the molar ratio of the 1-allyl-3-vinylimidazole halide to the bismaleimide compound is 1:1-6; The amount of the solvent added in step (1) is 1 to 34 times the mass of the 1-allyl-3-vinyl imidazole halide salt; The amount of the initiator added in step (1) is 18-23% of the mass of the 1-allyl-3-vinyl imidazole halide salt.

7. The method for preparing the imidazole-based polymeric ionic liquid according to claim 6, characterized in that: The molar ratio of 1-allyl-3-vinylimidazole halide salt to bismaleimide compound is 1:1-4; The amount of solvent added is 26 to 34 times the mass of 1-allyl-3-vinyl imidazole halide salt; The polymerization reaction time in step (1) is 18 to 24 hours; The vacuum drying temperature in step (2) is 70-90° C., and the vacuum drying time is 12-24 hours.

8. The method for preparing the imidazole-based polymeric ionic liquid according to claim 2, characterized in that: The solvent in step (1) is at least one of N,N-dimethylformamide, tetrahydrofuran, acetone, 1,4-dioxane and ethyl acetate; The initiator in step (1) is at least one of azobisisobutyronitrile, azobisisoheptanenitrile, dimethyl azobisisobutyrate and benzoyl peroxide; The method of washing the crude imidazole-based polymerized ionic liquid with ethyl acetate for multiple times in step (2) is as follows: washing with 300-600 mL of ethyl acetate for 3 times, each washing for 1-3 hours, and the washing temperature is 30-60°C.

9. Use of the imidazole-based polymeric ionic liquid according to claim 1 as a catalyst for the cycloaddition reaction of carbon dioxide and epoxide, characterized in that: The method comprises the following steps: using carbon dioxide and epoxy compounds as raw materials, using imidazole-based polymerized ionic liquid as a catalyst, reacting for 2 to 12 hours at a temperature of 30 to 120° C. and a pressure of 0.1 to 3 MPa to synthesize cyclic carbonate.

10. The use according to claim 9, characterized in that: The epoxy compound is at least one of ethylene oxide, propylene oxide butyl ether, propylene oxide, butylene oxide, epichlorohydrin, epibromohydrin and styrene oxide; The usage of the imidazole-based polymeric ionic liquid is 0.5-5 mol% of the epoxy compound.

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