Bipyridyl multifunctional ionic liquid as well as preparation method and application thereof

Abstract

The invention discloses a bipyridyl multifunctional ionic liquid as well as a preparation method and application thereof, and the bipyridyl multifunctional ionic liquid disclosed by the invention is respectively named as [C2H4] 2O [Py] 2ZnBr2Cl2, [C2H4] 2O [MeOPy] 2ZnBr2Cl2 and [C2H4] 2O [EOPy] 2ZnBr2Cl2. The invention also comprises a preparation method and application of the bipyridyl multifunctional ionic liquid. The cation of the bipyridyl multifunctional ionic liquid is a bipyridyl cation group with different ether groups, so that the bipyridyl multifunctional ionic liquid has the characteristics of lower price and better biodegradability and biocompatibility; zn metal has the characteristics of low toxicity and high abundance, and is suitable for constructing ionic liquid which is diversified in structure, low in price and environment-friendly; the catalyst is applied to preparation of cyclic carbonate through cycloaddition of CO2 and an epoxy substrate at normal temperature and pressure, CO2 catalytic conversion conditions of the catalyst are very mild, cheap, efficient and environment-friendly, the catalyst has the characteristic of green mimic enzyme catalytic conversion, additional solvents and auxiliaries can be avoided, energy consumption is low, and the production cost of cyclic carbonate can be greatly reduced.

Description

Technical Field

[0001] The invention relates to a multifunctional ionic liquid and a preparation method and application thereof, in particular to a bipyridine-based multifunctional ionic liquid and a preparation method and application thereof. Background Art

[0002] Global climate change caused by the greenhouse effect has become an important environmental issue that requires great attention. World industrialization and the extensive use of fossil fuels have led to a sharp increase in carbon dioxide concentrations. Therefore, the resulting global warming and climate change have become a serious challenge facing the world [Chemical Engineering Journal 493(2024)152345 and Nature Communications 15(2024)1-9]. Carbon capture and utilization (CCU) is an effective way to reduce carbon dioxide emissions into the atmosphere [Science of The Total Environment 948(2024)174873]. 2 It is a cheap and readily available C1 resource that can be used to catalyze the preparation of a variety of high value-added products, among which epoxides and CO 2 The process of cyclization to generate cyclic carbonates has 100% atom economy and has always attracted the attention of scientific researchers. As a highly soluble, low-toxic, green and biodegradable compound, cyclic carbonates have broad application prospects and can be widely used as polar aprotic solvents, lithium battery electrolytes, fuel additives, and chemical raw materials for the synthesis of dimethyl carbonate, polycarbonate and resins, etc., with broad market demand and high added value.

[0003] To date, homogeneous and heterogeneous catalytic systems such as ionic liquids, metal-organic frameworks, and polyionic liquids have been developed to generate cyclic carbonates. However, obtaining high yields of cyclic carbonates usually requires additional nucleophilic co-catalysts and harsh conditions such as high temperature and pressure. Summary of the invention

[0004] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a novel bipyridyl multifunctional ionic liquid and a preparation method and application thereof. The bipyridyl multifunctional ionic liquid can be used as a catalyst to prepare cyclic carbonates under very mild conditions of normal temperature and pressure.

[0005] Furthermore, the bipyridyl multifunctional ionic liquid can be used as a catalyst to prepare cyclic carbonate under very mild enzyme-like conditions at room temperature and pressure.

[0006] The technical solution adopted by the present invention to solve the technical problem is as follows:

[0007] The bipyridyl multifunctional ionic liquid of the present invention has any of the following three structural formulas:

[0008]

[0009] They are named [C 2 H 4 ] 2 O[Py] 2 ZnBr 2 Cl 2 , [C 2 H 4 ] 2 O[MeOPy] 2 ZnBr 2 Cl 2 and [C 2 H 4 ] 2 O[EOPy] 2 ZnBr 2 Cl 2 .

[0010] The preparation method of the bipyridine-based multifunctional ionic liquid of the present invention comprises the following steps: dissolving a pyridine compound in ethyl acetate under an inert atmosphere, stirring evenly, adding 2,2'-dibromodiethyl ether dropwise, refluxing at a certain temperature for a period of time, removing the ethyl acetate by reduced pressure distillation, adding an organic solvent with relatively low polarity, stirring, filtering, removing the organic solvent by reduced pressure distillation of the filtrate, and drying to obtain a bipyridine bromide salt; mixing the bipyridine bromide salt with ZnCl 2 The mixture is mixed and stirred at a certain temperature until a uniform viscous liquid is obtained; the obtained viscous liquid is dried to remove impurities, thereby obtaining a bipyridine-based multifunctional ionic liquid.

[0011] By adopting the above technical scheme, bipyridine-based multifunctional ionic liquids can be prepared, and the method is simple, low-cost, easy and controllable to operate, and easy to scale up.

[0012] Preferably, the pyridine compound is at least one of pyridine, 2-methoxypyridine or 2-ethoxypyridine.

[0013] Preferably, the molar ratio of the raw materials is pyridine compound: 2,2'-dibromodiethyl ether = 2-2.2: 1-1.1. Bispyridinium bromide: ZnCl 2 =1~1.05:1~1.05. By adopting the above technical solution, a higher yield can be obtained.

[0014] Preferably, after adding 2,2'-dibromodiethyl ether, the mixture is refluxed at 80-90° C. for 24-48 hours.

[0015] Preferably, the organic solvent with relatively low polarity is at least one of ethyl acetate, toluene, acetone and dichloromethane. By adopting the above technical solution, a better washing effect can be achieved.

[0016] Preferably, the inert atmosphere is a nitrogen atmosphere. The drying method adopted after the filtrate is distilled under reduced pressure to remove the organic solvent is vacuum drying. By adopting the above technical scheme, a better protection or drying effect can be obtained at a lower cost. It is also feasible to adopt other inert atmospheres or drying methods.

[0017] Preferably, the bipyridinium bromide is reacted with ZnCl 2 Mix and stir at 80-120°C for 20-30 hours until a uniform viscous liquid is obtained.

[0018] Preferably, the resulting viscous liquid is dried in an oven at 50-70°C overnight to remove impurities.

[0019] The application of the bipyridine-based multifunctional ionic liquid of the present invention as a catalyst for synthesizing cyclic carbonates from carbon dioxide and epoxides can greatly reduce the production cost of cyclic carbonates by adopting the above technical solution.

[0020] Preferably, the bipyridyl multifunctional ionic liquid is mixed with an epoxy compound as a catalyst, and the reaction is carried out for more than 24 hours (preferably 24 hours) under the conditions of a carbon dioxide pressure of 0.1 to 0.12 MPa and a temperature of 25 to 60° C.

[0021] By adopting the above technical solution, a better catalytic effect is achieved.

[0022] Preferably, the molar ratio of the bipyridyl multifunctional ionic liquid to the epoxy compound is 0.5-3.2%, more preferably 2.5-3.0%, that is, the amount of the bipyridyl multifunctional ionic liquid is equivalent to 0.5-3.2% of the amount of the epoxy compound.

[0023] By adopting the above technical solution, a better catalytic effect is achieved.

[0024] Preferably, the epoxy compound is at least one of epichlorohydrin, epibromohydrin, tert-butyl glycidyl ether, glycidyl phenyl ether and epoxystyrene.

[0025] By adopting the above technical solution, a better catalytic effect of producing cyclic carbonate is achieved. For other epoxy compounds with similar structures, the bipyridine-based multifunctional ionic liquid also has a good catalytic effect.

[0026] The present invention provides a method for preparing a novel ether-containing bipyridine-based multifunctional ionic liquid, which has the advantages of low toxicity, excellent biocompatibility and solubility, and easy biodegradation.2 The synthesis of cyclic carbonates by cycloaddition is in line with the requirements of green carbon science and sustainable development, which will be beneficial to improving the absorption and conversion of CO by ionic liquids. 2 Based on the versatility and rich designability of ether-functionalized ionic liquids, we have developed enzymes suitable for catalytic conversion of CO under normal temperature and pressure. 2 It is a new green ionic liquid catalytic material for high value-added cyclic carbonates, which overcomes the previous ionic liquid catalytic conversion of CO 2 The harsh conditions usually required have important scientific value and industrial application prospects.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] (1) The present invention provides a novel bipyridine Zn-based ionic liquid;

[0029] (2) The cation of the ionic liquid used in this method is a bipyridine group containing a diethyl ether group. The introduction of the ether group greatly increases the free volume between molecules, facilitates mass transfer between adjacent molecules, reduces the viscosity of the ionic liquid, and significantly increases its CO 2 At the same time, the Zn metal in the anion of the ionic liquid has the characteristics of high sustainability and low toxicity, which makes it easy to construct a new type of ionic liquid with diverse structures and low prices;

[0030] (3) Using a novel bipyridine-based multifunctional Zn-based ionic liquid with a unique structure as a new catalytic material for CO 2 Compared with conventional catalytic materials, the CO 2 The catalytic conversion conditions are simple, easy to control, and efficient, and no external solvents or additives are added. The reaction conditions are very mild (0.1-0.12MPa CO 2 pressure, 25-60 ° C), low energy consumption, thus greatly reducing the production cost of cyclic carbonates, and ionic liquids containing different side chains can significantly regulate the ether-functionalized ionic liquids to CO 2 The room-temperature and pressure enzyme conversion has important scientific value and industrial application prospects.

[0031] The cation of the bipyridyl multifunctional ionic liquid of the present invention is a bipyridyl cation group containing different ether groups. Compared with the common imidazole ionic liquid, it has the characteristics of lower price, better biodegradability and biocompatibility. Zn metal has the characteristics of low toxicity and high abundance, and is suitable for constructing ionic liquids with diverse structures, low prices and environmental friendliness. The novel bipyridyl multifunctional Zn-based ionic liquid with unique structure is used as a novel high-efficiency catalytic material for the reaction of CO at room temperature and pressure. 2The cyclic carbonate is prepared by cycloaddition with epoxy substrate. Compared with the conventional catalytic materials, the catalyst CO of the present invention is 2 The catalytic conversion conditions are very mild, inexpensive, efficient and environmentally friendly, and have the characteristics of green enzyme-like catalytic conversion. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 The bipyridyl multifunctional ionic liquid [C 2 H 4 ] 2 O[Py] 2 ZnBr 2 Cl 2 FT-IR graph of

[0033] Figure 2 The bipyridyl multifunctional ionic liquid [C 2 H 4 ] 2 O[Py] 2 ZnBr 2 Cl 2 of 1 HNMR spectra;

[0034] Figure 3 It is the chlorinated cyclic carbonate synthesized in Example 4 of the present invention. 1 H NMR spectra;

[0035] Figure 4 The bipyridine multifunctional ionic liquid [C 2 H 4 ] 2 O[Py] 2 ZnBr 2 Cl 2 Line graph showing the effect of dosage on catalytic epoxide cycloaddition;

[0036] Figure 5 The bipyridine multifunctional ionic liquid [C 2 H 4 ] 2 O[Py] 2 ZnBr 2 Cl 2 Line graph showing the effect of time on the catalytic epoxide cycloaddition reaction;

[0037] Figure 6 The brominated cyclic carbonate synthesized in Example 6 of the present invention 1 H NMR spectra. DETAILED DESCRIPTION

[0038] The present invention is further described below in conjunction with embodiments and drawings.

[0039] The raw materials used in the embodiments of the present invention are all obtained through conventional commercial channels.

[0040] Example 1

[0041] The bipyridine-based multifunctional ionic liquid catalyst prepared in this example has the following structural formula:

[0042] Use [C 2 H 4 ] 2 O[Py] 2 ZnBr 2 Cl 2 express.

[0043] This embodiment [C 2 H 4 ] 2 O[Py] 2 ZnBr 2 Cl 2 Preparation method of ionic liquid:

[0044] Under nitrogen protection, pyridine was dissolved in ethyl acetate, stirred evenly, 2,2'-dibromodiethyl ether was added dropwise, stirred and mixed evenly (in molar ratio, pyridine: 2,2'-dibromodiethyl ether = 2:1), refluxed at 80°C for 48h, ethyl acetate was removed by vacuum distillation, ethyl acetate was added for washing three times, stirred, the filtrate was vacuum distilled to remove the organic solvent, and dried at 80°C for 24h to obtain bipyridinium bromide; bipyridinium bromide ionic liquid was reacted with ZnCl 2 Mix and add to a round bottom flask (molar ratio, bispyridinium bromide: ZnCl 2 =1:1), stirred at 100°C for 24 hours until a uniform viscous liquid was obtained. The viscous liquid was dried in an oven at 60°C overnight to remove impurities, and a bipyridyl multifunctional ionic liquid [C 2 H 4 ] 2 O[Py] 2 ZnBr 2 Cl 2 .

[0045] Figure 1 The bipyridyl multifunctional ionic liquid [C 2 H 4 ] 2 O[Py] 2 ZnBr 2 Cl 2 FT-IR graph of

[0046] Figure 2The bipyridyl multifunctional ionic liquid [C 2 H 4 ] 2 O[Py] 2 ZnBr 2 Cl 2 of 1 HNMR spectrum.

[0047] Example 2

[0048] The bipyridine-based multifunctional ionic liquid catalyst prepared in this example has the following structural formula:

[0049] Use [C 2 H 4 ] 2 O[MeOPy] 2 ZnBr 2 Cl 2 express.

[0050] This embodiment [C 2 H 4 ] 2 O[MeOPy] 2 ZnBr 2 Cl 2 Preparation method of ionic liquid:

[0051] Under nitrogen protection, 2-methoxypyridine was dissolved in ethyl acetate, stirred evenly, 2,2'-dibromodiethyl ether was added dropwise and mixed evenly (in molar ratio, 2-methoxypyridine: 2,2'-dibromodiethyl ether = 2:1), refluxed at 80°C for 48h, ethyl acetate was removed by vacuum distillation, ethyl acetate was added for washing three times, stirred, the filtrate was vacuum distilled to remove the organic solvent, and dried at 80°C for 24h to obtain bipyridinium bromide; the bipyridinium bromide ionic liquid was reacted with ZnCl 2 Add the mixture to a round-bottom flask (molar ratio, bispyridinium bromide: ZnCl 2 =1:1), stirred at 100°C for 24 hours until a uniform viscous liquid was obtained. The viscous liquid was dried in an oven at 60°C overnight to remove impurities, and a bipyridyl multifunctional ionic liquid [C 2 H 4 ] 2 O[MeOPy] 2 ZnBr 2 Cl 2 .

[0052] Example 3

[0053] The bipyridine-based multifunctional ionic liquid catalyst prepared in this example has the following structural formula:

[0054] Use [C 2 H 4 ] 2 O[EOPy] 2 ZnBr 2 Cl 2 express.

[0055] This embodiment [C 2 H 4 ] 2 O[EOPy] 2 ZnBr 2 Cl 2 Preparation method of ionic liquid:

[0056] Under nitrogen protection, 2-ethoxypyridine is dissolved in ethyl acetate solution, stirred evenly, 2,2'-dibromodiethyl ether is added dropwise and mixed evenly (in molar ratio, 2-ethoxypyridine: 2,2'-dibromodiethyl ether = 2:1), refluxed at 80°C for 48h, ethyl acetate is removed by vacuum distillation, ethyl acetate is added for washing three times, stirred, the filtrate is vacuum distilled to remove the organic solvent, and dried at 80°C for 24h to obtain bipyridinium bromide; the bipyridinium bromide ionic liquid is mixed with ZnCl 2 Add the mixture to a round-bottom flask (molar ratio, bispyridinium bromide: ZnCl 2 =1:1), stirred at 100°C for 24 hours until a uniform viscous liquid was obtained. The viscous liquid was dried in an oven at 60°C overnight to remove impurities, and a bipyridyl multifunctional ionic liquid [C 2 H 4 ] 2 O[EOPy] 2 ZnBr 2 Cl 2 .

[0057] Example 4

[0058] Bispyridyl-based multifunctional ionic liquids[C 2 H 4 ] 2 O[Py] 2 ZnBr 2 Cl 2 , [C 2 H 4 ] 2 O[MeOPy] 2 ZnBr 2 Cl 2 and [C 2 H 4 ] 2 O[EOPy] 2 ZnBr 2 Cl2 Catalytic epoxide cycloaddition:

[0059] Bispyridyl multifunctional ionic liquid was used as a catalyst and epichlorohydrin was added into a 25 mL side-mouth flask. After mixing, 0.1 MPa CO was introduced. 2 , reacted at 25°C for 24h. The amount of catalyst added was 16mg (the amount of catalyst added was 3mol% of the amount of epichlorohydrin substance). After the reaction was completed, the selectivity and yield of cyclic carbonate were calculated, and the results are summarized in Table 1. The H NMR spectrum of the obtained product chlorocyclic carbonate was consistent with the theoretical value (such as Figure 3 ), proving that the pure target product was obtained.

[0060] Table 1 Effect of bipyridyl-based multifunctional ionic liquids on the synthesis of cyclic carbonates from carbon dioxide and epoxides

[0061]

[0062] Bipyridine Zn-based ionic liquids with different side chains on the pyridine group have good catalytic effects on the cycloaddition reaction of epoxy compounds; among them, the bipyridine Zn-based ionic liquid without side chains on the pyridine group [C 2 H 4 ] 2 O[Py] 2 ZnBr 2 Cl 2 Add epichlorohydrin and epichlorohydrin into a 25 mL side-mouth flask, mix and introduce 0.1 MPa CO 2 When the reaction was carried out at 25°C for 24 hours and the catalyst addition amount was 16 mg (3 mol%), the catalytic effect was optimal, providing a high yield (93%) and high selectivity (99%).

[0063] Example 5

[0064] Bipyridine multifunctional ionic liquids[C 2 H 4 ] 2 O[Py] 2 ZnBr 2 Cl 2 Further studies on catalytic epoxide cycloadditions:

[0065] (I) Effect of catalyst dosage on reaction

[0066] Add the catalyst and epichlorohydrin into a 25 mL side-mouth flask, mix and introduce 0.1 MPa CO 2 The amount of catalyst added was 10, 12, 14, 16, 18 mg (1.5-3.5 mol%), the reaction temperature was 25°C, and the reaction time was 24 h. After the reaction was completed, the selectivity and yield of the chlorocyclic carbonate were calculated. The results are as follows Figure 4 As shown, when the catalyst dosage increases from 10 mg to 16 mg, the catalyst active sites increase, and the yield of chlorocyclic carbonate increases from 89% to 93%. When the catalyst dosage is further increased, the yield and selectivity show a downward trend. Excessive catalyst dosage will cause mass transfer difficulties, which is not conducive to the reaction.

[0067] (II) Effect of reaction time on reaction

[0068] Add the catalyst and epichlorohydrin into a 25 mL side-mouth flask, mix and introduce 0.1 MPa CO 2 The reaction time is 18-28h and the reaction temperature is 25°C. The amount of catalyst added is 16mg (3mol%). After the reaction is completed, the selectivity and yield of the chlorocyclic carbonate are calculated. The results are as follows: Figure 5 As shown, within the reaction time of 18 to 24 hours, the yield of chlorocyclic carbonate has been significantly improved (89% to 93%). As the main reaction proceeds more and more deeply, the selectivity of chlorocyclic carbonate has also been improved (97% to 99%). When the reaction time exceeds 26 hours, the conversion rate and selectivity do not change significantly, indicating that the reaction is almost completed within 26 hours, and the yield and selectivity are 94% and 97% respectively.

[0069] In summary, bipyridine multifunctional ionic liquids [C 2 H 4 ] 2 O[Py] 2 ZnBr 2 Cl 2 Catalyze the cycloaddition of epoxides, preferably by adding the catalyst and epichlorohydrin into a 25 mL side-mouth flask, mixing and then passing 0.1 MPa CO 2 , 25°C, reaction time 26h, catalyst addition amount 16mg (3mol%), the yield of the obtained product chlorocyclic carbonate reached 94%, and the hydrogen nuclear magnetic resonance spectrum was consistent with the theoretical value, proving that the pure target product was obtained.

[0070] Example 6

[0071] Bipyridine multifunctional ionic liquids[C 2 H 4 ] 2 O[Py] 2 ZnBr 2 Cl 2 Catalysis of cycloaddition of different epoxides: The catalyst [C 2 H 4 ] 2 O[Py] 2 ZnBr 2 Cl 2and epoxide were added to a 25 mL side-mouth flask, mixed, and then introduced into a 0.1 MPa CO 2 The catalyst was added in an amount of 16 mg (3 mol%). The reaction was carried out at 25-60°C for 26 h, and the selectivity and yield of the cyclic carbonate were calculated. The results are summarized in Table 3. The H NMR spectrum of the synthesized bromocyclic carbonate is shown in Figure 6 shown.

[0072] Table 3 Bipyridyl-based multifunctional ionic liquids [C 2 H 4 ] 2 O[Py] 2 ZnBr 2 Cl 2 Catalytic effect of different epoxide cycloadditions

[0073]

Claims

1. A bipyridyl multifunctional ionic liquid, characterized in that: Has any of the following structural formulas:

2. The method for preparing the bipyridyl multifunctional ionic liquid according to claim 1, characterized in that: The method comprises the following steps: dissolving a pyridine compound in ethyl acetate under an inert atmosphere, stirring evenly, adding 2,2'-dibromodiethyl ether dropwise, refluxing at a certain temperature for a period of time, removing the ethyl acetate by reduced pressure distillation, adding an organic solvent with a relatively low polarity, stirring, filtering, removing the organic solvent by reduced pressure distillation of the filtrate, and drying to obtain a bipyridinium bromide salt; mixing the bipyridinium bromide salt with ZnCl2, stirring at a certain temperature until a uniform viscous liquid is obtained; and drying the obtained viscous liquid to remove impurities to obtain a bipyridyl-based multifunctional ionic liquid.

3. The method for preparing a bipyridyl multifunctional ionic liquid according to claim 2, characterized in that: The pyridine compound is at least one of pyridine, 2-methoxypyridine or 2-ethoxypyridine.

4. The method for preparing a bipyridyl multifunctional ionic liquid according to claim 2 or 3, characterized in that: The molar ratio of the raw materials is: pyridine compound: 2,2'-dibromodiethyl ether = 2-2.2: 1-1.

1. Bispyridinium bromide: ZnCl2 = 1-1.05: 1-1.

05.

5. The method for preparing a bipyridyl multifunctional ionic liquid according to claim 2 or 3, characterized in that: After adding 2,2'-dibromodiethyl ether, reflux the mixture at 80-90°C for 24-48 hours.

6. The method for preparing a bipyridyl multifunctional ionic liquid according to claim 2 or 3, characterized in that: The organic solvent with relatively low polarity is at least one of ethyl acetate, toluene, acetone and dichloromethane.

7. The method for preparing a bipyridyl multifunctional ionic liquid according to claim 2 or 3, characterized in that: The inert atmosphere is a nitrogen atmosphere; and / or, the drying method adopted after the filtrate is distilled under reduced pressure to remove the organic solvent is vacuum drying; and / or, the bipyridinium bromide is mixed with ZnCl2 and stirred at 80-100°C for 20-30 hours until a uniform viscous liquid is obtained; and / or, the obtained viscous liquid is dried in an oven at 50-70°C overnight to remove impurities.

8. Use of the bipyridyl multifunctional ionic liquid according to claim 1 or the bipyridyl multifunctional ionic liquid prepared by the preparation method of the bipyridyl multifunctional ionic liquid according to any one of claims 2 to 7, characterized in that: As a catalyst for the synthesis of cyclic carbonates from carbon dioxide and epoxides.

9. The use of the bipyridyl-based multifunctional ionic liquid according to claim 8, characterized in that: The bipyridyl multifunctional ionic liquid is used as a catalyst and mixed with an epoxy compound, and reacted for more than 24 hours under the conditions of a carbon dioxide pressure of 0.1 to 0.12 MPa and a temperature of 25 to 60° C.

10. The use of the bipyridyl multifunctional ionic liquid according to claim 8 or 9, characterized in that: The molar ratio of the bipyridyl multifunctional ionic liquid to the epoxy compound is 0.5-3.2%; and / or the epoxy compound is at least one of epichlorohydrin, epibromohydrin, tert-butyl glycidyl ether, glycidyl phenyl ether, and epoxystyrene.

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