A method for preparing a copolymer for catalyzing the cycloaddition reaction of carbon dioxide and epoxides

Abstract

The present invention discloses a preparation method of a copolymer for catalyzing the cycloaddition reaction of carbon dioxide and epoxide. The copolymer is a copolymer of acrylic acid and 1-vinylimidazole. The preparation method includes: under magnetic stirring, dropping the aqueous phase into the oil phase and heating and keeping the emulsion warm; wherein the aqueous phase includes acrylic acid, 1-vinylimidazole and water, and the oil phase includes liquid paraffin and an emulsifier; adding azobisisobutyronitrile to the emulsion and carrying out the reaction under insulation; after the reaction is completed, cooling to room temperature, centrifuging, washing, and then freeze-drying to remove the residual solvent and water to obtain the copolymer. The copolymer prepared by the present invention contains imidazole groups and a cross-linked network that can stably exist and swell in an organic solvent, and can be used as a heterogeneous catalyst to carry out the cycloaddition reaction of carbon dioxide and epoxide to generate cyclic carbonate without adding a cocatalyst and an organic solvent.

Description

Technical Field

[0001] The present invention relates to the technical field of organic synthesis, and particularly relates to a preparation method of a copolymer for catalyzing the cycloaddition reaction of carbon dioxide and epoxides. Background Art

[0002] In recent years, the emission of CO2 has had a serious impact on the global ecological environment. Therefore, it is urgent to reduce CO2 emissions. Through the carbon dioxide capture and utilization (CCU) technology, CO2 can be captured, enriched and converted into more valuable chemical products. There are two chemical conversion methods for CO2: reduction method and non-reduction method; under certain catalysts and other conditions, reduction conversion is the conversion of CO2 into CO, methane, methanol, formic acid, etc.; non-reduction conversion refers to the formation of esters, ureas, carboxylic acids, etc. by CO2 and other molecules under certain conditions. In terms of non-reduction reaction conversion, as early as 1969, Inoue (Advanced Functional Materials 2018, 28(10), 16.) et al. discovered the copolymerization reaction of CO2 and epoxides, which has rapidly developed the non-reduction conversion of CO2. The reaction of CO2 and epoxides generates cyclic carbonates, and this route is a 100% atom-economic reaction process. Cyclic carbonates are widely used in the pharmaceutical and chemical industries. It is not only a good organic solvent, but also has good applications in the preparation of other chemical raw materials and intermediates. Similarly, CO2 and epoxides can copolymerize to produce polycarbonates, which also have a wide range of uses. In recent years, Charlotte Williams et al. (Nature 2016, 540(7633), 354-362.) have reported many studies on this route. Cyclic carbonates are produced by the cycloaddition of CO2 and epoxides. The epoxides selected as substrates generally include propylene oxide (PO), styrene oxide (SO), epichlorohydrin (ECH), etc., and the reaction generates cyclic carbonates such as propylene carbonate (PC), chloropropyl carbonate (CPC), etc.

[0003] Catalysts and epoxides have different effects on the rate and products of the CO2 cycloaddition reaction. By adjusting the reaction rate of the catalyst to an appropriate range, different epoxides have different reaction activities for the CO2 cycloaddition reaction, and the selectivity of the reaction of CO2 and epoxides (i.e., cyclic carbonates and polycarbonates) is carried out simultaneously under the influence of catalysts, epoxides and reaction conditions. Therefore, the main topic in the field of CO2 conversion to cyclic carbonates is the design and development of the entire catalytic system. Currently, the development trend of the catalytic system is to require high efficiency and selectivity, good stability and recyclability under mild conditions, and the catalytic process does not require cocatalysts and volatile organic solvents, and the catalyst itself is cheap and easy to obtain and easy to synthesize.

[0004] In the past decade, quite a number of homogeneous or heterogeneous catalysts for the addition reaction of CO2 with epoxides have been reported, including ionic liquids, metal halides, metal-organic frameworks, porous organic polymers, metal-organic complexes, ammonium halides, phosphorus halides, imidazole halides, N-heterocyclic carbenes, and hybrid catalysts, etc. (ChemSusChem 2015, 8(15), 2436-2454.) (Journal of CO2 Utilization 2023, 68, 16.). The vast majority of catalysts often contain metal cations used as hydrogen bond donors and halide anions used for nucleophilic attack on the ring-opening of epoxides. Although these catalytic systems have excellent catalytic activity, they often have problems such as the need for cocatalysts or organic solvents, the metal active centers or halides being toxic and harmful to the environment, and the catalyst preparation being complex and expensive. Therefore, it is very important to develop efficient green catalysts that are metal-free, halide-free, and easy to prepare.

[0005] Hydrogen bond donor (HBD) groups (such as -NH2, -OH, -COOH) can coordinate with the O of the epoxide to form hydrogen bonds, polarize the C-O of the epoxide, and thus promote the ring-opening of the epoxide. Therefore, catalytic systems containing HBD groups can effectively replace catalyst systems containing metal ions and halides. Dai et al. compared the catalytic performance of hydroxyl, carboxyl, and amino-functionalized phosphonium ionic liquids (FPBILs) for the addition reaction of CO2 with epoxides, and the results showed that the catalyst with carboxyl functionalization had higher catalytic activity (Catalysis Letters 2010, 137(1-2), 74-80.). However, simple HBDs without nucleophilic groups cannot be used as catalysts for CO2 and epoxides because they lack the nucleophilic attack activity required for the epoxide ring-opening process. N-heterocyclic carbene (NHC) has a very strong electron-donating ability, shows strong nucleophilicity and Lewis basicity, and can be used as a nucleophile to promote the ring-opening of epoxides and the activation of CO2. Zhong et al. prepared a novel metal-free, halide-free catalyst MFN-KUST for the cycloaddition reaction of CO2 (Fuel 2022, 326, 15.). The catalyst was prepared by polycondensation of 2,5-FDCA rich in -COOH and N-heterocyclic carbene MA, showed excellent catalytic performance under solvent-free and cocatalyst-free conditions, and the promotion effect of MA on the ring-opening of epoxides was explained by DFT calculations.

[0006] Acrylic acid (AA) has abundant -COOH groups and can be used as an HBD to polarize epoxides and assist in ring-opening. 1-Vinylimidazole (VI) as an N-heterocyclic carbene can promote the ring-opening of epoxides and the activation of CO2. The synergistic effect of the two can be used as a metal-free and halide-free catalyst for the cycloaddition reaction of CO2 and epoxides. Currently, AA and VI are mostly formed into hydrogels by solution copolymerization (Macromolecules 2018, 51(20), 8136 - 8146.) or form composites by complexing with metal ions (Journal of Colloid and Interface Science 2013, 396, 1 - 8.), neither of which can meet the requirements of the cycloaddition reaction of CO2 and epoxides for the catalyst. Summary of the Invention

[0007] In view of the above limitations in the application of the cycloaddition reaction of CO2 and epoxides, in order to further improve the catalytic activity of metal-free and halide-free catalysts, while maintaining obvious advantages such as low price, simple synthesis, and non-toxicity, the present invention provides a preparation method of a copolymer P(AA-co-VI) for catalyzing the cycloaddition reaction of carbon dioxide and epoxides.

[0008] The present invention discloses a preparation method of a copolymer for catalyzing the cycloaddition reaction of carbon dioxide and epoxides. The copolymer is a copolymer of acrylic acid and 1-vinylimidazole. The preparation method includes:

[0009] Step 1: Under magnetic stirring, the aqueous phase is dropped into the oil phase, and the emulsion is heated and kept warm. Among them, the aqueous phase includes acrylic acid, 1-vinylimidazole, and water, and the oil phase includes liquid paraffin and an emulsifier.

[0010] Step 2: Add azobisisobutyronitrile to the emulsion and keep warm for reaction.

[0011] Step 3: After the reaction is completed, it is cooled to room temperature, centrifuged, washed, and then freeze-dried to remove the residual solvent and water to obtain the copolymer.

[0012] As a further improvement of the present invention, in the step 1, by weight, the aqueous phase is 30 - 40 parts, and the oil phase is 60 - 70 parts.

[0013] In the aqueous phase, the acrylic acid is 6 - 10 parts, the 1-vinylimidazole is 0 - 10 parts and not taking 0 part, and the water is 24 - 40 parts. Preferably, the mass ratio of acrylic acid to water is 1:4.

[0014] In the oil phase, the liquid paraffin is 58 - 68 parts, and the emulsifier is 1 - 2 parts.

[0015] As a further improvement of the present invention, the emulsifier is composed of a mixture of Span 80 and Tween 80. By weight, Span 80 is 70-80 parts, and Tween 80 is 20-30 parts.

[0016] As a further improvement of the present invention, in step 1, the rate of magnetic stirring is 300-500 rpm, the emulsion is heated to 65-75 °C, and purged with nitrogen, and kept warm for at least 30 min.

[0017] As a further improvement of the present invention, in step 2, the azobisisobutyronitrile is used as an initiator, and the added mass is 0.3-0.5 wt% of the mass of the copolymer monomers; after adding the azobisisobutyronitrile, the reaction is carried out at 65-75 °C for 4-7 h with heat preservation.

[0018] As a further improvement of the present invention, in step 2, the azobisisobutyronitrile is refined, and its refining method includes:

[0019] The azobisisobutyronitrile is added to a methanol solution and stirred to dissolve, and then filtered after heating in an oil bath;

[0020] The filtrate is placed in an ice-water bath to cool and precipitate needle-shaped crystals, and then filtered;

[0021] The crystals obtained by filtration are dried to obtain refined azobisisobutyronitrile.

[0022] As a further improvement of the present invention, in step 3, the centrifugal separation is to keep the sedimentation particles at least for 30 min at a speed lower than 6000 rpm, and the washing is carried out with n-hexane and water.

[0023] As a further improvement of the present invention, it further includes:

[0024] Step 4, adding an epoxide and a copolymer into a high-pressure reactor, and introducing CO2 for reaction; after the reaction is completed, the reactor is taken out and cooled in an ice-water bath, and the product is analyzed by 1 1H nuclear magnetic resonance spectroscopy.

[0025] As a further improvement of the present invention, in step 4, the mass ratio of the epoxide to the copolymer as a catalyst is 65:1, and the pressure of introducing CO2 is 0.1-2 MPa.

[0026] As a further improvement of the present invention, in step 4, a thermostatic heating magnetic stirrer with heat collection is used to raise the reaction temperature to no higher than 120 °C, and keep warm for 0.1-24 h.

[0027] Compared with the prior art, the beneficial effects of the present invention are:

[0028] The present invention can successfully prepare a copolymer P(AA-co-VI) for catalyzing the cycloaddition reaction of carbon dioxide and epoxides. It contains imidazole groups and a cross-linked network that can stably exist and swell in organic solvents, and can be used as a heterogeneous catalyst. Without adding a cocatalyst and organic solvent, the cycloaddition reaction of carbon dioxide and epoxides can be carried out to generate cyclic carbonates. At the same time, the catalyst prepared by this method has obvious advantages such as high activity, low price, simple synthesis, and non-toxicity, and shows strong potential in the cycloaddition reaction of CO2 and epoxides. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a flow chart of the preparation method of the copolymer for catalyzing the cycloaddition reaction of carbon dioxide and epoxides disclosed in the present invention;

[0030] Figure 2 It is a SEM image of the copolymer P(AA-co-VI) prepared in Example 1 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0031] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0032] The following further describes the present invention in detail with reference to the accompanying drawings:

[0033] As Figure 1 shown, the present invention provides a preparation method of a copolymer P(AA-co-VI) for catalyzing the cycloaddition reaction of carbon dioxide and epoxides. The copolymer is obtained by copolymerizing 1-vinylimidazole (VI) and acrylic acid (AA) using the inverse emulsion method. The preparation method includes:

[0034] Step 1: Under magnetic stirring, the aqueous phase is dropped into the oil phase, and the emulsion is heated and kept warm; wherein,

[0035] By weight, the aqueous phase is 30-40 parts, and the oil phase is 60-70 parts;

[0036] By weight, the aqueous phase includes 6-10 parts of acrylic acid (AA), 0-10 parts of 1-vinylimidazole (VI) and not taking 0 part, that is, greater than 0 part and less than or equal to 10 parts; water is 24-40 parts; preferably, acrylic acid is 10 parts, 1-vinylimidazole is 1-10 parts, and water is 40 parts

[0037] By weight, the oil phase includes 58 - 68 parts of liquid paraffin and 1 - 2 parts of emulsifier. Preferably, it is 68 parts of liquid paraffin and 2 parts of emulsifier. Further, the emulsifier is composed of a mixture of Span 80 and Tween 80. By weight, Span 80 is 70 - 80 parts and Tween 80 is 20 - 30 parts. Preferably, Span 80 is 75 parts and Tween 80 is 25 parts.

[0038] The rate of magnetic stirring is 300 - 500 rpm. The emulsion is heated to 65 - 75 °C and purged with nitrogen, and kept warm for at least 30 min.

[0039] Step 2: Add azobisisobutyronitrile to the emulsion in Step 1 and continue to keep warm for reaction; wherein,

[0040] Azobisisobutyronitrile is used as an initiator, and its added mass is 0.3 - 0.5 wt% of the mass of the polymer monomer, preferably 0.5 wt%. After adding azobisisobutyronitrile, keep warm at 65 - 75 °C for 4 - 7 h for reaction;

[0041] Azobisisobutyronitrile is refined, and its refining method includes:

[0042] Add azobisisobutyronitrile (AIBN) to a methanol solution and stir to dissolve it. After heating in an oil bath, filter it; place the filtrate in an ice - water bath to cool and precipitate needle - shaped crystals, and then filter; dry the filtered crystals to obtain refined azobisisobutyronitrile.

[0043] The specific refining method is as follows: Weigh 5 g of AIBN and add it to 50 mL of methanol solution, stir quickly to dissolve it. Heat it in an oil bath at 50 °C for 10 min, then quickly filter while it is hot to remove insoluble substances. Then place the obtained filtrate in an ice - water bath to cool for 30 min to precipitate needle - shaped crystals. Then dry the filtered crystals with an oil pump and dry them at room temperature in a desiccator for 24 h. Finally, store the refined AIBN in a refrigerator at low temperature and seal it.

[0044] Step 3: After the reaction is completed, cool to room temperature, centrifuge, wash, and then freeze - dry to remove residual solvents and water to obtain a copolymer; wherein,

[0045] Centrifugation is to keep the sedimented particles at least for 30 min at a speed lower than 6000 rpm;

[0046] Washing is to wash with n - hexane and water.

[0047] Step 4: Add an epoxide and the copolymer into a high - pressure reactor, introduce CO2 for reaction; after the reaction is completed, take out the reactor and cool it in an ice - water bath. The product is used 1Analyzed by \(^1H\) nuclear magnetic resonance spectroscopy; among them,

[0048] The mass ratio of the epoxide to the copolymer as the catalyst is 65:1, and the pressure of \(CO_2\) introduced is 0.1 - 2 MPa;

[0049] Using a thermostatic heating magnetic stirrer with heat collection, the reaction temperature is raised to no higher than 120 °C and kept warm for 0.1 - 24 h.

[0050] The preparation principle of the present invention is:

[0051] In the present invention, 1-vinylimidazole (VI) and acrylic acid (AA) are copolymerized by the inverse emulsion method to prepare a copolymer P(AA-co-VI) for catalyzing the cycloaddition reaction of carbon dioxide and epoxide. The key of this preparation method lies in the catalytic activity of the imidazole group and the cross-linked network that can stably exist and swell in organic solvents. The copolymer P(AA-co-VI) can stably exist in the epoxide as a heterogeneous catalyst, and at the same time, the epoxide can be absorbed into the polymer network to increase the contact between the reactants and the catalytic active intermediate, thus showing excellent catalytic activity.

[0052] Example 1

[0053] The present invention provides a preparation method of a copolymer P(AA-co-VI) for catalyzing the cycloaddition reaction of carbon dioxide and epoxide, including:

[0054] S11. Prepare the aqueous phase and oil phase required for the inverse emulsion method: The oil phase is composed of 34.0000 g of liquid paraffin and 1.0000 g of emulsifier. The emulsifier is composed of 0.7500 g of Span 80 and 0.2500 g of Tween 80; the aqueous phase is composed of 3.0000 g of acrylic acid (AA), 0.6000 g of 1-vinylimidazole (VI), and 12.0000 g of water;

[0055] S12. Under magnetic stirring at 300 rpm, slowly drop the aqueous phase into the oil phase, heat the emulsion to 65 °C, and purge with nitrogen, and keep warm for 30 min;

[0056] S13. Subsequently, add 0.0180 g of refined azobisisobutyronitrile (AIBN), which is 0.5% of the polymer monomer mass; and keep warm at 65 °C for 4 h;

[0057] S14. After the reaction is completed and cooled to room temperature, through centrifugal separation, first keep the sedimentation particles at 5000 rpm for 30 min, then wash with n-hexane and water, and then freeze-dry to remove the residual solvent and water to obtain P(AA-co-VI); among them, the SEM diagram of the prepared copolymer P(AA-co-VI) is as Figure 2 shown;

[0058] S15. Add 2 mL of epichlorohydrin and 0.0300 g of P(AA-co-VI) into a high-pressure reactor, introduce CO2 with a pressure of 0.5 MPa, heat it up to 120 °C by a heating magnetic stirrer with a heat collecting type constant temperature, and keep it warm for 6 h. After the reaction is completed, take out the reactor and cool it in ice water. The product is analyzed by 1 1H nuclear magnetic resonance spectroscopy using deuterated chloroform as the solvent.

[0059] Example 2

[0060] The present invention provides a preparation method of a copolymer P(AA-co-VI) for catalyzing the cycloaddition reaction of carbon dioxide and epoxide, including:

[0061] S21. Prepare the aqueous phase and the oil phase required for the inverse emulsion method: The oil phase consists of 34.0000 g of liquid paraffin and 1.0000 g of emulsifier, and the emulsifier is composed of 0.7500 g of Span 80 and 0.2500 g of Tween 80; the aqueous phase consists of 3.0000 g of acrylic acid (AA), 0.3000 g of 1-vinylimidazole (VI), and 12.0000 g of water;

[0062] S22. Under magnetic stirring at 300 rpm, slowly drop the aqueous phase into the oil phase, heat the emulsion to 65 °C, and purge it with nitrogen, and keep it warm for 30 min;

[0063] S23. Subsequently, add 0.0165 g of refined azobisisobutyronitrile (AIBN), and keep it warm at 65 °C for 4 h;

[0064] S24. After the reaction is completed and cooled to room temperature, through centrifugal separation, first keep the sedimented particles at 5000 rpm for 30 min, then wash them with n-hexane and water, and then freeze-dry to remove the residual solvent and water to obtain P(AA-co-VI);

[0065] S25. Add 2 mL of epichlorohydrin and 0.0300 g of P(AA-co-VI) into a high-pressure reactor, introduce CO2 with a pressure of 0.5 MPa, heat it up to 120 °C by a heating magnetic stirrer with a heat collecting type constant temperature, and keep it warm for 6 h. After the reaction is completed, take out the reactor and cool it in ice water. The product is analyzed by 1 1H nuclear magnetic resonance spectroscopy using deuterated chloroform as the solvent.

[0066] Example 3

[0067] The present invention provides a preparation method of a copolymer P(AA-co-VI) for catalyzing the cycloaddition reaction of carbon dioxide and epoxide, including:

[0068] S31. Prepare the aqueous phase and the oil phase required for the inverse emulsion method: The oil phase consists of 34.0000 g of liquid paraffin and 1.0000 g of emulsifier, and the emulsifier is composed of a mixture of 0.7500 g of Span 80 and 0.2500 g of Tween 80; the aqueous phase consists of 3.0000 g of acrylic acid (AA), 0.9000 g of 1-vinylimidazole (VI), and 12.0000 g of water.

[0069] S32. Under magnetic stirring at 300 rpm, slowly add the aqueous phase to the oil phase, heat the emulsion to 65 °C, purge with nitrogen, and keep warm for 30 min.

[0070] S33. Subsequently, add 0.0195 g of refined azobisisobutyronitrile (AIBN), and keep warm at 65 °C for 4 h.

[0071] S34. After the reaction is completed and cooled to room temperature, through centrifugal separation, first keep the sedimented particles at 5000 rpm for 30 min, then wash with n-hexane and water, and then freeze-dry to remove the residual solvent and water to obtain P(AA-co-VI).

[0072] S35. Add 2 mL of epichlorohydrin and 0.0300 g of P(AA-co-VI) into the high-pressure reactor, introduce CO2, the pressure is 0.5 MPa, heat up to 120 °C through a heating magnetic stirrer with a heat collection type constant temperature, and keep warm for 6 h. After the reaction is completed, take out the reactor and cool it in ice water. The product is analyzed by 1 1H nuclear magnetic resonance spectroscopy using deuterated chloroform as the solvent.

[0073] Example 4

[0074] The present invention provides a preparation method of a copolymer P(AA-co-VI) for catalyzing the cycloaddition reaction of carbon dioxide and epoxide, including:

[0075] S41. Prepare the aqueous phase and the oil phase required for the inverse emulsion method: The oil phase consists of 34.0000 g of liquid paraffin and 1.0000 g of emulsifier, and the emulsifier is composed of a mixture of 0.7500 g of Span 80 and 0.2500 g of Tween 80; the aqueous phase consists of 3.0000 g of acrylic acid (AA), 1.2000 g of 1-vinylimidazole (VI), and 12.0000 g of water.

[0076] S42. Under magnetic stirring at 300 rpm, slowly add the aqueous phase to the oil phase, heat the emulsion to 65 °C, purge with nitrogen, and keep warm for 30 min.

[0077] S43. Subsequently, 0.0210 g of refined azobisisobutyronitrile (AIBN) was added and the mixture was kept at 65 °C for 4 h;

[0078] S44. After the reaction was completed, the reaction mixture was cooled to room temperature. Then, by centrifugation, the sedimentation of particles was first maintained at 5000 rpm for 30 min, followed by washing with n - hexane and water, and then freeze - drying to remove the residual solvent and water, obtaining P(AA - co - VI);

[0079] S45. 2 mL of epichlorohydrin and 0.0300 g of P(AA - co - VI) were added into a high - pressure reactor. CO2 was introduced with a pressure of 0.5 MPa. The temperature was raised to 120 °C by a heating magnetic stirrer with a collecting - heat type constant temperature, and the mixture was kept at this temperature for 6 h. After the reaction was completed, the reactor was taken out and cooled in ice water. The product was analyzed by 1 1H nuclear magnetic resonance spectroscopy using deuterated chloroform as the solvent.

[0080] Example 5

[0081] The present invention provides a preparation method of a copolymer P(AA - co - VI) for catalyzing the cycloaddition reaction of carbon dioxide and epoxide, comprising:

[0082] S51. Prepare the aqueous phase and the oil phase required for the inverse emulsion method: The oil phase consists of 34.0000 g of liquid paraffin and 1.0000 g of emulsifier. The emulsifier is composed of a mixture of 0.7500 g of Span 80 and 0.2500 g of Tween 80; the aqueous phase consists of 3.0000 g of acrylic acid (AA), 1.5000 g of 1 - vinylimidazole (VI), and 12.0000 g of water;

[0083] S52. Under magnetic stirring at 300 rpm, the aqueous phase was slowly added dropwise to the oil phase, and the emulsion was heated to 65 °C and purged with nitrogen, and kept at this temperature for 30 min;

[0084] S53. Subsequently, 0.0225 g of refined azobisisobutyronitrile (AIBN) was added and the mixture was kept at 65 °C for 4 h;

[0085] S54. After the reaction was completed, the reaction mixture was cooled to room temperature. Then, by centrifugation, the sedimentation of particles was first maintained at 5000 rpm for 30 min, followed by washing with n - hexane and water, and then freeze - drying to remove the residual solvent and water, obtaining P(AA - co - VI);

[0086] S55. Add 2 mL of epichlorohydrin and 0.0300 g of P(AA-co-VI) into a high-pressure reactor, introduce CO2 with a pressure of 0.5 MPa, heat it to 120 °C by a collecting heat type constant temperature heating magnetic stirrer, and keep it warm for 6 h. After the reaction is completed, take out the reactor and cool it in ice water. The product is analyzed by 1 1H nuclear magnetic resonance spectroscopy, using deuterated chloroform as the solvent.

[0087] Example 6

[0088] The present invention provides a preparation method of a copolymer P(AA-co-VI) for catalyzing the cycloaddition reaction of carbon dioxide and epoxide, including:

[0089] S61. Prepare the aqueous phase and oil phase required for the reverse emulsion method: the oil phase consists of 34.0000 g of liquid paraffin and 1.0000 g of emulsifier, and the emulsifier is composed of 0.7500 g of Span 80 and 0.2500 g of Tween 80; the aqueous phase consists of 3.0000 g of acrylic acid (AA), 0.6000 g of 1-vinylimidazole (VI), and 12.0000 g of water;

[0090] S62. Under magnetic stirring at 300 rpm, slowly drop the aqueous phase into the oil phase, heat the emulsion to 65 °C, and purge it with nitrogen, then keep it warm for 30 min;

[0091] S63. Subsequently, add 0.0180 g of refined azobisisobutyronitrile (AIBN), and keep it warm at 65 °C for 4 h;

[0092] S64. After the reaction is completed and cooled to room temperature, through centrifugal separation, first keep the sedimented particles at 5000 rpm for 30 min, then wash them with n-hexane and water, and then freeze-dry to remove the residual solvent and water to obtain P(AA-co-VI);

[0093] S65. Add 2 mL of epichlorohydrin and 0.0300 g of P(AA-co-VI) into a high-pressure reactor, introduce CO2 with a pressure of 0.1 MPa, heat it to 120 °C by a collecting heat type constant temperature heating magnetic stirrer, and keep it warm for 12 h. After the reaction is completed, take out the reactor and cool it in ice water. The product is analyzed by 1 1H nuclear magnetic resonance spectroscopy, using deuterated chloroform as the solvent.

[0094] Example 7

[0095] The present invention provides a preparation method of a copolymer P(AA-co-VI) for catalyzing the cycloaddition reaction of carbon dioxide and epoxide, including:

[0096] S71. Prepare the aqueous phase and the oil phase required for the inverse emulsion method: The oil phase consists of 34.0000 g of liquid paraffin and 1.0000 g of emulsifier, and the emulsifier is composed of a mixture of 0.7500 g of Span 80 and 0.2500 g of Tween 80; the aqueous phase consists of 3.0000 g of acrylic acid (AA), 0.6000 g of 1-vinylimidazole (VI), and 12.0000 g of water;

[0097] S72. Under magnetic stirring at 300 rpm, slowly add the aqueous phase to the oil phase, heat the emulsion to 65 °C, purge with nitrogen, and keep it warm for 30 min;

[0098] S73. Subsequently, add 0.0180 g of refined azobisisobutyronitrile (AIBN), and keep it warm at 65 °C for 4 h;

[0099] S74. After the reaction is completed and cooled to room temperature, by centrifugal separation, first keep the sedimented particles at 5000 rpm for 30 min, then wash with n-hexane and water, and then freeze-dry to remove the residual solvent and water to obtain P(AA-co-VI);

[0100] S75. Add 2 mL of epichlorohydrin and 0.0300 g of P(AA-co-VI) into a high-pressure reactor, introduce CO2, with a pressure of 1.0 MPa, heat up to 120 °C by a heating magnetic stirrer with a heat-collecting type constant temperature, and keep it warm for 6 h. After the reaction is completed, take out the reactor and cool it in ice water. The product is analyzed by 1 1H nuclear magnetic resonance spectroscopy, using deuterated chloroform as the solvent.

[0101] Example 8

[0102] The present invention provides a preparation method of a copolymer P(AA-co-VI) for catalyzing the cycloaddition reaction of carbon dioxide and epoxide, including:

[0103] S81. Prepare the aqueous phase and the oil phase required for the inverse emulsion method: The oil phase consists of 34.0000 g of liquid paraffin and 1.0000 g of emulsifier, and the emulsifier is composed of a mixture of 0.7500 g of Span 80 and 0.2500 g of Tween 80; the aqueous phase consists of 3.0000 g of acrylic acid (AA), 0.6000 g of 1-vinylimidazole (VI), and 12.0000 g of water;

[0104] S82. Under magnetic stirring at 300 rpm, slowly add the aqueous phase to the oil phase, heat the emulsion to 65 °C, purge with nitrogen, and keep it warm for 30 min;

[0105] S83. Subsequently, 0.0180 g of refined azobisisobutyronitrile (AIBN) was added and the mixture was kept at 65 °C for 4 h;

[0106] S84. After the reaction was completed and cooled to room temperature, by centrifugation, the sedimentation particles should first be kept at 5000 rpm for 30 min, then washed with n - hexane and water, and then freeze - dried to remove the residual solvent and water, obtaining P(AA - co - VI);

[0107] S85. 2 mL of glycidyl phenyl ether and 0.0300 g of P(AA - co - VI) were added into a high - pressure reactor, CO2 was introduced, the pressure was 0.5 MPa, and the temperature was raised to 120 °C by a heating magnetic stirrer with heat collection and constant temperature, and kept for 6 h. After the reaction was completed, the reactor was taken out and cooled in ice water. The product was analyzed by 1 1H nuclear magnetic resonance spectroscopy using deuterated chloroform as the solvent.

[0108] Example 9

[0109] The present invention provides a preparation method of a copolymer P(AA - co - VI) for catalyzing the cycloaddition reaction of carbon dioxide and epoxide, including:

[0110] S91. Prepare the aqueous phase and oil phase required for the inverse emulsion method: The oil phase consists of 34.0000 g of liquid paraffin and 1.0000 g of emulsifier, and the emulsifier is composed of 0.7500 g of Span 80 and 0.2500 g of Tween 80; the aqueous phase consists of 3.0000 g of acrylic acid (AA), 0.6000 g of 1 - vinylimidazole (VI), and 12.0000 g of water;

[0111] S92. Under magnetic stirring at 300 rpm, the aqueous phase was slowly dropped into the oil phase, and the emulsion was heated to 65 °C and purged with nitrogen, and kept for 30 min;

[0112] S93. Subsequently, 0.0180 g of refined azobisisobutyronitrile (AIBN) was added and the mixture was kept at 65 °C for 4 h;

[0113] S94. After the reaction was completed and cooled to room temperature, by centrifugation, the sedimentation particles should first be kept at 5000 rpm for 30 min, then washed with n - hexane and water, and then freeze - dried to remove the residual solvent and water, obtaining P(AA - co - VI);

[0114] S95. Add 2 mL of cyclohexene oxide and 0.0300 g of P(AA-co-VI) into a high-pressure reactor. Introduce CO2 with a pressure of 1.0 MPa. Heat it up to 120 °C by a thermostatic heating magnetic stirrer with a heat collecting device and keep it warm for 6 h. After the reaction is completed, take out the reactor and cool it in ice water. The product is analyzed by 1 1H nuclear magnetic resonance spectroscopy using deuterated chloroform as the solvent.

[0115] Example 10

[0116] The present invention provides a preparation method of a copolymer P(AA-co-VI) for catalyzing the cycloaddition reaction of carbon dioxide and epoxides, including:

[0117] S101. Prepare the aqueous phase and the oil phase required for the reverse emulsion method: The oil phase consists of 34.0000 g of liquid paraffin and 1.0000 g of an emulsifier, and the emulsifier is composed of a mixture of 0.7500 g of Span 80 and 0.2500 g of Tween 80; the aqueous phase consists of 3.0000 g of acrylic acid (AA), 0.6000 g of 1-vinylimidazole (VI), and 12.0000 g of water.

[0118] S102. Under magnetic stirring at 300 rpm, slowly drop the aqueous phase into the oil phase, heat the emulsion to 65 °C, and purge it with nitrogen, then keep it warm for 30 min.

[0119] S103. Subsequently, add 0.0180 g of refined azobisisobutyronitrile (AIBN) and keep it warm at 65 °C for 4 h.

[0120] S104. After the reaction is completed and cooled to room temperature, through centrifugal separation, first keep the sedimented particles at 5000 rpm for 30 min, then wash them with n-hexane and water, and then freeze-dry to remove the residual solvent and water to obtain P(AA-co-VI).

[0121] S105. Add 2 mL of propylene oxide and 0.0300 g of P(AA-co-VI) into a high-pressure reactor. Introduce CO2 with a pressure of 0.5 MPa. Heat it up to 120 °C by a thermostatic heating magnetic stirrer with a heat collecting device and keep it warm for 6 h. After the reaction is completed, take out the reactor and cool it in ice water. The product is analyzed by 1 1H nuclear magnetic resonance spectroscopy using deuterated chloroform as the solvent.

[0122] The advantages of the present invention are:

[0123] The present invention can successfully prepare a copolymer P(AA-co-VI) for catalyzing the cycloaddition reaction of carbon dioxide and epoxides. It contains imidazole groups and a cross-linked network that can stably exist and swell in organic solvents, and can be used as a heterogeneous catalyst. Without adding a cocatalyst and an organic solvent, the cycloaddition reaction of carbon dioxide and epoxides can be carried out to generate cyclic carbonates. At the same time, the catalyst prepared by this method has obvious advantages such as high activity, low price, simple synthesis, and non-toxicity, and shows strong potential in the cycloaddition reaction of CO2 and epoxides.

[0124] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, various changes and modifications can be made to the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A preparation method of a copolymer for catalyzing the cycloaddition reaction of carbon dioxide and epoxide, the copolymer being a copolymer of acrylic acid and 1-vinylimidazole; characterized in that, The preparation method includes: Step 1: Under magnetic stirring, the aqueous phase is dropped into the oil phase, and the emulsion is heated and kept warm; wherein, the aqueous phase includes acrylic acid, 1-vinylimidazole and water, and the oil phase includes liquid paraffin and an emulsifier; by weight, the aqueous phase is 30-40 parts, and the oil phase is 60-70 parts; in the aqueous phase, the acrylic acid is 6-10 parts, the 1-vinylimidazole is 0-10 parts and not taking 0 part, and the water is 24-40 parts; in the oil phase, the liquid paraffin is 58-68 parts, and the emulsifier is 1-2 parts. Step 2: Add azobisisobutyronitrile to the emulsion and keep warm for reaction. Step 3: After the reaction is completed, cool to room temperature, carry out centrifugal separation, washing, and then freeze-dry to remove residual solvents and water to obtain a copolymer.

2. The method for preparing the copolymer according to claim 1, wherein The emulsifier is composed of a mixture of Span 80 and Tween 80. By weight, Span 80 is 70-80 parts, and Tween 80 is 20-30 parts.

3. The method for preparing the copolymer according to claim 1, wherein, In Step 1, the rate of magnetic stirring is 300-500 rpm, the emulsion is heated to 65-75 °C, and purged with nitrogen, and kept warm for at least 30 min.

4. The preparation method of the copolymer according to claim 1, characterized in that In Step 2, the azobisisobutyronitrile is used as an initiator, and its added mass is 0.3-0.5 wt% of the mass of the copolymer monomers; after adding azobisisobutyronitrile, keep warm at 65-75 °C for 4-7 h for reaction.

5. The method for preparing the copolymer according to claim 1 or 4, characterized in that, In Step 2, the azobisisobutyronitrile is refined, and its refining method includes: Add azobisisobutyronitrile to a methanol solution, stir to dissolve, heat in an oil bath and then filter. Place the filtrate in an ice-water bath to cool and precipitate needle-shaped crystals, and filter. Dry the crystals obtained by filtration to obtain refined azobisisobutyronitrile.

6. The preparation method of the copolymer according to claim 1, characterized in that, In Step 3, the centrifugal separation is to keep the sedimentation particles at least for 30 min at a speed lower than 6000 rpm, and the washing is to wash with n-hexane and water.

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