Catalyst for catalyzing carbon dioxide cycloaddition reaction, and preparation method therefor

Abstract

A catalyst for catalyzing a carbon dioxide cycloaddition reaction, and a preparation method therefor. The structural formula of the catalyst is as follows, wherein polycore is a polystyrene inner core, polyshellis a polyp-chloromethyl styrene outer shell, CationN+ is a nitrogen-containing cation group; and AnionO- is an anion group containing a phenoloxy group, wherein the structural formula of the anion group containing an phenoloxy group is as follows, wherein R3is any one of hydrogen, hydroxyl, methoxyl, amido, nitryl and chlorine. The prepared catalyst is easy to recycle, and has good stability and good catalytic effect.

Description

Catalysts for catalyzing the cycloaddition reaction of carbon dioxide and their preparation methods Technical Field

[0001] This invention belongs to the field of carbon dioxide cycloaddition reaction technology, specifically relating to a catalyst for catalyzing carbon dioxide cycloaddition reactions and its preparation method. Background Technology

[0002] Cyclic carbonates are an important class of chemical products with wide applications and promising prospects in lithium-ion battery electrolytes, biodegradable polymer monomers, and organic synthesis intermediates. Industrially, cyclic carbonates are synthesized through a cycloaddition reaction between carbon dioxide and epoxides. Current processes use metal halides and ammonium salts as catalysts, operating at temperatures of 100-150°C and pressures of 2.0-5.0 MPa. However, both metal halides and ammonium salts contain halide anions, which cause severe corrosion to metal equipment under high temperature and pressure conditions, placing high demands on the reactor material. Furthermore, metal halides and ammonium salts are homogeneous catalysts, making catalyst recovery difficult.

[0003] In view of this, the present invention is hereby proposed. Summary of the Invention

[0004] The first objective of this invention is to provide a catalyst for catalyzing the cycloaddition reaction of carbon dioxide, which is easier to recover, has better stability, and better catalytic effect than existing catalysts for catalyzing the cycloaddition reaction of carbon dioxide.

[0005] The second objective of this invention is to provide a method for preparing a catalyst for catalyzing the cycloaddition reaction of carbon dioxide, which can produce a catalyst with good catalytic effect and easy recovery.

[0006] A third objective of this invention is to provide a method for carbon dioxide cycloaddition reaction, which uses the above-mentioned catalyst to catalyze the cycloaddition reaction of carbon dioxide gas and epoxide compound, resulting in high reaction efficiency and reduced requirements for carbon dioxide purity, thus improving the economics of the cycloaddition reaction.

[0007] To achieve the above-mentioned objectives of this invention, the following technical solution is adopted: This invention provides a catalyst for catalyzing the cycloaddition reaction of carbon dioxide, the catalyst having the following structural formula: Among them, poly core For polystyrene core, poly shell For the polychloromethylstyrene shell, Cation N + indicates a nitrogen-containing cationic group; Anion O - is a phenolic oxygen-containing anionic group; wherein, the structural formula of the phenolic oxygen-containing anionic group is: R3 can be any one of hydrogen, hydroxyl, methoxy, amino, nitro, or chlorine.

[0008] The catalyst provided by this invention, compared to catalysts composed of metal halides and ammonium salts used in related technologies, is easier to recover, has better stability, and exhibits better catalytic performance. This is because the catalyst of this invention uses polystyrene and poly(p-chloromethylstyrene) as monomers to synthesize a polymer support with a core-shell structure, and synthesizes nitrogen-containing cationic groups and phenolic anionic groups on the basis of the polymer support. Specifically, the polystyrene core layer has strong mechanical stability. By using polystyrene as the core, this invention ensures that the catalyst is not easily broken during the reaction, which facilitates the recovery of the catalyst after the reaction. By polymerizing another layer of poly(p-chloromethylstyrene) as a shell on the outer layer of polystyrene, the chloromethyl groups contained in the shell can be fully utilized to react with various nitrogen-containing compounds to generate nitrogen-containing cationic groups, thereby improving the stability of the grafted nitrogen-containing cationic groups. By grafting nitrogen-containing cationic groups, on the one hand, the amine groups of the nitrogen-containing cationic groups can absorb CO2 molecules, thereby improving the catalyst's CO2 absorption capacity and CO2 utilization rate. This ensures that the cycloaddition reaction still has good reaction selectivity and conversion rate under low concentration carbon dioxide conditions, and is beneficial for catalytic reactions under lower pressure conditions. On the other hand, nitrogen-containing cation groups can act as cations, forming ionic bonds with phenolic oxide-containing anionic groups to immobilize the phenolic oxide-containing anionic groups on the polymer material surface, thereby further improving the overall structural stability of the catalyst. The immobilized phenolic oxide-containing anionic groups can activate CO2 molecules to form active carbonates, effectively reducing the activation energy of CO2 molecule conversion. This helps improve the catalytic effect on cycloaddition reactions, thus contributing to increased reaction efficiency. Therefore, the present invention, by employing a specific core and shell and grafting specific groups, results in a catalyst with excellent catalytic performance. Furthermore, due to its stable overall structure and simple recovery, applying this catalyst to cycloaddition reactions can effectively reduce the cost of cycloaddition reactions and help lower the requirements for reaction conditions (including CO2 gas purity and reaction pressure), thereby improving the reaction selectivity and conversion rate of cycloaddition reactions.

[0009] Preferably, the nitrogen-containing cationic group is any one of the following groups: sodium hydroxide choline cationic group, quaternary ammonium cationic group, or guanidine compound cationic group; preferably, the nitrogen-containing cationic group is a guanidine compound cationic group.

[0010] Preferably, the nitrogen-containing cation group is a sodium hydroxide choline cation group, and the structural formula of the sodium hydroxide choline cation group is:

[0011] Preferably, the nitrogen-containing cationic group is a quaternary ammonium cationic group, and the structural formula of the quaternary ammonium cationic group is: Where R1 is C 2～4 Alkyl groups.

[0012] Preferably, the nitrogen-containing cationic group is a guanidine compound cationic group, specifically a guanidine group, and the structural formula of the guanidine group is: R2 is methyl or tert-butyl.

[0013] In this scheme, a guanidino cationic group is used as the nitrogen-containing cationic group grafted onto the poly(p-chloromethylstyrene) shell. Compared with sodium hydroxide choline cationic groups and quaternary ammonium cationic groups, the guanidino cationic group contains more amine groups. Using it as a nitrogen-containing cationic group can further improve the catalyst's ability to absorb CO2, thereby further reducing the purity requirements of carbon dioxide gas in the cycloaddition reaction.

[0014] Preferably, the guanidine cationic group is 2-methyl-1,1,3,3-tetramethylguanidine, and the structural formula of 2-methyl-1,1,3,3-tetramethylguanidine is:

[0015] In this embodiment, R2 is a methyl group. The nitrogen-containing cationic group used in this embodiment can further improve the catalyst's ability to absorb CO2, thus exhibiting good catalytic activity even under lower reaction pressure conditions.

[0016] Preferably, R3 is a nitro group, and the phenolic oxygen-containing anionic group is an o-nitrophenol anionic group, the structural formula of which is:

[0017] In this embodiment, by making R3 a nitro group, the electron cloud density of the phenoxy anion can be appropriately reduced, thus appropriately reducing the nucleophilicity of the phenoxy anion. Applying the catalyst of this embodiment to a cycloaddition reaction makes it easier for carbonate species generated after CO2 activation to transfer, thereby promoting the formation of cyclic carbonates.

[0018] Preferably, the nitrogen-containing cationic group is 2-methyl-1,1,3,3-tetramethylguanidine, the phenolic oxygen-containing anionic group is o-nitrophenol anionic group, and the structural formula of the catalyst is:

[0019] In this embodiment, the catalyst uses polystyrene and poly(p-chloromethylstyrene) monomers to synthesize a core-shell structured polymer support. Based on this polymer support, nitrogen-containing cationic groups and phenolic oxide-containing anionic groups are synthesized. The nitrogen-containing cationic group is 2-methyl-1,1,3,3-tetramethylguanidine, and the phenolic oxide-containing anionic group is o-nitrophenol. This structure allows for the full utilization of the mechanical stability of the polystyrene core layer, improving the overall stability of the catalyst and facilitating catalyst recovery after the reaction, thus reducing reaction costs. Furthermore, the chloromethyl groups in poly(p-chloromethylstyrene) support the nitrogen-containing cationic groups, further enhancing the overall stability of the catalyst. Additionally, by using 2-methyl-1,1,3,3-tetramethylguanidine as the nitrogen-containing cationic group, the multiple amine groups on this group enhance the catalyst's CO2 absorption capacity and utilization rate. This ensures good selectivity and conversion rates in the cycloaddition reaction even under low-concentration carbon dioxide conditions and facilitates catalytic reactions under lower pressures. On the other hand, this scheme, by employing the o-nitrophenol anion group as the phenoxy group, can activate CO2 molecules to form active carbonates. This effectively lowers the activation energy for CO2 molecule conversion. Furthermore, the nitro group on the o-nitrophenol anion group can appropriately reduce the electron cloud density and nucleophilicity of the phenoxy anion, making it easier for the carbonate species formed after CO2 activation to transfer. This helps improve the selectivity and conversion rate of the cycloaddition reaction. In summary, the catalyst in this scheme has a stable overall structure and is easy to recover. Applying this catalyst to cycloaddition reactions can effectively improve the selectivity and conversion rate of the cycloaddition reaction.

[0020] Preferably, the polystyrene core has the following structural formula:

[0021] In the present invention, the core of the catalyst is made of polystyrene. Polystyrene is inexpensive and has a good mechanical structure. The preparation cost of using a polystyrene core is controllable and can ensure good structural stability.

[0022] Preferably, the structural formula of the poly(p-chloromethylstyrene) shell is:

[0023] It is understandable that the polystyrene core itself is very stable in physical and chemical properties, making it difficult to directly graft other chemical groups onto it. Therefore, in this invention, by polymerizing a layer of poly(p-chloromethylstyrene) on the outer layer of polystyrene, the shell layer contains a relatively reactive group, chloromethyl, which can react with various nitrogen-containing compounds to generate nitrogen-containing cationic groups, thereby improving the stability of the grafted nitrogen-containing cationic groups.

[0024] The present invention also provides a method for preparing the catalyst of the above embodiments, the method comprising: dispersing polystyrene microspheres in an organic solvent containing p-chloromethylstyrene monomer; adding an initiator and an emulsifier to the organic solvent to obtain a mixed solution; heating the mixed solution to carry out a seed emulsion polymerization reaction to form core-shell microspheres; reacting the core-shell microspheres with a nitrogen-containing cationic compound in anhydrous ethanol to graft nitrogen-containing cationic groups onto the core-shell microspheres; adding a phenolic anionic compound and the core-shell microspheres to the organic solvent, and stirring the organic solvent to graft phenolic anionic groups onto the core-shell microspheres.

[0025] The present invention also provides a method for carbon dioxide cycloaddition reaction, wherein the method uses the catalyst described in any of the above embodiments, and uses carbon dioxide gas and epoxide as raw materials to carry out a cycloaddition reaction to generate cyclic carbonates.

[0026] Preferably, the amount of catalyst used is 0.05-2 wt% of the amount of epoxide compound. More preferably, the amount of catalyst used is 0.2-1 wt% of the amount of epoxide compound. It is understood that too low a catalyst amount will result in a slow reaction rate, while too high a catalyst amount will cause catalyst particles to agglomerate in the reaction solution, offering no significant help in increasing the reaction rate and significantly increasing production costs. The solution in this embodiment, by rationally selecting the ratio of catalyst to epoxide compound based on the properties of the catalyst itself, can reduce catalyst waste while ensuring the efficiency of the cycloaddition reaction, which helps to further reduce production costs.

[0027] Preferably, the purity of the carbon dioxide gas is 20%-99%. It is understood that in related technologies, to ensure reaction efficiency, the purity of carbon dioxide gas is usually required to be relatively high (e.g., above 60%) during cycloaddition reactions. However, in the embodiments of this invention, a specific catalyst is used to improve the absorption capacity of CO2, thereby improving the utilization rate of CO2, ensuring good reaction efficiency even when the purity of the carbon dioxide gas is low. Therefore, the solution of this invention can use carbon dioxide gas with lower purity as a gas source during cycloaddition reactions, which can expand the range of gaseous raw materials used in cycloaddition reactions and reduce reaction costs. Simultaneously, since the carbon dioxide purity of some coal-fired flue gas in related technologies can reach 20%, this invention can directly use coal-fired flue gas as carbon dioxide gas during cycloaddition reactions, which can further reduce the reaction cost of cycloaddition reactions and has the advantages of being green and environmentally friendly.

[0028] Preferably, the purity of the carbon dioxide gas is 30%-99%. In this embodiment, considering that too low a purity of carbon dioxide gas may lead to a low gas phase diffusion coefficient, carbon dioxide gas with a purity of more than 30% is selected as the gas phase raw material to ensure reaction efficiency.

[0029] Preferably, the epoxy compound is any one of ethylene oxide, propylene oxide, epichlorohydrin, and epiphenylene oxide.

[0030] Preferably, the reaction pressure of the cycloaddition reaction is 0.1-3 MPa. More preferably, the reaction pressure of the cycloaddition reaction is 0.5-2 MPa. As described above, applying the catalyst described in the above embodiments to the cycloaddition reaction can improve the utilization rate of CO2. Therefore, during the cycloaddition reaction, the reaction pressure can be reduced to 0.5-2 MPa, thereby helping to reduce the requirements for the reaction site (which may be called the reactor) and thus helping to reduce the reaction cost.

[0031] Preferably, the reaction temperature of the cycloaddition reaction is in the range of 70–110°C. Preferably, the reaction temperature of the cycloaddition reaction is in the range of 80–100°C.

[0032] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The catalyst of the present invention has good stability, which can reduce the difficulty of catalyst recovery after reaction, thereby helping to reduce reaction cost; (2) The catalyst of the present invention has good CO2 absorption capacity. Applying the catalyst to the cycloaddition reaction can improve the utilization rate of CO2 and reduce the requirements of the cycloaddition reaction on the reaction conditions, so that the cycloaddition reaction can still ensure good reaction selectivity and reaction conversion rate under low concentration carbon dioxide and low pressure conditions. Attached Figure Description

[0033] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings: Figure 1 is an infrared spectrum of the catalyst provided in Example 1 of the present invention; Figure 2 is an electron spectrum of the catalyst provided in Example 1 of the present invention. Detailed Implementation

[0034] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings and specific embodiments. However, those skilled in the art will understand that the embodiments described below are some embodiments of the present invention, but not all embodiments, and are only used to illustrate the present invention, and should not be regarded as limiting the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0035] To more clearly illustrate the technical solutions in this invention, specific embodiments are described below.

[0036] Example 1 In this example, the structural formula of the catalyst is: The chemical formula is PS-TMG-PhNO2. The infrared spectrum of this catalyst is shown in Figure 1. The electronic energy spectrum of this catalyst is shown in Figure 2.

[0037] The catalyst was prepared as follows: First, 50g of polystyrene microspheres were dispersed in a 20% THF solvent containing p-chloromethylstyrene monomer, with a total mass of 50g of the monomer. Then, 0.2g of initiator AIBN and 1g of emulsifier SDS were added to the organic solvent to obtain a mixed solution. The mixed solution was heated to 55°C to carry out a seed emulsion polymerization reaction, forming core-shell microspheres. The core-shell microspheres were reacted with 10g of 2-methyl-1,1,3,3-tetramethylguanidine compound in anhydrous ethanol to graft nitrogen-containing cationic groups onto the core-shell microspheres. 10g of o-nitrophenol anionic compound and the core-shell microspheres were added to the organic solvent and stirred at 40°C for 20h to graft phenolic anionic groups onto the core-shell microspheres. After the reaction was completed, the reaction product was purified by centrifugation, washing, and drying to obtain the catalyst of this embodiment.

[0038] The carbon dioxide cycloaddition reaction method in this embodiment is as follows: 20 ml of propylene oxide containing 0.5 wt% catalyst (PS-TMG-PhNO2) was added to a 50 ml glass reactor. After purging with 99% carbon dioxide gas three times, the temperature was raised to 90°C with stirring. The reaction was carried out at this temperature with stirring for 4 hours, during which carbon dioxide gas was continuously introduced while maintaining the reactor pressure at 1.5 MPa. After the reaction was completed, the gas supply was stopped and the reactor was cooled to room temperature. Samples were taken for analysis. The results showed that the propylene oxide conversion rate (i.e., reaction conversion rate) was 98.5%, and the propylene carbonate selectivity (i.e., reaction selectivity) was 99.5%. The infrared spectrum and electron spectra of the catalyst (PS-TMG-PhNO2) used in this embodiment are shown in Figures 1-2.

[0039] Example 2 The difference between this example and Example 1 lies in the nitrogen-containing cationic group of the catalyst used. In this example, the nitrogen-containing cationic group of the catalyst is a sodium hydroxide choline cationic group.

[0040] The carbon dioxide cycloaddition reaction method described in Example 1 was used, but the catalyst was changed to one with a nitrogen-containing cation group of sodium hydroxide choline in this example. After the reaction was completed, samples were taken for analysis. The results showed that the propylene oxide conversion rate was 85.2%, and the propylene carbonate selectivity was 98.6%.

[0041] Example 3. The difference between this example and Example 1 lies in the nitrogen-containing cationic group of the catalyst used. In this example, the nitrogen-containing cationic group of the catalyst is a quaternary ammonium cationic group, specifically a tetraethylammonium cationic group.

[0042] The carbon dioxide cycloaddition reaction method described in Example 1 was used, but the catalyst was changed to a catalyst with a nitrogen-containing cationic group of tetraethylammonium in this example. After the reaction was completed, samples were taken for analysis. The results showed that the propylene oxide conversion rate was 82.4%, and the propylene carbonate selectivity was 97.8%.

[0043] Example 4. The difference between this example and Example 1 lies in the different R3 of the catalyst containing the phenolic anionic group. In this example, R3 is hydrogen (H).

[0044] The carbon dioxide cycloaddition reaction method described in Example 1 was used, with the catalyst changed to that used in this example. After the reaction was complete, samples were taken for analysis. The results showed that the propylene oxide conversion rate was 90.6%, and the propylene carbonate selectivity was 99.2%.

[0045] Example 5. The difference between this example and Example 1 lies in the different R3 of the catalyst containing the phenolic anionic group. In this example, R3 is a hydroxyl group (OH).

[0046] The carbon dioxide cycloaddition reaction method described in Example 1 was used, with the catalyst changed to that used in this example. After the reaction was complete, samples were taken for analysis. The results showed that the propylene oxide conversion rate was 86.7%, and the propylene carbonate selectivity was 98.7%.

[0047] Example 6. The difference between this example and Example 1 lies in the different R3 of the catalyst containing the phenolic anionic group. In this example, R3 is methoxy (OCH3).

[0048] The carbon dioxide cycloaddition reaction method described in Example 1 was used, with the catalyst changed to that used in this example. After the reaction was complete, samples were taken for analysis. The results showed that the propylene oxide conversion rate was 82.5%, and the propylene carbonate selectivity was 97.5%.

[0049] Example 7. The difference between this example and Example 1 lies in the different R3 group containing the phenolic oxide anion group in the catalyst used. In this example, R3 is an amino group (NH2).

[0050] The carbon dioxide cycloaddition reaction method described in Example 1 was used, with the catalyst changed to that used in this example. After the reaction was complete, samples were taken for analysis. The results showed that the propylene oxide conversion rate was 93.4%, and the propylene carbonate selectivity was 98.2%.

[0051] Example 8. The difference between this example and Example 1 lies in the different R3 of the catalyst containing the phenolic anionic group. In this example, R3 is chlorine.

[0052] The carbon dioxide cycloaddition reaction method described in Example 1 was used, with the catalyst changed to that used in this example. After the reaction was complete, samples were taken for analysis. The results showed that the propylene oxide conversion rate was 91.3%, and the propylene carbonate selectivity was 99.1%.

[0053] Example 9. The carbon dioxide cycloaddition reaction method in this example is as follows: 20 ml of propylene oxide containing 0.5 wt% catalyst (PS-TMG-PhNO2) was added to a 50 ml glass reactor. After purging three times with 99% carbon dioxide gas, the temperature was raised to 70°C with stirring. The reaction was carried out at this temperature with stirring for 4 hours, during which carbon dioxide gas was continuously introduced while maintaining the reactor pressure at 1.5 MPa. After the reaction was completed, the gas supply was stopped and the reactor was cooled to room temperature. Samples were taken for analysis. The results showed that the conversion rate of propylene oxide was 75.1%, and the selectivity of propylene carbonate was 99.9%.

[0054] Example 10: The carbon dioxide cycloaddition reaction method in this example is as follows: 20 ml of propylene oxide containing 0.5 wt% catalyst (PS-TMG-PhNO2) was added to a 50 ml glass reactor. After purging with 99% carbon dioxide gas three times, the temperature was raised to 80°C with stirring. The reaction was carried out at this temperature with stirring for 4 hours, during which carbon dioxide gas was continuously introduced while maintaining the reactor pressure at 1.5 MPa. After the reaction was completed, the gas supply was stopped and the reactor was cooled to room temperature. Samples were taken for analysis. The results showed that the conversion rate of propylene oxide was 85.6%, and the selectivity of propylene carbonate was 99.9%.

[0055] Example 11: The carbon dioxide cycloaddition reaction method in this example is as follows: 20 ml of propylene oxide containing 0.5 wt% catalyst (PS-TMG-PhNO2) was added to a 50 ml glass reactor. After three purgings with 99% carbon dioxide gas, the mixture was heated to 100°C with stirring. The reaction was carried out at this temperature with stirring for 4 hours, during which carbon dioxide gas was continuously introduced while maintaining the reactor pressure at 1.5 MPa. After the reaction was completed, the gas supply was stopped and the mixture was allowed to cool to room temperature. Samples were taken for analysis, and the results showed that the propylene oxide conversion rate was 99.9% and the propylene carbonate selectivity was 96.5%.

[0056] Example 12 The carbon dioxide cycloaddition reaction method in this example is as follows: 20 ml of propylene oxide containing 0.5 wt% catalyst (PS-TMG-PhNO2) was added to a 50 ml glass reactor. After purging with 99% carbon dioxide gas three times, the temperature was raised to 110°C with stirring. The reaction was carried out at this temperature with stirring for 4 hours, during which carbon dioxide gas was continuously introduced while maintaining the reactor pressure at 1.5 MPa. After the reaction was completed, the gas supply was stopped and the reactor was cooled to room temperature. Samples were taken for analysis. The results showed that the conversion rate of propylene oxide was 99.9%, and the selectivity of propylene carbonate was 94.6%.

[0057] Example 13 The difference between this example and Example 1 is the purity of the carbon dioxide gas. In this example, the purity of the carbon dioxide gas is 20%.

[0058] In this embodiment, the carbon dioxide cycloaddition reaction method achieves a propylene oxide conversion rate of 89.0% and a propylene carbonate selectivity of 99.6%.

[0059] Example 14 The difference between this example and Example 1 is the purity of the carbon dioxide gas. In this example, the purity of the carbon dioxide gas is 30%.

[0060] In this embodiment, the carbon dioxide cycloaddition reaction method achieves a propylene oxide conversion rate of 92.5% and a propylene carbonate selectivity of 99.4%.

[0061] Example 15 The difference between this example and Example 1 is the purity of the carbon dioxide gas. In this example, the purity of the carbon dioxide gas is 50%.

[0062] In this embodiment, the carbon dioxide cycloaddition reaction method achieves a propylene oxide conversion rate of 97.0% and a propylene carbonate selectivity of 99.5%.

[0063] Example 16 The difference between this example and Example 1 is the purity of the carbon dioxide gas. In this example, the purity of the carbon dioxide gas is 70%.

[0064] In this embodiment, the carbon dioxide cycloaddition reaction method achieves a propylene oxide conversion rate of 98.4% and a propylene carbonate selectivity of 99.8%.

[0065] Example 17 The difference between this example and Example 1 is the purity of the carbon dioxide gas. In this example, the purity of the carbon dioxide gas is 90%.

[0066] In this embodiment, the carbon dioxide cycloaddition reaction method achieves a propylene oxide conversion rate of 98.7% and a propylene carbonate selectivity of 99.5%.

[0067] Example 18 The difference between this example and Example 1 is the reaction pressure (i.e. the pressure inside the reactor). In this example, the reaction pressure is 0.1 MPa.

[0068] In this embodiment, the carbon dioxide cycloaddition reaction method achieves a propylene oxide conversion rate of 73.5% and a propylene carbonate selectivity of 96.3%.

[0069] Example 19 The difference between this example and Example 1 is the reaction pressure (i.e., the pressure inside the reactor). In this example, the reaction pressure is 0.5 MPa.

[0070] In this embodiment, the carbon dioxide cycloaddition reaction method achieves a propylene oxide conversion rate of 79.6% and a propylene carbonate selectivity of 97.1%.

[0071] Example 20 The difference between this example and Example 1 is the reaction pressure (i.e., the pressure inside the reactor). In this example, the reaction pressure is 2 MPa.

[0072] In this embodiment, the carbon dioxide cycloaddition reaction method achieves a propylene oxide conversion rate of 99.1% and a propylene carbonate selectivity of 99.6%.

[0073] Example 21 The difference between this example and Example 1 is the reaction pressure (i.e., the pressure inside the reactor). In this example, the reaction pressure is 3 MPa.

[0074] In this embodiment, the carbon dioxide cycloaddition reaction method achieves a propylene oxide conversion rate of 99.7% and a propylene carbonate selectivity of 99.8%.

[0075] Through the above Examples 1-21, it can be seen that the carbon dioxide cycloaddition reaction carried out using the catalyst of the present invention has good reaction selectivity and reaction conversion rate.

[0076] According to Examples 1-3, it can be seen that compared with sodium hydroxide choline cationic groups and quaternary ammonium cationic groups, the use of guanidine cationic groups can improve the reaction selectivity and reaction conversion rate. This may be because the guanidine cationic group contains more amine groups, which can improve the absorption capacity of CO2, thereby improving the reaction selectivity and reaction conversion rate.

[0077] Based on Examples 1 and 4-8, it can be seen that the carbon dioxide cycloaddition reaction exhibits better selectivity and conversion rate when R3, containing the phenoxy anion group, is a nitro group. This may be because using a nitro group as R3 can appropriately reduce the electron cloud density and nucleophilicity of the phenoxy anion, thereby making it easier for the carbonate species generated after CO2 activation to transfer, thus improving the reaction selectivity and conversion rate.

[0078] According to Examples 1 and 9-12, it can be seen that the carbon dioxide cycloaddition reaction method of the present invention can achieve good reaction selectivity and conversion rate in the range of 70-110°C. The reaction selectivity and conversion rate are optimal at a reaction temperature of 90°C. Specifically, at a reaction temperature of 70°C, the reaction conversion rate can reach 75.1%, and the reaction selectivity can reach 99.9%. Therefore, it can be seen that the carbon dioxide cycloaddition reaction method of the present invention can still achieve good reaction selectivity and conversion rate at lower reaction temperatures.

[0079] As can be seen from Examples 1 and 13-17, the carbon dioxide cycloaddition reaction method of the present invention can achieve good reaction selectivity and conversion rate when the purity of carbon dioxide gas is in the range of 20%-99%. Specifically, when the purity of carbon dioxide gas is 20%, the reaction conversion rate can reach 89.0%, and the reaction selectivity can reach 99.6%. This demonstrates that the carbon dioxide cycloaddition reaction method of the present invention can still achieve good reaction selectivity and conversion rate even at low carbon dioxide gas concentrations.

[0080] Based on Examples 1 and 18-21, it can be seen that the carbon dioxide cycloaddition reaction method of the present invention can achieve good reaction selectivity and reaction conversion rate within the range of 0.1 to 3 MPa. This demonstrates that the carbon dioxide cycloaddition reaction method of the present invention can still achieve good reaction selectivity and reaction conversion rate at low reaction pressures.

[0081] In summary, the catalyst of the present invention has good catalytic performance. Applying this catalyst to cycloaddition reactions can effectively reduce the cost of cycloaddition reactions and help reduce the requirements of cycloaddition reactions on reaction conditions (including CO2 gas purity, reaction pressure, etc.), thereby improving the reaction selectivity and reaction conversion rate of cycloaddition reactions.

[0082] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A catalyst for catalyzing the cycloaddition reaction of carbon dioxide, characterized in that, The structural formula of the catalyst is: Among them, poly core For polystyrene core, poly shell For the polychloromethylstyrene shell, Cation N + indicates a nitrogen-containing cationic group; Anion O - is a phenolic oxygen anionic group; The structural formula of the phenolic anionic group is as follows: R3 can be any one of hydrogen, hydroxyl, methoxy, amino, nitro, or chlorine.

2. The catalyst according to claim 1, characterized in that, The nitrogen-containing cationic group is any one of the following groups: sodium hydroxide choline cationic group, quaternary ammonium cationic group, or guanidine compound cationic group; preferably, the nitrogen-containing cationic group is a guanidine compound cationic group.

3. The catalyst according to claim 2, characterized in that, The nitrogen-containing cationic group is a sodium hydroxide choline cationic group.

4. The catalyst according to claim 2, characterized in that, The nitrogen-containing cationic group is a quaternary ammonium cationic group.

5. The catalyst according to claim 2, characterized in that, The nitrogen-containing cationic group is a guanidine compound cationic group, and the guanidine compound cationic group is a guanidine group.

6. The catalyst according to claim 5, characterized in that, The guanidine cationic group is 2-methyl-1,1,3,3-tetramethylguanidine.

7. The catalyst according to any one of claims 1-6, characterized in that, R3 is a nitro group, and the phenolic oxygen-containing anionic group is an o-nitrophenol anionic group.

8. The catalyst according to claim 1, characterized in that, The nitrogen-containing cationic group is 2-methyl-1,1,3,3-tetramethylguanidine, the phenolic oxygen-containing anionic group is o-nitrophenol anionic group, and the structural formula of the catalyst is:

9. A method for preparing a catalyst according to any one of claims 1-8, characterized in that, include: Polystyrene microspheres were dispersed in an organic solvent containing p-chloromethylstyrene monomer; An initiator and an emulsifier are added to an organic solvent to obtain a mixed solution; The mixed solution is heated to carry out a seed emulsion polymerization reaction to form core-shell microspheres; The core-shell microspheres were reacted with a nitrogen-containing cationic compound in anhydrous ethanol to graft nitrogen-containing cationic groups onto the core-shell microspheres; The phenol-oxygenated anionic compound and the core-shell microspheres are added to an organic solvent and the organic solvent is stirred to graft the phenol-oxygenated anionic groups onto the core-shell microspheres.

10. A method for a carbon dioxide cycloaddition reaction, characterized in that, Using the catalyst described in any one of claims 1-8, carbon dioxide gas and epoxide compounds are used as raw materials to carry out a cycloaddition reaction to generate cyclic carbonates; Preferably, the amount of catalyst used is 0.05-2 wt% of the amount of epoxy compound used; Preferably, the amount of catalyst used is 0.2-1 wt% of the amount of the epoxide compound; Preferably, the purity of the carbon dioxide gas is 20%-99%; Preferably, the purity of the carbon dioxide gas is 30%-99%.

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