Complex catalyst for synthesizing dimethyl carbonate, preparation method and application thereof

Abstract

The present application relates to the field of catalyst preparation, in particular to a complex catalyst for synthesizing dimethyl carbonate, a preparation method and application thereof; the complex catalyst is prepared by complex coordination reaction of copper salt and multiple types of nitrogen-containing and oxygen-containing organic ligands; the copper salt is selected from one or more of cuprous chloride, cuprous bromide, cuprous iodide, copper chloride, copper sulfate, copper nitrate and copper acetate; the ligand is selected from two or more of nicotinamide, 3,4-dihydro-2(1H) quinolinone, 1-hydroxyisoquinoline, 2-pyridine carboxamide, o-phenanthroline, hexamethylphosphorus triamide, N-methyl-1-pyridine-2-methylamine, N-isopropylphthalimide, 3-cyanoisoquinoline, N-methylpyrrolidone, N-methylphthalimide, 2-hydroxyquinoline, phthalimide, trans-N-(2-pyridylmethylene) aniline and respective derivatives thereof, and is prepared by compounding in different proportions; under the synergistic effect of multiple ligands, the selectivity of dimethyl carbonate is ensured to be higher than 98%, and the selectivity of CO is greatly improved.

Description

Technical Field

[0001] This invention relates to the field of catalyst preparation, specifically to complex catalysts for the synthesis of dimethyl carbonate, their preparation methods, and their applications. Background Technology

[0002] Dimethyl carbonate (DMC), with the structural formula CH3OCOOCH3, is non-toxic, biodegradable, and environmentally friendly. It is primarily used in the synthesis of polycarbonate (PC) and as a solvent in lithium-ion battery electrolytes. In PC synthesis, using DMC as a raw material and employing the non-phosgene process has become the mainstream method due to its green and environmentally friendly approach. With the rapid development of lithium-ion batteries, DMC, due to its excellent solubility, is widely used as a solvent in lithium-ion battery electrolytes. Furthermore, DMC is widely used as a green solvent in coatings, adhesives, and developers. Its high oxygen content makes it a gasoline additive for adjusting octane ratings, and it is used as a carbonylating agent in the synthesis of pesticide and pharmaceutical intermediates.

[0003] The main methods for synthesizing dimethyl carbonate (DMC) include the phosgene method, transesterification method, and methanol oxidative carbonylation method. The phosgene method has been phased out due to severe pollution. The methanol oxidative carbonylation method uses readily available and inexpensive methanol, CO, and O2 as raw materials to synthesize dimethyl carbonate under the action of a catalyst. Theoretically, methanol can be 100% converted to dimethyl carbonate, resulting in high atom utilization of the raw materials. Furthermore, besides the formation of dimethyl carbonate, only water is generated, making it environmentally friendly. The liquid-phase methanol oxidative carbonylation method avoids the use of toxic substances such as phosgene and NO. It uses readily available and inexpensive raw materials, has a simple process, a short flow rate, and is economical and environmentally friendly, making it the most promising production method for DMC currently.

[0004] Solid catalysts for the oxidative carbonylation synthesis of DMC from methanol are mainly palladium-based, including palladium chloride and palladium nitrate. Palladium compounds, as catalysts, also require co-catalysts, primarily copper compounds and amine compounds. The high price of precious metals leads to high production costs. Copper-based catalysts, due to their low cost and excellent catalytic activity, have become a research focus in this field. However, existing copper-based catalysts still suffer from problems such as low catalytic activity, easy deactivation during the reaction, high ligand costs, and strong corrosiveness to reaction equipment, limiting their industrial application.

[0005] To address the shortcomings of copper-based catalysts, researchers have conducted extensive modification studies, primarily by adding promoters or ligands such as o-phenanthroline and N-methylimidazolium to enhance the catalytic activity and reaction stability of copper compound catalysts and reduce equipment corrosion. Chinese patents have disclosed catalysts using cuprous chloride as the main catalyst, formed with nitrogen-containing heterocyclic compounds or polymeric complexes. These catalysts further improve the solubility of cuprous chloride in the reaction solution, increase catalyst activity and selectivity, and reduce the corrosiveness of the reaction system to equipment. However, the selectivity of CO for DMC is less than 50%, with more CO being converted into CO2, a greenhouse gas, which contradicts my country's carbon peaking and carbon neutrality goals. Furthermore, since CO selectivity is a core critical indicator, its quality directly affects process operating costs, product economic benefits, and the overall competitive advantage of the process. Summary of the Invention

[0006] The technical problem this application aims to solve is that the selectivity of CO for dimethyl carbonate (DMC) is less than 50%, and CO is mostly converted into CO2, a greenhouse gas. Based on the above technical problem, this invention develops a novel composite catalyst that can overcome the defects of existing catalysts such as poor selectivity for CO, easy deactivation, and strong corrosiveness to equipment. It has the advantages of high catalytic activity, high selectivity, good stability, and low corrosiveness to equipment. In particular, it can greatly improve the selectivity of CO for dimethyl carbonate and reduce the generation of CO2.

[0007] The specific technical solution of the present invention is as follows:

[0008] A complex catalyst is characterized by being prepared by a complex coordination reaction of a copper salt with various types of nitrogen-containing or nitrogen- and oxygen-containing organic ligands; the chemical formula and structural formula of the copper complex are shown below: (N)m-Cu-(O)n,

[0009]

[0010] L1 and L2 are two different ligands, and the coordination site can be two coordinating atoms of a ligand.

[0011] The copper salt is selected from one or more of cuprous chloride, cuprous bromide, cuprous iodide, cuprous chloride, copper sulfate, copper nitrate, and copper acetate.

[0012] The ligand is selected from two or more of nicotinamide, 3,4-dihydro-2(1H)quinoline, 1-hydroxyisoquinoline, 2-pyridinecarboxamide, o-phenanthroline, hexamethylphosphoric triamine, N-methyl-1-pyridin-2-methylamine, N-isopropylphthalimide, 3-cyanoisoquinoline, N-methylpyrrolidone, N-methylphthalimide, 2-hydroxyquinoline, phthalimide, trans-N-(2-pyridylmethylene)aniline and their respective derivatives.

[0013] Preferably, the ligand comprises two or more of amides, imides, quinolines, and quinoline-like organic compounds.

[0014] Preferably, the total molar ratio of the copper salt to the nitrogen-containing organic ligand is 1:1 to 4.

[0015] Preferably, the total molar ratio of the copper salt to the nitrogen-containing organic ligand is 1:1.2.

[0016] A method for preparing a complex catalyst, comprising the following steps:

[0017] Step 1: Add copper salt to an organic solvent and stir thoroughly to obtain a copper salt mixed solution;

[0018] Step 2: Add the selected organic ligands to the copper salt solution in the specified proportions and order, and stir the reaction at 25~100℃ for 2~5 hours;

[0019] Step 3: After the reaction is complete, the mixture is rotary evaporated and vacuum dried to obtain the organic complex catalyst.

[0020] Preferably, the organic solvent in step 1 is selected from one or more of methanol, ethanol, acetonitrile, and dichloromethane.

[0021] Application of a complexing catalyst, using the complexing catalyst described above to synthesize dimethyl carbonate.

[0022] Due to the adoption of the above technical solution, the beneficial effects of the present invention are as follows:

[0023] This invention utilizes (N) formed from a variety of organic ligands. m -Cu-(O) nThe composite complex catalyst is formed through the coordination interaction between copper salt and specific nitrogen- and oxygen-containing organic ligands. The mechanism involves the formation of a dicoordinate complex between the nitrogen-containing ligand and Cu ions in the catalyst preparation environment. This environment comprises metal ions, a bidentate nitrogen-containing ligand, and an amide, undergoing coordination in a solvent. This coordination strength is moderate, ensuring both the stability and high catalytic activity of Cu ions, while also improving catalyst stability and preventing the loss of active components during the reaction. Simultaneously, the amide ligand provides a certain alkaline environment. In this system, the Jahn-Te... The Cu²⁺ exhibits a significant hybridization effect, characterized by dsp² hybridization, consisting of one 3d orbital, one 4s orbital, and two 4p orbitals. This hybridization allows Cu²⁺ to form four coordinate bonds, resulting in a planar quadrilateral structure. Through the synergistic effect of multiple ligands, the selectivity of dimethyl carbonate is maintained above 98%, while the selectivity of CO is significantly improved to 70-84%, with a space-time yield greater than 10.5 g / (g·h). Furthermore, the catalyst exhibits no significant performance degradation after 10 cycles of use, thus solving the problems of low selectivity and easy deactivation of existing copper-based catalysts.

[0024] This catalyst exhibits low corrosivity to reaction equipment, eliminating the need for specialized corrosion protection and reducing equipment investment costs in industrial production. The low-priced ligands used further lower the catalyst's cost. Simultaneously, the catalyst preparation process is simple, the reaction conditions are mild, and it is easily scalable for large-scale production. The methanol oxidative carbonylation synthesis of dimethyl carbonate using this catalyst utilizes inexpensive and readily available raw materials with high atom utilization; the reaction process is simple, the reaction temperature and pressure are mild, and energy consumption is low, significantly reducing production costs and making it suitable for large-scale industrial production. Detailed Implementation

[0025] The present invention will now be described in detail with reference to specific embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention are still within the scope of protection of the present invention.

[0026] Example 1

[0027] (1) Catalyst preparation:

[0028] 9.9 g of cuprous chloride was weighed and added to 80 ml of methanol. The mixture was stirred at room temperature for 15 minutes. Then, 20.0 g of o-phenanthroline was weighed and added to the copper salt solution. The reaction system was heated to 90 °C and stirred at a rate of 400 r / min for 4 hours. After the reaction was completed, the methanol was removed by rotary evaporation at 55 °C and a vacuum of 0.07 MPa to obtain a solid product. The solid product was placed in a vacuum drying oven and dried at 70 °C for 4 hours to obtain an organic complex catalyst.

[0029] (2) Catalyst application:

[0030] Add 10g methanol and 0.3g catalyst to a 100ml high-pressure reactor; replace the air in the reactor with CO gas three times, then purge with CO until the pressure reaches 3.6MPa, and then purge with O2 until the total pressure reaches 4.0MPa (the pressure ratio of CO to O2 is 9:1); heat the reactor to 120℃, stir at 400r / min, and react at constant temperature and pressure for 0.5 hours; after the reaction is completed, cool to room temperature in a water bath, collect the gas components for analysis, filter the liquid to separate the catalyst, and purify the filtrate by distillation to obtain dimethyl carbonate product.

[0031] (3) Results Analysis:

[0032] The test results showed that the methanol conversion rate was 35.7%, the dimethyl carbonate selectivity was 98.1%, the space-time yield was 15.8 g / (gcat·h), and the CO selectivity was 48%.

[0033] Example 2:

[0034] (1) Catalyst preparation:

[0035] 9.9 g of cuprous chloride was weighed and added to 80 ml of methanol. The mixture was stirred at room temperature for 15 minutes. Then, 10.0 g of o-phenanthroline and 10.2 g of 2-hydroxyquinoline were weighed and added to the copper salt solution. The reaction system was heated to 90 °C and stirred at a rate of 400 r / min for 4 hours. After the reaction was completed, the methanol was removed by rotary evaporation at 55 °C and a vacuum of 0.07 MPa to obtain a solid product. The solid product was placed in a vacuum drying oven and dried at 70 °C for 4 hours to obtain an organic composite catalyst.

[0036] (2) Catalyst application:

[0037] Add 10g methanol and 0.3g catalyst to a 100ml high-pressure reactor; replace the air in the reactor with CO gas three times, then purge with CO until the pressure reaches 3.6MPa, and then purge with O2 until the total pressure reaches 4.0MPa (the pressure ratio of CO to O2 is 9:1); heat the reactor to 120℃, stir at 400r / min, and react at constant temperature and pressure for 0.5 hours; after the reaction is completed, cool to room temperature in a water bath, collect the gas components for analysis, filter the liquid to separate the catalyst, and purify the filtrate by distillation to obtain dimethyl carbonate product.

[0038] (3) Results Analysis:

[0039] The test results showed that the methanol conversion rate was 30.4%, the dimethyl carbonate selectivity was 98.0%, the space-time yield was 12.7 g / (gcat·h), and the CO selectivity was 78%.

[0040] Example 3:

[0041] (1) Catalyst preparation:

[0042] 18.8 g of copper nitrate was weighed and added to 80 ml of ethanol, and stirred at room temperature for 15 minutes to obtain a copper salt solution. 14.0 g of o-phenanthroline and 8.3 g of N-methylphthalimide were weighed and added to the copper salt solution. The reaction system was heated to 70 °C, and the stirring rate was 400 r / min. The reaction was carried out at a constant temperature for 4 hours. After the reaction was completed, the ethanol was removed by rotary evaporation at 55 °C and a vacuum of 0.07 MPa to obtain a solid product. The solid product was placed in a vacuum drying oven and dried at 75 °C for 5 hours to obtain an organic composite catalyst.

[0043] (2) Catalyst application:

[0044] Add 10g of methanol and 0.3g of catalyst to a 100ml high-pressure reactor; replace the air in the reactor with CO gas three times, then purge with CO until the pressure reaches 3.5MPa, and then purge with O2 until the total pressure reaches 4.0MPa (the pressure ratio of CO to O2 is 7:1).

[0045] The reactor was heated to 120°C, stirred at 400 r / min, and reacted under constant temperature and pressure for 0.5 hours. After the reaction was completed, the reactor was cooled to room temperature in a water bath. The gaseous components were collected for analysis, the catalyst was separated by liquid filtration, and the filtrate was purified by distillation to obtain dimethyl carbonate product.

[0046] (3) Results Analysis:

[0047] The test results showed that the methanol conversion rate was 30.1%, the dimethyl carbonate selectivity was 98.4%, the space-time yield was 13.0 g / (gcat·h), and the CO selectivity was 81%.

[0048] Example 4:

[0049] (1) Catalyst preparation

[0050] 9.9 g of cuprous chloride (CuCl) was weighed and added to 100 ml of acetonitrile. The mixture was stirred at 50 °C for 25 minutes to obtain a copper salt mixed solution. 10.0 g of o-phenanthroline and 13.3 g of trans-N-(2-pyridylmethylene)aniline were weighed and added to the copper salt solution. The reaction system was heated to 80 °C and stirred at a rate of 500 r / min for 4 hours. After the reaction was completed, the acetonitrile was removed by rotary evaporation at 50 °C and a vacuum of 0.09 MPa to obtain a solid product. The solid product was placed in a vacuum drying oven and dried at 75 °C for 8 hours to obtain an organic composite catalyst.

[0051] (2) Catalyst application

[0052] Add 10g of methanol and 0.32g of catalyst to a 100ml high-pressure reactor; replace the air in the reactor with CO gas three times, then purge with CO until the pressure reaches 3.6MPa, and then purge with O2 until the total pressure reaches 4.0MPa (the pressure ratio of CO to O2 is 9:1); heat the reactor to 100℃, stir at 300r / min, and react at constant temperature and pressure for 0.5 hours; after the reaction is completed, cool to room temperature in a water bath, collect the gas components for analysis, filter the liquid to separate the catalyst, and purify the filtrate by distillation to obtain dimethyl carbonate product.

[0053] (3) Results Analysis:

[0054] The test results showed that the methanol conversion rate was 34.2%, the dimethyl carbonate selectivity was 97.8%, the space-time yield was 15.7 g / (gcat·h), and the CO selectivity was 80%.

[0055] Example 5:

[0056] (1) Catalyst preparation:

[0057] 9.9 g of cuprous chloride was weighed and added to 80 ml of methanol. The mixture was stirred at room temperature for 15 minutes. Then, 10.0 g of o-phenanthroline and 10.4 g of phthalimide were weighed and added to the copper salt solution. The reaction system was heated to 90 °C and stirred at a rate of 400 r / min for 4 hours. After the reaction was completed, the methanol was removed by rotary evaporation at 55 °C and a vacuum of 0.07 MPa to obtain a solid product. The solid product was placed in a vacuum drying oven and dried at 70 °C for 4 hours to obtain an organic composite catalyst.

[0058] (2) Catalyst application:

[0059] Add 10g methanol and 0.3g catalyst to a 100ml high-pressure reactor; replace the air in the reactor with CO gas three times, then purge with CO until the pressure reaches 3.6MPa, and then purge with O2 until the total pressure reaches 4.0MPa (the pressure ratio of CO to O2 is 9:1); heat the reactor to 120℃, stir at 400r / min, and react at constant temperature and pressure for 0.5 hours; after the reaction is completed, cool to room temperature in a water bath, collect the gas components for analysis, filter the liquid to separate the catalyst, and purify the filtrate by distillation to obtain dimethyl carbonate product.

[0060] (3) Results Analysis:

[0061] The test results showed that the methanol conversion rate was 33.2%, the dimethyl carbonate selectivity was 98.3%, the space-time yield was 13.4 g / (gcat·h), and the CO selectivity was 82%.

[0062] Example 6:

[0063] (1) Catalyst preparation:

[0064] 16.0 g of copper sulfate was weighed and added to 80 ml of methanol. The mixture was stirred at room temperature for 15 minutes. Then, 14.0 g of o-phenanthroline and 9.3 g of hexamethylphosphoric triamine were weighed and added to the copper salt solution. The reaction system was heated to 90 °C and stirred at a rate of 400 r / min for 4 hours. After the reaction was completed, the methanol was removed by rotary evaporation at 55 °C and a vacuum of 0.07 MPa to obtain a solid product. The solid product was placed in a vacuum drying oven and dried at 70 °C for 4 hours to obtain an organic composite catalyst.

[0065] (2) Catalyst application:

[0066] Add 10g methanol and 0.3g catalyst to a 100ml high-pressure reactor; replace the air in the reactor with CO gas three times, then purge with CO until the pressure reaches 3.6MPa, and then purge with O2 until the total pressure reaches 4.0MPa (the pressure ratio of CO to O2 is 9:1); heat the reactor to 110℃, stir at 400r / min, and react at constant temperature and pressure for 0.5 hours; after the reaction is completed, cool to room temperature in a water bath, collect the gas components for analysis, filter the liquid to separate the catalyst, and purify the filtrate by distillation to obtain dimethyl carbonate product.

[0067] (3) Results Analysis:

[0068] The test results showed that the methanol conversion rate was 30.5%, the dimethyl carbonate selectivity was 97.8%, the space-time yield was 10.1 g / (gcat·h), and the CO selectivity was 70%.

[0069] Example 7:

[0070] (1) Catalyst preparation:

[0071] 9.9 g of cuprous chloride was weighed and added to 80 ml of methanol. The mixture was stirred at room temperature for 15 minutes. Then, 11.4 g of o-phenanthroline and 7.2 g of 2-pyridinecarboxamide were weighed and added to the copper salt solution. The reaction system was heated to 90 °C and stirred at a rate of 400 r / min for 4 hours. After the reaction was completed, the methanol was removed by rotary evaporation at 55 °C and a vacuum of 0.07 MPa to obtain a solid product. The solid product was placed in a vacuum drying oven and dried at 70 °C for 4 hours to obtain an organic composite catalyst.

[0072] (2) Catalyst application:

[0073] Add 10g methanol and 0.3g catalyst to a 100ml high-pressure reactor; replace the air in the reactor with CO gas three times, then purge with CO until the pressure reaches 3.6MPa, and then purge with O2 until the total pressure reaches 4.0MPa (the pressure ratio of CO to O2 is 9:1); heat the reactor to 120℃, stir at 400r / min, and react at constant temperature and pressure for 0.5 hours; after the reaction is completed, cool to room temperature in a water bath, collect the gas components for analysis, filter the liquid to separate the catalyst, and purify the filtrate by distillation to obtain dimethyl carbonate product.

[0074] (3) Results Analysis:

[0075] The test results showed that the methanol conversion rate was 33.0%, the dimethyl carbonate selectivity was 98.0%, the space-time yield was 14.7 g / (gcat·h), and the CO selectivity was 84%.

[0076] The following table summarizes the addition ratios and effects of each material in Examples 1-7;

[0077] Table 1: Comparison of the addition ratio and effects of each material in Examples 1-7

[0078]

[0079] In Examples 3, 4, 5, and 7 of this invention, the added composite ligand, o-phenanthroline, is a bidentate nitrogen-containing heterocyclic ligand. Its two pyridine nitrogen atoms can form a stable coordination structure with copper ions. This coordination forms a planar four-coordinate geometry, which allows copper ions to maintain their activity and is not easily deactivated during the reaction. The second ligand in the composite system, N-methylphthalimide, trans-N-(2-pyridylmethylene)aniline, phthalimide, and 2-pyridinecarboxamide, all have at least one nitrogen atom that can form a coordination interaction with copper ions. Some molecules also contain oxygen atoms. The fourth coordination site interacts with oxygen atoms or solvent molecules. On the one hand, they provide auxiliary electron supply and regulation for copper ions by coordinating with o-phenanthroline, ensuring that copper ions are in an electronic state that is both stable and has high catalytic activity. On the other hand, these ligands can provide certain steric hindrance in the coordination environment, limiting the possibility of side reactions, thereby enhancing the selectivity of the reaction.

[0080] The complex copper coordination center formed by o-phenanthroline and the second ligand can coordinate the adsorption and activation of oxygen and carbon monoxide at the reaction site, enabling carbon monoxide to participate more in the formation of dimethyl carbonate rather than being converted into carbon dioxide. The amide or quinoline ligands provide a weak alkaline environment in the system, which can further optimize the electronic structure of copper ions and enhance their affinity for carbon monoxide. This synergistic effect enables the catalyst to significantly improve the utilization rate of carbon monoxide while maintaining high dimethyl carbonate selectivity, and ensures the space-time yield and cycle stability of the reaction.

[0081] Compared with Examples 1, 2 and 6, Example 1 uses only a single ligand, o-phenanthroline, whose copper ion active center lacks electronic regulation and steric protection. Therefore, although the selectivity of dimethyl carbonate is high, the utilization rate of carbon monoxide is low.

[0082] Although another ligand was added in Example 2 to further optimize the electronic structure of copper ions, the ligand's electronic effect was strong, leading to a decrease in methanol conversion and space-time yield.

[0083] Although the ligand in Example 6 further optimized the electronic structure of copper ions, it had significant steric hindrance and lacked a stable cyclic structure, resulting in insufficient electron supply capacity, which also limited catalytic activity and space-time yield.

[0084] In contrast, Examples 3, 4, 5 and 7, by forming a stable and active complex copper coordination center with a suitable second ligand via o-phenanthroline, not only ensured the recyclability of the catalyst but also achieved high selectivity and high carbon monoxide utilization, thus outperforming other control examples in overall performance.

[0085] To further investigate the effect of 2-pyridinecarboxamide addition on catalyst performance in Example 7, this study prepared a series of 2-pyridinecarboxamide catalyst samples with different addition ratios, and systematically evaluated their catalytic activity and selectivity. The results are shown in Table 2.

[0086] Table 2: Effect of ligand 2-pyridinecarboxamide addition amount on catalyst performance

[0087]

[0088] Note: The amount of 2-pyridinecarboxamide added refers to its total molar amount in the total ligand system, and the total molar amount is relative to the copper salt.

[0089] As shown in the table above, with the increase of 2-pyridinecarboxamide dosage, the methanol conversion rate and space-time yield both decreased significantly, while the CO selectivity increased significantly; the addition of amide can effectively improve the CO selectivity of the catalyst.

[0090] Catalyst recycling performance test

[0091] The catalyst prepared by the method in Example 7 was subjected to 10 repeated methanol oxidative carbonylation reactions to synthesize DMC under the application conditions of Example 7. After each reaction, the catalyst was separated and recovered, and its catalytic performance was tested. The results are shown in the table below:

[0092] Table 3. Performance Comparison of Catalysts After 10 Cycles

[0093]

[0094] Note: The reaction numbered 10 was significantly affected by heating time and rate. The data did increase slightly, but only slightly, and there was analytical error, which is within the normal error range. This indicates that the reaction is stable and exhibits fluctuation characteristics within a certain range.

[0095] As shown in the table above, after the catalyst of Example 7 was recycled 10 times, the methanol conversion rate remained above 34%, the DMC selectivity remained above 98.0%, the space-time yield did not decrease significantly, and the CO selectivity was 81%, indicating that the catalyst has excellent cycle stability and CO selectivity.

[0096] It should be noted that the embodiments described above are only partial experimental data and are used solely to explain the present invention, and do not constitute any limitation on the present invention. All publications, patent applications, patents, and other references mentioned in this specification are incorporated herein by reference. Unless otherwise defined, all technical and scientific terms used in this specification have the meanings conventionally understood by those skilled in the art. In case of conflict, the definitions in this specification shall prevail.

Claims

1. A complex catalyst characterized in that, The copper complex is prepared by a complex coordination reaction of copper salts with various types of nitrogen-containing or nitrogen- and oxygen-containing organic ligands; the chemical formula and structural formula of the copper complex are shown below: (N)m-Cu-(O)n, ； L1 and L2 are two different ligands, and the coordination site can be two coordinating atoms of a ligand. The copper salt is selected from one or more of cuprous chloride, cuprous bromide, cuprous iodide, cuprous chloride, copper sulfate, copper nitrate, and copper acetate. The ligand is selected from two or more of nicotinamide, 3,4-dihydro-2(1H)quinoline, 1-hydroxyisoquinoline, 2-pyridinecarboxamide, o-phenanthroline, hexamethylphosphoric triamine, N-methyl-1-pyridin-2-methylamine, N-isopropylphthalimide, 3-cyanoisoquinoline, N-methylpyrrolidone, N-methylphthalimide, 2-hydroxyquinoline, phthalimide, trans-N-(2-pyridylmethylene)aniline and their respective derivatives.

2. The complexing catalyst according to claim 1, characterized in that, The ligands include two or more of amides, imides, quinolines, and quinoline-like organic compounds.

3. The complex catalyst according to claim 1, characterized in that, The total molar ratio of the copper salt to the nitrogen-containing organic ligand is 1:1 to 4.

4. The complex catalyst according to claim 1, characterized in that, The total molar ratio of the copper salt to the nitrogen-containing organic ligand is 1:1.

2.

5. A method for preparing a complex catalyst, characterized in that, The following steps are used to prepare the complex catalyst according to any one of claims 1 to 4: Step 1: Add copper salt to an organic solvent and stir thoroughly to obtain a copper salt mixed solution; Step 2: Add the selected organic ligands to the copper salt solution in the specified proportions and order, and stir the reaction at 25~100℃ for 2~5 hours; Step 3: After the reaction is complete, the mixture is rotary evaporated and vacuum dried to obtain the organic complex catalyst.

6. The method for preparing a complex catalyst according to claim 5, characterized in that, The organic solvent in step 1 is selected from one or more of methanol, ethanol, acetonitrile, and dichloromethane.

7. The application of a complexing catalyst, characterized in that, Dimethyl carbonate is synthesized using a complexing catalyst according to any one of claims 1 to 4.

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