A nano-catalyst for synthesizing dimethyl carbonate, a preparation method and application thereof

Abstract

This invention discloses a nanocatalyst for the synthesis of dimethyl carbonate, its preparation method, and its application, belonging to the field of catalyst technology. The invention involves a Friedel-Crafts reaction of biphenyl dichlorobenzyl with an alkylating agent to obtain a highly cross-linked nanoparticle support; a nucleophilic substitution reaction of this support with imidazole chloride to obtain an imidazole-modified highly cross-linked nanoparticle support; and an ion exchange reaction in an alkaline solution to obtain a highly cross-linked nanoparticle catalyst. The preparation method of this invention uses mild reaction conditions, requiring no high pressure or high temperature, making it suitable for industrial production. The obtained nanocatalyst does not contain toxic components; it can catalyze the synthesis of dimethyl carbonate under mild conditions, achieving a dimethyl carbonate yield of 96% and a selectivity of 99%; it exhibits excellent cycling performance, achieving a yield of 93% and a selectivity of 99% after 10 cycles, thus solving the problems of existing catalysts containing toxic components, poor catalyst cycling performance, and the need for high temperature and high pressure reactions.

Description

Technical Field

[0001] This invention belongs to the field of catalyst technology, specifically relating to a nanocatalyst for the synthesis of dimethyl carbonate, its preparation method, and its application. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] Lithium-ion batteries, as a type of green electrochemical storage device, possess advantages such as high energy density, high operating voltage, rapid charge and discharge, wide electrochemical window, and environmental friendliness, and are widely used in consumer electronics, transportation power, and new energy storage. Electrolyte, as one of the four main materials of lithium-ion batteries, is the carrier for lithium-ion transport within the battery and is often referred to as the 'blood' of lithium-ion batteries. Electrolytes are composed of lithium salts, solvents, and additives, and these three components jointly determine the performance of the electrolyte. For different application areas, material systems, and battery structures, researchers have designed electrolytes with different formulations of lithium salts, solvents, and additives to achieve the goals of high conductivity, wide temperature range, strong stability, and safety.

[0004] Carbonates (such as ethylene carbonate, dimethyl carbonate, diethyl carbonate, and propylene carbonate) are often used as solvents in electrolytes to provide transport media for lithium ions due to their low toxicity, high dielectric constant, and low viscosity. Currently, the traditional process for synthesizing carbonates (such as dimethyl carbonate) is the phosgene process; however, this process uses large amounts of highly toxic and corrosive phosgene and is gradually being phased out. To meet the vision of green chemistry and the requirements of atom economy, researchers have developed a new process for the direct synthesis of dimethyl carbonate from methanol and carbon dioxide. This process has the advantages of a short process flow, high atom utilization, and green sustainability. However, due to the inertness and thermodynamic limitations of carbon dioxide, the product yield of this process is low, making it difficult to meet the needs of large-scale production. Researchers have therefore developed various catalytic systems (such as quaternary ammonium halides, alkali metals, Schiff bases, and ionic liquids) to improve the yield of this process.

[0005] However, existing catalytic technologies often suffer from drawbacks such as poor catalyst recovery and recycling performance, high energy consumption due to high temperature and pressure, and the presence of many toxic and harmful components. For example, patent CN02154482.4 discloses a catalytic system of copper halide compounds CuX2 (X=Cl, Br, I) for gas-phase synthesis. This catalytic system has high catalytic selectivity, but the catalyst recovery and recycling performance is poor, and the catalyst contains harmful halogen components. For example, patent CN107915574A discloses a heterogeneous composite metal oxide MO. The TO2 / SP catalytic system exhibits good catalyst recyclability and minimal catalyst loss, with no significant decrease in conversion and selectivity after five cycles. However, this system requires high-temperature (120°C) synthesis, resulting in high energy consumption. Patent CN114210342A discloses a novel catalyst prepared from soluble palladium salts, manganese dioxide, and activated carbon. This system maintains a stable conversion rate of 30% and a selectivity exceeding 95%. However, its preparation process is complex, and catalytic conditions require 0.3-0.7 MPa and 120°C. Therefore, it is essential to develop a novel catalyst with high catalytic activity, strong recovery performance, absence of toxic elements such as halogens, and the ability to catalyze the synthesis of carbonate-based lithium-ion electrolytes under mild conditions (room pressure, lower temperature). Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a nanocatalyst for the synthesis of dimethyl carbonate, its preparation method, and its application. The nanocatalyst provided by the present invention has the advantages of good cycle performance, environmental friendliness, and high catalytic activity, and can be used to synthesize lithium battery electrolyte - dimethyl carbonate.

[0007] To achieve the above objectives, the technical solution of the present invention is as follows:

[0008] In a first aspect, the present invention provides a method for preparing a nanocatalyst for the synthesis of dimethyl carbonate, comprising the following steps:

[0009] Biphenyl dichlorobenzyl was dissolved in an alkylating agent and subjected to a Friedel-Crafts reaction (Friedel-Crafts reaction, or simply Friedel reaction) under catalytic conditions. After the reaction was completed, a highly cross-linked nanoparticle carrier was obtained.

[0010] The highly cross-linked nanoparticle carrier and imidazole chloride were dissolved in a solvent and subjected to a nucleophilic substitution reaction under heating and stirring conditions. After the reaction was completed, an imidazole-modified highly cross-linked nanoparticle carrier was obtained.

[0011] The imidazole-modified ultra-high crosslinked nanoparticle support was dissolved in an alkaline solution and subjected to an ion exchange reaction under heating conditions. After the reaction was completed, an ultra-high crosslinked nanoparticle catalyst was obtained.

[0012] In some embodiments of the present invention, the alkylating agent includes, but is not limited to, one of haloalkanes, alkyllithium, alkylcopper reagents, alkylaluminum reagents, alkylmagnesium reagents, or alcohols.

[0013] In some embodiments of the present invention, the catalyst includes, but is not limited to, one of anhydrous aluminum trichloride, ferric chloride, or boron trifluoride.

[0014] In some embodiments of the present invention, under a protective atmosphere, biphenyl dichlorobenzyl is dissolved in an alkylating agent, stirred and preheated, a catalyst is added, and the mixture is heated to carry out a Friedel-Crafts reaction.

[0015] In some embodiments of the present invention, the ratio of biphenyl dichlorobenzyl to the alkylating agent is 1:10~15, g / mL.

[0016] In some embodiments of the present invention, the mass ratio of biphenyl dichlorobenzyl to the catalyst is 3 to 5:1.

[0017] In some embodiments of the present invention, the preheating temperature is 40~60°C and the preheating time is 20~40 min.

[0018] In some embodiments of the present invention, the Friedel-Crafts reaction is carried out at a temperature of 70-90°C for a reaction time of 8-12 hours.

[0019] In some embodiments of the present invention, the imidazole chloride salt is selected from any one of 1-decyl-3-methylimidazolium chloride, 1-octyl-3-methylimidazolium chloride, and 1-hexyl-3-methylimidazolium chloride.

[0020] In some embodiments of the present invention, the molar ratio of the imidazole chloride to the ultra-highly cross-linked nanoparticle carrier is 1.1 to 1.3:1.

[0021] In some embodiments of the present invention, the ratio of the ultra-high cross-linked nanoparticle carrier to the solvent is 1:10~15, g / mL.

[0022] In some embodiments of the present invention, the nucleophilic substitution reaction is carried out at a temperature of 70-90°C for a time of 8-12 h.

[0023] In some embodiments of the present invention, the alkaline solution is a sodium hydroxide solution or a potassium hydroxide solution, and the concentration of the alkaline solution is 0.8~1.2 mol / L.

[0024] In some embodiments of the present invention, the ion exchange reaction is carried out at a temperature of 30-50°C for a time of 4-6 h.

[0025] In a second aspect, the present invention provides a nanocatalyst for the synthesis of dimethyl carbonate, which is prepared by the above-described preparation method.

[0026] A third aspect of the present invention provides an application of the above-described nanocatalyst in the synthesis of dimethyl carbonate.

[0027] In some embodiments of the present invention, the synthesis of dimethyl carbonate is carried out by: mixing propylene oxide, methanol and the nanocatalyst in a carbon dioxide atmosphere, heating and stirring to react, and synthesizing dimethyl carbonate in a one-pot process.

[0028] A third aspect of the present invention provides a method for one-pot synthesis of dimethyl carbonate, comprising the following steps:

[0029] In a carbon dioxide atmosphere, propylene oxide, methanol, and the aforementioned nanocatalyst are mixed and heated with stirring to synthesize dimethyl carbonate in a one-pot process.

[0030] In some embodiments of the present invention, the ratio of propylene oxide, methanol and nanocatalyst is 1:1:5~8, mol / mol / g.

[0031] In some embodiments of the present invention, the heating and stirring reaction is carried out at a temperature of 50-70°C for 8-12 hours.

[0032] The beneficial effects of this invention are as follows:

[0033] This invention proposes a method for preparing a nanocatalyst for the synthesis of dimethyl carbonate, comprising the following steps: dissolving biphenyl dichlorobenzyl in an alkylating agent and carrying out a Friedel-Crafts reaction under catalytic conditions; after the reaction is completed, a highly cross-linked nanoparticle support is obtained; dissolving the highly cross-linked nanoparticle support and imidazole chloride in a solvent and carrying out a nucleophilic substitution reaction under heating and stirring conditions; after the reaction is completed, an imidazole-modified highly cross-linked nanoparticle support is obtained; dissolving the imidazole-modified highly cross-linked nanoparticle support in an alkaline solution and carrying out an ion exchange reaction under heating conditions; after the reaction is completed, a highly cross-linked nanoparticle catalyst is obtained. The method for preparing the nanocatalyst for the synthesis of dimethyl carbonate proposed in this invention has mild reaction conditions, does not require high pressure or high temperature, and is suitable for industrial production.

[0034] The nanocatalyst provided by this invention for the synthesis of dimethyl carbonate is a novel ultra-high cross-linked catalyst that solves the problems of toxic components, poor catalyst cycle performance, and the need for high temperature and high pressure in previous catalysts. It can efficiently catalyze the one-pot synthesis of dimethyl carbonate from propylene oxide, carbon dioxide, and methanol under mild conditions, and has the following advantages in the catalytic process:

[0035] 1. The catalytic reaction can achieve a dimethyl carbonate yield of 96% and a selectivity of 99% at 60℃ and atmospheric pressure for 8 hours;

[0036] 2. The catalyst has a high imidazole loading of 6%-7%, is halogen-free, and contains no toxic or harmful components;

[0037] 3. The catalyst exhibits excellent recovery performance, achieving a dimethyl carbonate yield of 93% and a selectivity of 99% after 10 cycles;

[0038] 4. The catalyst has a specific surface area of ​​800 m². 2 It contains more than / g and has abundant pores, which can enrich carbon dioxide, improve catalytic efficiency, and is a green catalytic process;

[0039] 5. The catalyst can catalyze the ring-opening addition of propylene oxide and carbon dioxide to synthesize propylene carbonate, and can further catalyze the synthesis of dimethyl carbonate from propylene carbonate and methanol. This one-pot synthesis of dimethyl carbonate reduces the number of process steps and lowers costs and energy consumption. Attached Figure Description

[0040] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0041] Figure 1 This is a SEM image of the catalyst in Example 2 of the present invention;

[0042] Figure 2 The image shows a TEM image of the catalyst in Example 1 of the present invention.

[0043] Figure 3 The image shown is the XPS full spectrum of the catalyst in Example 1 of this invention.

[0044] Figure 4 This is a high-resolution XPS N1s spectrum image of the catalyst in Example 1 of the present invention;

[0045] Figure 5 The synthesis route of the catalyst in Example 1 of this invention is shown below. Detailed Implementation

[0046] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0047] In view of the shortcomings of existing catalysts for the catalytic synthesis of dimethyl carbonate, such as poor recycling performance, high energy consumption due to high temperature and pressure during preparation, and the presence of toxic and harmful components, this invention proposes a method for preparing a catalyst with good recycling performance, environmental friendliness, and high efficiency, and applies it to the synthesis of dimethyl carbonate for lithium battery electrolytes.

[0048] A typical embodiment of the present invention provides a method for preparing a nanocatalyst for the synthesis of dimethyl carbonate, comprising the following steps:

[0049] Biphenyl dichlorobenzyl was dissolved in an alkylating agent and subjected to a Friedel-Crafts reaction under catalytic conditions. After the reaction was completed, a highly cross-linked nanoparticle carrier was obtained.

[0050] The highly cross-linked nanoparticle carrier and imidazole chloride were dissolved in a solvent and subjected to a nucleophilic substitution reaction under heating and stirring conditions. After the reaction was completed, an imidazole-modified highly cross-linked nanoparticle carrier was obtained.

[0051] The imidazole-modified ultra-high crosslinked nanoparticle support was dissolved in an alkaline solution and subjected to an ion exchange reaction under heating conditions. After the reaction was completed, an ultra-high crosslinked nanoparticle catalyst was obtained.

[0052] In some embodiments of this implementation, the alkylating agent includes, but is not limited to, one of haloalkanes, alkyllithium, alkylcopper reagents, alkylaluminum reagents, alkylmagnesium reagents, or alcohols.

[0053] The haloalkanes include, but are not limited to, chloromethane, bromomethane, etc., and the chloromethanes include, but are not limited to, monochloromethane, dichloromethane, etc.

[0054] The alkyl lithium includes, but is not limited to, methyl lithium, tert-butyl lithium, etc.

[0055] The alkyl copper includes, but is not limited to, methyl copper, ethyl copper, etc.

[0056] The alkylaluminum includes, but is not limited to, trimethylaluminum, triethylaluminum, etc.

[0057] The alkyl magnesium includes, but is not limited to, methyl magnesium, tert-butyl magnesium, etc.

[0058] In some embodiments of this implementation, the alkylating agent is dichloromethane.

[0059] In some embodiments of the present invention, the catalyst includes, but is not limited to, one of anhydrous aluminum trichloride, ferric chloride, or boron trifluoride. In some embodiments, the catalyst is ferric chloride.

[0060] In some embodiments of the present invention, under a protective atmosphere, biphenyl dichlorobenzyl is dissolved in an alkylating agent, stirred and preheated, a catalyst is added, and the mixture is heated to carry out a Friedel-Crafts reaction.

[0061] In some embodiments of the present invention, the protective atmosphere is an inert gas and / or nitrogen. In some embodiments, the protective atmosphere is nitrogen.

[0062] In some embodiments of the present invention, the ratio of biphenyl dichlorobenzyl to the alkylating agent is 1:10 to 15, g / mL, specifically 1:10, 1:11, 1:12, 1:13, 1:14, or 1:15, etc. In some embodiments of the present invention, the mass ratio of biphenyl dichlorobenzyl to the catalyst is 3 to 5:1, specifically 3:1, 4:1, or 5:1, etc.

[0063] In some embodiments of the present invention, the preheating temperature is 40~60℃, specifically 40℃, 43℃, 45℃, 47℃, 50℃, 55℃ or 60℃, etc.; the preheating time is 20~40 min, specifically 20 min, 23 min, 25 min, 28 min, 30 min, 32 min, 34 min, 36 min, 38 min or 40 min, etc.

[0064] In some embodiments of the present invention, the Friedel-Crafts reaction is carried out at a temperature of 70-90°C, specifically 70°C, 73°C, 75°C, 77°C, 80°C, 85°C, or 90°C; and the reaction time is carried out at a time of 8-12 hours, specifically 8 hours, 8.5 hours, 9 hours, 9.5 hours, 10 hours, 10.5 hours, 11 hours, 11.5 hours, or 12 hours.

[0065] In some embodiments of the present invention, after the Friedel-Crafts reaction is completed, the resulting solid-liquid mixture is subjected to solid-liquid separation, washing, and drying to obtain an ultra-highly cross-linked nanoparticle carrier.

[0066] In some embodiments of the present invention, the imidazole chloride salt is selected from any one of 1-decyl-3-methylimidazolium chloride, 1-octyl-3-methylimidazolium chloride, and 1-hexyl-3-methylimidazolium chloride.

[0067] In some embodiments of the present invention, the molar ratio of the imidazole chloride to the ultra-high cross-linked nanoparticle carrier is 1.1 to 1.3:1, specifically 1.1:1, 1.2:1, or 1.3:1, etc.

[0068] In some embodiments of the present invention, the ratio of the ultra-high cross-linked nanoparticle carrier to the solvent is 1:10~15, g / mL, specifically 1:10, 1:11, 1:12, 1:13, 1:14 or 1:15, etc.

[0069] In some embodiments of the present invention, the nucleophilic substitution reaction is carried out at a temperature of 70-90°C, specifically 70°C, 73°C, 75°C, 77°C, 80°C, 85°C, or 90°C; and for a reaction time of 8-12 h, specifically 8 h, 8.5 h, 9 h, 9.5 h, 10 h, 10.5 h, 11 h, 11.5 h, or 12 h.

[0070] In some embodiments of the present invention, after the nucleophilic reaction is completed, the resulting solid-liquid mixture is subjected to solid-liquid separation, washing, and drying to obtain an imidazole-modified ultra-high cross-linked nanoparticle carrier.

[0071] In some embodiments of the present invention, the alkaline solution is a sodium hydroxide solution or a potassium hydroxide solution, and the concentration of the alkaline solution is 0.8~1.2 mol / L, specifically 0.8 mol / L, 0.9 mol / L, 1.0 mol / L, 1.1 mol / L or 1.2 mol / L, etc.

[0072] In some embodiments of the present invention, the ion exchange reaction is carried out at a temperature of 30-50°C, specifically 30°C, 33°C, 35°C, 37°C, 40°C, 45°C, or 50°C, etc.; and the reaction time is 4-6 h, specifically 4 h, 4.5 h, 5 h, 5.5 h, or 6 h, etc.

[0073] In some embodiments of the present invention, after the ion exchange reaction is completed, the resulting solid-liquid mixture is subjected to solid-liquid separation, washing, and drying to obtain an ultra-high cross-linked nanoparticle catalyst.

[0074] A second typical embodiment of the present invention provides a nanocatalyst for the synthesis of dimethyl carbonate, which is prepared by the above-described preparation method.

[0075] The highly cross-linked nanoparticle catalyst prepared in this invention is a nano-solid particle formed by the polymerization of biphenyl dichlorobenzyl monomer. The particles have abundant micropores and mesopores, and their surface is modified with imidazole chloride. The particles undergo ion exchange to remove chloride ions and exchange hydroxyl anions. The highly cross-linked nanoparticle catalyst prepared in this invention exhibits good cycling performance and can efficiently catalyze the one-pot synthesis of dimethyl carbonate from propylene oxide, methanol, and carbon dioxide under mild conditions. Therefore, a third typical embodiment of this invention provides an application of the above-mentioned nanocatalyst in the synthesis of dimethyl carbonate.

[0076] In some embodiments of the present invention, the synthesis of dimethyl carbonate is carried out by: mixing propylene oxide, methanol and the nanocatalyst in a carbon dioxide atmosphere, heating and stirring to react, and synthesizing dimethyl carbonate in a one-pot process.

[0077] A third aspect of the present invention provides a method for one-pot synthesis of dimethyl carbonate, comprising the following steps:

[0078] In a carbon dioxide atmosphere, propylene oxide, methanol, and the aforementioned nanocatalyst are mixed and heated with stirring to synthesize dimethyl carbonate in a one-pot process.

[0079] In some embodiments of the present invention, the ratio of propylene oxide, methanol and nanocatalyst is 1:1:5 to 8, mol / mol / g, specifically 1:1:5, 1:1:6, 1:1:7 or 1:1:8, etc.

[0080] In some embodiments of the present invention, the heating and stirring reaction is carried out at a temperature of 50-70°C, specifically 50°C, 53°C, 55°C, 57°C, 60°C, 65°C, or 70°C; and the reaction time is 8-12 h, specifically 8 h, 8.5 h, 9 h, 9.5 h, 10 h, 10.5 h, 11 h, 11.5 h, or 12 h.

[0081] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0082] All raw materials used in the following examples are commercially available.

[0083] Example 1

[0084] A method for preparing the highly cross-linked nanoparticle catalyst PBCMB-ImC8-OH according to the present invention, the method comprising the following steps:

[0085] 1. Under a nitrogen atmosphere, biphenyl dichlorobenzyl chloride (BCMB) and dichloroethane solvent were added to a 500 mL reaction flask at a ratio of 1:12.5 (g / mL) and stirred. The preheating temperature was controlled at 50℃. After preheating for 30 minutes, ferric chloride catalyst (BCMB to ferric chloride mass ratio of 4:1) was added to the reaction flask to carry out the Friedel-Crafts reaction. The reaction temperature was controlled at 90℃. The reaction was stopped after 10 hours. The resulting solid-liquid mixture was subjected to solid-liquid separation, washed, and dried to obtain the ultra-highly cross-linked nanoparticle carrier PBCMB.

[0086] 2. The highly cross-linked nanoparticle carrier PBCMB obtained in step 2 and 1-octyl-3-methylimidazolium chloride (ImC8) (molar ratio 1:1.2) were dissolved in isopropanol solvent (PBCMB mass to solvent volume ratio 1:12.5, g / mL); and added to a 500 mL reaction flask for nucleophilic substitution reaction. The reaction temperature was controlled at 70℃, and the reaction was stopped after 10 hours. The resulting solid-liquid mixture was subjected to solid-liquid separation, washed, and dried to obtain the imidazole-modified highly cross-linked nanoparticle carrier PBCMB-ImC8-Cl.

[0087] 3. The imidazole-modified ultra-high crosslinked nanoparticle support obtained in step 2 was dissolved in 1 mol / L potassium hydroxide solution for ion exchange reaction. The reaction was stopped after 5 hours at 40℃. The resulting solid-liquid mixture was separated, washed, and dried to obtain the ultra-high crosslinked nanoparticle catalyst PBCMB-ImC8-OH. The obtained catalyst was characterized by SEM, TEM and XPS.

[0088] Figure 1 The image shown is a SEM image of the catalyst prepared in Example 1 of this invention. Figure 1 It is known that the size of a single catalyst particle is around 50-100 nm. Due to the strong adsorption force formed by the high specific surface area of ​​the nanoparticles, the nanoparticles aggregate into clusters of large particles. Figure 2 This is a TEM image of the catalyst prepared in Example 1 of the present invention. Figure 2 This further demonstrates that the size of individual catalyst particles is 50-100 nm. Figure 3 The above is an XPS full spectrum image of the catalyst prepared in Example 1 of this invention. Figure 3 It is known that the catalyst contains three elements: C, N, and O, indicating the success of alkyl chain imidazole chloride modification and potassium hydroxide ion exchange. Figure 4 This is a high-resolution XPS N1s spectrum image of the catalyst prepared in Example 1 of this invention. Figure 4 It can be seen that the binding energy of N1s is 401.9 eV, which is CN. + The binding energy of the valence state further demonstrates the success of the modification of the alkyl chain imidazole chloride salt. The bound chlorine on the surface of the PBCMB precursor is replaced, forming an ionic compound in which the PBCMB-ImC8 cation pairs with the free chloride anion.

[0089] Example 2

[0090] The only difference between Example 2 and Example 1 is that in step 2, 1-octyl-3-methylimidazolium chloride (Im C8) is replaced with 1-hexyl-3-methylimidazolium chloride (Im C6), while the other steps, parameters and raw materials remain unchanged.

[0091] Example 3

[0092] The only difference between Example 3 and Example 1 is that in step 2, 1-octyl-3-methylimidazolium chloride (Im C8) is replaced with 1-decyl-3-methylimidazolium chloride (Im C8). 10 (The other steps, parameters and raw materials remain unchanged.)

[0093] Comparative Example 1

[0094] The only difference between Comparative Example 1 and Example 1 is that in step 1, the reaction temperature of the Friedel-Crafts reaction was adjusted to 130°C, while the other steps, parameters and raw materials remained unchanged.

[0095] Comparative Example 2

[0096] The only difference between Comparative Example 2 and Example 1 is that in step 1, the reaction temperature of the Friedel-Crafts reaction was adjusted to 50°C, while other steps, parameters and raw materials remained unchanged.

[0097] Comparative Example 3

[0098] The only difference between Comparative Example 3 and Example 1 is that in step 1, the mass ratio of BCMB to ferric chloride is 10:1, while other steps, parameters and raw materials remain unchanged.

[0099] Comparative Example 4

[0100] The only difference between Comparative Example 4 and Example 2 is that in step 2, the molar ratio of the carrier PBCMB and 1-octyl-3-methylimidazolium chloride (Im C8) is adjusted to 1:1, while other steps, parameters and raw materials remain unchanged.

[0101] Comparative Example 5

[0102] The only difference between Comparative Example 5 and Example 1 is that in step 3, the concentration of potassium hydroxide was adjusted to 0.6 mol / L, the ion exchange reaction time was adjusted to 2 hours, and other steps, parameters and raw materials remained unchanged.

[0103] Performance verification

[0104] The catalytic performance of the catalysts prepared in the above examples and comparative examples was verified. The method steps for the one-pot synthesis of dimethyl carbonate using ultra-highly cross-linked nanoparticle catalysts under mild conditions are as follows:

[0105] 1. In a carbon dioxide atmosphere, propylene oxide, methanol, and ultra-high cross-linked nanoparticle catalyst were added to a reaction flask and heated and stirred. The molar ratio of epichlorohydrin to methanol to catalyst was 1 mol: 1 mol: 5 g. The reaction temperature was 70℃ and the reaction time was 10 hours.

[0106] 2. After the reaction is complete, the resulting solid-liquid mixture is separated into solid and liquid components. The liquid portion is analyzed by GC. The solid catalyst is washed and dried. Step 1 is repeated for 5 cycles.

[0107] The experimental results are shown in Table 1.

[0108] Table 1. Catalyst properties and catalytic performance data for Examples 1-3 and Comparative Examples 1-5.

[0109]

[0110] As shown in Table 1, Examples 1-3 demonstrate that the catalysts synthesized using the technical solution provided by this invention have a high nitrogen content, reaching 6-7%, indicating a high imidazole loading; and a high specific surface area, reaching 800 m². 2 The presence of pores above a certain value (e.g., g / g) indicates that the catalyst synthesized using the technical solution provided by this invention has numerous pores, increasing the contact between the catalyst and the substrate. Among these, the catalyst PBCMB-ImC8-OH provided in Example 1 exhibits the highest catalytic efficiency, achieving a yield of 96% and a selectivity of 99%. After 5 cycles, the yield remains at 93% and the selectivity at 99%, demonstrating the excellent cycling performance of this catalyst. In Comparative Examples 1 and 2, the reaction temperatures of the Friedel-Crafts reaction were adjusted to 130℃ and 50℃, respectively, resulting in a decrease in the specific surface area of ​​the obtained catalysts to 341.21 m². 2 / g and 572.26m 2 The catalytic yield decreased to 35% and 47% in Comparative Example 3, indicating incomplete catalyst support synthesis, a decrease in specific surface area, reduced catalyst-substrate contact, and decreased catalytic efficiency. In Comparative Example 4, the amount of ferric chloride used in the Friedel-Crafts reaction was reduced to one-tenth of the mass of BCMB, indicating incomplete catalyst support synthesis, a decrease in surface area, and decreased catalytic efficiency. In Comparative Example 5, the molar ratio of the support PBCMB and 1-octyl-3-methylimidazolium chloride (Im C8) was adjusted to 1:1, and the nitrogen content decreased from 6.71% to 6.01%, resulting in a decrease in imidazole loading and catalytic efficiency. Comparative Example 5 and Example 1 were identical except for the potassium hydroxide concentration. In Comparative Example 5, the potassium hydroxide concentration was adjusted to 0.6 mol / L, and the ion exchange reaction time was adjusted to 2 hours. Insufficient hydroxide ion exchange resulted in a decrease in catalytic efficiency compared to Example 1.

[0111] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a nanocatalyst for the synthesis of dimethyl carbonate, characterized in that, Includes the following steps: Biphenyl dichlorobenzyl was dissolved in an alkylating agent and subjected to a Friedel-Crafts reaction under catalytic conditions. After the reaction was completed, a highly cross-linked nanoparticle carrier was obtained. The Friedel-Crafts reaction is carried out at a temperature of 70-90°C for a time of 8-12 hours. The highly cross-linked nanoparticle carrier and imidazole chloride were dissolved in a solvent and subjected to a nucleophilic substitution reaction under heating and stirring conditions. After the reaction was completed, an imidazole-modified highly cross-linked nanoparticle carrier was obtained. The imidazole chloride salt is selected from any one of 1-decyl-3-methylimidazolium chloride, 1-octyl-3-methylimidazolium chloride, and 1-hexyl-3-methylimidazolium chloride; The molar ratio of the imidazole chloride to the ultra-highly cross-linked nanoparticle carrier is 1.1~1.3:1; The nucleophilic substitution reaction is carried out at a temperature of 70-90℃ for a time of 8-12 h. The imidazole-modified ultra-high cross-linked nanoparticle support was dissolved in an alkaline solution and subjected to an ion exchange reaction under heating conditions. After the reaction was completed, an ultra-high cross-linked nanoparticle catalyst was obtained. The alkaline solution is a sodium hydroxide solution or a potassium hydroxide solution, and the concentration of the alkaline solution is 0.8~1.2 mol / L; The ion exchange reaction is carried out at a temperature of 30-50°C for a time of 4-6 hours. The catalyst has a specific surface area of ​​800 m². 2 The catalyst has an imidazole loading of 6%-7% at a rate of 1 / g or higher.

2. The preparation method according to claim 1, characterized in that, The alkylating agent includes one of the following: haloalkane, alkyllithium, alkylcopper, alkylaluminum, alkylmagnesium, or alcohol.

3. The preparation method according to claim 1, characterized in that, The catalyst includes one of anhydrous aluminum trichloride, ferric trichloride, or boron trifluoride.

4. The preparation method according to claim 1, characterized in that, Under a protective atmosphere, biphenyl dichlorobenzyl was dissolved in an alkylating agent, stirred and preheated, a catalyst was added, and the mixture was heated to carry out a Friedel-Crafts reaction. The ratio of biphenyl dichlorobenzyl to the alkylating agent is 1:10~15, g / mL; The mass ratio of biphenyl dichlorobenzyl to the catalyst is 3~5:1; The preheating temperature is 40~60℃, and the preheating time is 20~40 min.

5. The preparation method according to claim 1, characterized in that, The ratio of the ultra-highly cross-linked nanoparticle carrier to the solvent is 1:10~15, g / mL.

6. A nanocatalyst for the synthesis of dimethyl carbonate, characterized in that, It is prepared by any of the preparation methods described in claims 1-5.

7. The application of the nanocatalyst according to claim 6 in the synthesis of dimethyl carbonate; The synthesis of dimethyl carbonate is carried out by mixing propylene oxide, methanol and the nanocatalyst in a carbon dioxide atmosphere, heating and stirring to synthesize dimethyl carbonate in a one-pot process.

8. A method for one-pot synthesis of dimethyl carbonate, characterized in that, Includes the following steps: In a carbon dioxide atmosphere, propylene oxide, methanol, and the nanocatalyst described in claim 6 are mixed and heated with stirring to synthesize dimethyl carbonate in a one-pot process.

9. The method as described in claim 8, characterized in that, The ratio of propylene oxide, methanol, and nanocatalyst is 1:1:5~8, mol / mol / g.

10. The method as described in claim 8, characterized in that, The heating and stirring reaction is carried out at a temperature of 50-70℃ for 8-12 hours.

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