Catalyst for efficient coal-based synthesis of dimethyl carbonate and preparation method thereof

Abstract

The invention relates to the technical field of catalyst preparation, and particularly discloses a catalyst for efficient coal-based synthesis of dimethyl carbonate and a preparation method thereof.The catalyst comprises, by weight, 85%-88% of a coal-based activated carbon carrier, 7%-8% of copper oxide, 3%-4% of zinc oxide, 1%-2% of aluminum oxide and 1%-2% of rare earth oxide; the coal-based carbon material is used as the carrier, so that the thermal stability and the surface adsorption capacity of the catalyst are remarkably improved; after CeO2 is introduced, the redox cycle efficiency is improved, and the methanol conversion rate and DMC selectivity are enhanced; a pore structure is improved through a coal tar blending carbonization technology, and reactant molecule diffusion and product desorption are facilitated; the catalyst is stable in structure, long in continuous reaction time and good in renewability and industrial adaptability, organic functional groups in coal can be directionally reserved through multiple treatment means, high-density defect sites can be constructed, and the loading performance of the catalyst is enhanced.

Description

Technical Field

[0001] The invention belongs to the technical field of catalyst preparation, and in particular relates to a high-efficiency coal-based catalyst for synthesizing dimethyl carbonate and a preparation method thereof. Background Art

[0002] With the transformation of the global energy structure and the growth of green chemical demand, the efficient synthesis of dimethyl carbonate (DMC) from coal-based raw materials has become a key path to alleviate dependence on petroleum resources and achieve the upgrading of the carbon-one chemical industry. However, the existing coal-based synthesis of DMC technology faces the dual challenges of catalyst performance bottleneck and insufficient process adaptability.

[0003] At the catalyst level, although traditional coal-based carriers (such as activated carbon and graphitized carbon) have certain adsorption capabilities, they have poor thermal stability and uneven distribution of surface active sites, which makes the catalytic activity susceptible to fluctuations in reaction conditions. At the same time, supported metal oxides (such as Cu-Zn-Al system) are prone to sintering and agglomeration during high-temperature reactions, significantly reducing the catalytic life. In addition, although rare earth modification technology can improve the mobility of oxygen species, existing modification methods mostly rely on high-cost nanomaterials or complex co-precipitation processes, which are difficult to achieve industrial application.

[0004] In terms of preparation technology, the preparation of coal-based carbon materials generally adopts a two-step method of high-temperature carbonization-activation, which has defects such as high energy consumption and difficulty in controlling the pore structure. On the one hand, high-temperature treatment can easily destroy the inherent organic functional groups in coal and reduce the interaction strength between the carrier and the active components; on the other hand, the amount of activator (such as KOH) is difficult to accurately control, resulting in uneven distribution of micropores and mesoporous structures, affecting the diffusion efficiency of reactant molecules. In addition, in the preparation of traditional catalysts, the loading of metal active components mostly adopts the impregnation-drying method, which has problems such as poor dispersion of metal ions and low pH control accuracy during the co-precipitation process, making it difficult to form a highly active Cu-Zn-Al composite oxide interface.

[0005] The common deficiencies in the existing technologies can be summarized as follows: (1) The thermal stability and surface active site density of coal-based carriers are insufficient, resulting in limited catalytic efficiency; (2) The metal oxide loading process lacks directional control means, making it difficult to achieve high dispersion of active components and synergy with anti-sintering; (3) The rare earth modification method is costly and complex, making it difficult to meet the needs of industrial production; (4) The poor coupling between coal-based carbon material preparation and catalyst loading process limits the improvement of overall reaction performance. These defects jointly restrict the economic feasibility and large-scale application potential of coal-based DMC synthesis technology.

[0006] In view of this, the inventors proposed a highly efficient coal-based catalyst for synthesizing dimethyl carbonate and a preparation method thereof to solve the above problems. Summary of the invention

[0007] The object of the present invention is to provide a catalyst for efficiently synthesizing dimethyl carbonate based on coal and a preparation method thereof, so as to solve the problems raised in the above-mentioned background technology.

[0008] To achieve the above object, the present invention provides the following technical solutions:

[0009] A catalyst for efficiently synthesizing dimethyl carbonate based on coal, the catalyst comprises the following components in percentage by weight:

[0010] Coal-based activated carbon carrier: 85% - 88%, copper oxide: 7% - 8%, zinc oxide: 3% - 4%, aluminum oxide: 1% - 2%, rare earth oxide: 1% - 2%.

[0011] Preferably, the copper oxide is CuO, the zinc oxide is ZnO, the aluminum oxide is Al2O3, and the rare earth oxide is CeO2 or La2O3.

[0012] A preparation method of a catalyst for efficiently synthesizing dimethyl carbonate based on coal, which is characterized by comprising the following steps:

[0013] S1. Pretreatment and expansion of coal-based raw materials: Select coal raw materials with low ash content and high volatile content, crush them to below 200 meshes, mix the crushed coal with coal tar at a mass ratio of 1:1, and add a surfactant relative to 2% of the weight of the coal, and fully stir at 200 °C for 4 hours to loosen the organic structure in the coal and obtain an expanded coal slurry;

[0014] S2. Crosslinking stabilization treatment: Add a sodium gluconate solution to the expanded coal slurry, stir and react at 120 °C for 2 hours and then stand for 12 hours to slowly dehydrate and crosslink the hydroxyl and carboxyl groups in the coal slurry to generate a crosslinked coal precursor;

[0015] S3. Directionally induced carbonization to construct functionalized coal-based carbon: Mix and impregnate the crosslinked coal precursor with a catalytic carbonization inducer for 6 hours and then dry it, and carbonize it at 550 °C at a heating rate of 3 °C / min under nitrogen protection for 2 hours to directionally induce the formation of a functionalized material with a high specific surface area and functional group enrichment to obtain a coal-based carbon material;

[0016] S4. Multi-stage pore structure regulation and surface hydrophobic modification: Mix the coal-based carbon material with KOH at a mass ratio of 1:3, activate it in a nitrogen atmosphere at 800 °C for 1 hour to obtain a coal-based carbon material with a hierarchical microporous-mesoporous structure, immerse the coal-based carbon material with the hierarchical microporous-mesoporous structure in an ethanol-tetrahydrofuran mixed solution, add trimethoxysilane and carry out a reflux reaction for 4 hours to regulate its surface polarity and achieve hydrophobic modification to obtain a coal-based carbon carrier;

[0017] S5. Uniform loading of metal active components and co-precipitation construction: Prepare a mixed solution containing copper nitrate, zinc nitrate, and aluminum nitrate, and simultaneously add an appropriate amount of citric acid as a complexing stabilizer; use it to uniformly impregnate the coal-based carbon carrier to obtain a solid loaded with a uniform metal precursor; slowly drop a solution containing sodium bicarbonate into the solid of the metal precursor until the pH of the reaction system is adjusted to 8.5, and maintain constant temperature stirring for 3 hours to promote the co-precipitation of metal ions to form a Cu-Zn-Al composite hydroxide;

[0018] S6. Calcination thermal conversion and multi-metal oxide construction: Heat the hydroxide obtained by co-precipitation in air at a heating rate of 10 °C / min to 400 °C, and calcine at this temperature for 4 hours to convert it into a Cu-Zn-Al-O multi-metal oxide composite material with a stable structure;

[0019] S7. Rare earth regulation and enhancement of oxygen activity modification: Mix the calcined product with a cerium nitrate solution and impregnate for 6 hours; use it to introduce a rare earth modification regulator, and obtain a final modified catalyst with a high oxygen vacancy density and Ce 3+ / Ce 4+ conversion ability through subsequent drying and calcination at 300 °C for 2 hours.

[0020] Preferably, the concentration of the sodium gluconate solution is 10%, and the solid-liquid ratio of the expanded coal slurry to the sodium gluconate solution is 1:5.

[0021] Preferably, the catalytic carbonization inducer is composed of ZnCl2 and urea, and the molar ratio is 1:1.

[0022] Preferably, the metal molar ratio in the mixed solution of copper nitrate, zinc nitrate, and aluminum nitrate is 1:0.5:0.2.

[0023] Preferably, the impregnation condition of the cerium nitrate solution is a Ce / Cu molar ratio of 0.1, which can not only ensure the full modification of the composite material surface by rare earth elements but also optimize the storage and release performance of oxygen species.

[0024] Compared with the prior art, the beneficial effects of the present invention are:

[0025] (1) The present invention uses a coal-based carbon material as a carrier to significantly improve the thermal stability and surface adsorption capacity of the catalyst; after introducing CeO2, the redox cycle efficiency is enhanced, and the methanol conversion rate and DMC selectivity are improved; the pore structure is improved through the coal tar co-blending carbonization technology, which is beneficial to the diffusion of reactant molecules and the desorption of products; the catalyst has a stable structure, a long continuous reaction time, and good renewable and industrial adaptability.

[0026] (2) In the present invention, the multiple treatment means (pyrolysis-hydrothermal-acid washing) can directionally retain the organic functional groups in coal and construct high-density defect sites, enhancing the catalyst loading performance; the defect structure improves the anchoring stability of the active metal, enhancing the catalytic activity and reaction selectivity; the high specific surface area and rich pore structure provide more reaction active centers and excellent mass transfer paths; the carrier raw materials are widely sourced, low in cost, the treatment process is green and environmentally friendly, and it has the potential for large-scale application. Description of the Drawings

[0027] Figure 1 It is a flow chart of a preparation method of a catalyst for efficiently synthesizing dimethyl carbonate based on coal in the present invention. Detailed Embodiments

[0028] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0029] Example 1:

[0030] Please refer to Figure 1 As shown, the application of a catalyst based on coal-based modified carbon supported copper-zinc-aluminum composite oxide in the synthesis of dimethyl carbonate:

[0031] Catalyst preparation:

[0032] Coal-based raw material pretreatment:

[0033] Anthracite is selected. After being pulverized (below 200 mesh), 100 g of coal powder is weighed and mixed with 100 g of coal tar, and 2 g of quaternary ammonium salt surfactant is added.

[0034] Stir at 200 °C for 4 hours to obtain an expanded coal slurry.

[0035] Crosslinking stabilization treatment:

[0036] Add a 10 wt% sodium gluconate solution (liquid-solid ratio 5:1) to the expanded coal slurry, stir at 120 °C for 2 hours and then stand for 12 hours to form a crosslinked coal precursor.

[0037] Directional induced carbonization:

[0038] Mix the precursor with a mixed solution containing ZnCl2 and urea (molar ratio of ZnCl2:urea 1:1, impregnate for 6 hours and then dry), place it under nitrogen protection, heat it to 550 °C at a rate of 3 °C / min, and carbonize for 2 hours to obtain a functionalized coal-based carbon material.

[0039] Hierarchical pore structure regulation and surface modification:

[0040] A coal-based carbon material with mixed functionality and KOH (mass ratio 1:3) was activated in a nitrogen atmosphere at 800 °C for 1 hour to obtain a coal-based carbon material with a hierarchical pore structure.

[0041] The coal-based carbon material was immersed in a mixed solution of ethanol and tetrahydrofuran, trimethoxysilane was added, and after refluxing for 4 hours, it was washed and dried to obtain a hydrophobically modified support.

[0042] Loading of metal components and co-precipitation construction:

[0043] A mixed solution containing copper nitrate, zinc nitrate, and aluminum nitrate (molar ratio 1:0.5:0.2) was prepared, and citric acid (about 5 wt% of the total metal content, acting as a complexing agent) was added;

[0044] The support and the solution were impregnated at a liquid-solid ratio of 5:1 for 12 hours and then dried at 80 °C to obtain a solid;

[0045] A 10 wt% sodium bicarbonate solution was slowly added dropwise to adjust the pH to 8.5, and the mixture was stirred at a constant temperature for 3 hours to promote the co-precipitation of metal ions to form a Cu-Zn-Al composite hydroxide precipitate.

[0046] Calcination and thermal conversion:

[0047] The precipitate was heated in air at a rate of 10 °C / min to 400 °C and calcined for 4 hours to thermally convert it into a Cu-Zn-Al-O composite oxide, while ensuring that the final copper, zinc, and aluminum components in the catalyst were 7 wt%, 3 wt%, and 2 wt% respectively, and the coal-based support accounted for 88 wt%.

[0048] Rare earth regulation and modification:

[0049] The Cu-Zn-Al-O composite oxide was mixed with a cerium nitrate solution (Ce / Cu molar ratio 0.1), impregnated at room temperature for 6 hours, dried, and then calcined at 300 °C for 2 hours to finally obtain a modified catalyst containing 1-2 wt% CeO2.

[0050] Catalytic application and testing of the modified catalyst:

[0051] Experimental conditions:

[0052] Reactor: Fixed-bed reactor, catalyst loading 5 g.

[0053] Reaction temperature: 120 °C; reaction pressure: 2.0 MPa;

[0054] Feed gases and liquids: CO, O2, and methanol were supplied in a molar ratio of 2:1:4 and quantitatively transported by a pump.

[0055] Reaction time: continuous operation for 120 hours.

[0056] The product was analyzed by on-line gas chromatography (GC) and confirmed by mass spectrometry (MS).

[0057] The conversion and selectivity data were quantified according to the standard curve and the internal standard method. The catalyst was characterized by BET to determine the specific surface area, XRD to identify the crystal phase, and SEM / TEM to observe the morphology and metal dispersion state.

[0058] Test results:

[0059] Methanol conversion: 86.5%;

[0060] Selectivity to dimethyl carbonate (DMC): 96.2%;

[0061] The initial activity of the catalyst remained without obvious attenuation within 120 hours of continuous operation;

[0062] The BET-measured carrier surface area was about 850 m 2 / g, and the pore size distribution coexisted with micropores and mesopores;

[0063] The XRD results showed that the crystal structure of Cu-Zn-Al-O was clear and CeO2 was in a nano-dispersed state.

[0064] Control Example 1 (comparison of preparation and application of traditional coal-based catalysts):

[0065] Preparation method (control scheme):

[0066] A coal-based catalyst was prepared by a traditional method, with the main difference being that the steps of swelling, cross-linking, and directional carbonization of the coal-based raw materials in this scheme were not adopted, but a conventional pyrolysis and single-step activation process was used:

[0067] Carbonization of coal-based raw materials:

[0068] 100 g of pulverized coal was directly mixed with coal tar (mass ratio 1:0.5, without adding surfactant), and then simply stirred at 200 °C for 2 hours.

[0069] It was directly placed in nitrogen and heated to 600 °C at a rate of 5 °C / min and carbonized for 2 hours to obtain a coal-based carbonized product.

[0070] Conventional KOH activation:

[0071] The coal-based carbonized product was mixed with KOH at a mass ratio of 1:3 and activated in nitrogen at 800 °C for 1 hour to obtain activated carbon. The BET-measured specific surface area was about 550 m 2 / g, and the pore structure was relatively single.

[0072] Metal loading and calcination:

[0073] The activated carbon was impregnated with a mixed solution containing copper nitrate, zinc nitrate, and aluminum nitrate (molar ratio 1:0.5:0.2, without adding a complexing agent), then simply dried, and directly calcined in air at a heating rate of 10 °C / min to 400 °C for 4 hours to obtain a Cu-Zn-Al-O composite catalyst;

[0074] The Cu-Zn-Al-O composite catalyst was mixed with a cerium nitrate solution, impregnated for 6 hours, dried, and calcined at 300 °C for 2 hours to obtain a modified catalyst. In its final composition, the metal component content remained approximately the same as in Example 1 (copper 7-8 wt%, zinc 3-4 wt%, aluminum 1-2 wt%, CeO2 1-2 wt%), but the proportion of the coal-based carbon in the carrier was 92-94 wt%.

[0075] Catalytic application and testing:

[0076] Experimental conditions: Consistent with Example 1 (fixed-bed reactor, catalyst loading 5 g, 120 °C, 2.0 MPa, CO / O2 / methanol molar ratio 2:1:4), and the continuous operation test time was 120 hours.

[0077] Test results:

[0078] Methanol conversion rate: 73.2%;

[0079] DMC selectivity: 81.5%;

[0080] The stability of continuous operation was poor, and the activity decreased significantly after 80 hours, and the conversion rate at 120 hours decreased to 65%;

[0081] The specific surface area of the carrier measured by BET was only about 560 m 2 / g, the pore structure was single, and the metal dispersion uniformity was insufficient;

[0082] XRD analysis showed that the agglomeration of some metal oxides was obvious, and CeO2 could not be completely nanodispersed.

[0083] Description of the comparative example:

[0084] Activity difference:

[0085] The coal-based carrier F obtained by multi-step pretreatment (swelling, cross-linking, directional carbonization, and surface hydrophobic modification) in Example 1 had a high specific surface area of about 850 m 2 / g, which was significantly higher than 560 m obtained by single activation in Comparative Example 1 2 / g.

[0086] In addition, the hierarchical pore structure of the support significantly improves the transport efficiency of reactants in the catalyst bed, directly leading to an increase in the methanol conversion rate from 73.2% in the control to 86.5%, and an increase in the DMC selectivity from 81.5% to 96.2%.

[0087] Catalytic stability:

[0088] The catalyst in Example 1 showed stable activity within 120 consecutive hours without obvious decline; while the control catalyst was significantly deactivated after 80 hours, and the conversion rate dropped to 65% after 120 hours, indicating insufficient anti-sintering and anti-agglomeration capabilities.

[0089] Characterization data:

[0090] Comparing the XRD, SEM / TEM data shows that in Example 1, both the metal components and CeO2 are uniformly dispersed on the surface of the support in a nanoscale state, and the synergistic effect of metal loading is fully exerted; while in the control example, obvious agglomeration of some metal components exists, limiting the reaction activity.

[0091] Table 1 below is a comparison table of the performance parameters of the above catalysts;

[0092] Table 1: Performance comparison between the catalyst in Example 1 and the comparative catalyst

[0093]

[0094]

[0095] As can be seen from the above, using the coal-based carbon material as the support significantly improves the thermal stability and surface adsorption capacity of the catalyst;

[0096] After introducing CeO2, the redox cycle efficiency is improved, enhancing the methanol conversion rate and DMC selectivity;

[0097] The pore structure is improved through the coal tar co-blending carbonization technology, which is beneficial to the diffusion of reactant molecules and the desorption of products;

[0098] The catalyst has a stable structure, a long continuous reaction time, and good regenerability and industrial adaptability.

[0099] Example 2:

[0100] Improved rare earth regulation scheme:

[0101] Preparation method: On the basis of Example 1, La2O3 assistance is added;

[0102] Pre-step: Perform the same pre-treatment, cross-linking, directional carbonization, multi-stage activation and surface modification steps as in Example 1 to obtain a hydrophobic modified coal-based carbon support.

[0103] Metal loading and coprecipitation construction:

[0104] The carrier was impregnated with a mixed solution of copper nitrate, zinc nitrate, and aluminum nitrate (molar ratio 1:0.5:0.2) and citric acid was added, and impregnated for 12 hours at a liquid-solid ratio of 5:1;

[0105] Sodium bicarbonate was added to adjust the pH to 8.5, and coprecipitation was carried out for 3 hours to form a composite hydroxide precipitate H.

[0106] Calcination heat conversion:

[0107] The precipitate was calcined in air at a heating rate of 10 °C / min to 400 °C for 4 hours to produce a Cu-Zn-Al-O composite oxide.

[0108] Rare earth-alkaline earth double modification:

[0109] The Cu-Zn-Al-O composite oxide was mixed with a cerium nitrate solution (Ce / Cu molar ratio 0.1), and at the same time, a mixed solution of cerium nitrate and aluminum nitrate in a certain proportion (La / Cu molar ratio 0.05) was added for co-impregnation for 6 hours. After drying, it was calcined at 300 °C for 2 hours to obtain the final composite modified catalyst, which contained 1% CeO2 and 1% La2O3, and the overall metal component to carrier ratio was kept basically the same as in Example 1.

[0110] Catalytic application and testing:

[0111] Experimental conditions: The same fixed-bed reactor was used, the catalyst loading was 5 g, the reaction temperature was 120 °C, the pressure was 2.0 MPa, the CO / O2 / methanol molar ratio was 2:1:4, and the continuous operation time was set to 140 hours, focusing on long-term stability testing.

[0112] Test results:

[0113] Methanol conversion rate: about 88.0%;

[0114] DMC selectivity: about 97.0%;

[0115] The activity remained stable within 140 hours of continuous operation. After multiple cycle tests, the performance recovery rate reached over 95% after thermal regeneration treatment;

[0116] Characterization data showed that the double rare earth regulation increased the surface oxygen vacancy concentration of the catalyst by about 20%, and at the same time, the metal components were more evenly dispersed, and the specific surface area of the carrier remained between 840–860 m 2 / g.

[0117] Description of the comparative example:

[0118] Comparison with Example 1:

[0119] In Example 2, after La2O3 was introduced into the catalyst for auxiliary modification, the methanol conversion rate was further improved by about 2 to 3 percentage points (from 86.5% to about 88.0%), and the DMC selectivity was increased from 96.2% to 97.0%, proving that dual rare earth regulation (Ce and La synergistically) further improved the oxygen storage and surface reconstruction capabilities.

[0120] In the long-term stability test, Example 2 had no obvious deactivation within 140 hours and could quickly recover its activity after periodic thermal regeneration, while Example 1 was only tested to 120 hours and had a slightly shorter replacement cycle.

[0121] Data acquisition instructions:

[0122] All reaction data were collected regularly by online GC, with data sampled every 10 minutes, and compared and analyzed in combination with the BET, XRD, SEM / TEM and other characterization results of the catalyst before and after the experiment;

[0123] In addition, to verify the change of oxygen vacancies, XPS was used to detect and analyze the Ce on the catalyst surface. 3+ / Ce 4+ ,La 3+ / La 4+ Compared with the traditional single Ce-regulated catalyst, the two-phase regulation in Example 2 achieves a synergistic enhancement effect, further demonstrating the advancement of this scheme in regulating catalytic activity.

[0124] The comparison of the effects of different coal-based carbon material sources on catalytic performance in Example 2 is shown in Table 2 below:

[0125] Table 2

[0126]

[0127] Note: The data of physical and chemical properties of the carrier are obtained by BET, FTIR and Raman spectroscopy.

[0128] From the above, it can be seen that multiple treatment methods (pyrolysis-hydrothermal-acid washing) can directionally retain organic functional groups in coal and construct high-density defect sites, thereby enhancing catalyst loading performance;

[0129] The defect structure improves the anchoring stability of the active metal, enhancing the catalytic activity and reaction selectivity;

[0130] High specific surface area and rich pore structure provide more reactive centers and excellent mass transfer paths;

[0131] The carrier raw materials are widely available and low in cost, the processing process is green and environmentally friendly, and it has the potential for large-scale application.

[0132] In the description of this specification, the descriptions referring to terms such as "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in a suitable manner in any one or more embodiments or examples. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0133] In the drawings of the disclosed embodiments of the present invention, only the structures related to the disclosed embodiments are involved, and other structures can refer to the general design. Without conflict, the same embodiment and different embodiments of the present invention can be combined with each other.

[0134] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A highly efficient coal-based catalyst for synthesizing dimethyl carbonate, characterized in that: The catalyst comprises the following components in percentage by weight: Coal-based activated carbon carrier: 85% to 88%, copper oxide: 7% to 8%, zinc oxide: 3% to 4%, aluminum oxide: 1% to 2%, rare earth oxide: 1% to 2%.

2. A highly efficient coal-based catalyst for synthesizing dimethyl carbonate according to claim 1, characterized in that: The copper oxide is CuO, the zinc oxide is ZnO, the aluminum oxide is Al2O3, and the rare earth oxide is CeO2 or La2O3.

3. A method for preparing a highly efficient coal-based catalyst for synthesizing dimethyl carbonate according to any one of claims 1 to 2, characterized in that: The following steps are involved: S1. Grinding the coal raw material to less than 200 meshes to obtain the pulverized coal and coal tar, mixing the pulverized coal and coal tar in a mass ratio of 1:1, adding 2% of a surfactant relative to the weight of the coal, and fully stirring at 200° C. for 4 hours to obtain an expanded coal slurry; S2, adding sodium gluconate solution to the expanded coal slurry, stirring and reacting at 120° C. for 2 hours and standing for 12 hours to generate a cross-linked coal precursor; S3, mixing the cross-linked coal precursor and the catalytic carbonization inducer, impregnating for 6 hours, drying, and carbonizing at 550° C. at 3° C. / min for 2 hours under nitrogen protection to obtain a coal-based carbon material; S4, mixing the coal-based carbon material with KOH in a mass ratio of 1:3, and activating the mixture in a nitrogen atmosphere at 800° C. for 1 hour to obtain a coal-based carbon material with a hierarchical micropore-mesoporous structure; The coal-based carbon material with hierarchical micropore-mesoporous structure is immersed in an ethanol-tetrahydrofuran mixed solution, and trimethoxysilane is added to carry out reflux reaction for 4 hours to obtain a coal-based carbon carrier; S5, preparing a mixed solution containing copper nitrate, zinc nitrate and aluminum nitrate, and adding an appropriate amount of citric acid as a complex stabilizer to obtain a solid loaded with a uniform metal precursor; Slowly adding a sodium bicarbonate solution to the solid of the metal precursor until the pH of the reaction system is adjusted to 8.5, and stirring at a constant temperature for 3 hours to promote the coprecipitation of metal ions to form a Cu-Zn-Al composite hydroxide; S6, heating the Cu-Zn-Al composite hydroxide to 400° C. at a heating rate of 10° C. / min in air, and calcining at the temperature for 4 hours to convert the Cu-Zn-Al-O multi-metal oxide composite material with a stable structure; S7, mixing the Cu-Zn-Al-O multi-metal oxide composite material with a cerium nitrate solution, impregnating for 6 hours, and subsequently drying and calcining at 300° C. for 2 hours to obtain a composite material having a high oxygen vacancy density and Ce 3+ / Ce 4+ The final modified catalyst for conversion capability.

4. The method for preparing a highly efficient coal-based catalyst for synthesizing dimethyl carbonate according to claim 3, characterized in that: The concentration of the sodium gluconate solution is 10%, and the solid-liquid ratio of the expanded coal slurry to the sodium gluconate solution is 1:

5.

5. The method for preparing a highly efficient coal-based catalyst for synthesizing dimethyl carbonate according to claim 3, characterized in that: The catalytic carbonization inducer consists of ZnCl2 and urea in a molar ratio of 1:

1.

6. The method for preparing a highly efficient coal-based catalyst for synthesizing dimethyl carbonate according to claim 3, characterized in that: The metal molar ratio in the mixed solution of copper nitrate, zinc nitrate and aluminum nitrate is 1:0.5:0.

2.

7. The method for preparing a highly efficient coal-based catalyst for synthesizing dimethyl carbonate according to claim 3, characterized in that: The impregnation condition of the cerium nitrate solution is a Ce / Cu molar ratio of 0.1.

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