Copper-zinc-aluminum-alkylated graphite carbon combined catalyst as well as preparation method and application thereof

Abstract

The invention relates to the field of catalytic materials and discloses a copper-zinc-aluminum-alkylated graphite carbon combined catalyst as well as a preparation method and application thereof. The copper-zinc-aluminum-alkylated graphite carbon combined catalyst comprises a copper-zinc-aluminum catalyst and alkylated graphite carbon which are physically mixed, the alkylated graphite carbon is graphite carbon subjected to silane surface hydrophobic modification. The combined catalyst comprises a copper-zinc-aluminum catalyst and alkylated graphite carbon, and based on the hydrophobic property of the alkylated graphite carbon, in the reaction process of catalyzing CO2 hydrogenation to prepare methanol, the thermodynamic equilibrium limitation in the reaction of preparing methanol through carbon dioxide hydrogenation can be broken through by adjusting the equilibrium movement of element reaction, and the catalytic activity of the alkylated graphite carbon is improved. And meanwhile, agglomeration of metal particles can be effectively inhibited. Therefore, the combined catalyst of the present invention can exhibit efficient carbon dioxide conversion rate, excellent methanol selectivity and long-term stability.

Description

Technical Field

[0001] This invention relates to the field of catalytic materials, and in particular to a copper-zinc-aluminum-alkyl graphite-carbon composite catalyst, its preparation method, and its application. Background Technology

[0002] Carbon dioxide is an underdeveloped industrial raw material with broad application prospects. Through catalytic hydrogenation technology, it can be converted into methanol, possessing crucial strategic value. Methanol is not only a high-value-added chemical that can be used directly as fuel, solvent, and antifreeze, but it is also an important chemical intermediate used to produce various organic products such as formaldehyde, acetic acid, chloromethane, methylamine, and dimethyl sulfate. Therefore, driven by both environmental demands and market potential, numerous international companies and research institutions are actively investing in the development and construction of methanol-to-carbon dioxide hydrogenation projects.

[0003] However, current catalyst technology for the synthesis of methanol from carbon dioxide hydrogenation is still not mature enough, and existing processes are mostly modified from catalysts used for the hydrogenation of methanol from carbon monoxide. Research mainly focuses on the reaction mechanism, the selection of active components and supports, and the influence of different preparation methods and reaction conditions on catalyst performance. However, constrained by thermodynamic equilibrium, traditional copper-zinc-aluminum methanol catalysts suffer from problems such as low carbon dioxide conversion, poor methanol selectivity, and insufficient stability (for example, patent CN118988352A struggles to simultaneously achieve high CO2 conversion and methanol selectivity). Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a copper-zinc-aluminum-alkyl graphite carbon composite catalyst, its preparation method, and its applications. The composite catalyst comprises two components: a copper-zinc-aluminum catalyst and alkyl graphite carbon. Based on the hydrophobic properties of the alkyl graphite carbon, in the catalytic hydrogenation of CO2 to methanol reaction, it can not only break the thermodynamic equilibrium limitation in the CO2 hydrogenation to methanol reaction by regulating the equilibrium shift of the elementary reactions, but also effectively inhibit the agglomeration of metal particles. Therefore, the composite catalyst of this invention exhibits high CO2 conversion efficiency, excellent methanol selectivity, and long-term stability.

[0005] The specific technical solution of the present invention includes: In a first aspect, the present invention provides a copper-zinc-aluminum-alkyl graphite carbon composite catalyst, which comprises a physically mixed copper-zinc-aluminum catalyst and alkyl graphite carbon; wherein the alkyl graphite carbon is graphite carbon modified with silane surface hydrophobicity.

[0006] As described in the background section, the development of catalysts for the synthesis of methanol from CO2 hydrogenation is not yet mature. Traditional copper-zinc-aluminum catalysts have disadvantages such as low CO2 conversion rate, poor methanol selectivity, and catalyst instability. Traditional copper-zinc-aluminum catalysts are prone to deactivation during the reaction. Through research, this invention found that the main reason is that under the synergistic effect of high temperature and water vapor, the copper particles agglomerate, resulting in a decrease in catalyst activity.

[0007] Therefore, the combined catalyst provided by this invention comprises two components: a copper-zinc-aluminum catalyst and alkylated graphite carbon. The copper-zinc-aluminum catalyst serves as the basic catalyst for the CO2 hydrogenation to methanol synthesis; the alkylated graphite carbon is graphite carbon with a surface modified by silane hydrophobicity. On one hand, the addition of alkylated graphite carbon can effectively inhibit the agglomeration of copper particles, thereby improving the catalyst's stability. On the other hand, this invention regulates the diffusion rate of byproducts (water) during the reaction by adjusting the wettability of water on the graphite carbon surface, thereby altering the reaction equilibrium and breaking the thermodynamic equilibrium limitations in the CO2 hydrogenation to methanol reaction, resulting in a catalyst exhibiting superior CO2 conversion rate and methanol selectivity.

[0008] The reactions involved in the hydrogenation of carbon dioxide to methanol are as follows: Main reaction: CO2 + 3H2 → CH3OH + H2O; Main side reaction: Reverse water-gas shift reaction (RWGS); CO2 + H2 → CO + H2O. These side reactions consume raw materials and generate impurities (such as CO and methane), reducing methanol selectivity.

[0009] Preferably, the silane has a carbon number of C2-C6.

[0010] This invention reveals that to further improve catalytic performance, the carbon number of silanes needs to be specifically limited. The influence of the carbon number of silanes on the catalytic effect can be analyzed from two dimensions: physical effects involving steric hindrance and mass transfer resistance, and chemical effects involving electronic effects and stability. This invention ultimately found that within the aforementioned reasonable carbon number range, the effect is better. If the carbon number is too low, it easily leads to insufficient hydrophobicity, and the improvement in catalyst performance is not significant; conversely, if the carbon number is too high, a dense organic layer is easily formed on the graphite carbon surface, resulting in greater mass transfer resistance, and the mechanical strength of the catalyst will also decrease.

[0011] More preferably, the silane includes one or more of trimethylchlorosilane, dimethyldichlorosilane, methyltrichlorosilane, and phenyltrimethoxysilane.

[0012] Preferably, the mass ratio of the alkylated graphite carbon to the copper-zinc-aluminum catalyst is 0.1-3:1.

[0013] The invention strictly limits the mass ratio of alkylated graphite carbon to copper-zinc-aluminum catalysts to the range of 0.1-3:1. Its core theory lies in balancing the triple requirements of hydrophobic protection, active site density, and mass transfer kinetics. When the ratio is below 0.1:1, the amount of support is insufficient to form a continuous hydrophobic layer, resulting in partial exposure of CuZnAl particles, allowing water molecules to invade and causing catalyst particle sintering. Conversely, if the ratio exceeds 3:1 (e.g., 4:1), the excess support will dilute the active components below the critical point—reducing the effective loading rate of CuZnAl, decreasing the catalytic activity per unit mass, and restricting product diffusion.

[0014] Preferably, the copper, zinc, and aluminum contents in the copper-zinc-aluminum catalyst are 20-60 mol%, 10-50 mol%, and 10-50 mol%, respectively.

[0015] Preferably, the copper-zinc-aluminum catalyst has a particle size of 20-40 mesh; the alkyl graphite carbon has a particle size of 20-40 mesh.

[0016] Preferably, the physical mixing method includes: a) Alkyl graphite carbon is laid in the lower layer and copper-zinc-aluminum catalyst is laid in the upper layer to form a double bed.

[0017] In method a), the two components are layered, and the reactants (Co2, H2) first contact the upper copper-zinc-aluminum catalyst. The generated products (methanol, byproduct water) need to diffuse downwards to the lower alkyl graphite carbon. Therefore, the catalytic effect of this method is relatively limited: (1) The water diffusion efficiency is relatively low: the byproduct water accumulates in the copper-zinc-aluminum catalyst layer and is difficult to diffuse quickly to the lower alkyl graphite carbon (hydrophobic material), which leads to increased water wettability on the catalyst surface and inhibits the equilibrium shift of the main reaction (CO2 hydrogenation to methanol) (the thermodynamic equilibrium limitation cannot be effectively broken); (2) The synergistic effect is relatively weak: the layered structure makes it impossible for the alkyl graphite carbon to closely regulate the microenvironment on the surface of the copper-zinc-aluminum catalyst. Copper particles are more likely to agglomerate under the synergistic effect of high temperature and water vapor, and the stability decreases. Therefore, the CO2 conversion rate and methanol selectivity of this method are relatively the worst among the several methods.

[0018] b) Alkyl graphite carbon and copper-zinc-aluminum catalysts are alternately laid to form a multi-layer composite bed.

[0019] In method b), the two components are alternately laid to form a multilayer structure of “copper-zinc-aluminum-alkyl graphite-carbon-copper-zinc-aluminum-…”. The reactants and products alternately contact the two components between the layers, so the catalytic effect is improved compared with method a): (1) The water diffusion path is shortened: the by-product water can diffuse rapidly in the adjacent alkyl graphite-carbon layers, reducing the accumulation on the surface of the copper-zinc-aluminum catalyst, and the regulation effect on the reaction equilibrium is better than that of method a); (2) Local synergistic enhancement: each layer of copper-zinc-aluminum catalyst can form local synergy with the adjacent alkyl graphite-carbon, which inhibits the agglomeration of copper particles to a certain extent. However, it also has certain limitations: the multilayer structure still has mass transfer resistance (the interlayer interface may hinder diffusion), and the contact area between the two components is limited. The hydrophobic regulation and anti-agglomeration ability are still not as good as the uniform mixing method. Therefore, the effect is better than that of method a) but weaker than that of method c) and d).

[0020] c) The copper-zinc-aluminum catalyst is mixed with alkyl graphite carbon, extruded, crushed, sieved, and laid to form a single bed.

[0021] In method c), the two components are uniformly mixed and then extruded to form a tightly structured composite particle, which is then laid into a single bed layer. The catalytic effect is optimal: (1) Maximizes the contact area: Extrusion molding allows the copper-zinc-aluminum catalyst and alkyl graphite carbon to be tightly combined at the microscale. The hydrophobic groups of alkyl graphite carbon can directly regulate the water wettability of the copper-zinc-aluminum catalyst surface. By-product water diffuses rapidly through hydrophobic channels, effectively breaking the thermodynamic equilibrium limitation; (2) Strongest anti-agglomeration ability: The tight mixed structure allows alkyl graphite carbon to "wrap" or "anchor" copper particles, physically hindering the migration and agglomeration of copper particles induced by water vapor at high temperature, significantly improving the stability of the catalyst; (3) High mass transfer efficiency: The particle structure after molding is uniform, and the reactants (CO2, H2) can contact the two components at the same time. The reaction and product diffusion proceed simultaneously, reducing the local concentration gradient and further improving the CO2 conversion rate and methanol selectivity.

[0022] d) Alkyl graphite carbon is mixed with copper-zinc-aluminum catalyst and laid to form a single bed.

[0023] In method d), the two components are directly mixed (without extrusion molding) and laid out as a single bed. The components are evenly distributed but the interparticle bonding is relatively loose. Its catalytic effect is second only to method c) among the four methods: (1) Effective hydrophobic regulation: The uniform mixing allows the alkyl graphite carbon to adsorb water by-products in a timely manner, regulating the reaction balance. The effect is better than the layered methods a) and b). The limitation of method d is that: without extrusion molding, the bonding tightness of the two components is lower than that of method c). Some copper particles may be exposed to water vapor, and the risk of agglomeration is slightly higher than that of c). At the same time, the loose structure may lead to slightly lower local mass transfer efficiency (such as uneven diffusion paths of reactants).

[0024] Secondly, the present invention provides a method for preparing the above-mentioned copper-zinc-aluminum-alkyl graphite-carbon composite catalyst, which includes the following steps: 1) Preparation of copper-zinc-aluminum catalyst: Dissolve copper salt, zinc salt and aluminum salt in water to obtain solution A; simultaneously add solution A containing copper salt, zinc salt and aluminum salt and alkaline solution B to water, react under alkaline conditions, age the resulting precipitate, separate it, and calcine it to obtain copper-zinc-aluminum catalyst.

[0025] 2) Chemically modified graphite carbon: Pre-exfoliated graphite carbon (Gra) dispersion is mixed with silane and reacted to obtain alkylated graphite carbon.

[0026] This invention uses hydrophobic silanes to modify graphite carbon to exhibit hydrophobic properties. The reaction principle is that the graphite carbon surface has sufficient -OH / -COOH, which can react directly with silanes, thereby endowing the graphite carbon with appropriate hydrophobicity.

[0027] Preferably, the ratio of silane to graphite carbon is 0.2-6 mL / g.

[0028] This invention limits the ratio of graphite carbon to silane reagent to 0.2-6 mL / g, which essentially achieves dual regulation of monolayer dense modification and side reaction suppression through stoichiometric equilibrium. When the ratio is below 0.2 mL / g (e.g., 0.1 mL / g), the amount of silane is insufficient to cover the active sites on the graphite carbon surface, failing to form an effective hydrophobic barrier; more seriously, unreacted hydroxyl groups become metal agglomeration sites in the subsequent CuZnAl mixing, increasing the particle size of the active component and reducing catalyst activity. Conversely, if the ratio exceeds 6 mL / g (e.g., 8 mL / g), excess silane hydrolyzes and condenses in the solvent to form polysiloxane particles, which block the mesopores of the support, reducing pore volume and increasing mass transfer resistance. 3) Alkyl graphite carbon is physically mixed with copper-zinc-aluminum catalysts to obtain copper-zinc-aluminum-alkyl graphite carbon composite catalysts.

[0029] Preferably, in step 1), the dropping rate of solution A is 2-4 mL / min.

[0030] Preferably, in step 1), the pH value of the alkaline condition is 8.5-9.5.

[0031] Preferably, in step 1), the reaction temperature is 30-120°C.

[0032] Preferably, in step 1), the calcination is carried out in a muffle furnace with air introduced, at a temperature of 300-400°C and a time of 2-6 hours.

[0033] Preferably, in step 2), the pre-stripping treatment includes: dispersing graphite carbon in water, ultrasonically treating it to ensure full dispersion, filtering it after the process, and drying it; mixing anhydrous toluene or tetrahydrofuran with the obtained graphite carbon and ultrasonically dispersing it.

[0034] Preferably, in step 2), the reaction conditions are: inert atmosphere, temperature 50-80℃, and time 6-12h.

[0035] Thirdly, the present invention provides the application of the above-mentioned copper-zinc-aluminum-alkyl graphite carbon composite catalyst in the catalytic hydrogenation of CO2 to methanol.

[0036] Preferably, the application includes the following steps: loading a copper-zinc-aluminum-alkyl graphite carbon composite catalyst into a high-pressure fixed-bed reactor, reducing the catalyst before the reaction, and then reacting the catalyst at 200-300°C, a pressure of 1-9 MPa, and a space velocity of 500-50000 mL / (g). cat Under the conditions of .h), a reaction gas is introduced to hydrogenate methanol; the molar ratio of H2 / CO2 in the reaction gas is 1-10:1, and CO with a volume percentage content of 0-10% is added.

[0037] The role of CO doping in the reaction gas is to enhance the activity, selectivity, and stability of the copper-zinc-alkyl graphite-carbon composite catalyst through a synergistic effect of "regulating active sites, suppressing side reactions, optimizing kinetics, and balancing thermal effects," especially under conditions where side reactions are prone to occur, such as high temperature and low H2 / CO2 ratio. However, the CO doping amount should be controlled below 10% (excessive doping will compete for active sites and inhibit the main reaction).

[0038] Preferably, the reduction catalyst uses hydrogen / nitrogen as the reducing atmosphere, with a hydrogen / nitrogen space velocity of 2500-3500 mL / (gcat.h), a hydrogen content of 5-15 vol%, a reduction temperature of 200-300℃, and a time of 2-10 h.

[0039] Compared with the prior art, the beneficial effects of the present invention are: (1) The combined catalyst provided by this invention comprises two components: a copper-zinc-aluminum catalyst and an alkylated graphite carbon. The copper-zinc-aluminum catalyst serves as the basic catalyst for the synthesis of methanol from CO2 hydrogenation. The alkylated graphite carbon is graphite carbon with a surface modified by hydrophobic silane. On the one hand, the addition of alkylated graphite carbon can effectively inhibit the agglomeration of copper particles, thereby improving the stability of the catalyst. On the other hand, by adjusting the wettability of water on the graphite carbon surface, the diffusion rate of byproducts (water) during the reaction is controlled, thereby changing the reaction equilibrium, breaking the thermodynamic equilibrium limitation in the reaction of carbon dioxide hydrogenation to methanol, and enabling the catalyst to exhibit better carbon dioxide conversion rate and methanol selectivity.

[0040] (2) By limiting the carbon number range of silanes, the present invention can further improve the catalytic effect of the combined catalyst.

[0041] (3) The present invention can further improve the catalytic effect by adjusting the physical mixing method of the two components in the combined catalyst.

[0042] (4) By optimizing the process conditions for producing methanol by carbon dioxide hydrogenation, the present invention can further improve the carbon dioxide conversion rate and methanol selectivity. Attached Figure Description

[0043] Figure 1 This is a schematic diagram of four physical mixing methods for the copper-zinc-aluminum-alkyl graphite carbon composite catalyst in this invention. Detailed Implementation

[0044] The present invention will be further described below with reference to embodiments.

[0045] General Implementation Examples In a first aspect, a copper-zinc-aluminum-alkyl graphite carbon composite catalyst comprises a physically mixed copper-zinc-aluminum catalyst and alkyl graphite carbon; wherein the alkyl graphite carbon is graphite carbon modified with silane surface.

[0046] In some preferred embodiments, the silane has a carbon number of C2-C6.

[0047] In some more preferred embodiments, the silane includes one or more of trimethylchlorosilane, dimethyldichlorosilane, methyltrichlorosilane, and phenyltrimethoxysilane.

[0048] In some preferred embodiments, the mass ratio of the alkylated graphite carbon to the copper-zinc-aluminum catalyst is 0.1-3:1.

[0049] In some preferred embodiments, the copper, zinc, and aluminum contents in the copper-zinc-aluminum catalyst are 20-60 mol%, 10-50 mol%, and 10-50 mol%, respectively.

[0050] In some preferred embodiments, the copper-zinc-aluminum catalyst has a particle size of 20-40 mesh; the alkyl graphite carbon has a particle size of 20-40 mesh.

[0051] In some preferred embodiments, the physical mixing method includes: a) An alkyl graphite carbon layer is laid in the lower layer, and a copper-zinc-aluminum catalyst layer is laid in the upper layer to form a dual-bed system; or b) Alkyl graphite carbon and copper-zinc-aluminum catalysts are alternately laid to form a multi-layer composite bed; or c) Mix copper-zinc-aluminum catalyst with alkylated graphite carbon, extrude it, crush it, sieve it, and lay it in a single bed; or d) Alkyl graphite carbon is mixed with copper-zinc-aluminum catalyst and laid to form a single bed.

[0052] Secondly, a method for preparing the above-mentioned copper-zinc-aluminum-alkyl graphite carbon composite catalyst includes the following steps: 1) Preparation of copper-zinc-aluminum catalyst: dissolving copper salt, zinc salt and aluminum salt in water to obtain solution A; simultaneously adding solution A containing copper salt, zinc salt and aluminum salt and alkaline solution B to water, reacting under alkaline conditions, aging the precipitate obtained from the reaction, separating it, and calcining it to obtain copper-zinc-aluminum catalyst.

[0053] In some preferred embodiments, in step 1), the copper salt, zinc salt, and aluminum salt are one or more of the nitrate, sulfate, and chloride salts corresponding to copper, zinc, and aluminum elements, respectively.

[0054] In some preferred embodiments, in step 1), the alkaline solution B is an aqueous sodium carbonate solution.

[0055] In some preferred embodiments, in step 1), the dropping rate of solution A is 2-4 mL / min.

[0056] In some preferred embodiments, in step 1), the pH value of the alkaline conditions is 8.5-9.5.

[0057] In some preferred embodiments, in step 1), the temperature of the reaction is 30-120°C.

[0058] In some preferred embodiments, in step 1), the precipitation aging time is 2-100 hours.

[0059] In some preferred embodiments, in step 1), the calcination is carried out in a muffle furnace with air introduced, at a temperature of 300-400°C and a time of 2-6 hours.

[0060] 2) Chemically modified graphite carbon: The pre-exfoliated graphite carbon dispersion is mixed with silane to obtain alkylated graphite carbon; the ratio of silane to graphite carbon is 0.2-6 mL / g.

[0061] In some preferred embodiments, step 2) of the pre-stripping treatment includes: dispersing graphite carbon (Gra) in water, ultrasonically treating it to ensure full dispersion, filtering it after the process, and drying it; mixing anhydrous toluene or tetrahydrofuran with the obtained graphite carbon and ultrasonically dispersing it.

[0062] In some preferred embodiments, in step 2), the reaction conditions are: inert atmosphere, temperature 50-80℃, and time 6-12h.

[0063] In some preferred embodiments, in step 2), the reaction is cooled to room temperature, centrifuged, washed alternately with anhydrous ethanol and toluene, and dried under vacuum.

[0064] 3) The alkyl graphite carbon was physically mixed with the copper-zinc-aluminum catalyst to obtain the copper-zinc-aluminum-alkyl graphite carbon composite catalyst.

[0065] Thirdly, the present invention provides the application of the above-mentioned copper-zinc-aluminum-alkyl graphite carbon composite catalyst in the catalytic hydrogenation of CO2 to methanol.

[0066] In some preferred embodiments, the application includes the following steps: loading a copper-zinc-aluminum-alkyl graphite-carbon composite catalyst into a high-pressure fixed-bed reactor, reducing the catalyst before the reaction, and then introducing a reaction gas to hydrogenate methanol under conditions of 200-300°C, pressure 1-9 MPa, and space velocity 500-50000 mL / (gcat.h); the molar ratio of H2 / Co2 in the reaction gas is 1-10:1, and CO is incorporated at a volume percentage of 0-10%.

[0067] In some preferred embodiments, the reduction catalyst uses hydrogen / nitrogen as the reducing atmosphere, with a hydrogen / nitrogen space velocity of 2500-3500 mL / (gcat.h), a hydrogen content of 5-15 vol%, a reduction temperature of 200-300℃, and a time of 2-10 h.

[0068] Specific Examples and Comparative Examples (I): Comparison of Alkyl Graphite Carbons with Different Carbon Numbers of Silanes Example 1: Copper-Zinc-Aluminum + Gra-0.5Si(CH3)2 catalyst First, a CuZnAl catalyst was synthesized via co-precipitation: 12.05 g (0.050 mol) copper nitrate trihydrate, 10.40 g (0.035 mol) zinc nitrate hexahydrate, and 5.63 g (0.015 mol) aluminum nitrate nonahydrate were dissolved in 200 mL of deionized water to obtain solution A. 15.90 g (0.15 mol) sodium carbonate was dissolved in 200 mL of deionized water to obtain solution B. Solutions A and B were simultaneously added dropwise to a beaker containing 200 mL of deionized water, while maintaining heating at 30 °C and stirring at 700 rpm. The dropwise flow rate of solution A was controlled at 3 mL / min, and the pH of the liquid in the beaker was maintained at 9.5 by adjusting the dropwise flow rate of solution B. After aging the resulting precipitate for 100 h, it was washed with deionized water, filtered six times, and dried at 100 °C for 2 h. After drying, the sample was placed in a muffle furnace and calcined at 350°C with air for 4 hours to obtain the copper-zinc-aluminum catalyst CuZnAl. The molar percentages of copper, zinc, and aluminum in this catalyst were 50%, 35%, and 15%, respectively. Synthetic methylated graphite carbon material Gra-0.5Si(CH3)2: 10g of commercial graphite carbon material (brand: Cabot Corporation, product name: ...) XC-72R was dispersed in deionized water and sonicated for 30 minutes to ensure full dispersion. After the dispersion was complete, the material was filtered and dried for later use. 10 g of anhydrous toluene and 1 g of dried graphite carbon material were added to a dry reaction flask and sonicated for 15 minutes. 0.5 mL of dimethylchlorosilane (methyltrichlorosilane (CH3) and hexadecyltrimethoxysilane (C16) were added as comparative examples of different carbon chain lengths) was slowly added dropwise. The mixture was heated to 80 °C under nitrogen protection and stirred for 6 h. After the reaction was completed, the mixture was cooled to room temperature and the solid product was obtained by centrifugation. The solid product was washed three times alternately with anhydrous ethanol and toluene and then dried in a vacuum drying oven at 60 °C for 12 h.

[0069] The carbon dioxide hydrogenation reaction was tested in a fixed-bed reactor. The test procedures for the catalytic reaction performance are as follows: (1) Mix 0.5g of copper-zinc-aluminum catalyst (30 mesh) and 0.5g of Gra-0.5Si(CH3)2 (30 mesh) catalyst according to... Figure 1 Method (c) involves physical mixing, filling the mixture into a stainless steel reaction tube, and plugging both ends with quartz wool to maintain the bed height, thus assembling a fixed-bed reactor. Method (c) specifically involves mixing copper-zinc-aluminum catalysts with alkylated graphite carbon, extruding and molding the mixture, crushing it, passing it through a 30-mesh sieve, and laying it to form a single bed. As a comparison, 0.5g of copper-zinc-aluminum catalyst and 0.5g of inert quartz sand were packed into a stainless steel reaction tube, and both ends were plugged with quartz wool to maintain the bed height, thus assembling a fixed-bed reactor.

[0070] (2) Using a space velocity of 3000 mL / (g) cat The catalyst was reduced by 10 vol% hydrogen / nitrogen at 240 °C for 6 h.

[0071] (3) A reaction gas with a hydrogen / carbon dioxide / argon (H2 / Co2 / Ar) ratio of 72 / 24 / 4 was introduced into a high-pressure fixed-bed reactor. The catalyst bed temperature was controlled at 240℃, the reaction pressure at 3.0 MPa, and the volumetric space velocity of the feed gas at 6000 mL / (g) cat .h), TOS = 40h. The experimental results are as follows: The data comparison in the table above shows that Gra-0.5Si(CH3)2, through hydrophobic microenvironment regulation (accelerating water diffusion) and synergistic action of active centers (inhibiting RWGS side reactions), simultaneously improves Co2 conversion and methanol selectivity, verifying the advantages of the "copper-zinc-aluminum + alkyl graphite carbon" composite system in the carbon dioxide hydrogenation to methanol reaction, and providing experimental basis for optimizing catalyst structure. Gra-0.5Si(CH3) suffers from insufficient hydrophobicity due to its low carbon number, resulting in insignificant catalyst performance improvement; while Gra-0.5Si(C16), with its excessive carbon number, easily forms a dense organic layer on the graphite carbon surface, leading to greater mass transfer resistance and a decrease in catalyst mechanical strength.

[0072] Example 2: Copper-Zinc-Aluminum + Gra-2Si(CH3)2 catalyst First, the CuZnAl catalyst was synthesized via co-precipitation: 4.82 g (0.02 mol) copper nitrate trihydrate, 14.86 g (0.05 mol) zinc nitrate hexahydrate, and 11.26 g (0.03 mol) aluminum nitrate nonahydrate were dissolved in 200 mL of deionized water to obtain solution A. 15.90 g (0.15 mol) sodium carbonate was dissolved in 200 mL of deionized water to obtain solution B. Solutions A and B were simultaneously added dropwise to a beaker containing 200 mL of deionized water, while maintaining heating at 120 °C and stirring at 700 rpm. The dropwise flow rate of solution A was controlled at 3 mL / min, and the pH of the liquid in the beaker was maintained at 8.5 by adjusting the dropwise flow rate of solution B. After aging the resulting precipitate for 2 h, it was washed with deionized water, filtered six times, and dried at 100 °C for 12 h. After drying, it was placed in a muffle furnace and calcined at 350 °C with air for 4 h to obtain the copper-zinc-aluminum catalyst CuZnAl. In this catalyst, the molar percentages of copper, zinc, and aluminum are 20%, 50%, and 30%, respectively. Synthesis of methylated graphene carbon material Gra-2Si(CH3)2: 10g of anhydrous toluene and 1g of dried commercial graphene carbon material (brand: Cabot Corporation, product grade: ...) XC-72R) was added to a dry reaction flask and ultrasonically dispersed for 15 minutes; 2.0 mL of dimethyldichlorosilane was slowly added dropwise, and the mixture was heated to 50 °C under nitrogen protection and stirred for 12 h. After the reaction was completed, the mixture was cooled to room temperature and centrifuged to obtain a solid product. The product was washed three times alternately with anhydrous ethanol and toluene and then dried in a vacuum drying oven at 60 °C for 12 h.

[0073] The carbon dioxide hydrogenation reaction was tested in a fixed-bed reactor. The test procedures for the catalytic reaction performance are as follows: (1) Mix 0.5g of copper-zinc-aluminum catalyst (30 mesh) and 0.5g of Gra-2Si(CH3)2 (30 mesh) catalyst according to... Figure 1The catalyst was physically mixed using method (c) (same as in Example 1) and packed into a stainless steel reaction tube. Both ends were plugged with quartz wool to maintain the bed height, thus assembling a fixed-bed reactor. The reduction and reaction conditions of the catalyst were the same as in Example 1, and the reaction results are as follows: The data in the table above show that, compared to CuZnAl alone, the introduction of Gra-2Si(CH3)2 doubled the CO2 conversion rate and significantly improved methanol selectivity. The increased hydrophobicity resulting from a larger amount of dimethylsilane modification (i.e., Gra-2Si(CH3)2 compared to Gra-0.5Si(CH3)2 in Example 1) is key to further performance optimization, verifying the positive correlation between the degree of modification of alkyl graphite carbon and catalytic performance, and providing a basis for the design of high-efficiency catalysts. Example 3: Copper-Zinc-Aluminum + Gra-6Si(CH3) Catalyst First, a CuZnAl catalyst was synthesized via co-precipitation: 14.46 g (0.06 mol) copper nitrate trihydrate, 2.97 g (0.01 mol) zinc nitrate hexahydrate, and 11.26 g (0.03 mol) aluminum nitrate nonahydrate were dissolved in 200 mL of deionized water to obtain solution A. 15.90 g (0.15 mol) sodium carbonate was dissolved in 200 mL of deionized water to obtain solution B. Solutions A and B were simultaneously added dropwise to a beaker containing 200 mL of deionized water, while maintaining heating at 60 °C and stirring at 700 rpm. The dropwise flow rate of solution A was controlled at 3 mL / min, and the pH of the liquid in the beaker was maintained at 9 by adjusting the dropwise flow rate of solution B. After aging the resulting precipitate for 24 h, it was washed with deionized water, filtered six times, and dried at 100 °C for 12 h. After drying, it was placed in a muffle furnace and calcined at 350 °C with air for 4 h to obtain the copper-zinc-aluminum catalyst CuZnAl. In this catalyst, the molar percentages of copper, zinc, and aluminum are 60%, 10%, and 30%, respectively. Synthetic methylated graphene carbon material Gra-6Si(CH3): 10g anhydrous toluene and 1g dried commercial graphene carbon material (brand: Cabot Corporation, product grade: ...) XC-72R) was added to a dry reaction flask and ultrasonically dispersed for 15 minutes; 6.0 mL of methyltrichlorosilane was slowly added dropwise, and the mixture was heated to 70 °C under nitrogen protection and stirred for 8 hours. After the reaction was completed, the mixture was cooled to room temperature and centrifuged to obtain a solid product. The product was washed 5 times alternately with anhydrous ethanol and toluene and then dried in a vacuum drying oven at 60 °C for 12 hours.

[0074] The carbon dioxide hydrogenation reaction was tested in a fixed-bed reactor. The test procedures for the catalytic reaction performance are as follows: (1) Mix 0.5g of copper-zinc-aluminum catalyst (30 mesh) and 0.5g of Gra-6Si(CH3) (30 mesh) catalyst according to... Figure 1 The catalyst was physically mixed using method (c) (same as in Example 1) and packed into a stainless steel reaction tube. Both ends were plugged with quartz wool to maintain the bed height, thus assembling a fixed-bed reactor. The reduction and reaction conditions of the catalyst were the same as in Example 1, and the reaction results are as follows: The data in the table above shows that the matching between the proportion of active metal components in the catalyst and the type of silane is the key to the synergistic effect. Simply increasing the Cu content or the amount of silane may not necessarily enhance the catalytic performance. It is necessary to optimize the component ratio and modification process to achieve efficient synergy.

[0075] (II) Copper-Zinc-Aluminum + Gra-2Si(CH3)2 catalysts with different proportions Example 4 The CuZnAl and Gra-2Si(CH3)2 catalysts were tested in the same way as in Example 2, with the carbon dioxide hydrogenation reaction performed in a fixed-bed reactor. The test steps for the catalytic reaction performance were as follows: (1) 0.5g of copper-zinc-aluminum catalyst (30 mesh) and 0.1g / 0.25g / 0.5g / 1.0g / 1.5g of Gra-2Si(CH3)2 (30 mesh) catalyst were mixed according to the following steps: Figure 1 The catalyst was physically mixed using method (c) (same as in Example 1) and packed into a stainless steel reaction tube. Both ends were plugged with quartz wool to maintain the bed height, thus assembling a fixed-bed reactor. The reduction and reaction conditions of the catalyst were the same as in Example 1, and the reaction results are as follows: The data comparison in the table above shows that the addition of Gra-2Si(CH3)2 significantly improves the CO2 hydrogenation performance of the CuZnAl catalyst through a synergistic effect of "hydrophobic regulation and side reaction suppression"; however, excessive addition will lead to diminishing marginal benefits due to dilution of the active component. Considering both performance and cost, a mass ratio of Gra-2Si(CH3)2 to CuZnAl of 1:1 to 2:1 is the preferred range, which can achieve high conversion rate and high methanol selectivity at a lower cost.

[0076] (III) The Influence of Different Physical Mixing Methods Example 5 The CuZnAl and Gra-2Si(CH3)2 reactions were tested in the same manner as in Example 2, with the carbon dioxide hydrogenation reaction performed in a fixed-bed reactor. The test steps for the catalytic reaction performance are as follows: 0.5g of copper-zinc-aluminum catalyst and 0.5g of Gra-2Si(CH3)2 catalyst were mixed. Figure 1Four physical mixing methods were used (ad) to physically mix the catalysts separately and fill them into stainless steel reaction tubes. Both ends were plugged with quartz wool to maintain the bed height, resulting in a fixed-bed reactor. Physical mixing method (a) involved laying alkyl graphite carbon in the lower layer and copper-zinc-aluminum catalyst in the upper layer, forming a double-bed layer. Physical mixing method (b) involved alternating layers of alkyl graphite carbon and copper-zinc-aluminum catalyst, forming a multi-layer composite bed. Physical mixing method (c) was the same as in Example 1. Physical mixing method (d) involved mixing alkyl graphite carbon and copper-zinc-aluminum catalyst and laying them to form a single-bed layer.

[0077] The reduction and reaction conditions for the catalyst were the same as in Example 1, and the reaction results are as follows: The data comparison in the table above shows that different mixing methods directly affect the catalytic effect by changing the contact area of ​​components, the water diffusion path, and the microenvironment of the active center. Method (c), an extruded single-bed catalyst, exhibits the best performance due to its "largest contact area, lowest mass transfer resistance, and most direct hydrophobic control." Method (d), a simple mixed single-bed catalyst, is second best, although its uniformity still ensures a certain degree of synergistic effect. Methods (b) and (a) have poorer performance due to insufficient interlayer mass transfer resistance and hydrophobic control. This result verifies that "closely bound components + uniform distribution" are key to maximizing the synergistic effect of CuZnAl and Gra-2Si(CH3)2, providing experimental basis for catalyst bed design.

[0078] (iv) Effect of different reaction temperatures Example 6 The CuZnAl and Gra-2Si(CH3)2 reactions were tested in the same manner as in Example 2, with the carbon dioxide hydrogenation reaction performed in a fixed-bed reactor. The test steps for the catalytic reaction performance are as follows: (1) Mix 0.5g of copper-zinc-aluminum catalyst (30 mesh) and 0.5g of Gra-2Si(CH3)2 (30 mesh) catalyst according to... Figure 1 The catalyst was physically mixed using method (c) (same as in Example 1) and packed into a stainless steel reaction tube. Both ends were plugged with quartz wool to maintain the bed height, resulting in a fixed-bed reactor. The catalyst reduction conditions were the same as in Example 1, with a reaction gas ratio of hydrogen / carbon dioxide / argon (H2 / CO2 / Ar) of 72 / 24 / 4. The catalyst bed temperature was controlled at 200, 220, 240, 260, 280, and 300°C, the reaction pressure at 3.0 MPa, the feed gas volume hourly space velocity (VHSV) at 6000 mL / (gcat.h), and the total oxygen storage (TOS) at 40 h. The experimental results are as follows: The data comparison in the table above shows that the reaction temperature affects catalytic performance through a triple mechanism of "thermodynamic equilibrium regulation + kinetic rate driving + side reaction competition": low temperature (200℃) is beneficial to methanol selectivity but the conversion rate is too low; high temperature (>240℃) increases the conversion rate but the side reaction dominates, causing a sharp drop in methanol selectivity; 220-240℃ is the preferred range, at which a high methanol selectivity can be maintained on the basis of a high conversion rate, maximizing the yield of the target product, and the synergistic effect with CuZnAl+Gra-2Si(CH3)2 catalyst is best matched.

[0079] (V) Effects of different reaction pressures Example 7 The CuZnAl and Gra-2Si(CH3)2 reactions were tested in the same manner as in Example 2, with the carbon dioxide hydrogenation reaction performed in a fixed-bed reactor. The test steps for the catalytic reaction performance are as follows: (1) Mix 0.5g of copper-zinc-aluminum catalyst (30 mesh) and 0.5g of Gra-2Si(CH3)2 (30 mesh) catalyst according to... Figure 1 The catalyst was physically mixed using method (c) (same as in Example 1) and packed into a stainless steel reaction tube. Both ends were plugged with quartz wool to maintain the bed height, resulting in a fixed-bed reactor. The catalyst reduction conditions were the same as in Example 1, with a reaction gas ratio of hydrogen / carbon dioxide / argon (H2 / CO2 / Ar) of 72 / 24 / 4. The catalyst bed temperature was controlled at 240°C, and the reaction pressures were 1, 2, 3, 5, 7, and 9 MPa. The feed gas volume hourly space velocity (VHSV) ranged from 6000 mL / (gcat.h), and the TOS was 40 h. The experimental results are as follows: The data comparison in the table above shows that reaction pressure affects catalytic performance through "thermodynamic equilibrium regulation + reactant adsorption competition": at low pressure (<3MPa), the main reaction advantage is weak, and the conversion rate and methanol selectivity are low; at high pressure (>5MPa), the performance improvement is limited but the cost increases dramatically, and the preferred pressure is 3.0-5.0MPa; when using CuZnAl / alkyl graphite carbon catalyst, a pressure below 3.0MPa will lead to a decrease in methanol space-time yield of >40%, and a pressure above 5.0MPa will increase energy consumption per unit yield by >35%.

[0080] (vi) Effect of different reaction flow rates Example 8 The CuZnAl and Gra-2Si(CH3)2 reactions were tested in the same manner as in Example 2, with the carbon dioxide hydrogenation reaction performed in a fixed-bed reactor. The test steps for the catalytic reaction performance are as follows: (1) Mix 0.5g of copper-zinc-aluminum catalyst (30 mesh) and 0.5g of Gra-2Si(CH3)2 (30 mesh) catalyst according to... Figure 1The catalyst was physically mixed using method (c) (same as in Example 1) and packed into a stainless steel reaction tube. Both ends were plugged with quartz wool to maintain the bed height, resulting in a fixed-bed reactor. The catalyst reduction conditions were the same as in Example 1, with a reaction gas ratio of hydrogen / carbon dioxide / argon (H2 / CO2 / Ar) of 72 / 24 / 4. The catalyst bed temperature was controlled at 240°C, the reaction pressure at 3 MPa, and the feed gas volume hourly space velocity (VHSV) ranged from 500, 1000, 3000, 6000, 10000, to 50000 mL / (gcat.h), with a TOS of 40 h. The experimental results are as follows: The data comparison in the table above shows that space velocity affects the competition between the main and side reactions by adjusting the "contact time": Medium space velocity (6000 mL / (g)) cat At a space velocity of 3000-10000 mL / (g), the main reaction kinetics are significantly superior, side reactions are suppressed, and overall performance is optimal; excessively low or high space velocities lead to decreased performance due to increased side reaction proportions or insufficient conversion efficiency. Therefore, 3000-10000 mL / (g) cat The preferred range is 6000 mL / (g) (·h). cat (h) is the optimal point, balancing catalytic performance and industrial feasibility. (VII) The influence of different H2 / CO2 ratios. Example 9 The CuZnAl and Gra-2Si(CH3)2 reactions were tested in the same manner as in Example 2, with the carbon dioxide hydrogenation reaction performed in a fixed-bed reactor. The test steps for the catalytic reaction performance are as follows: (1) Mix 0.5g of copper-zinc-aluminum catalyst (30 mesh) and 0.5g of Gra-2Si(CH3)2 (30 mesh) catalyst according to... Figure 1 The catalyst was physically mixed using method (c) (same as in Example 1) and packed into a stainless steel reaction tube. Both ends were plugged with quartz wool to maintain the bed height, resulting in a fixed-bed reactor. The catalyst reduction conditions were the same as in Example 1, with the following reaction conditions: a certain proportion of hydrogen / carbon dioxide / argon (H2 / CO2 / Ar) reaction gas was introduced, making H2 / CO2 = 1, 2, 3, 5, 10; the catalyst bed temperature was controlled at 240℃; the reaction pressure was 3 MPa; the feed gas volume hourly space velocity was 6000 mL / (gcat.h); and TOS = 40 h. The experimental results are as follows: The data comparison in the table above shows that the H2 / CO2 ratio affects catalytic performance by regulating the "match between feedstock supply and reaction stoichiometry": when the ratio is too low (<3), insufficient H2 leads to low CO2 conversion and more byproducts; when the ratio is too high (>5), H2 is wasted and performance improvement is limited. A ratio of 3-5 is the preferred range, which balances high conversion rate, high methanol selectivity, and feedstock economy, representing the optimal choice for balancing the main reaction and process costs.

[0081] (viii) The Influence of Different CO Contents Example 10 The CuZnAl and Gra-2Si(CH3)2 reactions were tested in the same manner as in Example 2, with the carbon dioxide hydrogenation reaction performed in a fixed-bed reactor. The test steps for the catalytic reaction performance are as follows: (1) Mix 0.5g of copper-zinc-aluminum catalyst (30 mesh) and 0.5g of Gra-2Si(CH3)2 (30 mesh) catalyst according to... Figure 1 The catalyst was physically mixed using method (c) and packed into a stainless steel reaction tube. Both ends were plugged with quartz wool to maintain the bed height, resulting in a fixed-bed reactor. The catalyst reduction conditions were the same as in Example 1, with the following reaction conditions: a certain proportion of hydrogen / carbon dioxide / argon (H2 / CO2 / Ar) reaction gas was introduced to make H2 / CO2 = 3, and CO was added at volume percentages of 0, 1, 2, 3, 5, and 10%. The catalyst bed temperature was controlled at 240°C, the reaction pressure at 3 MPa, the feed gas volume hourly space velocity (VHSV) ranged from 6000 mL / (gcat.h), and TOS = 40 h. The experimental results are as follows: The data comparison in the table above shows that the addition of CO affects catalytic performance through a dual effect of "competitive adsorption and side reaction inhibition": at low concentrations (2-3 vol%), it mainly inhibits RWGS, significantly improving methanol selectivity, and its impact on CO2 conversion is controllable; at high concentrations (>5%), competitive adsorption dominates, CO2 conversion rate plummets, and it loses its practical application value. Therefore, 2-3 vol% is the preferred CO content range, which can improve methanol purity while maintaining high overall production efficiency.

[0082] (ix) Life test Example 11 The CuZnAl and Gra-2Si(CH3)2 reactions were tested in the same manner as in Example 2, with the carbon dioxide hydrogenation reaction performed in a fixed-bed reactor. The test steps for the catalytic reaction performance are as follows: Mix 0.5g of copper-zinc-aluminum catalyst (30 mesh) and 0.5g of Gra-2Si(CH3)2 (30 mesh) catalyst according to... Figure 1The catalyst was physically mixed using method (c) (same as in Example 1) and packed into a stainless steel reaction tube. Both ends were plugged with quartz wool to maintain the bed height, thus assembling a fixed-bed reactor. The reduction and reaction conditions of the catalyst were the same as in Example 1, and the reaction results are as follows: The data comparison in the table above shows that CuZnAl and Gra-2Si(CH3)2, when mixed in method (c), exhibit excellent long-term operational stability: (1) Stability of active centers: The anchoring effect of Gra-2Si(CH3)2 effectively inhibits Cu particle aggregation, avoids the reduction of active sites, and ensures long-term stability of conversion rate; (2) Stability of microenvironment: The hydrophobic groups of alkyl graphite carbon are not destroyed by water or reaction products, the water diffusion efficiency remains stable, the enhancement of RWGS side reaction is inhibited, and the long-term selectivity of CO and methanol fluctuates very little. This result verifies the industrial application potential of this composite catalyst system in the reaction of carbon dioxide hydrogenation to methanol. It not only has excellent initial performance, but also maintains high efficiency and stable catalytic activity during long-term operation, providing key experimental evidence for large-scale production.

[0083] Comparative Example 1 The synthesis steps of the copper-zinc-aluminum catalyst are the same as in Example 1. The carbon dioxide hydrogenation reaction was tested in a fixed-bed reactor, and the test steps for the catalytic reaction performance are as follows: 0.5g of copper-zinc-aluminum catalyst (30 mesh) was packed into a stainless steel reaction tube, and both ends were plugged with quartz wool to maintain the bed height, thus assembling a fixed-bed reactor. The reduction and reaction conditions of the catalyst were the same as in Example 1, and the reaction results are as follows: The data comparison in the table above shows that the core reason for the performance degradation of the pure CuZnAl catalyst is the lack of hydrophobic regulation and active center protection by Gra-2Si(CH3)2, which is the key to the rapid deterioration of the pure CuZnAl catalyst performance: (1) Water inhibition effect: water byproduct cannot diffuse, forming a water film that hinders the reaction; (2) Cu particle agglomeration: water accelerates the migration and sintering of Cu particles, resulting in the loss of active sites; (3) Imbalance between main and side reactions: the proportion of RWGS side reaction continues to increase, and the methanol selectivity drops sharply. Compared with the long-term stability of the CuZnAl+Gra-2Si(CH3)2 combined catalyst in Comparative Example 11 (the conversion rate is stable at around 23% after 2000h), the pure CuZnAl catalyst experienced severe degradation within 200h, which verifies the irreplaceable role of alkyl graphite carbon in improving catalyst stability.

[0084] Unless otherwise specified, the raw materials and equipment used in this invention are all commonly used in the field; unless otherwise specified, the methods used in this invention are all conventional methods in the field.

[0085] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, alterations, and equivalent transformations made to the above embodiments based on the technical essence of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A copper-zinc-aluminum-alkyl graphite-carbon composite catalyst, characterized in that: Including physically mixed copper-zinc-aluminum catalysts and alkyl graphite carbon; The alkyl graphite carbon is graphite carbon with a hydrophobic surface modified by silane.

2. The copper-zinc-aluminum-alkyl graphite-carbon composite catalyst according to claim 1, characterized in that: The silane has a carbon number of C2-C6.

3. The copper-zinc-aluminum-alkyl graphite-carbon composite catalyst according to claim 2, characterized in that: The silane includes one or more of trimethylchlorosilane, dimethyldichlorosilane, methyltrichlorosilane, and phenyltrimethoxysilane.

4. The copper-zinc-aluminum-alkyl graphite-carbon composite catalyst according to any one of claims 1-3, characterized in that: The mass ratio of the alkylated graphite carbon to the copper-zinc-aluminum catalyst is 0.1-3:1; and / or The copper-zinc-aluminum catalyst contains 20-60 mol% copper, 10-50 mol% zinc, and 10-50 mol% aluminum, respectively; and / or The copper-zinc-aluminum catalyst has a particle size of 20-40 mesh; the alkyl graphite carbon has a particle size of 20-40 mesh.

5. The copper-zinc-aluminum-alkyl graphite-carbon composite catalyst according to any one of claims 1-3, characterized in that: The physical mixing methods include: a) An alkyl graphite carbon layer is laid in the lower layer, and a copper-zinc-aluminum catalyst layer is laid in the upper layer to form a dual-bed system; or b) Alkyl graphite carbon and copper-zinc-aluminum catalysts are alternately laid to form a multi-layer composite bed; or c) Mix copper-zinc-aluminum catalyst with alkylated graphite carbon, extrude it, crush it, sieve it, and lay it in a single bed; or d) Alkyl graphite carbon is mixed with copper-zinc-aluminum catalyst and laid to form a single bed.

6. A method for preparing a copper-zinc-aluminum-alkyl graphite-carbon composite catalyst according to any one of claims 1-5, characterized in that... include: 1) A solution containing copper, zinc and aluminum salts and an alkaline solution B are simultaneously added dropwise to water. The mixture reacts under alkaline conditions, the precipitate ages, is separated, and then calcined to obtain a copper-zinc-aluminum catalyst. 2) The pre-exfoliated graphite carbon dispersion is mixed with silane and reacted to obtain alkylated graphite carbon; the ratio of silane to graphite carbon is 0.2-6 mL / g; 3) Physically mix alkyl graphite carbon with copper-zinc-aluminum catalyst.

7. The preparation method according to claim 6, characterized in that: In step 1), The dropping rate of solution A is 2-4 mL / min; and / or The alkaline conditions have a pH value of 8.5-9.5; and / or The reaction temperature is 30-120°C; and / or The roasting conditions are: air atmosphere, temperature 300-400℃, time 2-6h.

8. The preparation method according to claim 6, characterized in that: In step 2), The pre-exfoliation treatment includes: dispersing graphite carbon in water, ultrasonic treatment, filtration, and drying; mixing anhydrous toluene or tetrahydrofuran with the obtained graphite carbon, and ultrasonically dispersing; and / or The reaction conditions are: inert atmosphere, temperature 50-80℃, time 6-12h.

9. The application of the copper-zinc-aluminum-alkyl graphite-carbon composite catalyst according to any one of claims 1-5 or the copper-zinc-aluminum-alkyl graphite-carbon composite catalyst obtained by the preparation method according to any one of claims 6-8 in the catalytic hydrogenation of CO2 to methanol.

10. The application according to claim 9, characterized in that: A copper-zinc-aluminum-alkylated graphite-carbon composite catalyst was loaded into a fixed-bed reactor. The catalyst was reduced before the reaction, and then subjected to a reaction at 200-300℃, a pressure of 1-9 MPa, and a space velocity of 500-50000 mL / (g). cat· Under the conditions of h), methanol is produced by hydrogenation by introducing a reaction gas; the molar ratio of H2 / CO2 in the reaction gas is 1-10:1, and CO is added with a volume percentage of 0-10%.

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