High-selectivity and high-stability catalyst for preparing methanol from carbon dioxide as well as preparation method and application of high-selectivity and high-stability catalyst

Abstract

The invention discloses a high-selectivity and high-stability catalyst for preparing methanol from carbon dioxide as well as a preparation method and application of the high-selectivity and high-stability catalyst, and belongs to the field of catalysts. The catalyst comprises a carrier and a catalytic component loaded on the carrier, the catalytic component is a copper nanocluster material or copper-based nanoparticles enriched with oxidation-state copper atoms; the catalytic component is dispersed inside and / or on the surface of the metal organic framework in an atomic form, and the catalytic component accounts for 10-50wt% of the total mass of the catalyst in terms of copper. The catalyst disclosed by the invention has the characteristic of high active metal dispersity, a synergistic effect exists among atomic-scale dispersed copper-zinc active sites, the number of copper active centers is controllable, a new zinc source is introduced as a catalytic active center, and methanol preparation through carbon dioxide hydrogenation under relatively wide temperature and pressure intervals can be realized on the catalytic effect; compared with a conventional industrial catalyst, the catalyst provided by the invention has a better reaction effect and shows excellent stability in the reaction process.

Description

Technical Field

[0001] This invention belongs to the field of catalysts, specifically relating to a highly selective and highly stable catalyst for the production of methanol from carbon dioxide, 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] Currently, the process of producing methanol from CO2 via hydrogenation faces several challenges. Firstly, CO2 is a chemically inert molecule, and the activation of its carbon-oxygen double bond is difficult. Traditional CO2 hydrogenation to methanol reactions often require high temperature and pressure conditions, but these conditions result in highly selective byproducts such as CO, water, and alkanes, which are detrimental to the reaction. Furthermore, designing catalysts for CO2 hydrogenation to methanol under mild conditions presents a challenge. Studies have shown that partially oxidized copper significantly promotes methanol selectivity, and that copper and zinc exhibit a synergistic effect, which is beneficial to the reaction.

[0004] The performance of copper-based catalysts is closely related to their structure. Studies have shown that the active centers in copper-based catalysts are mainly composed of Cu. 0 and Cu + The composition of a catalyst is crucial, and the copper dispersion (i.e., the percentage of metallic copper atoms exposed on the surface out of the total number of copper atoms) significantly affects its catalytic performance. Higher copper dispersion increases the number of active sites, thereby improving the catalyst's activity and selectivity. However, excessively high copper dispersion may lead to a reduction in oxide sites, which is detrimental to the activation and conversion of carbon dioxide. Therefore, copper dispersion needs to be controlled at an optimal value to balance activity and selectivity.

[0005] ZIF-8 is an organometallic framework prepared based on a zinc source. It has an ideal mesoporous structure and pore size. Copper-based catalysts are loaded onto ZIF-8 materials, and the framework structure effectively and uniformly disperses copper active centers, while the active sites are fully exposed. At the same time, the synergistic effect between copper and zinc greatly promotes the reaction.

[0006] Based on the above technical analysis, this catalyst is expected to achieve methanol production from carbon dioxide under mild conditions, and it exhibits better reaction performance than traditional industrial catalysts (copper, zinc, and aluminum). This catalyst has significant practical and industrial value. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention provides a highly selective and stable catalyst for the hydrogenation of carbon dioxide to methanol, its preparation method, and its applications. The catalyst provided by this invention can catalyze the hydrogenation of carbon dioxide to methanol over a wide temperature and atmospheric pressure range, and effectively suppresses the generation of side reactions during the reaction process.

[0008] In a first aspect, the present invention provides a catalyst for the hydrogenation of carbon dioxide to methanol, comprising a support and a catalytic component supported on the support.

[0009] The support is a metal-organic framework, preferably a ZIF-8 metal-organic framework. This invention innovatively introduces ZIF-8 material, utilizing it as a zinc source in copper-based catalysts.

[0010] The catalytic components are partially oxidized copper and copper-zinc, wherein the copper is dispersed in atomic form within and / or on the surface of the ZIF-8 metal-organic framework, and the copper accounts for 10wt%-50wt% of the total mass of the catalyst.

[0011] The carbon dioxide hydrogenation to methanol catalyst provided by this invention is composed of copper nanoclusters or copper-based nanoparticles enriched with oxidized copper atoms and porous material ZIF-8. It has the advantages of high dispersion, synergistic effect between atomically dispersed copper active sites and between copper and zinc, and enrichment effect of porous material. In terms of catalytic effect, it can realize the process of carbon dioxide hydrogenation to methanol in a wide temperature and pressure range such as room temperature. It is expected to solve the problem of catalytic conversion of carbon dioxide to methanol under mild conditions. Moreover, the catalyst exhibits excellent stability during the reaction process.

[0012] The copper nanoclusters have a size of 0.5-1.5 nm. The organic ligands in the copper nanoclusters do not contain phosphine or sulfur.

[0013] The copper-based nanoparticles have a particle size of 10-50 nm.

[0014] The copper nanocluster material or copper-based nanoparticles include at least one of copper clusters, copper nanoparticles, copper-cerium nanoparticles, copper-indium nanoparticles, copper-zinc nanoparticles, and copper-zirconium nanoparticles.

[0015] The copper nanoclusters were prepared by the following method:

[0016] Copper source and organic ligand are dissolved in dichloromethane or water and dispersed for 0.5 h. Then, sodium borohydride ice-water mixture or L-ascorbic acid solution is added. Under nitrogen protection and room temperature, the mixture is stirred vigorously for 10-30 min. The solvent is removed by centrifugation or rotary evaporation. After washing and drying, copper nanoclusters are obtained.

[0017] In the preparation process of the copper nanocluster material, the molar ratio of copper to organic ligand is 1:1-2, the molar ratio of copper to sodium borohydride is 1:1-4, and the molar ratio of copper to L-ascorbic acid is 1:1-2.5.

[0018] The copper-based nanoparticles were prepared by the following method:

[0019] Dissolve a copper source or other metal salt in methanol or water and disperse for 0.5 h. Adjust the pH of the system to the range of 7-9. Then add sodium borohydride ice-water mixture or L-ascorbic acid solution. Stir vigorously for 10-30 min under nitrogen protection and at room temperature. After centrifugation, washing and drying, copper-based nanoparticles are obtained.

[0020] During the preparation of the copper-based nanoparticles, sodium hydroxide or ammonia is preferred for adjusting the pH value; the molar ratio of copper to sodium borohydride is 1:1-4, and the molar ratio of copper to L-ascorbic acid is 1:1-2.5.

[0021] In the preparation process of the above copper nanoclusters and copper-based nanoparticles:

[0022] The copper source is selected from at least one of copper acetylacetone, copper nitrate, copper chloride, and copper acetate.

[0023] The organic ligands include organic carboxylic acid ligands and hydroxyl ligands, and none of the organic ligands contain phosphine or sulfur.

[0024] Furthermore, the carboxylic acid ligand is selected from at least one of glycine, trifluoroacetic acid, benzoic acid, methyl-tetra(4-carboxyphenyl)porphyrin, and 2,2'-bipyridine-5,5'-dicarboxylic acid.

[0025] Furthermore, the hydroxyl ligand is selected from at least one of sodium citrate, 8-hydroxyquinoline, and catechol.

[0026] The other metal salts include at least one of cerium nitrate, indium nitrate, zinc nitrate, and zirconium nitrate.

[0027] Secondly, the present invention provides a method for preparing the catalyst for the hydrogenation of carbon dioxide to methanol. The catalyst can be prepared using a conventional supported method or an in-situ supported method.

[0028] When prepared using conventional loading methods, the following steps are included:

[0029] Step 1: Dissolve zinc nitrate and 2-methylimidazole in methanol, sonicate for 10-30 min, then heat in a sealed container at 60-90℃ for 1-12 h, centrifuge, and wash 1-2 times to obtain a white solid; the molar ratio of 2-methylimidazole to zinc nitrate is 4:1, and the molar ratio of copper to zinc is 1:0.5-10.

[0030] Step 2: Mix the copper nanoclusters or copper-based nanoparticles with the white solid obtained in Step 1, sonicate for 10-30 min, stir for 0.5-1 h, then let stand at 20-60℃ for 1-3 h, centrifuge, wash and dry to obtain the solid product.

[0031] Step 3: Grind, calcine, press, and screen the solid product obtained in Step 2, and then activate it under a reducing atmosphere to obtain a catalyst for the hydrogenation of carbon dioxide to methanol.

[0032] When preparing the material using the in-situ loading method, the following steps are included:

[0033] Step 1: Disperse copper nanoclusters or copper-based nanoparticles with 2-methylimidazole by ultrasonication for 10-30 min, then add zinc nitrate to the system and stir for 10-30 min, followed by standing at 25-60℃ for 1-3 h; centrifuge, wash and dry the obtained suspension to obtain the solid product; the molar ratio of 2-methylimidazole to zinc nitrate is 4:1; the molar ratio of copper to zinc is 1:0.5-10.

[0034] Step 2: Grind, calcine, press, and screen the solid product obtained in Step 1, and then activate it under a reducing atmosphere to obtain a catalyst for the hydrogenation of carbon dioxide to methanol.

[0035] The calcination is carried out at 250-500℃ in an air or argon atmosphere for 1-3 hours; the tableting is carried out under a pressure of 2.0-3.0 MPa for 5-10 seconds.

[0036] The screening process involves using a standard sieve to screen out catalysts with a mesh size of 20-60, preferably 20-40 mesh.

[0037] The reducing atmosphere is a mixture of hydrogen and nitrogen, a mixture of hydrogen and argon, or a pure hydrogen atmosphere. In the hydrogen-nitrogen mixture or the hydrogen-argon mixture, the volume percentage of hydrogen is 5%-50%. The activation is a reduction treatment at 200-500℃ for 0.5-5 hours.

[0038] Furthermore, when loading copper nanoclusters, ZIF-8 requires etching with tannic acid for 10-60 minutes. The mass ratio of tannic acid to ZIF-8 is 0.001wt%-0.1wt%:1.

[0039] In the above preparation process, the centrifugation speed is 5000-10000 r / min; the drying is carried out in a vacuum oven at 80-110℃ for 8-10 h.

[0040] Thirdly, the application of the catalyst prepared by the above method in the catalytic hydrogenation of carbon dioxide to methanol reaction.

[0041] The reaction conditions were as follows: a fixed-bed reactor was used; the catalyst loading was 0.5-1 g; the carbon dioxide hydrogenation reaction pressure was 0.1-10 MPa; the reaction temperature was 180-320℃; the volume ratio of H2 to CO2 was 1:9 to 9:1; and the gas hourly space velocity was 3000-12000 h⁻¹. -1 .

[0042] Compared with the prior art, the beneficial effects of the present invention are reflected in:

[0043] 1. The catalyst of this invention exhibits excellent low-reverse water-gas shift activity and stability for selective hydrogenation of carbon dioxide to methanol.

[0044] 2. The catalyst preparation process of this invention incorporates a ZIF-8 structure, replacing the traditional zinc-zinc-aluminum catalyst, allowing zinc to act as a framework to disperse copper active centers, and the synergistic effect between copper and zinc is beneficial to the catalytic reaction.

[0045] 3. After calcination, copper nanoclusters can partially remove ligands and expose active centers, which can effectively improve the selectivity of methanol, achieve controllable acquisition of the number of active centers, and improve the reaction yield.

[0046] 4. Metal-organic frameworks increase the specific surface area of ​​active sites.

[0047] 5. The catalyst of this invention has a simple preparation process, good reproducibility, and is easy to scale up for production. It also exhibits better performance in terms of CO2 conversion rate and methanol selectivity than industrial catalysts at higher temperatures.

[0048] 6. The catalyst of this invention is a non-precious metal, which is inexpensive, has low industrial production costs, and has good application prospects. Attached Figure Description

[0049] Figure 1 This is the XRD pattern of the carbon dioxide hydrogenation to methanol catalyst prepared in Example 1.

[0050] Figure 2 This is a TEM image of the carbon dioxide hydrogenation to methanol catalyst prepared in Example 4.

[0051] Figure 3 It is the core structure of the icosahedral copper nanoclusters prepared in Example 4 (Cu nanoclusters composed of tetrahedra shared by four vertices). 13 nuclear). Detailed Implementation

[0052] To make the technical problems, technical solutions and beneficial effects of the present invention clearer and more understandable, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0053] In a first aspect, the present invention provides a catalyst for the hydrogenation of carbon dioxide to methanol, comprising a support and a catalytic component supported on the support, wherein the support is a ZIF-8 metal-organic framework, and the catalytic component is partially oxidized copper and copper-zinc, wherein the copper is atomically dispersed within and / or on the surface of the ZIF-8 metal-organic framework, and the copper accounts for 10 wt% to 50 wt% of the total mass of the catalyst.

[0054] The carbon dioxide hydrogenation to methanol catalyst provided by this invention is composed of copper nanoclusters or copper-based nanoparticles enriched with oxidized copper atoms and porous material ZIF-8. It has advantages such as high dispersion / atomic-level dispersion of copper active sites, synergistic effects between copper and zinc, and enrichment effect of porous materials. In terms of catalytic effect, it can realize the process of carbon dioxide hydrogenation to methanol in a wide temperature and pressure range, such as room temperature. It is expected to solve the problem of catalytic conversion of carbon dioxide to methanol under mild conditions. Moreover, the catalyst exhibits excellent stability during the reaction process.

[0055] The technical solution group of the present invention will be further analyzed and explained below through specific embodiments.

[0056] Example 1: Conventional Loading Method

[0057] 1. Disperse 0.04 mol of copper nitrate trihydrate in 10 mL of water, add 0.1 M of L-ascorbic acid solution (molar ratio of copper nitrate: L-ascorbic acid = 1:2) under nitrogen protection, and stir vigorously for 0.5 h to synthesize 30 nm copper nanoparticles.

[0058] 2. Dissolve 0.16 mol of 2-methylimidazole and 0.04 mol of zinc nitrate in 25 mL of methanol, sonicate for 20 min, then seal and let stand at 80 °C for 6 h, centrifuge, wash twice with methanol to obtain a white solid.

[0059] 3. Add the copper nanoparticles synthesized in step 1 to the white solid obtained in step 2 and stir for 10 min, then let stand for 1 h; centrifuge and wash the above suspension 1 to 2 times, and dry it under vacuum overnight at 90 to 110 °C to obtain a solid product, wherein the copper loading is about 30 wt%.

[0060] 4. Grind the solid product obtained in step 3 into powder using a mortar and pestle, and calcine it in a muffle furnace at 350°C for 3 hours in an air atmosphere to obtain a solid. Grind the obtained solid into powder, and then press it into tablets using a pressure of 2.0~3.0 MPa. Grind and screen out catalyst precursors with particles of 20~40 mesh. Activate the catalyst at 300°C for 2 hours in an H2 / N2 or H2 / Ar or pure H2 atmosphere with a H2 concentration of 5%~50% to obtain a carbon dioxide hydrogenation to methanol catalyst.

[0061] 5. The obtained catalyst was used for evaluation in the carbon dioxide hydrogenation reaction. The specific operation was as follows: a fixed-bed reactor was used, with a catalyst loading of 1 g. The carbon dioxide hydrogenation reaction pressure was adjusted to 3 MPa, the reaction temperature to 200–320 °C, the volume ratio of H2 to CO2 to be 3:1, and the gas hourly space velocity (GHSV) to be 5000–11000 h⁻¹. -1 The performance evaluation results of the catalyst are shown in Table 1.

[0062] Example 2: Conventional Loading Method

[0063] 1. Disperse 0.04 mol of copper nitrate trihydrate in 10 mL of dichloromethane, add 0.05 M sodium borohydride solution (molar ratio of copper nitrate: sodium borohydride = 1:2) under nitrogen protection, and stir vigorously for 0.5 h to synthesize 20 nm copper nanoparticles.

[0064] 2. Dissolve 0.16 mol of 2-methylimidazole and 0.04 mol of zinc nitrate in 25 mL of methanol solution, sonicate for 20 min, then seal and let stand at 80 °C for 6 h, centrifuge, wash twice with methanol to obtain a white solid with a copper loading of about 30 wt%.

[0065] 3. Add the copper nanoparticles synthesized in step 1 to the white solid obtained in step 2 and stir for 10 min, then let stand for 1 h; centrifuge and wash the above suspension 1-2 times, and dry it overnight at 90-110℃ to obtain the solid product;

[0066] 4. Grind the solid product obtained in step 3 into powder using a mortar and pestle, and calcine it in a muffle furnace at 350°C for 3 hours in an air atmosphere to obtain a solid. Grind the obtained solid into powder, and then press it into tablets using a pressure of 2.0~3.0 MPa. Grind and screen out catalyst precursors with particles of 20~40 mesh. Activate the catalyst at 300°C for 2 hours in an H2 / N2 or H2 / Ar or pure H2 atmosphere with a H2 concentration of 5%~50% to obtain a carbon dioxide hydrogenation to methanol catalyst.

[0067] Example 3: Conventional Loading Method

[0068] 1. Disperse 0.04 mol of copper nitrate trihydrate and 0.04 mol of cerium nitrate hexahydrate in 10 mL of dichloromethane, add 0.05 M sodium borohydride solution (molar ratio of copper nitrate: sodium borohydride = 1:3) under nitrogen protection, and stir vigorously for 0.5 h to synthesize 30 nm copper cerium nanoparticles.

[0069] 2. Dissolve 0.16 mol of 2-methylimidazole and 0.04 mol of zinc nitrate in 25 mL of methanol solution, sonicate for 20 min, then seal and let stand at 80 °C for 6 h, centrifuge, wash twice with methanol to obtain a white solid with a copper loading of about 25 wt%.

[0070] 3. Add the copper-cerium nanoparticles synthesized in step 1 to the white solid obtained in step 2 and stir for 10 min, then let stand for 1 h; centrifuge and wash the above suspension 1-2 times, and dry it overnight at 90-110℃ to obtain the solid product;

[0071] 4. Grind the solid product obtained in step 3 into powder using a mortar and pestle, and calcine it in a muffle furnace at 350°C for 3 hours in an air atmosphere to obtain a solid. Grind the obtained solid into powder, and then press it into tablets using a pressure of 2.0~3.0 MPa. Grind and screen out catalyst precursors with particles of 20~40 mesh. Activate the catalyst at 300°C for 2 hours in an H2 / N2 or H2 / Ar or pure H2 atmosphere with a H2 concentration of 5%~50% to obtain a carbon dioxide hydrogenation to methanol catalyst.

[0072] Example 4: Conventional Loading Method

[0073] 1. Dissolve 0.001 mol of 2,2'-bipyridine-5,5'-dicarboxylic acid in NaOH solution at pH=10, add 0.002 mol of copper nitrate, stir at 60℃ for 0.5 h, slowly add 0.002 mol of sodium citrate solution, continue stirring at 70℃ for 1 h, add 0.003 mol of L-ascorbic acid solution dropwise under nitrogen protection, heat to 80℃ and stir for 2 h, centrifuge to collect the solid, wash twice with ethanol to obtain 1.1 nm icosahedral copper nanoclusters Cu. 13 (Molecular formula: Na6[Cu)) 13 (bpdc)4(cit)2]6).

[0074] 2. Dissolve 0.16 mol of 2-methylimidazole and 0.04 mol of zinc nitrate in 25 mL of methanol solution, sonicate for 20 min, then seal and let stand at 80 °C for 6 h, centrifuge, take the solid, then etch with 0.01 g of tannic acid for 20 min, wash twice with methanol, and centrifuge.

[0075] 3. Add the copper nanoclusters synthesized in step 1 to the solid obtained in step 2 and stir for 10 min, then let stand for 1 h; centrifuge and wash the above suspension 1 to 2 times, and dry it under vacuum overnight at 90 to 110 °C to obtain a solid product, wherein the copper loading is about 10 wt%.

[0076] 4. Grind the solid product obtained in step 3 into powder using a mortar and pestle, then calcine it in a muffle furnace at 350°C for 3 hours under an argon atmosphere to obtain a solid. Grind the obtained solid into powder, then press it into tablets using a pressure of 2.0~3.0 MPa. Grind and sieve the tablets to obtain catalyst precursors with particles of 20~40 mesh. Activate the catalyst at 300°C for 2 hours under an H2 / N2 or H2 / Ar or pure H2 atmosphere with a H2 concentration of 5%~50% to obtain a carbon dioxide hydrogenation to methanol catalyst. Figure 1 The image shown is its TEM image.

[0077] Example 5: In-situ Loading Method

[0078] 1. Dissolve 0.001 mol of 2,2'-bipyridine-5,5'-dicarboxylic acid in NaOH solution at pH=10, add 0.002 mol of copper nitrate, stir at 60℃ for 0.5 h, slowly add 0.002 mol of sodium citrate solution, continue stirring at 70℃ for 1 h, add 0.003 mol of L-ascorbic acid solution dropwise under nitrogen protection, heat to 80℃ and stir for 2 h, centrifuge to collect the solid, wash twice with ethanol to obtain 1.1 nm icosahedral copper nanoclusters Cu. 13 (Molecular formula: Na6[Cu)) 13 (bpdc)4(cit)2]6).

[0079] 2. The copper nanoclusters obtained in step 1 were ultrasonically reacted with 0.32 mol of 2-methylimidazole for 10-30 min, then 0.08 mol of zinc nitrate was added and stirred for 10-30 min. The mixture was then allowed to stand at 25-60℃ for 1-3 h, followed by etching with 0.01 mol of tannic acid for 20 min. The suspension was centrifuged and washed 1-2 times, then dried under vacuum overnight at 90-110℃ to obtain a solid product with a copper loading of approximately 10 wt%.

[0080] 3. Grind the solid product obtained in step 2 into powder using a mortar and pestle, and calcine it in a muffle furnace at 350°C for 3 hours under an argon atmosphere to obtain a solid. Grind the obtained solid into powder, and then press it into tablets using a pressure of 2.0~3.0 MPa. Grind and screen out catalyst precursors with particles of 20~40 mesh. Activate the catalyst at 300°C for 2 hours under an H2 / N2 or H2 / Ar or pure H2 atmosphere with a H2 concentration of 5%~50% to obtain a carbon dioxide hydrogenation to methanol catalyst.

[0081] Example 6: In-situ Loading Method

[0082] 1. Disperse 0.04 mol of copper nitrate trihydrate in 10 mL of water, add 0.1 M of L-ascorbic acid solution (molar ratio of copper nitrate: L-ascorbic acid = 1:1) under nitrogen protection, and stir vigorously for 0.5 h to synthesize copper nanoparticles of 40 nm.

[0083] 2. The copper-based nanoparticles obtained in step 1 are sonicated with 0.16 mol of 2-methylimidazole for 10-30 min, then 0.04 mol of zinc nitrate is added and stirred for 10-30 min, and then allowed to stand at 25-60℃ for 1-3 h.

[0084] The suspension was centrifuged and washed 1-2 times, then dried overnight at 90-110°C to obtain a solid product, in which the copper loading was approximately 30 wt%.

[0085] 3. The obtained solid product is dried and ground into powder using a mortar and pestle. It is then placed in a muffle furnace and calcined at 350°C in air for 3 hours to obtain a solid. The obtained solid is ground into powder and then pressed into tablets using a pressure of 2.0~3.0 MPa. The catalyst precursor with particles of 20~40 mesh is obtained by grinding and screening. The catalyst is activated at 300°C for 2 hours in an atmosphere of H2 / N2 or H2 / Ar or pure H2 with a concentration of 5%~50% to obtain a catalyst for the hydrogenation of carbon dioxide to methanol.

[0086] Example 7: In-situ Loading Method

[0087] 1. Disperse 0.04 mol of copper nitrate trihydrate and 0.04 mol of zirconium nitrate pentahydrate in 10 mL of water, add 0.1 M L-ascorbic acid solution (molar ratio of copper nitrate: L-ascorbic acid = 1:1) under nitrogen protection, and stir vigorously for 0.5 h to synthesize 40 nm copper zirconium nanoparticles.

[0088] 2. The copper zirconium nanoparticles obtained in step 1 were ultrasonicated with 0.16 mol of 2-methylimidazole for 10-30 min, and then 0.04 mol of zinc nitrate was added and stirred for 10-30 min. After that, the mixture was allowed to stand at 25-60℃ for 1-3 h.

[0089] The suspension was centrifuged and washed 1-2 times, then dried overnight at 90-110°C to obtain a solid product, in which the copper loading was approximately 25 wt%.

[0090] 3. The obtained solid product is dried and ground into powder using a mortar and pestle. It is then placed in a muffle furnace and calcined at 350°C in air for 3 hours to obtain a solid. The obtained solid is ground into powder and then pressed into tablets using a pressure of 2.0~3.0 MPa. The catalyst precursor with particles of 20~40 mesh is obtained by grinding and screening. The catalyst is activated at 300°C for 2 hours in an atmosphere of H2 / N2 or H2 / Ar or pure H2 with a concentration of 5%~50% to obtain a catalyst for the hydrogenation of carbon dioxide to methanol.

[0091] Example 8: In-situ Loading Method

[0092] 1. Disperse 0.04 mol of copper nitrate trihydrate in 10 mL of water, add 0.1 M of L-ascorbic acid solution (molar ratio of copper nitrate: L-ascorbic acid = 1:2) under nitrogen protection, and stir vigorously for 0.5 h to synthesize copper nanoparticles of 30 nm.

[0093] 2. The obtained copper nanoparticles were ultrasonically reacted with 0.16 mol of 2-methylimidazole for 10-30 min, then 0.04 mol of zinc nitrate was added and stirred for 10-30 min. The mixture was then allowed to stand at 25-60℃ for 1-3 h. The suspension was centrifuged and washed 1-2 times, and dried overnight at 90-110℃ to obtain a solid product with a copper loading of approximately 30 wt%.

[0094] 3. Grind the obtained solid product into powder using a mortar and pestle, then calcine it in a muffle furnace at 350°C for 3 hours in air atmosphere to obtain a solid. Grind the obtained solid into powder, then press it into tablets using a pressure of 2.0~3.0 MPa. Grind and screen the tablets to obtain catalyst precursors with particles of 20~40 mesh. Activate the catalyst at 300°C for 2 hours in an atmosphere of H2 / N2 or H2 / Ar or pure H2 with a H2 concentration of 5%~50% to obtain a catalyst for the hydrogenation of carbon dioxide to methanol.

[0095]

[0096] As shown in Table 1, smaller copper nanoparticle sizes result in superior catalytic performance (Examples 1 and 2). Comparing different types of nanoparticles, copper-cerium nanoparticles are found to promote greater methanol selectivity (Examples 1, 3, 6, and 7). Comparing the effects of supported nanoclusters and nanoparticles on catalytic performance, nanoclusters exhibit superior methanol selectivity, indicating that clusters have very high industrial application potential (Examples 1 and 4). Comparing the effects of catalysts synthesized with the same support using conventional and in-situ supported methods on catalytic performance, in-situ supported catalysts exhibit superior catalytic performance (Examples 1, 8, 4, and 5).

[0097] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A highly selective and highly stable catalyst for the production of methanol from carbon dioxide, characterized in that: The catalyst includes a support and a catalytic component supported on the support; The catalytic component is a copper nanocluster material enriched with oxidized copper atoms or copper-based nanoparticles. The catalytic component is dispersed in atomic form within and / or on the surface of the metal-organic framework, and the catalytic component, based on copper, accounts for 10wt%-50wt% of the total mass of the catalyst.

2. The highly selective and highly stable carbon dioxide-to-methanol catalyst according to claim 1, characterized in that: The copper nanoclusters have a size of 0.5-1.5 nm; the copper-based nanoparticles have a particle size of 10-50 nm.

3. The highly selective and highly stable carbon dioxide-to-methanol catalyst according to claim 1, characterized in that: The carrier is a ZIF-8 metal-organic framework.

4. The highly selective and highly stable carbon dioxide-to-methanol catalyst according to claim 2, characterized in that: The copper nanoclusters were prepared by the following method: Copper source and organic ligand are dissolved in dichloromethane or water and dispersed for 0.5 h. Then, sodium borohydride ice-water mixture or L-ascorbic acid solution is added. Under nitrogen protection and room temperature, the mixture is stirred vigorously for 10-30 min. The solvent is removed by centrifugation or rotary evaporation. After washing and drying, copper nanoclusters are obtained. The molar ratio of copper to organic ligands is 1:1-2, the molar ratio of copper to sodium borohydride is 1:1-4, and the molar ratio of copper to L-ascorbic acid is 1:1-2.

5.

5. The highly selective and highly stable carbon dioxide-to-methanol catalyst according to claim 2, characterized in that: The copper-based nanoparticles were prepared by the following method: Dissolve a copper source or other metal salt in methanol or water and disperse for 0.5 h. Adjust the pH of the system to the range of 7-9. Then add sodium borohydride ice water mixture or L-ascorbic acid solution. Stir vigorously for 10-30 min under nitrogen protection and room temperature. After centrifugation, washing and drying, copper-based nanoparticles are obtained. During the preparation of the copper-based nanoparticles, sodium hydroxide or ammonia is preferred for adjusting the pH value; the molar ratio of copper to sodium borohydride is 1:1-4, and the molar ratio of copper to L-ascorbic acid is 1:1-2.

5.

6. The method for preparing the highly selective and highly stable carbon dioxide-to-methanol catalyst according to any one of claims 1-5, characterized in that... Includes the following steps: Step 1: Dissolve zinc nitrate and 2-methylimidazole in methanol, disperse evenly by ultrasonication, then heat in a sealed container at 60-90℃ for 1-12 hours, centrifuge, and wash 1-2 times to obtain a white solid; the molar ratio of 2-methylimidazole to zinc nitrate is 4:1, and the molar ratio of copper to zinc is 1:0.5-10. Step 2: Mix the copper nanoclusters or copper-based nanoparticles with the white solid obtained in Step 1, disperse by ultrasonication, stir for 0.5-1 h, then let stand at 20-60℃ for 1-3 h, centrifuge, wash and dry to obtain the solid product; Step 3: Grind, calcine, press, and screen the solid product obtained in Step 2, and then activate it under a reducing atmosphere to obtain a catalyst for the hydrogenation of carbon dioxide to methanol.

7. The method for preparing the highly selective and highly stable carbon dioxide-to-methanol catalyst according to any one of claims 1-5, characterized in that... Includes the following steps: Step 1: Disperse copper nanoclusters or copper-based nanoparticles with 2-methylimidazole using ultrasonication, then add zinc nitrate to the system and stir for 10-30 min. Allow the mixture to stand at 25-60℃ for 1-3 h. Centrifuge, wash, and dry the resulting suspension to obtain a solid product. The molar ratio of 2-methylimidazole to zinc nitrate is 4:1; the molar ratio of copper to zinc is 1:0.5-10. Step 2: Grind, calcine, press, and screen the solid product obtained in Step 1, and then activate it under a reducing atmosphere to obtain a catalyst for the hydrogenation of carbon dioxide to methanol.

8. The use of the catalyst according to any one of claims 1-5 in the catalytic hydrogenation of carbon dioxide to methanol reaction.

9. The application according to claim 8, characterized in that: A fixed-bed reactor was used, with a catalyst loading of 0.5-1 g, a carbon dioxide hydrogenation reaction pressure of 0.1-10 MPa, a reaction temperature of 180-320℃, a H2 to CO2 volume ratio of 1:9 to 9:1, and a gas hourly space velocity of 3000-12000 h⁻¹. -1 .

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