Preparation and application of a highly stable catalyst for CO2 hydrogenation to ethanol

Abstract

The invention discloses a kind of preparation and application of high stability catalyst for CO2 hydrogenation to ethanol, belong to carbon dioxide conversion application field.Catalyst of the present invention is by active component polyatomic site (atomic number is 2 10), metal oxide support and SiO2 membrane reactor composition.Catalyst of the present invention constructs polyatomic supported catalyst by stabilizing metal precursor in organometallic framework material, and it shows excellent CO2 hydrogenation performance, ethanol selectivity>99%.At the same time, catalyst is encapsulated in hydrophobic surface modified SiO2 membrane reactor, the water-stabilized active center configuration generated by in-situ enrichment improves CO2 stability during hydrogenation reaction.The present invention accurately realizes the construction of different atomic number active site catalysts by the structural confinement effect of organometallic framework material, and then improves CO2 hydrogenation to ethanol catalytic performance, and improves the stability of center configuration by rationally constructing membrane reactor, and then improves the stability of catalyst.

Description

Technical Field

[0001] The present invention relates to the preparation and application of a high-stability catalyst for producing ethanol by hydrogenating CO2, and belongs to the field of carbon dioxide conversion applications. Background Art

[0002] The massive CO2 emissions from the over-consumption of carbon-based fossil resources have caused major environmental problems such as global warming, climate change, and ocean acidification. Capturing CO2 and converting it into useful fuels and chemicals offers a promising alternative for reducing atmospheric CO2 concentrations while alleviating large-scale dependence on fossil resources.

[0003] In recent years, the catalytic conversion of CO2 into C1 compounds and high carbon (C 2+ ) organic compounds have become an unprecedented hot topic. CO2 conversion is directly achieved by using heat, light, electricity and biocatalysis, or indirectly through the series / relay catalysis of intermediates. In these studies, the efficient and highly selective synthesis of high value-added C 2+ The most challenging goal is to achieve a product, especially nearly 100% synthesis of a single product molecule, because it is extremely difficult to control carbon-carbon coupling and related side reactions. 2+ Among the products, ethanol is an important chemical that can not only serve as a high-quality non-toxic fuel component / hydrogen carrier / solvent, but can also be directly or further converted into ethylene for use in the synthesis of a variety of related chemicals. At the same time, CO2 is also a non-toxic, cheap, abundant, and renewable C1 resource, so converting CO2 into high-value-added chemicals is of great practical significance. Ethanol is an important basic chemical raw material and is widely used as a disinfectant, reaction solvent, and gasoline additive. Directly converting carbon dioxide into ethanol is an ideal process for eliminating greenhouse gases and producing valuable products. However, this process is hindered by low activity, which is due to the high thermodynamic stability and chemical inertness of CO2, as well as the formation of by-products (such as CH4, CO, and CH3OH, etc.). Therefore, the development of highly active and selective catalysts for ethanol production remains a huge challenge.

[0004] The reported highly selective hydrogenation of CO2 to ethanol is mainly carried out in batch reactors, using Cu-based catalysts for photocatalysis and electrocatalysis, or Rh-based, Co-based, Ir-based and alloy catalysts for thermal catalysis. However, discontinuous batch reaction systems have the serious problem of separating small amounts of ethanol product from the solvent. In practical applications, solvent-free continuous flow fixed-bed reactors are the most likely to achieve industrial application. However, the main challenge currently is that the catalysts reported in continuous flow fixed-bed reactors lack the ability to convert the active intermediate *CH x OH dissociates into *CH xand subsequently coupled with *CO, thus producing mainly C1 by-products such as methanol, methane and carbon monoxide.

[0005] Therefore, developing a continuous flow fixed-bed reaction system for CO2 hydrogenation to ethanol with high activity, high selectivity and excellent stability remains a daunting challenge. Summary of the Invention

[0006] To address these issues, the present invention employs a metal organic framework (MOF) structural stabilization strategy to stabilize the active center configuration, regulate the active center configuration during the synthesis process, and regulate the precursor to prepare a diatomic-loaded catalyst. This active center can efficiently catalyze the conversion of CO2 into a single product, ethanol, during the CO2 hydrogenation process to produce ethanol, effectively reducing the formation of byproducts such as CO, CH4, and CH3OH. Simultaneously, a membrane reactor is constructed outside the active component, and the SiO2 shell is modified with hydrophobic molecules, allowing it to concentrate the H2O produced in the CO2 hydrogenation reaction around the diatomic catalyst. This water-rich environment effectively stabilizes the diatomic configuration, giving it greater stability during the catalytic process.

[0007] The first object of the present invention is to provide a method for preparing a highly stable catalyst for catalytic CO2 hydrogenation to ethanol, comprising the following steps:

[0008] (1) dissolving a carrier precursor in a medium, adding a complexing agent to carry out a coordination reaction to generate an organic metal framework material (MOFs), filtering and collecting the solid after the reaction, and drying to obtain a solid N-MOFs carrier;

[0009] (2) dispersing the N-MOFs support in an organic solvent to obtain a suspension, then adding a metal precursor to the suspension, stirring, centrifuging, and drying to obtain a solid M@N-MOFs material;

[0010] (3) dispersing the M@N-MOFs material in an ethanol aqueous solution of a surfactant, adding ammonia water and stirring, then adding ethyl orthosilicate to react, stirring, filtering, collecting the solid, and drying to obtain the M@N-MOFs@SiO2 material; and then calcining to obtain the MN@Si material;

[0011] (4) The MN@Si material was dispersed in a solvent, and an organic hydrophobic agent was added for surface modification. The mixture was stirred, centrifuged, and the solid was collected and dried to obtain a highly stable catalyst for catalyzing CO2 hydrogenation to ethanol, which was designated as MN@Si-R catalyst.

[0012] In one embodiment of the present invention, the carrier precursor in step (1) is one or more of cerium salts, zirconium salts, indium salts, zinc salts, iron salts, cobalt salts, titanium salts, vanadium salts, chromium salts, and manganese salts. The salts include any one or more of nitrates, hydrochlorides, and sulfates.

[0013] In one embodiment of the present invention, the complexing agent in step (1) is one or more of 2-methylimidazole, terephthalic acid, trimesic acid, and 2-aminoterephthalic acid.

[0014] In one embodiment of the present invention, the medium in step (1) is water and / or ethanol, and specifically a mixture of water and ethanol in a volume ratio of 1:1.

[0015] In one embodiment of the present invention, the molar ratio of the carrier precursor to the complexing agent in step (1) is (0.05-20): 1. Specifically, it can be 1: (1-5).

[0016] In one embodiment of the present invention, the organic solvent in step (2) is one of N,N-dimethylformamide, toluene, methanol and ethanol.

[0017] In one embodiment of the present invention, the metal precursor in step (2) is a soluble compound of one or more of palladium, iridium, ruthenium, platinum, rhodium, copper, gold, silver, cobalt and nickel.

[0018] In one embodiment of the present invention, the mass ratio of the metal precursor to the N-MOFs support in step (2) is (0.0005-0.5):1. Specifically, it can be 0.01:1.

[0019] In one embodiment of the present invention, the volume ratio of water to ethanol in the ethanol aqueous solution of the surfactant in step (3) is (0.1-20):1. It can further be 1.5:1.

[0020] In one embodiment of the present invention, the surfactant in step (3) is one or more of cetyl ammonium bromide, cetyl ammonium bromide, cetyl ammonium bromide, and cetyl ammonium bromide.

[0021] In one embodiment of the present invention, the mass ratio of the surfactant to the M@N-MOFs in step (3) is 1:1.

[0022] In one embodiment of the present invention, the concentration of the surfactant relative to the ethanol aqueous solution in step (3) is 1-10 g / L.

[0023] In one embodiment of the present invention, the volume ratio of ammonia water to tetraethyl orthosilicate in step (3) is 1:1.

[0024] In one embodiment of the present invention, in step (3), the volume mass ratio of ethyl orthosilicate to M@N-MOFs material is 0.1-10 mL / g.

[0025] In one embodiment of the present invention, the calcination temperature in step (3) is 400° C. and the calcination time is 4 hours.

[0026] In one embodiment of the present invention, the solvent in step (4) is one of N,N-dimethylformamide, toluene, methanol and ethanol.

[0027] In one embodiment of the present invention, the mass ratio of the organic hydrophobic agent to the MN@Si material in step (4) is (0.05-50):1. Specifically, 1:1 can be selected.

[0028] In one embodiment of the present invention, the organic hydrophobic agent in step (4) includes one or more of trimethylchlorosilane, methyltrimethoxysilane, propyltrimethoxysilane, trimethyloxyphenylsilane and hexadecyltrimethoxysilane.

[0029] The present invention provides a high-stability catalyst for catalyzing CO2 hydrogenation to ethanol based on the above method.

[0030] In one embodiment of the present invention, the metal active components in the catalyst are highly dispersed on the carrier in the form of sub-nano clusters, with the number of atoms being 2-10.

[0031] In one embodiment of the present invention, the content of active components in the catalyst accounts for 0.01% to 5% of the total mass of the catalyst.

[0032] In one embodiment of the present invention, the active component and the carrier are encapsulated in a SiO2 nanomembrane reactor with a hydrophobic surface.

[0033] The present invention also provides a method for producing ethanol by hydrogenating CO2, in which the above catalyst is used as a hydrogenation catalyst.

[0034] In one embodiment of the present invention, the method is to introduce CO2 / H2 synthesis gas into a catalyst for CO2 hydrogenation to ethanol, and carry out the CO2 hydrogenation to ethanol reaction in a fixed bed.

[0035] In one embodiment of the present invention, the catalyst does not need to be pre-treated for activation before use.

[0036] In one embodiment of the present invention, the reaction conditions for the CO2 hydrogenation to ethanol are: CO2:H2=1:3-4, the reaction temperature is 150-400°C, the reaction pressure is 0.1-5MPa, and the feed gas flow rate is 5-200mL / min.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] (1) The present invention introduces the concept of structural confinement of an organic metal framework material to regulate the configuration of the active center of the catalyst. The metal precursor confined in the organic metal framework material can be regulated to achieve different atomic configurations (the number of atoms is controlled within the range of 2-10) during high-temperature calcination, thereby preparing a highly dispersed multi-site catalyst supported by a carrier. The catalyst of the present invention, which is constructed by dispersing atomic clusters on the surface of carrier nanoparticles, shows excellent CO2 hydrogenation performance, with an ethanol selectivity of >99%. The present invention achieves atomic configuration regulation by regulating the active component precursor and introducing a method of structural confinement, thereby improving the catalytic performance of CO2 hydrogenation to ethanol.

[0039] (2) This invention introduces the concept of a membrane reactor. By constructing a SiO2 shell with a hydrophobic surface on the exterior of the catalyst, the water generated by the CO2 hydrogenation reaction is encapsulated in situ within the membrane reactor. The water-rich environment created by this membrane reactor is conducive to the stability of the active components, making it difficult for polyatomic sites to agglomerate and sinter, resulting in high stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 This is a microstructure image of the catalyst (a diatomic Pd-loaded CeO2 catalyst encapsulated in a hydrophobic SiO2 membrane reactor), which includes: a diatomic Pd-loaded CeO2 catalyst and a hydrophobic SiO2 membrane reactor.

[0041] Figure 2 This is the XANES data analysis diagram of the fresh catalyst obtained in Example 1.

[0042] Figure 3 This is the EXAFS data analysis diagram of the fresh catalyst obtained in Example 1.

[0043] Figure 4 This is the XANES data analysis diagram of the catalyst obtained in Example 1 after the catalyst reacted for 10 hours.

[0044] Figure 5 This is the EXAFS data analysis diagram of the catalyst obtained in Example 1 after the reaction for 10 hours. DETAILED DESCRIPTION

[0045] In order to illustrate the present invention more clearly, the present invention is further described below with reference to specific examples. Those skilled in the art should understand that the specific description below is illustrative rather than restrictive and should not be used to limit the scope of protection of the present invention.

[0046] Catalyst performance evaluation was conducted in a fixed-bed reactor. The specific catalytic performance evaluation method is as follows: No catalyst treatment is required, and the catalyst mass is 300 mg. A feed gas with a CO2:H2 ratio of 1:3 is directly introduced into a fixed-bed reactor (with an inner diameter of 8 mm). The reaction pressure is adjusted to 0.1-5 MPa, and the flow rate is adjusted to 5-200 mL / min. The fixed-bed reactor temperature is raised at 5°C / min to the desired temperature, and the reaction is then initiated. The product is maintained at 120°C and then analyzed online by chromatography.

[0047] CO2 conversion rate = (CO2 moles before reaction - CO2 moles after reaction) / CO2 moles before reaction × 100%;

[0048] Product selectivity = number of moles of product × number of carbon atoms in the product molecule / (number of moles of CO2 before reaction - number of moles of CO2 after reaction) × 100%.

[0049] Catalyst system for CO2 hydrogenation to ethanol and its preparation method:

[0050] Example 1

[0051] In the first step, 0.02 mol of cerium nitrate and 0.02 mol of trimellitic acid were dissolved in a mixture of 400 mL of deionized water and 400 mL of ethanol, followed by vigorous stirring for 1 hour. Finally, the product was filtered, washed with water and ethanol, and dried at 100°C overnight. This was recorded as the Ce-MOFs precursor support.

[0052] In the second step, 1 g of Ce-MOFs support was dispersed in 15 mL of ethanol to obtain a suspension. 10 mg of palladium nitrate was then added to the suspension, stirred for 12 h, and then centrifuged with ethanol and dried at 100 ° C overnight. This suspension was recorded as Pd@Ce-MOFs material.

[0053] The third step is to disperse 1g of Pd@Ce-MOFs material in a water / ethanol mixed solution of hexadecyl ammonium bromide (wherein hexadecyl ammonium bromide is 1g, water is 180mL, and ethanol is 120mL), add 0.5mL of ammonia water and stir, then add 0.5mL of ethyl orthosilicate, and continue stirring for 6h to react. The product is filtered and washed with ethanol, dried at 100°C overnight, and recorded as 1Pd@Ce-MOFs@SiO2 material. Finally, it is calcined at 400°C in a muffle furnace for 4h and recorded as 1PdCe@Si material;

[0054] In the fourth step, 0.5 g of PdCe@Si material was dispersed in 10 mL of toluene, 0.5 g of trimethylsilyl chloride was added, stirred for 24 h, then centrifuged and washed with ethanol, and dried at 100 °C overnight, which was recorded as 1PdCe@Si-C3 catalyst.

[0055] The coordination results of the materials were characterized by EXAFS and XANES. Figure 2 XANES data analysis of the fresh catalyst obtained, Figure 3 EXAFS data analysis of the fresh catalyst obtained.

[0056] According to the above Figure 2-3 The data in the paper prove that the catalyst has Pd-O and Pd-Pd coordination structures, and the Pd-Pd bond coordination number is approximately 1, indicating that the Pd species in the material are mainly in a di-Pd configuration, that is, diatomic loading.

[0057] Example 2

[0058] The palladium nitrate in the second step of Example 1 was replaced with ruthenium acetylacetonate, and the other steps and operations remained unchanged to obtain the 1RuCe@Si-C3 catalyst.

[0059] Example 3

[0060] The palladium nitrate in the second step of Example 1 was replaced with iridium acetylacetonate, and the other steps and operations remained unchanged to obtain the 1IrCe@Si-C3 catalyst.

[0061] Example 4

[0062] The palladium nitrate in the second step of Example 1 was replaced with rhodium acetylacetonate, and the other steps and operations remained unchanged to obtain the 1RhCe@Si-C3 catalyst.

[0063] Example 5

[0064] The cerium nitrate in the first step of Example 1 was replaced with zinc nitrate, and the other steps and operations remained unchanged to obtain the 1PdZn@Si-C3 catalyst.

[0065] Example 6

[0066] The cerium nitrate in the first step of Example 1 was replaced with indium nitrate, and the other steps and operations remained unchanged to obtain the 1PdIn@Si-C3 catalyst.

[0067] Example 7

[0068] The cerium nitrate in the first step of Example 1 was replaced with zirconium nitrate, and the other steps and operations remained unchanged to obtain the 1PdZr@Si-C3 catalyst.

[0069] Application of CO2 hydrogenation catalyst to ethanol:

[0070] The catalyst (300 mg) was placed in a fixed-bed reactor under the following conditions: CO₂:H₂ = 1:3, temperature 240°C, 3 MPa, and a feed gas flow rate of 15 mL / min. The reaction was continued for 10 hours. The conversion and product selectivity or distribution results are shown in Table 1.

[0071] Example 8

[0072] The 1PdCe@Si-C3 catalyst was placed in a fixed-bed reactor and the reaction temperature was changed to 200°C, while other parameters remained unchanged. The conversion and product selectivity or distribution results are shown in Table 1.

[0073] Example 9

[0074] The 1PdCe@Si-C3 catalyst was placed in a fixed-bed reactor and the reaction temperature was changed to 220°C, while other parameters remained unchanged. The conversion and product selectivity or distribution results are shown in Table 1.

[0075] Example 10

[0076] The 1PdCe@Si-C3 catalyst was placed in a fixed-bed reactor and the reaction temperature was changed to 260°C, while other parameters remained unchanged. The conversion and product selectivity or distribution results are shown in Table 1.

[0077] Example 11

[0078] The 1PdCe@Si-C3 catalyst was placed in a fixed-bed reactor and the reaction temperature was changed to 280°C, while other parameters remained unchanged. The conversion and product selectivity or distribution results are shown in Table 1.

[0079] Example 12

[0080] The 1PdCe@Si-C3 catalyst was placed in a fixed-bed reactor and the reaction pressure was changed to 1 MPa, while other parameters remained unchanged. The conversion and product selectivity or distribution results are shown in Table 1.

[0081] Example 13

[0082] The 1PdCe@Si-C3 catalyst was placed in a fixed-bed reactor and the reaction pressure was changed to 2 MPa, while other parameters remained unchanged. The conversion and product selectivity or distribution results are shown in Table 1.

[0083] Example 14

[0084] The 1PdCe@Si-C3 catalyst was placed in a fixed-bed reactor and the feed gas flow rate was changed to 30 mL / min, while other parameters remained unchanged. The conversion and product selectivity or distribution results are shown in Table 1.

[0085] Example 15

[0086] The 1PdCe@Si-C3 catalyst was placed in a fixed-bed reactor and the feed gas flow rate was changed to 60 mL / min, while other parameters remained unchanged. The conversion and product selectivity or distribution results are shown in Table 1.

[0087] Table 1 Catalytic performance of different catalysts

[0088]

[0089] As can be seen from the results in Table 1, the catalyst prepared by the catalyst preparation method of the present invention exhibits good CO2 conversion rate and ethanol selectivity (>99%) for the CO2 hydrogenation to ethanol reaction under appropriate conditions.

[0090] The catalyst was taken out after continuous reaction for 10 hours in Example 1 and tested by EXAFS and XANES. Figure 4 and Figure 5 As shown: the catalyst after the reaction still maintains a good diatomic loading morphology.

[0091] Comparative Example 1

[0092] The Ce@Si catalyst was prepared using the same catalyst preparation steps as in Example 1, except that the amount of palladium nitrate added in Step 2 was changed to 0 mg, and the amount of hexadecyltrimethoxysilane added in Step 4 was changed to 0 mg. The catalyst was then evaluated for CO2 hydrogenation performance in a fixed-bed reactor under the following conditions: 240°C, 3 MPa, a feed gas flow rate of 15 mL / min, and a reaction time of 10 h. The conversion and product selectivity or distribution are shown in Table 2.

[0093] Comparative Example 2

[0094] The catalyst preparation steps were the same as in Example 1, except that the amount of trimethylchlorosilane added in step 4 was changed to 0 mg. The 1PdCe@Si catalyst was obtained. Its CO2 hydrogenation performance was evaluated in a fixed-bed reactor under the following conditions: 240°C, 3 MPa, a feed gas flow rate of 15 mL / min, and a reaction time of 10 h. The conversion and product selectivity or distribution are shown in Table 2.

[0095] Comparative Example 3

[0096] The Ce@Si-C3 catalyst was prepared using the same catalyst preparation steps as in Example 1, except that the amount of palladium nitrate added in the second step was changed to 0 mg. The CO2 hydrogenation performance was evaluated in a fixed-bed reactor under the following conditions: 240°C, 3 MPa, a feed gas flow rate of 15 mL / min, and a reaction time of 10 h. The conversion and product selectivity or distribution are shown in Table 2.

[0097] Comparative Example 4

[0098] The trimethylchlorosilane used in step 4 of Example 1 was replaced with methyltrimethoxysilane. The remaining catalyst preparation steps were the same as in Example 1 to obtain the 1PdCe@Si-Cl catalyst. Its CO2 hydrogenation performance was evaluated in a fixed-bed reactor under the following conditions: 240°C, 3 MPa, a feed gas flow rate of 15 mL / min, and a reaction time of 10 h. The conversion and product selectivity or distribution are shown in Table 2.

[0099] Table 2 Catalytic performance of different catalysts for CO2 hydrogenation

[0100]

[0101] The results in Table 2 show that the CO2 conversion and ethanol selectivity of the diatomic catalyst not encapsulated in a membrane reactor were low after 10 hours of reaction. However, the stability of the diatomic catalyst encapsulated in a membrane reactor with a weaker hydrophobicity (methyltrimethoxysilane) was improved, indicating that the hydrophobic membrane reactor has a strong stabilizing effect on the diatomic sites. Comparison of the supported catalysts (Ce@Si and Ce@Si-C3) encapsulated in a membrane reactor and unencapsulated in a membrane reactor shows that there is no ethanol in the product, indicating that the ethanol production does not originate from hydrophobic organic molecules.

[0102] In addition, the catalyst after the reaction in Comparative Example 2 was taken out and tested. The results showed that the catalyst after the reaction no longer had a diatomic loading morphology, but was in a granular state.

[0103] The above embodiments of the present invention are merely examples for the purpose of illustrating the present invention and are not intended to limit the present invention. Persons skilled in the art will readily appreciate that various modifications or variations can be made based on the above description. It is not possible to enumerate all possible implementations here. Therefore, the scope of protection of the present invention shall be determined by the claims.

Claims

1. A method for preparing a high-stability catalyst for catalytic CO2 hydrogenation to ethanol, characterized in that: The steps include: (1) dissolving the carrier precursor in a medium, adding a complexing agent to carry out a coordination reaction to generate an organic metal framework material, and after the reaction is completed, filtering and collecting the solid, and drying to obtain a solid N-MOFs carrier; (2) dispersing the N-MOFs support in an organic solvent to obtain a suspension, then adding a metal precursor to the suspension, stirring, centrifuging, and drying to obtain a solid M@N-MOFs material; (3) dispersing the M@N-MOFs material in an ethanol aqueous solution of a surfactant, adding ammonia water and stirring, then adding ethyl orthosilicate to react, stirring, filtering, collecting the solid, and drying to obtain the M@N-MOFs@SiO2 material; and then calcining to obtain the MN@Si material; (4) The MN@Si material is dispersed in a solvent, an organic hydrophobic agent is added for surface modification, and the mixture is stirred. After the mixture is centrifuged, the solid is collected, and dried to obtain a highly stable catalyst for catalyzing CO2 hydrogenation to ethanol, which is referred to as MN@Si-R catalyst. The carrier precursor in step (1) is one or more of cerium salt, zirconium salt, indium salt, zinc salt, iron salt, cobalt salt, titanium salt, vanadium salt, chromium salt and manganese salt; the complexing agent is one or more of 2-methylimidazole, terephthalic acid, trimesic acid and 2-aminoterephthalic acid; The metal precursor in step (2) is a soluble compound of one or more of palladium, iridium, ruthenium, platinum, rhodium, copper, gold, silver, cobalt and nickel.

2. The method according to claim 1, characterized in that The carrier precursor in step (1) is one or more of cerium salt, zirconium salt, indium salt, zinc salt, iron salt, cobalt salt, titanium salt, vanadium salt, chromium salt and manganese salt; wherein the salt includes any one or more of nitrate, hydrochloride and sulfate; the molar ratio of the carrier precursor to the complexing agent is (0.05-20):

1.

3. The method according to claim 1, characterized in that In step (2), the mass ratio of the metal precursor to the N-MOFs carrier is (0.0005-0.5):

1.

4. The method according to claim 1, wherein The volume ratio of water to ethanol in the ethanol aqueous solution of the surfactant in step (3) is (0.1-20):1; the concentration of the surfactant relative to the ethanol aqueous solution is 1-10 g / L; the surfactant is one or more of hexadecyl ammonium bromide, hexadecyl ammonium bromide, hexadecyl ammonium bromide, and hexadecyl ammonium bromide; the mass ratio of the surfactant to the M@N-MOFs is 1:

1.

5. The method according to claim 1, characterized in that In step (3), the volume ratio of ammonia water to tetraethyl orthosilicate is 1:1; the volume mass ratio of tetraethyl orthosilicate to M@N-MOFs material is 0.1-10 mL / g; the calcination temperature is 400° C. and the calcination time is 4 h.

6. The method according to claim 1, characterized in that The solvent in step (4) is one of N,N-dimethylformamide, toluene, methanol, and ethanol; the mass ratio of the organic hydrophobic agent to the MN@Si material is (0.05-50):1; the organic hydrophobic agent includes one or more of trimethylchlorosilane, methyltrimethoxysilane, propyltrimethoxysilane, trimethyloxyphenylsilane and hexadecyltrimethoxysilane.

7. The method according to claim 1, characterized in that In step (4), the mass ratio of the organic hydrophobic agent to the MN@Si material is 1:

1.

8. A highly stable catalyst for catalytic CO2 hydrogenation to ethanol prepared by the method according to any one of claims 1 to 7.

9. A high-stability catalyst for catalyzing CO2 hydrogenation to ethanol according to claim 8, characterized in that: The metal active components in the catalyst are highly dispersed on the carrier in a sub-nano cluster configuration with an atomic number of 2-10; the content of the active components in the catalyst accounts for 0.01% to 5% of the total mass of the catalyst; the active components and the carrier are encapsulated in a SiO2 nano-membrane reactor with a hydrophobic surface.

10. A method for preparing ethanol by hydrogenating CO2, characterized in that: In the method, the catalyst according to claim 8 or 9 is used as a hydrogenation catalyst.

11. The method according to claim 10, characterized in that The method comprises the following steps: introducing CO2 / H2 synthesis gas into a catalyst for producing ethanol by hydrogenating CO2, and carrying out a reaction of producing ethanol by hydrogenating CO2 in a fixed bed; the catalyst does not require activation pretreatment before use; and the reaction conditions for producing ethanol by hydrogenating CO2 are: CO2:H2=1:3-4, a reaction temperature of 150-400°C, a reaction pressure of 0.1-5MPa, and a feed gas flow rate of 5-200mL / min.

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