A catalyst for carbon dioxide hydrogenation to methanol and a preparation method thereof

Abstract

The application belongs to the technical field of catalysts, and provides a catalyst for preparing methanol from carbon dioxide hydrogenation and a preparation method thereof. First, indium nitrate and zirconyl nitrate hydrate are added to citric acid, CTAB and PVP as metal precursors to obtain an In2O3-ZrO2 composite with high thermal stability and Lewis acid sites through hydrothermal treatment and calcination. Second, the In2O3-ZrO2 composite is combined with MOF and carbonized to obtain a C-MOF@In2O3-ZrO2 composite. Third, the C-MOF@In2O3-ZrO2 composite is mixed with an ionic liquid and heated and then rapidly cooled to obtain an IL@C-MOF@In2O3-ZrO2 composite. Fourth, the IL@C-MOF@In2O3-ZrO2 composite is subjected to weak reduction treatment in an H2 / Ar atmosphere to introduce additional oxygen vacancies, thereby obtaining the catalyst for preparing methanol from carbon dioxide hydrogenation.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of catalysts, and relates to a catalyst for preparing methanol by hydrogenating carbon dioxide and a preparation method thereof. BACKGROUND

[0002] The increasing global CO2 emissions have led to the gradual prominence of climate change issues, and at present, the society has reached a broad consensus on controlling carbon emissions, and it is urgent to reduce carbon. Among various carbon emission reduction technology routes, the conversion of CO2 into fuels or high-value chemicals represented by methanol through CO2 chemical utilization is one of the most promising approaches. At present, the most important method is to use CO2 and hydrogen as raw materials, and to produce methanol and water as products through a solid catalyst under certain reaction conditions by a thermal catalytic process. Among them, the performance of the catalyst is the core, which directly affects the conversion rate of CO2.

[0003] At present, there are four types of catalysts for preparing methanol by hydrogenating CO2: (1) copper-based catalysts, copper-based composite oxides represented by Cu / ZnO / Al2O3 have high conversion rate in the field of CO2 methanol production, but the selectivity of methanol is relatively low due to the presence of many by-products, and the stability is also poor due to the poor water resistance of copper under reaction conditions; (2) indium-based catalysts, a type of metal / metal oxide catalyst based on indium oxide, which has high methanol selectivity, but has the problem of low total yield; (3) composite oxides, composite oxide / solid solution catalysts represented by ZnO / ZrO2, which have the highest reaction temperature and pressure required to achieve the same CO2 conversion rate and methanol yield due to the absence of metal active sites, and high energy consumption; (4) noble metal catalysts, catalysts with active components such as Pd, Ru, and Pt, which have the highest CO2 conversion rate and methanol yield, but the cost is much higher than that of other catalysts, which is not conducive to large-scale application. Compared with other catalysts, indium oxide-based catalysts have the characteristics of high methanol selectivity, moderate reaction conditions, and low cost, but the current indium oxide-based catalysts have the problems of low CO2 conversion rate and easy sintering of active metals. SUMMARY

[0004] In view of the deficiencies of the prior art, the purpose of the present application is to provide a catalyst for carbon dioxide hydrogenation to methanol and a preparation method thereof. First, In2O3 and ZrO2 are combined to provide oxygen vacancies by In2O3 and Lewis acidity by ZrO2, to realize the synergistic effect of adsorption, activation of CO2 and stability of intermediates. Second, MOF is grown on the surface of the oxide, and porous carbon-based material is generated by high-temperature carbonization. The carbon-based framework not only improves the specific surface area and porosity of the catalyst, but also enhances the thermal stability and mechanical strength of the catalyst by limiting the agglomeration behavior of the oxide particles. The surface electronic structure and Lewis acid-base properties are optimized by functionalizing the composite with 1-butyl-3-methylimidazole acetate, and the catalyst interface stability and deactivation resistance are enhanced, thereby meeting the needs of actual production.

[0005] To achieve this purpose, the present application adopts the following technical solutions:

[0006] In a first aspect, the present application provides a preparation method of a catalyst for carbon dioxide hydrogenation to methanol, which is:

[0007] S1, dispersing indium nitrate hydrate in deionized water to prepare an indium nitrate solution, dispersing zirconyl nitrate hydrate in deionized water to prepare a zirconium salt solution, adding citric acid to the indium nitrate solution, stirring and dissolving, then adding CTAB solution and PVP solution, mixing uniformly, then adding the zirconium salt solution, adjusting the pH to 7 with sodium hydroxide solution, then transferring to a polytetrafluoroethylene-lined hydrothermal reactor, hydrothermal reaction at a first temperature, centrifugal washing and drying to obtain a precipitate, transferring the precipitate to a muffle furnace, heating to a second temperature under air atmosphere, calcining to obtain an In2O3-ZrO2 composite;

[0008] S2, adding zinc nitrate solution to 2-methylimidazole solution, stirring uniformly, adjusting the pH to 8 with sodium hydroxide solution to obtain a MOF precursor solution, dispersing the In2O3-ZrO2 composite in the MOF precursor solution, ultrasonic oscillation, then transferring to a polytetrafluoroethylene-lined hydrothermal reactor, hydrothermal reaction at a second temperature, washing and drying to obtain a MOF@In2O3-ZrO2 composite, placing the dried MOF@In2O3-ZrO2 composite in a tube furnace under argon atmosphere, heating to a third temperature for calcination to obtain a C-MOF@In2O3-ZrO2 composite;

[0009] S3, adding the C-MOF@In2O3-ZrO2 composite into the 1-butyl-3-methylimidazolium acetate solution, ultrasonic dispersion, standing at a fourth temperature, vacuum distillation, vacuum drying to obtain a non-cured C-MOF@In2O3-ZrO2 composite, placing the non-cured C-MOF@In2O3-ZrO2 composite in a tube furnace, heating to a fifth temperature under an argon atmosphere, after the holding, turning off the heating and continuously introducing argon to rapidly reduce the product to room temperature, to obtain an IL@C-MOF@In2O3-ZrO2 composite;

[0010] S4, heating the IL@C-MOF@In2O3-ZrO2 composite in a tube furnace under an H2 / Ar atmosphere to a sixth temperature, after holding to obtain a reduced IL@C-MOF@In2O3-ZrO2 composite;

[0011] S5, mixing the reduced IL@C-MOF@In2O3-ZrO2 composite with an inorganic binder and then adding a silica sol, drying after extrusion under an argon atmosphere to obtain a catalyst for carbon dioxide hydrogenation to methanol.

[0012] Indium nitrate and zirconyl nitrate are completely dissociated in water to form In 3+ and ZrO 2+ ions, the unique electronic structure of In 3+ and ZrO 2+ ions provides good chemical reactivity for subsequent reactions, In 3+ is a high oxidation state ion of indium, because its 5s orbital is completely empty, In 3+ has strong electron acceptor ability, so it shows strong Lewis acidity (electron pair accepting ability), and the Lewis acidity makes In 3+ can form a coordination bond with the oxygen atom in the CO2 molecule, especially through the shift of the electron cloud of the C=O bond of CO2, inducing the activation of CO2, the activated CO2 molecule is converted from a linear structure to a bent form, the electron density on the C atom is reduced, showing stronger electrophilicity, thereby promoting the chemical reaction with H2 or intermediates (such as H- or H + ). In the unactivated state, CO2 is a linear molecule, the carbon atom and the two oxygen atoms in the center of the molecule are connected by a double bond, the molecular structure is linear, and the chemical inertness of CO2 mainly comes from its molecular symmetry and the strong polarization force of the C=O bond, resulting in the need for external activation to reduce the reaction energy barrier of the molecule, In 3+ is a strong Lewis acidic metal ion, which lacks valence shell electrons, so it has strong electron accepting ability, when the CO2 molecule is close to In 3+ , the oxygen atom (with a lone pair of electrons) of CO2 will form a coordination bond with In 3+form coordination, due to the lone pair of electrons on the oxygen atom and the empty orbital of In 3+ , the electron distribution of the CO2 molecule changes, and the electron cloud density of the π bond in the C=O bond of the CO2 molecule is partially biased towards the oxygen atom. This electron cloud asymmetry is further amplified under the action of the Lewis acid, and the In 3+ , by coordinating with one or two oxygen atoms, the electron density of the C=O bond is further biased towards the oxygen atom, resulting in a decrease in the electron density on the C atom, showing stronger electrophilicity, and the electron cloud on the O atom is more biased towards the In 3+ , making the O atom exhibit stronger nucleophilicity, and after the CO2 molecule coordinates with the In 3+ , its adsorption energy is significantly reduced, and the molecule is more easily fixed on the catalyst surface, providing sufficient time and space for subsequent reactions.

[0013] In In2O3 crystals, due to the lattice structure of the oxide, some oxygen atoms may be missing, forming oxygen vacancies. The presence of oxygen vacancies enhances the electronic density of the surface and further enhances the adsorption and activation ability of CO2. Oxygen vacancies provide an electron-rich environment, polarize the C=O bond of the CO2 molecule, and reduce its chemical inertness. In 3+ , the Lewis acid sites on the surface can stabilize reaction intermediates (such as HCOO - , H2CO), thereby reducing the reaction energy barrier. After C O2 is adsorbed and activated, it reacts with H2 to form formate intermediate (HCOO - ), HCOO - is further converted into formaldehyde and methanol, and In 3+ , the Lewis acidity stabilizes these intermediates by coordinating with oxygen atoms, preventing their premature dissociation. In the composite oxide In2O3-ZrO2, the introduction of ZrO2 can improve the stability of the overall lattice, preventing the crystal structure from sintering or deactivating under high-temperature reaction conditions. This is because the high melting point and strong oxide bond (Zr-O bond) of ZrO2 can effectively disperse In2O3 particles, preventing their agglomeration; ZrO2 3+ , the Lewis acid sites on the surface of ZrO2 can adsorb the oxygen atoms of CO2, while the In 3+ , sites interact with the C atom to form a bifunctional activation center, improving the activation efficiency of CO2.

[0014] ZrO2 is a typical Lewis acid oxide, and its surface Lewis acid sites mainly come from exposed Zr 4+ ions, Zr 4+The ions have a high positive charge density and exhibit strong electron acceptor ability. 4+ Ions tend to accept electrons, and their surfaces can interact electrostatically or coordinate with electron-rich molecules (such as the oxygen atoms of CO2). When the CO2 molecule approaches the ZrO2 surface, the lone pair of electrons on the oxygen atom will interact with the ZrO2 surface. 4+ Coordination, forming electrostatic interactions or coordination bonds, is Zr 4+ The adsorbed CO2 molecule will become more electrophilic due to the electron cloud shift of the oxygen atom, and the CO2 molecule will be partially activated. 4+ Different, In 3+ It is more inclined to interact with the C atom of CO2 molecule because the C atom of CO2 acts as an electrophilic center in the molecule. 4+ Based on the site adsorption of CO2, In 3+ The sites can further interact with the C atoms of CO2, and the electron cloud density on the C atoms is 4+ has been reduced under the action of 3+ By directly coordinating with C atoms, the electrophilicity of C atoms is further enhanced. In the composite material In2O3-ZrO2, In2O3 and ZrO2 form a unique interface, which provides an ideal environment for the dual-functional activation of CO2. 4+ The site is responsible for adsorbing the oxygen atom of CO2, while shifting the C=O bond electron cloud toward the oxygen atom, enhancing the electrophilicity of the C atom. 3+ The sites interact directly with C atoms, further reducing the electron cloud density of C atoms through Lewis acidity, reducing the chemical inertness of CO2, and ZrO2 can effectively stabilize the reaction intermediates, especially through the hydrogen bonding provided by the oxygen atoms on its surface, thereby avoiding the dissociation of the intermediates during the reaction. The high chemical stability and dispersion of ZrO2 further improve the activity and life of the catalyst.

[0015] Citric acid contains three carboxyl groups and one alcoholic hydroxyl group. Upon addition, the carboxyl groups of citric acid coordinate with metal cations to form stable chelates. This process effectively prevents premature hydrolysis or precipitation of the metal ions and reduces the possibility of particle agglomeration through uniform intermolecular distribution. The addition of citric acid regulates the distribution of metal ions, helping to form a uniform composite oxide structure, thereby increasing the number and uniformity of active sites in the catalyst. The decomposition products of citric acid (such as CO2 and water) do not introduce impurities during the calcination process, thus ensuring the purity and high specific surface area of ​​the catalyst. CTAB is a cationic surfactant whose hydrophilic head can electrostatically interact with metal ions, while the hydrophobic tail (long-chain alkyl) limits excessive particle growth through steric hindrance. PVP forms a weak coordination bond with the metal ions through the carbonyl group in the molecule, forming a stable protective layer on the surface of the nanoparticles. The synergistic effect of CTAB and PVP can control the particle morphology and size of In2O3-ZrO2, resulting in a composite oxide with a large specific surface area. This helps to increase the active sites exposed by the catalyst, and the stabilization effect of PVP further reduces particle agglomeration and maintains the high efficiency of the catalyst. 3+ and ZrO 2+ The ions form separate precipitates, and co-precipitation during this process results in a highly uniform distribution of the two metal hydroxides. This co-precipitation process ensures strong interactions between In2O3 and ZrO2, forming uniform phase interfaces. These interfaces enhance the activation of CO2 and increase the efficiency of H2 dissociation. The introduction of ZrO2 improves the composite oxide's sintering resistance, thereby extending the catalyst's service life.

[0016] In solution, Zn 2+ ions and 2-methylimidazole form a metal organic framework (MOF) through coordination. 3+ It exhibits strong Lewis acidity and is therefore very easy to accept lone pair electrons from ligands (such as 2-methylimidazole). 3+ The strong electron-accepting ability of Zr enables it to form a coordination bond with the lone pair electrons of the nitrogen atom in 2-methylimidazole, thereby adsorbing organic ligands on the surface; 4+ It also acts as a Lewis acid site, which can react with the nitrogen atom in 2-methylimidazole or Zn 2+ Electrostatic or coordination interactions occur, and on the surface of In2O3-ZrO2, hydroxyl groups and oxygen vacancies behave as Lewis acid-base pairs. The surface hydroxyl groups help to regulate the surface charge distribution and can enhance the adsorption effect through hydrogen bonding with 2-methylimidazole. When In2O3-ZrO2 is dispersed in the MOF precursor solution, Zn 2+ It is the central ion of MOF. When it is close to the surface of In2O3-ZrO2, it will be attracted by the Lewis acid sites (In3+ and Zr 4+ ) or oxygen vacancy adsorption, Zn 2+ 's positive charge is attracted to the negative charge of the oxygen vacancy or surface hydroxyl group, or to the oxygen atom of the surface hydroxyl group or In 3+ / Zr 4+ coordination, forming a stable adsorption state on the oxide surface, the particle surface of In2O3-ZrO2 acts as a template, allowing the nucleation and growth process of MOF to gradually cover the particle surface, ultimately forming a MOF-coated composite structure (MOF@In2O3-ZrO2). This coating not only improves the dispersion of In2O3-ZrO2, but also increases the specific surface area and pore structure of the composite. The MOF shell provides physical isolation for In2O3-ZrO2, preventing particle agglomeration and thus maintaining the high specific surface area and dispersion of the composite. The porous structure of MOF allows free diffusion of reactant molecules (such as CO2 and H2) to the active center, while preventing the intrusion of large molecules or impurities, thereby improving the selectivity and durability of the catalyst.

[0017] The metal nodes Zn 2+ of MOF exhibit Lewis acidity, Zn 2+ 's acidic sites can interact with molecules with lone pairs of electrons (such as the oxygen atoms of CO2 or the dissociation products H - of H2), in the structure of MOF, some Zn 2+ ions may be exposed on the framework surface due to incomplete coordination, these coordination unsaturated Zn 2+ are strong Lewis acidic sites that can adsorb and activate CO2, the porous structure of MOF allows closer contact between adsorbed molecules and Lewis acidic sites (such as Zn 2+ ), thereby enhancing adsorption and activation. At the interface between MOF and In2O3-ZrO2, the adsorption and activation of CO2 are synergized by the bifunctional sites, MOF's Zn 2+ sites interact with the oxygen atoms (nucleophilic centers) of CO2 through Lewis acidity, adsorbing CO2 and polarizing the molecule, Zn 2+ sites can induce electron redistribution in the CO2 molecule, causing the electron cloud of the C=O bond to shift towards the oxygen atom, enhancing the electrophilicity of the C atom, the C atom (electrophilic center) of the CO2 molecule interacts with In 3+ or oxygen vacancies on the surface of In2O3-ZrO2, further polarizing or activating the C=O bond of CO2, Zr 4+ sites can further reduce the symmetry of the molecule and enhance its chemical reactivity by coordinating with the oxygen atoms of CO2, MOF's Zn 2+ sites and In 3+The active sites of MOF and In2O3-ZrO2 can act on the oxygen atom and carbon atom of CO2 (bifunctional activation) to improve its reactivity. In the CO2 hydrogenation reaction, the activation of H2 is another key step, and the synergistic effect of MOF and In2O3-ZrO2 can also promote the adsorption and dissociation of H2. The pore structure of MOF can capture H2 molecules, and the Lewis acidity of Zn 2+ sites can adsorb H2. The Zn 2+ sites may induce weak polarization of H2, reducing its dissociation energy barrier; the surface oxygen vacancies of In2O3-ZrO2 are the main active sites for H2. H2 molecules dissociate at the oxygen vacancies to generate active hydrogen species, and the Zn 2+ sites of MOF can capture and guide H2 molecules to the oxygen vacancies of In2O3-ZrO2, thereby promoting the dissociation of H2. This interface synergistic effect improves the activation efficiency of H2. In the CO2 hydrogenation reaction, the adsorption and stability of intermediates have an important influence on the reaction path and product selectivity, and the interface effect of MOF and In2O3-ZrO2 can improve the stability of intermediates. The pore structure of MOF can capture HCOO - and CH2O, and the Lewis acidity of Zn 2+ sites can stabilize these intermediates, and the Zn 2+ sites can also prevent the premature dissociation of intermediates to avoid the formation of by-products (such as CO). The surface sites of In2O3-ZrO2 (such as In 3+ and Zr 4+ ) can further stabilize the intermediates. HCOO - can coordinate with Zr 4+ through its oxygen atom, thereby reducing its reaction energy barrier, and CH2O can interact with In 3+ through its carbonyl group to prevent its dissociation into CO. The organic framework will partially decompose into carbon material (C-MOF) during subsequent calcination, which can further improve the electrical conductivity and surface activity of the catalyst.

[0018] 1-Butyl-3-methylimidazolium acetate is a typical ionic liquid, and the 1-butyl-3-methylimidazolium cation has a hydrophobic butyl side chain and an electron-rich imidazole ring. The imidazole ring is a five-membered aromatic ring composed of two nitrogen atoms and three carbon atoms. The nitrogen atom has a lone pair of electrons, which has strong nucleophilicity due to the high electronegativity of nitrogen. The lone pair of electrons can coordinate with Lewis acidic centers (such as In 3+ and Zr 4+ ). The Lewis acidic sites on the surface of C-MOF@In2O3-ZrO2 tend to interact with lone pair electrons with high electron cloud density to form coordination bonds. The nitrogen atom lone pair electrons in the imidazole ring can coordinate with In 3+ or Zr 4+Coordination occurs, the lone pair of electrons of pyridine type nitrogen is transferred to In 3+ or Zr 4+ empty orbital through coordination bond, forming stable Lewis acid-base coordination complex, this coordination further stabilizes the adsorption of imidazole ring on the surface of C-MOF@In2O3-ZrO2 by reducing the positive charge density of Lewis acid center. The butyl side chain is composed of non-polar C-H bond, and its electron cloud distribution is relatively uniform, so it shows hydrophobicity. The hydrophobicity of the butyl side chain makes it tend to interact with other non-polar or weakly polar surfaces (such as graphitic surface). The graphitic surface is the surface of carbon material formed during the carbonization of C-MOF. The non-polar characteristics of the graphitic surface make it easy to interact with other non-polar molecules (such as butyl side chain). The non-polar C-H bond of the butyl side chain weakly interacts with the graphitic surface through van der Waals force, enhancing its adsorption on C-MOF@In2O3-ZrO2. This synergistic effect enables 1-butyl-3-methyl imidazole ionic liquid to be firmly adsorbed on the surface of C-MOF@In2O3-ZrO2, forming a stable coating or interface. The carboxyl group of acetate anion can interact with the hydroxyl (-OH) or oxygen vacancy adsorbed on the surface of carbon material through hydrogen bond or electrostatic interaction, and can also coordinate with the unsaturated metal sites (such as In 3+ , Zr 4+ ) on the surface, thereby stabilizing the attachment of ionic liquid on the surface.

[0019] The C-MOF@In2O3-ZrO2 composite is heated to 180-200°C under an argon atmosphere, and this process accelerates the formation of oxygen vacancies through thermal induction. High temperature promotes the desorption of surface oxygen atoms of the oxide as gaseous oxygen molecules. This oxygen vacancy generation improves the surface activity of the material, especially the adsorption and activation capacity for molecules such as CO2 and H2. At high temperatures, the In2O3 and ZrO2 lattices can form metastable structures (such as high-temperature-induced lattice distortion, incomplete crystallization regions, etc.). These metastable structures have higher free energy. After the heating and holding under an argon atmosphere, the material is subjected to rapid cooling (quenching), that is, the heating is turned off and argon is continuously supplied to rapidly cool the composite material to room temperature. This operation realizes the preservation of oxygen vacancies and metastable structures through the following mechanisms. During the conventional cooling process, oxygen vacancies can be refilled with oxygen from the environment or lattice oxygen in the oxide. Oxygen molecules are re-adsorbed to the surface and fill the oxygen vacancies or the oxygen atoms in the lattice migrate to the vacancy positions to repair defects, reducing the oxygen vacancy concentration of the material, thereby weakening the surface activity and the adsorption capacity for CO2 molecules. Rapid cooling inhibits the diffusion of oxygen molecules and the surface chemical reaction rate by rapidly reducing the temperature, preventing oxygen vacancies from being refilled. The argon atmosphere further prevents the participation of environmental oxygen, ensuring that the oxygen vacancy concentration is preserved. During the slow cooling process, atoms or ions in the lattice will diffuse and rearrange on a long time scale, eventually tending towards a thermodynamic stable state. The metastable structures formed at high temperatures (such as distorted metal oxide lattices and irregular interface structures) can be reorganized or repaired during this process. The rapid cooling operation significantly shortens the cooling time, and the metastable structures are preserved, thereby improving the catalytic performance.

[0020] Hydrogen is a commonly used reducing agent. Hydrogen molecules dissociate into active hydrogen atoms at high temperatures, which then combine with oxygen atoms on the surface of the oxide to form water molecules, causing the desorption of oxygen atoms to form oxygen vacancies. The formation of oxygen vacancies increases the active sites on the surface of the composite material, which can adsorb and activate reaction molecules to enhance the catalytic performance. The reduction treatment temperature of 150-160°C belongs to weak reduction conditions, which can generate an appropriate amount of oxygen vacancies without causing serious damage to the material structure. In the H2 atmosphere, part of the In 3+ in In2O3 is reduced to In + , In 3+ exhibits strong Lewis acidity (due to high positive charge density), and In + exhibits weaker Lewis acidity. Compared with In 3+ , In + has a significantly reduced charge density, but at the same time has higher polarization ability and stronger reducing property; hydrogen can also reduce part of the Zr 4+ in ZrO2 to Zr 3+ , and Zr 3+The unsaturated electronic state of the imidazole ring can act as Lewis acidic sites, enhancing the adsorption and stabilization of reaction intermediates (such as HCOO - , CH2O) in the reaction. Under the reduction conditions of 150-160℃, the cation [BMIM] + and anion [Ac] - of the ionic liquid do not decompose, but can be further optimized by heating to improve the binding with the oxide surface. The lone pair electrons of the imidazole ring can form stronger coordination with the newly generated oxygen vacancies or partially reduced metal centers (such as In + or Zr 3+ ). The hydrogen reduction treatment can further adjust the electronic structure of the ionic liquid layer at the oxide interface, making it more capable of adsorbing and activating reaction molecules, ultimately improving the performance of the catalytic reaction.

[0021] As a preferred technical solution of the present application, in step S1, the concentration of the indium nitrate solution is 0.2M.

[0022] In some alternative embodiments, the concentration of the zirconium salt solution is 0.1M.

[0023] In some alternative embodiments, the molar ratio of citric acid to indium nitrate hydrate is 1:1.

[0024] In some alternative embodiments, the concentration of the CTAB solution is 0.01M.

[0025] In some alternative embodiments, the concentration of the PVP solution is 0.01M.

[0026] In some alternative embodiments, the volume ratio of the indium nitrate solution, zirconium salt solution, CTAB solution, and PVP solution is 10:10:1:1.

[0027] In some alternative examples, the first temperature is 120-130℃, for example, it can be 120.0℃, 121.0℃, 122.0℃, 123.0℃, 124.0℃, 125.0℃, 126.0℃, 127.0℃, 128.0℃, 129.0℃, or 130.0℃, but not limited to the listed values, other unlisted values within this range are also applicable.

[0028] In some alternative examples, the first temperature hydrothermal reaction time is 14-16h, for example, it can be 14.0h, 14.2h, 14.4h, 14.6h, 14.8h, 15.0h, 15.2h, 15.4h, 15.6h, 15.8h, or 16.0h, but not limited to the listed values, other unlisted values within this range are also applicable.

[0029] In some optional examples, the second temperature is 300-400℃, for example, it can be 300.0℃, 310.0℃, 320.0℃, 330.0℃, 340.0℃, 350.0℃, 360.0℃, 370.0℃, 380.0℃, 390.0℃ or 400.0℃, but not limited to the listed values, other values in the range are also applicable.

[0030] In some optional examples, the heating rate of the second temperature is 2-5℃ / min, for example, it can be 2.0℃ / min, 2.3℃ / min, 2.6℃ / min, 2.9℃ / min, 3.2℃ / min, 3.5℃ / min, 3.8℃ / min, 4.1℃ / min, 4.4℃ / min, 4.7℃ / min or 5.0℃ / min, but not limited to the listed values, other values in the range are also applicable.

[0031] In some optional examples, the calcination time of the second temperature is 3-5h, for example, it can be 3.0h, 3.2h, 3.4h, 3.6h, 3.8h, 4.0h, 4.2h, 4.4h, 4.6h, 4.8h or 5.0h, but not limited to the listed values, other values in the range are also applicable.

[0032] As a preferred technical solution of the present application, in step S2, the concentration of the zinc nitrate solution is 0.1M.

[0033] In some optional examples, the concentration of the 2-methylimidazole solution is 0.5M.

[0034] In some optional examples, the volume ratio of the zinc nitrate solution to the 2-methylimidazole solution is 1:1.

[0035] In some optional examples, the mass-volume ratio of the In2O3-ZrO2 composite to the zinc nitrate solution is 1g:10mL.

[0036] In some optional examples, the second temperature is 90-100℃, for example, it can be 90.0℃, 91.0℃, 92.0℃, 93.0℃, 94.0℃, 95.0℃, 96.0℃, 97.0℃, 98.0℃, 99.0℃ or 100.0℃, but not limited to the listed values, other values in the range are also applicable.

[0037] In some optional examples, the hydrothermal reaction time at the second temperature is 8-10h, for example, it can be 8.0h, 8.2h, 8.4h, 8.6h, 8.8h, 9.0h, 9.2h, 9.4h, 9.6h, 9.8h or 10.0h, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0038] In some optional examples, the third temperature is 400-500°C, for example, it can be 400.0°C, 410.0°C, 420.0°C, 430.0°C, 440.0°C, 450.0°C, 460.0°C, 470.0°C, 480.0°C, 490.0°C or 500.0°C, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0039] In some optional examples, the heating rate of the third temperature is 2-5°C / min, for example, it can be 2.0°C / min, 2.3°C / min, 2.6°C / min, 2.9°C / min, 3.2°C / min, 3.5°C / min, 3.8°C / min, 4.1°C / min, 4.4°C / min, 4.7°C / min or 5.0°C / min, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0040] In some optional examples, the calcination time is 2-3h, for example, it can be 2.0h, 2.1h, 2.2h, 2.3h, 2.4h, 2.5h, 2.6h, 2.7h, 2.8h, 2.9h or 3.0h, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0041] As a preferred technical solution of the present invention, in step S3, the concentration of the 1-butyl-3-methylimidazolium acetate solution is 0.1 M, and the solvent is ethanol.

[0042] In some optional examples, the mass volume ratio of the C-MOF@In2O3-ZrO2 complex to the 1-butyl-3-methylimidazolium acetate solution is 1 g:30 mL.

[0043] In some optional examples, the ultrasonic dispersion time is 20-30 min, for example, it can be 20.0 min, 21.0 min, 22.0 min, 23.0 min, 24.0 min, 25.0 min, 26.0 min, 27.0 min, 28.0 min, 29.0 min or 30.0 min, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0044] In some optional examples, the fourth temperature is 50-60℃, for example, can be 50.0℃, 51.0℃, 52.0℃, 53.0℃, 54.0℃, 55.0℃, 56.0℃, 57.0℃, 58.0℃, 59.0℃ or 60.0℃, but not only limited to the listed values, other values in the range are also applicable.

[0045] In some optional examples, the standing time is 6-8h, for example, can be 6.0h, 6.2h, 6.4h, 6.6h, 6.8h, 7.0h, 7.2h, 7.4h, 7.6h, 7.8h or 8.0h, but not only limited to the listed values, other values in the range are also applicable.

[0046] In some optional examples, the fifth temperature is 180-200℃, for example, can be 180℃, 182℃, 184℃, 186℃, 188℃, 190℃, 192℃, 194℃, 196℃, 198℃ or 200℃, but not only limited to the listed values, other values in the range are also applicable.

[0047] In some optional examples, the holding time of the fifth temperature is 30-40min, for example, can be 30min, 31min, 32min, 33min, 34min, 35min, 36min, 37min, 38min, 39min or 40min, but not only limited to the listed values, other values in the range are also applicable.

[0048] As a preferred technical solution of the present application, in step S4, the volume ratio of H2 in H2 / Ar is 5-7%, for example, can be 5.0%, 5.2%, 5.4%, 5.6%, 5.8%, 6.0%, 6.2%, 6.4%, 6.6%, 6.8% or 7.0%, but not only limited to the listed values, other values in the range are also applicable.

[0049] In some optional examples, the sixth temperature is 150-160℃, for example, can be 150.0℃, 151.0℃, 152.0℃, 153.0℃, 154.0℃, 155.0℃, 156.0℃, 157.0℃, 158.0℃, 159.0℃ or 160.0℃, but not only limited to the listed values, other values in the range are also applicable.

[0050] In some optional examples, the holding time is 60-80 min, for example, it can be 60.0 min, 62.0 min, 64.0 min, 66.0 min, 68.0 min, 70.0 min, 72.0 min, 74.0 min, 76.0 min, 78.0 min or 80.0 min, but not limited to the listed values, and other values in the range are also applicable.

[0051] As a preferred technical solution of the present application, in step S5, the mass ratio of the reduced IL@C-MOF@In2O3-ZrO2 composite, the inorganic binder and the silica sol is 90:5:5.

[0052] In some optional examples, the inorganic binder is carbon fiber and graphite powder, and the mass ratio is 3:7.

[0053] In a second aspect, the present application provides a catalyst for carbon dioxide hydrogenation to methanol, which is prepared by the preparation method of the first aspect.

[0054] Compared with the prior art, the present application has the following beneficial effects:

[0055] (1) The oxygen vacancies in In2O3 can interact with CO2 molecules, activate CO2 molecules to reduce the bond dissociation energy of C=O, ZrO2 as a Lewis acidic material can provide additional Lewis acid sites to stabilize the reaction intermediates and improve the reaction efficiency of the CO2 hydrogenation conversion process, ZrO2 and In 3+ Synergistic effect at the interface of the composite oxide, enhance the adsorption and activation ability of CO2, form a bifunctional activation center, improve the activation efficiency of CO2, and the introduction of ZrO2 improves the thermal stability of the composite material, maintains the high activity of the catalyst under high temperature reaction conditions;

[0056] (2) The particle surface of In2O3-ZrO2 as a template forms MOF@In2O3-ZrO2, improves the dispersity of In2O3-ZrO2, and also increases the specific surface area and pore structure of the composite, and the porous structure of MOF allows the diffusion of reactant molecules to the active center, making the contact between the adsorbed molecules and the Lewis acid sites more intimate, thereby enhancing the adsorption and activation effect, and the subsequent calcination process will partially decompose to generate carbon material (C-MOF), which can further improve the electrical conductivity and surface activity of the catalyst;

[0057] (3) The composite is heated under an argon atmosphere to promote the formation of oxygen vacancies, improve the adsorption and activation capacity of molecules such as CO2 and H2, and at high temperatures, the In2O3 and ZrO2 lattices can form a metastable structure, so that the composite material is rapidly cooled to room temperature, realizing the retention of oxygen vacancies and metastable structures, and improving the catalytic performance;

[0058] (4) The composite material is subjected to weak reduction treatment, and in a H2 atmosphere, part of In 3+ of In2O3 is reduced to In + , and at the same time has higher polarization capacity and stronger reducibility, part of Zr 4+ in ZrO2 is reduced to Zr 3+ , enhancing the adsorption and stability of reaction intermediates, and the lone pair electrons of the imidazole ring of the ionic liquid can have stronger coordination with newly generated oxygen vacancies or partially reduced metal centers, having stronger adsorption and activation capacity of reaction molecules, and improving the catalytic reaction performance. BRIEF DESCRIPTION OF DRAWINGS

[0059] Figure 1 FIG. 1 is an SEM image of an In2O3-ZrO2 composite prepared in Example 1 of the present application;

[0060] Figure 2 FIG. 3 is an SEM image of a MOF@In2O3-ZrO2 composite prepared in Example 1 of the present application;

[0061] Figure 3 FIG. 4 is a TEM image of a MOF@In2O3-ZrO2 composite prepared in Example 1 of the present application. DETAILED DESCRIPTION

[0062] The technical solutions of the present application will be described in detail below with reference to specific examples and their accompanying drawings. The examples described herein are specific embodiments of the present application, which are used to illustrate the concept of the present application; these descriptions are all explanatory and exemplary, and should not be understood as limiting the embodiments of the present application and the protection scope of the present application. In addition to the examples described herein, those skilled in the art can also employ other technical solutions that are obvious based on the content disclosed in the claims and the specification of the present application, which include technical solutions that make any obvious substitutions and modifications to the examples described herein.

[0063] The chemical reagents used in the examples and comparative examples of the present application are all commercially available and have not been subjected to any further purification treatment.

[0064] Example 1

[0065] The present embodiment provides a preparation method of a catalyst for carbon dioxide hydrogenation to methanol, which specifically comprises the following steps:

[0066] S1, indium nitrate hydrate was dispersed in deionized water to prepare a 0.2M indium nitrate solution, and zirconium oxide nitrate hydrate was dispersed in deionized water to prepare a 0.1M zirconium salt solution, 4mmol of citric acid was added to 20mL of the indium nitrate solution, after stirring and dissolving, 2mL of 0.01M CTAB solution and 2mL of 0.01M PVP solution were added, after mixing evenly, 20mL of 0.1M zirconium salt solution was added, and the pH was adjusted to 7 using sodium hydroxide solution and then transferred to a polytetrafluoroethylene lined hydrothermal reactor, which was hydrothermally reacted at 120°C for 14.2h, and after centrifugal washing and drying, a precipitate was obtained, which was transferred to a muffle furnace, and heated to 320°C at a rate of 2°C / min under air atmosphere and calcined for 3.3h to obtain an In2O3-ZrO2 composite;

[0067] S2, 20mL of 0.1M zinc nitrate solution was added to 20mL of 0.5M 2-methylimidazole solution, after stirring evenly, a MOF precursor solution was obtained by adjusting the pH to 8 using sodium hydroxide solution, 2g of In2O3-ZrO2 composite was dispersed in the MOF precursor solution, and after ultrasonic oscillation, it was transferred to a polytetrafluoroethylene lined hydrothermal reactor, which was hydrothermally reacted at 91°C for 8.4h, and after washing and drying, a MOF@In2O3-ZrO2 composite was obtained, and the dried MOF@In2O3-ZrO2 composite was placed in a tube furnace under argon atmosphere, heated to 440°C at a rate of 2°C / min and calcined for 2.2h to obtain a C-MOF@In2O3-ZrO2 composite;

[0068] S3, 1g of C-MOF@In2O3-ZrO2 composite was added to 30mL of 0.1M 1-butyl-3-methylimidazole acetate solution, ultrasonic dispersed for 22min, and placed at 52°C for 6.3h, and after vacuum distillation and vacuum drying, an unsolidified C-MOF@In2O3-ZrO2 composite was obtained, which was placed in a tube furnace under argon atmosphere, heated to 183°C and kept for 31min, after the heat preservation was completed, the heating was turned off and argon was continuously introduced to quickly reduce the product to room temperature to obtain an IL@C-MOF@In2O3-ZrO2 composite;

[0069] S4, the IL@C-MOF@In2O3-ZrO2 composite was heated to 151°C in a tube furnace under H2(5%) / Ar atmosphere, and after keeping for 64min, a reduced IL@C-MOF@In2O3-ZrO2 composite was obtained;

[0070] S5, 90 g of reduced IL@C-MOF@In2O3-ZrO2 composite, 1.5 g of carbon fiber and 3.5 g of graphite powder were mixed, then 5 g of silica sol was added, and after extrusion, it was dried in an argon atmosphere to obtain a catalyst for the hydrogenation of carbon dioxide to methanol.

[0071] Figure 1 The SEM image of the In2O3-ZrO2 composite prepared in this example shows that the In2O3-ZrO2 composite particles are uniformly distributed and there is no obvious agglomeration phenomenon; Figure 2 The SEM image of the MOF@In2O3-ZrO2 composite prepared in this example shows that the In2O3-ZrO2 composite particles are uniformly distributed on the surface of the MOF; Figure 3 The TEM image of the MOF@In2O3-ZrO2 composite prepared in this example.

[0072] Example 2

[0073] The present example provides a preparation method of a catalyst for the hydrogenation of carbon dioxide to methanol, which specifically comprises the following steps:

[0074] S1, prepare a 0.2M indium nitrate solution by dispersing indium nitrate hydrate in deionized water, prepare a 0.1M zirconium salt solution by dispersing zirconyl nitrate hydrate in deionized water, add 4mmol of citric acid to 20mL of the indium nitrate solution, stir and dissolve, then add 2mL of 0.01M CTAB solution and 2mL of 0.01M PVP solution, mix uniformly, then add 20mL of 0.1M zirconium salt solution, adjust the pH to 7 using sodium hydroxide solution, and then transfer to a polytetrafluoroethylene-lined hydrothermal reactor, hydrothermal reaction at 125℃ for 14.8h, centrifugal washing and drying to obtain a precipitate, transfer the precipitate to a muffle furnace, heat to 390℃ at 4℃ / min under air atmosphere, and calcine for 4.7h to obtain an In2O3-ZrO2 composite;

[0075] S2, add 20mL of 0.1M zinc nitrate solution to 20mL of 0.5M 2-methylimidazole solution, stir uniformly, then adjust the pH to 8 using sodium hydroxide solution to obtain a MOF precursor solution, disperse 2g of In2O3-ZrO2 composite in the MOF precursor solution, ultrasonic oscillation, then transfer to a polytetrafluoroethylene-lined hydrothermal reactor, hydrothermal reaction at 98℃ for 8.9h, washing and drying to obtain a MOF@In2O3-ZrO2 composite, place the dried MOF@In2O3-ZrO2 composite in a tube furnace under argon atmosphere, heat to 410℃ at 5℃ / min, and calcine for 2.8h to obtain a C-MOF@In2O3-ZrO2 composite;

[0076] S3, 1 g of C-MOF@In2O3-ZrO2 composite was added to 30 mL of 0.1M 1-butyl-3-methylimidazolium acetate solution, ultrasonic dispersion for 29 min, standing at 59℃ for 7.4 h, vacuum distillation, vacuum drying to obtain unsolidified C-MOF@In2O3-ZrO2 composite, the unsolidified C-MOF@In2O3-ZrO2 composite was placed in a tube furnace, heated to 188℃ under argon atmosphere for 36 min, after the heat preservation was turned off and the argon was continuously introduced to make the product quickly reduce to room temperature, to obtain IL@C-MOF@In2O3-ZrO2 composite;

[0077] S4, the IL@C-MOF@In2O3-ZrO2 composite was heated to 158℃ in a tube furnace under H2(6%) / Ar atmosphere, and a reduced IL@C-MOF@In2O3-ZrO2 composite was obtained after 78 min of heat preservation;

[0078] S5, 90 g of reduced IL@C-MOF@In2O3-ZrO2 composite, 1.5 g of carbon fiber and 3.5 g of graphite powder were mixed, and then 5 g of silica sol was added, and after extrusion, it was dried under argon atmosphere to obtain a catalyst for the hydrogenation of carbon dioxide to methanol.

[0079] Example 3

[0080] The embodiment provides a preparation method of a catalyst for the hydrogenation of carbon dioxide to methanol, and specifically comprises the following steps:

[0081] S1, an indium nitrate hydrate was dispersed in deionized water to prepare a 0.2M indium nitrate solution, a zirconyl nitrate hydrate was dispersed in deionized water to prepare a 0.1M zirconium salt solution, 4 mmol of citric acid was added to 20 mL of the indium nitrate solution, after stirring and dissolving, 2 mL of 0.01M CTAB solution and 2 mL of 0.01M PVP solution were added, the mixture was uniformly mixed, 20 mL of 0.1M zirconium salt solution was added, sodium hydroxide solution was used to adjust the pH to 7, and then the mixture was transferred to a polytetrafluoroethylene-lined hydrothermal reactor, and hydrothermal reaction was carried out at 130℃ for 15.8 h, after centrifugal washing and drying, a precipitate was obtained, the precipitate was transferred to a muffle furnace, and the temperature was increased to 350℃ at a rate of 5℃ / min under air atmosphere, and calcination was carried out for 4.1 h to obtain an In2O3-ZrO2 composite;

[0082] S2, 20 mL of 0.1M zinc nitrate solution was added to 20 mL of 0.5M 2-methylimidazole solution, after stirring evenly, MOF precursor solution was obtained by adjusting pH to 8 using sodium hydroxide solution, 2g of In2O3-ZrO2 composite was dispersed in the MOF precursor solution, after ultrasonic oscillation, it was transferred to a polytetrafluoroethylene lined autoclave, hydrothermal reaction was carried out at 93℃ for 9.7h, after washing and drying, MOF@In2O3-ZrO2 composite was obtained, under argon atmosphere, the dried MOF@In2O3-ZrO2 composite was placed in a tube furnace, and was heated to 490℃ at a rate of 3℃ / min and calcined for 2.5h, to obtain C-MOF@In2O3-ZrO2 composite;

[0083] S3, 1g of C-MOF@In2O3-ZrO2 composite was added to 30 mL of 0.1M 1-butyl-3-methylimidazole acetate solution, ultrasonic dispersion was carried out for 26min, and it was placed at 56℃ for 7.8h, after vacuum distillation and vacuum drying, unsolidified C-MOF@In2O3-ZrO2 composite was obtained, the unsolidified C-MOF@In2O3-ZrO2 composite was placed in a tube furnace, heated to 196℃ under argon atmosphere, and kept for 39min, after the end of the heat preservation, the heating was turned off and argon was continuously introduced to rapidly reduce the product to room temperature, to obtain IL@C-MOF@In2O3-ZrO2 composite;

[0084] S4, IL@C-MOF@In2O3-ZrO2 composite was heated to 154℃ in a tube furnace under H2(7%) / Ar atmosphere, and after keeping for 73min, reduced IL@C-MOF@In2O3-ZrO2 composite was obtained;

[0085] S5, 90g of reduced IL@C-MOF@In2O3-ZrO2 composite, 1.5g of carbon fiber and 3.5g of graphite powder were mixed, and then 5g of silica sol was added, after extrusion, it was dried under argon atmosphere, to obtain a catalyst for hydrogenation of carbon dioxide to methanol.

[0086] Example 4

[0087] The embodiment provides a preparation method of a catalyst for hydrogenation of carbon dioxide to methanol, and specifically comprises the following steps:

[0088] S1, indium nitrate hydrate is dispersed in deionized water to prepare a 0.2M indium nitrate solution, zirconium oxynitrate hydrate is dispersed in deionized water to prepare a 0.1M zirconium salt solution, 4mmol citric acid is added to 20mL indium nitrate solution, stirred to dissolve, and then 2mL 0.01M CTAB solution and 2mL 0.01M PVP solution are added, mixed evenly, and then 20mL 0.1M zirconium salt solution is added, and the pH is adjusted to 7 with sodium hydroxide solution and then transferred to a polytetrafluoroethylene-lined hydrothermal reactor, and the hydrothermal reaction is carried out at 128°C for 15.3h. After centrifugation, washing and drying, a precipitate is obtained, which is transferred to a muffle furnace, and the temperature is increased to 370°C at 3°C / min in an air atmosphere and calcined for 3.6h to obtain an In2O3-ZrO2 complex;

[0089] S2, add 20mL of 0.1M zinc nitrate solution to 20mL of 0.5M 2-methylimidazole solution, stir evenly, and adjust the pH to 8 with sodium hydroxide solution to obtain a MOF precursor solution, disperse 2g of In2O3-ZrO2 complex in the MOF precursor solution, transfer it to a polytetrafluoroethylene-lined hydrothermal reactor after ultrasonic vibration, and hydrothermally react at 96°C for 9.3h. Wash and dry to obtain a MOF@In2O3-ZrO2 complex. Under an argon atmosphere, the dried MOF@In2O3-ZrO2 complex is placed in a tube furnace, heated to 460°C at 3°C / min, and calcined for 2.1h to obtain a C-MOF@In2O3-ZrO2 complex;

[0090] S3, adding 1 g of C-MOF@In2O3-ZrO2 complex to 30 mL of 0.1 M 1-butyl-3-methylimidazolium acetate solution, ultrasonically dispersing for 20 min, standing at 50 ° C for 6.9 h, distilling under reduced pressure, and vacuum drying to obtain an uncured C-MOF@In2O3-ZrO2 complex, placing the uncured C-MOF@In2O3-ZrO2 complex in a tube furnace, heating to 192 ° C under an argon atmosphere and keeping the temperature for 33 min, turning off the heating after the end of the heat preservation and continuously introducing argon to quickly cool the product to room temperature to obtain an IL@C-MOF@In2O3-ZrO2 complex;

[0091] S4, heating the IL@C-MOF@In2O3-ZrO2 composite to 160 °C in a tube furnace under H2(6%) / Ar atmosphere and keeping the temperature for 68 min to obtain the reduced IL@C-MOF@In2O3-ZrO2 composite;

[0092] S5, 90g of reduced IL@C-MOF@In2O3-ZrO2 composite, 1.5g of carbon fiber and 3.5g of graphite powder were mixed, and then 5g of silica sol was added. After extrusion, the mixture was dried under an argon atmosphere to obtain a catalyst for hydrogenation of carbon dioxide to methanol.

[0093] Comparative Example 1

[0094] The present comparative example provides a preparation method of a catalyst for methanol synthesis from carbon dioxide hydrogenation, which is different from Example 1 in that the volume of the zirconium salt solution in S1 is adjusted to 40 mL, which is increased by 20 mL compared to Example 1, and other process parameters and operating conditions are exactly the same as Example 1.

[0095] Comparative Example 2

[0096] The present comparative example provides a preparation method of a catalyst for methanol synthesis from carbon dioxide hydrogenation, which is different from Example 1 in that the volume of the zirconium salt solution in S1 is adjusted to 2 mL, which is reduced by 18 mL compared to Example 1, and other process parameters and operating conditions are exactly the same as Example 1.

[0097] Comparative Example 3

[0098] The present comparative example provides a preparation method of a catalyst for methanol synthesis from carbon dioxide hydrogenation, which is different from Example 1 in that the volume of the 2-methylimidazole solution in S2 is adjusted to 40 mL, which is increased by 20 mL compared to Example 1, and other process parameters and operating conditions are exactly the same as Example 1.

[0099] Comparative Example 4

[0100] The present comparative example provides a preparation method of a catalyst for methanol synthesis from carbon dioxide hydrogenation, which is different from Example 1 in that the volume of the 2-methylimidazole solution in S2 is adjusted to 2 mL, which is reduced by 18 mL compared to Example 1, and other process parameters and operating conditions are exactly the same as Example 1.

[0101] Test conditions: The prepared catalyst is loaded into the constant temperature zone of the fixed bed reaction tube, heated to 270℃ at a heating rate of 2℃ / min, the reaction pressure is 4 MPa, the volume ratio of hydrogen: carbon dioxide: nitrogen is 60:20:20, and GHSV = 15000 mL / (h·g). The test results are shown in Table 1.

[0102] Table 1 Test results of catalysts for methanol synthesis from carbon dioxide hydrogenation prepared in Examples 1-4 and Comparative Examples 1-4

[0103] <![CDATA[CO2转化率(%)]]> CH3OH selectivity (%) Example 1 22.3 76.6 Example 2 20.4 75.9 Example 3 21.8 74.7 Example 4 21.2 75.1 Comparative Example 1 14.7 52.4 Comparative Example 2 15.2 57.6 Comparative Example 3 15.6 55.1 Comparative Example 4 14.3 54.7

[0104] From Table 1, compared with Example 1, the CO2 conversion and CH3OH selectivity of Comparative Example 1 are reduced; the CO2 conversion and CH3OH selectivity of Comparative Example 2 are reduced. In Comparative Example 1, too much zirconium salt can lead to too high relative content of ZrO2, and the oxygen vacancy density of ZrO2 itself is relatively low, and compared with In2O3, the adsorption and activation ability of CO2 is weak, thereby reducing the overall activation ability of the catalyst to CO2, leading to a decrease in CO2 conversion, and although the Lewis acid site of ZrO2 can stabilize the reaction intermediate, too high proportion of ZrO2 can change the acid-base balance of the catalyst surface, leading to a deviation of the reaction path to side reactions (such as reverse water-gas shift reaction) and a decrease in methanol selectivity. In Comparative Example 2, ZrO2 is an important source of Lewis acid sites, and its Lewis acid sites play an important role in adsorbing and stabilizing reaction intermediates, and too low content of ZrO2 can lead to a lack of sufficient Lewis acid sites on the catalyst surface, and the stability of the intermediate will decrease, leading to a decrease in the efficiency of the methanol generation path and a decrease in methanol selectivity. Compared with Example 1, the CO2 conversion and CH3OH selectivity of Comparative Example 3 are reduced; the CO2 conversion and CH3OH selectivity of Comparative Example 4 are reduced. In Comparative Example 3, when the 2-methylimidazole solution is excessive, the MOF growth can be excessive, generating a relatively thick organic framework layer, leading to the surface active sites of the In2O3-ZrO2 composite being covered by the MOF, thereby reducing the contact of CO2 and H2 molecules with the active sites, and the adsorption and activation ability of CO2 is reduced, leading to a decrease in CO2 conversion and a decrease in methanol selectivity. In Comparative Example 4, the amount of 2-methylimidazole is insufficient, and the growth of MOF can be incomplete, leading to a decrease in the interface effect of the MOF@In2O3-ZrO2 composite and a decrease in the stabilizing effect of the MOF on the intermediate, thereby reducing the methanol selectivity.

[0105] The above description is merely a specific implementation of the present application, but the protection scope of the present application is not limited thereto. It should be understood by those skilled in the art that any changes or replacements within the technical scope disclosed by the present application can be easily conceived, and all these changes and replacements are within the protection scope and disclosure scope of the present application.

Claims

1. A method for preparing a catalyst for producing methanol by hydrogenation of carbon dioxide, characterized in that: The preparation method comprises: S1, adding citric acid, CTAB solution, PVP solution and zirconium salt solution to indium nitrate solution, hydrothermally reacting to obtain a precipitate, and calcining the precipitate to obtain an In2O3-ZrO2 composite; S2, adding zinc nitrate solution to 2-methylimidazole solution to obtain a MOF precursor solution, dispersing In2O3-ZrO2 complex in the MOF precursor solution, hydrothermally reacting to obtain a MOF@In2O3-ZrO2 complex, and calcining the dried MOF@In2O3-ZrO2 complex under an argon atmosphere to obtain a C-MOF@In2O3-ZrO2 complex, wherein the calcination temperature is 400-500°C; S3, adding the C-MOF@In2O3-ZrO2 complex to a 1-butyl-3-methylimidazolium acetate solution, allowing the solution to stand to obtain an uncured C-MOF@In2O3-ZrO2 complex, heating and maintaining the uncured C-MOF@In2O3-ZrO2 complex, and turning off the heating after the insulation, while continuously introducing argon gas to rapidly cool the product to room temperature, to obtain an IL@C-MOF@In2O3-ZrO2 complex; S4, heating and keeping the IL@C-MOF@In2O3-ZrO2 composite in a tube furnace under H2 / Ar atmosphere to obtain a reduced IL@C-MOF@In2O3-ZrO2 composite; S5, mixing the reduced IL@C-MOF@In2O3-ZrO2 composite with an inorganic binder and then adding silica sol, extruding and drying under an argon atmosphere to obtain a catalyst for hydrogenation of carbon dioxide to methanol; The volume ratio of the indium nitrate solution, the zirconium salt solution, the CTAB solution and the PVP solution is 10:10:1:1; The volume ratio of the zinc nitrate solution to the 2-methylimidazole solution is 1:

1.

2. The method for preparing a catalyst for producing methanol by hydrogenation of carbon dioxide according to claim 1, wherein: In S1, The concentration of the indium nitrate solution is 0.2M; The concentration of the zirconium salt solution is 0.1M.

3. The method for preparing a catalyst for producing methanol by hydrogenation of carbon dioxide according to claim 1, wherein: In S2, The concentration of the zinc nitrate solution is 0.1M; The concentration of the 2-methylimidazole solution is 0.5M.

4. The method for preparing a catalyst for producing methanol by hydrogenation of carbon dioxide according to claim 1, wherein: In S2, The mass volume ratio of the In2O3-ZrO2 complex to the zinc nitrate solution is 1 g:10 mL.

5. The method for preparing a catalyst for producing methanol by hydrogenation of carbon dioxide according to claim 1, characterized in that: In S3, The concentration of the 1-butyl-3-methylimidazolium acetate solution is 0.1 M, and the solvent is ethanol; The mass volume ratio of the C-MOF@In2O3-ZrO2 composite and the 1-butyl-3-methylimidazolium acetate solution is 1 g:30 mL.

6. The method for preparing a catalyst for producing methanol by hydrogenation of carbon dioxide according to claim 1, characterized in that: In S4, The volume proportion of H2 in the H2 / Ar is 5-7%; The insulation time is 60-80 minutes.

7. The method for preparing a catalyst for producing methanol by hydrogenation of carbon dioxide according to claim 1, characterized in that: In S5, The mass ratio of the reduced IL@C-MOF@In2O3-ZrO2 composite, the inorganic binder and the silica sol is 90:5:

5.

8. The method for preparing a catalyst for producing methanol by hydrogenation of carbon dioxide according to claim 1, characterized in that: In S5, The inorganic binder is carbon fiber and graphite powder, with a mass ratio of 3:

7.

9. A catalyst for producing methanol by hydrogenating carbon dioxide obtained according to the preparation method according to any one of claims 1 to 8.

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