A highly zinc-loaded mesoporous alumina-based CO2 hydrogenation catalyst, its solvent-free preparation method, and its application.

Abstract

This invention relates to the field of CO2 resource utilization and hydrogenation catalysis technology, and discloses a highly zinc-loaded mesoporous alumina-based CO2 hydrogenation catalyst, its solvent-free preparation method, and its applications. The preparation method includes: mixing and stirring a structure-directing agent composed of a polyhydroxy organic compound and an organic acid, an inorganic acid, and an aluminum source in a sealed container to form a clear system; then slowly adding a zinc source solution and a copper source solution to obtain a homogeneous precursor; and finally drying and calcining to obtain the catalyst. The highly zinc-loaded mesoporous alumina-based CO2 hydrogenation catalyst (Cu-Zn@Al2O3) prepared by this invention has a specific surface area of ​​100–400 m² / g. 2 / g, with a pore size distribution of 2–50nm, which facilitates mass transfer and diffusion of CO2, H2, and products; the preparation method is solvent-free and uses a one-pot synthesis with few steps, suitable for the hydrogenation reaction of CO2 and H2 under fixed-bed conditions, and can be used to prepare methanol, methane, carbon monoxide and / or C1–C4 low-carbon hydrocarbons and reduce the CO2 content in the feed gas. When methanol is the main product, the methanol selectivity can reach ≥90%.

Description

Technical Field

[0001] This invention belongs to the field of CO2 resource utilization and hydrogenation catalysis technology, specifically relating to a highly zinc-loaded mesoporous alumina-based CO2 hydrogenation catalyst and its solvent-free preparation method and application. Background Technology

[0002] Steel smelting and energy-intensive industries such as coal-fired / gas-fired power plants are widely recognized as major sources of carbon dioxide (CO2) emissions. Long-term excessive emissions have triggered and exacerbated a series of environmental and socio-economic problems, including global warming, sea-level rise, increased extreme weather events, and ecosystem degradation. Traditional CO2 control primarily relies on capture and storage (CCS), but this technology generally suffers from limitations such as high construction and operating costs, difficulty in assessing the safety of long-term storage, and limited direct economic benefits, making it difficult to meet the demands of large-scale emission reduction and resource utilization under the "dual carbon" goals. Compared to CCS technology, CO2 hydrogenation into high-value-added products such as methanol, methane, carbon monoxide, and low-carbon hydrocarbons is considered one of the important pathways for CO2 waste management in the industrial sector. On the one hand, CO2 in industrial exhaust gas has a concentrated source, relatively stable composition, and high purity, providing a good raw material basis for CO2 hydrogenation conversion, enabling the treatment mode to shift from "passive storage" to "active utilization". On the other hand, the sale of CO2 hydrogenation products can offset emission reduction costs to a certain extent, alleviate the emission reduction pressure on enterprises, and increase their enthusiasm for participating in CO2 treatment. Therefore, the development of efficient and stable CO2 hydrogenation catalysts is of great significance.

[0003] Currently, research on CO2 hydrogenation catalysts mainly focuses on Cu-Zn-Al2O3, Ni-based, noble metal-based, and oxide catalytic systems such as In and Zr, with Al2O3, SiO2, ZrO2, and their composite oxides being the most common supports. Traditional methanol synthesis catalysts such as Cu-Zn-Al2O3 exhibit certain activity under medium-high temperature and high pressure conditions, but their CO2 conversion rate is low at low temperatures, and their selectivity for methanol or specific low-carbon products is limited. Furthermore, they are prone to sintering deactivation in atmospheres containing water or impurities. Ni-based and some noble metal catalysts often exhibit excessive CO2 reduction, generating large amounts of methane or deep cracking products, making it difficult to balance target product selectivity with energy efficiency.

[0004] In catalyst preparation, existing CO2 hydrogenation catalysts mostly employ wet chemical routes such as impregnation, co-precipitation, or sol-gel methods, requiring large amounts of organic or inorganic solvents. These methods involve complex multi-step dispersion and loading processes, and the active components are prone to agglomeration during calcination, making it difficult to achieve uniform dispersion of high-load metal species on the inner and outer surfaces of the support. Furthermore, traditional dense alumina supports have small pore sizes and limited specific surface areas, which are detrimental to the mass transfer of CO2 molecules and reactants, affecting catalytic performance and stability.

[0005] In recent years, mesoporous alumina, with its regular pore structure and large specific surface area, has been considered an excellent support for constructing highly efficient CO2 hydrogenation catalysts due to its abundant surface acid-base sites and good thermal stability. Zinc, as an important functional component for CO2 adsorption and activation, can synergistically interact with alumina to improve CO2 adsorption activity and the stability of intermediate species; the synergistic effect of copper and zinc also benefits the formation and transformation of key intermediates in the CO2 hydrogenation process, thereby improving the selectivity of target products such as methanol. However, under high zinc loading conditions, zinc species are more prone to agglomeration and pore obstruction, leading to a decrease in the integrity of the mesoporous structure and uneven distribution of active components inside and outside the pores, further affecting the CO2 hydrogenation activity and stability. In existing technologies, the preparation of Cu / Zn supported mesoporous alumina-based catalysts still largely relies on solvent-based impregnation or precipitation processes. These processes generally involve numerous steps, high solvent consumption, heavy environmental burden, and difficulties in maintaining high dispersion of active species and easy damage to the mesoporous structure under high loading conditions. Therefore, how to construct highly dispersed and reasonably loaded mesoporous alumina-based CO2 hydrogenation catalysts with zinc in a simple one-pot method under solvent-free conditions, while taking into account both environmental friendliness and industrial scale-up feasibility, remains an important technical problem to be solved in this field. Summary of the Invention

[0006] This invention addresses the problems of insufficient activity of existing CO2 hydrogenation catalysts at low temperatures, easy migration and agglomeration of metal components under high loading conditions leading to deactivation, and the high solvent consumption, cumbersome steps, easy agglomeration of active components during drying and calcination, and difficulty in obtaining both regular mesoporous structures and highly dispersed active components in traditional wet chemical preparation routes. It provides a highly zinc-loaded mesoporous alumina-based CO2 hydrogenation catalyst, its solvent-free preparation method, and its applications. This method utilizes a structure-directing agent composed of a polyhydroxy organic compound and an organic acid to achieve the construction of mesoporous alumina structures and promote the high dispersion of Cu and Zn species in a one-pot process under solvent-free conditions, thereby improving CO2 adsorption and activation capacity and reaction stability. It is suitable for emission reduction and resource utilization of CO2-containing gases such as industrial exhaust gases.

[0007] To achieve the above objectives, the technical solution of the present invention is as follows: The first aspect of this invention provides a solvent-free method for preparing a highly zinc-loaded mesoporous alumina-based CO2 hydrogenation catalyst, comprising the following steps: (1) Add the structure-directing agent, inorganic acid and aluminum source to a sealed glass bottle and mix and stir for 10-60 min to form a clear solution or a homogeneous sol to obtain an aluminum source sol; the structure-directing agent is formed by compounding a polyhydroxy organic compound with an organic acid, wherein the polyhydroxy organic compound is glucose and / or sucrose, and the organic acid is citric acid and / or tartaric acid; (2) Under stirring conditions, the active component is slowly added to the aluminum source sol and stirred for 0.5-3 hours to mix thoroughly, so as to obtain a homogeneous precursor mixture; the active component is a zinc source solution and a copper source solution; (3) After the precursor mixture is left to stand, it is spread evenly in a petri dish and dried at 50-90℃ for 24-72h to remove moisture and form a solid precursor. (4) The solid precursor is placed in a muffle furnace and heated to 450-700℃ at a heating rate of 0.5-5℃ / min in an air atmosphere. After holding at the temperature for 2-6 hours, it is naturally cooled to obtain a mesoporous alumina-based CO2 hydrogenation catalyst with high zinc loading.

[0008] Further, based on the aluminum source, the molar ratio of the polyhydroxy organic compound to the organic acid is 0.5–20:0.5–30 mmol. The structure-directing agent regulates the hydrolysis and condensation processes of aluminum species through complexation with the aluminum source, thereby inducing the formation of mesoporous alumina structures and promoting the uniform dispersion of Cu and Zn species on the carrier surface and within the pores.

[0009] Furthermore, the zinc source is an aqueous solution of zinc nitrate with a mass fraction of 5–20%, and the copper source is an aqueous solution of copper nitrate with a mass fraction of 2–10%.

[0010] Furthermore, the Zn to Cu molar ratio of the zinc source to the copper source is 0.5:1–10:1, preferably 1:1–5:1.

[0011] Furthermore, the drying step is carried out at 60–80°C for 36–60 h to obtain a solid precursor with a regular mesoporous structure.

[0012] A second aspect of the present invention provides the above-mentioned highly zinc-loaded mesoporous alumina-based CO2 hydrogenation catalyst, comprising an active component and a support, wherein the support is mesoporous alumina, and the active component is copper and zinc; the total mass percentage of the active component in the catalyst is 1–40% based on oxides, wherein the mass percentage of ZnO in the catalyst is 1–30%, and the mass percentage of CuO in the catalyst is 0.1–10%.

[0013] Furthermore, the catalyst has a mesoporous structure with a specific surface area of ​​100–400 m². 2 / g, pore size distribution 2–50nm, and Cu and Zn species exist as highly dispersed oxides or oxide-spinel phases on the surface and in the pores of mesoporous alumina.

[0014] The third aspect of this invention provides the application of the highly zinc-loaded mesoporous alumina-based CO2 hydrogenation catalyst in the CO2 hydrogenation catalytic reaction.

[0015] Further, the method of application is as follows: CO2-containing feed gas and hydrogen are mixed at a volume ratio of 1:(1-10), and then passed through a fixed-bed reactor filled with the mesoporous alumina-based CO2 hydrogenation catalyst with high zinc loading, and the CO2 hydrogenation reaction is carried out at 150-400℃ and 0.1-5MPa, and the CO2 conversion rate is tested.

[0016] This invention employs a solvent-free one-pot synthesis strategy, synergistically assembling and transforming an aluminum source, a structure-directing agent composed of a polyhydroxy organic compound and an organic acid, and copper and zinc sources within the same system. This reduces the process complexity caused by solvent involvement and multi-step loading processes in traditional wet chemical routes such as impregnation and co-precipitation. The structure-directing agent, formed by combining glucose and / or sucrose with citric acid and / or tartaric acid, can regulate the hydrolysis and condensation processes of aluminum species under solvent-free conditions, inducing the formation of a regular mesoporous alumina structure. Simultaneously, it promotes the high dispersion of Cu and Zn species on the support surface and within the pores, enhancing their interaction. This, in turn, facilitates CO2 adsorption and activation and improves the intrinsic activity of the catalyst.

[0017] The advantages and beneficial effects of this invention are: (1) The specific surface area of ​​the highly zinc-loaded mesoporous alumina-based CO2 hydrogenation catalyst (Cu-Zn@Al2O3) prepared in this invention is 100–400 m². 2 / g, with a pore size distribution of 2–50nm, which is conducive to the mass transfer and diffusion of CO2, H2 and products; at the same time, Cu and Zn species exist stably on the surface and in the pores of mesoporous alumina as highly dispersed oxides or oxide-spinel phases, which is beneficial to the mass transfer and diffusion of reactants and products, and improves reaction efficiency and stability.

[0018] (2) The catalyst of the present invention exhibits high activity and stability in the CO2 hydrogenation reaction at 150–400℃ and 0.1–5MPa, and can obtain high selectivity for the target product (the methanol selectivity can reach ≥90% when methanol is the main product).

[0019] (3) The preparation method of the present invention is solvent-free and uses a one-pot synthesis method. The preparation process has fewer steps, is simple to operate, and has high atom utilization. It greatly reduces the use of organic solvents and waste liquid discharge, and has good environmental friendliness and industrial scale-up potential.

[0020] (4) The catalyst prepared by the present invention is suitable for the hydrogenation conversion of CO2-containing feed gas under fixed bed conditions. It can be used to prepare methanol, methane, carbon monoxide and / or C1–C4 low carbon hydrocarbons and reduce the CO2 content in the feed gas. The preparation method is green and simple, and is suitable for emission reduction and resource utilization of CO2-rich gases such as industrial tail gas. It has good application prospects. Attached Figure Description

[0021] Figure 1 The wide-angle XRD spectra of the catalysts prepared in Examples 1-5 are shown below. Figure 2 The images show the N2 adsorption-desorption isotherms and pore size distribution of the catalysts prepared in Examples 1-5. Detailed Implementation

[0022] The present invention will be further described in detail below through specific embodiments. The following embodiments are merely descriptive and not limiting, and should not be used to limit the scope of protection of the present invention.

[0023] Example 1 A solvent-free method for preparing a catalyst includes the following steps: (1) Place 10 mmol glucose, 5 mL hydrochloric acid (HCl) and 10 mmol aluminum isopropoxide in a sealed glass bottle and stir for 30 min to mix them to form a clear solution or a homogeneous sol system, thus obtaining an aluminum source sol. (2) Under stirring conditions, a 13% zinc nitrate aqueous solution was slowly added to the aluminum source sol. The amount added was adjusted so that the ZnO mass fraction in the final catalyst was 10wt%. Stirring was continued for 30 minutes to make the mixture uniform and a homogeneous precursor mixture was obtained. (3) After the precursor mixture is left to stand for 2 hours, it is spread evenly on a petri dish and dried in an oven at 60°C for 48 hours to remove moisture and form a solid precursor. (4) The solid precursor was placed in a muffle furnace and heated to 600°C at 1°C / min in an air atmosphere. After calcination for 4 hours and natural cooling, the catalyst was obtained and labeled as sample A.

[0024] Example 2 A solvent-free method for preparing a catalyst includes the following steps: (1) Place 10 mmol citric acid, 5 mL hydrochloric acid (HCl) and 10 mmol aluminum isopropoxide in a sealed glass bottle and stir for 30 min to mix them to form a clear solution or a homogeneous sol system, thus obtaining an aluminum source sol. (2) Under stirring conditions, a 13% zinc nitrate aqueous solution was slowly added to the aluminum source sol. The amount added was adjusted so that the ZnO mass fraction in the final catalyst was 10wt%. Stirring was continued for 30 minutes to make the mixture uniform and a homogeneous precursor mixture was obtained. (3) After the precursor mixture is left to stand for 2 hours, it is spread evenly on a petri dish and dried in an oven at 60°C for 48 hours to remove moisture and form a solid precursor. (4) The solid precursor was placed in a muffle furnace and heated to 600°C at 1°C / min in an air atmosphere. After calcination for 4 hours and natural cooling, the catalyst was obtained and labeled as sample B.

[0025] Example 3 A solvent-free preparation method for a mesoporous alumina-based CO2 hydrogenation catalyst includes the following steps: (1) Place 10 mmol glucose, 10 mmol citric acid, 5 mL hydrochloric acid (HCl) and 10 mmol aluminum isopropoxide in a sealed glass bottle and stir for 30 min to mix and clarify to obtain aluminum source sol; (2) Under stirring conditions, a 13% zinc nitrate aqueous solution was slowly added to the aluminum source sol. The amount added was adjusted so that the ZnO mass fraction in the final catalyst was 10wt%. Stirring was continued for 30 minutes to make the mixture uniform and a homogeneous precursor mixture was obtained. (3) After the precursor mixture is left to stand for 2 hours, it is spread evenly on a petri dish and dried in an oven at 60°C for 48 hours to remove moisture and form a solid precursor. (4) The solid precursor was placed in a muffle furnace and heated to 600°C at 1°C / min in an air atmosphere. After calcination for 4 hours and natural cooling, a mesoporous alumina-based CO2 hydrogenation catalyst containing only zinc (Zn@Al2O3) was obtained and labeled as sample C.

[0026] Example 4 A solvent-free preparation method for a mesoporous alumina-based CO2 hydrogenation catalyst includes the following steps: (1) Place 10 mmol sucrose, 10 mmol tartaric acid, 5 mL hydrochloric acid (HCl) and 10 mmol aluminum isopropoxide in a sealed glass bottle and stir for 30 min to mix and clarify to obtain aluminum source sol; (2) Under stirring conditions, 13% zinc nitrate aqueous solution and 5% copper nitrate aqueous solution were slowly added to the aluminum source sol. The amount of the two solutions added was adjusted so that the mass fraction of ZnO in the final catalyst was 10wt% and the mass fraction of CuO was 1wt%. Stirring was continued for 30 minutes to make the mixture uniform and a homogeneous precursor mixture was obtained. (3) After the precursor mixture is left to stand for 2 hours, it is spread evenly on a petri dish and dried in an oven at 60°C for 48 hours to remove moisture and form a solid precursor. (4) The solid precursor was heated to 600°C in a muffle furnace under an air atmosphere at a rate of 1°C / min and calcined for 4 hours. After natural cooling, a mesoporous alumina-based CO2 hydrogenation catalyst with high zinc loading (Cu-Zn@Al2O3) was obtained and labeled as sample D.

[0027] Example 5 A solvent-free preparation method for a mesoporous alumina-based CO2 hydrogenation catalyst includes the following steps: (1) Place 5 mL of hydrochloric acid (HCl) and 10 mmol of aluminum isopropoxide in a sealed glass bottle and stir for 30 min to mix and clarify, thus obtaining aluminum source sol; (2) Under stirring conditions, 13% zinc nitrate aqueous solution and 5% copper nitrate aqueous solution were slowly added to the aluminum source sol. The amount added was adjusted so that the mass fraction of ZnO in the final catalyst was 20wt% and the mass fraction of CuO was 1wt%. Stirring was continued for 30min to make the mixture uniform and a homogeneous precursor mixture was obtained. (3) After the precursor mixture is left to stand for 2 hours, it is spread evenly on a petri dish and dried in an oven at 60°C for 48 hours to remove moisture and form a solid precursor. (4) The solid precursor was placed in a muffle furnace and heated to 600°C at 1°C / min in air atmosphere. After calcination for 4 hours and natural cooling, a high zinc-loaded Cu-Zn@Al2O3 catalyst was obtained and labeled as sample E.

[0028] Performance test analysis X-ray diffraction (XRD) tests were performed on an X'Pert3 powder diffractometer, with the X-rays originating from CuKα radiation (λ=1.5418Å), and the voltage and current being V=45kV and I=40mA, respectively.

[0029] The BET specific surface area and pore volume of the sample in the example were evaluated on a Micromeritics TriStarⅡ 3020 system, and were degassed at 200°C for 12 h before measurement.

[0030] CO2 Catalytic Oxidation Performance Testing: The performance of the catalytic reaction was tested using a fixed-bed microtubular catalyst evaluation device (Beijing MRT-3203-G type microtubular reaction device). The gaseous components of the reaction products were analyzed using an online gas chromatograph (equipped with a TCD / FID detector) to determine the volume fractions of CO2, CO, CH4, methanol, and low-carbon hydrocarbons.

[0031] Before testing, 100 mg of catalyst was weighed and thoroughly mixed with 0.45 g of SiC, then packed into a quartz fixed-bed reaction tube. Reduction was carried out at 300-400 °C for 1-2 h under a 10% H2 / N2 atmosphere, followed by a reduction to the set reaction temperature. The CO2 hydrogenation reaction feed gas composition was 10-30% CO2, 30-70% H2, with the remainder being N2 or Ar as an internal standard and dilution gas. The H2 / CO2 molar ratio was generally 3-4, and the total flow rate was 30-100 mL / min. The reaction pressure was 0.1-5.0 MPa, and the reaction temperature range was 200-400 °C. The composition of the outlet gas was recorded under different temperature and pressure conditions, and the CO2 conversion rate and the selectivity of each product (CO, methane, methanol, and C1-C4 low-carbon hydrocarbons) were calculated to evaluate the CO2 hydrogenation catalytic performance of the Cu-Zn@Al2O3 catalyst of this invention. The test results are shown in Tables 2 and 3.

[0032] The catalysts obtained in the examples were analyzed and tested accordingly: Figure 1 These are the wide-angle XRD spectra of the catalysts prepared in Examples 1-5. Figure 1 As can be seen, all catalysts exhibited a broad amorphous diffraction peak within the 2θ = 20°–40° range, and no obvious characteristic peaks of crystalline metal oxides were observed. Furthermore, no independent diffraction peaks for CuO, ZnO, or other metal oxides were observed in any of the samples, indicating that copper and zinc species did not precipitate as large grains, but were highly dispersed on the inner and outer surfaces of the alumina support, or partially interacted with the support through solid solution / composite phase reactions to form indistinguishable microcrystalline phases. This result demonstrates that the solvent-free one-pot method of this invention is beneficial for achieving high dispersion and firm anchoring of Cu and Zn species within the mesoporous alumina framework, helping to maintain the structural integrity of the support, while simultaneously providing a large number of uniformly distributed active sites for the CO2 hydrogenation reaction.

[0033] Figure 2 The images show the N2 adsorption-desorption curves and pore size distribution diagrams of the catalysts prepared in Examples 1-5. Figure 2 It can be seen that the N2 adsorption-desorption isotherms of all samples exhibit typical type IV curves, indicating that the obtained materials all have obvious mesoporous structures. Among them, sample AD shows a relatively gentle saturated adsorption plateau accompanied by an H1-type hysteresis loop in the relative pressure range of 0.6-1.0, indicating that these samples have a relatively uniform pore size and a relatively regular channel mesoporous structure. With the increase of the total Cu and Zn loading, the overall surface area and pore volume are still maintained, which is conducive to the diffusion of reactant molecules and the full exposure of active sites. The pore size distribution of each catalyst is mainly concentrated in the 2-40 nm range, further confirming that the Cu-Zn@Al2O3 catalyst prepared in this invention has a typical mesoporous material structure.

[0034] Table 1 Catalyst structural parameters of the examples

[0035] Table 1 shows the structural parameters of the catalyst samples prepared in Examples 1-5. As can be seen from Table 1, Examples 1 and 2 used only glucose or citric acid as structure directing agents. The catalyst prepared in Example 5 without a structure directing agent had a lower specific surface area and pore volume. The catalyst prepared in Example 3 using a structure directing agent composed of glucose and citric acid significantly improved the specific surface area. The catalyst prepared in Example 4 using sucrose and tartaric acid, along with zinc nitrate and copper nitrate, exhibited even better specific surface area and pore volume. This indicates that the structure directing agent composed of glucose / sucrose and citric acid / tartaric acid can regulate the hydrolysis and condensation process of aluminum species through complexation with the aluminum source, thereby inducing the formation of mesoporous alumina structures and promoting the uniform dispersion of Cu and Zn species on the support surface and within the pores. Cu and Zn can enhance their interaction. Under the condition of introducing a complex structure directing agent, the catalyst as a whole can obtain a higher specific surface area. When the total metal loading of Cu and Zn is further increased, the specific surface area decreases compared to the low-load sample, but still remains at a high level. This is mainly attributed to the fact that when the metal loading increases, some CuO and ZnO species are deposited on the inner wall of the pores in the form of oxides or composite phases, partially occupying the original pore space, thus reducing the pore size, but the overall mesoporous framework structure remains intact. This indicates that the present invention uses a structure-directing agent composed of glucose / sucrose and citric acid / tartaric acid to synergistically regulate the hydrolysis and polycondensation process of aluminum species under solvent-free one-pot conditions, maintaining the mesoporous structure characteristics well even under high metal loading conditions.

[0036] Table 2 shows the performance tests of the catalysts prepared in Examples 1-5 for CO2 hydrogenation.

[0037] Table 2 shows the CO2 hydrogenation conversion rates of the catalysts prepared in Examples 1-5 at different temperatures. As can be seen from Table 2, within the test temperature range of 150-250℃, the CO2 conversion rates of the catalysts in Examples 1-6 gradually increased with increasing reaction temperature, but there were significant differences in activity among the different samples. Samples AD showed low CO2 conversion rates in the low-temperature region (150-190℃). Although the conversion rate improved somewhat with increasing temperature to 200-250℃, it remained at a low level overall. Sample D, on the other hand, showed significant CO2 conversion ability at 150℃, and the conversion rate increased rapidly with increasing temperature, achieving a CO2 conversion rate of nearly 11.1% at around 200℃, and maintaining a high conversion rate of 15.2% at 250℃.

[0038] Table 3. Selectivity test data for CO2 hydrogenation of the catalysts prepared in Examples 1-5.

[0039] Table 3 shows that, under the same reaction conditions, the product distribution of different catalysts differs significantly. The Cu–Zn@Al2O3 catalyst (sample D) prepared using a composite structure-directing agent maintains a high CO2 conversion rate while exhibiting significantly higher selectivity for methanol, whereas the selectivity for byproducts such as CO and CH4 is significantly reduced. This indicates that the high dispersion and synergistic effect of Cu and Zn species on the mesoporous alumina support are beneficial for the selective conversion of CO2 hydrogenation to methanol. In contrast, sample E, prepared without the structure-directing agent, although possessing some CO2 conversion capacity, shows a significant decrease in methanol selectivity and enhanced side reactions, further verifying the crucial role of the composite structure-directing agent in constructing a highly efficient CO2 hydrogenation catalyst.

[0040] Therefore, this invention demonstrates that by adjusting the loading and ratio of Cu and Zn, the CO2 hydrogenation activity of the catalyst can be significantly affected. Specifically, the highly loaded Cu-Zn / mesoporous alumina catalyst (sample D) exhibits superior CO2 conversion performance at low temperatures, indicating that the mesoporous structure induced by the composite structure-directing agent of this invention, combined with the highly dispersed state of Cu and Zn, provides more abundant and effective active sites and improves low-temperature reaction performance. Furthermore, the results of single-component comparative samples (such as comparative samples A / B containing only polyhydroxy components or only organic acid components) further demonstrate that the composite structure-directing agent system has a synergistic promoting effect on mesoporous structure formation and active component dispersion, thereby enhancing CO2 hydrogenation performance and stability.

[0041] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several modifications and improvements without departing from the inventive concept, and these all fall within the protection scope of the present invention.

Claims

1. A one-pot precursor co-assembly method for a highly zinc-loaded mesoporous alumina-based CO2 hydrogenation catalyst without added solvent, characterized in that, Includes the following steps: (1) The structure directing agent, inorganic acid and aluminum source are added to a sealed container and mixed and stirred to obtain aluminum source sol; the structure directing agent is formed by compounding polyhydroxy organic compound and organic acid, the polyhydroxy organic compound is glucose and / or sucrose, the organic acid is citric acid and / or tartaric acid; the inorganic acid is hydrochloric acid, and the aluminum source is aluminum isopropoxide; (2) Under stirring conditions, the active component is slowly added to the aluminum source sol and stirring is continued to obtain a homogeneous precursor mixture; the active component is a zinc source solution and a copper source solution; (3) After the precursor mixture is allowed to stand, it is spread evenly in a petri dish and dried at 50-90℃ for 24-72h to obtain a solid precursor; (4) The solid precursor is heated to 450-700℃ in air at a heating rate of 0.5-5℃ / min, and calcined for 2-6 hours. After cooling, a high-loaded zinc mesoporous alumina-based CO2 hydrogenation catalyst is obtained. The aluminum source, the structure-directing agent composed of polyhydroxy organic compounds and organic acids, and the copper and zinc sources are synergistically assembled and transformed in the same system. The structure-directing agent formed by the compound regulates the hydrolysis and condensation process of aluminum species under solvent-free conditions, induces the formation of a regular mesoporous alumina structure, and promotes the high dispersion of Cu and Zn species on the surface and in the pores of the support.

2. The preparation method according to claim 1, characterized in that, Based on the aluminum source, the molar ratio of the polyhydroxy organic compound to the organic acid is 0.5–20:0.5–30.

3. The preparation method according to claim 1, characterized in that, The zinc source is a zinc nitrate aqueous solution with a mass fraction of 5-20%, and the copper source is a copper nitrate aqueous solution with a mass fraction of 2-10%.

4. The preparation method according to claim 1, characterized in that, The molar ratio of Zn to Cu in the zinc source to the copper source is 0.5:1 to 10:

1.

5. The preparation method according to claim 1, characterized in that, The drying in step (3) is carried out at 60-80℃ for 36-60h.

6. The preparation method according to claim 1, characterized in that, The stirring time in step (1) is 10-60 min.

7. A highly zinc-loaded mesoporous alumina-based CO2 hydrogenation catalyst, characterized in that, Prepared by the preparation method according to any one of claims 1-6, comprising an active component and a support, wherein the support is mesoporous alumina, and the active component is copper and zinc; based on oxides, the total mass percentage of the active component in the catalyst is 1-40%, wherein the mass percentage of ZnO in the catalyst is 1-30%, and the mass percentage of CuO in the catalyst is 0.1-10%.

8. The highly zinc-loaded mesoporous alumina-based CO2 hydrogenation catalyst according to claim 7, characterized in that, The catalyst has a mesoporous structure and a specific surface area of ​​100–400 m². 2 / g, pore size distribution 2–50nm, and Cu and Zn species exist as highly dispersed oxides or oxide-spinel phases on the surface and in the pores of mesoporous alumina.

9. The application of a highly zinc-loaded mesoporous alumina-based CO2 hydrogenation catalyst as described in claim 7 or 8 in the CO2 hydrogenation catalytic reaction.

10. The application according to claim 9, characterized in that, The method of application is as follows: CO2-containing feed gas and hydrogen are mixed at a volume ratio of 1:(1-10), and then passed through a fixed-bed reactor filled with the mesoporous alumina-based CO2 hydrogenation catalyst with high zinc loading. The CO2 hydrogenation reaction is carried out at 150-400℃ and 0.1-5MPa, and the CO2 conversion rate and product selectivity are tested.

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