Cu-Fe-based spinel catalyst suitable for CO2 recycling as well as preparation method and application of Cu-Fe-based spinel catalyst

Abstract

The invention discloses a Cu-Fe-based spinel catalyst suitable for CO2 recycling as well as a preparation method and application of the Cu-Fe-based spinel catalyst. The Cu-Fe-based spinel catalyst comprises a carrier and a metal oxide loaded on the carrier, the metal oxide comprises CuO and a CuxFeyO4 composite oxide, and the CuxFeyO4 composite oxide is of a spinel structure; and the carrier is CeO2. The catalyst provided by the invention shows excellent CH4 and CH3OH selectivity in CO2 hydrogenation reaction, and reduces the generation of CO, so that efficient CO2 conversion is realized, the problems of poor selectivity and insufficient stability of a traditional Cu-based catalyst are solved, the catalyst has important technical innovation and practical value, a feasible efficient catalytic material is provided for CO2 resource utilization, and the catalyst has a wide application prospect. The method can be used in the fields of clean energy production, greenhouse gas emission reduction, carbon resource utilization and the like.

Description

Technical Field

[0001] The present invention relates to the field of catalyst technology, and more specifically, to a Cu-Fe-based spinel catalyst suitable for CO2 resource recovery, and a preparation method and application thereof. Background Art

[0002] As the global requirements for carbon emission control increase, the reduction of CO2 as a greenhouse gas has attracted much attention. CO2 hydrogenation reaction is an important means to realize the resource utilization of CO2, especially in the preparation of high value-added chemicals (such as CH4 and CH3OH). CO2 hydrogenation can be achieved through the following main reactions:

[0003] Methanation reaction: CO2+4H2→CH4+2H2O

[0004] Methanol synthesis reaction: CO2+3H2→CH3OH+H2O

[0005] Methane is the main component of natural gas and can be used directly as a clean fuel; methanol is not only an important chemical raw material, but can also be used in liquid fuel, fuel cells and other applications. Therefore, the development of efficient CO2 hydrogenation catalysts is of great significance to promote the resource utilization of CO2 and reduce greenhouse gas emissions.

[0006] CO2 hydrogenation is a complex multi-step reaction process involving the adsorption, activation, hydrogenation and desorption of CO2 products. Therefore, it places high demands on the selectivity, activity and stability of the catalyst. Among them, Cu-based catalysts are widely used in methanol synthesis reactions due to their high activation ability for CO2 under medium temperature conditions, good selectivity and low cost. Cu has high dispersibility on oxide carriers such as CeO2 and ZnO, which can significantly improve the activation efficiency of CO2 and the selectivity of products. CeO2, as an oxide carrier, can further enhance the activity of Cu-based catalysts in CO2 hydrogenation reactions because it can provide reducible oxygen vacancies. However, traditional Cu-based catalysts have the following problems in the CO2 hydrogenation process: (1) High amount of CO byproduct generation: Cu-based catalysts will produce CO byproducts at high temperatures, affecting the selectivity of target products (such as CH4 and CH3OH). (2) Poor catalyst stability: Cu-based catalysts are prone to agglomeration and sintering under high temperature conditions, resulting in decreased activity and selectivity. (3) Limited hydrogen (H2) adsorption capacity: The H2 adsorption and activation efficiency of Cu-based catalysts is insufficient, resulting in a low hydrogenation rate. Therefore, how to optimize the structure of Cu-based catalysts, improve their stability and H2 adsorption activity, and improve the efficiency of CO2 hydrogenation to methane and methanol has become an important research direction.

[0007] Fe-based catalysts are widely used in the reduction of CO2 due to their excellent hydrogenation ability. Fe has a two-step reaction path in the CO2 reduction reaction, that is, first reducing CO2 to CO, and then further converting CO into hydrocarbons through Fischer-Tropsch synthesis. However, a single Fe-based catalyst is prone to generate a large amount of CH4 during the CO2 hydrogenation process, lacks selective control over CH3OH, and the stability and durability of a single Fe-based catalyst are also limited.

[0008] Therefore, it is an urgent problem to be solved at present to research and develop a CO2 hydrogenation catalyst with high catalytic activity and stability, which can effectively control the reaction path, thereby improving the selectivity of methane and methanol and reducing the generation of by-product CO. Summary of the invention

[0009] The purpose of the present invention is to overcome the above-mentioned defects of the prior art and provide a Cu-Fe-based spinel catalyst suitable for CO2 resource utilization and its preparation method and application. By introducing Fe components into the Cu / CeO2 catalyst, the structure and electronic properties of the catalyst are optimized to form a CuFe2O4 spinel structure, thereby increasing the surface area, oxygen vacancy content and H2 adsorption capacity of the catalyst surface, and improving the adsorption capacity for CO2; the Fe introduced into the CuFe2O4 spinel structure promotes the further hydrogenation of CO2, improves the thermodynamic and kinetic advantages of CH4 generation, and significantly inhibits the generation of CO. Finally, the Cu of the present invention x Fe y / CeO2 catalyst shows excellent CH4 and CH3OH selectivity in CO2 hydrogenation reaction and reduces the generation of CO, thereby achieving efficient CO2 conversion and solving the problems of poor selectivity and insufficient stability of traditional Cu-based catalysts. It has important technological innovation and practical value, and provides a feasible and efficient catalytic material for CO2 resource utilization, which can be used in the production of clean energy, greenhouse gas emission reduction, carbon resource utilization and other fields.

[0010] To achieve the above object, the technical solution of the present invention is as follows:

[0011] A Cu-Fe-based spinel catalyst suitable for CO2 resource recovery, the Cu-Fe-based spinel catalyst comprising a carrier and a metal oxide supported on the carrier; the carrier is CeO2; the metal oxide includes CuO and Cu x Fe y O4 composite oxide, wherein the Cu x Fe y O4 composite oxide has a spinel structure.

[0012] Optionally, the structural formula of the Cu-Fe-based spinel catalyst is Cu x Fe y / CeO2; wherein the molar ratio of Cu element to Fe element in the Cu-Fe-based spinel catalyst is x / y=1 / 2; the mass percentage of the total mass of Fe element to the total mass of the Cu-Fe-based spinel catalyst is 7.5%.

[0013] Optionally, the CuO and Cu in the Cu-Fe-based spinel catalyst x Fe y The O4 composite oxides are all nanoparticles.

[0014] Optionally, the CuO and Cu x Fe y The particle size of the O4 composite oxide is 5 nm to 20 nm to increase the surface area of ​​the catalytic active site.

[0015] Optionally, the catalyst has a spinel structure of Cu x Fe y The formation of O4 composite oxide increases the dispersibility of CuO, making the specific surface area of ​​the Cu-Fe-based spinel catalyst 70 m 2 / g~80m 2 / g, thereby enhancing the activity of the catalyst.

[0016] Optionally, the oxygen vacancy concentration is determined by Ce 3+ / (Ce 3+ +Ce 4+ ) indicates that Ce in the Cu-Fe-based spinel catalyst 3+ / (Ce 3+ +Ce 4+ )≥30%, with enhanced oxygen vacancy content to increase the adsorption and activation capacity of CO2 and H2.

[0017] The present invention also discloses a method for preparing the Cu-Fe-based spinel catalyst as described above, comprising the following steps:

[0018] (1) Using metal salts of Cu, Fe and Ce as raw materials, dissolving them in ethanol to form a uniform mixed solution;

[0019] (2) adding oxalic acid ethanol solution dropwise to the mixed solution, reacting at 70° C. to 90° C. for 2 h to 4 h, then standing and aging at room temperature, washing and drying the solid separated after standing, to obtain a precursor;

[0020] (3) calcining the precursor at 400° C. to 500° C. for 4 h to 5 h to obtain the Cu-Fe-based spinel catalyst.

[0021] Optionally, in step (1), the metal salt includes at least one of nitrate, sulfate, acetate and chloride.

[0022] In step (2), the standing aging time is 48 h to 72 h; the drying temperature is 110° C. to 150° C.; and the concentration of the oxalic acid ethanol solution is 0.2 mol / L.

[0023] Optionally, in step (3), the calcination temperature is 450° C. and the calcination time is 4 hours to ensure the formation of the spinel structure and avoid excessive agglomeration of the metal oxides.

[0024] The present invention also discloses an application of the Cu-Fe-based spinel catalyst as described above in carbon dioxide hydrogenation reaction, carbon dioxide reduction reaction and greenhouse gas emission reduction.

[0025] Optionally, the step of using the Cu-Fe-based spinel catalyst for the carbon dioxide hydrogenation reaction includes: mixing CO2 and H2 in a volume ratio of 1:3, and reacting at a reaction temperature of 400K to 600K and a reaction pressure of 2MPa to 4MPa to prepare CH4 and CH3OH.

[0026] Optionally, the reaction temperature is preferably 553K and the reaction pressure is preferably 3MPa.

[0027] Optionally, the Cu-Fe-based spinel catalyst exhibits a CH4 selectivity of 30% to 40%, a CH3OH selectivity of 40% to 50%, and a CO selectivity of less than 20% in the reaction.

[0028] Optionally, the Cu-Fe-based spinel catalyst is used in a carbon dioxide reduction reaction with high selective conversion, and is particularly suitable for the synthesis of methane or methanol.

[0029] Optionally, the Cu-Fe-based spinel catalyst is used in greenhouse gas emission reduction to convert industrially generated CO2 gas into fuel or high value-added chemicals to achieve effective utilization of carbon resources.

[0030] Optionally, the Cu-Fe-based spinel catalyst is characterized by a high-pressure in-situ DRIFTS technique, and the m-HCOO* intermediate formed during the reaction can effectively promote the generation of CH4 and inhibit the generation of CO by-products.

[0031] Optionally, the Cu-Fe-based spinel catalyst x Fe y The O4 spinel structure can promote the adsorption and activation of CO2 and enhance the H2 dissociation efficiency in the CO2 hydrogenation reaction pathway by increasing the oxygen vacancy concentration.

[0032] Implementing the embodiments of the present invention will have the following beneficial effects:

[0033] The present invention provides a new type of Cu x Fe y / CeO2 catalyst overcomes the shortcomings of single Cu-based and Fe-based catalysts. By introducing Fe elements to form a CuFe2O4 spinel structure, the selectivity of methane (CH4) and methanol (CH3OH) in the CO2 hydrogenation process is significantly improved, overcoming the problem of excessive byproduct CO generation and poor stability of traditional Cu-based catalysts in CO2 hydrogenation reactions. Studies have shown that the Cu x Fe y / CeO2 catalyst has high activity, high selectivity and excellent stability in CO2 hydrogenation reaction, which is mainly reflected in the following aspects:

[0034] (1) High selectivity and low by-product generation

[0035] The Cu of the present invention x Fe y The CuFe2O4 / CeO2 catalyst achieved 38.7% CH4 selectivity and 48.9% CH3OH selectivity at 553K and 3MPa, while the selectivity of byproduct CO was less than 20%. This significant selectivity improvement is due to the synergistic effect of abundant oxygen vacancies and Fe species in the CuFe2O4 spinel structure, which optimizes the reaction pathway to preferentially generate CH4 and CH3OH from CO2 hydrogenation, thereby effectively reducing the generation of CO.

[0036] (2) Excellent CO2 and H2 adsorption activity

[0037] By introducing Fe into the Cu / CeO2 catalyst to form a CuFe2O4 structure, the generation of a large number of oxygen vacancies greatly improves the catalyst's ability to adsorb and activate CO2. At the same time, the presence of Fe enhances the adsorption and dissociation of H2 on the Cu surface, promotes the hydrogenation reaction, and further improves the activity and conversion efficiency of the catalyst. These characteristics ensure that Cu x Fe y / CeO2 catalyst can achieve efficient CO2 conversion with lower energy demand.

[0038] (3) Optimized reaction pathway

[0039] The CO2 hydrogenation reaction path changes significantly on the Cu-Fe / CeO2 catalyst of the present invention. Through high-pressure in-situ DRIFTS experiments, it was observed that the m-HCOO generated by the CuFe2O4 structure *The intermediates are easily hydrogenated to produce CH4 instead of CO in the reaction path, which is different from the reaction path of the traditional Cu / CeO2 catalyst. The introduction of Fe changes the kinetic and thermodynamic advantages of the reaction, making CO2 preferentially converted to CH4 instead of CO. This avoids the traditional Cu-based catalyst from easily generating a large amount of byproduct CO during the CO2 hydrogenation process, which affects the purity of the product and the efficiency of the reaction.

[0040] (4) Good stability and durability

[0041] The CuFe2O4 spinel structure gives the catalyst good resistance to sintering and deactivation, and can effectively inhibit the agglomeration of Cu and Fe species. Long-term high-temperature and high-pressure tests show that the selectivity and activity of the catalyst remain stable, indicating that it is suitable for long-term industrial applications. This feature makes Cu x Fe y / CeO2 catalysts show lower maintenance requirements and longer service life in industrial production, thereby reducing industrial operating costs.

[0042] (5) Potential industrial applications and environmental protection significance

[0043] The Cu of the present invention x Fe y / CeO2 catalyst provides an efficient and economical solution for the resource utilization of CO2. The catalyst is not only suitable for the synthesis of methane and methanol, but also can be used in related fields such as carbon capture and utilization (CCU) and carbon emission reduction. It is particularly suitable for the conversion and reuse of CO2 waste gas in the chemical and energy industries. This technology converts CO2 from a greenhouse gas into clean fuels and important chemical raw materials, providing a feasible technical means to achieve the goal of carbon neutrality.

[0044] (6) Economic benefits and sustainable development

[0045] The catalyst can show excellent CO2 conversion performance under low reaction temperature and pressure and low energy consumption conditions, greatly reducing energy consumption in industrial production processes. Its high efficiency and long life characteristics can not only significantly reduce the replacement and maintenance costs of the catalyst, but also improve the economic benefits of the reaction process. By converting CO2 into high-value-added chemicals and fuels, the present invention provides a new way for sustainable energy utilization and helps promote the development of green chemical technology.

[0046] In summary, the Cu x Fe y / CeO2 catalysts show excellent performance in CO2 hydrogenation reactions and have broad application prospects in achieving efficient CO2 conversion, reducing greenhouse gas emissions and resource utilization. The introduction of CuFe2O4 spinel structure successfully solves the main defects of traditional Cu-based catalysts, making it have important technical value and application potential in the fields of industrial carbon emission reduction and clean energy production. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 The X-ray diffraction (XRD) pattern of the CuFe2 / CeO2 catalyst of the present invention.

[0048] Figure 2 It is the H2-programmed temperature reduction (H2-TPR) spectra of the CuFe2 / CeO2 catalyst and the Cu / CeO2 catalyst of the present invention.

[0049] Figure 3 The Raman spectra of the CuFe2 / CeO2 catalyst and the Cu / CeO2 catalyst of the present invention are shown.

[0050] Figure 4 The figure is a comparison chart of CO2 conversion rate, activation energy and selectivity of the CuFe2 / CeO2 catalyst of the present invention and the Cu / CeO2 catalyst at different temperatures.

[0051] Figure 5 This is a graph showing the results of a 100-hour stability test of the CuFe2 / CeO2 catalyst of the present invention at 553K and 3MPa.

[0052] Figure 6 This is a high-pressure in-situ DRIFTS spectrum of the reaction intermediates formed on the surface of the CuFe2 / CeO2 catalyst during the CO2 hydrogenation process of the present invention.

[0053] Figure 7 These are the DFT calculation results of different intermediates of the CuFe2 / CeO2 catalyst of the present invention in the CO2 hydrogenation reaction. DETAILED DESCRIPTION

[0054] The present invention is further described below in conjunction with specific embodiments, but the present invention is not limited in any way.

[0055] The invention discloses a Cu-Fe-based spinel catalyst suitable for CO2 resource recovery. The Cu-Fe-based spinel catalyst comprises a carrier and a metal oxide loaded on the carrier; the carrier is CeO2; the metal oxide comprises CuO and Cu x Fe y O4 composite oxide, among which Cu x Fe y O4 composite oxide has a spinel structure.

[0056] Specifically, the Cu x Fe y / Structure and composition of CeO2 catalyst:

[0057] (1) Active ingredients

[0058] The Cu of the present invention x Fe y The main active components of the / CeO2 catalyst are CuO, CuFe2O4 and CeO2. CuO is the active center of the CO2 hydrogenation reaction, and the introduction of Fe makes Cu x Fe y The O4 spinel structure can be formed and exist stably. This spinel structure provides additional oxygen vacancies and promotes the adsorption and activation of H2. In addition, CeO2, as a reducible oxide, contributes to the generation and stability of oxygen vacancies, enhancing the activity and life of the catalyst.

[0059] (2) Advantages of spinel structure

[0060] Cu x Fe y The O4 spinel structure not only improves the dispersibility of Cu, making the Cu species evenly distributed on the CeO2 carrier in the form of nanoparticles, but also provides a high concentration of oxygen vacancies. The increase in oxygen vacancies can significantly improve the adsorption and activation ability of CO2, making CO2 more easily activated and reacting with H2, thereby optimizing the hydrogenation path of CO2 and reducing the generation of CO byproducts. In addition, Cu x Fe y The Fe species in O4 further improve the electron distribution on the Cu surface, making the adsorption of H2 by the catalyst more efficient, thus enhancing the overall efficiency of the reaction.

[0061] In one embodiment, the structure of the Cu-Fe-based spinel catalyst is Cu x Fe y / CeO2; wherein the molar ratio of Cu element to Fe element in the Cu-Fe-based spinel catalyst is x / y=1 / 2; the mass percentage of the total mass of the Fe element to the total mass of the Cu-Fe-based spinel catalyst is 7.5%.

[0062] In one embodiment, the CuO and Cu in the Cu-Fe-based spinel catalyst x Fe y The O4 composite oxides are all nanoparticles.

[0063] In one embodiment, CuO and Cu x Fe yThe particle sizes of the O4 composite oxides are 5nm to 20nm, which greatly improves the overall activity of the catalyst and enables better contact with CO2 and H2 molecules during the reaction.

[0064] In one embodiment, the catalyst has a spinel structure of Cu x Fe y The formation of O4 composite oxides increases the dispersibility of CuO, resulting in a Cu-Fe-based spinel catalyst with a specific surface area of ​​70 m 2 / g~80m 2 / g, which is beneficial to provide more active sites.

[0065] In one embodiment, the oxygen vacancy concentration is determined by Ce 3+ / (Ce 3+ +Ce 4+ ) indicates that Ce in Cu-Fe-based spinel catalysts 3+ / (Ce 3+ +Ce 4+ )≥30%, with enhanced oxygen vacancy content to increase the adsorption and activation capacity of CO2 and H2.

[0066] The present invention also discloses a method for preparing the Cu-Fe-based spinel catalyst as described above, which is prepared by a coprecipitation method and comprises the following steps:

[0067] (1) Metal salts of Cu, Fe and Ce are used as raw materials and dissolved in ethanol to form a uniform mixed solution.

[0068] In a specific embodiment, in step (1), the metal salt includes at least one of nitrate, sulfate, acetate, and chloride, preferably Cu(NO3)2·3H2O, Fe(NO3)3·6H2O, and Ce(NO3)3·6H2O.

[0069] Specifically, by mixing the metal salt in the ethanol solution, the metal ions are ensured to be fully dispersed, thereby forming a uniform precipitate.

[0070] (2) Add oxalic acid ethanol solution dropwise to the mixed solution, react at 70° C. to 90° C. for 2 h to 4 h, then stand at room temperature for aging, and wash and dry the solid separated after standing to obtain a precursor.

[0071] In step (2), the standing aging time is 48 h to 72 h to allow the initial formation of the crystal structure; the drying temperature is 110° C. to 150° C. to ensure complete dehydration of the precipitate; and the concentration of the oxalic acid ethanol solution is 0.2 mol / L.

[0072] Specifically, oxalic acid is used as a precipitant and Cu 2+ and Fe3+ The metal ions react to form oxalate precipitates, forming the precursor of the Cu-Fe-Ce complex. This process ensures that Cu and Fe are evenly distributed at the nanoscale, thereby enhancing the activity and stability of the final catalyst.

[0073] (3) The precursor is calcined at 400°C to 500°C for 4h to 5h to obtain a Cu-Fe-based spinel catalyst.

[0074] In a specific embodiment, in step (3), the calcination temperature is 450° C. and the calcination time is 4 hours to ensure the formation of the spinel structure and avoid excessive agglomeration of the metal oxides.

[0075] Specifically, during the calcination process, the oxalates of Cu, Fe, and Ce decompose to form CuO, Fe2O3, and CeO2, which further form a CuFe2O4 spinel structure through a solid phase reaction. The formation of this spinel structure is crucial for the active dispersion of Cu and the generation of oxygen vacancies, significantly improving the performance of the catalyst.

[0076] The present invention also discloses an application of the Cu-Fe-based spinel catalyst as described above in carbon dioxide hydrogenation reaction, carbon dioxide reduction reaction and greenhouse gas emission reduction.

[0077] In a specific embodiment, the steps of using a Cu-Fe-based spinel catalyst for the carbon dioxide hydrogenation reaction include: mixing CO2 and H2 in a volume ratio of 1:3, reacting at a reaction temperature of 400K to 600K and a reaction pressure of 2MPa to 4MPa to prepare CH4 and CH3OH.

[0078] In a specific embodiment, the reaction temperature is preferably 553 K, and the reaction pressure is preferably 3 MPa. Specifically, under these conditions, the catalyst exhibits excellent selectivity for CH4 and CH3OH, and the proportion of CO byproducts is significantly reduced.

[0079] In a specific embodiment, the Cu-Fe-based spinel catalyst exhibits a CH4 selectivity of 30% to 40% (about 38.7%), a CH3OH selectivity of 40% to 50% (about 48.9%), and a CO selectivity of less than 20% in the reaction. This shows that by introducing the Fe element into the Cu / CeO2 catalyst, not only the reaction path is optimized, making the CH4 generation more advantageous, but also the generation of the byproduct CO is suppressed to a certain extent.

[0080] In a specific embodiment, the Cu-Fe-based spinel catalyst is used in the carbon dioxide reduction reaction, has a high selective conversion, and is particularly suitable for the synthesis of methane or methanol.

[0081] In a specific embodiment, the Cu-Fe-based spinel catalyst is used in greenhouse gas emission reduction to convert industrially generated CO2 gas into fuel or high value-added chemicals to achieve effective utilization of carbon resources.

[0082] The following are specific embodiments

[0083] Example 1

[0084] The preparation method of the CuFe2 / CeO2 catalyst of the present embodiment comprises the following steps:

[0085] 1.1 Prepare the precursor solution: weigh Cu(NO3)2·3H2O, Fe(NO3)3·6H2O and Ce(NO3)3·6H2O, with a Cu / Fe molar ratio of 1:2 and a Ce(NO3)3·6H2O mass percentage of 35%, and dissolve each component in anhydrous ethanol to obtain a uniformly mixed ethanol solution.

[0086] 1.2 Precipitation reaction: 0.2 mol / L oxalic acid ethanol solution was added dropwise to the mixed ethanol solution and stirred at 70°C for 2 hours to ensure sufficient precipitation reaction. The role of oxalic acid ethanol solution is to induce the co-precipitation reaction of Cu, Fe and Ce to form the precursor of Cu-Fe / CeO2.

[0087] 1.3 Aging and treatment: After the reaction was completed, the obtained precipitate was aged for 48 hours to improve the crystallinity of the precursor. Subsequently, the precipitate was vacuum filtered and washed with deionized water several times to remove unreacted impurities, and finally dried at 110°C overnight.

[0088] 1.4 Calcination: The dried sample was placed in a muffle furnace and calcined at 450°C in air atmosphere for 4 hours. During the calcination process, the oxides of Cu, Fe and Ce gradually formed a CuFe2O4 spinel structure, combined with the CeO2 support, and finally formed a CuFe2 / CeO2 catalyst with high activity and selectivity.

[0089] 2. Catalytic performance test

[0090] 2.1 Experimental setup: The catalytic reaction was carried out in a fixed bed reactor, using a stainless steel reaction tube with an inner diameter of 20 mm as the reactor. Quartz wool was filled at both ends of the reactor to fix the catalyst and ensure that the reaction gas passed through the catalyst bed evenly.

[0091] 2.2 Catalyst pretreatment: Before the reaction, 0.5 g of the prepared CuFe2 / CeO2 catalyst was loaded into the reaction tube and pretreated at 300 °C with a pure hydrogen flow of 50 mL / min for 3 h to activate the active sites on the catalyst surface.

[0092] 2.3 Reaction conditions: A mixture of CO2 and H2 (volume ratio 1:3) was introduced into the reactor at a flow rate of 60 mL / min, the reaction temperature was set at 553 K, and the pressure was 3 MPa. After the reaction stabilized, the product was analyzed by online gas chromatography every 2 h to ensure the accuracy and repeatability of the data.

[0093] 2.4 Product analysis: The concentrations of CO2 and CO were analyzed by gas chromatograph with a thermal conductivity detector (TCD), and the yields of CH4 and CH3OH were analyzed by flame ionization detector (FID) and capillary column. The average value of each set of experimental data was taken, and the CO2 conversion rate and the selectivity of CH4, CH3OH and CO were calculated.

[0094] Comparative Example 1

[0095] The preparation method of Cu / CeO2 used in this comparative example comprises the following steps:

[0096] Prepare the precursor solution: weigh Cu(NO3)2·3H2O and Ce(NO3)3·6H2O, dissolve the components in anhydrous ethanol at a molar ratio of 1:1 to obtain a uniformly mixed ethanol solution.

[0097] The precipitation reaction, aging, treatment and calcination in Example 1 are followed to obtain the Cu / CeO2 of this comparative example.

[0098] Test Case

[0099] 1.1.1 Experimental verification

[0100] In order to verify the performance of the CuFe2 / CeO2 catalyst of Example 1 in the CO2 hydrogenation process, the experiment was studied in detail from the aspects of catalyst structure characterization, CO2 hydrogenation reaction test, product distribution analysis and reaction path mechanism verification. The experimental results show that the CuFe2 / CeO2 catalyst of the present invention exhibits excellent selectivity, activity and stability in the process of CO2 hydrogenation to methane (CH4) and methanol (CH3OH).

[0101] 1. Structural characterization of catalysts

[0102] 1.1 X-ray diffraction (XRD) analysis

[0103] The crystal phase composition and structure of CuFe2 / CeO2 catalyst were analyzed by X-ray diffraction (XRD). Figure 1The results show that the spinel structure diffraction peaks of CuFe2O4 are clearly visible. The spinel structure of CuFe2O4 is successfully formed in the CuFe2 / CeO2 catalyst and is evenly distributed on the CeO2 support. At the same time, the typical crystal phase peaks of CeO2 (JCPDS 34-0394) and the diffraction peaks of CuO and CuFe2O4 are observed in the XRD spectrum, indicating that Cu and Fe have good dispersion on CeO2. The presence of the spinel structure of CuFe2O4 provides a structural basis for the high activity and selectivity of the catalyst.

[0104] 1.2 BET surface area and pore structure

[0105] The specific surface area (BET) and pore size distribution of CuFe2 / CeO2 catalyst were measured by N2 adsorption-desorption isotherm. The results showed that the specific surface area of ​​CuFe2 / CeO2 catalyst increased significantly compared with Cu / CeO2, reaching 78.2 m 2 / g, this increased surface area helps to increase the number of catalytic active sites, thereby improving the catalytic activity.

[0106] 1.3H2-TPR analysis

[0107] H2-TPR experiment was used to analyze the reducibility of CuFe2 / CeO2 catalyst. The experimental results showed that Figure 2 As shown in the figure, the CuFe2 / CeO2 catalyst exhibits multiple reduction peaks in the range of 200-500℃, corresponding to the reduction reactions of highly dispersed CuO, CuFe2O4 and Fe species. Compared with the Cu / CeO2 catalyst, the intensity of the reduction peak in CuFe2 / CeO2 is significantly increased, indicating that the introduction of Fe improves the reducibility of the catalyst and is beneficial to the adsorption and activation of CO2 and H2.

[0108] 1.4 Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) analysis

[0109] Raman and XPS tests show that the CuFe2 / CeO2 catalyst surface contains a high concentration of oxygen vacancies. Figure 3 As shown, the Raman spectrum at 450 cm -1 CeO2 F is shown nearby 2g The peak intensity related to oxygen vacancies is significantly enhanced on the CuFe2 / CeO2 catalyst, indicating that the introduction of the CuFe2O4 structure increases the concentration of oxygen vacancies. These oxygen vacancies play an important role in the adsorption and activation of CO2, thereby improving the overall performance of the catalyst. 3+ / (Ce 3+ +Ce 4+) reaches 37.8%, further proving that the introduction of Fe helps to form oxygen vacancies, which enhance the adsorption and activation ability of CO2.

[0110] 2.CO2 hydrogenation reaction test

[0111] 2.1 Reaction conditions setting

[0112] The CO2 hydrogenation performance was tested in a fixed bed reactor. The reaction conditions were set at 553K temperature, 3MPa pressure, and a volume ratio of CO2 to H2 of 1:3. The reactor inlet flow rate was set at 60mL min -1 Before the reaction activity test, the catalyst was heated at 300 °C for 50 mL min -1 The catalyst was pretreated with pure H2 for 3 h to remove surface oxides and activate the catalyst.

[0113] 2.2 Product analysis method

[0114] The reaction products were analyzed by online gas chromatography (GC), where a thermal conductivity detector (TCD) was used to detect the concentrations of CO2 and CO, and a flame ionization detector (FID) was used to quantitatively analyze CH4 and CH3OH. Product distribution data were recorded every 2 h after reaching a stable reaction state to ensure the accuracy and repeatability of the results.

[0115] 3. Performance test results

[0116] 3.1CO2 conversion and product selectivity

[0117] like Figure 4 As shown in (a), (c) and (d), under the conditions of 553K and 3MPa, the CO2 conversion rate of the CuFe2 / CeO2 catalyst reached 15.4%, which is significantly improved compared with the traditional Cu / CeO2 catalyst. Analysis of the product distribution shows that the CH4 selectivity of the CuFe2 / CeO2 catalyst is 38.7%, the CH3OH selectivity is 48.9%, and the formation of the byproduct CO is effectively suppressed, with a selectivity of less than 20%. These results verify the significant effect of the CuFe2O4 spinel structure in optimizing the distribution of CO2 hydrogenation products.

[0118] 3.2 Reduction of reaction activation energy

[0119] like Figure 4 As shown in (b), by comparing the activation energies of CuFe2 / CeO2 and Cu / CeO2 catalysts, it is found that the activation energy of CuFe2 / CeO2 is 27.3 kJ·mol -1 , which is significantly lower than 29.4 kJ·mol of Cu / CeO2 -1This indicates that the CuFe2 / CeO2 catalyst can achieve CO2 hydrogenation reaction at a lower energy barrier, which helps to improve the reaction rate and product selectivity under low temperature conditions.

[0120] 3.3 Catalyst stability test

[0121] The stability test of CuFe2 / CeO2 catalyst was carried out for 100h. Figure 5 As shown, the results show that the CO2 conversion rate and product distribution maintain stable CO2 conversion rate and high selectivity in long-term reactions. After multiple cycles of reaction, the CH4 and CH3OH selectivities of the catalyst did not change significantly, indicating that the CuFe2O4 spinel structure can effectively inhibit the agglomeration of Cu and Fe species, making the catalyst exhibit excellent anti-deactivation ability under high temperature and high pressure conditions, indicating that it is suitable for long-term operation in industrial applications.

[0122] 4. Reaction path mechanism verification

[0123] 4.1 High-pressure in-situ DRIFTS analysis

[0124] High-pressure in-situ DRIFTS infrared spectroscopy was used to track the intermediate types and generation pathways of CO2 hydrogenation reactions under reaction conditions. Figure 6 As shown, HCOO was detected on the surface of CuFe2 / CeO2 catalyst. * , CH3O and other key intermediates, among which m-HCOO is formed on CuFe2 / CeO2 and further hydrogenated to CH4. In contrast, CO is the main intermediate on the traditional Cu / CeO2 catalyst. The introduction of CuFe2O4 structure effectively promotes the m-HCOO * The formation of CO was inhibited and the formation of CO was suppressed, which verified the important role of Fe in optimizing the reaction path. At the same time, the formation path of CH3OH on the catalyst surface was similar to that of Cu / CeO2, both passing through the bi-HCOO intermediate, but the CuFe2O4 structure suppressed the formation of CO. This result verified the reaction path optimization effect of CuFe2 / CeO2 catalyst in the CO2 hydrogenation process.

[0125] 4.2 Density functional theory (DFT) calculations

[0126] Combined with DFT calculations, the reaction path and energy changes of CuFe2 / CeO2 catalysts were simulated, such as Figure 7 As shown in Figure 2, the adsorption energy of CO2 and H2 on CuFe2O4 structure is significantly increased, and the activation energy of the reaction to generate CH4 is reduced. DFT calculations also show that m-HCOO *It is a key intermediate in the production of CH4, while CO is not easy to exist stably on the CuFe2 / CeO2 catalyst, thus reducing the production of CO byproducts. The above calculation results are consistent with the experimental data, indicating that the introduction of Fe enhances the thermodynamic and kinetic advantages of CH4 production through structural regulation, further verifying the high selectivity of the CuFe2 / CeO2 catalyst in the CO2 hydrogenation process.

[0127] 5. Experimental verification conclusion

[0128] The experimental verification results show that the CuFe2 / CeO2 catalyst of the present invention exhibits significant performance advantages in the CO2 hydrogenation reaction to produce CH4 and CH3OH, with high selectivity, high activity and excellent stability:

[0129] (1) The CuFe2O4 spinel structure forms a large number of oxygen vacancies on the CeO2 support, which greatly enhances the adsorption capacity and activation efficiency of the catalyst surface for CO2, allowing CO2 molecules to be efficiently activated at a lower temperature. DRIFTS experiments have shown that the CuFe2 / CeO2 catalyst can generate stable HCOO during the CO2 hydrogenation process. * intermediates, thereby enhancing the reactivity of CO2.

[0130] (2) The introduction of Fe changes the reaction path, promoting the reaction intermediate m-HCOO * It is preferentially converted into CH4, thereby reducing the generation of CO and significantly improving product selectivity.

[0131] (3) The CuFe2 / CeO2 catalyst exhibits excellent stability in long-term high-temperature and high-pressure reactions, effectively preventing the agglomeration of Cu and Fe, maintaining the high activity and high selectivity of the catalyst, and is suitable for continuous operation on an industrial scale.

[0132] The above experimental verification clearly demonstrates the superior performance of the CuFe2 / CeO2 catalyst of the present invention in the production of CH4 and CH3OH by hydrogenation of CO2, which is specifically manifested in that at 553K and 3MPa, when reacting at a CO2 / H2 volume ratio of 1:3, the CH4 selectivity of the CuFe2 / CeO2 catalyst is significantly increased to 38.7%, the CH3OH selectivity reaches 48.9%, and the proportion of CO byproducts is significantly reduced, accounting for only 10.2% of the product. This selectivity improvement effect shows the potential of the CuFe2 / CeO2 catalyst in methane generation, and can be widely used in industrial production of carbon dioxide resource utilization, providing an efficient and sustainable catalytic material for realizing CO2 resource utilization.

[0133] The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the patent application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A Cu-Fe-based spinel catalyst suitable for CO2 resource recovery, characterized in that: The Cu-Fe-based spinel catalyst comprises a carrier and a metal oxide supported on the carrier; The metal oxides include CuO and Cu x Fe y O4 composite oxide, wherein the Cu x Fe y O4 composite oxide has a spinel structure; The carrier is CeO2.

2. The Cu-Fe-based spinel catalyst suitable for CO2 resource recovery according to claim 1, characterized in that: The structural formula of the Cu-Fe-based spinel catalyst is Cu x Fe y / CeO2; The molar ratio of Cu element to Fe element in the Cu-Fe-based spinel catalyst is x / y=1 / 2; the mass percentage of the total mass of Fe element to the total mass of the Cu-Fe-based spinel catalyst is 7.5%.

3. The Cu-Fe-based spinel catalyst suitable for CO2 resource recovery according to claim 1, characterized in that: The CuO and Cu in the Cu-Fe-based spinel catalyst x Fe y O4 composite oxides are all nanoparticles; The CuO and Cu x Fe y The particle size of each O4 composite oxide is 5 nm to 20 nm.

4. The Cu-Fe-based spinel catalyst suitable for CO2 resource recovery according to claim 1, characterized in that: The specific surface area of ​​the Cu-Fe-based spinel catalyst is 70 m 2 / g~80m 2 / g.

5. The Cu-Fe-based spinel catalyst suitable for CO2 resource recovery according to claim 1, characterized in that: Ce in the Cu-Fe-based spinel catalyst 3+ / (Ce 3+ +Ce 4+ )≥30%.

6. A method for preparing a Cu-Fe-based spinel catalyst suitable for CO2 resource recovery as claimed in any one of claims 1 to 5, characterized in that: The following steps are involved: (1) Using metal salts of Cu, Fe and Ce as raw materials, dissolving them in ethanol to form a uniform mixed solution; (2) adding oxalic acid ethanol solution dropwise to the mixed solution, reacting at 70° C. to 90° C. for 2 h to 4 h, then standing and aging at room temperature, washing and drying the solid separated after standing, to obtain a precursor; (3) calcining the precursor at 400° C. to 500° C. for 4 h to 5 h to obtain the Cu-Fe-based spinel catalyst.

7. The preparation method according to claim 6, characterized in that: In step (1), the metal salt includes at least one of nitrate, sulfate, acetate and chloride; In step (2), the standing aging time is 48 h to 72 h; the drying temperature is 110° C. to 150° C.; and the concentration of the oxalic acid ethanol solution is 0.2 mol / L.

8. The preparation method according to claim 6, characterized in that: In step (3), the calcination temperature is 450° C. and the calcination time is 4 hours.

9. Use of the Cu-Fe based spinel catalyst suitable for CO2 resource recovery as claimed in any one of claims 1 to 5 in carbon dioxide hydrogenation reaction, carbon dioxide reduction reaction and greenhouse gas emission reduction.

10. The use according to claim 9, characterized in that: The Cu-Fe-based spinel catalyst is used for the carbon dioxide hydrogenation reaction step comprising: CO2 and H2 are mixed in a volume ratio of 1:3, and reacted at a reaction temperature of 400K to 600K and a reaction pressure of 2MPa to 4MPa to prepare CH4 and CH3OH; The Cu-Fe-based spinel catalyst exhibits a CH4 selectivity of 30% to 40%, a CH3OH selectivity of 40% to 50%, and a CO selectivity of less than 20% in the reaction.

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