CO2 methanation catalyst as well as preparation method and application thereof

Abstract

The invention relates to a CO2 methanation catalyst and a preparation method and application thereof in the field of catalysts. The CO2 methanation catalyst comprises an active component, an optional auxiliary agent and a carrier. The active component can be selected from at least one of Ni, Fe and Co, the auxiliary agent can be selected from at least one of alkaline earth metal, transition metal or rare earth metal, and the carrier is a macroporous alumina carrier with high water absorption. The CO2 methanation catalyst is prepared by the following steps: impregnating components including active components and optional auxiliaries on a carrier by adopting an impregnation method, and then drying and roasting. According to the catalyst, under the action of the carrier, the dispersity of the active components is higher, the water absorption rate is higher, and the catalyst has good activity and can be used for CO2 methanation reaction.

Description

Technical Field

[0001] This invention relates to the field of catalysts, and more specifically, to a CO2 methanation catalyst, its preparation method, and its application. Background Technology

[0002] The rise in atmospheric CO2 concentration has led to global warming and various climate problems. Reducing atmospheric CO2 concentration and mitigating global warming has become a crucial challenge that humanity must face. In the short term, humans cannot drastically reduce their use of fossil fuels, so large-scale CO2 emissions will continue for a considerable period. Therefore, converting CO2 into fuels or chemicals is a promising strategy for CO2 utilization.

[0003] Current research on catalysts for CO2 methanation mainly focuses on Ni and Ru as active components. CN112138654A discloses a 3% Ru / TiZrMgAlO45 catalyst. x The catalyst can achieve 81% CO2 conversion and 100% CH4 selectivity at 310℃ under space velocities of 18000–24000 L / kg·h. CN111514889A discloses catalysts such as 1% Ru / TiO2 and 1% Ru / Al2O3, which achieve a space velocity of 2400 h⁻¹. -1 At 220℃, a CO2 conversion rate of about 40% can be obtained. Although Ru catalysts have high conversion rates and selectivity, Ru is a precious metal, and its high cost makes it difficult to achieve industrial application.

[0004] Ni, due to its relatively low price, shows promise for industrial applications. Currently, the main challenge with Ni-based catalysts is the high activation energy required, making it difficult to achieve high-conversion CO2 methanation at low temperatures. Patent CN112588292A discloses a Ni / TiO2 aerogel catalyst that achieves approximately 60% CO2 conversion and 97% methane selectivity at 450℃. Patent CN111318281A discloses a Ni / TiO2 catalyst that achieves 63.5% CO2 conversion at 360℃. He Feng et al. reported a Ni-Zr-Al catalyst with high catalytic activity, capable of converting CO2 to methane at 210℃ with a conversion rate of 80%. However, at high reaction temperatures, the active Ni metal is prone to sintering, loss, and carbon deposition, leading to catalyst deactivation and hindering long-term stable methanation reactions. Therefore, to further reduce the temperature of CO2 methanation, a highly active Ni catalyst needs to be developed. Summary of the Invention

[0005] To address the problems existing in the prior art, the present invention provides a CO2 methanation catalyst that can improve the metal-support interaction, enhance the hydrogenation activity of Ni, and reduce the CO2 hydrogenation temperature.

[0006] One objective of this invention is to provide a CO2 methanation catalyst, comprising an active component, optional promoters, and a macroporous alumina support, wherein the active component is selected from at least one of Ni, Fe, and Co, and the active metal dispersion is 4.0–6.0%; the promoters are selected from at least one of alkaline earth metals, transition metals, or rare earth metals; the macroporous alumina support has a water absorption rate higher than 180%, a pore size greater than 20 nm, and is θ and / or δ phase alumina, with a sulfur content of 0.01–0.2 wt%.

[0007] The alumina carrier has a layered structure and is alumina of θ and / or δ phases. That is, the alumina microspheres can be alumina of θ phase, alumina of δ phase, or a mixture of θ and δ phases. The mixture can be dominated by alumina of θ phase or alumina of δ phase.

[0008] Preferably, the water absorption rate of the alumina carrier is 180% to 300%, for example, it can be 180%, 200%, 220%, 240%, 260%, 280%, 300%, etc.

[0009] Preferably, the pore size of the alumina carrier is 20–50 nm.

[0010] Preferably, the sulfur content of the alumina carrier is 0.05-0.15%.

[0011] Based on a total catalyst content of 100 wt%, the content of metal oxides in the active component is 30–66 wt%, preferably 50–60 wt%; the content of metal oxides in the additive is 0–5 wt%, preferably 0–4 wt%. When additives are added, the content of metal oxides in the additives can be, for example, 0.1 wt%, 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, etc.

[0012] The alkaline earth metal may be selected from at least one of Be, Mg, Ca, Sr, and Ba, with at least one of Mg and Ca being preferred.

[0013] The transition metal may be selected from at least one of Sc, Ti, V, Cr, Mn, Mo, Cu, Zn, Ag, Cd, Au, and Pt, preferably at least one of Ti, Mn, Mo, Cu, Zn, and Ag.

[0014] The rare earth metal may be selected from at least one of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, with at least one of La, Ce, Pr, and Sm being preferred.

[0015] The catalyst described in this invention has good activity and the active components are more uniformly dispersed, and it can be used for CO2 methanation reaction.

[0016] The method for preparing the macroporous alumina carrier of the present invention preferably includes the following steps:

[0017] (1) Prepare a sodium aluminate solution by mixing sodium hydroxide and sodium aluminate;

[0018] (2) Sodium aluminate solution was added dropwise to aluminum sulfate solution to obtain boehmite precursor;

[0019] (3) Boehmite precursor was crystallized to obtain boehmite;

[0020] (4) Boehmite is shaped into sheets and then calcined at high temperature to obtain the alumina carrier.

[0021] In step (1), the molar ratio of sodium to aluminum in the sodium aluminate solution is (3-6):1, for example, it can be 3:1, 4:1, 5:1, 6:1, etc.

[0022] The solvent in the sodium aluminate solution is water, preferably deionized water.

[0023] In step (1), the concentration of aluminum ions in the sodium aluminate solution is 0.1 to 2.0 mol / L, for example, 0.1 mol / L, 0.2 mol / L, 0.4 mol / L, 0.6 mol / L, 0.8 mol / L, 1 mol / L, 1.2 mol / L, 1.5 mol / L, 1.8 mol / L, 2.0 mol / L, etc.

[0024] In step (2), the concentration of the aluminum sulfate solution is 0.1 to 1 mol / L, for example, it can be 0.1 mol / L, 0.2 mol / L, 0.4 mol / L, 0.6 mol / L, 0.8 mol / L, 1 mol / L, etc.

[0025] The solvent in the aluminum sulfate solution is water, preferably deionized water.

[0026] In step (2), sodium aluminate solution is added dropwise until the pH of the system is 8 to 11, for example, 8, 9, 10, 11, etc.

[0027] In step (2), sodium aluminate solution is added to aluminum sulfate solution by a peristaltic pump at a flow rate of 5-15 mL / min, preferably 10-13 mL / min.

[0028] In step (3), the crystallization conditions are: crystallization temperature of 50–120°C and crystallization time of 2–24 h. Preferably, the crystallization temperature is 60–100°C and the crystallization time is 5–20 h.

[0029] Step (3) may optionally include filtering and washing the crystallization solution after crystallization.

[0030] The specific surface area of ​​the boehmite obtained in step (3) is 200–600 cm². 2 / g.

[0031] In step (4), the calcination conditions are: calcination temperature of 900-1100℃ and calcination time of 4-10h. Preferably, the calcination temperature is 1000-1100℃ and the calcination time is 5-7h.

[0032] In step (4), the tableting process can be carried out by using a tablet press to press the boehmite powder into cylindrical granules with a size of about 0.3*0.5mm. Other forming methods can also be used, such as kneading and extruding, with tableting being the preferred method.

[0033] A second objective of this invention is to provide a method for preparing the CO2 methanation catalyst, comprising impregnating the macroporous alumina support in a solution containing an active component precursor compound and optionally an auxiliary precursor compound, followed by drying and calcination.

[0034] According to a preferred embodiment of the present invention, the methanation catalyst can be obtained by impregnation method, in which components including the soluble salts corresponding to the active components and the soluble salts corresponding to the auxiliary agents are impregnated on a macroporous alumina support according to the specified amount, followed by drying and calcination.

[0035] The active component precursor compound is selected from at least one of the soluble salts of Ni, Fe, and Co, and preferably from at least one of the nitrates and carbonates of Ni, Fe, and Co.

[0036] The precursor compound for the adjuvant is selected from at least one of the soluble salts of alkaline earth metals, transition metals, and rare earth metals, and preferably from at least one of the nitrates and carbonates of alkaline earth metals, transition metals, and rare earth metals.

[0037] The alkaline earth metal is selected from at least one of Be, Mg, Ca, Sr, and Ba, preferably from at least one of Mg and Ca; the transition metal is selected from at least one of Sc, Ti, V, Cr, Mn, Mo, Cu, Zn, Ag, Cd, Au, and Pt, preferably from at least one of Ti, Mn, Mo, Cu, Zn, and Ag; the rare earth metal is selected from at least one of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, preferably from at least one of La, Ce, Pr, and Sm.

[0038] In the preparation method, the solvent in the solution containing the active component precursor compound and the auxiliary agent precursor compound can be water, preferably deionized water. Dissolution is performed at maximum solubility, and the amount of solvent used is sufficient to completely dissolve the soluble salts corresponding to the active component and the auxiliary agent.

[0039] The impregnation method can be an equal-volume impregnation method, specifically by adding a solution containing an active component precursor compound and an optional auxiliary agent precursor compound to the carrier.

[0040] The drying conditions are: drying temperature of 60-140℃ and drying time of 2-10h.

[0041] The calcination conditions are as follows: calcination is carried out under a protective atmosphere; the calcination temperature is 300-450℃; and the calcination time is 2-6 hours.

[0042] A third objective of this invention is to provide the application of the CO2 methanation catalyst or the CO2 methanation catalyst obtained by the preparation method in the CO2 methanation reaction.

[0043] The reaction temperature is 200–300℃, and the reaction pressure is 0–3.0 MPa.

[0044] The CO2 methanation reaction in this invention can be carried out using the following technical solution: The methanation catalyst of this invention is loaded into a stainless steel fixed-bed reactor, high-purity nitrogen is introduced at a flow rate of 200-300 mL / min, and the temperature is raised to 120°C. The high-purity nitrogen is then switched to hydrogen at a flow rate of 200-300 mL / min, and the temperature is raised to 400-450°C and maintained for 4 hours. Then, the hydrogen is switched to the feed gas, and the reaction is carried out at different reaction temperatures of 200-300°C and at a reaction pressure of 0-3 MPa. The composition of the gas after the reaction is analyzed by an Agilent 7890 gas chromatograph.

[0045] The essential difference between this invention and the prior art lies in:

[0046] (1) In order to obtain a high loading catalyst, traditional supports usually need to be repeatedly impregnated multiple times. The support in this invention has a high water absorption rate and can achieve the loading of three to four conventional supports in one impregnation.

[0047] (2) The alumina support has a lamellar structure. Compared with granular alumina supports, the lamellar structure has more highly active defect sites at its edges, which helps to anchor the active metal. Furthermore, the (110) interplanar spacing of the lamellar alumina matches the interplanar spacing of Ni. During the growth of Ni on the support, lattice matching occurs, achieving strong anchoring between the support and the metal. Even with a high loading, a uniformly dispersed catalyst can still be obtained, preventing the active components from agglomerating and becoming deactivated during high-temperature calcination.

[0048] (3) The crystal phase of the alumina support is different from that of the traditional alumina support. The alumina support with θ and / or δ phases interacts with the active metal, which helps to improve the activity of the support.

[0049] The beneficial effects of this invention are:

[0050] 1) The catalyst has high activity. Under the same reaction conditions, the CO2 removal temperature can reach 230℃, which significantly reduces the reaction temperature, extends the catalyst life, and also achieves the effect of energy saving and consumption reduction.

[0051] 2) Traditional catalyst supports require three or even four calcinations to achieve the desired loading, while the catalyst of this invention can achieve it in one step, effectively reducing the number of calcinations and lowering the production cost of the catalyst.

[0052] 3) The special structure of the catalyst results in high dispersion of active metal. The metal dispersion of traditional catalysts is 3.9%, while the dispersion of active components in the catalyst of this invention can be 5.2%, which is higher than that of catalysts prepared by traditional methods. Attached Figure Description

[0053] Figure 1 This is a scanning electron microscope image of the macroporous alumina support obtained in Example 1. Detailed Implementation

[0054] The present invention will now be described in detail with reference to specific embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Any improvements and adjustments made by those skilled in the art based on the content of the present invention that are not part of this invention shall still fall within the scope of protection of the present invention.

[0055] Unless otherwise specified, the raw materials used in the examples and comparative examples are all disclosed in the prior art, such as those that can be directly purchased or prepared according to the preparation methods disclosed in the prior art.

[0056] According to a preferred embodiment of the present invention, the preparation method of the CO2 methanation catalyst may specifically include the following steps:

[0057] (1) Prepare a sodium aluminate solution by mixing sodium hydroxide and sodium aluminate;

[0058] (2) Sodium aluminate solution was added dropwise to aluminum sulfate solution to obtain boehmite precursor;

[0059] (3) Boehmite precursor is crystallized to obtain boehmite with a large specific surface area;

[0060] (4) Boehmite with a large specific surface area is shaped into sheets and then calcined at high temperature to obtain alumina with a large specific surface area.

[0061] (5) The alumina is impregnated in a solution containing the active component precursor compound and optional auxiliary precursor compound, and then dried and calcined to obtain the methanation catalyst.

[0062] In the following embodiments:

[0063] The dispersion of the active component was obtained by testing the metal dispersion using a chemisorption analyzer.

[0064] Example 1

[0065] (1) Weigh 22.56g NaOH and 17.5g sodium aluminate and dissolve them in 250ml deionized water for later use.

[0066] (2) Weigh 88.4g of aluminum sulfate into 500ml of deionized water, add the sodium aluminate solution prepared in step 1) dropwise into the aluminum sulfate solution with a concentration of 0.5mol / L until the pH is 9.0, the flow rate is 12.1mL / min, and stir at room temperature for 60min to obtain boehmite precursor.

[0067] (3) Continue crystallization at 80℃ for 10h to obtain boehmite with a large specific surface area.

[0068] (4) Use a tablet press to press the boehmite into cylindrical pellets of 5mm*3mm.

[0069] (5) The obtained boehmite with a large specific surface area was calcined at 1100℃ for 6 hours in air to obtain macroporous alumina. BET characterization showed that the pore size of the macroporous alumina was distributed in the range of 20-40 nm, the water absorption rate was 220%, and the sulfur content of the carrier was 0.08 wt%.

[0070] (6) Dissolve 54g of nickel nitrate in 26mL of deionized water and stir until homogeneous. Load the solution onto 12g of a macroporous alumina support using an equal-volume impregnation method. Dry the impregnated product in an oven at 120℃ for 2 hours. Then, place the dried product in a tube furnace and calcine it at 400℃ for 3 hours under a nitrogen atmosphere to obtain catalyst C1. The obtained catalyst C1 contains 54% NiO.

[0071] Example 2

[0072] (1)~(4) are the same as in Example 1.

[0073] (5) The obtained boehmite with a large specific surface area was calcined at 1000℃ for 6 hours in air to obtain macroporous alumina. BET characterization showed that the macroporous alumina had a pore size distribution of 25-40 nm, a water absorption rate of 240%, and a carrier sulfur content of 0.15 wt%.

[0074] (6) Dissolve 54g of nickel nitrate and 4g of magnesium nitrate in 29mL of deionized water and stir until homogeneous. Load the solution onto 12g of macroporous alumina support using an equal-volume impregnation method. Dry the impregnated product in an oven at 120℃ for 2 hours. Then, place the dried product in a tube furnace and calcine it at 400℃ for 3 hours under a nitrogen atmosphere to obtain catalyst C2. The obtained catalyst C2 contains 53% NiO and 2.4% MgO.

[0075] Example 3

[0076] (1)~(4) are the same as in Experiment 1.

[0077] (5) The obtained boehmite with a large specific surface area was calcined at 1050℃ for 6 hours in air to obtain macroporous alumina. BET characterization showed that the macroporous alumina had a pore size distribution of 25-40 nm, a water absorption rate of 230%, and a carrier sulfur content of 0.09 wt%.

[0078] (6) Dissolve 54g of nickel nitrate and 6g of magnesium nitrate in 28mL of deionized water and stir until homogeneous. Load the solution onto 12g of macroporous alumina support using an equal-volume impregnation method. Dry the impregnated product in an oven at 120℃ for 2 hours. Then, place the dried product in a tube furnace and calcine it at 400℃ for 3 hours under a nitrogen atmosphere to obtain catalyst C3. The obtained catalyst C3 contains 54% NiO and 3.5% MgO.

[0079] Example 4

[0080] (1) Weigh 22.56g NaOH and 17.5g sodium aluminate and dissolve them in 250ml deionized water for later use.

[0081] (2) Weigh 88.4g of aluminum sulfate into 500ml of deionized water, add the sodium aluminate solution prepared in step 1) dropwise into the aluminum sulfate solution with a concentration of 0.5mol / L until the pH is 9.5, the flow rate is 10.5mL / min, and stir at room temperature for 60min to obtain boehmite precursor.

[0082] (3) Continue crystallization at 80℃ for 10h to obtain boehmite with a large specific surface area.

[0083] (4) Use a tablet press to press the boehmite into cylindrical pellets of 5mm*3mm.

[0084] (5) The obtained boehmite with a large specific surface area was calcined at 1100℃ for 6 hours in air to obtain macroporous alumina. BET characterization showed that the macroporous alumina had a pore size distribution of 20-30 nm, a water absorption rate of 200%, and a carrier sulfur content of 0.08 wt%.

[0085] (6) Dissolve 54g of nickel nitrate in 24mL of deionized water and stir until homogeneous. Load the solution onto 12g of a macroporous alumina support using an equal-volume impregnation method. Dry the impregnated product in an oven at 120℃ for 2 hours. Then, place the dried product in a tube furnace and calcine it at 400℃ for 3 hours under a nitrogen atmosphere to obtain catalyst C4. The obtained catalyst C4 contains 54% NiO.

[0086] Comparative Example 1

[0087] (1) A commercially available alumina support was calcined at 1000℃ for 6 hours in air to obtain an alumina support with a mixed δ and θ crystalline phase. BET characterization showed that the specific surface area of ​​the calcined alumina support was 104 m². 2 / g, pore volume 0.6cm 3 / g, carrier water absorption rate 90%.

[0088] (2) Dissolve 20g of nickel nitrate hexahydrate and 0.6g of magnesium nitrate in 9mL of deionized water and stir until homogeneous. Impregnate the 10g alumina support using the equal volume impregnation method. Place the impregnated product in an oven at 100℃ and dry for 10 hours. Place the dried product in a tube furnace and calcine at 400℃ for 3 hours under a nitrogen atmosphere to obtain the catalyst product. Repeat the above operation 3 times to obtain a catalyst product with equivalent sample loading, NiO loading of 42% and MgO content of 3.2%.

[0089] Comparative Example 2

[0090] (1) Weigh 22.56g NaOH and 17.5g sodium aluminate and dissolve them in 250ml deionized water for later use.

[0091] (2) Weigh 88.4g of aluminum sulfate into 500ml of deionized water, add the sodium aluminate solution prepared in step 1) dropwise into the aluminum sulfate solution with a concentration of 0.5mol / L until the pH is 9.0, the flow rate is 12.1mL / min, and stir at room temperature for 60min to obtain boehmite precursor.

[0092] (3) Continue crystallization at 80℃ for 10h to obtain boehmite with a large specific surface area.

[0093] (4) Use a tablet press to press the alumina carrier into cylindrical particles of 5mm*3mm.

[0094] (5) The cylindrical particle carrier was immersed in a 5 wt% glucose solution (1 g of glucose was used), then transferred to a hydrothermal reactor and reacted at 100 °C for 10 h. After cooling and filtration, it was dried at 80 °C for 4 h, and then placed in a nitrogen atmosphere and calcined at 600 °C for 10 h to obtain the carrier (carbon-doped γ-alumina). The carrier was characterized by BET, and the pore size distribution was 5-12 nm. The water absorption rate was 120%, and the sulfur content in the carrier was not detected.

[0095] (6) Dissolve 20g of nickel nitrate in 14mL of deionized water and stir evenly. Impregnate the 20g of nickel nitrate onto 12g of carbon-doped alumina support using the equal volume impregnation method. Place the impregnated product in an oven and dry it at 120℃ for 2 hours. Then place the dried product in a muffle furnace and calcine it at 400℃ for 3 hours. Repeat the above operation 3 times to obtain the catalyst product with a NiO content of 45%.

[0096] Comparative Example 3

[0097] (1) Weigh 22.56g NaOH and 17.5g sodium aluminate and dissolve them in 250ml deionized water for later use.

[0098] (2) Weigh 88.4g of aluminum sulfate into 500ml of deionized water, add the sodium aluminate solution prepared in step 1) dropwise into the aluminum sulfate solution with a concentration of 0.5mol / L until the pH is 9.0, stir at room temperature for 60min to obtain boehmite precursor.

[0099] (3) Continue crystallization at 80℃ for 10h to obtain boehmite with a large specific surface area.

[0100] (4) Use a tablet press to press the alumina carrier into cylindrical particles of 5mm*3mm.

[0101] (5) The obtained boehmite with a large specific surface area was calcined at 600℃ for 6 hours in air to obtain macroporous γ-alumina. BET characterization showed that the macroporous alumina had a pore size distribution of 15-40 nm, a water absorption rate of 260%, and a carrier sulfur content of 2.1 wt%.

[0102] (6) Dissolve 54g of nickel nitrate in 26mL of deionized water and stir evenly. Impregnate the 12g alumina support using the equal volume impregnation method. Place the impregnated product in an oven at 120℃ and dry for 2 hours. Place the dried product in a tube furnace and calcine at 400℃ for 3 hours under a nitrogen atmosphere to obtain the catalyst product with a NiO content of 55%.

[0103] Table 1 below shows the crystal phases of alumina obtained by calcining boehmite obtained in steps (1) to (4) of Example 1 at different temperatures:

[0104] Table 1

[0105]

[0106] Test case

[0107] Methanation reaction performance test

[0108] 5 mL of catalyst was loaded into a stainless steel fixed-bed reactor. High-purity nitrogen was introduced at a flow rate of 300 mL / min, and the temperature was raised to 120 °C. The high-purity nitrogen was then switched to hydrogen at a flow rate of 200 mL / min, and the temperature was raised to 400 °C and maintained for 4 h. Then, the hydrogen was switched to the feed gas, and the reaction was carried out at a reaction pressure of 0–3.0 MPa. The composition of the gas after the reaction was analyzed by an Agilent 7890 gas chromatograph.

[0109] The catalysts prepared in Examples 1-4 and Comparative Examples 1-3 were evaluated according to the above evaluation method. Table 2 shows the detailed evaluation results (raw material gas composition: CO2 5%, H2 95%, by volume fraction).

[0110] Table 2 Evaluation results of catalysts for CO2 methanation reaction

[0111]

[0112] As can be seen from the results in Table 2, under the same conditions, the catalyst in the embodiments of the present invention has a higher CO2 methanation conversion rate than the comparative example, indicating that the catalyst has high activity and the catalyst in the embodiments has higher dispersion.

Claims

1. A CO2 methanation catalyst, comprising an active component, optional promoters, and a macroporous alumina support, wherein the active component is selected from at least one of Ni, Fe, and Co, the promoter is selected from at least one of alkaline earth metals, transition metals, or rare earth metals, the dispersion of the active component is 4.0–6.0%, the macroporous alumina support has a water absorption rate higher than 180%, a pore size greater than 20 nm, and is θ and / or δ phase alumina, with a sulfur content of 0.01–0.2%.

2. The CO2 methanation catalyst according to claim 1, characterized in that: The alkaline earth metal is selected from at least one of Be, Mg, Ca, Sr, and Ba, preferably at least one of Mg and Ca; and / or, The transition metal is selected from at least one of Sc, Ti, V, Cr, Mn, Mo, Cu, Zn, Ag, Cd, Au, and Pt, preferably at least one of Ti, Mn, Mo, Cu, Zn, and Ag; and / or, The rare earth metal is selected from at least one of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, with at least one of La, Ce, Pr, and Sm being preferred.

3. The CO2 methanation catalyst according to claim 1, characterized in that: The macroporous alumina carrier has a water absorption rate of 180-300%, a pore size of 20-50 nm, and a sulfur content of 0.05-0.15%.

4. The CO2 methanation catalyst according to claim 1, characterized in that: Based on a total catalyst content of 100 wt%, the content of metal element oxides in the active component is 30-66 wt%, preferably 50-60 wt%; the content of metal element oxides in the auxiliary agent is 0-5 wt%, preferably 0-4 wt%.

5. The CO2 methanation catalyst according to claim 1, characterized in that... The method for preparing the macroporous alumina carrier includes the following steps: (1) Prepare a sodium aluminate solution by mixing sodium hydroxide and sodium aluminate; (2) Sodium aluminate solution was added dropwise to aluminum sulfate solution to obtain boehmite precursor; (3) Boehmite precursor was crystallized to obtain boehmite; (4) Boehmite is shaped into sheets and then calcined at high temperature to obtain the macroporous alumina carrier.

6. The CO2 methanation catalyst according to claim 5, characterized in that: In step (1), the molar ratio of sodium to aluminum in the sodium aluminate solution is (3-6):1; and / or, In step (1), the concentration of aluminum ions in the sodium aluminate solution is 0.1–2 mol / L; and / or In step (2), the concentration of the aluminum sulfate solution is 0.1–1 mol / L; and / or, In step (2), the sodium aluminate solution is added dropwise to the aluminum sulfate solution at a flow rate of 5–15 mL / min, preferably 10–13 mL / min; and / or, In step (2), sodium aluminate solution is added dropwise until the pH of the system is 8 to 11.

7. The CO2 methanation catalyst according to claim 5, characterized in that: The crystallization conditions in step (3) are: a crystallization temperature of 50–120°C and a crystallization time of 2–24 h; preferably, a crystallization temperature of 60–100°C and a crystallization time of 5–20 h; and / or, The calcination conditions in step (4) are: calcination temperature of 900-1100℃ and calcination time of 4-10h; preferably, calcination temperature of 1000-1100℃ and calcination time of 5-7h.

8. A method for preparing a CO2 methanation catalyst according to any one of claims 1 to 7, comprising impregnating the macroporous alumina support in a solution containing an active component precursor compound and optionally an auxiliary agent precursor compound, followed by drying and calcination.

9. The method for preparing the CO2 methanation catalyst according to claim 8, characterized in that: The drying conditions are: drying temperature of 60–140℃, drying time of 2–10 hours; and / or, The calcination conditions are as follows: calcination is carried out under a protective atmosphere; the calcination temperature is 300-450℃, and the calcination time is 2-6 hours.

10. The use of the catalyst according to any one of claims 1 to 7 or the catalyst obtained by the preparation method according to any one of claims 8 to 9 in the CO2 methanation reaction.

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