A methanation catalyst, its preparation method and use

Abstract

The present application relates to the field of catalysts, in particular to a methanation catalyst and a preparation method and application thereof. The methanation catalyst comprises an active component, an auxiliary agent and a carbon-containing alumina carrier, wherein the metal elements in the active component can be selected from at least one of Ni, Fe and Co, the metal elements in the auxiliary agent can be selected from at least one of alkaline earth metals, transition metals and rare earth metals, and the carrier is a carbon-modified large specific surface area alumina. The methanation catalyst is obtained by impregnating the components including the active component and the auxiliary agent on the carrier and then drying and calcining. The catalyst carrier has higher dispersion of the active component and higher water absorption rate under the condition of lower metal loading, and the catalyst has good activity and can be used for methanation reaction.

Description

Technical Field

[0001] This invention belongs to the field of catalyst technology, specifically relating to a methanation catalyst, its preparation method, and its application. Background Technology

[0002] Methanation, the simplest reaction in the Fischer-Tropsch synthesis, is mainly used in the ethylene industry, ammonia synthesis, hydrogen purification, and coal gasification, aiming to convert CO into hydrogen. x Converted to methane, or CO impurities removed from the feed gas. x This achieves the purpose of purification. Methane, as one of the fossil fuels used in natural gas, is mainly used in the chemical and fuel industries. Its main component, methane, can be produced from syngas (CO). x It is obtained by catalytic conversion of hydrogen. As the simplest Fischer-Tropsch synthesis reaction, methanation has the advantages of high calorific value, high conversion rate, single product, and good economic benefits.

[0003] Currently, there is a wide variety of methanation catalysts on the market, which are basically composed of supports, promoters, and active components. Among these, the support, as a crucial component, acts as a dispersant, binder, or support for the main catalyst, forming the framework for supporting the main catalyst. The support primarily provides effective surface area and suitable pore structure, enhances the catalyst's mechanical strength, enables it to adapt to external changes, improves thermal conductivity, and provides additional active sites. The macroscopic structure of the catalyst, such as specific surface area, pore structure, porosity, and pore size distribution, has a significant impact on the catalyst's activity and selectivity, and this macroscopic structure is often determined by the support. The support plays a vital role in the preparation and catalytic performance of supported metal nanocatalysts. The support not only improves the dispersion of noble metal nanoparticles and stabilizes them to prevent aggregation, but also influences the catalytic performance of noble metal nanoparticles through electronic effects and steric hindrance effects. With in-depth research into the mechanisms of various catalytic reactions, the influence of the support on catalyst performance (activity, stability, selectivity, etc.) is known as the "support effect." The support effect has been extensively studied by researchers. Currently proven support effects include strong metal-support interaction (SMSI), charge transfer (CT), support participation in catalytic processes (interface effect), and support stabilization of metal clusters and single atoms. To meet the needs of strongly exothermic / endothermic reactions in industry, supports generally need to have large heat capacity and good thermal conductivity to allow for rapid transfer of reaction heat energy, avoiding localized overheating that could lead to catalyst sintering and deactivation or equipment damage. They can also prevent side reactions at high temperatures, thereby improving catalyst selectivity. Due to the acidity of its surface, alumina can cause a series of problems during reactions, such as side reactions, decreased activity, and carbon buildup. Therefore, reducing the acidity of the support surface to minimize side reactions has become a key focus of support research. Furthermore, the water absorption of the support is also crucial for catalysts. Active metals are usually loaded onto the support surface using impregnation methods. The higher the water absorption rate of the support, the more catalyst can be loaded; therefore, improving the water absorption rate of the support is also very important. Summary of the Invention

[0004] To overcome the problem of acidic support surface in existing technologies, reduce metal loading, and lower catalyst preparation costs, this invention provides a methanation catalyst, its preparation method, and its application. This invention uses carbon-containing alumina with a large specific surface area as a support, loading active components and additives, resulting in higher dispersion of active components, higher water absorption, and excellent catalyst activity.

[0005] One objective of this invention is to provide a methanation catalyst, comprising: a carbon-containing alumina support, and an active component and an auxiliary agent supported on the carbon-containing alumina support, wherein the specific surface area of ​​the carbon-containing alumina support is ≥300 m². 2 / g, pore size 10–30 nm, pore volume 1.0–2.5 cm³ 3 / g, with a water absorption rate of 100-180%, preferably, the specific surface area of ​​the carbon-containing alumina carrier is 320-460m². 2 / g, pore size 10–25 nm, pore volume 1.5–2.2 cm³ 3 / g, water absorption rate is 120-150%.

[0006] According to the present invention, the carbon-containing alumina support is obtained by calcining alumina with a large specific surface area after modification with a carbonizable compound. Preferably, the specific surface area of ​​the alumina with a large specific surface area is ≥300 m². 2 / g. The carbonizable compound is selected from at least one of glucose and sucrose; the amount of the carbonizable compound is 0.1–10 wt% of alumina with a large specific surface area, preferably 0.5–5 wt%.

[0007] According to the present invention, in the methanation catalyst:

[0008] The metal element in the active component is selected from at least one of Ni, Fe, and Co;

[0009] The metal element in the additive is selected from at least one of alkaline earth metals, transition metals, and rare earth metals. Preferably, the alkaline earth metal is selected from at least one of Be, Mg, Ca, Sr, and Ba, and more 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, and more 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, and more preferably from at least one of La, Ce, Pr, and Sm.

[0010] According to the present invention, in the methanation catalyst:

[0011] Based on a total amount of 100 wt% for the methanation catalyst, the content of metal elements in the active component is 5-45 wt%, preferably 14-40 wt%; the content of metal elements in the auxiliary agent is 0.1-10 wt%, preferably 0.5-5 wt%; and the content of the carbon-containing alumina support is 36-95 wt%, preferably 40-85 wt%.

[0012] The second objective of this invention is to provide a method for preparing the above-mentioned methanation catalyst, comprising: impregnating a carbon-containing alumina support precursor in a solution containing an active component precursor compound and an auxiliary precursor compound, drying and calcining the solution to obtain the methanation catalyst.

[0013] According to the present invention, the preparation method of the methanation catalyst specifically includes the following steps:

[0014] (1) Prepare a sodium aluminate solution by mixing sodium hydroxide and sodium aluminate;

[0015] (2) Sodium aluminate solution was added dropwise to aluminum sulfate solution to obtain boehmite precursor;

[0016] (3) Boehmite precursor is crystallized to obtain boehmite with a large specific surface area;

[0017] (4) Boehmite with a large specific surface area is roasted to obtain alumina with a large specific surface area.

[0018] (5) Add alumina with a large specific surface area to a solution of carbonizable compounds for contact reaction to obtain a carbon-containing alumina support precursor;

[0019] (6) The carbon-containing alumina support precursor is impregnated in a solution containing active component precursor compound and auxiliary precursor compound, and then dried and calcined to obtain the methanation catalyst.

[0020] According to the present invention, in the method for preparing the methanation catalyst:

[0021] In the sodium aluminate solution, the molar ratio of sodium to aluminum is (3-6):1;

[0022] The concentration of aluminum ions in the sodium aluminate solution is 0.1–1 mol / L;

[0023] The solvent in the sodium aluminate solution is water, preferably deionized water;

[0024] The concentration of the aluminum sulfate solution is 0.1–0.7 mol / L;

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

[0026] The carbonizable compound is selected from at least one of glucose and sucrose;

[0027] The concentration of the carbonizable compound solution is 0.1–10 wt%, preferably 0.1–5 wt%.

[0028] The solvent in the carbonizable compound solution is water, preferably deionized water;

[0029] The active component precursor compound is selected from at least one of the soluble salts of Ni, Fe, and Co, preferably from at least one of the nitrates of Ni, Fe, and Co;

[0030] The auxiliary precursor compound is selected from at least one of the soluble salts of alkaline earth metals, transition metals, and rare earth metals, preferably from at least one of the nitrates of alkaline earth metals, transition metals, and rare earth metals. Specifically, the alkaline earth metal nitrate is selected from at least one of the nitrates of Be, Mg, Ca, Sr, and Ba, preferably from at least one of the nitrates of Mg and Ca; the transition metal nitrate is selected from at least one of the nitrates of Sc, Ti, V, Cr, Mn, Mo, Cu, Zn, Ag, Cd, Au, and Pt, preferably from at least one of the nitrates of Ti, Mn, Mo, Cu, Zn, and Ag; and the rare earth metal nitrate is selected from at least one of the nitrates of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, preferably from at least one of the nitrates of La, Ce, Pr, and Sm.

[0031] In the solution containing the active component precursor compound and the auxiliary agent precursor compound, the solvent is water, preferably deionized water. There is no particular limitation on the amount of solvent used; the amount of solvent should be sufficient to completely dissolve both the active component precursor compound and the auxiliary agent precursor compound.

[0032] According to the present invention, in the method for preparing the methanation catalyst:

[0033] In step (2), sodium aluminate solution is added dropwise to aluminum sulfate solution until the pH is 8-11, and stirred at room temperature for 10-60 minutes.

[0034] In step (3), crystallization can be carried out using crystallization equipment and crystallization conditions commonly used in the field, such as hydrothermal crystallization. The crystallization conditions are: crystallization temperature of 50-120℃ and crystallization time of 2-24h.

[0035] Step (3) may optionally include filtering and washing the crystallization solution after crystallization to obtain boehmite with a large specific surface area.

[0036] In step (4), the roasting can be carried out using roasting equipment and roasting conditions commonly used in the field. For example, the roasting conditions are: roasting temperature of 400-600℃ and roasting time of 4-10h.

[0037] In step (5), the conditions for the contact reaction are: reaction temperature of 120-200℃ and reaction time of 2-15h.

[0038] Before immersing the carbon-containing alumina carrier precursor obtained in step (5) into a metal solution, it is first pressed into tablets. For example, a tablet press is used to press the carbon-containing alumina carrier precursor powder into cylindrical granules. The size of the carrier after molding can be adjusted according to actual needs.

[0039] The impregnation method in step (6) can be a commonly used impregnation method in the art, which can make the carbon-containing alumina carrier precursor completely impregnated in the solution containing the active component precursor compound and the auxiliary agent precursor compound. The equal volume impregnation method is preferred.

[0040] In step (6), the drying can be carried out using drying equipment and drying conditions commonly used in the field. For example, the drying conditions are: drying temperature of 60 to 140°C and drying time of 2 to 10 hours.

[0041] In step (6), the roasting can be carried out using roasting equipment and roasting conditions commonly used in the field. For example, the roasting conditions are: roasting is carried out under a protective atmosphere, such as nitrogen; the roasting temperature is 300-450℃ and the roasting time is 2-6h.

[0042] A third objective of this invention is to provide an application of the above-described methanation catalyst, or the methanation catalyst prepared by the above-described method, in a methanation reaction. This invention utilizes a carbon-containing alumina support with a large specific surface area, which effectively improves the dispersion of the active metal component and enhances the catalyst activity. The catalyst of this invention is suitable for methanation reactions in the ethylene industry, as well as methanation reactions in the coal gasification or fertilizer industries, and is preferably used in the methanation reaction in the ethylene industry.

[0043] The methanation reaction in this invention can employ a commonly used methanation process in the art. For example, the following technical solution can be used: the methanation catalyst provided by 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, the temperature is raised to 120°C, the high-purity nitrogen is switched to hydrogen at a flow rate of 200-300 mL / min, 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 a reaction temperature of 150-250°C and a reaction pressure of 3.0-3.5 MPa. The composition of the gas after the reaction is analyzed by an Agilent 7890 gas chromatograph.

[0044] The beneficial effects of this invention are:

[0045] (1) Conventional catalysts cannot achieve high loading of active metals due to the water absorption rate of conventional supports. The water absorption rate of the support in this invention is significantly higher than that of conventional supports.

[0046] (2) Because the carbon-containing alumina carrier provided by the present invention has a large pore volume and a high specific surface area, CO inlet removal can be achieved with a low metal loading, which reduces the metal loading and reduces experimental costs.

[0047] (3) The carbon loaded on the surface of the alumina support adjusts the acidity of the catalyst support, inhibits the formation of carbon deposits, is conducive to anchoring the active metal, avoids the aggregation of active components during high-temperature calcination, and improves the dispersion of active metal.

[0048] (4) Traditional alumina requires kneading and extrusion molding. The alumina with a large specific surface area provided by the present invention does not require traditional kneading and extrusion because the surface is carbon-doped. It only needs to be pressed to prepare the catalyst support, which simplifies the preparation process and avoids the problem of reduced specific surface area during support molding. Detailed Implementation

[0049] 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.

[0050] 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.

[0051] Example 1

[0052] (1) Weigh 22.56g NaOH and 17.5g sodium aluminate and dissolve them in 250ml deionized water for later use.

[0053] (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.

[0054] (3) Continue crystallization at 80℃ for 10h to obtain boehmite with a large specific surface area.

[0055] (4) The obtained boehmite with a large specific surface area was calcined at 600°C for 6 hours in an air atmosphere to obtain alumina with a large specific surface area.

[0056] (5) 100g of alumina with a large specific surface area was immersed in a 1.5wt% glucose aqueous solution (1g of glucose was used), then transferred to a hydrothermal reactor and reacted at 180℃ for 10h. After cooling and filtration, the mixture was dried at 80℃ for 4h to obtain a carbon-containing alumina support. BET characterization showed that the specific surface area of ​​the carbon-containing alumina support was 350m². 2 / g, pore volume 1.5cm 3 / g.

[0057] (6) Use a tablet press to press the carbon-containing alumina carrier into cylindrical particles of 5mm*3mm.

[0058] (7) Dissolve 20g of nickel nitrate in 12mL of deionized water and stir until homogeneous. Dissolve 2g of magnesium nitrate in 5mL of deionized water and stir until homogeneous. Mix the two solutions and stir until homogeneous. Load the mixture onto a carbon-containing alumina support using an equal-volume impregnation method. Place the impregnated product in an oven and dry at 120°C for 2 hours. Then, place the dried product in a tube furnace and calcine at 400°C for 3 hours under a nitrogen atmosphere to obtain catalyst C1. The obtained catalyst C1 contains 30% Ni and 4.5% Mg.

[0059] Example 2

[0060] (1) to (6) are the same as in Example 1.

[0061] (7) Dissolve 15g of nickel nitrate in 12mL of deionized water and stir until homogeneous. Dissolve 2g of magnesium nitrate in 8mL of deionized water and stir until homogeneous. Mix the two solutions and stir until homogeneous. Load the mixture onto a carbon-containing alumina support using an equal-volume impregnation method. Place the impregnated product in an oven and dry at 120°C for 2 hours. Then, place the dried product in a tube furnace and calcine at 400°C for 6 hours under a nitrogen atmosphere to obtain catalyst C2. The obtained catalyst C2 contains 28% Ni and 3.0% Mg.

[0062] Example 3

[0063] (1)~(6) are the same as in Experimental Example 1.

[0064] (7) Dissolve 25g of nickel nitrate in 20mL of deionized water and stir until homogeneous. Dissolve 2g of magnesium nitrate in 5mL of deionized water and stir until homogeneous. Mix the two solutions and stir until homogeneous. Load the mixture onto a carbon-containing alumina support using an equal-volume impregnation method. Place the impregnated product in an oven and dry at 120°C for 2 hours. Then, place the dried product in a tube furnace and calcine at 400°C for 6 hours under a nitrogen atmosphere to obtain catalyst C3. The obtained catalyst C3 contains 34% Ni and 4.0% Mg.

[0065] Example 4

[0066] (1) to (6) are the same as in Example 1.

[0067] (7) Dissolve 20g of nickel nitrate in 12mL of deionized water and stir until homogeneous. Dissolve 2g of manganese nitrate in 5mL of deionized water and stir until homogeneous. Mix the two solutions and stir until homogeneous. Load the mixture onto a carbon-containing alumina support using an equal-volume impregnation method. Place the impregnated product in an oven and dry at 110°C for 2 hours. Then, place the dried product in a tube furnace and calcine at 400°C for 6 hours under a nitrogen atmosphere to obtain catalyst C4. The obtained catalyst C4 contains 30% Ni and 3.9% Mn.

[0068] Example 5

[0069] (1) to (6) are the same as in Example 1.

[0070] (7) Dissolve 10g of nickel nitrate in 12mL of deionized water and stir until homogeneous. Dissolve 0.5g of cobalt nitrate in 3mL of deionized water and stir until homogeneous. Mix the two solutions and stir until homogeneous. Load the mixture onto an alumina support using an equal-volume impregnation method. Place the impregnated product in an oven and dry at 100°C for 2 hours. Then, place the dried product in a tube furnace and calcine at 400°C for 6 hours under a nitrogen atmosphere to obtain catalyst C5. The obtained catalyst C5 contains 16% Ni and 1.0% Co.

[0071] Example 6

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

[0073] (5) 100g of the high specific surface area boehmite obtained in the preparation example was impregnated in a 5wt% sucrose aqueous solution (where the amount of sucrose was 2g), then transferred to a hydrothermal reactor and reacted at 180℃ for 10h. After cooling and filtration, it was dried at 80℃ for 4h, and then placed in a nitrogen atmosphere and calcined at 400℃ for 10h to obtain the support (carbon-doped alumina). By BET characterization, the specific surface area of ​​the alumina with a high specific surface area was 320m². 2 / g, pore volume 1.5cm 3 / g.

[0074] (6) Use a tablet press to press the large specific surface area alumina powder into cylindrical particles of 5mm*3mm.

[0075] (7) Dissolve 20g of nickel nitrate in 12mL of deionized water and stir until homogeneous. Dissolve 2g of magnesium nitrate in 5mL of deionized water and stir until homogeneous. Mix the two solutions and stir until homogeneous. Load the mixture onto an alumina support using an equal-volume impregnation method. Place the impregnated product in an oven and dry at 120°C for 2 hours. Then, place the dried product in a tube furnace and calcine at 400°C for 6 hours under a nitrogen atmosphere to obtain catalyst C6. The obtained catalyst C6 contains 30% Ni and 4.4% Mg.

[0076] Comparative Example 1

[0077] Dissolve 20g of nickel nitrate in deionized water and stir until homogeneous. Dissolve 2g of magnesium nitrate in deionized water and stir until homogeneous. Mix the two solutions thoroughly and impregnate them onto 10g of alumina carrier (commercially available alumina industrial carrier particles, specific surface area 230m²) using an equal-volume impregnation method. 2 / g, pore volume 1.0cm 3 The impregnated product was placed in an oven at 100°C and dried for 10 hours. The dried product was then placed in a muffle furnace and calcined at 400°C for 5 hours to obtain the catalyst product.

[0078] Comparative Example 2

[0079] (1) Commercially available alumina carrier (specific surface area 230 m²) 2 / g, pore volume 1.0cm 3 100g of alumina was impregnated in a 5wt% glucose solution (1g of glucose), then transferred to a hydrothermal reactor and reacted at 100°C for 10 hours. After cooling and filtration, the alumina was dried at 80°C for 4 hours and then calcined at 400°C for 10 hours under a nitrogen atmosphere to obtain a support (carbon-doped alumina). BET characterization showed that the alumina had a specific surface area of ​​180m². 2 / g, pore volume 1.0cm 3 / g.

[0080] (2) Dissolve 20g of nickel nitrate in deionized water and stir evenly. Dissolve 2g of magnesium nitrate in deionized water and stir evenly. Mix the two solutions and stir evenly. Impregnate the carbon-doped alumina support using the equal volume impregnation method. Place the impregnated product in an oven at 100°C and dry for 10 hours. Place the dried product in a muffle furnace and calcine at 400°C for 5 hours to obtain the catalyst product.

[0081] Test case

[0082] Methanation reaction performance test

[0083] 5 mL of catalyst was loaded into a stainless steel fixed-bed reactor. High-purity nitrogen gas was introduced at a flow rate of 300 mL / min, and the temperature was raised to 120 °C. The high-purity nitrogen gas was then switched to hydrogen gas at a flow rate of 200 mL / min, and the temperature was raised to 400 °C and maintained for 4 h. Then, the hydrogen gas was switched to the feed gas, and the reaction was carried out at 200 °C and a reaction pressure of 3.0 MPa. The composition of the gas after the reaction was analyzed by an Agilent 7890 gas chromatograph.

[0084] The catalysts prepared in Examples 1-6 and Comparative Examples 1-3 were evaluated for reaction according to the above evaluation method. Table 1 shows the detailed evaluation results (raw material gas composition: CO 0.5%, CO2 0.05%, H2 99.45%, by volume fraction).

[0085] Table 1 Catalyst CO x Evaluation results of the methanation reaction (reaction bed temperature 200℃)

[0086]

[0087] As can be seen from the results in Table 1, under the same conditions, the catalyst in the embodiments of the present invention significantly improved the CO2 methanation reaction. x The conversion rate is higher than that of the comparative example, indicating that the catalyst obtained by the carbon-containing alumina support used in this invention has higher activity, and the active components in the catalysts of Examples 1 to 6 have higher dispersion.

Claims

1. A methanation catalyst, comprising: The alumina-containing carrier, and the active component and additives loaded on the alumina-containing carrier, wherein the metal element in the active component is selected from at least one of Ni, Fe, and Co, and the metal element in the additives is selected from at least one of alkaline earth metals, transition metals, and rare earth metals, and the specific surface area of ​​the alumina-containing carrier is ≥300 m². 2 / g, pore size 10~30nm, pore volume 1.0~2.5cm³ 3 / g, water absorption rate of 100~180%; the carbon-containing alumina carrier is obtained by calcining alumina with a large specific surface area after modification by a carbonizable compound, wherein the carbonizable compound is selected from at least one of glucose and sucrose. Sodium hydroxide and sodium aluminate were prepared into a sodium aluminate solution. The sodium aluminate solution was added dropwise to an aluminum sulfate solution to obtain a boehmite precursor. The boehmite precursor was crystallized to obtain boehmite with a large specific surface area. The boehmite with a large specific surface area was calcined to obtain alumina with a large specific surface area.

2. The methanation catalyst according to claim 1, characterized in that, The specific surface area of ​​the carbon-containing alumina carrier is 320~460m². 2 / g, pore size 10~25nm, pore volume 1.5~2.2cm³ 3 / g, water absorption rate 120~150%; and / or, The alumina with a large specific surface area has a specific surface area ≥ 300 m². 2 / g.

3. The methanation catalyst according to claim 2, characterized in that, The amount of the carbonizable compound used is 0.1 to 10 wt% of alumina with a large specific surface area.

4. The methanation catalyst according to claim 3, characterized in that, The amount of the carbonizable compound used is 0.5 to 5 wt% of alumina with a large specific surface area.

5. The 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, 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, and / or the rare earth metal is selected from at least one of La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu.

6. The methanation catalyst according to claim 5, characterized in that, The alkaline earth metal is selected from at least one of Mg and Ca, and / or the transition metal is selected from 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, and Sm.

7. The methanation catalyst according to claim 1, characterized in that, Based on a total amount of 100 wt% for the methanation catalyst, the content of metal elements in the active component is 5-45 wt%, and / or the content of metal elements in the auxiliary agent is 0.1-10 wt%, and / or the content of the carbon-containing alumina support is 36-95 wt%.

8. The methanation catalyst according to claim 7, characterized in that, Based on a total amount of 100 wt% for the methanation catalyst, the content of metal elements in the active component is 14-40 wt%, and / or the content of metal elements in the auxiliary agent is 0.5-5 wt%, and / or the content of the carbon-containing alumina support is 40-85 wt%.

9. A method for preparing the methanation catalyst according to any one of claims 1 to 8, comprising: The carbon-containing alumina support precursor is impregnated in a solution containing an active component precursor compound and an auxiliary precursor compound, and then dried and calcined to obtain the methanation catalyst.

10. The preparation method according to claim 9, characterized in that, The preparation method specifically includes the following steps: (1) Prepare a sodium aluminate solution by mixing sodium hydroxide and sodium aluminate; (2) Add sodium aluminate solution dropwise to aluminum sulfate solution to obtain boehmite precursor; (3) Boehmite precursor is crystallized to obtain boehmite with a large specific surface area; (4) Boehmite with a large specific surface area is roasted to obtain alumina with a large specific surface area; (5) Add alumina with a large specific surface area to a solution of carbonizable compounds for contact reaction to obtain a carbon-containing alumina support precursor; (6) The carbon-containing alumina support precursor is impregnated in a solution containing the active component precursor compound and the auxiliary precursor compound, and then dried and calcined to obtain the methanation catalyst.

11. The preparation method according to claim 10, characterized in that, In the sodium aluminate solution, the molar ratio of sodium to aluminum is (3~6):1; and / or, The concentration of aluminum ions in the sodium aluminate solution is 0.1~1 mol / L; and / or, The concentration of the aluminum sulfate solution is 0.1~0.7 mol / L; and / or, The concentration of the carbonizable compound solution is 0.1~10 wt%; and / or, The active component precursor compound is selected from at least one soluble salt of Ni, Fe, and Co; and / or, The precursor compound is selected from at least one of the soluble salts of alkaline earth metals, transition metals, and rare earth metals.

12. The preparation method according to claim 11, characterized in that, The concentration of the carbonizable compound solution is 0.1~5 wt%; and / or, The active component precursor compound is selected from at least one of the nitrates of Ni, Fe, and Co; and / or, The precursor compound for the additive is selected from at least one of the nitrates of alkaline earth metals, transition metals, and rare earth metals.

13. The preparation method according to claim 10, characterized in that, In step (3), the crystallization conditions are: crystallization temperature of 50~120℃, crystallization time of 2~24h; and / or, In step (4), the calcination conditions are: calcination temperature of 400~600℃, calcination time of 4~10 h; and / or, In step (5), the conditions for the contact reaction are: a reaction temperature of 120~200℃ and a reaction time of 2~15 h; and / or, In step (6), the drying conditions are: a drying temperature of 60~140℃ and a drying time of 2~10h; and / or, In step (6), 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 h.

14. The use of a methanation catalyst according to any one of claims 1 to 8 or a methanation catalyst obtained by the preparation method according to any one of claims 9 to 13 in a methanation reaction.

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