Carbon dioxide hydrogenation to methane catalyst and preparation method thereof

Abstract

The present application relates to the technical field of carbon dioxide hydrogenation catalyst, and particularly relates to a carbon dioxide hydrogenation catalyst for preparing methane and a preparation method thereof. The preparation method comprises the following steps: dissolving nitrate A, nitrate B and nitrate C in deionized water to prepare a nitrate solution; adding citric acid into the nitrate solution to form a mixture, uniformly heating and stirring, adjusting pH, and obtaining a sol; adding a cordierite honeycomb ceramic carrier into the sol, taking out the cordierite honeycomb ceramic after fully adsorbing the sol, blowing off residual liquid, drying, and calcining to obtain the carbon dioxide hydrogenation catalyst for preparing methane. In the present application, the sol is obtained by mixing the nitrate solution and citric acid, and the components are fully dispersed, so that the oxides obtained after calcination are uniformly dispersed and uniformly loaded on the cordierite honeycomb ceramic, and the catalyst performance is stable. The whole process is simple, which is helpful for wide industrial application.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of carbon dioxide hydrogenation catalysts, in particular to a carbon dioxide hydrogenation catalyst for preparing methane and a preparation method thereof. BACKGROUND

[0002] With the continuous rise of human society's demand for energy, the large-scale application of fossil fuels has caused the carbon dioxide content in the air to rise significantly year by year, thereby causing a series of serious environmental problems such as global warming. In order to effectively alleviate this predicament, converting carbon dioxide into hydrocarbon fuels has become a highly potential research direction, which not only helps to reduce the dependence on increasingly depleted fossil fuels, but also realizes the recycling of carbon, which is helpful to build a sustainable energy system.

[0003] However, the carbon dioxide molecule has a very stable structure, and its carbon-oxygen bond has a high dissociation energy, which makes it necessary to input a high energy to reduce carbon dioxide into other substances. Among the many carbon dioxide conversion technologies, carbon dioxide hydrogenation to prepare methane and methanol is a hot research field at present. Among them, carbon dioxide hydrogenation to prepare methanol has achieved engineering demonstration to a certain extent, providing a feasible example for large-scale carbon recycling. Carbon dioxide hydrogenation to prepare methane is still in the laboratory research stage, and the research focus is mostly focused on the preparation and research of catalysts.

[0004] The carbon dioxide methanation reaction is a highly exothermic chemical reaction, but due to the chemical inertness of carbon dioxide, the corresponding reaction activation energy is relatively high, which requires improving the reaction temperature to promote activation and using high-activity catalysts to reduce the activation energy to facilitate the process. However, increasing the reaction temperature will consume a large amount of energy and require higher equipment, which does not conform to the concept of sustainable energy development. The performance of the existing catalysts is not enough, and the activity at a lower temperature is not high. The reaction selectivity is low in the application of carbon dioxide hydrogenation to prepare methane.

[0005] Therefore, the present application provides a carbon dioxide hydrogenation catalyst for preparing methane with high activity and selectivity. SUMMARY

[0006] The first purpose of the present application is to provide a carbon dioxide hydrogenation catalyst for preparing methane, which can solve the above technical problems, improve the activity and selectivity of the catalyst, and reduce the reaction temperature.

[0007] The present application provides a preparation method of a carbon dioxide hydrogenation catalyst for preparing methane, which comprises the following steps:

[0008] S1. Dissolving nitrate A, nitrate B and nitrate C in deionized water to prepare a nitrate solution;

[0009] S2. Add citric acid to the nitrate solution to form a mixture, heat and stir until homogeneous, adjust the pH to obtain a sol;

[0010] This step allows the components in the sol to be fully dispersed, ensuring uniform loading on the carrier surface in the subsequent process.

[0011] S3. Add cordierite honeycomb ceramic carrier to the sol. After the cordierite honeycomb ceramic fully adsorbs the sol, remove it, blow off the residual liquid, dry it, and calcine it to obtain a catalyst for the hydrogenation of carbon dioxide to methane.

[0012] Compositional analysis after calcination showed that Al(NO3)3, Ni(NO3)2, and Ce(NO3)4 were fully decomposed. The final catalyst contained 15-25% Al2O3, 1.5-3% NiO, 0.2-1% CeO2 by mass fraction, with the balance being cordierite honeycomb ceramic.

[0013] Preferably, in step S1, nitrate A is Al(NO3)3; nitrate B is Ni(NO3)2; and nitrate C is Ce(NO3)4.

[0014] Preferably, in step S1, the concentration of Al(NO3)3 in the nitrate solution is 20.9-34.8 g / L, the concentration of NiNO3 is 1.21-2.44 g / L, and the concentration of Ce(NO3)4 is 0.13-0.63 g / L.

[0015] Preferably, in step S2, the molar concentration of citric acid in the mixture is twice the molar concentration of the cation. The cation includes Al. 3+ Ni 2+ Ce 4+ .

[0016] Preferably, the heating temperature in step S2 is 65-75℃.

[0017] Preferably, in step S2, the pH value is adjusted to 2.8-3.5.

[0018] Preferably, the mass ratio between cordierite honeycomb ceramic and sol in step S3 is (71-83):(100-150).

[0019] The minimum size of cordierite honeycomb ceramic is 150*150*300mm, which effectively avoids damage to the internal structure of cordierite honeycomb ceramic due to its small size, and also provides a larger reaction site for subsequent catalytic reactions, which is conducive to improving the efficiency of catalytic reactions.

[0020] Preferably, in step S3, the cordierite honeycomb ceramic has a pore size of 50-60 pores / cm² and a density of 0.3-0.6 g / cm³. 3 .

[0021] Preferably, the specific steps of drying and calcining in step S3 are as follows: after drying at 100-120℃ for 4-6 hours, calcining at 450-550℃ for 2-3 hours.

[0022] The present invention also provides a carbon dioxide hydrogenation to methane catalyst prepared by the above-mentioned method.

[0023] Beneficial effects:

[0024] This invention uses cordierite honeycomb ceramic as a carrier, which has a large specific surface area, which helps the adsorption of sol and the uniform dispersion of active ingredients. At the same time, its good thermal and chemical stability can maintain the structural integrity under reaction conditions, which provides a guarantee for the long-term stable operation of the catalyst. Furthermore, its regular honeycomb structure is conducive to the diffusion and transport of reactant gases, increases the contact area between the reactant gases and the catalyst, reduces mass transfer resistance, and further improves the catalytic reaction efficiency.

[0025] In this invention, a sol is obtained by mixing nitrate solution and citric acid, ensuring thorough dispersion of all components. This results in uniform dispersion of the oxides obtained after calcination, which are then uniformly loaded onto cordierite honeycomb ceramic, stabilizing the catalyst performance. The introduction of NiO after calcination increases the active sites on the catalyst, lowers the catalytic reaction temperature, and improves catalytic performance. Nickel, as an active center, effectively adsorbs hydrogen and carbon dioxide, promoting the reaction. Al₂O₃ disperses the active components and stabilizes the catalyst structure. CeO₂ modifies the active centers, enhancing their catalytic activity. The synergistic effect of these three elements improves the overall activity and selectivity of the catalyst.

[0026] The preparation method of this invention is simple, the raw materials are readily available, which is conducive to large-scale production and facilitates its widespread industrial application. Detailed Implementation

[0027] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0028] It should be noted that the terminology used herein is for the purpose of describing particular implementations only and is not intended to limit the exemplary implementations according to this application. As used herein, the singular form includes the plural form unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this description, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0029] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] Example 1

[0031] A method for preparing a catalyst for the hydrogenation of carbon dioxide to methane includes the following steps:

[0032] S1. Dissolve Al(NO3)3, Ni(NO3)2 and Ce(NO3)4 in deionized water to prepare a nitrate solution; the concentration of Al(NO3)3 in the nitrate solution is 30.00 g / L, the concentration of NiNO3 is 2.44 g / L, and the concentration of Ce(NO3)4 is 0.46 g / L.

[0033] S2. Adding citric acid to a nitrate solution forms a mixture, the mixture containing cations including Al. 3+ Ni 2+ Ce 4+ The molar concentration of citric acid was twice that of cations. The mixture was heated to 70°C and stirred evenly with a magnetic stirrer. The pH was adjusted to 3 with ammonia to obtain a sol.

[0034] S3. Add cordierite honeycomb ceramic carrier to the sol. The cordierite honeycomb ceramic has a size of 300*300*400mm, a pore size of 50-60 pores / cm², and a density of 0.5g / cm³. 3 The mass ratio between cordierite honeycomb ceramic and sol was 71:150. After the cordierite honeycomb ceramic fully adsorbed the sol, it was removed, the residual liquid was blown off, and it was dried at 110℃ for 5 hours and then calcined at 500℃ for 2 hours. Al(NO3)3, Ni(NO3)2 and Ce(NO3)4 were fully decomposed to obtain Al2O3, NiO and CeO2. During this process, the sol dried into particles and was loaded on the surface of the cordierite honeycomb ceramic to obtain a catalyst for the hydrogenation of carbon dioxide to methane.

[0035] Example 2

[0036] A method for preparing a catalyst for the hydrogenation of carbon dioxide to methane includes the following steps:

[0037] S1. Dissolve Al(NO3)3, Ni(NO3)2 and Ce(NO3)4 in deionized water to prepare a nitrate solution; the concentration of Al(NO3)3 in the nitrate solution is 20.9 g / L, the concentration of NiNO3 is 1.88 g / L, and the concentration of Ce(NO3)4 is 0.63 g / L.

[0038] S2. Adding citric acid to a nitrate solution forms a mixture, the mixture containing cations including Al. 3+ Ni 2+ Ce 4+ The molar concentration of citric acid was twice that of cations. The mixture was heated to 65°C and stirred evenly with a magnetic stirrer. The pH was adjusted to 2.8 with ammonia to obtain a sol.

[0039] S3. Add cordierite honeycomb ceramic carrier to the sol. The cordierite honeycomb ceramic has a size of 150*150*300mm, a pore size of 50-60 pores / cm², and a density of 0.6g / cm³. 3 The mass ratio between cordierite honeycomb ceramic and sol was 83:100. After the cordierite honeycomb ceramic fully adsorbed the sol, it was taken out, the residual liquid was blown off, and it was dried at 100℃ for 6 hours and then calcined at 550℃ for 2 hours. Al(NO3)3, Ni(NO3)2 and Ce(NO3)4 were fully decomposed to obtain Al2O3, NiO and CeO2. During this process, the sol dried into particles and was loaded on the surface of cordierite honeycomb ceramic to obtain a catalyst for the hydrogenation of carbon dioxide to methane.

[0040] Example 3

[0041] A method for preparing a catalyst for the hydrogenation of carbon dioxide to methane includes the following steps:

[0042] S1. Dissolve Al(NO3)3, Ni(NO3)2 and Ce(NO3)4 in deionized water to prepare a nitrate solution; the concentration of Al(NO3)3 in the nitrate solution is 34.8 g / L, the concentration of NiNO3 is 1.21 g / L, and the concentration of Ce(NO3)4 is 0.13 g / L.

[0043] S2. Adding citric acid to a nitrate solution forms a mixture, the mixture containing cations including Al. 3+ Ni 2+ Ce 4+ The molar concentration of citric acid is twice the molar concentration of cations. The mixture is heated to 75°C and stirred until homogeneous. The pH is adjusted to 3.5 with ammonia to obtain a sol.

[0044] S3. Add cordierite honeycomb ceramic carrier to the sol. The cordierite honeycomb ceramic has a size of 150*150*300mm, a pore size of 50-60 pores / cm², and a density of 0.3g / cm³. 3The mass ratio between cordierite honeycomb ceramic and sol was 76:125. After the cordierite honeycomb ceramic fully adsorbed the sol, it was removed, the residual liquid was blown off, and it was dried at 120℃ for 4 hours. Then it was calcined at 450℃ for 3 hours. Al(NO3)3, Ni(NO3)2 and Ce(NO3)4 were fully decomposed to obtain Al2O3, NiO and CeO2. During this process, the sol dried into particles and was loaded on the surface of the cordierite honeycomb ceramic to obtain a catalyst for the hydrogenation of carbon dioxide to methane.

[0045] The performance of the carbon dioxide hydrogenation to methane catalysts prepared in Examples 1-3 was tested.

[0046] Catalyst evaluation was conducted using a fixed-bed reactor. The reaction was carried out at 3.5 MPa with a CO2 and H2 mixture introduced at a molar ratio of 4:1. The reactor was heated to a specified temperature to carry out the carbon dioxide hydrogenation methanation reaction. The composition of the gas after the reaction was analyzed by gas chromatography. The catalyst performance data obtained are shown in Table 1.

[0047] Table 1

[0048]

[0049]

[0050] As shown in Table 1, the carbon dioxide conversion rate of the carbon dioxide hydrogenation to methane catalysts prepared in Examples 1-3 first increases and then decreases with increasing temperature. The optimal activity temperature window of the catalyst is between 300℃ and 350℃, and all exhibit excellent activity and selectivity at 350℃. Example 1 is the best example, and the carbon dioxide hydrogenation to methane catalyst prepared therefrom has better activity and selectivity than the products of other examples, and can effectively catalyze the reaction of carbon dioxide hydrogenation to methane.

[0051] Currently, the reaction temperature of conventional catalysts Ni / γ-Al2O3 is 450-500℃. The carbon dioxide hydrogenation to methane catalyst prepared by the method provided in this invention has a significantly lower reaction temperature. It still has high activity and high reaction selectivity at lower temperatures, reducing energy consumption and lowering equipment requirements, making it easier to promote and apply.

[0052] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a catalyst for the hydrogenation of carbon dioxide to methane, characterized in that, Includes the following steps: S1. Dissolve nitrate A, nitrate B, and nitrate C in deionized water to prepare a nitrate solution, wherein nitrate A is Al(NO3)3; nitrate B is Ni(NO3)2; and nitrate C is Ce(NO3)4. The concentration of Al(NO3)3 in the nitrate solution is 20.9-34.8 g / L, the concentration of Ni(NO3)2 is 1.21-2.44 g / L, and the concentration of Ce(NO3)4 is 0.13-0.63 g / L. S2. Add citric acid to the nitrate solution to form a mixture, heat and stir until homogeneous, adjust the pH to obtain a sol; S3. Add cordierite honeycomb ceramic carrier to the sol. After the cordierite honeycomb ceramic fully adsorbs the sol, remove it, blow off the residual liquid, dry it, and calcine it to obtain a carbon dioxide hydrogenation catalyst.

2. The method for preparing the catalyst for carbon dioxide hydrogenation to methane according to claim 1, characterized in that, In step S2, the molar concentration of citric acid in the mixture is twice the molar concentration of cations.

3. The method for preparing the catalyst for carbon dioxide hydrogenation to methane according to claim 1, characterized in that, The heating temperature in step S2 is 65-75℃.

4. The method for preparing the catalyst for carbon dioxide hydrogenation to methane according to claim 1, characterized in that, In step S2, the pH value is adjusted to 2.8-3.

5.

5. The method for preparing the catalyst for carbon dioxide hydrogenation to methane according to claim 1, characterized in that, In step S3, the mass ratio between cordierite honeycomb ceramic and sol is (71-83):(100-150).

6. The method for preparing the catalyst for carbon dioxide hydrogenation to methane according to claim 1, characterized in that, In step S3, the cordierite honeycomb ceramic has a pore size of 50-60 pores / square centimeter and a density of 0.3-0.6 g / cm³. 3 .

7. The method for preparing the catalyst for carbon dioxide hydrogenation to methane according to claim 1, characterized in that, The specific steps of drying and calcining in step S3 are as follows: after drying at 100-120℃ for 4-6 hours, calcining at 450-550℃ for 2-3 hours.

8. A carbon dioxide hydrogenation to methane catalyst prepared by the method of any one of claims 1-7.

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