Catalyst for preparing methane through carbon dioxide hydrogenation and preparation method thereof

Abstract

The invention relates to the technical field of carbon dioxide hydrogenation catalysts, in particular to a catalyst for preparing methane through carbon dioxide hydrogenation 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, heating and uniformly stirring, and adjusting the pH value to obtain sol; and adding a cordierite honeycomb ceramic carrier into the sol, taking out the cordierite honeycomb ceramic after the cordierite honeycomb ceramic fully adsorbs the sol, blowing off residual liquid, drying and roasting to obtain the catalyst for preparing methane through carbon dioxide hydrogenation. According to the invention, the nitrate solution and the citric acid are mixed to obtain the sol, and the components are fully dispersed, so that the oxides obtained after roasting are uniformly dispersed and uniformly loaded on the cordierite honeycomb ceramic, and the performance of the catalyst is stable. The whole process is simple in technology, and wide industrial application is facilitated.

Description

Technical Field

[0001] The invention relates to the technical field of carbon dioxide hydrogenation catalysts, and in particular to a carbon dioxide hydrogenation methane catalyst and a preparation method thereof. Background Art

[0002] As human society's demand for energy continues to rise, the large-scale use of fossil fuels has caused the carbon dioxide content in the air to increase significantly year by year, which in turn has caused a series of severe environmental problems such as global warming. In order to effectively alleviate this dilemma, converting carbon dioxide into hydrocarbon fuels has become a very promising research direction, which not only helps to reduce dependence on increasingly depleted fossil fuels, but also achieves carbon recycling and helps to build a sustainable energy system.

[0003] However, the molecular structure of carbon dioxide is extremely stable, and its carbon-oxygen bond dissociation energy is quite high, which means that it takes a lot of energy to reduce carbon dioxide to other substances. Among the many carbon dioxide conversion technologies, the hydrogenation of carbon dioxide to methane and methanol is a hot area of ​​current research. Among them, the hydrogenation of carbon dioxide to methanol has achieved engineering demonstration to a certain extent, providing a feasible example for large-scale carbon recycling. The hydrogenation of carbon dioxide to methane is still in the stage of in-depth laboratory research, and the research focus is mostly on the preparation and development of catalysts.

[0004] The carbon dioxide methanation reaction is a highly exothermic chemical reaction. However, due to the chemical inertness of carbon dioxide, the corresponding reaction activation energy is relatively high. It is necessary to promote the activation by increasing the reaction temperature and reduce the activation energy by using highly active catalysts. However, increasing the reaction temperature will consume a lot of energy and place higher requirements on equipment, which is not in line with the concept of sustainable energy development. The existing catalysts are not good enough, and their activity is not high at lower temperatures. In the application of carbon dioxide hydrogenation to methane, the reaction selectivity is low.

[0005] Based on this, the present invention proposes a carbon dioxide hydrogenation to methane catalyst with high activity and high selectivity. Summary of the invention

[0006] The first object of the present invention is to provide a catalyst for producing methane by hydrogenating carbon dioxide, which can solve the above-mentioned technical problems, improve the activity and selectivity of the catalyst, and reduce the reaction temperature.

[0007] The present invention provides a method for preparing a catalyst for producing methane by hydrogenating carbon dioxide, comprising the following steps:

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

[0009] S2. adding citric acid to the nitrate solution to form a mixture, heating and stirring, adjusting the pH, and obtaining a sol;

[0010] This step can fully disperse the components in the sol and ensure uniform loading on the carrier surface in the subsequent process.

[0011] S3. Adding a cordierite honeycomb ceramic carrier to the sol, taking out the cordierite honeycomb ceramic after fully absorbing the sol, blowing off the residual liquid, drying, and calcining to obtain a carbon dioxide hydrogenation to methane catalyst.

[0012] After calcination, composition analysis was performed, and 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, and the remainder was cordierite honeycomb ceramics.

[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 the nitrate solution in step S1, the concentration of Al(NO3)3 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, the molar concentration of citric acid in the mixture in step S2 is twice the molar concentration of cations. 3+ 、Ni 2+ 、Ce 4+ .

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

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

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

[0019] The minimum size of cordierite honeycomb ceramics is 150*150*300mm, which effectively avoids the internal structure of cordierite honeycomb ceramics being damaged by too small a size, and also provides a larger reaction site for subsequent catalytic reactions, which is beneficial to improving the efficiency of the catalytic reaction.

[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 / cm 3 .

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

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

[0023] Beneficial effects:

[0024] The present invention adopts cordierite honeycomb ceramic as a carrier, which has a large specific surface area, is conducive to the adsorption of sol and the uniform dispersion of active ingredients. At the same time, its good thermal stability and chemical stability can maintain the integrity of the structure under reaction conditions, providing a guarantee for the long-term stable operation of the catalyst. Its regular honeycomb structure is conducive to the diffusion and transmission of the reaction gas, increases the contact area with the reaction gas, reduces the mass transfer resistance, and further improves the catalytic reaction efficiency.

[0025] In the present invention, a sol is obtained by mixing a nitrate solution with citric acid, and each component is fully dispersed, so that each oxide obtained after calcination is evenly dispersed and evenly loaded on the cordierite honeycomb ceramic, so that the catalyst performance is stable. The introduction of NiO after calcination increases the active sites of the catalyst, reduces the catalytic reaction temperature, and improves the catalytic performance. The nickel element, as an active center, can effectively adsorb hydrogen and carbon dioxide to promote the reaction; Al2O3 plays a role in dispersing active components and stabilizing the catalyst structure; CeO2 can modify the active center and improve its catalytic activity. The synergistic effect of the three improves the overall activity and selectivity of the catalyst.

[0026] The whole preparation method of the present invention has simple process, and the raw materials are easy to obtain, which is conducive to large-scale production and preparation, and is convenient for wide industrial application. DETAILED DESCRIPTION

[0027] It should be noted that the following detailed descriptions are illustrative and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present application belongs.

[0028] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form also includes the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this description, it indicates 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 in conjunction with the embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] Example 1

[0031] A method for preparing a catalyst for producing methane by hydrogenating carbon dioxide comprises the following steps:

[0032] S1. Al(NO3)3, Ni(NO3)2 and Ce(NO3)4 are dissolved 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. Add citric acid to the nitrate solution to form a mixture, the cations in the mixture include Al 3+ 、Ni 2+ 、Ce 4+ , the molar concentration of citric acid is twice the molar concentration of cations, heated to 70°C and stirred evenly with a magnetic stirrer, and the pH was adjusted to 3 with ammonia water 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 holes / square centimeter, and a density of 0.5g / cm 3 ; The mass ratio between cordierite honeycomb ceramics and sol is 71:150. After the cordierite honeycomb ceramics fully absorb the sol, they are taken out and the residual liquid is blown away. After drying at 110°C for 5 hours, they are calcined at 500°C for 2 hours. Al(NO3)3, Ni(NO3)2 and Ce(NO3)4 are fully decomposed to obtain Al2O3, NiO and CeO2. In this process, the sol is dried into particles loaded on the surface of the cordierite honeycomb ceramics to obtain a carbon dioxide hydrogenation to methane catalyst.

[0035] Example 2

[0036] A method for preparing a catalyst for producing methane by hydrogenating carbon dioxide comprises the following steps:

[0037] S1. Al(NO3)3, Ni(NO3)2 and Ce(NO3)4 are dissolved 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. Add citric acid to the nitrate solution to form a mixture, the cations in the mixture include Al 3+ 、Ni 2+ 、Ce 4+ , the molar concentration of citric acid is twice the molar concentration of cations, heated to 65°C and stirred evenly with a magnetic stirrer, and the pH was adjusted to 2.8 with ammonia water 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 holes / square centimeter, and a density of 0.6g / cm 3 ; The mass ratio between cordierite honeycomb ceramics and sol is 83:100. The cordierite honeycomb ceramics are taken out after fully absorbing the sol, and the residual liquid is blown away. After drying at 100°C for 6 hours, it is calcined at 550°C for 2 hours. Al(NO3)3, Ni(NO3)2 and Ce(NO3)4 are fully decomposed to obtain Al2O3, NiO and CeO2. In this process, the sol is dried into particles loaded on the surface of the cordierite honeycomb ceramics to obtain a carbon dioxide hydrogenation to methane catalyst.

[0040] Example 3

[0041] A method for preparing a catalyst for producing methane by hydrogenating carbon dioxide comprises the following steps:

[0042] S1. Al(NO3)3, Ni(NO3)2 and Ce(NO3)4 are dissolved 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. Add citric acid to the nitrate solution to form a mixture, the cations in the mixture include Al 3+ 、Ni 2+ 、Ce 4+ , the molar concentration of citric acid is twice the molar concentration of cations, heated to 75°C and stirred evenly, and ammonia water is used to adjust the pH to 3.5 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 holes / square centimeter, and a density of 0.3g / cm 3The mass ratio between cordierite honeycomb ceramics and sol is 76:125. The cordierite honeycomb ceramics are taken out after fully absorbing the sol, and the residual liquid is blown away. After drying at 120°C for 4 hours, it is calcined at 450°C for 3 hours. Al(NO3)3, Ni(NO3)2 and Ce(NO3)4 are fully decomposed to obtain Al2O3, NiO and CeO2. In this process, the sol is dried into particles loaded on the surface of the cordierite honeycomb ceramics to obtain a carbon dioxide hydrogenation to methane catalyst.

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

[0046] The catalyst was evaluated using a fixed bed reactor. The reaction was carried out at 3.5 MPa. A mixed gas of CO2 and H2 was introduced. The molar ratio of H2 to CO2 was 4:1. The reactor was heated to a specified temperature for carbon dioxide hydrogenation and methanation. The composition of the gas after the reaction was analyzed by gas chromatography. The catalyst performance data results are shown in Table 1.

[0047] Table 1

[0048]

[0049]

[0050] As can be seen from Table 1, the carbon dioxide conversion rate of the carbon dioxide hydrogenation to methane catalysts prepared in Examples 1-3 shows a trend of first increasing and then decreasing with increasing temperature, and the optimal active temperature window of the catalyst is between 300°C and 350°C, and both have excellent activity and selectivity at 350°C. Example 1 is the best example, and the prepared carbon dioxide hydrogenation to methane catalyst has better activity and selectivity than the products of other examples, and can effectively catalyze the reaction of hydrogenating carbon dioxide to generate methane.

[0051] At present, the reaction temperature of the conventional catalyst Ni / γ-Al2O3 is 450-500°C. The reaction temperature of the carbon dioxide hydrogenation to methane catalyst prepared by the preparation method provided by the present invention is greatly reduced, and it still has high activity and high reaction selectivity at a relatively low temperature, thereby reducing energy consumption and equipment requirements, and facilitating promotion and application.

[0052] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements 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 hydrogenating carbon dioxide to methane, characterized in that: The following steps are involved: S1. dissolving nitrate A, nitrate B and nitrate C in deionized water to prepare a nitrate solution; S2. adding citric acid to the nitrate solution to form a mixture, heating and stirring, adjusting the pH, and obtaining a sol; S3. Adding a cordierite honeycomb ceramic carrier to the sol, taking out the cordierite honeycomb ceramic after fully absorbing the sol, blowing off the residual liquid, drying, and calcining to obtain a carbon dioxide hydrogenation catalyst.

2. The method for preparing a catalyst for producing methane by hydrogenation of carbon dioxide according to claim 1, characterized in that: In step S1, nitrate A is Al(NO3)3; nitrate B is Ni(NO3)2; and nitrate C is Ce(NO3)4.

3. The method for preparing a catalyst for producing methane by hydrogenation of carbon dioxide according to claim 2, characterized in that: In the nitrate solution in step S1, the concentration of Al(NO3)3 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.

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

5. The method for preparing a catalyst for producing methane by hydrogenation of carbon dioxide according to claim 1, characterized in that: The heating temperature in step S2 is 65-75°C.

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

5.

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

8. The method for preparing a catalyst for producing methane by hydrogenation of carbon dioxide 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 / cm 3 .

9. The method for preparing a catalyst for producing methane by hydrogenation of carbon dioxide according to claim 1, characterized in that: The specific steps of drying and calcining in step S3 are: drying at 100-120° C. for 4-6 hours, and then calcining at 450-550° C. for 2-3 hours.

10. A catalyst for producing methane by hydrogenating carbon dioxide obtained by the method for producing a catalyst for producing methane by hydrogenating carbon dioxide according to any one of claims 1 to 9.

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