Carbon dioxide capture and methanation bifunctional catalyst, and preparation method and application thereof
By preparing a bifunctional catalyst based on boron-nitrogen co-doped carbon nanotube aerogel, the problems of high energy consumption and low efficiency in carbon dioxide capture and methanation in the prior art have been solved, realizing efficient capture and conversion of carbon dioxide at low temperature and improving methane yield and purity.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- CHINA PETROLEUM & CHEMICAL CORP
- Filing Date
- 2024-12-09
- Publication Date
- 2026-06-09
AI Technical Summary
Existing carbon dioxide capture methods suffer from high energy consumption, high cost, and low separation efficiency. Furthermore, existing CO2 methanation technologies require high temperature and high pressure, and the catalysts have insufficient catalytic activity and stability, making it difficult to achieve carbon dioxide capture and methanation in the same system.
A bifunctional catalyst based on boron-nitrogen co-doped carbon nanotube aerogel is used to load metal or metal oxide active components. A continuous porous structure is prepared by supercritical carbon dioxide drying method. Combined with active components such as nickel, zirconium, and nickel oxide, it can achieve efficient capture and methanation conversion of carbon dioxide.
It efficiently captures carbon dioxide and promotes its methanation conversion within the same reaction system, reduces reaction temperature and energy consumption, and improves methane yield and purity, exhibiting good catalytic stability and reusability.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of catalyst technology, specifically to a bifunctional catalyst for carbon dioxide capture and methanation, its preparation method, and its application. Background Technology
[0002] With the acceleration of industrialization and the continuous growth of global energy demand, the widespread use of fossil fuels has led to massive emissions of carbon dioxide (CO2), exacerbating global warming. Therefore, effectively reducing CO2 emissions and exploring its resource utilization pathways has become a hot topic and a challenge in global scientific research. Traditional CO2 capture methods mainly include physical adsorption, chemical absorption, and membrane separation, but these methods often suffer from high energy consumption, high cost, and low separation efficiency. Furthermore, utilizing captured CO2 for resource purposes, such as converting it into useful chemicals like methane (CH4), is also an important way to solve the CO2 emission problem. However, existing CO2 methanation technologies typically require high temperature and high pressure conditions, and the catalytic activity and stability of the catalysts need improvement. Currently, it is difficult to simultaneously perform CO2 capture and CO2 methanation in the same system. Therefore, developing a bifunctional catalyst capable of simultaneously achieving CO2 capture and methanation conversion is of great significance for simplifying the process, reducing energy consumption, and improving efficiency. Summary of the Invention
[0003] To address the problems existing in the aforementioned background technology, this invention provides a bifunctional catalyst for carbon dioxide capture and methanation based on boron-nitrogen co-doped carbon nanotube aerogel support, and its preparation method. This catalyst can efficiently capture carbon dioxide and promote its methanation conversion within the same reaction system, reducing reaction temperature and energy consumption, and improving methane yield and purity. The bifunctional catalyst of this invention combines a highly efficient carbon dioxide adsorbent material and a methanation catalytically active component, enabling the capture and methanation conversion of carbon dioxide within the same reaction system, resulting in significant environmental and economic benefits.
[0004] To achieve the above-mentioned objectives, the present invention provides the following technical solution:
[0005] A bifunctional catalyst for carbon dioxide capture and methanation includes a boron-nitrogen co-doped carbon nanotube aerogel support and a metal or metal oxide active component and additives supported on the support.
[0006] The boron-nitrogen co-doped carbon nanotube aerogel is obtained by supercritical carbon dioxide drying of a boron-nitrogen co-doped carbon nanotube dispersion. This boron-nitrogen co-doped carbon nanotube aerogel has a three-dimensional network structure with continuous pores and a specific surface area of not less than 500 m². 2 / g, porosity not less than 80%;
[0007] The active metal or metal oxide component and the additive are loaded onto the pores and surface of the carrier, wherein the active component is selected from any one or a mixture of one or more of metallic nickel, metallic zirconium, nickel oxide, and zirconium oxide, and the additive is any one or a mixture of two of metallic lanthanum and lanthanum oxide.
[0008] Furthermore, the boron-nitrogen co-doped carbon nanotubes of this invention are prepared by chemical vapor deposition or arc discharge method using methane as the carbon source and trimethylboron and trimethylamine as the boron and nitrogen sources, respectively. The molar ratio of boron to nitrogen is 1:1 to 1:5, preferably 1:1 to 1:2. After boron-nitrogen co-doping, the surface properties and chemical activity of the carrier material can be significantly altered, thereby improving the adsorption capacity for carbon dioxide gas and enhancing the mechanical properties and chemical stability of the carrier. In addition, the interaction between heteroatoms and active metals after boron-nitrogen co-doping improves the dispersion of the active metal on the carrier surface, thus enhancing catalytic activity.
[0009] Furthermore, in the catalyst of the present invention, the mass ratio of the active metal or metal oxide component and the auxiliary agent to the boron-nitrogen co-doped carbon nanotube aerogel support is (0.05-0.5):1.
[0010] Furthermore, the present invention also provides a method for preparing the above-mentioned bifunctional catalyst for carbon dioxide capture and methanation, comprising the following steps:
[0011] (1) First, boron-nitrogen co-doped carbon nanotubes are dispersed in a solvent to form a uniform dispersion. Then, the solvent is removed by supercritical carbon dioxide drying to form a boron-nitrogen co-doped carbon nanotube aerogel with a three-dimensional network structure of continuous pores, which serves as a catalyst support.
[0012] (2) Mix the solution containing the active metal precursor with the boron-nitrogen co-doped carbon nanotube aerogel prepared in step (1) and use the impregnation method to make the active metal precursor uniformly adsorbed in the pores and surface of the boron-nitrogen co-doped carbon nanotube aerogel.
[0013] (3) Heat the product obtained in step (2) to a certain temperature to convert the active metal precursor into a catalytically active metal or metal oxide form, and tightly combine it with boron-nitrogen co-doped carbon nanotube aerogel to form the carbon dioxide capture and methanation bifunctional catalyst of the present invention.
[0014] The heat treatment temperature in step (3) is 400-1000℃, preferably 500-700℃, and the heat treatment time is 1-12h, preferably 5-8h; and the heating rate is limited to 1-10℃ / min, preferably 5-8℃ / min. A suitable heating rate is beneficial to forming a catalyst with a suitable active metal particle size.
[0015] Furthermore, the solvent for dispersing carbon nanotubes in step (1) of the present invention is selected from any one or a mixture of one or more of water, ethanol, methanol, isopropanol, acetone, benzene and toluene.
[0016] Furthermore, the supercritical carbon dioxide drying method described in step (1) of the present invention operates at a temperature of 40–80°C, preferably 40–60°C, a pressure of 8–30 MPa, preferably 15–25 MPa, and a time of 1–10 h.
[0017] Further, the active metal precursor in step (2) of the present invention is a mixture of any one or two of nickel salts and zirconium salts with lanthanum salt; the nickel salt is selected from any one or more of nickel nitrate, nickel sulfate, and nickel chloride; the zirconium salt is selected from any one or more of zirconium nitrate, zirconium sulfate, and zirconium chloride; and the lanthanum salt is selected from any one or more of lanthanum nitrate, lanthanum sulfate, and lanthanum chloride. Preferably, the active metal precursor in step (2) of the present invention is a mixture of nickel salt, zirconium salt, and lanthanum salt, and the molar ratio of nickel, zirconium, and lanthanum is (1-3):1:(0.1-0.5).
[0018] Furthermore, the solvent containing the active metal precursor solution in step (2) of the present invention is selected from any one or a mixture of one or more of water, ethanol, methanol, isopropanol, acetone, benzene and toluene, preferably a mixture of water and ethanol.
[0019] Furthermore, the immersion temperature in step (2) of the present invention is 30-100°C, preferably 60-80°C, and the immersion time is 1-20 hours, preferably 5-8 hours.
[0020] Furthermore, the present invention also provides a method for using the above-mentioned catalyst, wherein the catalyst is used at a reaction temperature of 250–400°C. This catalyst can effectively promote the adsorption and methanation reactions of carbon dioxide at lower temperatures, improving methane yield and purity, while exhibiting good catalytic stability and reusability.
[0021] Compared with the prior art, the present invention has the following beneficial effects:
[0022] The catalyst prepared by the method described in this invention utilizes the high specific surface area and continuous pore structure of boron-nitrogen co-doped carbon nanotube aerogel to provide abundant adsorption and catalytic active sites. At the same time, the active components of metallic nickel, nickel oxide, metallic zirconium, and zirconium oxide, and the auxiliary agents of metallic lanthanum and lanthanum oxide exhibit excellent methanation catalytic activity. The combined effect of these two components enables efficient capture and methanation conversion of carbon dioxide.
[0023] The catalyst prepared by this invention can efficiently capture carbon dioxide and promote its methanation conversion in the same reaction system, reduce reaction temperature and energy consumption, improve methane yield and purity, and can be used at lower temperatures. Detailed Implementation
[0024] The present invention will be further described below with reference to specific embodiments, but this does not constitute any limitation on the present invention.
[0025] Example 1
[0026] A method for preparing a bifunctional catalyst for carbon dioxide capture and methanation includes:
[0027] (1) Boron-nitrogen co-doped carbon nanotubes were prepared by chemical vapor deposition using methane as the carbon source, trimethylboron and trimethylamine as the boron and nitrogen sources, respectively, with a boron-nitrogen doping ratio of 1:1.
[0028] (2) The boron-nitrogen co-doped carbon nanotubes were uniformly dispersed in ethanol to form a dispersion. Then, the dispersion was dried for 5 hours at 40°C and 15 MPa using supercritical carbon dioxide drying method to obtain boron-nitrogen co-doped carbon nanotube aerogel.
[0029] (3) Nickel nitrate and lanthanum chloride were dissolved in a mixed solvent of water and ethanol (the volume ratio of water to ethanol was 1:2) to prepare a precursor solution, wherein the molar ratio of nickel to lanthanum was 1:0.2; the precursor solution was mixed with the boron-nitrogen co-doped carbon nanotube aerogel and impregnated at 60°C for 5 hours.
[0030] (4) The above mixture is placed in a muffle furnace and heated to 550°C at a heating rate of 5°C / min, and held at this temperature for 5 hours to form a bifunctional catalyst S1 for carbon dioxide capture and methanation.
[0031] Example 2
[0032] A method for preparing a bifunctional catalyst for carbon dioxide capture and methanation includes:
[0033] (1) Boron-nitrogen co-doped carbon nanotubes were prepared by chemical vapor deposition using methane as the carbon source, trimethylboron and trimethylamine as the boron and nitrogen sources, respectively, with a boron-nitrogen doping ratio of 1:2.
[0034] (2) The prepared boron-nitrogen co-doped carbon nanotubes were uniformly dispersed in ethanol to form a dispersion. Subsequently, the dispersion was dried for 8 hours at 40℃ and 20MPa using supercritical carbon dioxide drying method to obtain boron-nitrogen co-doped carbon nanotube aerogel;
[0035] (3) Nickel nitrate and lanthanum chloride were dissolved in a mixed solvent of water and ethanol (the volume ratio of water to ethanol was 1:2) to prepare a precursor solution, wherein the molar ratio of nickel to lanthanum was 1:0.2; the precursor solution was mixed with the boron-nitrogen co-doped carbon nanotube aerogel and impregnated at 80°C for 8 hours.
[0036] (4) The above mixture is placed in a muffle furnace and heated to 600°C at a heating rate of 6°C / min, and held at this temperature for 5 hours to form a bifunctional catalyst S2 for carbon dioxide capture and methanation.
[0037] Example 3
[0038] A method for preparing a bifunctional catalyst for carbon dioxide capture and methanation includes:
[0039] (1) Boron-nitrogen co-doped carbon nanotubes were prepared by chemical vapor deposition using methane as the carbon source, trimethylboron and trimethylamine as the boron and nitrogen sources, respectively, with a boron-nitrogen doping ratio of 1:2.
[0040] (2) The prepared boron-nitrogen co-doped carbon nanotubes were uniformly dispersed in ethanol to form a dispersion. Subsequently, the dispersion was dried for 5 h at 40 °C and 25 MPa using supercritical carbon dioxide drying method to obtain boron-nitrogen co-doped carbon nanotube aerogel;
[0041] (3) Nickel nitrate, zirconium tetrachloride and lanthanum chloride were dissolved in a mixed solvent of water and ethanol (the volume ratio of water to ethanol was 1:2) to prepare a precursor solution, wherein the molar ratio of nickel, zirconium and lanthanum was 1:1:0.2; the precursor solution was mixed with the boron-nitrogen co-doped carbon nanotube aerogel and impregnated at 60°C for 8 hours.
[0042] (4) The above mixture is placed in a muffle furnace and heated to 650°C at a heating rate of 6°C / min, and held at this temperature for 8 hours to form a bifunctional catalyst S3 for carbon dioxide capture and methanation.
[0043] Example 4
[0044] A method for preparing a bifunctional catalyst for carbon dioxide capture and methanation includes:
[0045] (1) Boron-nitrogen co-doped carbon nanotubes were prepared by chemical vapor deposition using methane as the carbon source, trimethylboron and trimethylamine as the boron and nitrogen sources, respectively, with a boron-nitrogen doping ratio of 1:2.
[0046] (2) The prepared boron-nitrogen co-doped carbon nanotubes were uniformly dispersed in ethanol to form a dispersion. Subsequently, the dispersion was dried for 5 h at 60 °C and 15 MPa using supercritical carbon dioxide drying method to obtain boron-nitrogen co-doped carbon nanotube aerogel;
[0047] (3) Nickel nitrate, zirconium tetrachloride and lanthanum chloride were dissolved in a mixed solvent of water and ethanol (the volume ratio of water to ethanol was 1:2) to prepare a precursor solution, wherein the molar ratio of nickel, zirconium and lanthanum was 1:1:0.2; the precursor solution was mixed with the boron-nitrogen co-doped carbon nanotube aerogel and impregnated at 80°C for 5 hours.
[0048] (4) The above mixture is placed in a muffle furnace and heated to 700°C at a heating rate of 7°C / min, and held at this temperature for 6 hours to form a bifunctional catalyst for carbon dioxide capture and methanation, S4.
[0049] Example 5
[0050] A method for preparing a bifunctional catalyst for carbon dioxide capture and methanation includes:
[0051] (1) Boron-nitrogen co-doped carbon nanotubes were prepared by chemical vapor deposition using methane as the carbon source, trimethylboron and trimethylamine as the boron and nitrogen sources, respectively, with a boron-nitrogen doping ratio of 1:2.
[0052] (2) The prepared boron-nitrogen co-doped carbon nanotubes were uniformly dispersed in ethanol to form a dispersion. Subsequently, the dispersion was dried for 6.5 h at 50 °C and 25 MPa using supercritical carbon dioxide drying method to obtain boron-nitrogen co-doped carbon nanotube aerogel;
[0053] (3) Nickel nitrate, zirconium tetrachloride and lanthanum chloride were dissolved in a mixed solvent of water and ethanol (the volume ratio of water to ethanol was 1:2) to prepare a precursor solution, wherein the molar ratio of nickel, zirconium and lanthanum was 1:1:0.2; the precursor solution was mixed with the boron nitrogen co-doped carbon nanotube aerogel and impregnated at 70°C for 6 hours.
[0054] (4) The above mixture is placed in a muffle furnace and heated to 600°C at a heating rate of 5°C / min, and held at this temperature for 6 hours to form a bifunctional catalyst for carbon dioxide capture and methanation, S5.
[0055] The five examples above demonstrate how to prepare bifunctional catalysts with different properties based on carbon dioxide capture and methanation by adjusting the preparation conditions of boron-nitrogen co-doped carbon nanotube aerogels, the type of active metal precursor, impregnation conditions, and heat treatment conditions. These examples provide an experimental basis and reference for further optimization of catalyst performance.
[0056] To more comprehensively evaluate the performance of the prepared bifunctional catalyst based on carbon dioxide capture and methanation, the following comparative examples will be used as benchmark or comparative experiments to highlight the advantages of the catalyst of the present invention.
[0057] Comparative Example 1
[0058] Similar to Example 1, except that only nickel nitrate was used as the active metal precursor to finally obtain catalyst D1.
[0059] Comparative Example 2
[0060] Similar to Example 3, except that the carbon nanotubes were not doped with boron, resulting in catalyst D2.
[0061] Comparative Example 3
[0062] Similar to Example 3, except that the carbon nanotubes were not nitrogen-doped, resulting in catalyst D3.
[0063] Comparative Example 4
[0064] Similar to Example 3, except that the carbon nanotubes were not doped with boron or nitrogen, resulting in catalyst D4.
[0065] Comparative Example 5
[0066] Similar to Example 3, except that the solvent in the carbon nanotube dispersion was removed by vacuum drying to obtain the support, and finally catalyst D5 was obtained.
[0067] The catalysts prepared in Examples S1-S5 and Comparative Examples D1-D5 were subjected to carbon dioxide capture and methanation tests, and stability tests were also conducted. The test results are shown in Table 1. Comparative Example D1, which only supported single-metal Ni, still exhibited a certain carbon dioxide capture efficiency due to the support, but its methanation catalytic performance was poor because single-metal Ni is prone to agglomeration. In Comparative Examples D2-D4, compared to boron-nitrogen co-doping, the undoped or doped-with-only-one-heteroatom exhibited weaker CO2 adsorption. Furthermore, due to the weakened interaction between the heteroatom and the active metal, the catalyst dispersion on the support surface decreased, resulting in reduced methanation catalytic performance. In Comparative Example D5, the solvent in the carbon nanotube dispersion was removed by vacuum drying. The obtained carbon nanotubes were not in an aerogel state, and the aerogel structure is conducive to gas adsorption, thus exhibiting lower carbon dioxide capture efficiency and methane selectivity. The bifunctional catalyst prepared by the method described in this invention has high carbon dioxide capture efficiency and good methane selectivity.
[0068] Table 1 Carbon Dioxide Capture and Methanation Tests
[0069]
[0070]
[0071] Any numerical value mentioned in this invention, if there is only a two-unit interval between any minimum and any maximum value, includes all values that increase by one unit each time from the minimum to the maximum value. For example, if the amount of a component, or the value of a process variable such as temperature, pressure, or time, is stated as 50-90, in this specification it means specifically listing values such as 51-89, 52-88… and 69-71 and 70-71, etc. For non-integer values, it may be appropriately considered that a unit is 0.1, 0.01, 0.001, or 0.0001. These are merely some specifically specified examples. In this application, in a similar manner, all possible combinations of numerical values between the listed minimum and maximum values are considered to have been disclosed.
[0072] It should be noted that the embodiments described above are only for explaining the present invention and do not constitute any limitation on the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory terms, not limiting terms. Modifications can be made to the present invention within the scope of the claims, and revisions can be made to the present invention without departing from the scope and spirit of the present invention. Although the present invention described herein relates to specific methods, materials, and embodiments, it does not mean that the present invention is limited to the specific examples disclosed herein; on the contrary, the present invention can be extended to all other methods and applications with the same function.
Claims
1. A bifunctional catalyst for carbon dioxide capture and methanation, characterized in that, It includes a boron-nitrogen co-doped carbon nanotube aerogel as a support, and active components and additives of metal or metal oxide loaded on the support; The boron-nitrogen co-doped carbon nanotube aerogel is obtained by supercritical carbon dioxide drying of a boron-nitrogen co-doped carbon nanotube dispersion. This boron-nitrogen co-doped carbon nanotube aerogel has a three-dimensional network structure with continuous pores and a specific surface area of not less than 500 m². 2 / g, porosity not less than 80%; The active metal or metal oxide component and the additive are loaded onto the pores and surface of the carrier, wherein the active component is selected from any one or a mixture of one or more of metallic nickel, metallic zirconium, nickel oxide, and zirconium oxide, and the additive is any one or a mixture of two of metallic lanthanum and lanthanum oxide.
2. The bifunctional catalyst for carbon dioxide capture and methanation according to claim 1, characterized in that, The boron-nitrogen co-doped carbon nanotubes are prepared by chemical vapor deposition or arc discharge method using methane as the carbon source and trimethylboron and trimethylamine as the boron and nitrogen sources, respectively; wherein the molar ratio of boron to nitrogen doping is 1:1 to 1:
5.
3. The bifunctional catalyst for carbon dioxide capture and methanation according to claim 1, characterized in that, In the catalyst, the mass ratio of the active metal or metal oxide component and auxiliaries to the boron-nitrogen co-doped carbon nanotube aerogel support is (0.05–0.5):
1.
4. A method for preparing the bifunctional catalyst according to any one of claims 1 to 3, characterized in that, Includes the following steps: (1) First, boron-nitrogen co-doped carbon nanotubes are dispersed in a solvent to form a uniform dispersion. Then, the solvent is removed by supercritical carbon dioxide drying to form a boron-nitrogen co-doped carbon nanotube aerogel with a three-dimensional network structure of continuous pores, which serves as a catalyst support. (2) Mix the solution containing the active metal precursor with the boron-nitrogen co-doped carbon nanotube aerogel prepared in step (1) and use the impregnation method to make the active metal precursor uniformly adsorbed in the pores and surface of the boron-nitrogen co-doped carbon nanotube aerogel. (3) Heat the product obtained in step (2) to a certain temperature to convert the active metal precursor into a catalytically active metal or metal oxide form, and tightly bind it with boron-nitrogen co-doped carbon nanotube aerogel to form the carbon dioxide capture and methanation bifunctional catalyst. The heat treatment temperature in step (3) is 400-1000℃, the heat treatment time is 1-12h, and the heating rate is 1-10℃ / min; The active metal precursor is any one or a mixture of two of nickel salts and zirconium salts with lanthanum salt.
5. The method for preparing the bifunctional catalyst according to claim 4, characterized in that, The solvent for dispersing carbon nanotubes in step (1) is selected from any one or a mixture of one or more of water, ethanol, methanol, isopropanol, acetone, benzene and toluene; The solvent for the active metal precursor solution in step (2) is selected from any one or a mixture of one or more of water, ethanol, methanol, isopropanol, acetone, benzene and toluene.
6. The method for preparing the bifunctional catalyst according to claim 5, characterized in that, The solvent for the active metal precursor solution in step (2) is a mixture of water and ethanol.
7. The method for preparing the bifunctional catalyst according to claim 4, characterized in that, In the active metal precursor, the nickel salt is selected from any one or a mixture of nickel nitrate, nickel sulfate, and nickel chloride; the zirconium salt is selected from any one or a mixture of zirconium nitrate, zirconium sulfate, and zirconium chloride; and the lanthanum salt is selected from any one or a mixture of lanthanum nitrate, lanthanum sulfate, and lanthanum chloride.
8. The method for preparing the bifunctional catalyst according to claim 7, characterized in that, The active metal precursor in step (2) is a mixture of nickel salt, zirconium salt and lanthanum salt, and the molar ratio of nickel, zirconium and lanthanum is (1-3):1:(0.1-0.5).
9. The method for preparing the bifunctional catalyst according to claim 4, characterized in that, The supercritical carbon dioxide drying method described in step (1) operates at a temperature of 40–80°C, a pressure of 8–30 MPa, and a time of 1–10 h. The immersion temperature in step (2) is 30 to 100°C, and the immersion time is 1 to 20 minutes.
10. A method of using the bifunctional catalyst according to any one of claims 1 to 3, characterized in that, The above catalyst is used at a reaction temperature of 250–400°C.