Use of an actinide metal catalyst in the carbon dioxide methanation reaction

Abstract

The application discloses application of an actinide metal catalyst in a carbon dioxide methanation reaction, and the catalyst is prepared by using a carbon source and a metal source to be synthesized through a direct current arc discharge method, and has the advantages of simple process, high preparation efficiency and low cost, and can stably synthesize the actinide metal catalyst with high thermal stability. The prepared actinide metal catalyst has excellent catalytic performance on carbon dioxide hydrogenation conversion, the selectivity of product methane can reach 100%, and the carbon dioxide conversion rate can reach more than 89% under a reaction temperature of 350 DEG C.

Description

Technical Field

[0001] This invention relates to the field of actinide metal catalyst technology, and more specifically to the application of an actinide metal catalyst in the carbon dioxide methanation reaction. Background Technology

[0002] In the field of carbon dioxide methanation catalysis technology, existing catalyst systems have significant drawbacks: On the one hand, mainstream nickel-based oxide supported catalysts in industry are limited by the weak interaction between the active component and the support. Within the commonly used reaction temperature range of 200-400 °C, nickel nanoparticles tend to agglomerate and the support sinters, leading to a rapid decline in catalytic activity and making it difficult to meet the requirements for long-term stable operation. On the other hand, noble metal-based catalysts with high activity at low temperatures (such as ruthenium and rhodium-based catalysts) have significantly increased the threshold for industrial application due to their high raw material costs and scarcity, making it difficult to meet the needs of large-scale production.

[0003] Meanwhile, existing catalytic material preparation technologies have shortcomings in the composite processes of special metals (such as actinides) and traditional active metals: conventional preparation methods (such as impregnation and co-precipitation) struggle to achieve uniform dispersion of actinides and the main active metal, and cannot fully utilize the physicochemical properties of actinides to synergistically improve catalyst stability and catalytic efficiency. This results in difficulties in overcoming the performance bottlenecks of existing catalysts even when attempting to introduce actinides into the catalytic system, failing to achieve a synergistic effect of resource utilization and catalytic performance improvement. Therefore, there is an urgent need for an actinide metal catalyst with a simple preparation process and excellent high-temperature stability to promote its application in the carbon dioxide methanation reaction. Summary of the Invention

[0004] To address the aforementioned technical problems, the present invention aims to provide an application of actinide metal catalysts in the carbon dioxide methanation reaction.

[0005] The above-mentioned objective of the present invention is achieved through the following technical solution:

[0006] The application of an actinide metal catalyst in the carbon dioxide methanation reaction, wherein the preparation of the actinide metal catalyst includes the following steps:

[0007] (1) A mixed powder of a main active metal source, an actinide metal source and a carbon source is uniformly mixed and filled into a hollow graphite rod to obtain a graphite rod containing a metal source; the main active metal source is a nickel source; the actinide metal source is a thorium source or a uranium source;

[0008] (2) The graphite rod containing the metal source obtained in step (1) is subjected to quenching and reduction treatment under nitrogen atmosphere to obtain the reduced graphite rod.

[0009] (3) taking the reduced graphite rod obtained in step (2) as an anode of a direct current arc discharge cavity, taking a pure graphite rod as a cathode of the direct current arc discharge cavity, and performing direct current arc discharge in the presence of a protective gas to form the actinide metal catalyst on the direct current arc discharge cavity.

[0010] The actinide metal catalyst provided by the application can be used in the catalytic reaction of carbon dioxide hydrogenation to produce methane. The actinide metal catalyst has excellent catalytic performance for carbon dioxide hydrogenation conversion. The selectivity of the product methane can reach 100%, and the carbon dioxide conversion rate can reach more than 89% at a reaction temperature of 350 DEG C.

[0011] The actinide metal can enhance the adsorption effect of the carrier on carbon dioxide, and cooperate with the hydrogenolysis ability of the nickel metal to effectively ensure that the catalyst has high methane selectivity and high carbon dioxide conversion rate.

[0012] Further, the actinide metal catalyst comprises a graphene carrier, actinide metal nanoparticles dispersed on the graphene carrier, and main active metal nanoparticles embedded in the graphene carrier.

[0013] The size of the actinide metal nanoparticles is small, and the actinide metal nanoparticles are dispersed on the graphene carrier. The main active metal nanoparticles nickel are embedded in the defect sites of the graphene carrier to form nanoparticles of 10-20 nm.

[0014] Further, the metal nanoparticles in the actinide metal catalyst can remain stable below 500 DEG C without obvious agglomeration.

[0015] Further, in step (1), the carbon source is selected from one or more of amorphous carbon, graphite powder and activated carbon.

[0016] Further, in step (1), the main active metal source is nickel oxide.

[0017] Further, in step (1), the molar ratio of the main active metal element in the main active metal source to the carbon element in the carbon source is 1:(1-30), for example, 1:1, 1:2, 1:5, 1:10, 1:15, 1:25, 1:30, etc., including but not limited to the above-mentioned listed ratios.

[0018] In the specific embodiment, the molar ratio of the nickel element to the carbon element in the mixed powder is 1:(1-30), and preferably 1:(15-30).

[0019] Further, in step (1), the actinide metal source is thorium oxide or triuranium octaoxide, and preferably thorium oxide.

[0020] Further, in step (1), the molar ratio of the actinide metal element in the actinide metal source to the carbon element in the carbon source is 2:(15-120), such as 2:15, 2:25, 2:30, 2:40, 2:50, 2:60, 2:120, etc., including but not limited to the above-mentioned enumerated values.

[0021] In the specific embodiment, the molar ratio of the actinide metal element to the carbon element in the mixed powder is 2:(15-120), preferably 2:(15-60).

[0022] In the specific embodiment, the molar ratio of the actinide metal element, the nickel element, and the carbon element in the mixed powder is (0.5-4):1:(15-30), preferably (1-4):1:(15-30), and more preferably (1-4):1:30.

[0023] The actinide metal catalyst provided by the application has cost advantages in raw material selection. The mixed powder used for preparing the catalyst contains a thorium oxide powder. Thorium has a high crust abundance (about 3-4 times that of uranium) and is mainly derived from inexpensive nuclear waste. Compared with expensive metals such as ruthenium and rhodium, the thorium-based catalyst can greatly reduce the threshold for industrial application, thereby providing support for the large-scale promotion of carbon dioxide capture and utilization (CCU) technology.

[0024] Further, in step (1), the ratio of the diameter to the inner diameter of the hollow graphite rod is 4:(2.5-3.5).

[0025] Further, in step (2), the quenching reduction treatment is performed in a tube furnace.

[0026] Further, in step (2), the temperature of the quenching reduction treatment is 900-1100 ℃, and the time is 10-14 h.

[0027] Further, in step (2), the quenching reduction treatment is specifically as follows: under a nitrogen atmosphere, the temperature is raised to 900-1100 ℃ at a temperature raising rate of 3-7 ℃ / min, and the temperature is maintained for 10-14 h.

[0028] Further, in step (2), after the quenching reduction treatment is completed, the temperature is lowered at a temperature lowering rate of 8-12 ℃ / min.

[0029] Further, in step (3), the distance between the anode and the cathode is 1-10 mm, such as 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, etc., including but not limited to the above-mentioned enumerated values.

[0030] Further, in step (3), the reduced graphite rod has the same length as the pure graphite rod.

[0031] Further, in step (3), the two ends of the cathode and the anode are horizontally opposite in the direct current arc discharge cavity, so as to ensure that the temperature is uniform during the arc discharge process and the graphite rod can be stably and uniformly consumed.

[0032] Further, in step (3), the protective gas is selected from one or more of argon, helium and nitrogen.

[0033] Further, in step (3), the direct current arc discharge cavity is first vacuumized to a pressure less than 10 Pa, and then the protective gas is introduced; after the protective gas is introduced, the pressure of the direct current arc discharge cavity is 200-400 Torr.

[0034] Further, in step (3), the discharge current of the direct current arc discharge is 80-120 A, for example, 80 A, 90 A, 100 A, 110 A, 120 A, etc., including but not limited to the above-mentioned current values.

[0035] Further, the actinium series metal catalyst is filled into the reaction tube, and a mixed gas of carbon dioxide and hydrogen is introduced to perform a catalytic reaction under the action of pressure.

[0036] In a specific embodiment, the actinium series metal catalyst is tabletted and sieved, and catalyst particles of 30-40 mesh are selected; the 30-40 mesh catalyst particles are filled into the reaction tube, and a mixed gas of carbon dioxide and hydrogen is introduced to perform a catalytic reaction under the action of pressure.

[0037] Further, the volume ratio of carbon dioxide to hydrogen in the mixed gas is 1:4.

[0038] Further, the pressure is 2-3 MPa, preferably 2.5 MPa.

[0039] Further, the space velocity of the introduction of the mixed gas is 5800-6000 mL / (g·h).

[0040] Further, the temperature of the catalytic reaction is 200-400 ℃, preferably 250-400 ℃, and more preferably 300-350 ℃.

[0041] The above technical solutions of the present application have the following beneficial effects compared with the prior art:

[0042] 1. The actinium metal catalyst provided by the application has excellent performance, when applied to the carbon dioxide methanation reaction, not only can start the reaction at a low activation temperature (250 DEG C), but also can efficiently activate carbon dioxide and hydrogen and realize 100% selectivity of the methane product; and at a catalytic temperature of 350 DEG C, the carbon dioxide conversion rate can reach more than 89%, compared with the pure nickel catalyst, the doping of the actinium metal significantly improves the carbon dioxide conversion efficiency.

[0043] 2. The application realizes high-value resource utilization of actinium metal waste, and converts idle actinium metal waste into a catalytically active component; meanwhile, the catalyst is prepared by synthesizing a carbon source and a metal source by a direct current arc discharge method, and has the advantages of simple process, high preparation efficiency and low cost, and can stably synthesize an actinium metal catalyst with high thermal stability, and is suitable for batch production.

[0044] 3. The actinium metal catalyst provided by the application has excellent thermal stability and long-term catalytic stability, due to the high melting point (1750 DEG C) and strong metal-support interaction of thorium, the thorium and nickel metal nanoparticles in the catalyst can maintain stable nanoparticle size in the range of 20-500 DEG C without obvious agglomeration; even if the carbon dioxide reduction is continuously catalyzed for 100 h, the catalytic activity does not change significantly. BRIEF DESCRIPTION OF DRAWINGS

[0045] Figure 1 X-ray diffraction spectra of the thorium-doped carbon-based nickel catalyst (ThNi@C) prepared in Example 1 and the carbon-based nickel catalyst (Ni@C) prepared in Comparative Example 2.

[0046] Figure 2 X-ray photoelectron spectrograms of the thorium-doped carbon-based nickel catalyst prepared in Example 1 and the carbon-based nickel catalyst prepared in Comparative Example 2.

[0047] Figure 3 Transmission electron microscope (TEM) image (scale is 50 nm) of the thorium-doped carbon-based nickel catalyst prepared in Example 1.

[0048] Figure 4 TEM image (scale is 10 nm) of the thorium-doped carbon-based nickel catalyst prepared in Example 1.

[0049] Figure 5 The carbon dioxide conversion rate comparison chart of the carbon dioxide methanation reaction catalyzed by the thorium-doped carbon-based nickel catalyst prepared in Example 1, the uranium-doped carbon-based nickel catalyst prepared in Example 5, and the carbon-based nickel catalyst prepared in Comparative Examples 2, 5, 6 and 7.

[0050] Figure 6 Stability test chart of the carbon dioxide methanation reaction catalyzed by the thorium-doped carbon-based nickel catalyst prepared in Example 1. Detailed Implementation

[0051] Unless otherwise defined, 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 invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0052] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0053] Unless otherwise specified, the experimental methods used in the following examples are conventional methods, and the materials and reagents used are commercially available.

[0054] Example 1

[0055] The application of a thorium-doped carbon-based nickel catalyst in the carbon dioxide methanation reaction involves pressing and sieving the thorium-doped carbon-based nickel catalyst to obtain 40-mesh catalyst particles. Then, 500 mg of the 40-mesh catalyst particles are filled into a reaction tube, and a mixture of carbon dioxide and hydrogen with a volume ratio of 1:4 is introduced. The catalytic reaction is carried out at a pressure of 2.5 MPa, a temperature of 350 °C, and a gas hourly space velocity of 6000 mL / (g·h).

[0056] The preparation of the thorium-doped carbon-based nickel catalyst in Example 1 includes the following steps:

[0057] (1) Thorium oxide (99% purity), nickel oxide (99% purity), and graphite powder (99.99% purity) are mixed uniformly in a Th:Ni:C molar ratio of 1:4:30. The resulting mixed powder is filled into a hollow graphite rod with a diameter of 8 mm and an inner diameter of 6 mm to obtain a graphite rod containing a metal source.

[0058] (2) The graphite rod containing the metal source obtained in step (1) was placed in a tube furnace under a nitrogen atmosphere for quenching and reduction treatment. The temperature was raised to 1000 ℃ at a heating rate of 5 ℃ / min, held for 12 h, and then cooled to room temperature at a cooling rate of 10 ℃ / min to obtain the reduced graphite rod.

[0059] (3) The reduced graphite rod obtained in step (2) is used as an anode of a direct current arc discharge cavity, and another pure graphite rod with a diameter of 8 mm is used as a cathode of the direct current arc discharge cavity. The two graphite rod ends of the cathode and the anode are horizontally opposite, and the distance between the ends of the anode and the cathode is kept at 10 mm. The direct current arc discharge cavity is vacuumized to a pressure of less than 10 Pa, and then high-purity helium is introduced. After the introduction of the high-purity helium, the pressure in the direct current arc discharge cavity is 200 Torr. The electric welding machine is turned on, and the discharge current is kept at 100 A. The direct current arc discharge is started. During the discharge process, the anode is continuously consumed until the anode graphite rod is consumed. The discharge is stopped, and the discharge process lasts about 5 min. The black powder generated on the inner wall of the direct current arc discharge cavity is a thorium-doped carbon-based nickel catalyst powder.

[0060] Example 2

[0061] The thorium-doped carbon-based nickel catalyst is pressed, sieved, and treated to obtain 40-mesh catalyst particles. Then, 500 mg of the 40-mesh catalyst particles are filled into a reaction tube, and a mixed gas of carbon dioxide and hydrogen with a volume ratio of 1:4 is introduced. The catalytic reaction is carried out at a pressure of 2.5 MPa, a temperature of 350°C, and a mixed gas inlet space velocity of 6000 mL / (g·h).

[0062] The preparation of the thorium-doped carbon-based nickel catalyst in Example 2 is basically the same as that in Example 1, except that in step (1), thorium oxide (purity 99%), nickel oxide (purity 99%), and graphite powder (purity 99.99%) are uniformly mixed in a molar ratio of Th: Ni: C of 2:1:60.

[0063] Example 3

[0064] The thorium-doped carbon-based nickel catalyst is pressed, sieved, and treated to obtain 40-mesh catalyst particles. Then, 500 mg of the 40-mesh catalyst particles are filled into a reaction tube, and a mixed gas of carbon dioxide and hydrogen with a volume ratio of 1:4 is introduced. The catalytic reaction is carried out at a pressure of 2.5 MPa, a temperature of 350°C, and a mixed gas inlet space velocity of 6000 mL / (g·h).

[0065] The preparation of the thorium-doped carbon-based nickel catalyst in Example 3 is basically the same as that in Example 1, except that in step (1), thorium oxide (purity 99%), nickel oxide (purity 99%), and graphite powder (purity 99.99%) are uniformly mixed in a molar ratio of Th: Ni: C of 1:1:30.

[0066] Example 4

[0067] The application of a thorium-doped carbon-based nickel catalyst in a carbon dioxide methanation reaction. The thorium-doped carbon-based nickel catalyst is pressed into tablets and sieved to obtain 40-mesh catalyst particles. Then, 500 mg of the 40-mesh catalyst particles are filled into a reaction tube, and a mixed gas of carbon dioxide and hydrogen with a volume ratio of 1:4 is introduced. The catalytic reaction is carried out at a pressure of 2.5 MPa, a temperature of 350°C, and a mixed gas inlet space velocity of 6000 mL / (g·h).

[0068] The preparation of the thorium-doped carbon-based nickel catalyst in Example 4 is basically the same as that in Example 1, except that in step (1), thorium oxide (purity 99%), nickel oxide (purity 99%), and graphite powder (purity 99.99%) are uniformly mixed in a molar ratio of Th:Ni:C of 1:2:30.

[0069] Example 5

[0070] The application of a thorium-doped carbon-based nickel catalyst in a carbon dioxide methanation reaction. The thorium-doped carbon-based nickel catalyst is pressed into tablets and sieved to obtain 40-mesh catalyst particles. Then, 500 mg of the 40-mesh catalyst particles are filled into a reaction tube, and a mixed gas of carbon dioxide and hydrogen with a volume ratio of 1:4 is introduced. The catalytic reaction is carried out at a pressure of 2.5 MPa, a temperature of 350°C, and a mixed gas inlet space velocity of 6000 mL / (g·h).

[0071] The preparation of the thorium-doped carbon-based nickel catalyst in Example 4 is basically the same as that in Example 1, except that in step (1), thorium oxide (purity 99%), nickel oxide (purity 99%), and graphite powder (purity 99.99%) are uniformly mixed in a molar ratio of Th:Ni:C of 1:2:30.

[0072] Example 6

[0073] The application of a thorium-doped carbon-based nickel catalyst in a carbon dioxide methanation reaction. The thorium-doped carbon-based nickel catalyst is pressed into tablets and sieved to obtain 40-mesh catalyst particles. Then, 500 mg of the 40-mesh catalyst particles are filled into a reaction tube, and a mixed gas of carbon dioxide and hydrogen with a volume ratio of 1:4 is introduced. The catalytic reaction is carried out at a pressure of 2.5 MPa, a temperature of 350°C, and a mixed gas inlet space velocity of 6000 mL / (g·h).

[0074] The preparation of the thorium-doped carbon-based nickel catalyst in Example 6 is the same as that in Example 1.

[0075] Example 7

[0076] The application of a thorium-doped carbon-based nickel catalyst in a carbon dioxide methanation reaction, the thorium-doped carbon-based nickel catalyst is subjected to tabletting and sieving to obtain 40-mesh catalyst particles, then 500 mg of the 40-mesh catalyst particles are filled into a reaction tube, a mixed gas of carbon dioxide and hydrogen with a volume ratio of 1:4 is introduced, and the catalytic reaction is carried out at a pressure of 2.5 MPa, a temperature of 300 DEG C, and a mixed gas introduction space velocity of 6000 mL / (g.h).

[0077] The preparation of the thorium-doped carbon-based nickel catalyst in Example 7 is the same as that in Example 1.

[0078] Example 8

[0079] The application of a thorium-doped carbon-based nickel catalyst in a carbon dioxide methanation reaction, the thorium-doped carbon-based nickel catalyst is subjected to tabletting and sieving to obtain 40-mesh catalyst particles, then 500 mg of the 40-mesh catalyst particles are filled into a reaction tube, a mixed gas of carbon dioxide and hydrogen with a volume ratio of 1:4 is introduced, and the catalytic reaction is carried out at a pressure of 2.5 MPa, a temperature of 400 DEG C, and a mixed gas introduction space velocity of 6000 mL / (g.h).

[0080] The preparation of the thorium-doped carbon-based nickel catalyst in Example 8 is the same as that in Example 1.

[0081] Comparative Example 1

[0082] The application of a carbon-based catalyst in a carbon dioxide methanation reaction, the carbon-based catalyst is subjected to tabletting and sieving to obtain 40-mesh catalyst particles, then 500 mg of the 40-mesh catalyst particles are filled into a reaction tube, a mixed gas of carbon dioxide and hydrogen with a volume ratio of 1:4 is introduced, and the catalytic reaction is carried out at a pressure of 2.5 MPa, a temperature of 350 DEG C, and a mixed gas introduction space velocity of 6000 mL / (g.h).

[0083] The preparation of the carbon-based catalyst in Comparative Example 1 comprises the following steps:

[0084] (1) graphite powder (purity 99%) is filled into a hollow graphite rod with a diameter of 8 mm and an inner diameter of 6 mm to obtain a graphite rod containing graphite powder;

[0085] (2) the graphite rod containing graphite powder obtained in step (1) is placed in a tube furnace for quenching reduction treatment under a nitrogen atmosphere, heated to 1000 DEG C at a heating rate of 5 DEG C / min, and then cooled to room temperature at a cooling rate of 10 DEG C / min to obtain a reduced graphite rod;

[0086] (3) The reduced graphite rod obtained in step (2) is used as an anode of a direct current arc discharge cavity, and another pure graphite rod with a diameter of 8 mm is used as a cathode of the direct current arc discharge cavity. The two graphite rod ends of the cathode and the anode are horizontally opposite, and the distance between the ends of the anode and the cathode is kept at 10 mm. The direct current arc discharge cavity is vacuumized to a pressure of less than 10 Pa, and then high-purity helium is introduced. After the introduction of the high-purity helium, the pressure in the direct current arc discharge cavity is 200 Torr. The electric welding machine is turned on, and the discharge current is kept at 100 A. The direct current arc discharge is started. During the discharge process, the anode is continuously consumed until the anode graphite rod is consumed. The discharge is stopped, and the discharge process lasts about 5 min. The black powder generated on the inner wall of the direct current arc discharge cavity is a carbon-based catalyst powder.

[0087] Comparative Example 2

[0088] An application of a carbon-based nickel catalyst in a carbon dioxide methanation reaction. The carbon-based nickel catalyst is pressed, sieved, and treated to obtain 40-mesh catalyst particles. Then, 500 mg of the 40-mesh catalyst particles are filled into a reaction tube, and a mixed gas of carbon dioxide and hydrogen with a volume ratio of 1:4 is introduced. The catalytic reaction is carried out at a pressure of 2.5 MPa, a temperature of 350 ℃, and a mixed gas inlet space velocity of 6000 mL / (g·h).

[0089] The preparation of the carbon-based nickel catalyst in Comparative Example 2 is basically the same as that in Example 1, except that in step (1), nickel oxide (purity 99%) and graphite powder (purity 99.99%) are uniformly mixed at a molar ratio of Ni:C of 4:30. The obtained mixed powder is filled into a hollow graphite rod with a diameter of 8 mm and an inner diameter of 6 mm to obtain a graphite rod containing a metal source.

[0090] Comparative Example 3

[0091] An application of a carbon-based nickel catalyst in a carbon dioxide methanation reaction. The carbon-based nickel catalyst is pressed, sieved, and treated to obtain 40-mesh catalyst particles. Then, 500 mg of the 40-mesh catalyst particles are filled into a reaction tube, and a mixed gas of carbon dioxide and hydrogen with a volume ratio of 1:4 is introduced. The catalytic reaction is carried out at a pressure of 2.5 MPa, a temperature of 250 ℃, and a mixed gas inlet space velocity of 6000 mL / (g·h).

[0092] The preparation of the carbon-based nickel catalyst in Comparative Example 3 is the same as that in Comparative Example 2.

[0093] Comparative Example 4

[0094] The application of a thorium-doped carbon-based catalyst in a carbon dioxide methanation reaction, the thorium-doped carbon-based catalyst is subjected to tabletting and sieving to obtain 40-mesh catalyst particles, then 500 mg of the 40-mesh catalyst particles are filled into a reaction tube, a mixed gas of carbon dioxide and hydrogen with a volume ratio of 1:4 is introduced, and the catalytic reaction is carried out at a pressure of 2.5 MPa, a temperature of 350 ℃, and a mixed gas introduction space velocity of 6000 mL / (g·h).

[0095] The preparation of the thorium-doped carbon-based catalyst in Comparative Example 4 is basically the same as that in Example 1, except that in step (1), thorium oxide (purity 99%) and graphite powder (purity 99.99%) are uniformly mixed at a Th:C molar ratio of 4:30, and the obtained mixed powder is filled into a hollow graphite rod with a diameter of 8 mm and an inner diameter of 6 mm to obtain a graphite rod containing a metal source.

[0096] Comparative Example 5

[0097] The application of a cerium-doped carbon-based nickel catalyst in a carbon dioxide methanation reaction, the cerium-doped carbon-based nickel catalyst is subjected to tabletting and sieving to obtain 40-mesh catalyst particles, then 500 mg of the 40-mesh catalyst particles are filled into a reaction tube, a mixed gas of carbon dioxide and hydrogen with a volume ratio of 1:4 is introduced, and the catalytic reaction is carried out at a pressure of 2.5 MPa, a temperature of 350 ℃, and a mixed gas introduction space velocity of 6000 mL / (g·h).

[0098] The preparation of the cerium-doped carbon-based nickel catalyst in Comparative Example 5 is basically the same as that in Example 1, except that in step (1), cerium oxide (purity 99%), nickel oxide (purity 99%), and graphite powder (purity 99.99%) are uniformly mixed at a Ce:Ni:C molar ratio of 1:4:30.

[0099] Comparative Example 6

[0100] The application of a zirconium-doped carbon-based nickel catalyst in a carbon dioxide methanation reaction, the zirconium-doped carbon-based nickel catalyst is subjected to tabletting and sieving to obtain 40-mesh catalyst particles, then 500 mg of the 40-mesh catalyst particles are filled into a reaction tube, a mixed gas of carbon dioxide and hydrogen with a volume ratio of 1:4 is introduced, and the catalytic reaction is carried out at a pressure of 2.5 MPa, a temperature of 350 ℃, and a mixed gas introduction space velocity of 6000 mL / (g·h).

[0101] The preparation of the thorium-doped carbon-based nickel catalyst in Comparative Example 6 was basically the same as that in Example 1, except that in step (1), zirconium oxide (purity 99%), nickel oxide (purity 99%) and graphite powder (purity 99.99%) were uniformly mixed in a molar ratio of Zr: Ni: C = 1:4:30.

[0102] Comparative Example 7

[0103] The application of a thorium-doped carbon-based nickel catalyst in a carbon dioxide methanation reaction, 500 mg of 40-mesh catalyst particles were filled into a reaction tube, and a mixed gas of carbon dioxide and hydrogen in a volume ratio of 1:4 was introduced, and the catalytic reaction was carried out under a pressure of 2.5 MPa, a temperature of 350°C, and a mixed gas inlet space velocity of 6000 mL / (g·h).

[0104] The preparation of the thorium-doped carbon-based nickel catalyst in Comparative Example 7 was basically the same as that in Example 1, except that the quenching reduction treatment of step (2) was not performed.

[0105] Test Example 1

[0106] The thorium-doped carbon-based nickel catalyst prepared in Example 1 and the carbon-based nickel catalyst prepared in Comparative Example 2 were subjected to X-ray diffraction analysis and X-ray photoelectron spectroscopy analysis.

[0107] The X-ray diffraction spectra of the thorium-doped carbon-based nickel catalyst prepared in Example 1 and the carbon-based nickel catalyst prepared in Comparative Example 2 are shown in FIG. 1. Figure 1 As shown in FIG. 1, the characteristic diffraction peak of the graphene carrier in the carbon-based nickel catalyst did not shift or mutate in intensity after thorium doping, indicating that the introduction of thorium did not destroy the crystal structure of the graphene carrier, and the carrier had good stability; at the same time, there was no characteristic diffraction peak of thorium oxide (no obvious sharp peak shape) in the spectrum, indicating that the preparation method of the present application can make the thorium nanoparticles exist in the graphene carrier in a highly dispersed state, avoiding the formation of obvious crystal phase due to thorium agglomeration.

[0108] The X-ray photoelectron spectroscopy spectra of the thorium-doped carbon-based nickel catalyst prepared in Example 1 and the carbon-based nickel catalyst prepared in Comparative Example 2 are shown in FIG. 2. Figure 2 As shown in FIG. 2, the 2p orbital binding energy of Ni in the carbon-based nickel catalyst did not have an obvious charge shift after thorium doping, which indicated that there was no obvious electron transfer or chemical bond interaction between thorium and nickel; further deduced from the catalytic reaction mechanism, thorium mainly captured carbon dioxide molecules through physical adsorption or surface site adsorption in the carbon dioxide methanation reaction, thereby assisting to improve the enrichment efficiency of the reaction raw materials.

[0109] The TEM image of the thorium-doped carbon-based nickel catalyst prepared in Example 1 is shown in FIG. 3. Figure 3and Figure 4 As shown in the figure, it can be seen from the figure that the thorium nanoparticles are highly dispersed in the graphene carrier, and the nickel is successfully loaded on the graphene carrier, that is, the synthesis method provided by the present application successfully prepares the thorium-doped carbon-based nickel catalyst.

[0110] Test Example 2

[0111] The carbon-based nickel catalysts prepared in Examples 1-8 and the catalysts prepared in Comparative Examples 1-7 were subjected to catalyst performance evaluation on a fixed-bed continuous flow reactor-GC gas chromatograph, and the performance results are shown in Table 1:

[0112] Table 1

[0113]

[0114] As can be seen from Table 1, the thorium-doped carbon-based nickel catalysts prepared in Examples 1-4 and 6-8 all exhibit excellent product selectivity in the carbon dioxide methanation reaction, and the methane selectivity all reaches 100%, and the catalytic performance of Example 1 is particularly outstanding, at a reaction temperature of 350 ℃, the carbon dioxide conversion rate is 89.94%; at a reaction temperature of 400 ℃, the carbon dioxide conversion rate is 94.09%.

[0115] Further comparison of Examples 1-4 with Comparative Examples 1, 2 and 4 can further find that on the one hand, the catalysts without adding nickel source (Comparative Examples 1 and 4) cannot completely realize the catalytic reduction of carbon dioxide, which proves that nickel is the core active component in the catalytic system; on the other hand, compared with the carbon-based nickel catalyst without doping thorium (Comparative Example 2), the introduction of thorium can significantly improve the catalytic efficiency of the catalyst, which reflects the optimization effect of thorium on the catalytic performance.

[0116] In addition, the comparison results of Example 1 and Example 5, Comparative Example 5 show that: after doping uranium (Example 5) or cerium (Comparative Example 5) which are actinide metals or rare earth metals into the carbon-based nickel catalyst, although there is a certain promoting effect on the carbon dioxide methanation reaction, but the catalytic efficiency is lower than that of the thorium-doped catalyst (Example 1), which further confirms the advantage of thorium in improving the carbon dioxide conversion efficiency in the catalytic system.

[0117] The comparison results of Example 1 and Comparative Example 6 show that: doping zirconium metal which is in the same main group into the carbon-based nickel catalyst will inhibit the carbon dioxide methanation reaction. This phenomenon may be due to the fact that under this synthesis method, zirconium metal and nickel metal form an alloy structure, thereby reducing the number or activity strength of the active sites of nickel metal.

[0118] The comparison results of example 1 and comparative example 7 show that the activity of the catalyst without quenching reduction treatment for catalyzing the carbon dioxide methanation reaction is significantly lower than that of the catalyst with quenching reduction treatment, indicating that the quenching reduction process plays a key role in improving the reaction activity of the catalyst.

[0119] Figure 5 The carbon dioxide conversion rate comparison chart of the thorium-doped carbon-based nickel catalyst prepared in example 1, the uranium-doped carbon-based nickel catalyst prepared in example 5, and the carbon-based nickel catalysts prepared in comparative example 2, comparative example 5, comparative example 6 and comparative example 7 for catalyzing the carbon dioxide methanation reaction.

[0120] Figure 6 The stability test chart of the thorium-doped carbon-based nickel catalyst prepared in example 1 for catalyzing the carbon dioxide methanation reaction. Under the conditions of a pressure of 2.5 MPa, a temperature of 350 DEG C, and a mixed gas of carbon dioxide and hydrogen with a volume ratio of 1:4, the catalyst maintains a high catalytic activity during the 100 h continuous operation, indicating that the catalyst with excellent thermal stability is successfully synthesized by the preparation method adopted in the present application.

[0121] Obviously, the above examples of the present application are only examples for clearly illustrating the present application, and are not intended to limit the embodiments of the present application. Those skilled in the art should understand that on the basis of the above description, other different forms of changes or variations can also be made. Here, it is not necessary and also impossible to exhaust all the embodiments. Any modification, equivalent replacement and improvement, etc. made within the spirit and principle of the present application should be included in the protection scope of the claims of the present application.

Claims

1. The application of an actinide metal catalyst in the carbon dioxide methanation reaction, characterized in that, The preparation of the actinide metal catalyst includes the following steps: (1) A mixed powder of a main active metal source, an actinide metal source and a carbon source is uniformly mixed and filled into a hollow graphite rod to obtain a graphite rod containing a metal source; the main active metal source is a nickel source; the actinide metal source is a thorium source or a uranium source; (2) The graphite rod containing the metal source obtained in step (1) is subjected to quenching and reduction treatment under nitrogen atmosphere to obtain the reduced graphite rod. (3) Using the reduced graphite rod obtained in step (2) as the anode of the DC arc discharge cavity and the pure graphite rod as the cathode of the DC arc discharge cavity, DC arc discharge is performed in the presence of protective gas, and the actinide metal catalyst is formed on the DC arc discharge cavity.

2. The application according to claim 1, characterized in that, The actinide metal catalyst comprises a graphene support, actinide metal nanoparticles dispersed on the graphene support, and main active metal nanoparticles embedded within the graphene support.

3. The application according to claim 1, characterized in that, In step (1), the main active metal source is nickel oxide; the molar ratio of the main active metal element in the main active metal source to the carbon element in the carbon source is 1:(1-30).

4. The application according to claim 1, characterized in that, In step (1), the actinide metal source is thorium oxide or uranium octaoxide.

5. The application according to claim 1, characterized in that, In step (1), the molar ratio of actinide metal elements in the actinide metal source to carbon elements in the carbon source is 2:(15-120).

6. The application according to claim 1, characterized in that, In step (2), the quenching reduction treatment is performed at a temperature of 900-1100 ℃ for 10-14 h.

7. The application according to claim 1, characterized in that, The actinide metal catalyst is filled into a reaction tube, and a mixture of carbon dioxide and hydrogen is introduced to carry out the catalytic reaction under pressure.

8. The application according to claim 7, characterized in that, The pressure is 2-3 MPa.

9. The application according to claim 7, characterized in that, The gas velocity of the mixture is 5800-6000 mL / (g·h).

10. The application according to claim 7, characterized in that, The temperature of the catalytic reaction is 200-400 ℃.

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