Carbon dioxide (CO2) methanation catalyst, production method for the same, methane production device using the same, and methane production method using the same

Abstract

To provide a carbon dioxide (CO2) methanation catalyst using nickel with excellent catalytic activity in a low temperature range of 300°C or lower, a production method for the same, a methane production device using the same, and a methane production method using the same.SOLUTION: A carbon dioxide (CO2) methanation catalyst is composed of a porous material comprising nickel oxide or nickel metal, RE oxide (where RE is at least one element selected from the group consisting of Y, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu), carbon, and optionally, at least one additional oxide selected from the group consisting of aluminum oxide, yttria-stabilized zirconia (YSZ), zirconium oxide, magnesium oxide, calcium oxide, and silicon oxide.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a carbon dioxide (CO2) methanation catalyst, a method for producing the same, a methane production apparatus using the same, and a method for producing methane using the same. [Background technology]

[0002] To prevent global warming, it is necessary to capture and effectively use carbon dioxide (CO2) emitted from power generation, steel manufacturing, and other plants. Methanation is known as a technology for effectively using CO2. Methanation is a reaction that uses a catalyst to produce methane (CH4) from CO2 and hydrogen (H2), as shown in the following formula. CO2+4H2⇔CH4+2H2O

[0003] As a catalyst for a methanation reaction (methanation catalyst), a catalyst in which metal particles such as ruthenium (Ru) or nickel (Ni) are supported on an oxide is used (see, for example, Non-Patent Document 1 and Patent Documents 1 to 5).

[0004] According to Non-Patent Document 1, precious metal catalysts such as Ru exhibit higher methanation catalytic activity at lower temperatures (below 300°C) than base metal catalysts such as Ni. However, precious metals are expensive and resources are limited, so catalysts mainly made of base metals such as Ni are desirable as methanation catalysts. For this reason, methanation catalysts using Ni have been actively researched in recent years.

[0005] Patent documents 1 to 5 all report that catalysts in which Ni is supported on oxides such as cerium oxide (CeO2) and zirconium oxide (ZrO2) have high methanation catalytic activity. However, the effect of the methanation catalytic activity at low temperatures (below 300°C) is lower than that of precious metal catalysts and is not sufficient. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2000-254508 A [Patent Document 2] JP 2009-034650 A [Patent Document 3] JP 2010-022944 A [Patent Document 4] Japanese Patent Application Publication No. 8-127544 [Patent Document 5] JP 2020-37535 A [Non-patent literature]

[0007] [Non-Patent Document 1] Gabriella Garbarino et al., International Journal of Hydrogen Energy, 40(30), 9171-9182 Summary of the Invention [Problem to be solved by the invention]

[0008] In view of the above, an object of the present invention is to provide a carbon dioxide (CO2) methanation catalyst using nickel that has excellent catalytic activity at low temperatures of 300°C or less, a method for producing the same, a methane production apparatus using the same, and a methane production method using the same. [Means for solving the problem]

[0009] The carbon dioxide (CO2) methanation catalyst according to the present invention comprises a porous material containing nickel oxide or nickel metal, an oxide of RE (wherein RE is at least one element selected from the group consisting of yttrium (Y), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu), carbon, and, if necessary, at least one further oxide selected from the group consisting of aluminum oxide, yttria-stabilized zirconia (YSZ), zirconium oxide, magnesium oxide, calcium oxide, and silicon oxide, thereby solving the above-mentioned problems. The carbon may be amorphous carbon. When the entire porous material is taken as 100% by mass, the nickel oxide or nickel metal may be contained in a range of 5% by mass or more and 60% by mass or less, calculated as nickel metal, the RE oxide may be contained in a range of 15% by mass or more and 85% by mass or less, the carbon may be contained in a range of more than 0% by mass and less than 70% by mass, and the further oxide may be contained in a range of 0% by mass or more and 55% by mass or less. The nickel oxide or nickel metal may be contained in a range of 7 mass% or more and 55 mass% or less in terms of nickel metal, the oxide of RE may be contained in a range of 17.5 mass% or more and 75 mass% or less, the carbon may be contained in a range of 5 mass% or more and 50 mass% or less, and the further oxide may be contained in a range of 0 mass% or more and 52.5 mass% or less. The nickel oxide or nickel metal may be contained in a range of 10% by mass or more and 50% by mass or less, calculated as nickel metal, the oxide of RE may be contained in a range of 20% by mass or more and 70% by mass or less, the carbon may be contained in a range of 20% by mass or more and 50% by mass or less, and the further oxide may be contained in a range of 0% by mass or more and 35% by mass or less. The RE may be yttrium and / or ytterbium. The porous material may have micropores, mesopores and macropores. The specific surface area of ​​the porous material by the BET method is 10 m 2 / g or more 300m 2 / g or less. The specific surface area of ​​the porous material by the BET method is 60 m 2 / g or more 300m 2 / g or less. The micropore surface area of ​​the porous material by t-plot method is 2 m 2 / g or more 240m 2 / g or less. The micropore surface area of ​​the porous material by t-plot method is 25m 2 / g or more 240m 2 / g or less. The ratio of micropores in the porous material may be in the range of 10% to 85%. The ratio of micropores in the porous material may be in the range of 40% to 85%. The porous material may have mesopores whose average pore size measured by the BJH method falls within the range of 5 nm to 16 nm. The method for producing a carbon dioxide methanation catalyst according to the present invention comprises preparing a mixture of a nickel salt, an oxide of RE (wherein RE is at least one element selected from the group consisting of yttrium (Y), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu)), and, if necessary, at least one further oxide selected from the group consisting of aluminum oxide, yttria-stabilized zirconia (YSZ), zirconium oxide, magnesium oxide, calcium oxide, and silicon oxide, calcining the mixture in an oxidizing atmosphere, mixing the calcined mixture with at least one resin selected from the group consisting of phenol resins, furan resins, and divinylbenzene resins to prepare a resin mixture, and carbonizing the resin mixture, thereby solving the above-mentioned problem. The method for producing a carbon dioxide methanation catalyst according to the present invention comprises preparing a resin mixture of an oxide of RE (wherein RE is at least one element selected from the group consisting of yttrium (Y), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu)), at least one resin selected from the group consisting of a phenol resin, a furan resin, and a divinylbenzene resin, and, as necessary, at least one further oxide selected from the group consisting of aluminum oxide, yttria-stabilized zirconia (YSZ), zirconium oxide, magnesium oxide, calcium oxide, and silicon oxide; carbonizing the resin mixture; impregnating the oxide-containing porous carbon body obtained by the carbonization with an aqueous solution of a nickel salt; and firing the oxide-containing porous carbon body impregnated with the nickel salt in an oxidizing atmosphere, thereby solving the above-mentioned problem. The nickel salt may be at least one salt selected from the group consisting of nickel nitrate, sulfate, chlorate, bromate, iodate, perbromate, metaperiodate, and thiocyanate. The methane production apparatus according to the present invention includes a reaction vessel that contains a catalyst for producing methane from carbon dioxide and hydrogen, and the catalyst is the carbon dioxide methanation catalyst, thereby solving the above-mentioned problems. The method for producing methane according to the present invention comprises reducing the carbon dioxide methanation catalyst under a reducing atmosphere, heating the reduced methanation catalyst, and introducing carbon dioxide and hydrogen into the reduced methanation catalyst, thereby solving the above-mentioned problem. Effect of the Invention

[0010] The carbon dioxide methanation catalyst according to the present invention is made of a porous material containing nickel oxide or nickel metal, an oxide of RE (wherein RE is at least one element selected from the group consisting of yttrium (Y), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu)), carbon, and, if necessary, at least one further oxide selected from the group consisting of aluminum oxide, yttria-stabilized zirconia (YSZ), zirconium oxide, magnesium oxide, calcium oxide, and silicon oxide. The methanation catalyst of the present invention is effective in reducing costs because it does not use a precious metal such as Ru. Since the methanation catalyst of the present invention is a porous material, the reactive molecules of carbon dioxide and hydrogen quickly diffuse into the pores, making it easy for the methanation reaction to occur. Therefore, high methanation catalytic activity can be obtained even at low temperatures of 300°C or less. In particular, the methanation catalytic activity can be significantly improved by combining nickel oxide or nickel metal with a specific RE oxide. By using the methanation catalyst of the present invention, a methane production method and methane production apparatus with high methane production efficiency can be provided. The above-mentioned method for producing the methanation catalyst of the present invention does not require special techniques or equipment, making it possible to reduce costs and advantageous for mass production. [Brief description of the drawings]

[0011] [Figure 1] Schematic diagram showing a carbon dioxide methanation catalyst according to the present invention. [Diagram 2] A flow chart showing the steps of producing a carbon dioxide methanation catalyst according to the present invention. [Diagram 3] Another flow chart showing the process for producing a carbon dioxide methanation catalyst according to the present invention. [Figure 4] Flowchart showing the process for producing methane according to the present invention [Diagram 5] Schematic diagram showing a methane production apparatus according to the present invention. [Figure 6]FIG. 3 shows an XRD pattern of the mixture obtained in step S220 of FIG. 2 in Example 1. [Figure 7] A diagram showing the appearance of the sample in Example 1 [Figure 8] FIG. 1 shows the XRD pattern of the sample of Example 1. [Figure 9] FIG. 1 shows an SEM image of a sample from Example 3. [Figure 10] FIG. 1 shows an SEM image of a sample of Example 11. [Figure 11] FIG. 1 shows an SEM image of a sample of Example 12. [Figure 12] FIG. 1 shows an SEM image of a sample of Example 13. [Figure 13] FIG. 1 shows an SEM image of a sample of Example 15. [Figure 14] Graph showing nitrogen gas adsorption / desorption isotherms for the sample of Example 2 [Figure 15] Graph showing pore size distribution of sample in Example 2 DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Note that like elements are given like reference numerals and their description will be omitted. (Embodiment 1) In the first embodiment, a carbon dioxide methanation catalyst and a production method thereof according to the present invention will be described.

[0013] FIG. 1 is a schematic diagram showing a carbon dioxide methanation catalyst according to the present invention.

[0014] The carbon dioxide (CO2) methanation catalyst 100 of the present invention is made of a porous material containing nickel oxide or nickel metal, an oxide of RE (wherein RE is at least one element selected from the group consisting of yttrium (Y), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu)), and carbon. The methanation catalyst 100 of the present invention does not contain a precious metal such as Ru (ruthenium), and is therefore effective in reducing costs. In addition, since the methanation catalyst 100 of the present invention is a porous material, the reactive molecules of carbon dioxide and hydrogen quickly diffuse into the pores, making it easy for the methanation reaction to occur. Therefore, even at a low temperature of 300°C or less, high methanation catalytic activity can be obtained. In particular, the methanation catalytic activity can be significantly improved by combining nickel oxide or nickel metal with a specific RE oxide.

[0015] The methanation catalyst 100 of the present invention may contain at least one further oxide selected from the group consisting of aluminum oxide, yttria-stabilized zirconia (YSZ), zirconium oxide, magnesium oxide, calcium oxide, and silicon oxide, as necessary. These oxides function as catalyst supports. By containing these oxides, the amount of the above-mentioned RE oxides can be reduced, which is preferable, thereby reducing costs. Among them, aluminum oxide and yttria-stabilized zirconia improve the methanation catalytic activity at low temperatures of 300°C or less.

[0016] Hereinafter, each component of the CO2 methanation catalyst 100 of the present invention will be described. In the methanation catalyst 100, nickel metal functions as a catalyst that promotes the above-mentioned reaction formula. Note that the methanation catalyst 100 may contain nickel metal as nickel oxide, and in that case, prior to methanation, a reduction treatment is carried out to reduce the nickel oxide to nickel metal.

[0017] In the methanation catalyst 100, the RE oxide functions as a promoter. Among the above-mentioned RE elements, the oxide of yttrium (Y2O3) or the oxide of ytterbium (Yb2O3) is preferable. These oxides, together with nickel metal, improve the methanation catalytic activity at low temperatures of 300°C or less.

[0018] In the methanation catalyst 100, the carbon is preferably amorphous carbon, and functions as a carrier for the above-mentioned nickel metal or nickel oxide, RE oxide, and further oxide, as well as a forming agent for the porous structure. Therefore, the methanation catalyst 100 can minimize the amount of metal or metal oxide, thereby reducing costs. Since the amount of metal or metal oxide is reduced, the metal or metal oxide does not aggregate even during the methanation reaction, and deterioration of the methanation catalytic activity can be suppressed.

[0019] In the methanation catalyst 100, the above-mentioned nickel oxide or nickel metal, the oxide of RE, carbon, and further oxide constitute a porous material 110 (FIG. 1). Therefore, the reactant molecules (CO2, H2) easily diffuse into the inside of the porous material through the pores, making it easier for the methanation reaction to occur, and high methanation catalytic activity can be expected.

[0020] The porous material 110 preferably has micropores 120 with a pore diameter of less than 2 nm, mesopores 130 with a pore diameter of 2 nm to 50 nm, and macropores 140 with a pore diameter of more than 50 nm. Since the porous material 110 has a plurality of pores with different pore diameters, the diffusion of reaction molecules is further promoted, and the methanation catalytic activity can be improved. If the nitrogen adsorption / desorption isotherm of the porous material 110 corresponds to IUPAC types I and IV, it can be determined that the porous material 110 has micropores 120 and mesopores 130. In addition, it can be determined that the porous material 110 has macropores 140 from an electron microscope image.

[0021] The BET specific surface area of ​​the porous material 110 is preferably 10 m 2 / g or more 300m 2 / g or less. If the specific surface area is within this range, the methanation catalytic activity can be improved. More preferably, the specific surface area is 60 m 2 / g or more 300m 2 / g or less. If the specific surface area is within this range, the methanation catalytic activity is further improved. More preferably, the specific surface area is 150 m 2 / g or more 300m 2 / g or less. If the amount is within this range, the methanation catalytic activity at low temperatures of 300°C or less is improved.

[0022] The micropore surface area of ​​the porous material 110, as measured by the t-plot method, is preferably greater than 2 m 2 / g or more 240m 2 / g or less. If the surface area is within this range, the methanation catalytic activity can be improved. The micropore surface area is more preferably 25 m 2 / g or more 240m 2 / g or less. This range further improves the methanation catalytic activity. The micropore surface area is more preferably 100 m 2 / g or more 300m 2 / g or less. If the amount is within this range, the methanation catalytic activity at low temperatures of 300°C or less is improved.

[0023] The proportion of micropores 120 in the porous material 110 (i.e., the percentage of micropore surface area / BET specific surface area) is preferably in the range of 10% or more and 85% or less. Within this range, methanation catalytic activity is improved. The proportion of micropores more preferably is in the range of 40% or more and 85% or less. Within this range, methanation catalytic activity is further improved. The proportion of micropores even more preferably is in the range of 60% or more and 85% or less. Within this range, methanation catalytic activity is improved at low temperatures of 300°C or less.

[0024] The average pore size of the porous material 110 measured by the BJH method falls within the range of 5 nm to 16 nm, inclusive. If the average pore size falls within this range, the methanation catalytic activity is improved.

[0025] The porous material 110 may satisfy the specific surface area by the BET method, the micropore surface area by the t-plot method, the micropore ratio, and the average pore diameter by the BJH method, either alone or in any combination.

[0026] The porous material 110 is composed of nickel oxide or nickel metal, an oxide of RE, carbon, and, if necessary, further oxides. When the entire porous material 110 is taken as 100% by mass, the porous material 110 is preferably composed of: Contains nickel oxide or nickel metal in an amount of 5% by mass or more and 60% by mass or less in terms of nickel metal, Contains RE oxide in the range of 15 mass% to 85 mass%; Contains carbon in the range of greater than 0 mass% and less than 70 mass%, The further oxide is contained in the range of 0 mass % or more and 55 mass % or less. Within this range, the above-mentioned porosity is provided and the methanation catalytic activity is further improved.

[0027] The porous material 110 is more preferably Contains nickel oxide or nickel metal in an amount of 7% by mass or more and 55% by mass or less, calculated as nickel metal; Contains RE oxide in the range of 17.5 mass% or more and 75 mass% or less, Contains carbon in the range of 5% by mass to 50% by mass, The further oxide is contained in the range of 0 mass % or more and 52.5 mass % or less. Within this range, the above-mentioned porosity is provided and the methanation catalytic activity is further improved.

[0028] The porous material 110 is even more preferably Contains nickel oxide or nickel metal in an amount of 10% by mass or more and 50% by mass or less in terms of nickel metal, Contains RE oxide in the range of 20% by mass or more and 70% by mass or less, Contains carbon in the range of 20% by mass or more and 50% by mass or less, The further oxide is contained in the range of 0 mass % to 35 mass % inclusive, which provides the above-mentioned porosity and further improves the methanation catalytic activity.

[0029] In particular, when containing a further oxide, the porous material 110 preferably comprises Contains nickel oxide or nickel metal in an amount of 10% by mass or more and 50% by mass or less in terms of nickel metal, Contains RE oxide in the range of 20% by mass or more and 55% by mass or less, Contains carbon in the range of 20% by mass or more and 50% by mass or less, The further oxide is contained in an amount of from 15% by mass to 35% by mass, which provides the above-mentioned porosity and further improves the methanation catalytic activity.

[0030] Next, a method for producing the methanation catalyst 100 of the present invention will be described. FIG. 2 is a flow chart showing the process for producing a carbon dioxide methanation catalyst according to the present invention.

[0031] The methanation catalyst 100 of the present invention is produced by the following steps S210 to S240. Step S210: A mixture of a nickel salt and an oxide of RE (wherein RE is at least one element selected from the group consisting of yttrium (Y), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu)) and, if necessary, at least one further oxide selected from the group consisting of aluminum oxide, yttria-stabilized zirconia (YSZ), zirconium oxide, magnesium oxide, calcium oxide, and silicon oxide is prepared. Step S220: The mixture is fired in an oxidizing atmosphere. Step S230: The mixture after baking is mixed with at least one resin selected from the group consisting of a phenol resin, a furan resin, and a divinylbenzene resin to prepare a resin mixture. Step S240: The resin mixture is carbonized.

[0032] Each step will be described in detail. In step S210, the nickel salt may be nickel nitrate, sulfate, chlorate, bromate, iodate, perbromate, metaperiodate, thiocyanate, etc., among which, from the viewpoint of reaction efficiency, nickel nitrate, sulfate, chlorate, and hydrates thereof are preferred. The RE oxide and further oxide are not particularly limited, but may be particles having a particle size in the range of 100 nm to 5000 nm. This allows the raw materials to be mixed uniformly.

[0033] In step S210, the nickel salt, oxides of RE, and, if necessary, further oxides are mixed to satisfy the composition of the methanation catalyst 100 of the present invention, where again, the nickel salt is mixed in terms of nickel metal in the nickel salt.

[0034] In step S210, the mixture may be prepared by adding the oxide of RE, and optionally further oxide, to the nickel salt aqueous solution, stirring, and drying. Such drying may be performed, for example, in the atmosphere at a temperature range of 85° C. to 110° C. for 5 hours to 24 hours.

[0035] In step S220, the mixture from step S210 is fired in an oxidizing atmosphere, and the nickel salt becomes nickel oxide. The firing conditions are not particularly limited as long as the nickel salt becomes nickel oxide, but may be, for example, in air at a temperature range of 400°C to 600°C for 1 hour to 6 hours. Within this range, the nickel salt does not react with the oxide of RE or further oxide, and nickel oxide is obtained. As a result, the resulting nickel oxide becomes particles having a particle size in the range of 1 nm to 500 nm.

[0036] In step S230, the phenol resin, furan resin, and divinylbenzene resin are all carbon sources that become amorphous carbon when calcined. Here, the carbon sources are weighed so that the carbon content after calcination satisfies the composition of the methanation catalyst 100 of the present invention, together with step S210. A resin mixture obtained by mixing these carbon sources with the nickel oxide obtained in step S220, the oxide of RE, and, if necessary, a mixture of further oxides may be formed into a pellet shape.

[0037] In step S240, the carbonization is not particularly limited, but for example, the carbon source may be calcined in an inert gas atmosphere, such as nitrogen or a rare gas such as argon, at a temperature range of 500°C to 1100°C for 30 minutes to 12 hours. Under such conditions, the carbon source becomes porous amorphous carbon. More preferably, the carbonization is calcined in an inert gas atmosphere, at a temperature range of 600°C to 800°C for 1 hour to 3 hours.

[0038] In carbonization, in order to suppress internal cracks, it is advisable to control the heating rate and cooling rate. Preferably, the heating rate is 1°C / min to 5°C / min, more preferably 1.5°C / min to 2.5°C / min, up to 300°C, and the heating rate is 1°C / min to 5°C / min, more preferably 0.5°C / min to 1.5°C / min, up to the holding temperature from above 300°C. In addition, the temperature is reduced from the holding temperature to room temperature at a rate of 1°C / min to 3°C / min, more preferably 1.5°C / min to 2.5°C / min.

[0039] In this way, a methanation catalyst 100 of the invention (FIG. 1) is obtained, which consists of a porous material containing nickel oxide or nickel metal, oxides of RE, carbon and, optionally, further oxides.

[0040] Another method for producing the methanation catalyst 100 of the present invention will now be described. FIG. 3 is another flow chart showing the process for producing a carbon dioxide methanation catalyst according to the present invention.

[0041] The methanation catalyst 100 of the present invention is produced by the following steps S310 to S340. Step S310: Prepare a resin mixture of an oxide of RE (wherein RE is at least one element selected from the group consisting of yttrium (Y), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu)), at least one resin selected from the group consisting of a phenolic resin, a furan resin, and a divinylbenzene resin, and, if necessary, at least one further oxide selected from the group consisting of aluminum oxide, yttria-stabilized zirconia (YSZ), zirconium oxide, magnesium oxide, calcium oxide, and silicon oxide. Step S320: Carbonize the resin mixture. Step S330: The oxide-containing porous carbon body obtained by carbonization is impregnated with an aqueous solution of a nickel salt. Step S340: The oxide-containing porous carbon body impregnated with the nickel salt is fired in an oxidizing atmosphere.

[0042] The manufacturing method shown in Figure 3 differs from that shown in Figure 2 in that carbonization is carried out first and then oxidation of the nickel salt. Each step will be described in detail.

[0043] In step S310, the oxide of RE and the further oxide may be the same as in step S210 (FIG. 2), and the resin mixture may be molded into pellets in the same manner as in step S230.

[0044] In step S320, a carbon porous body containing the oxides of RE and, if necessary, further oxides (oxide-containing carbon porous body) is obtained, where the carbonization may be the same as in step S240.

[0045] In step S330, the oxide-containing porous carbon body is impregnated with an aqueous solution of a nickel salt. The nickel salt may be the nickel salt described in detail in step S210 (FIG. 2). This causes the nickel salt to adhere to the pores of the carbon porous body. After the impregnation, the oxide-containing porous carbon body may be dried in the air to remove the solvent. Such drying may be, for example, heating in the air at a temperature range of 85° C. to 110° C. for 5 hours to 24 hours.

[0046] In step S340, the baking may be similar to step S210 (FIG. 2). In this way, a methanation catalyst 100 of the invention (FIG. 1) is obtained, which consists of a porous material containing nickel oxide or nickel metal, oxides of RE, carbon and, optionally, further oxides.

[0047] (Embodiment 2) In the second embodiment, a methane production method and a methane production apparatus using a carbon dioxide methanation catalyst according to the present invention will be described.

[0048] FIG. 4 is a flow chart showing a process for producing methane according to the present invention.

[0049] Methane is produced by the following steps S410 to S430. Step S410: The methanation catalyst 100 of the present invention (FIG. 1) is subjected to a reduction treatment under a reducing atmosphere. Step S420: The reduced methanation catalyst is heated. Step S430: Carbon dioxide and hydrogen are introduced into the reduced methanation catalyst.

[0050] Methane can be produced from carbon dioxide and hydrogen by using the methanation catalyst 100 of the present invention. Each step will be described in detail. In step S410, the methanation catalyst 100 of the present invention is reduced and activated. When the methanation catalyst 100 is reduced, nickel oxide in the methanation catalyst 100 is reduced to nickel metal, and the methanation catalytic activity can be improved.

[0051] In step S410, the reduction treatment may be, for example, a heat treatment in the temperature range of 350° C. to 700° C. for 30 minutes to 5 hours by introducing a reducing agent such as hydrogen, carbon monoxide, or methanol. The reducing agent is preferably hydrogen for ease of handling. The methanation catalyst 100 of the present invention does not lose its specific surface area even when subjected to a reduction treatment at a relatively high temperature (for example, 500° C. to 700° C.). Therefore, the amount of unreduced nickel oxide can be reduced as much as possible, thereby improving the methanation catalytic activity.

[0052] In step S420, a temperature of 600° C. or less can be applied for heating, but since the methanation catalyst 100 of the present invention has excellent methanation catalytic activity even in a low temperature range of 300° C. or less, a temperature range of 200° C. to 300° C. can be used.

[0053] In step S420, the pressure may be controlled. Increasing the pressure tends to increase the methane yield. For example, the pressure may be in the range of 0.1 MPa to 10 MPa, preferably 0.5 MPa to 8 MPa, more preferably 1 MPa to 5 MPa. Those skilled in the art can adjust the heating temperature and the reaction temperature as appropriate.

[0054] In step S430, carbon dioxide (CO2) and hydrogen (H2) are introduced into the reduced methanation catalyst and reacted in the gas phase to produce methane (CH4) according to the above-mentioned reaction formula. The molar ratio of carbon dioxide to hydrogen may be, for example, 1:2 to 8, preferably 1:3 to 6, and more preferably 1:4. This can promote the methanation reaction. The space velocity of carbon dioxide and hydrogen is not particularly limited, but is illustratively 1000 mL / g-cat·hr or more and 100000 mL / g-cat·hr or less, preferably 2000 mL / g-cat·hr or more and 20000 mL / g-cat·hr or less.

[0055] FIG. 5 is a schematic diagram showing a methane production apparatus according to the present invention.

[0056] As an example of a methane production apparatus that can be used in the above-mentioned methane production method, there is a fixed-bed flow-type methane production apparatus 500. The methane production apparatus 500 produces methane (CH4) by causing a methanation reaction between carbon dioxide (CO2) and hydrogen (H2) in a reaction vessel 510. The reaction vessel 510 contains the methanation catalyst 100 of the present invention.

[0057] The methane production apparatus 500 may be equipped with flow meters (not shown) for adjusting the flow rates of carbon dioxide and hydrogen supplied to the reaction vessel 510. The reaction vessel 510 may be equipped with a heating device (not shown) for heating the contained methanation catalyst 100, or a flow path (not shown) through which a heat medium such as oil passes. A condenser (not shown) for removing water produced together with methane may be provided downstream of the reaction vessel 510.

[0058] The present invention will now be described in detail with reference to specific examples, but it should be noted that the present invention is not limited to these examples. EXAMPLES

[0059] [Raw materials, etc.] The raw powders used in the synthesis were nickel nitrate hexahydrate (Ni(NO3)2·6H2O, special grade, Fujifilm Wako Pure Chemical Industries Co., Ltd.), titanium oxide (TiO2, Sakai Chemical Industry Co., Ltd., 15 nm), yttria-stabilized zirconia (YSZ, Y2O3 (3 mol%)-ZrO2 (97 mol%), Tosoh Corporation, 40 nm), aluminum oxide (Al2O3, 260 nm), yttrium oxide (Y2O3, Kojundo Chemical Laboratory Co., Ltd., 1000 nm), ytterbium oxide (Yb2O3, Kojundo Chemical Laboratory Co., Ltd., 1200 nm), lanthanum oxide (La2O3, Kojundo Chemical Laboratory Co., Ltd., 2000 nm), cerium oxide (CeO2, Daiichi Kigenso Kagaku Kogyo Co., Ltd., 4700 nm (D50)), and phenolic resin (PR-311, Sumitomo Bakelite Co., Ltd.).

[0060] In addition, a Ru-supported TiO2 catalyst (Ru / TiO2) was used for comparison as a commercial carbon dioxide methanation catalyst.

[0061] [Example 1] In Example 1, a carbon dioxide methanation catalyst was produced using the production process shown in FIG.

[0062] A mixture of nickel nitrate hexahydrate (Ni(NO3)2·6H2O) as a nickel salt, Y2O3 as an oxide of RE, and YSZ as a further oxide was prepared (step S210 in FIG. 2). Specifically, as shown in Table 1, nickel nitrate solution (concentration 50 wt%) was prepared by dissolving distilled water in Ni(NO3)2·6H2O so that Ni was contained at 10 wt% based on the sample weight of the designed composition. Then, Y2O3 and YSZ were added to this aqueous solution and left to stand for 1 hour. After that, this slurry was dried at 120°C in the air while stirring with a stirrer to obtain a mixture. The obtained mixture was further thoroughly dried at 100°C for more than 12 hours to remove remaining moisture.

[0063] Next, the mixture was fired in an oxidizing atmosphere (step S220 in FIG. 2). The dried mixture was pulverized and then fired in air at 500° C. for 2 hours. The resulting mixture was subjected to powder X-ray diffraction (XRD) measurement. The results are shown in FIG. 6.

[0064] Next, the baked mixture was mixed with phenolic resin to prepare a resin mixture (step S230 in FIG. 2). Phenolic resin was added to the mixture, mixed uniformly, and molded. A hydraulic pump and tablet press were used for molding, and the pellet-type resin mixture was made into a pellet with a diameter of 15 mm and a thickness of 1 to 5 mm at a tableting pressure of 5 to 30 MPa.

[0065] Next, the pellet-type resin mixture was carbonized (step S240 in FIG. 2). In detail, in a nitrogen atmosphere, the temperature was increased to 300° C. at a rate of 2° C. / min, held for 1 hour, increased to 700° C. at a rate of 1° C. / min, held for 2 hours, and then cooled to room temperature at a rate of 2° C. / min. The sample thus obtained is referred to as the sample of Example 1.

[0066] The appearance of the sample of Example 1 was observed, and powder X-ray diffraction measurements were performed. The microstructure of the sample of Example 1 was observed using a scanning electron microscope (SEM, JEL-7000F, JEOL). The specific surface area and pore distribution of the sample of Example 1 were measured using a nitrogen gas device (specific surface area / pore distribution measurement device, ASAP2020, manufactured by Micromeritics). The methanation catalyst properties of the sample of Example 1 were evaluated using a fixed-bed flow-type catalyst evaluation device. These results are shown in Figures 7 and 8 and Table 2.

[0067] [Example 2 to Example 16] In Examples 2 to 16, similarly to Example 1, the raw materials were appropriately mixed in the ratios shown in Table 1 so as to obtain the design composition shown in Table 1, and carbonized under the carbonization conditions shown in Table 1. The samples thus obtained are referred to as the samples of Examples 2 to 16, respectively. For the samples of Examples 2 to 16, similarly to Example 1, XRD, SEM observation, specific surface area, pore distribution, and methanation catalyst property evaluation were performed. For the sample of Example 3, the contents of Ni, Y, and Zr were analyzed by inductively coupled plasma optical emission spectrometry (ICP-OES) (Agilent5800, Agilent Technologies), and the content of O was analyzed by inert gas fusion-infrared absorption method (instrument type TC-436AR, LECO). Furthermore, the content of C was calculated from these results. These results are shown in Figures 9 to 15 and Tables 2 and 3.

[0068] [Table 1]

[0069] [Example 17] In Example 17, a carbon dioxide methanation catalyst was produced using the production process shown in FIG.

[0070] In Example 17, to obtain the same design composition as Example 1, 10 wt% Ni-70 wt% Y2O3-20 wt% C, Y2O3 and phenol resin were used as raw materials at 70 wt% and 35.7 wt%, respectively.

[0071] A resin mixture of Y2O3 as an oxide of RE and phenolic resin was prepared (step S310 in FIG. 3). Specifically, phenolic resin was added to Y2O3 and mixed uniformly, and a hydraulic pump and a tablet press were used to produce a pellet-type resin mixture with a diameter of 15 mm and a thickness of 1 to 5 mm at a tableting pressure of 5 to 30 MPa.

[0072] Next, the pellet-type resin mixture was carbonized (step S320 in FIG. 3). In detail, the mixture was heated to 300°C at a heating rate of 3°C / min under a nitrogen atmosphere, held for 1 hour, heated to 700°C at a heating rate of 3°C / min, held for 2 hours, and then cooled to room temperature at a cooling rate of 3°C / min. This produced a Y2O3-containing porous carbon body.

[0073] The Y2O3-containing porous carbon body was impregnated with a nickel nitrate solution (concentration: 50 wt%) (step S330 in FIG. 3). Next, the Y2O3-containing porous carbon body impregnated with the nickel salt was fired in an oxidizing atmosphere (step S340 in FIG. 3). The nickel salt-impregnated Y2O3-containing porous carbon body was dried at 90°C for 12 hours, and then fired in air at 500°C for 4 hours. The sample thus obtained is referred to as the sample of Example 17.

[0074] For the sample of Example 17, XRD, SEM observation, specific surface area, pore distribution, and methanation catalyst property evaluation were performed in the same manner as in Example 1. These results are shown in Tables 2 and 3.

[0075] The above results will be summarized.

[0076] FIG. 6 is a diagram showing an XRD pattern of the mixture obtained in step S220 of FIG. According to Fig. 6, it was found that a mixture containing NiO, Y2O3 and ZrO2 phases was obtained by step S220 of Fig. 2. This indicates that the nickel salt is oxidized to nickel oxide by the firing in step S220 of Fig. 2 and step S340 of Fig. 3.

[0077] FIG. 7 is a diagram showing the appearance of the sample of Example 1.

[0078] As shown in Fig. 7, the sample of Example 1 maintained its shape without crumbling even after carbonization. Although not shown, the samples of Examples 2 to 15 and 17 all had similar forms. On the other hand, the sample of Example 16, which did not contain carbon, was easily crumbled and brittle after firing.

[0079] FIG. 8 shows the XRD pattern of the sample of Example 1.

[0080] FIG. 8(A) is the XRD pattern shown in FIG. 6, and FIG. 8(B) is the XRD pattern of the sample of Example 1. According to FIG. 8(B), the XRD pattern is the same as FIG. 8(A), and it was confirmed that the NiO phase, the Y2O3 phase, and the ZrO2 phase exist without reacting even after the carbonization treatment. Note that the carbon generated from the phenolic resin by carbonization is amorphous and cannot be detected by X-ray diffraction, so a composition analysis was performed. Although not shown, it was confirmed that the samples of Examples 2 to 6, Examples 11 to 14, and Example 17 also contain the NiO phase, the Y2O3 phase, and / or the Yb2O3 phase, and the ZrO2 phase or the Al2O3 phase.

[0081] 4 shows the results of composition analysis of the sample of Example 3. Ni:9.48 (mass%) Y:27.4 (mass%) Zr:22.4 (mass%) O:20.0 (mass%) C: 20.72 (mass%) (estimated as C%=100-Ni%-Y%-Zr%-O%) From these, when the entire sample of Example 3 was taken as 100 mass%, Y and Zr were converted to Y2O3 and YSZ, Ni: 9.48% by mass Y2O3: 34.8% by mass YSZ: 31.97% by mass C: 23.75% by mass (estimated as C% = 100-Ni%-Y2O3%-YSZ%) This indicates that the method of the present invention can produce a sample that satisfies the designed composition.

[0082] FIG. 9 is a diagram showing an SEM image of the sample of Example 3. FIG. 10 is a diagram showing an SEM image of the sample of Example 11. FIG. 11 is a diagram showing an SEM image of the sample of Example 12. FIG. 12 is a diagram showing an SEM image of the sample of Example 13. FIG. 13 is a diagram showing an SEM image of the sample of Example 15.

[0083] 9 to 13 show SEM images of the samples before hydrogen reduction treatment observed at various magnifications. According to Fig. 9(A) to Fig. 12(A), it was found that the samples of Example 3 and Examples 11 to 13 were porous materials having macropores with a diameter of more than 50 nm. Moreover, according to Fig. 9(C) and Fig. 10(B) to Fig. 12(B), the samples of Example 3 and Examples 11 to 13 had a microstructure in which metal oxide particles with a diameter of several tens of nm and carbon were uniformly mixed. Although not shown, the samples of Example 1, Example 2, Examples 4 to 6, Example 11, Example 14, and Example 17 also showed similar SEM images.

[0084] On the other hand, according to FIG. 13, the sample of Example 15 was also a porous material having macropores, but metal oxide particles (nickel oxide) having a diameter of several hundred nm were present in the carbon substrate.

[0085] FIG. 14 is a graph showing the nitrogen gas adsorption / desorption isotherm of the sample of Example 2. FIG. 15 shows the pore distribution of the sample of Example 2.

[0086] The results of the nitrogen adsorption test of the sample before the hydrogen reduction treatment are shown in Figures 14 and 15. Figure 15 shows the mesopore distribution calculated by the BJH (Barrett-Joyner-Halenda) method from the isotherm in Figure 14.

[0087] According to Fig. 14, the sample of Example 2 showed an isotherm showing hysteresis, and the isotherm was classified as a mixed type of IUPAC type I and type IV. This and SEM observation showed that the sample of Example 2 was a porous material having micropores with a diameter of 2 nm or less, mesopores with a diameter of more than 2 nm and less than 50 nm, and macropores with a diameter of 50 nm or more. Although not shown, the samples of Example 1, Example 3 to Example 6, Example 11 to Example 14, and Example 17 also showed similar nitrogen gas adsorption and desorption isotherms.

[0088] Table 2 shows the specific surface area of ​​the sample of Example 2 calculated by the BET (Brunauer-Emmett-Teller) method and the micropore surface area calculated by the t-plot method.

[0089] 15, it was found that mesopores with pore diameters of 4 nm and 18 nm existed in the sample of Example 2. The average pore diameter measured by the BJH method was 6.65 nm.

[0090] [Table 2]

[0091] The ratio of micropores calculated from the BET specific surface area and the t-plot micropore surface area (t-plot micropore surface area / BET specific surface area × 100) and the t-plot external surface area are also shown in Table 2. The sum of the t-plot micropore area and the t-plot external surface area is approximately equal to the BET specific surface area.

[0092] According to Table 2, the samples of Examples 1 to 6, 11 to 14, and 17 all had a 10 m 2 / g or more 300m 2 / g or less BET specific surface area, 2m 2 / g or more 240m 2 / g and a BJH average pore size in the range of 5 nm to 16 nm.

[0093] [Table 3]

[0094] Table 3 shows the evaluation results of the methanation catalyst properties of the samples of Examples 1 to 17. The samples of Examples 1 to 17 were reduced under the reduction conditions shown in Table 3 before the evaluation of the methanation catalyst properties. By this reduction, the nickel oxide in the samples of Examples 1 to 17 was reduced to nickel metal. For comparison, the evaluation results of a commercial Ru-supported TiO2 catalyst (Ru / TiO2) are also shown.

[0095] The methanation catalyst properties were evaluated as follows. A heatable reaction tube (e.g., reaction vessel 510 in FIG. 5) with an inner diameter of 8 mm in which the samples (0.5 g) of Examples 1 to 17 were placed was designed to be supplied with feed gas (CO2: 6 mL / min, H2: 24 mL / min, N2: 30 mL / min), and an online gas chromatograph (TCD detector, GLScience) for analyzing the generated gas and a dry flowmeter (Defender 530+, manufactured by Mesa Labs) for measuring the gas flow rate were installed downstream of the reaction tube, and the generated gas was analyzed. The methanation catalyst properties were evaluated at reaction temperatures of 240°C and 250°C.

[0096] According to Table 3, the samples of Examples 1 to 6, 11 to 14, and 17 all had a CO2 conversion rate of more than 50% and a CH4 selectivity of nearly 100% at temperatures of 300°C or less, indicating that they function as carbon dioxide (CO2) methanation catalysts.

[0097] Next, focusing on the results of Examples 2, 15, and 16, it was shown that a porous material containing nickel oxide / nickel metal, an oxide of RE (wherein RE is at least one element selected from the group consisting of yttrium (Y), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu)) as active ingredients, and carbon functions as an excellent carbon dioxide methanation catalyst at low temperatures of 300° C. or less.

[0098] Next, focusing on the results of Examples 1, 2, 4, and 5, it was shown that a porous material further containing at least one oxide selected from the group consisting of aluminum oxide, yttria-stabilized zirconia (YSZ), zirconium oxide, magnesium oxide, calcium oxide, and silicon oxide as an active ingredient functions as an excellent carbon dioxide methanation catalyst at low temperatures of 300° C. or less. This allows a part of the oxide of RE to be replaced with the above-mentioned oxide, which is advantageous in reducing the cost of the catalyst.

[0099] Next, when attention is paid to the results of Examples 3 and 6 to 9, it is shown that the oxide of RE is preferably an oxide of yttrium (Y2O3) and an oxide of ytterbium (Yb2O3).

[0100] Next, focusing on the results of Examples 2 and 11 to 12, it was shown that when the amount of carbon was the same, the methanation catalytic activity at low temperatures of 300° C. or less improved as the amount of nickel oxide / nickel metal increased.

[0101] Next, looking at the results of Examples 11 and 13, it was found that when the amount of nickel oxide was the same, the methanation catalytic activity at low temperatures below 300°C did not depend on the carbon content. This is advantageous because it allows the carbon content to be increased and the cost of the catalyst to be reduced.

[0102] Moreover, focusing on the results of Examples 2 and 17, although the pore characteristics of the sample of Example 2 and the sample of Example 17 are different, both of them showed excellent methanation catalytic activity at low temperatures of 300°C or less. This shows that both the production method shown in Figure 2 and the production method shown in Figure 3 are effective for producing the catalyst of the present invention described with reference to Figure 1. In particular, focusing on the reduction conditions of the sample of Example 17, it was shown that the lower the reduction temperature, the more improved the methanation catalytic activity at low temperatures of 300°C or less.

[0103] Focusing on the results of commercial Ru / TiO2, excellent methanation catalytic activity was shown at a reduction temperature of 430° C., but the methanation catalytic activity was significantly decreased at a reduction temperature of 600° C. On the other hand, according to the results of Examples 1 to 6, 11 to 14, and 17, excellent methanation catalytic activity was shown even at a reduction temperature of 600° C., indicating that the catalyst of the present invention has excellent heat resistance. [Industrial Applicability]

[0104] The carbon dioxide methanation catalyst of the present invention does not use a precious metal such as Ru and has excellent methanation catalytic activity at low temperatures of 300° C. or less, and therefore will further contribute to the realization of carbon neutrality. [Explanation of symbols]

[0105] 100 Methanation catalyst 110 Porous materials 120 micro holes 130 Mesopores 140 Macropores 500 Methane production equipment 510 Reaction vessel

Claims

1. Nickel oxide or nickel metal, An oxide of RE (where RE is at least one element selected from the group consisting of yttrium (Y), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu)), Carbon and, If necessary, a further oxide selected from the group consisting of aluminum oxide, yttria-stabilized zirconia (YSZ), zirconium oxide, magnesium oxide, calcium oxide, and silicon oxide, and A porous material containing carbon dioxide (CO2) ２ A methanation catalyst.

2. The methanation catalyst according to claim 1, wherein the carbon is amorphous carbon.

3. When the entire porous material is considered to be 100% by mass, The aforementioned nickel oxide or nickel metal is contained in an amount of 5% by mass or more and 60% by mass or less in terms of nickel metal. The above RE oxide is contained in an amount of 15% by mass or more and 85% by mass or less. The carbon is contained in a range greater than 0% by mass and less than 70% by mass. The methanation catalyst according to claim 1, further containing the aforementioned additional oxide in an amount of 0% by mass or more and 55% by mass or less.

4. The aforementioned nickel oxide or nickel metal is contained in an amount of 7% by mass or more and 55% by mass or less in terms of nickel metal. The aforementioned RE oxide is contained in an amount of 17.5% by mass or more and 75% by mass or less. The carbon is contained in a range of 5% by mass or more and 50% by mass or less. The methanation catalyst according to claim 3, further containing the aforementioned further oxide in an amount of 0% by mass or more and 52.5% by mass or less.

5. The aforementioned nickel oxide or nickel metal is contained in an amount of 10% by mass or more and 50% by mass or less in terms of nickel metal. The above RE oxide is contained in an amount of 20% by mass or more and 70% by mass or less. The carbon is contained in a range of 20% by mass or more and 50% by mass or less. The methanation catalyst according to claim 4, further containing the aforementioned additional oxide in an amount of 0% by mass or more and 35% by mass or less.

6. The methanation catalyst according to claim 1, wherein the RE is yttrium and / or ytterbium.

7. The methanation catalyst according to claim 1, wherein the porous material has micropores, mesopores, and macropores.

8. The specific surface area of ​​the porous material measured by the BET method is 10 m². ２ / g or more 300m ２ The methanation catalyst according to claim 1, satisfying the range of less than or equal to / g.

9. The specific surface area of ​​the porous material measured by the BET method is 60 m². ２ / g or more 300m ２ The methanation catalyst according to claim 8, satisfying the range of less than or equal to / g.

10. The micropore surface area of ​​the porous material measured by the t-plot method is 2 m ２ / g or more 240m ２ The methanation catalyst according to claim 1, satisfying the range of less than or equal to / g.

11. The micropore surface area of the porous material by the t-plot method is 25 m ２ / g or more and 240 m ２ / g or less, and the methanation catalyst according to claim 10.

12. The methanation catalyst according to claim 1, wherein the proportion of micropores in the porous material is in the range of 10% to 85%.

13. The methanation catalyst according to claim 12, wherein the proportion of micropores in the porous material is in the range of 40% to 85%.

14. The methanation catalyst according to claim 1, wherein the porous material has mesopores that satisfy the range of 5 nm to 16 nm in average pore diameter determined by the BJH method.

15. The method involves preparing a mixture of a nickel salt, an oxide of RE (where RE is at least one element selected from the group consisting of yttrium (Y), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu)), and optionally a further oxide selected from the group consisting of aluminum oxide, yttria-stabilized zirconia (YSZ), zirconium oxide, magnesium oxide, calcium oxide, and silicon oxide. The mixture is calcined in an oxidizing atmosphere, The process involves mixing the aforementioned calcined mixture with at least one resin selected from the group consisting of phenolic resin, furan resin, and divinylbenzene resin to prepare a resin mixture. Carbonizing the aforementioned resin mixture A method for producing a carbon dioxide methane catalyst according to any one of claims 1 to 14, comprising the above.

16. The present invention provides a resin mixture comprising an oxide of RE (where RE is at least one element selected from the group consisting of yttrium (Y), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu)), a resin selected from the group consisting of phenolic resins, furan resins, and divinylbenzene resins, and optionally a further oxide selected from the group consisting of aluminum oxide, yttria-stabilized zirconia (YSZ), zirconium oxide, magnesium oxide, calcium oxide, and silicon oxide, The aforementioned resin mixture is carbonized, The oxide-containing carbon porous material obtained by carbonization is impregnated with an aqueous solution of nickel salt, The oxide-containing carbon porous body impregnated with the aforementioned nickel salt is fired in an oxidizing atmosphere. A method for producing a carbon dioxide methane catalyst according to any one of claims 1 to 14, comprising the above.

17. The method according to claim 15, wherein the nickel salt is a salt selected from the group consisting of nickel nitrates, sulfates, chlorates, bromates, iodates, perbromates, metaperiodates, and thiocyansates.

18. The method according to claim 16, wherein the nickel salt is a salt selected from the group consisting of nickel nitrates, sulfates, chlorates, bromates, iodates, perbromates, metaperiodates, and thiocyansates.

19. A methane production apparatus comprising a reaction vessel for containing a catalyst for producing methane from carbon dioxide and hydrogen, wherein the catalyst is a carbon dioxide methane catalyst according to any one of claims 1 to 14.

20. A method for producing methane, The carbon dioxide methane catalyst described in any one of claims 1 to 14 is subjected to reduction treatment in a reducing atmosphere, Heating the reduced methane catalyst, Introducing carbon dioxide and hydrogen into the reduced methane catalyst. A method that includes.

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