Catalyst for methanation and method for producing methane

Abstract

To provide a catalyst that can progress methanation even at the temperature of 500°C or less, under the normal pressure condition, and at a low hydrogen concentration, and a method for producing methane.SOLUTION: A catalyst for methanation includes first grains, second grains, and third grains. The first grains consist of metal containing at least one kind selected from the group consisting of nickel, cobalt, and ruthenium. The second grains contain apatite type oxide shown by general formula (1). R10Si6-xMxO27 (1) (In general formula (1), R is one or more kinds selected from lanthanoid elements, M is one or more kinds selected from the group consisting of Co, Fe, Ni, and x denotes 0≤x≤1.5) The third grains is made of a ceramic material. The first grains and the second grains are carried on the third grains.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a catalyst for methanation and a method for producing methane. [Background technology]

[0002] Carbon Dioxide (CO 2 ) and hydrogen (H 2 The reaction that produces methane using ethanol and ethanol as raw materials is known as the methanation reaction (sometimes simply called methanation). The methanation reaction is represented by the following reaction formula: CO 2 +4H 2 →CH 4 +2H 2 O Catalysts for efficiently promoting methanation have been studied. For example, Patent Document 1 discloses a catalyst for methanation that includes a carrier and a catalytic component. In the catalyst disclosed in Patent Document 1, the carrier includes one or more elements selected from the group consisting of elements such as cerium, lanthanum, praseodymium, and neodymium, and the catalytic component includes nickel supported on the carrier.

[0003] Patent Document 2 discloses a carrier and a catalytic metal supported on the carrier as a catalyst used for methanation. The carrier of the catalyst disclosed in Patent Document 2 contains a metal oxide containing at least one metal element selected from cerium, zirconium, yttrium, aluminum, silicon, and magnesium. The catalytic metal contains at least one metal selected from nickel, ruthenium, rhodium, potassium, calcium, sodium, and iridium. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2019-155227 A [Patent Document 2] JP 2020-33280 A Summary of the Invention [Problem to be solved by the invention]

[0005] The methanation reaction is an exothermic reaction, but carbon monoxide is generated by the reverse water gas shift reaction from about 500°C. Therefore, in consideration of reaction efficiency and safety, it is preferable to carry out methanation at 500°C or less and at normal pressure. In addition, hydrogen gas, which is the raw material, is flammable and has an explosion range in air (the explosion concentration range of hydrogen in air is 4.0 to 75%). From the viewpoint of safety, it is preferable to carry out the methanation reaction at a hydrogen concentration below the explosion limit. Therefore, one of the objects of the present disclosure is to provide a catalyst and a method for producing methane that can proceed with methanation even at a low hydrogen concentration under normal pressure conditions at a temperature of 500°C or less. [Means for solving the problem]

[0006] The catalyst for methanation according to the present disclosure includes first particles, second particles, and third particles, and the first particles are made of at least one metal selected from the group consisting of nickel, cobalt, and ruthenium. The second particles contain an apatite-type oxide represented by general formula (1). R 10 S 6-x M x O 27 (1) (In the general formula (1), R is one or more elements selected from the lanthanoid elements, M is one or more elements selected from the group consisting of Co, Fe, and Ni, and x is 0≦x≦1.5.) The third particles are made of a ceramic material, and the first particles and the second particles are supported on the third particles. Effect of the Invention

[0007] The above catalyst allows methanation to proceed even at a temperature of 500° C. or less, under normal pressure conditions, and with a low hydrogen concentration. [Brief description of the drawings]

[0008] [Figure 1] 1 is a graph showing the relationship between reaction temperature and CO2 conversion rate in methanation using the catalysts of Example 1 and Example 2. [Diagram 2] 1 is a graph showing the relationship between reaction temperature and methane yield in methanation using the catalysts of Example 1 and Example 2. [Diagram 3] 1 is a graph showing the relationship between reaction temperature and CO2 conversion rate in methanation using the catalysts of Example 2 and Example 3. [Figure 4] 1 is a graph showing the relationship between reaction temperature and methane yield in methanation using the catalysts of Example 2 and Example 3. [Diagram 5] 1 is a graph showing the relationship between reaction temperature and CO2 conversion rate in methanation using the catalysts of Example 1 and Examples 4 to 6. [Figure 6] 1 is a graph showing the relationship between reaction temperature and methane yield in methanation using the catalysts of Example 1 and Examples 4 to 6. [Figure 7] 1 is a graph showing the relationship between reaction temperature and CO2 conversion rate in methanation using the catalysts of Example 1 and Examples 7 to 8. [Figure 8] 1 is a graph showing the relationship between reaction temperature and methane yield in methanation using the catalysts of Example 1 and Examples 7 to 8. [Figure 9] 1 is a graph showing the relationship between reaction temperature and CO2 conversion rate in methanation using the catalysts of Example 1 and Comparative Examples 1 and 2. [Figure 10] 1 is a graph showing the relationship between reaction temperature and methane yield in methanation using the catalysts of Example 1 and Comparative Examples 1 and 2. [Figure 11] 1 is a flow chart illustrating a method for producing methane using a catalyst according to the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] [Outline of the embodiment] First, the catalysts and production methods according to the present disclosure will be listed and described. The catalyst for methanation according to the present disclosure includes first particles, second particles, and third particles, and the first particles are made of at least one metal selected from the group consisting of nickel, cobalt, and ruthenium. The second particles include an apatite-type material represented by general formula (1). R 10 S 6-x M x O 27 (1) (In the general formula (1), R is one or more elements selected from the lanthanoid elements, M is one or more elements selected from the group consisting of Co, Fe, and Ni, and x is 0≦x≦1.5.) The third particles are made of a ceramic material, and the first particles and the second particles are supported on the third particles.

[0010] Methanation is a reaction that converts carbon dioxide into methane using hydrogen. Methanation can reduce carbon dioxide and reuse the methane produced as fuel gas. Expectations for methanation as a technology that can achieve carbon neutrality are growing, and catalysts for methanation and methods of using them are being studied. Patent Document 1 discloses a method of carrying out methanation using a catalyst having a specific composition. In the examples of Patent Document 1, it is described that a raw material gas consisting of 80 mol % hydrogen and 20 mol % carbon dioxide, and a raw material gas consisting of 8 mol % hydrogen, 2 mol % carbon dioxide, and 90 mol % nitrogen were used as the raw material gas.

[0011] Patent Document 2 discloses a method for producing methane by methanation using a specific catalyst. Patent Document 2 discloses a method using a raw material gas containing carbon dioxide, hydrogen, and oxygen. In consideration of the fact that exhaust gases and the like that are used as raw material gases for methanation in practice may contain not only carbon dioxide and hydrogen but also oxygen, the technology of Patent Document 2 proposes a method for efficiently producing methane even in the presence of oxygen. In the examples of Patent Document 2, a mixed gas consisting of 10 volume % carbon dioxide, 10 volume % oxygen, 60 volume % hydrogen, and the balance nitrogen is used as the raw material gas.

[0012] If the concentrations of carbon dioxide and hydrogen contained in the raw gas are low, the methanation reaction is thermodynamically unfavorable. On the other hand, since hydrogen has an explosive range in air, it is desirable that the methanation reaction proceeds even at a low hydrogen concentration, such as below the explosive limit (4% or less). In addition, in order to increase the reaction efficiency, it is possible to carry out methanation under pressure, but from the viewpoint of energy efficiency and safety, it is desirable that methanation proceeds even at normal pressure. According to the catalyst disclosed herein, even when the reaction is carried out at normal pressure using a raw gas with a low hydrogen concentration, a sufficient carbon dioxide conversion rate and methane yield can be obtained. Although it is not limited to a particular theory, it is believed that the catalyst disclosed herein has a configuration in which an apatite-type oxide having an oxide ion conduction path and capable of efficiently storing and releasing oxygen in the lattice, and a catalytic metal (typically Ni) having hydrogen dissociation ability are supported on a ceramic material with a high specific surface area, thereby enhancing the oxidation-reduction ability and exhibiting excellent catalytic activity in methanation.

[0013] In the catalyst for methanation, at least a part of the first particles may be in contact with the second particles. The content of the first particles may be 3 mass% or more and 40 mass% or less with respect to the mass of the catalyst. With these configurations and content ratios, the effects of the present disclosure can be reliably obtained.

[0014] In the catalyst for methanation, the content of the second particles may be 5% by mass or more and 60% by mass or less with respect to the total mass of the second particles and the third particles. When it is in this range, the effect of the present disclosure can be obtained more reliably.

[0015] In the catalyst for methanation, the ceramic material may be one or more selected from the group consisting of alumina, silica, cordierite, and mullite. These ceramic materials are known materials with excellent stability, and can stably obtain a catalyst supporting a catalytically active substance including a catalytic metal and a composite metal oxide.

[0016] The method for producing methane according to the present disclosure includes the steps of preparing a feed gas containing carbon dioxide and hydrogen, and contacting the feed gas with a catalyst for methanation to produce methane from carbon dioxide and hydrogen. According to the production method according to the present disclosure, even when a feed gas with a low hydrogen concentration is used, the conversion rate of carbon dioxide and the methane yield are high, and methane can be suitably obtained.

[0017] In the method, the hydrogen concentration in the source gas may be 1% by volume or more and 8% by volume or less based on the volume of the source gas. When the hydrogen concentration is within this range, the effects of the present disclosure become more pronounced.

[0018] [Specific Example of the Embodiment] The catalyst and the method for producing methane according to the present disclosure will be described in more detail below with reference to specific examples of embodiments.

[0019] (catalyst) The catalyst according to the present disclosure is a catalyst including a first particle, a second particle, and a third particle. The first particle includes a catalytic metal. The second particle includes an apatite-type oxide. The third particle is a ceramic material. In the catalyst according to the present disclosure, the first particle and the second particle are supported by the third particle. At least a part of the first particle is in contact with the surface of the second particle. That is, at least a part of the first particle is supported by the second particle. The second particle is in contact with the surface of the third particle. The first particle includes a particle in contact with the surface of the second particle and the surface of the third particle, and a particle in contact only with the surface of the second particle and supported by the third particle via the second particle.

[0020] The composition of the first particles can be confirmed by, for example, X-ray diffraction (XRD) to confirm that they exist as particles. The morphology of the second and third particles can be confirmed by, for example, a scanning electron microscope (SEM) or a transmission electron microscope (TEM), and the composition of the particles can be confirmed by X-ray diffraction (XRD) or X-ray fluorescence analysis.

[0021] (1st particle) The first particles are made of at least one metal selected from the group consisting of nickel, cobalt, and ruthenium. The metal constituting the first particles may be one type or may contain two or more types. The metal as the first particles is a catalytic metal that has hydrogen dissociation ability and functions as a catalyst for promoting a methanation reaction.

[0022] The first particles preferably contain nickel. The content of nickel in the first particles may be 50% by mass or more, preferably 70% by mass or more, based on the entire first particles, and is preferably substantially made of nickel. "Substantially made of nickel" means that the first particles are composed of nickel, except for unavoidable impurities.

[0023] In the catalyst according to the present disclosure, the content ratio of the first particles, which are catalytic metals, is not limited as long as the effect according to the present disclosure is obtained, but may be 3% by mass to 40% by mass, and preferably 6% by mass to 30% by mass, based on the mass of the catalyst. If the content of the catalytic metal is 3% by mass or more, the catalytic effect of promoting methanation by functioning together with the second particles is obtained. If the content of the catalytic metal is 40% by mass or less, a sufficient catalytic effect is obtained.

[0024] (2nd particle) The second particles contain an apatite-type oxide represented by general formula (1), and preferably consist of an apatite-type oxide represented by general formula (1). R 10 S 6-x M x O 27 (1) (In the general formula (1), R is one or more elements selected from the lanthanoid elements, M is one or more elements selected from the group consisting of Co, Fe, and Ni, and x is 0≦x≦1.5.) It is known that apatite-type rare earth silicates have oxide ion conduction paths in the lattice and can efficiently store and release oxygen. On the other hand, it was not known that such apatite-type oxides are suitable as methanation catalysts. The catalyst according to the present disclosure was discovered by supporting the above-mentioned apatite-type oxide and catalytic metal on a ceramic support, and thereby exhibiting a high methanation catalytic effect.

[0025] In the general formula (1), R is a lanthanoid element, specifically, La (lanthanum), Ce (cerium), Pr (praseodymium), Sm (samarium), Eu (europium), Gd (gadolinium), etc. Among these, it is preferable that R is one or more elements selected from Sm, La, Nd, Eu, and Gd.

[0026] Other metals may be added as part of Si constituting the silicate in the second particle. In the general formula (1), the other metal represented by M is any one of Co, Fe, and Ni, and among them, Co is preferable. x is 0 or more and 1.5 or less, and preferably 0 or more and 1.1 or less. When x=0, it means that no other metal is contained, and the apatite-type oxide constituting the second particle is R. 10 S 6 O 27 It is.

[0027] In the catalyst according to the present disclosure, the content ratio of the second particles, which are composite metal oxides, is not limited as long as it has the effect according to the present disclosure, but may be 5% by mass to 60% by mass, and preferably 8% by mass to 53% by mass, based on the mass of the catalyst. The content ratio of the second particles may be 5% by mass to 60% by mass, and preferably 10% by mass to 60% by mass, based on the total mass of the second particles and the third particles. If the content ratio of the second particles is 5% by mass or more based on the total mass of the second particles and the third particles, the effect of converting carbon dioxide in the raw gas and promoting methanation is obtained. If the content ratio of the second particles is 60% by mass or less, a sufficient catalytic effect is obtained.

[0028] (3rd particle) The third particles constituting the catalyst according to the present disclosure are made of a ceramic material that functions as a carrier. Examples of the ceramic material include alumina (Al 2 O 3 ), silica (SiO 2 ), cordierite (2MgO 2Al 2 O 3 5SiO 2 ) and Mullite (3Al 2 O 3 2SiO 2 The above-mentioned materials are suitable as the ceramic material constituting the third particles.

[0029] Among them, γ-alumina, which is a cubic crystal, can be preferably used. The third particles function as a dispersion medium. When the catalyst contains the third particles, the aggregation of the first particles and the second particles can be suppressed, and the reduction in the surface area of ​​the first particles and the second particles can be suppressed. The average particle size of the third particles is, for example, 5 nm or more, preferably 10 nm or more. The upper limit of the average particle size of the third particles is not particularly limited, but is, for example, less than 1 μm.

[0030] The content ratio of the third particles in the catalyst according to the present disclosure can be appropriately determined depending on the content ratio of the second particles and the first particles.

[0031] (Catalyst Function) The catalyst according to the present disclosure is used as a catalyst for producing methane. The catalyst according to the present disclosure promotes the methanation reaction. The activity of the catalyst is determined by the amount of CO 2 Conversion, CH 4 Yield and CH 4 The selectivity can be used as an index. 2 Conversion rate is the ratio of CO in the feed gas to the total amount of the catalyst at a certain temperature. 2 Concentration of CO in the gas obtained after the reaction 2 The percentage decrease in concentration. 4 The yield is calculated by dividing the CO 2 CH in the gas after the reaction versus concentration 4 The concentration ratio is CH 4 The selectivity is CO 2 CH vs. Conversion 4 It is the percentage of yield.

[0032] The catalyst according to the present disclosure is capable of reacting with CO at a reaction temperature of 250°C to 400°C. 2 The conversion rate may be 21% or more. 4 The selectivity may be 55% or more. Preferably, the CO 2 The conversion rate may be 42% or more. 4The selectivity may be 67% or more. The performance of the catalyst according to the present disclosure is not particularly limited. For example, 2 Conversion rate is 21% or more, CH 4 The selectivity is 55% or more. For example, CO 2 Conversion rate is 42% or more, CH 4 The selectivity is 70% or more. For example, CO 2 Conversion rate is 48% or more, CH 4 The selectivity is 67% or more. For example, CO 2 Conversion rate is 45% or more, CH 4 The selectivity is 60% or more. For example, CO 2 Conversion rate is 45% or more, CH 4 The selectivity is 29% or more. For example, CO 2 Conversion rate is 47% or more, CH 4 The selection rate is 13% or higher.

[0033] The catalyst according to the present disclosure can proceed with methanation even when the carbon dioxide and hydrogen concentrations in the raw gas are low. For example, methanation can proceed even when the hydrogen concentration in the raw gas is 10% or less, typically 4% or less. Hydrogen gas is a flammable gas, and the explosive concentration range of hydrogen in air is 4.0% to 75%. When the catalyst according to the present disclosure is used, methanation can proceed even when the hydrogen concentration is below the lower explosive concentration limit, and the safety of methane production is high.

[0034] (Catalyst manufacturing method) The method for producing the catalyst according to the present disclosure is not particularly limited, but can be produced, for example, by the following method. First, an apatite-type oxide, which is the second particle, is prepared. The apatite-type oxide can be suitably obtained by a so-called coprecipitation method. Specifically, for example, an aqueous solution (aqueous solution 1) of a rare earth nitrate hydrate (e.g., samarium nitrate hexahydrate) and a basic aqueous solution (aqueous solution 2) of a silicate hydrate (e.g., sodium metasilicate nonahydrate) are prepared, and aqueous solution 1 is dropped into aqueous solution 2, mixed, and stirred to obtain a precipitate. This precipitate is recovered, dried, and then fired. Through these steps, an apatite-type oxide is obtained. Next, the obtained apatite-type oxide is mixed with a ceramic material as the third particle, and fired to obtain a composition in which the apatite-type oxide as the second particle is supported on the ceramic material as the third particle.

[0035] Furthermore, the composition and a nitrate of a catalytic metal (e.g., Ni) can be composited by a carboxylic acid complex polymerization method. More specifically, the composition and an aqueous solution of a nitrate or chloride of the catalytic metal are evaporated to dryness to produce a carboxylic acid complex polymer. The resulting carboxylic acid complex polymer is then fired. In this way, a catalytic metal as the first particle, an apatite-type oxide as the second particle, and a ceramic material as the third particle can be composited.

[0036] Specific examples of the carboxylic acid used in the carboxylic acid complex polymerization include oxalic acid, malonic acid, glycolic acid, lactic acid, malic acid, tartaric acid, glyoxylic acid, citric acid, and gluconic acid, with malic acid or citric acid being preferred. The amount of carboxylic acid added is preferably about 1 to 5 equivalents relative to the catalyst metal. The calcination step of the carboxylic acid complex polymer can be carried out, for example, in air at 400°C to 600°C for 1 to 6 hours. These calcination temperatures and times provide a catalyst with excellent methanation activity.

[0037] The catalyst obtained may be used alone or may be mixed with other materials to be used as a catalyst composition. Prior to the calcination step, the catalyst material according to the present disclosure may be mixed with other materials and calcined together.

[0038] (Method of producing methane) A method for producing methane using the catalyst according to the present disclosure will now be described. Figure 11 is a flow chart showing a method for producing methane using the catalyst according to the present disclosure.

[0039] 11, in the method for producing methane using the catalyst according to the present disclosure, a preparation step (S10) is first performed to prepare a raw material gas. The raw material gas contains carbon dioxide and hydrogen. When the catalyst according to the present disclosure is used, methanation occurs and methane can be obtained even when the hydrogen concentration in the raw material gas is relatively low.

[0040] The concentration of carbon dioxide in the raw gas is not particularly limited as long as the effect of the present disclosure can be obtained, but may be, for example, 1 vol% or more, 2 vol% or more, or 3 vol% or more, and 50 vol% or less, 20 vol% or less, 10 vol% or less, or 8 vol% or less, based on the volume of the raw gas. The concentration of hydrogen in the raw gas is not particularly limited as long as the effect of the present disclosure can be obtained, but may be, for example, 1 vol% or more, 2 vol% or more, or 4 vol% or more, and 90 vol% or less, 80 vol% or less, 50 vol% or less, or 10 vol% or less, based on the volume of the raw gas. The concentration of hydrogen in the raw gas may typically be 1 vol% or more and 8 vol% or less, based on the volume of the raw gas.

[0041] The raw material gas may be, for example, a gas obtained by adding hydrogen to a gas containing carbon dioxide, such as exhaust gas. The raw material gas may contain an inert gas, such as nitrogen, in addition to carbon dioxide and hydrogen, or may contain a gas such as oxygen or carbon monoxide. In the preparation process of the raw material gas, for example, a pretreatment may be performed to remove specific components, such as moisture and oxygen, from the raw material gas.

[0042] Next, a methanation step is carried out (S20). Specifically, methanation can be carried out by introducing a raw material gas into a reaction tube filled with the catalyst according to the present disclosure and contacting the raw material gas with the catalyst. The flow rate of the raw material gas introduced into the reaction tube is appropriately selected according to the diameter of the reaction tube. For example, when a reaction tube with a diameter of 10 mm is used, the flow rate of the raw material gas can be 1 to 50 mL / min, preferably 10 to 50 mL / min. The catalyst may be directly filled into the reaction tube, or may be held in a state of being attached to the surface of a substrate, which is, for example, a ceramic honeycomb structure. When the catalyst is filled into the reaction tube, the amount of the catalyst can be appropriately selected according to the diameter of the reaction tube and the flow rate of the reaction gas. For example, the amount of catalyst disposed in one reaction tube may be 10 mg to 10 g, and preferably 10 mg to 1 g. When the catalyst is held on the surface of the substrate, a catalyst layer can be formed on the surface of the substrate by applying a catalyst in a slurry form to the surface of the substrate. The amount of the catalyst held can be, for example, 0.01 to 10 mg / mm based on the surface area of ​​the substrate. 2 may be also possible.

[0043] The reaction tube is maintained at a temperature at which methanation occurs. The temperature of the reaction tube may be, for example, a temperature exceeding 200°C, for example, 210°C or more, 220°C or more, 250°C or more, or 270°C or more. The temperature of the reaction tube may be 400°C or less, 370°C or less, or 360°C or less. When methanation is performed using the catalyst according to the present disclosure, it is more preferable to perform the reaction at 270°C or more and 360°C or less. The methanation reaction can be confirmed, for example, by measuring the carbon dioxide concentration in the raw material gas introduced into the reaction tube and the reaction gas discharged from the reaction tube. The heat source for heating the reaction tube is not particularly limited, and may be, for example, an electric furnace using an electric heater, or other heat medium. The temperature of the reaction tube may be constant during the methanation step (S20), or may be changed according to the progress of the reaction.

[0044] Next, methane is recovered from the reaction gas flowing out of the reaction tube (S30). Any method can be used to recover methane. The recovered methane can be used, for example, as fuel. In this way, carbon dioxide contained in the exhaust gas, etc. is converted into methane, and it can be reused as an energy source. EXAMPLES

[0045] The present invention will now be described in more detail with reference to examples, although the present invention is not limited to these examples. A catalyst according to the present disclosure was prepared as follows, and the structure of the catalyst and the progress of the methanation reaction were confirmed.

[0046] [Example 1] Dissolve Sm(NO) in deionized water (10 mL). 3 ) 3 6H 2 O (1.299 g) was dissolved to obtain solution 1. 3 In aqueous solution (20 mL) 2 SiO 3 9H 2 O (0.498 g) was dissolved in the mixture, and solution 1 was added dropwise thereto. This mixture was stirred at 60°C for 1 hour. After stirring was completed, the precipitate was collected by suction filtration and dried. The dried product was pulverized in a ball mill at 300 rpm for 3 hours. It was then fired in air at 1000°C for 2 hours. Through the above steps, samarium silicate (Sm 10 S 6 O 27 ) was obtained. Next, Sm 10 S 6 O 27 (0.4g) and γ-Al 2 O 3 (0.6 g) was mixed in ethanol (25 mL) using a ball mill at 300 rpm for 3 hours. After mixing, the mixture was fired in air at 500°C for 4 hours. Through the above process, Sm was added to the γ-alumina. 10 S 6 O 27 A composition carrying 40wt% Sm 10 S6 O 27 / γ-Al 2 O 3 ) was obtained. 0.40 g of this composition was taken and placed in deionized water (40 mL) and Ni(NO 3 ) 2 6H 2 O (0.270 g), propylene glycol (0.340 mL), and malic acid (0.372 g, 3 equivalents relative to Ni) were added. The mixture was then stirred at 90°C for 4 hours. After stirring was completed, the mixture was heated to 150°C to remove the solvent. The mixture was then calcined in air at 500°C for 4 hours. In this way, Sm was added to the γ-alumina. 10 S 6 O 27 and Ni-supported catalyst (12wt%Ni / 40wt%Sm 10 S 6 O 27 / γ-Al 2 O 3 ) was obtained.

[0047] (Methanation device) Using the catalyst obtained above, methanation was carried out under the following conditions to confirm the performance of the catalyst. A 0.1g catalyst sample was packed into a reaction tube. To hold the catalyst sample at a predetermined position in the reaction tube, both ends of the catalyst sample were filled with quartz wool. The reaction tube was placed in an electric furnace and heated so that the gas temperature introduced into the reaction tube reached a predetermined temperature. Cylinders containing carbon dioxide, hydrogen, and argon gas were prepared, and the gases were taken out and mixed in a predetermined ratio to prepare the raw material gas. The composition (volume ratio) of the raw material gas was 1% CO 2 -4%H 2 -95% Ar. This raw material gas was introduced into the reaction tube at a flow rate of 50 mL / min, and methanation was carried out by passing it through the reaction tube. Methanation was carried out at reaction temperatures of 150°C, 200°C, 250°C, 300°C, 350°C, 400°C, 450°C, and 500°C.

[0048] (Analysis of gas after reaction) The composition of the gas passing through the reaction tube was analyzed using a GC-MS (Shimadzu Corporation, GCMS-QP2010plus), and the CO 2 Conversion, CH 4 Yield, CH 4 The selectivity was calculated.

[0049] CO 2 Conversion rate (%) = (1-[CO 2 ] / [CO 2 ] 0 ) x 100 ·CH 4 Yield (%) = [CH 4 ] / [CO 2 ] 0 ×100 ·CH 4 Selection rate (%) = (CH 4 Yield) / (CO 2 Conversion rate) x 100 In the above formula, [CO 2 ] 0 is the CO in the feed gas 2 Concentration, [CO 2 ] is the amount of CO in the gas after passing through the reaction tube 2 Concentration, [CH 4 ] is the CH in the gas after passing through the reaction tube 4 The concentration is indicated.

[0050] [Example 2] Dissolve La(NO) in deionized water (10 mL). 3 ) 3 6H 2 O (1.299 g) was dissolved to obtain solution 2. 14% NH 3 In aqueous solution (20 mL) 2 SiO 3 9H 2 O (0.512 g) was dissolved in the mixture, and solution 2 was added dropwise thereto. This mixture was stirred at 60°C for 1 hour. After stirring was completed, the precipitate was collected by suction filtration and dried. The dried product was pulverized in a ball mill at 300 rpm for 3 hours. It was then fired in air at 1000°C for 2 hours. Through the above steps, lanthanum silicate (La 10 S 6 O 27) was obtained. Next, La 10 S 6 O 27 (0.4g) and γ-Al 2 O 3 (0.6 g) was mixed in ethanol (25 mL) using a ball mill at 300 rpm for 3 hours. After mixing, the mixture was fired in air at 500°C for 4 hours. Through the above process, La was added to the γ-alumina. 10 S 6 O 27 A composition carrying 40wt% La 10 S 6 O 27 / γ-Al 2 O 3 ) was obtained. 0.40 g of this composition was taken and placed in deionized water (40 mL) and Ni(NO 3 ) 2 6H 2 O (0.270 g), propylene glycol (0.340 mL), and malic acid (0.124 g, 1 equivalent to Ni) were added. The mixture was then stirred at 90°C for 4 hours. After stirring was completed, the mixture was heated to 150°C to remove the solvent. The mixture was then calcined in air at 500°C for 4 hours. In this way, La was added to the γ-alumina. 10 S 6 O 27 and Ni-supported catalyst (12wt%Ni / 40wt%La 10 S 6 O 27 / γ-Al 2 O 3 ) was obtained.

[0051] [Comparative Example 1] As a comparative example, a catalyst in which Ni was supported on γ-alumina (12 wt% Ni / γ-Al 2 O 3 Methanation was carried out in the same manner as in Example 1 except that a benzene ring was used instead of the benzene ring, and the gas after the reaction was analyzed.

[0052] The results of Example 1, Example 2, and Comparative Example 1 at a reaction temperature of 300° C. are shown in Table 1. 2 The conversion rate is shown in Figure 1.4 The yield (%) graphs are shown in Figure 2. The dotted lines in each graph indicate the CO 2 Conversion or CH 4 The yields are shown. [Table 1]

[0053] As shown in Table 1, the catalysts of Examples 1 and 2 had a higher CO 2 Conversion, CH 4 High yield and CH 4 The selectivity was also significantly high. As shown in Figures 1 and 2, it was confirmed that when the catalysts of Examples 1 and 2 were used, the methanation reaction proceeded sufficiently, especially at reaction temperatures of 400°C or lower, even when a feed gas with a carbon dioxide concentration of 1% and a hydrogen concentration of 4% was used.

[0054] (Study of raw gas) [Example 3] The same catalyst (12 wt% Ni / 40 wt% La) as that obtained in Example 2 was used. 10 S 6 O 27 / γ-Al 2 O 3 ) was used as the raw gas, with 1% CO 2 -4%H 2 -95%N 2 Methanation was carried out in the same manner as in Example 1, except that the following was used.

[0055] The results of Examples 2 and 3 at a reaction temperature of 300° C. are shown in Table 2 (the results of Example 2 are the same as those in Table 1). 2 The conversion rate is shown in Figure 3. 4 The yield (%) graphs are shown in Figure 4. The dotted lines in each graph indicate the CO 2 Conversion or CH 4 The yields are shown.

[0056] [Table 2]

[0057] As shown in Table 2, the catalyst according to the present disclosure (12 wt% Ni / 40 wt% La 10 S 6 O 27 / γ-Al 2 O 3 ), methanation proceeded using a feed gas with a carbon dioxide concentration of 1% and a hydrogen concentration of 4%, regardless of the balance gas. As shown in Figures 3 and 4, it was confirmed that even when feed gases with different compositions were used, the methanation reaction proceeded sufficiently, especially at reaction temperatures of 400°C or less. 4 The selection rate was over 95% in all cases, and CH 4 It was confirmed that the selectivity was very high. At 300 to 400 °C, Example 2, in which Ar was used as the balance gas, 2 Conversion and CH 4 The yield was higher.

[0058] (Consideration of the second particle) [Example 4] As a raw material for apatite-type oxide, Sm(NO 3 ) 3 6H 2 Nd(CH 3 COO) 3 6H 2 O is used, Na 2 SiO 3 9H 2 The same procedure as in Example 1 was repeated except for adjusting the amount of O used, and apatite-type oxide, neodymium silicate (Nd 10 S 6 O 27 In the same manner as in Example 1, Nd was added to γ-alumina. 10 S 6 O 27 and Ni-supported catalyst (12wt%Ni / 40wt%Nd 10 S 6 O 27 / γ-Al 2 O 3Using the obtained catalyst, methanation was carried out in the same manner as in Example 1.

[0059] [Example 5] As a raw material for apatite-type oxide, Sm(NO 3 ) 3 6H 2 Eu(NO 3 ) 3 6H 2 O is used, Na 2 SiO 3 9H 2 The same procedure as in Example 1 was repeated except for adjusting the amount of O used, and an apatite-type oxide, europium silicate (Eu 10 S 6 O 27 In the same manner as in Example 1, Eu was added to γ-alumina. 10 S 6 O 27 and Ni-supported catalyst (12wt%Ni / 40wt%Eu 10 S 6 O 27 / γ-Al 2 O 3 Using the obtained catalyst, methanation was carried out in the same manner as in Example 1.

[0060] [Example 6] As a raw material for apatite-type oxide, Sm(NO 3 ) 3 6H 2 Gd(NO 3 ) 3 6H 2 O is used, Na 2 SiO 3 9H 2 The same procedure as in Example 1 was repeated except for adjusting the amount of O used, and gadolinium silicate (Gd 10 S 6 O 27 In the same manner as in Example 1, Gd was added to γ-alumina. 10 S 6 O 27 The catalyst supported with Ni (12wt%Ni / 40wt%Gd 10 S6 O 27 / γ-Al 2 O 3 Using the obtained catalyst, methanation was carried out in the same manner as in Example 1.

[0061] The results of Example 1 and Examples 4 to 6 at a reaction temperature of 300° C. are shown in Table 3 (the results of Example 1 are the same as those in Table 1). 2 The conversion rate is shown in Figure 5. 4 The yield (%) graphs are shown in Figure 6. The dotted lines in each graph indicate the CO 2 Conversion or CH 4 The yields are shown.

[0062] [Table 3]

[0063] As shown in Table 3, it was confirmed that methanation proceeded in the catalysts prepared in Examples 4 to 6 in the same manner as in Example 1. As shown in Figures 5 and 6, methanation proceeded in the catalysts of Examples 4 to 6 at temperatures of 200°C or higher and 400°C or lower. 4 The highest yield was obtained at a reaction temperature of 300°C.

[0064] (Addition of other metals) [Example 7] As a raw material for apatite-type oxide, Sm(NO 3 ) 3 6H 2 O plus Co(NO 3 ) 2 6H 2 O is used, Na 2 SiO 3 9H 2 A cobalt-doped samarium silicate (Sm), which is an apatite-type oxide in which part of silicon is replaced with cobalt, was prepared in the same manner as in Example 1, except that the amount of O used was adjusted. 10 S 5 Chief of Staff 27This apatite-type oxide was supported on γ-alumina in the same manner as in Example 1, and 40 wt% Sm 10 S 5 Chief of Staff 27 / γ-Al 2 O 3 ) was obtained. 0.40 g of this composition was taken and placed in deionized water (40 mL) and Ni(NO 3 ) 2 6H 2 O (0.270 g), propylene glycol (0.340 mL), and malic acid (0.124 g, 1 equivalent to Ni) were added. The mixture was then stirred at 90°C for 4 hours. After stirring was completed, the mixture was heated to 150°C to remove the solvent. The mixture was then calcined in air at 500°C for 4 hours. In this way, Sm was added to the γ-alumina. 10 S 5 Chief of Staff 27 and Ni-supported catalyst (12wt%Ni / 40wt%Sm 10 S 5 Chief of Staff 27 / γ-Al 2 O 3 ) was obtained. Using this catalyst, methanation was carried out in the same manner as in Example 1.

[0065] (Consideration of complex polymerization conditions) [Example 8] In the same manner as in Example 7, 40 wt% Sm 10 S 5 Chief of Staff 27 / γ-Al 2 O 3 ) was obtained. 0.40 g of this composition was taken and placed in deionized water (40 mL) and Ni(NO 3 ) 2 6H 2 O (0.270 g), propylene glycol (0.340 mL), and citric acid (0.178 g, 1 equivalent to Ni) were added. The mixture was then stirred at 90°C for 4 hours. After stirring was completed, the mixture was heated to 150°C to remove the solvent. The mixture was then calcined in air at 500°C for 4 hours. In this way, Sm was added to the γ-alumina. 10 S 5 Chief of Staff 27and Ni-supported catalyst (12wt%Ni / 40wt%Sm 10 S 5 Chief of Staff 27 / γ-Al 2 O 3 ) was obtained. Using this catalyst, methanation was carried out in the same manner as in Example 1.

[0066] The results of Examples 1, 7, and 8 at a reaction temperature of 300° C. are shown in Table 4 (the results of Example 1 are the same as those in Table 1). 2 The conversion rate is shown in Figure 7. 4 The yield (%) graphs are shown in Figure 8. The dotted lines in each graph indicate the CO 2 Conversion or CH 4 The yields are shown.

[0067] [Table 4]

[0068] As shown in Table 4, it was confirmed that methanation proceeded in the catalysts prepared in Examples 7 and 8, similarly to Example 1. As shown in Figures 7 and 8, methanation proceeded in the catalysts of Examples 7 and 8 at temperatures of 200°C or higher and 400°C or lower. 2 Conversion, CH 4 The highest yield was obtained at a reaction temperature of 300°C to 350°C.

[0069] [Comparative Example 2] As Comparative Example 2, γ-alumina was not used, and Ni and Sm obtained in the same manner as in Example 1 were used. 10 S 6 O 27 A catalyst consisting of 12 wt% Ni / Sm 10 S 6 O 27 ) was prepared and methanation was carried out in the same manner as in Example 1.

[0070] The results of Example 1 and Comparative Examples 1 and 2 at a reaction temperature of 300° C. are shown in Table 5 (the results of Example 1 and Comparative Example 1 are the same as those in Table 1). 2 The conversion rate is shown in Figure 9. 4 The yield (%) graphs are shown in Figure 10. The dotted lines in each graph indicate the CO 2 Conversion or CH 4 The yields are shown.

[0071] [Table 5]

[0072] As shown in Table 5, Comparative Examples 1 and 2 had a lower CO 2 Conversion, CH 4 As shown in Fig. 9 and Fig. 10, in the temperature range of 200°C to 350°C, Example 1 had a higher CO yield than Comparative Examples 2 and 3. 2 Conversion, CH 4 The yield was high. It was believed that the catalyst according to the present disclosure exhibited a high catalytic effect due to the composite of the catalytic metal (first particle), the apatite-type oxide (second particle), and the ceramic material (third particle).

[0073] It should be understood that the embodiments and examples disclosed herein are illustrative in all respects and are not limiting in any respect. The scope of the present invention is not the above meaning, but is indicated by the claims, and is intended to include all modifications within the meaning and scope of the claims. [Industrial Applicability]

[0074] The catalyst of the present invention is particularly advantageously applied as a catalyst for producing methane by utilizing a methanation reaction.

Claims

1. comprising first particles, second particles, and third particles, the first particles are made of at least one metal selected from the group consisting of nickel, cobalt, and ruthenium; The second particles contain an apatite-type oxide represented by general formula (1), R １０ Yes ６－ｘ M ｘ O ２７ (1) (In the general formula (1), R is one or more elements selected from the lanthanoid elements, M is one or more elements selected from the group consisting of Co, Fe, and Ni, and x is 0≦x≦1.5.) the third particles are made of a ceramic material; A catalyst for methanation, wherein the first particles and the second particles are supported on the third particles.

2. At least a portion of the first particles contact the second particles; The content ratio of the first particles is 3 mass% or more and 40 mass% or less with respect to the mass of the catalyst. Catalyst for methanation according to claim 1.

3. The content ratio of the second particles is 5 mass% or more and 60 mass% or less with respect to the total mass of the second particles and the third particles. Catalyst for methanation according to claim 1 or claim 2.

4. The ceramic material is at least one selected from the group consisting of alumina, silica, cordierite, and mullite. Catalyst for methanation according to claim 1 or claim 2.

5. Providing a feed gas comprising carbon dioxide and hydrogen; and contacting the feed gas with the catalyst for methanation according to claim 1 or 2 to produce methane from carbon dioxide and hydrogen. A method for producing methane.

6. The hydrogen concentration in the raw material gas is 1 vol.% or more and 8 vol.% or less based on the volume of the raw material gas.

6. The method for producing methane according to claim 5.

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