Ammonia decomposition catalyst

Abstract

To provide an ammonia decomposition catalyst that is low-cost yet has a good ammonia conversion rate. [Solution] An ammonia decomposition catalyst having a core-shell structure comprising a core containing a first metal oxide and a shell containing a second metal oxide and covering the core, wherein the shell supports a catalytically active metal and a reaction accelerator.

Description

[Technical Field]

[0001] This disclosure relates to ammonia decomposition catalysts. [Background technology]

[0002] Ammonia decomposition catalysts are catalysts that have the function of decomposing NH3 into N2 and H2 using catalytically active metals such as Ru. As ammonia decomposition catalysts, a catalyst is known in which Ru and rare earth oxides are supported on a support made of a metal oxide other than the rare earth oxide, and the Ru is supported in an eggshell type configuration (see, for example, Patent Document 1). This eggshell type catalyst is manufactured by supporting rare earth oxides on the above-mentioned support, and then further supporting Ru. Ru is supported on the support by a process such as immersing the support on which the rare earth oxides are supported in an aqueous solution of ruthenium salt, and then contacting it with a basic aqueous solution. By forming an eggshell, the active metal species Ru is effectively utilized. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] International Publication No. 2019 / 188219 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] However, in Patent Document 1, which is based on an eggshell-shaped structure, the above method of supporting Ru is not only time-consuming but also prone to Ru loss during the process, so the resulting catalyst is inevitably expensive.

[0005] This disclosure is made in view of the above circumstances and aims to provide an ammonia decomposition catalyst that is low-cost yet has a good ammonia conversion rate. [Means for solving the problem]

[0006] An overview of this disclosure is as follows: [1] A core-shell type structure comprising a core containing a first metal oxide and a shell containing a second metal oxide and covering the core, An ammonia decomposition catalyst wherein the shell supports a catalytically active metal and a reaction accelerator. [2] The ammonia decomposition catalyst according to [1], comprising 60 to 95% by mass of the first metal oxide and 4 to 35% by mass of the second metal oxide, based on the total amount of catalyst. [3] The ammonia decomposition catalyst according to [1] or [2], comprising 0.1 to 10% by mass of the catalytically active metal and 0.5 to 5% by mass of the reaction accelerator, based on the total amount of catalyst. [4] The ammonia decomposition catalyst according to any one of [1] to [3], wherein the thickness of the shell is 30 to 200 μm. [5] The ammonia decomposition catalyst according to any one of [1] to [4], wherein the first metal oxide is cordierite. [6] The ammonia decomposition catalyst according to any one of [1] to [5], wherein the second metal oxide is γ-alumina. [7] An ammonia decomposition catalyst according to any one of [1] to [6], comprising 0.1 to 2% by mass of Ru as the catalytically active metal and 0.5 to 5% by mass of K as the reaction accelerator, based on the total amount of catalyst. [8] An ammonia decomposition catalyst according to any one of [1] to [7], comprising 2 to 10% by mass of Ni as the catalytically active metal and 1 to 5% by mass of La or Ce as the reaction accelerator, based on the total amount of catalyst. [Effects of the Invention]

[0007] According to this disclosure, an ammonia decomposition catalyst is provided that is low-cost and has a good ammonia conversion rate. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a schematic diagram showing the support in a core-shell type catalyst and the support in an eggshell type catalyst. [Modes for carrying out the invention]

[0009] Preferred embodiments of this disclosure are described in detail below. However, this disclosure is not limited to the embodiments described below.

[0010] <Ammonia decomposition catalyst> Ammonia decomposition catalysts have a core-shell structure comprising a core containing a first metal oxide and a shell containing a second metal oxide that covers the core. A support having a core-shell structure is called a core-shell support. Furthermore, the shell supports the catalytically active metal and the reaction accelerator.

[0011] In ammonia decomposition catalysts, the decomposition reaction occurs on the catalyst surface. Therefore, in order to achieve good catalytic activity while minimizing the use of active metal species such as Ru and Ni, and their accelerators such as rare earth elements and alkali metals, it is crucial to selectively support these components, including the catalytically active metals, on the catalyst surface. With this in mind, we re-examined the method of supporting catalytically active metals and found that, compared to eggshell-type catalysts obtained using a support with a uniform composition, core-shell type catalysts obtained using a support with a shell on a core exhibited a better ammonia conversion rate when the amounts of each component were used were the same. The ammonia decomposition catalyst of this disclosure is based on these findings.

[0012] Figure 1 is a schematic diagram showing the support in a core-shell type catalyst and the support in an eggshell type catalyst. Figure (a) shows the support in a core-shell type catalyst, which comprises a core 1 and a shell 2 covering the core. Figure (b) shows the support in an eggshell type catalyst, which comprises a uniform support component 3. As shown in the figure, the two catalysts have different support structures.

[0013] (core) As the first metal oxide contained in the core, a metal oxide used as a general catalyst substrate can be used. Examples of the first metal oxide include cordierite, α-alumina, silica, etc. These may be used alone or in combination of two or more. Among these, cordierite is preferable from the viewpoint that the specific surface area is small and the catalytic active metal can be selectively supported on the shell. The core may be composed of the first metal oxide.

[0014] The presence of the first metal oxide, the second metal oxide described later, the catalytic active metal, the reaction accelerator, etc. can be confirmed by powder X-ray diffraction analysis (XRD).

[0015] Based on the total amount of the catalyst, the content of the first metal oxide is preferably 60 to 95% by mass. When the content is at least the above lower limit, it is easier to effectively utilize the active component in the shell part compared to the case where it is less than the above lower limit. When the content is at most the above upper limit, it is easier to secure a sufficient amount of the active component compared to the case where it exceeds the above upper limit. From these viewpoints, the content is more preferably 70 to 95% by mass, and still more preferably 85 to 90% by mass. When the core is composed of the first metal oxide, the above content can be referred to as the content of the core.

[0016] The specific surface area of the core is preferably 10 m 2 / g or less. When the specific surface area is at most the above upper limit, it is easier to selectively support the catalytic active metal on the shell compared to the case where it exceeds the above upper limit. From this viewpoint, the specific surface area is more preferably 5 m 2 / g or less, and still more preferably 1 m 2 / g or less. The lower limit of the specific surface area is not particularly limited, but for example, it can be 0.1 m 2 / g. The specific surface area can be measured by the BET method. When the core is composed of the first metal oxide, the above specific surface area can be referred to as the specific surface area of the first metal oxide.

[0017] The shape of the core is not particularly limited and can be determined according to the actual situation in which the ammonia decomposition catalyst is used, but it can be particulate, for example. In this case, the average particle diameter D50 of the core is preferably 0.5 to 5 mm, more preferably 1 to 3 mm, and even more preferably 1.5 to 2.5 mm. The average particle diameter D50 of the core can be measured by an image-based particle size distribution analyzer.

[0018] (shell) Examples of the second metal oxide included in the shell include γ-alumina, θ-alumina, and cerium oxide. These can be used individually or in combination of two or more. Of these, γ-alumina is preferred from the viewpoint of availability and cost-effectiveness. The shell may consist of the second metal oxide.

[0019] The content of the second metal oxide is preferably 4 to 35% by mass, relative to the total amount of catalyst. When the content is above the lower limit, it is easier to secure sufficient active ingredients compared to when it is below the lower limit, and when the content is below the upper limit, it is easier to effectively utilize the active ingredients of the shell compared to when it is above the upper limit. From these viewpoints, the content is more preferably 4 to 20% by mass, and even more preferably 4 to 15% by mass. If the shell consists of a second metal oxide, the above content can be referred to as the shell content.

[0020] Based on the total amount of catalyst, the weight of the shell (for example, the total weight of the second metal oxide, catalytically active metal, and reaction accelerator) is preferably 5 to 40% by mass. When the content is above the lower limit, it is easier to secure sufficient active components compared to when it is below the lower limit, and when the content is below the upper limit, it is easier to effectively utilize the active components of the shell compared to when it is above the upper limit. From these viewpoints, the content is more preferably 5 to 20% by mass, and even more preferably 5 to 15% by mass.

[0021] The specific surface area of ​​the shell is 100 m². 2 It is preferable that the specific surface area is 120 m² or more. Having a specific surface area above the lower limit makes it easier to selectively support the catalytically active metal on the shell compared to when it is below the lower limit. From this viewpoint, the specific surface area is 120 m². 2 It is more preferable that it be 150m or more per gram. 2 It is even more preferable that the specific surface area is 300 m or more. The upper limit of the specific surface area is not particularly limited, but from the viewpoint of maintaining appropriate dispersibility of the catalytically active metal, it is 300 m. 2 It can be less than / g. If the shell is made of a second metal oxide, the above specific surface area can be said to be the specific surface area of ​​the second metal oxide.

[0022] The first and second metal oxides are different. Furthermore, the second metal oxide is located outside the first metal oxide and has a larger specific surface area. This makes it easier to selectively support the catalytically active metal on the shell.

[0023] The shell thickness is preferably 30 to 200 μm. A thickness above the lower limit makes it easier to secure sufficient active ingredients compared to a thickness below the lower limit, and a thickness below the upper limit makes it easier to effectively utilize the active ingredients in the shell compared to a thickness above the upper limit. From these viewpoints, a thickness of 40 to 100 μm is more preferable, and 40 to 60 μm is even more preferable. The shell thickness can be measured by determining the difference between the shell thickness and the core size using an image-based particle size distribution analyzer.

[0024] Examples of catalytically active metals supported by the shell include the noble metal Ru, and transition metals such as Ni, Fe, and Co. The catalytically active metal is the active component for ammonia decomposition. These catalytically active metals may be used individually or in alloys of two or more. Of these, Ru is particularly preferred from the viewpoint of catalytic performance, and transition metals (of which Ni is particularly preferred from the viewpoint of catalytic performance) are particularly preferred from the viewpoint of economy.

[0025] The content of catalytically active metals is preferably 0.1 to 10% by mass, relative to the total amount of catalyst. The content of catalytically active metals can be adjusted according to their type.

[0026] When the catalytically active metal is Ru, it is more preferable that the content of the catalytically active metal is 0.1 to 2% by mass, based on the total amount of catalyst. When the content is above the lower limit, it is easier to ensure catalytic activity compared to when it is below the lower limit, and when the content is below the upper limit, it is easier to increase the activity per unit amount of metal compared to when it is above the upper limit. From these viewpoints, it is even more preferable that the content is 0.3 to 0.7% by mass.

[0027] When the catalytically active metal is a transition metal such as Ni, it is more preferable that the content of the catalytically active metal is 2 to 10% by mass, relative to the total amount of catalyst. When the content is above the lower limit, it is easier to ensure catalytic activity compared to when it is below the lower limit, and when the content is below the upper limit, it is easier to increase the activity per unit amount of metal compared to when it is above the upper limit. From these viewpoints, it is even more preferable that the content is 3 to 6% by mass.

[0028] Based on the total amount of shell, the content of catalytically active metal is preferably 1 to 30% by mass, and more preferably 3 to 30% by mass. The content of catalytically active metal can be adjusted according to its type.

[0029] When the catalytically active metal is Ru, the catalytically active metal content is more preferably 1 to 10% by mass, and even more preferably 3 to 5% by mass, based on the total amount of shell.

[0030] When the catalytically active metal is a transition metal such as Ni, the content of the catalytically active metal is more preferably 10 to 30% by mass, and even more preferably 15 to 25% by mass, based on the total amount of shell.

[0031] Examples of reaction accelerators supported on the shell together with the catalytically active metal include alkali metals such as Na, K, and Cs, alkaline earth metals such as Ca and Ba, and rare earth elements such as La and Ce. The reaction accelerator is an agent that promotes the ammonia decomposition reaction by the catalytically active metal. These reaction accelerators may be used individually or in combination of two or more. Of these, K is preferred from the viewpoint of availability and cost-effectiveness, and among the rare earth elements, La and Ce are preferred from the viewpoint of availability and cost-effectiveness.

[0032] The catalytic activity of Ru is higher than that of transition metals such as Ni, and the type of reaction accelerator should be adjusted according to the type of catalytic metal, while also considering cost. For example, when the catalytic metal is Ru, alkali metals or alkaline earth metals are preferred as reaction accelerators from the viewpoint of availability and economics, and when the catalytic metal is a transition metal such as Ni, rare earth elements are preferred as reaction accelerators from the viewpoint of improving the accelerator effect.

[0033] The content of the reaction accelerator is preferably 0.5 to 5% by mass, relative to the total amount of catalyst. The content of the reaction accelerator can be adjusted according to the type of catalytically active metal.

[0034] When the catalytically active metal is Ru, it is preferable to include 0.5 to 5% by mass of an alkali metal or alkaline earth metal (especially K) as a reaction accelerator, based on the total amount of catalyst. A content above the lower limit makes it easier to improve low-temperature activity compared to a content below the lower limit. A content below the upper limit makes it easier to obtain the accelerator effect while keeping costs down compared to a content above the upper limit. From these viewpoints, a content of 1 to 3% by mass is more preferable.

[0035] When the catalytically active metal is a transition metal (especially Ni), it is more preferable to include 1 to 5% by mass of a rare earth element (especially La or Ce) as a reaction accelerator, relative to the total amount of catalyst. When the content is above the lower limit, the accelerator effect is more easily exhibited compared to when it is below the lower limit. Also, when the content is below the upper limit, it is easier to obtain the accelerator effect while keeping costs down compared to when it is above the upper limit. From these viewpoints, it is even more preferable that the content be 2 to 4% by mass.

[0036] The content of the reaction accelerator is preferably 1 to 20% by mass, based on the total amount of shell. The content of the reaction accelerator can be adjusted according to its type.

[0037] When the catalytically active metal is Ru, the content of alkali metals or alkaline earth metals (especially K) as reaction accelerators is more preferably 4 to 20% by mass, and even more preferably 8 to 12% by mass, based on the total amount of shell.

[0038] When the catalytically active metal is a transition metal (especially Ni), the content of rare earth elements (especially La or Ce) as reaction accelerators is more preferably 1 to 15% by mass, and even more preferably 5 to 10% by mass, based on the total amount of shell.

[0039] The component composition of the catalyst can be determined by general analytical methods for metals, metal oxides, and metal salts.

[0040] <Method for producing ammonia decomposition catalyst> The method for producing an ammonia decomposition catalyst is: A step of coating a core containing a first metal oxide with a suspension containing a second metal oxide and, if necessary, a binder, A process of firing the coated core to form a shell containing a second metal oxide on the core surface, The process includes a step of supporting a catalytically active metal and a reaction accelerator on a core-shell carrier comprising a core and a shell. The core-shell carrier can be manufactured by referring to the contents of Japanese Patent No. 4772270.

[0041] Here, the suspension may contain inorganic binders such as boehmite and pseudoboehmite, and organic binders such as polyvinyl alcohol and cellulose, for the purpose of improving the bonding strength between the first metal oxide and the second metal oxide, and between the second metal oxides themselves. Preferably, the inorganic binder is selected to be a compound that becomes the second metal oxide contained in the shell upon firing. For example, the inorganic binders such as boehmite and pseudoboehmite ultimately become γ-alumina upon firing. On the other hand, the organic binder is burned away upon firing.

[0042] The amount of binder used is preferably 10 to 30 parts by mass per 100 parts by mass of the second metal oxide. The amount of binder used can be adjusted depending on the type of second metal oxide and binder.

[0043] The suspension is prepared by dispersing a second metal oxide and, if necessary, a binder in a liquid medium such as water, nitric acid, or hydrochloric acid.

[0044] The second metal oxide and binder are generally available as coarse-grained powdered raw materials. Therefore, a process of grinding or dispersing these raw materials may be carried out prior to coating. Such processes include, for example, ball milling or ultrasonic dispersion of the suspension.

[0045] There are no particular restrictions on the method of coating using a suspension, but general coating techniques such as spray coating can be used.

[0046] By firing the coated core at 500-700°C for 3-5 hours in an air atmosphere, a core-shell support can be obtained comprising a core containing a first metal oxide and a shell containing a second metal oxide that covers the core.

[0047] In the step of supporting a catalytically active metal and a reaction accelerator on a core-shell carrier, for example, an aqueous solution containing a precursor of the catalytically active metal and a precursor of the reaction accelerator is brought into contact with the core-shell carrier. This aqueous solution is prepared by dispersing nitrates, chlorides, etc. of the catalytically active metal and nitrates, carbonates, chlorides, etc. of the reaction accelerator in a liquid medium such as water.

[0048] After thoroughly drying the core-shell support, which has been brought into contact with the above aqueous solution and in which the shell contains a precursor of the catalytically active metal and a precursor of the reaction accelerator, heat treatment is performed at 500-550°C for 2-3 hours in a reducing atmosphere under a hydrogen gas stream. This process allows the catalytically active metal and the reaction accelerator to be supported on the shell in a core-shell support comprising a core containing a first metal oxide and a shell containing a second metal oxide and covering the core. If the catalytically active metal is Ni, a step of oxidizing the Ni precursor at 400°C for 2-3 hours may be performed before the heat treatment in the reducing atmosphere.

[0049] The amounts of each component in the above suspension and aqueous solution may be adjusted as appropriate according to the desired composition of the ammonia decomposition catalyst. [Examples]

[0050] The present invention will be described in more detail by the following examples, but the present invention is not limited to these examples.

[0051] (Example 1) 450 g of γ-alumina and 94 g of pseudo-boehmite were added to 1220 g of distilled water, and this was mixed with 40 g of concentrated nitric acid and 192 g of a 15% aqueous solution of polyvinyl alcohol to prepare a suspension. The obtained suspension was ground in a ball mill until the average particle size D50 of the alumina was 3 to 5 μm. Then, the suspension was sprayed onto the core material, cordierite (average particle size D50: 1.5 to 2.5 mm), using a spray coating apparatus to coat the core surface with alumina and boehmite. The resulting coated body was fired at 600°C for 3 hours in an air atmosphere to obtain a core-shell carrier (average particle size D50: 1.6 to 2.6 mm) having a cordierite core and a γ-alumina shell (thickness: approximately 50 μm). Next, 84 g of the obtained core-shell support was placed in a flask, and then a mixed aqueous solution containing 8 g of nitrate Ru solution (Ru concentration: 4.7 mass%), 3 g of nitrate K, and 6 g of distilled water was added. The flask was then heated to 95-100°C in a water bath while rotating at 1-5 rpm to evaporate the water. The obtained nitrate Ru and nitrate K-supported γ-alumina was subjected to a reduction treatment in a tubular reactor at 500°C for 2 hours under a hydrogen gas stream to obtain a RuK-supported γ-alumina core-shell catalyst.

[0052] (Examples 2 and 3) A RuK-supported core-shell catalyst was obtained in the same manner as in Example 1, except that the shell thickness was increased by extending the spray coating time (thickness in Example 2: approximately 100 μm, thickness in Example 3: approximately 200 μm).

[0053] (Example 4) A RuK-supported core-shell catalyst was obtained in the same manner as in Example 1, except that the amount of Ru nitrate solution in the Ru nitrate / K nitrate aqueous solution was increased to 10 g.

[0054] (Example 5) A RuCs-supported core-shell catalyst was obtained by preparing a solution in the same manner as in Example 2, except that 15 g of nitrate Ru was used and 3 g of nitrate Cs was added instead of nitrate K.

[0055] (Example 6) In a flask, 84 g of the core-shell carrier obtained in Example 2 was immersed in an aqueous solution prepared by dissolving 22 g of nickel nitrate hexahydrate and 6 g of lanthanum nitrate hexahydrate in 16 g of distilled water, and the flask was heated to 95 - 100 °C in a water bath while rotating to evaporate the water. The obtained γ-alumina supported with nickel nitrate and lanthanum nitrate was calcined at 400 °C for 3 hours under a stream of air. Then, a NiLa-supported core-shell catalyst was obtained by performing a reduction treatment and a slow oxidation treatment at 550 °C for 3 hours under a stream of hydrogen.

[0056] (Comparative Example 1) As the carrier, a spherical (granular) γ-alumina carrier (average particle diameter D50: 1.5 - 2.5 mm, specific surface area: 200 m 2 / g) was used, and a Ru-supported γ-alumina catalyst was prepared in the same manner as in Example 1 except that only an aqueous solution of ruthenium nitrate was used as the impregnating solution. 47 g of the carrier, 40 g of the ruthenium nitrate solution, and 15 g of distilled water were used.

[0057] (Comparative Example 2) An RuK-supported alumina catalyst was obtained in the same manner as in Comparative Example 1 except that an aqueous solution prepared by additionally dissolving 17 g of potassium nitrate in 46 g of the aqueous solution of ruthenium nitrate was used.

[0058] (Comparative Example 3) 84 g of the core-shell carrier obtained in Example 2 was added to a mixed aqueous solution to which a palladium nitrate solution (Pd concentration: 10.0%) and 20 g of distilled water were added. Then, the flask was heated to 95 - 100 °C in a water bath while rotating at 1 - 5 rpm to evaporate the water. The obtained palladium nitrate-supported alumina was calcined at 400 °C for 2 hours under air in a tubular reactor to obtain a Pd-supported core-shell catalyst.

[0059] (Comparative Example 4) For Example 6, a spherical γ-alumina carrier (average particle diameter D50: 1.5 - 2.5 mm, specific surface area: 200 m 2 / g) was used as the carrier, and a Ni-supported γ-alumina catalyst was prepared in the same manner except that a single nickel nitrate solution was used instead of the mixed solution of nickel nitrate / lanthanum nitrate.

[0060] (Comparative Example 5) The preparation was carried out similarly to Comparative Example 4, except that a mixed solution of Ni nitrate and La nitrate was used instead of a Ni nitrate solution, to obtain a NiLa-supported γ-alumina catalyst. 66 g of Ni nitrate, 20 g of La nitrate hexahydrate, and 22 g of distilled water were used.

[0061] (Ammonia conversion rate evaluation) The ammonia conversion rate (ability to decompose ammonia into hydrogen and nitrogen) of the catalysts obtained in each example was evaluated using a gas-phase fixed-bed flow reactor. The set conditions were: gas: 100% pure NH3 gas, pressure: atmospheric pressure, catalyst amount: SV = 5000h relative to NH3 gas. -1 The reaction temperature was set to 500-550°C. Undecomposed NH3 in the outlet gas was trapped with a dilute sulfuric acid solution, and the flow rates of the generated N2 and H2 were measured using a membrane flow meter. From this, the NH3 conversion rate was calculated. As a performance criterion, an NH3 conversion rate of less than 75% at any temperature was considered unacceptable. The results are shown in Table 2.

[0062] [Table 1]

[0063] [Table 2]

[0064] A comparison of Comparative Example 1 and Comparative Example 2 revealed that adding K to the Ru-supported catalyst improved the NH3 conversion rate. This confirmed the action of K as a reaction accelerator.

[0065] According to Examples 1-3, the Ru and K content of the shell portion was almost the same, and only the proportion (weight) of the shell portion differed, but there was almost no difference in the NH3 conversion rate at 500°C. Since changing the proportion of the shell portion has almost no effect on performance, even if the Ru loading amount of Comparative Example 2 (non-core shell) was converted to a core shell and reduced to Ru 0.5% as in Example 1, the performance can be maintained.

[0066] Example 4 increased the amount of Ru based on the total amount of shell compared to Examples 1-3. Despite having a lower amount of Ru based on the total amount of catalyst compared to Examples 2 and 3, Example 4 showed the highest NH3 conversion rate at 500°C. In other words, by increasing the amount of Ru based on the total amount of shell, it was possible to improve catalytic activity while reducing the amount of Ru based on the total amount of catalyst.

[0067] Comparative Example 3 is a catalyst with a core-shell structure and the active metal species being Pd, and its performance is significantly inferior to that of the Ru-based catalyst.

[0068] Example 5 is a variation of Example 2 in which the K accelerator was replaced with a Cs accelerator, and it exhibits equivalent performance.

[0069] A comparison of Comparative Example 4 and Comparative Example 5 revealed that the addition of La to the Ni-supported catalyst improved the NH3 conversion rate. This confirmed the action of La as a reaction accelerator.

[0070] From a comparison of Comparative Example 5 and Example 6, it was found that by forming a core-shell structure in the NiLa-supported alumina catalyst, a reasonably good NH3 conversion rate can be achieved even with a significantly reduced amount of Ni and La added. It is understood that the amount of metal used can be reduced with core-shell catalysts.

[0071] Comparative Example 6 is a catalyst obtained by removing La from Example 6, and it can be seen that the NH3 conversion rate is improved by more than 10% by adding La. [Industrial applicability]

[0072] This disclosure relates to an ammonia decomposition catalyst that has a good ammonia conversion rate at a relatively low temperature of about 500°C while being low cost. The hydrogen extracted by this catalytic reaction can be used in fuel cells, boiler power generation, ship fuel, etc., or it can be used to co-fire ammonia in industrial furnace burners, engines, turbine power generation, etc., for the purpose of improving the combustion characteristics of ammonia. [Explanation of Symbols]

[0073] 1...Core, 2...Shell, 3...Uniform carrier component.

Claims

1. It has a core-shell type structure comprising a core containing a first metal oxide and a shell containing a second metal oxide and covering the core, An ammonia decomposition catalyst wherein the shell supports a catalytically active metal and a reaction accelerator.

2. The ammonia decomposition catalyst according to claim 1, comprising 60 to 95% by mass of the first metal oxide and 4 to 35% by mass of the second metal oxide, based on the total amount of catalyst.

3. The ammonia decomposition catalyst according to claim 1 or 2, comprising 0.1 to 10% by mass of the catalytically active metal and 0.5 to 5% by mass of the reaction accelerator, based on the total amount of catalyst.

4. The ammonia decomposition catalyst according to claim 1 or 2, wherein the thickness of the shell is 30 to 200 μm.

5. The ammonia decomposition catalyst according to claim 1 or 2, wherein the first metal oxide is cordierite.

6. The ammonia decomposition catalyst according to claim 1 or 2, wherein the second metal oxide is γ-alumina.

7. The ammonia decomposition catalyst according to claim 1 or 2, comprising 0.1 to 2% by mass of Ru as the catalytically active metal and 0.5 to 5% by mass of K as the reaction accelerator, based on the total amount of catalyst.

8. The ammonia decomposition catalyst according to claim 1 or 2, comprising 2 to 10% by mass of Ni as the catalytically active metal and 1 to 5% by mass of La or Ce as the reaction accelerator, based on the total amount of catalyst.

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