Ammonia decomposition catalyst and method for producing same

Abstract

The present invention relates to a catalyst for the decomposition of ammonia and a method for producing the same, and more specifically to a catalyst for the decomposition of ammonia, which comprises an MgAlO spinel support and ruthenium, the ruthenium being present in an amount of 0.1 to 5 wt % based on the total catalyst weight; a method for producing the same; and an ammonia decomposition method using the same.

Description

[Technical Field]

[0001] The present invention relates to a catalyst for ammonia decomposition and a method for producing the same, and more particularly to a catalyst utilizing a spinel support obtained by heat treatment of a precursor having a hydrotalcite structure and a method for producing the same. [Background technology]

[0002] In order to overcome climate change and various environmental pollution problems, efforts are underway worldwide to restructure the carbon-based energy society into one based on renewable energy. However, because the distribution of renewable energy is uneven depending on region and time, in order to make renewable energy universally available, it is necessary to build an inter-national or inter-continental trade system using energy storage devices that can store renewable energy in large quantities.

[0003] Hydrogen is a material capable of storing large amounts of energy stably for long periods. Various countries, including Europe, Japan, Saudi Arabia, and Australia, are working to build a global renewable energy trading system using hydrogen as a renewable energy storage medium. Meanwhile, the Korean government's Hydrogen Economy Revitalization Roadmap sets a goal of increasing domestic hydrogen supply. However, hydrogen has a very low energy density relative to its volume. Therefore, research into chemical and physical hydrogen storage methods is essential to economically importing large amounts of hydrogen from overseas. To this end, various hydrogen storage materials, including ammonia (NH3), liquid organic hydrogen compounds (LOHCs), and liquefied hydrogen (LH2), are being actively researched. Ammonia, in particular, is attracting attention as a hydrogen (renewable energy) storage medium with great commercial viability due to its high hydrogen storage capacity (17.6 wt%, 108 g / L), ease of storage (8.74 Kpa, 20°C), and ability to utilize existing ammonia storage and transportation infrastructure.

[0004] One ammonia molecule consists of three hydrogen atoms and one nitrogen atom, and when this ammonia molecule is decomposed at high temperatures, only hydrogen and nitrogen gas, which makes up 78% of air, are produced. Ammonia has the advantage of being able to use existing infrastructure for large-scale storage and long-distance transportation, and in addition, since only hydrogen and nitrogen are produced, carbon dioxide emissions can be minimized.

[0005] However, the biggest problem is that the ammonia decomposition reaction itself proceeds at high temperatures and pressures, so a considerable amount of heat must be supplied to heat the reactor. The ammonia decomposition reaction is an endothermic reaction in which two ammonia molecules are decomposed into one nitrogen molecule and three hydrogen molecules, as shown in the following formula, and requires a heat quantity of approximately 46 kJ / mol. 2NH3(g) → N2(g) + 3H2(g)

[0006] Although the thermodynamic ammonia conversion rate reaches 99.1% at 400°C and 1 atmosphere, in practice, the reaction is operated at a higher reaction temperature of 550°C or higher due to the kinetic energy barrier. Therefore, the reaction temperature can be significantly reduced by using a solid powder catalyst during the reaction. Meanwhile, as disclosed in JP 2016-198720 A, for example, commonly used ruthenium-based catalysts have high ammonia decomposition activity but are very expensive, making them uneconomical from a process standpoint. Therefore, there is a need for the development of an economical ruthenium catalyst that has a low ruthenium content and exhibits high activity and durability at temperatures lower than existing reaction temperatures.

[0007] In particular, to efficiently proceed with the ammonia dehydrogenation reaction, it is necessary to promote nitrogen recombination, which is the reaction rate-determining step, and for this, an appropriate metal-nitrogen binding energy is required. The size of ruthenium metal also affects the degree of reaction activity, so technological development is needed to obtain the size of ruthenium that shows the best activity in the ammonia dehydrogenation reaction. Summary of the Invention [Problem to be solved by the invention]

[0008] One aspect of the present invention is to provide an ammonia decomposition catalyst that is excellent in ammonia decomposition and hydrogen production capabilities, and has high activity and durability.

[0009] Another aspect of the present invention is to provide a method for producing a catalyst having the above properties.

[0010] Another aspect of the present invention is to provide a method for decomposing ammonia using the catalyst of the present invention. [Means for solving the problem]

[0011] According to one embodiment of the present invention, there is provided a catalyst for ammonia decomposition, comprising an MgAl2O4 spinel support and ruthenium, wherein the ruthenium is present in an amount of 0.1 to 5 wt % based on the total weight of the catalyst.

[0012] According to another embodiment of the present invention, there is provided a method for producing a catalyst for ammonia decomposition, including: a first heat-treatment step of heat-treating a precursor mixture containing magnesium oxide and aluminum oxide and having a hydrotalcite structure to obtain an MgAlO spinel support; a step of mixing the spinel support with an aqueous ruthenium precursor solution to prepare a mixture; and a second heat-treatment step of drying the mixture.

[0013] According to yet another embodiment of the present invention, the catalyst for ammonia decomposition of the present invention is used to produce a GHSV of 10,000 to 30,000 mL g at a reaction temperature of 300 to 700°C. cat -1 h -1 A method for decomposing ammonia is provided, comprising treating ammonia at conditions. [Effects of the Invention]

[0014] The ammonia decomposition catalyst according to the present invention has excellent hydrogen production capacity at temperatures of 550°C or less, and has high catalytic activity and durability. The ammonia decomposition catalyst according to one embodiment of the present invention can maximize ammonia decomposition efficiency by optimizing metal-support interaction, and can exhibit higher stability and activity with a smaller ruthenium content than conventional ammonia decomposition catalysts at the same reaction temperature and gas space velocity. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a graph showing the results of XRD analysis of an alumina-magnesia mixture as a precursor of a catalyst support for ammonia dehydrogenation according to one embodiment of the present invention. [Figure 2] 1 is a graph showing the XRD evaluation results of the MgAl2O4 material having a spinel structure of the support synthesized according to one embodiment of the present invention. [Figure 3] 1 is a graph showing the results of XRD evaluation of the catalyst for ammonia dehydrogenation according to one embodiment of the present invention, depending on the type of support. [Figure 4] 1 is a graph showing the results of evaluating ammonia decomposition efficiency depending on the support in an ammonia decomposition reaction of the ammonia dehydrogenation catalyst according to one embodiment of the present invention. [Figure 5a] FIG. 5a is a TEM analysis photograph of the catalyst for ammonia dehydrogenation reaction according to one embodiment of the present invention. [Figure 5b] Figure 5b is a graph showing the particle size distribution, and the average particle size was measured to be 2.54 nm. [Figure 6] 1 is a graph showing the results of evaluating ammonia decomposition performance depending on the ruthenium content in an ammonia dehydrogenation catalyst according to one embodiment of the present invention. [Figure 7] 1 is a graph showing the results of evaluating ammonia decomposition performance according to changes in atmospheric conditions for heat treatment (second heat treatment) when ruthenium is supported in an ammonia dehydrogenation catalyst according to one embodiment of the present invention. [Figure 8a]8a is a graph showing the ammonia decomposition performance evaluation results for the ammonia dehydrogenation catalyst according to one embodiment of the present invention, where GHSV is 30,000 mL g / h. [Figure 8b] 8a and 8b are graphs showing the ammonia decomposition performance evaluation results for the ammonia dehydrogenation catalyst according to one embodiment of the present invention, where the temperature of the heat treatment (first heat treatment) during the preparation of the support is changed. FIG. 8b shows the results when GHSV is 20,000 mL g / h. [Figure 8c] 8c is a graph showing the ammonia decomposition performance evaluation results for the ammonia dehydrogenation catalyst according to one embodiment of the present invention, where GHSV is 10,000 mL g / h. [Figure 9a] 9A and 9B are graphs showing the ammonia decomposition performance evaluation results for the ammonia dehydrogenation catalyst according to an embodiment of the present invention, where the second heat treatment temperature is changed. FIG. 9A shows the results when GHSV is 30,000 mL gcat −1 h −1 . [Figure 9b] 9b is a graph showing the ammonia decomposition performance evaluation results for the ammonia dehydrogenation catalyst according to an embodiment of the present invention, where the second heat treatment temperature is changed. FIG. 9b is a graph showing the results when GHSV is 20,000 mL gcat −1 h −1 . [Figure 9c] 9c is a graph showing the ammonia decomposition performance evaluation results for the ammonia dehydrogenation catalyst according to an embodiment of the present invention, where GHSV is 10,000 mL gcat −1 h −1 . DETAILED DESCRIPTION OF THE INVENTION

[0016] The present invention will be described in detail below with reference to the accompanying drawings, in which: FIG. 1 is a block diagram of a semiconductor device according to a first embodiment of the present invention; FIG. 2 is a block diagram of a semiconductor device according to a first embodiment of the present invention; FIG. 3 is a block diagram of a semiconductor device according to a first embodiment of the present invention;

[0017] According to the present invention, there is provided a catalyst for ammonia decomposition that can produce high-purity hydrogen at temperatures of 550° C. or less. The catalyst of the present invention is a ruthenium-based catalyst for ammonia decomposition that has very high catalytic activity and durability.

[0018] More specifically, the ammonia decomposition catalyst of the present invention comprises an MgAlO spinel support and ruthenium, with the ruthenium content being 0.1 to 5 wt % based on the total catalyst weight, for example, 1 to 4 wt %, or 1 to 3 wt %, and preferably 1 to 2 wt %. If the ruthenium content is less than 0.1 wt %, the catalytic activity may be insufficient. If the ruthenium content exceeds 5 wt %, the increased ruthenium concentration on the catalyst surface can cause ruthenium particles to clump together, increasing the particle size of the ruthenium and resulting in reduced catalytic activity and durability. The ammonia decomposition catalyst of the present invention can exhibit excellent catalytic activity even when used in a relatively small amount.

[0019] The ruthenium contained in the catalyst of the present invention has an average particle size of 2 to 5 nm, for example, 2 to 3 nm, and therefore can exhibit excellent activity in the ammonia dehydrogenation reaction.

[0020] As described above, the present invention provides a catalyst for ammonia decomposition reaction that supports ruthenium particles with a particle size of 2 to 5 nm, which exhibits high specific surface area, basicity, and homogeneity by introducing MgAl2O4 as a support, and exhibits the best activity in ammonia decomposition reaction.

[0021] The catalyst of the present invention can be prepared using a precursor mixture containing magnesium oxide and aluminum oxide and having a hydrotalcite structure. More specifically, the catalyst comprises a first heat treatment step of heat treating the precursor mixture containing magnesium oxide and aluminum oxide and having a hydrotalcite structure to obtain an MgAlO spinel support; a step of mixing the spinel support with an aqueous ruthenium precursor solution to prepare a mixture; and The method includes a step of subjecting the mixture to a second heat treatment after drying.

[0022] According to the present invention, magnesia is chemically bonded to alumina (Al2O3) with high acidity, and the basicity of the catalyst is increased by using MgAl2O4 with a spinel structure, thereby enabling the synthesis of an ammonia decomposition catalyst that can enhance metal-support interaction.

[0023] The ruthenium precursor that can be used in the present invention can be at least one selected from the group consisting of ruthenium chloride (RuCl), ruthenium acetylate (Ru(CHO)), ruthenium oxide (RuO), and hydrates thereof, and preferably ruthenium(III) chloride hydrate can be used.

[0024] In this case, the precursor mixture may contain 10 to 40 wt % of magnesia (MgO), for example, 20 to 30 wt %, based on the total weight of the precursor mixture. If the magnesia (MgO) content is less than 10 wt % or exceeds 40 wt %, catalytic activity tends to decrease.

[0025] In the first heat treatment step of heat treating the precursor mixture to obtain the MgAlO spinel support, the first heat treatment can be performed at 500 to 900°C for 1 to 10 hours, for example, at 600 to 800°C for 4 to 8 hours. If the first heat treatment temperature and time are below or exceed the above ranges, the catalytic activity may be reduced.

[0026] Here, the first heat treatment may be performed in an atmosphere of at least one reducing gas selected from the group consisting of hydrogen and nitrogen.

[0027] On the other hand, the second heat treatment can be carried out at 600 to 1000° C. for 1 to 10 hours, for example, at 700 to 900° C. for 4 to 8 hours. If the second heat treatment temperature and time are below or exceed the above ranges, the catalytic activity may decrease.

[0028] In this case, the second heat treatment can be performed in an atmosphere of at least one gas selected from the group consisting of hydrogen and nitrogen, and preferably in an atmosphere of at least one reducing gas selected from the group consisting of hydrogen and nitrogen.

[0029] According to the present invention, the specific surface area is 50 to 200 m 2 / g, e.g., 90-240m 2 / g and an average pore diameter of 10 to 20 nm, for example, 12 to 16 nm. In addition, the ammonia decomposition catalyst according to the present invention has excellent hydrogen production ability at temperatures of 550°C or less, and has high catalytic activity and durability.

[0030] Furthermore, according to another embodiment of the present invention, a GHSV of 10,000 to 30,000 mL g is obtained at a reaction temperature of 300 to 700°C using a catalyst for ammonia decomposition. cat -1 h -1 The reaction temperature may be, for example, 500 to 550°C.

[0031] When using the ammonia decomposition catalyst according to the present invention, the metal-support interaction can be optimized to maximize ammonia decomposition efficiency, and higher stability and activity can be exhibited with a smaller ruthenium content at the same reaction temperature and gas space velocity compared to conventional ammonia decomposition catalysts. [Example]

[0032] 1. Manufacture of ammonia decomposition catalyst Example (1)Support synthesis A magnesium oxide-aluminum oxide mixture (Sasol, MG30) with a hydrotalcite structure was used as the support precursor, and the support was synthesized by heat treatment (first heat treatment) at a temperature of 600 to 900°C in an air atmosphere for 6 hours, with a heating rate of 5°C / min.

[0033] When the temperature applied to the support by the first heat treatment is 600°C, the support is called MgAl2O4-600, when it is 700°C, MgAl2O4-700, when it is 800°C, MgAl2O4-800, and when it is 900°C, MgAl2O4-900.

[0034] (2) Ruthenium support Ruthenium(III) chloride hydrate was used as the ruthenium precursor, and an aqueous solution of the ruthenium precursor was prepared by dissolving it in 100 mL of water. The ruthenium precursor aqueous solution prepared using a rotary evaporator and the MgAl2O4-800 support obtained in (1) above were stirred at room temperature. The bath temperature was then increased to 80°C, the pressure was set to 0.08 MPa, and the mixture was stirred until the solution was completely evaporated. The resulting solid was stored in a drying oven at 100°C for at least 12 hours. The dried catalyst was then subjected to a second heat treatment at 800°C for 6 hours to obtain the Ru / MgAl2O4 catalyst.

[0035] Using the MgAl2O4-800 support, Ru / MgAl2O4 catalysts with ruthenium contents of 0.1, 0.2, 0.5, 1.0, 2.0, and 3.0 wt. % based on the total catalyst weight were prepared by the above-described ruthenium loading process.

[0036] Additionally, Ru / MgAl2O4 catalysts were prepared using the MgAl2O4-800 support through the ruthenium loading process described above, in a H2 / N2 mixture (hydrogen / nitrogen atmosphere), N2 (nitrogen atmosphere), or air atmosphere depending on the second heat treatment atmosphere.

[0037] Furthermore, Ru / MgAl2O4 catalysts were prepared using MgAl2O4 samples (MgAl2O4-600, MgAl2O4-700, and MgAl2O4-900) that were first heat-treated at different temperatures from 600 to 900°C as supports.

[0038] Comparative Example Comparative Example 1 Using an Al2O3 support, a Ru / Al2O3 catalyst containing 3 wt% ruthenium based on the weight of the total catalyst was prepared according to 1.(2) above.

[0039] Comparative Example 2 Using an MgO support, a Ru / MgO catalyst containing 3 wt % ruthenium based on the weight of the total catalyst was prepared according to 1.(2) above.

[0040] Comparative Example 3 Using a MgOAl2O3 support, in which MgO and Al2O3 were physically mixed in a 5:5 ratio, a Ru / MgO+Al2O3 catalyst containing 3 wt% ruthenium based on the weight of the total catalyst was prepared according to 1.(2) above.

[0041] 2. Evaluation of ammonia decomposition reaction efficiency 80 mg of each catalyst obtained in 1 above was placed in a reactor, and ammonia decomposition efficiency was evaluated by injecting ammonia at 550°C, 500°C, 450°C, and 400°C. After the ammonia decomposition reaction, the gas concentration was measured by gas chromatography, and the ammonia decomposition efficiency was calculated based on the measured concentration.

[0042] 3. Experimental Example Experimental Example 1: XRD Characterization of Support Precursor The material used as the support precursor was an alumina-magnesia mixture with a hydrotalcite structure, in which magnesia (MgO) was contained at 30 wt% based on the total weight of the mixture. XRD analysis of the material confirmed a layered structure, as shown in Figure 1.

[0043] Experimental Example 2: Confirmation of characteristics depending on the substrate heat treatment temperature 1) XRD characteristics confirmation MgAl2O4 spinel was synthesized by first heat treatment of the alumina-magnesia mixture, which had a hydrotalcite structure as the support precursor. XRD analysis was performed to analyze the structural characteristics of the support material as the first heat treatment temperature changed, and the results are shown in Figure 2. The support was synthesized as described in 1.(1) above. It can be seen that as the first heat treatment temperature increased, the intensity of the diffraction peaks associated with MgAl2O4 due to the formation of the spinel structure increased.

[0044] 2) Confirmation of specific surface area characteristics In addition, BET evaluation was carried out to analyze the pore structure characteristics of the support depending on the change in the first heat treatment temperature, and the results are summarized in the following Table 1. At this time, the support was synthesized according to the above 1.(1).

[0045] [Table 1]

[0046] Referring to Table 1 above, it can be seen that as the first heat treatment temperature increases, the specific surface area of ​​the support decreases.

[0047] Experimental Example 3: Confirmation of the characteristics of ruthenium-supported catalysts XRD analysis was performed to confirm the material characteristics of Ru / MgAl2O4 and Ru / Al2O3 loaded with 3 wt% ruthenium, and the results are shown in Figure 3. No peaks due to ruthenium loading were observed, and only the XRD pattern corresponding to the support was recorded.

[0048] Experimental Example 4: Confirmation of the ammonia decomposition efficiency of ruthenium-supported catalysts The ammonia decomposition efficiency of Ru / MgAl2O4, Ru / MgO, Ru / Al2O3, all loaded with 3 wt% ruthenium, was compared with that of Ru / MgO+Al2O3, which was loaded with Ru on a physically mixed MgO and Al2O3 support (5:5 ratio) and then subjected to a second heat treatment at a high temperature of 800°C. The ammonia decomposition efficiency reaction was carried out under the following conditions: -GHSV = 10,000 mL g cat -1 h -1 -Catalyst amount: 0.08g -Reaction temperature: 550℃, 500℃, 450℃, 400℃

[0049] After the ammonia dehydrogenation reaction, the unreacted ammonia was analyzed using a gas chromatograph under the following conditions, and the ammonia conversion rate was calculated based on the analysis results, which are shown in FIG. -GC-TCD -Carrier gas: Helium -Oven conditions: 40℃ → 20℃ / min → 120℃

[0050] It was found that when using an MgAl2O4 support as in the present invention, a better ammonia decomposition efficiency was recorded than with other supports. This is due to the superiority of the MgAl2O4 spinel structure generated using a hydrotalcite-structure precursor. In particular, it was confirmed that the ammonia decomposition efficiency was significantly improved compared to a catalyst that was subjected to a second heat treatment at a high temperature of 800°C after Ru metal was supported on a commonly used physical mixture of Al2O3 and MgO supports.

[0051] Experimental Example 5: TEM analysis of ruthenium-supported Ru / MgAl2O4 catalyst TEM analysis was performed to examine the ruthenium dispersion characteristics of Ru / MgAl2O4 loaded with 3 wt% ruthenium, and the results are shown in Figure 5. In this case, the support heat treatment (first heat treatment) temperature and second heat treatment temperature for the prepared catalyst were 800°C.

[0052] When ruthenium was supported on MgAlO as a support, FIG. 5a is a TEM image of the ammonia dehydrogenation catalyst according to one embodiment of the present invention, and FIG. 5b shows that the particle size distribution of ruthenium particles was in the range of 1 to 5 nm, with the average particle size measured being 2.54 nm.

[0053] Experimental Example 6: Confirmation of ammonia decomposition efficiency by ruthenium content To investigate the ammonia decomposition efficiency of MgAl2O4-based catalysts loaded with 0.1-3 wt% ruthenium, the ammonia conversion rate was measured under the following conditions, and the results are shown in Figure 6. The ammonia decomposition efficiency analysis of the catalyst was carried out under the same conditions as in Experimental Example 4.

[0054] As the ruthenium content decreases, the ammonia decomposition efficiency decreases, but even when a very small amount of ruthenium (0.1 wt%) is supported, excellent ammonia decomposition efficiency was recorded at 550°C.

[0055] Experimental Example 7: Confirmation of ammonia decomposition efficiency by changing the atmospheric conditions of the second heat treatment To investigate the difference in ammonia decomposition efficiency characteristics depending on the atmosphere used in the second heat treatment for the ruthenium-loaded MgAlO-based catalyst, the second heat treatment was carried out under hydrogen / nitrogen, nitrogen, and air atmospheres. The ammonia decomposition efficiency analysis of the catalysts synthesized under different atmospheres was carried out under the same conditions as in Experimental Example 4. The results are shown in Figure 7.

[0056] It was confirmed that the ammonia decomposition efficiency showed different trends depending on the atmospheric conditions of the second heat treatment, and the sample that underwent the second heat treatment in a reducing atmosphere (under a flow of hydrogen / nitrogen mixed gas) recorded the best ammonia decomposition efficiency.

[0057] Experimental Example 8: Confirmation of ammonia decomposition efficiency by changing the first heat treatment temperature during support synthesis To investigate the difference in ammonia decomposition efficiency characteristics depending on the temperature conditions of the support heat treatment (first heat treatment) for a ruthenium-loaded MgAl2O4-based catalyst, the first heat treatment temperature was varied from 600 to 900°C. Ammonia decomposition catalysts were synthesized using supports synthesized at different temperatures. The ammonia decomposition efficiency reaction was carried out under the following conditions. GHSV = 10,000-30,000 mL g cat -1 h -1 Catalyst amount: 0.08g Reaction temperature: 550℃, 500℃, 450℃, 400℃

[0058] After the ammonia dehydrogenation reaction, the unreacted ammonia was analyzed using a gas chromatograph under the following conditions, and the ammonia conversion rate was calculated based on the analysis results, which are shown in FIG. -GC-TCD -Carrier gas: Helium -Oven conditions: 40℃ → 20℃ / min → 120℃

[0059] The catalyst produced has a GHSV of 10,000-30,000 mL g cat -1 h -1 It was confirmed that the catalysts prepared using the support synthesized through the first heat treatment at 800°C showed excellent ammonia decomposition efficiency, and that the catalysts prepared using the support synthesized through the first heat treatment at 800°C showed the best catalytic activity.

[0060] Experimental Example 9: Confirmation of ammonia decomposition efficiency by changing the temperature conditions of the second heat treatment To investigate the difference in ammonia decomposition efficiency characteristics depending on the second heat treatment temperature in the ruthenium-loaded MgAl2O4-based catalyst, the second heat treatment temperature was changed from 600°C to 900°C, and the ammonia decomposition efficiency analysis was carried out under the same conditions as in Experimental Example 8, and the results are shown in Figure 9.

[0061] The catalyst produced has a GHSV of 10,000-30,000 mL g cat -1 h -1 It was confirmed that the catalyst exhibited excellent ammonia decomposition efficiency even after the second heat treatment at 800°C, and that the catalyst that underwent the second heat treatment at 800°C exhibited the best catalytic activity.

Claims

1. MgAl ２ O ４ comprising a spinel support and ruthenium; The catalyst for ammonia decomposition contains 0.1 to 5% by weight of the ruthenium based on the total weight of the catalyst.

2. 2. The ammonia decomposition catalyst according to claim 1, wherein the ruthenium has an average particle size of 2 to 5 nm.

3. A precursor mixture containing magnesium oxide and aluminum oxide having a hydrotalcite structure is heat-treated to obtain MgAl ２ O ４ a first heat treatment step to obtain a spinel support; preparing a mixture by mixing the spinel support with an aqueous ruthenium precursor solution; and a second heat treatment after drying the mixture.

4. 4. The method for producing a catalyst for ammonia decomposition according to claim 3, wherein the first heat treatment is carried out at 500 to 900° C. for 1 to 10 hours.

5. 4. The method for producing a catalyst for ammonia decomposition according to claim 3, wherein the second heat treatment is carried out at 600 to 1000° C. for 1 to 10 hours.

6. 4. The method for producing a catalyst for ammonia decomposition according to claim 3, wherein the second heat treatment is carried out in an atmosphere of at least one gas selected from the group consisting of hydrogen and nitrogen.

7. Using the catalyst for ammonia decomposition according to claim 1 or 2, a GHSV of 10,000 to 30,000 mL g at a reaction temperature of 300 to 700°C is obtained. ｃａｔ －１ h －１ 1. A method for decomposing ammonia, comprising treating ammonia under conditions.

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