Method for pretreating ammonia decomposition catalyst and method for regenerating same

Abstract

According to exemplary embodiments of the present invention, provided may be a method for pretreating an ammonia decomposition catalyst, capable of effectively reducing an active metal oxide contained in the catalyst, and a method for regenerating same.

Description

Ammonia decomposition catalyst pretreatment method and regeneration method thereof

[0001] The present invention relates to a method for pre-treating an ammonia decomposition catalyst and a method for regenerating an ammonia decomposition catalyst.

[0002] Catalysts are utilized in various industrial processes as they contribute to increasing the rate of chemical reactions. Since catalysts are initially manufactured in a high-temperature oxidizing atmosphere, they exist in the form of metal oxides. In hydrogen production processes such as steam methane reforming or ammonia cracking, ruthenium (Ru) or nickel (Ni) are generally used as the main components of the catalyst. However, because the unreduced metal oxide form exhibits low activity at low temperatures, a pretreatment process is required to reduce the catalyst to its metallic state before process operation. Furthermore, metals can be reoxidized by exposure to the atmosphere during prolonged reactions or shutdowns; upon restart, the catalyst must be reduced again using the aforementioned method to restore its original activity. Therefore, a catalyst reduction procedure is required even when restarting the process.

[0003] (Patent Document 1) Japanese Registered Patent Publication No. 7525731

[0004] The problem that the technical concept of the present invention aims to solve is to provide a pretreatment method for an ammonia decomposition catalyst capable of effectively reducing an active metal oxide contained in the catalyst, and a method for regenerating the same.

[0005] The problems of the present invention are not limited to those described above. A person skilled in the art to which the present invention pertains will have no difficulty understanding additional problems of the present invention from the overall details of the specification.

[0006] According to exemplary embodiments for solving the problem of the present invention, a method for pre-treating an ammonia decomposition catalyst is provided.

[0007] The above ammonia decomposition catalyst pretreatment method may include: a reduction step of reducing the active metal oxide of the ammonia decomposition catalyst in a gas atmosphere containing, in volume%, 51 to 90% ammonia and the remainder nitrogen, and in a temperature range of 500 to 900°C; and a cooling step of switching to a nitrogen atmosphere to cool the reduced ammonia decomposition catalyst to room temperature.

[0008] It may further include a heating step of heating to the target temperature of the above reduction step at an average heating rate of 1 to 10℃ / min.

[0009] The holding time of the above reduction step may be 0.5 to 5 hours.

[0010] The above cooling step can be performed in a gas atmosphere consisting of nitrogen.

[0011] The nitrogen atmosphere gas in the above cooling step may be the process tail gas recovered after hydrogen purification in the ammonia decomposition process.

[0012]

[0013] According to other exemplary embodiments, a method for regenerating an ammonia decomposition catalyst is provided. The method for regenerating an ammonia decomposition catalyst may include: a regeneration step of regenerating an ammonia decomposition catalyst exposed to ambient air after an ammonia decomposition reaction in a gas atmosphere containing 51 to 90% ammonia and the remainder nitrogen by volume%, and in a temperature range of 500 to 900°C; and a cooling step of cooling the ammonia decomposition catalyst to room temperature by switching to a nitrogen atmosphere.

[0014] The above regeneration step can be performed to satisfy the following relationship 1.

[0015] [Relationship 1]

[0016] 0.1 < log(D) / (T / 500) < 2.0

[0017] In the above equation 1, D represents the time (h) exposed to ambient air after the ammonia decomposition reaction, and T represents the temperature (°C) at the regeneration stage.

[0018] The nitrogen atmosphere gas in the above cooling step may be the process tail gas recovered after hydrogen purification in the ammonia decomposition process.

[0019] The method may further include a step of pre-reducing the ammonia decomposition catalyst by contacting the process tail gas recovered after hydrogen purification in the ammonia decomposition process with the ammonia decomposition catalyst exposed to ambient air after the ammonia decomposition reaction.

[0020] According to exemplary embodiments of the present invention, a method for pre-treating an ammonia decomposition catalyst capable of effectively reducing an active metal oxide contained in the catalyst and a method for regenerating the same can be provided.

[0021] The various and beneficial advantages and effects of the present invention are not limited to those described above and will be more easily understood in the process of explaining specific embodiments of the present invention.

[0022] Hereinafter, preferred embodiments of the present invention will be described in detail. Prior to this, terms and words used in this specification and claims should not be interpreted as being limited to their ordinary or dictionary meanings. Instead, based on the principle that the inventor may appropriately define the concepts of terms to best describe his invention, they should be interpreted in a meaning and concept consistent with the technical spirit of the present invention.

[0023] In the following embodiments, the terms first, second, etc. are used not in a limiting sense, but for the purpose of distinguishing one component from another component.

[0024] In the following embodiments, the singular expression includes the plural expression unless the context clearly indicates otherwise.

[0025] In the following embodiments, terms such as "include" or "have" mean that the features or components described in the specification are present, and do not preclude the possibility that one or more other features or components may be added.

[0026] Where an embodiment can be implemented differently, a specific process sequence may be performed differently from the order described. For example, two processes described consecutively may be performed substantially simultaneously or proceed in the reverse order of the description.

[0027] In addition, in describing the present invention, if it is determined that a detailed description of related known components or functions may obscure the essence of the invention, such detailed description is omitted.

[0028] The present invention will be described in detail below through each embodiment. It should be noted that each embodiment described in this specification is not limited to a single embodiment but may also be combined with other embodiments. Accordingly, the citation of claims in the patent claims is merely an example of an embodiment, and the technical concept of the present invention should not be interpreted as being limited only to a combination with the cited claims; rather, combinations with various claims are also included within the scope of the technical concept of the present invention.

[0029] The present invention will be described in detail below through examples. However, it should be noted that the following examples are intended merely to illustrate and embody the present invention and are not intended to limit the scope of the present invention. This is because the scope of the present invention is determined by the matters described in the patent claims and matters reasonably inferred therefrom.

[0030] [Ammonia Decomposition Catalyst Pretreatment Method]

[0031] According to exemplary embodiments, the ammonia decomposition catalyst pretreatment method includes a reduction step and a cooling step.

[0032] The reduction step may be a step of reducing the active metal oxide of the ammonia decomposition catalyst in a gas atmosphere containing, in volume percent, 51–90% ammonia and the remainder nitrogen, and in a temperature range of 500–800°C. The ammonia decomposition catalyst contains an active metal. Additionally, it may optionally include an active metal supported on a ceramic support or a carbon-based support to increase the contact area with the source gas and increase thermal stability. The active metal of this ammonia decomposition catalyst exists in the form of a metal oxide during initial manufacturing. Therefore, it is necessary to reduce this metal oxide to increase catalytic activity.

[0033] Conventionally, to create a reducing atmosphere, gases primarily containing hydrogen or carbon monoxide were used. However, hydrogen was economically unsuitable and presented problems regarding transportation and storage. Additionally, carbon monoxide had the problem of generating carbon dioxide by combining with oxygen during the reduction process of oxides. According to exemplary embodiments, a gas primarily containing ammonia is used as the reducing gas. Ammonia can decompose into hydrogen and nitrogen in a high-temperature environment. In particular, the active metal oxide, which is the target of reduction, and the reduced active metal can contribute as catalysts to the decomposition reaction of ammonia. In this way, a reducing atmosphere can be created by promoting the ammonia decomposition reaction to generate hydrogen. Therefore, according to exemplary embodiments, oxides of active metals can be reduced using ammonia, which is relatively inexpensive and easy to store and transport.

[0034] The ammonia decomposition reaction can follow the following reaction equation.

[0035] [Reaction Equation 1]

[0036] 2NH3→ N2+ 3H2

[0037] The reduction reaction of an active metal oxide may follow any one of the following reaction schemes.

[0038] [Reaction Equation 2]

[0039] MO + H2 → M + H2O

[0040] [Reaction Equation 3]

[0041] 3MO + 2NH3 → 3M + 3H2O + N2

[0042] In the above reaction schemes 2 and 3, M is the active metal of the ammonia decomposition catalyst. The type of M is not particularly limited as long as it is a metal that exhibits catalytic activity in the ammonia decomposition reaction, but as a non-limiting example, M may be any one of nickel (Ni), cobalt (Co), ruthenium (Ru), palladium (Pd), platinum (Pt), iron (Fe), molybdenum (Mo), and alloy elements thereof.

[0043] If the ammonia content in the atmosphere gas during the reduction step is low, a sufficient reducing atmosphere may not be created. Therefore, it is desirable for the ammonia content in the atmosphere gas to be higher. However, if the ammonia content in the atmosphere gas is excessively high, ammonia slip may occur, in which unreacted ammonia leaks into subsequent processes, and some ammonia may combine directly with oxygen in oxides to form nitrogen oxides. Therefore, the ammonia content is controlled to 51–90%. More preferably, in terms of creating a reducing atmosphere and preventing ammonia slip, the ammonia content may be 60–80%.

[0044] In addition, nitrogen may be included as a remainder. Nitrogen is a chemically stable gas that can minimize side reactions that may occur during the reduction process.

[0045] If the temperature of the reduction step is excessively low, the reduction of the active metal oxide may not be sufficiently achieved. Since the reduction reaction of the active metal is generally an endothermic reaction, a higher temperature during the reduction step may be preferable. However, if the temperature of the reduction step is excessively high, excessive energy may be consumed to create the temperature atmosphere. Therefore, the reduction step is performed in a temperature range of 500 to 900°C. In terms of creating a reducing atmosphere and energy efficiency, it is more preferable to perform it in a temperature range of 530 to 800°C.

[0046] According to exemplary embodiments, the holding time of the reduction step may be 0.5 to 5 hours. If the holding time of the reduction step is excessively short, the oxide of the active metal may not be sufficiently reduced. In this case, the efficiency of the subsequent ammonia decomposition process may also be reduced. If the holding time of the reduction step is excessively long, the process time may be excessively extended, and process efficiency may be reduced.

[0047] According to exemplary embodiments, a heating step may be further included, which involves heating to the target temperature of the reduction step at an average heating rate of 1 to 10°C / min. If the average heating rate is less than 1°C / min, an excessive amount of time may be consumed to establish the reduction atmosphere. If the average heating rate is 10°C / min or higher, temperature deviations may occur, which may result in uneven reduction of the active metal oxide and structural damage to the catalyst pellets in the reactor.

[0048] According to exemplary embodiments, the composition of the atmosphere gas in the heating step may be substantially the same as the composition of the atmosphere gas in the reduction step. As a result, oxides of some active metals can be reduced even in the heating step, thereby increasing the reduction efficiency.

[0049] The cooling step may involve switching to a nitrogen atmosphere to cool the reduced ammonia decomposition catalyst to room temperature. If a gas primarily containing ammonia is continuously supplied during the cooling process, ammonia may remain undigested into hydrogen and nitrogen, potentially causing ammonia slip. Additionally, the reduction of the active metal is performed at high temperatures. In this case, if the ammonia decomposition catalyst is cooled in the atmosphere after the reduction is complete, uncontrolled reoxidation of the active metal may occur unevenly, potentially causing the surface of the catalyst to become non-uniform. Consequently, the efficiency of the ammonia decomposition catalyst may decrease. Therefore, switching to a relatively stable nitrogen atmosphere can prevent reoxidation or ammonia slip that may occur during the cooling process.

[0050] The atmosphere gas of the cooling step is not particularly limited as long as it mainly contains nitrogen. More specifically, if the atmosphere gas of the cooling step contains more than 50% nitrogen by volume, the remaining gas components are not particularly limited. According to exemplary embodiments, the cooling step may be performed in a gas atmosphere consisting of nitrogen. However, for the purpose of preventing reoxidation of the active metal, the atmosphere gas of the cooling step may not substantially contain oxygen.

[0051] According to exemplary embodiments, the nitrogen atmosphere gas in the cooling step may be the process tail gas recovered after hydrogen purification in the ammonia decomposition process. According to exemplary embodiments, the ammonia decomposition catalyst pretreated may be supplied to the ammonia decomposition process to produce hydrogen. The reaction gas generated in the ammonia decomposition process may contain hydrogen, nitrogen, and undissolved ammonia. Subsequently, to increase the purity of the ammonia hydrogen, hydrogen may be purified from the reaction gas to obtain high-purity hydrogen gas and a process tail gas containing nitrogen, undissolved ammonia, and unseparated hydrogen. At this time, the method of purifying hydrogen is not particularly limited, but may be any one of membrane separation, pressure swing adsorption, temperature swing adsorption, vacuum swing adsorption, pressure-vacuum swing adsorption, temperature-vacuum swing adsorption, and a combination thereof.

[0052] As such, the process tail gas may contain a high content of nitrogen, undecomposed ammonia capable of creating a reducing atmosphere, and undecomposed hydrogen. The composition of the process tail gas may be determined according to the ammonia conversion rate and hydrogen purification efficiency of the ammonia decomposition process, but as a non-limiting example, it may contain 90 to 100% nitrogen, 10% or less (including 0%) of undecomposed ammonia, and 5% or less (including 0%) of undecomposed hydrogen in volume%. By creating a cooling atmosphere using such a process tail gas, the reoxidation of the ammonia decomposition catalyst can be effectively prevented.

[0053] [Ammonia Decomposition Catalyst Regeneration Method]

[0054] According to exemplary embodiments, a method for regenerating an ammonia decomposition catalyst comprises a regeneration step and a cooling step. After the ammonia decomposition process is completed, the active metal may be reoxidized during the storage of the ammonia decomposition catalyst. The reoxidized ammonia decomposition catalyst may have relatively low catalytic activity. Consequently, if the reoxidized ammonia decomposition catalyst is introduced directly into the ammonia decomposition process, hydrogen production efficiency may be reduced, and an excessive load may occur in the hydrogen purification process. Therefore, to reuse the ammonia decomposition catalyst after the ammonia decomposition reaction process, it is necessary to regenerate the ammonia decomposition catalyst that has been stored in an atmospheric environment.

[0055] The regeneration step involves regenerating the ammonia decomposition catalyst, which has been exposed to ambient air after the ammonia decomposition reaction, in a gas atmosphere containing 51–90% ammonia and the remainder nitrogen, and in a temperature range of 500–900°C. In this way, the ammonia decomposition efficiency can be improved by reducing the active metal that has been oxidized by ambient air during storage. Furthermore, since it does not utilize conventional highly reducing gases such as hydrogen or carbon monoxide, it is possible to provide an environmentally friendly method for regenerating an ammonia decomposition catalyst that is highly resource-efficient.

[0056] If the ammonia decomposition catalyst is exposed to ambient air after the ammonia decomposition reaction is terminated, it may be the ammonia decomposition catalyst exposed to ambient air without limitation. The time of exposure to the atmosphere may refer to the elapsed time from the termination of ammonia decomposition until the time when the ammonia decomposition catalyst that participated in the ammonia decomposition reaction is reloaded into the ammonia decomposition reactor. Alternatively, it may refer to the elapsed time from the termination of ammonia decomposition until the regeneration step according to exemplary embodiments is performed on the catalyst used. As a non-limiting example, the time the ammonia decomposition catalyst is exposed to an ambient air atmosphere after the termination of the ammonia decomposition reaction may be 1 to 50 hours.

[0057] If the ammonia content in the atmosphere gas during the regeneration stage is excessively low, regeneration efficiency may decrease. If the ammonia content in the atmosphere gas during the regeneration stage is excessively high, ammonia slip may occur, and there is a possibility of nitrogen oxides being generated.

[0058] In addition, it may contain nitrogen as a remainder. As a result, side reactions that may occur during the regeneration process can be minimized.

[0059] If the temperature of the regeneration step is excessively low, the regeneration of the active metal may not be sufficiently achieved. To ensure that the active metal oxide is sufficiently reduced in an ammonia environment, it is better for the temperature of the regeneration step to be higher. However, if the temperature of the regeneration step is excessively high, excessive energy may be consumed to create the temperature atmosphere. Therefore, the regeneration step is performed in a temperature range of 500 to 900°C. In terms of creating a reducing atmosphere and energy efficiency, it is more preferably performed in a temperature range of 530 to 800°C.

[0060] According to exemplary embodiments, the regeneration step can be performed to satisfy the following relationship 1.

[0061] [Relationship 1]

[0062] 0.1 < log(D) / (T / 500) < 2.0

[0063] In the above equation 1, D represents the time (h) exposed to ambient air after the ammonia decomposition reaction, and T represents the temperature (°C) at the regeneration stage.

[0064] After the ammonia decomposition reaction is completed, the longer the time the catalyst is left in ambient air, the greater the degree of oxidation of the active metal may become. Therefore, it is necessary to control the temperature of the regeneration step according to the time of exposure to ambient air after the ammonia decomposition reaction. According to exemplary embodiments, the regeneration efficiency of the ammonia decomposition catalyst can be further enhanced by controlling the temperature conditions of the regeneration step to satisfy Equation 1. In addition, by controlling to satisfy Equation 1, an ammonia decomposition catalyst having a higher ammonia decomposition efficiency than an ammonia decomposition catalyst regenerated using pure hydrogen can be provided.

[0065] According to exemplary embodiments, the holding time of the regeneration step may be 0.5 to 5 hours. If the holding time of the regeneration step is excessively short, the oxide of the active metal may not be sufficiently reduced. If the holding time of the regeneration step is excessively long, the process time may be excessively increased, and process efficiency may be reduced.

[0066] According to exemplary embodiments, a heating step may be further included, which heats to the target temperature of the regeneration step at an average heating rate of 1 to 10°C / min. If the average heating rate is less than 1°C / min, an excessive amount of time may be consumed to create a reducing atmosphere for the regeneration step. If the average heating rate is 10°C / min or more, temperature deviations may occur, causing the regeneration of the active metal to become uneven.

[0067] According to exemplary embodiments, the composition of the atmosphere gas in the heating step may be substantially the same as the composition of the atmosphere gas in the regeneration step. As a result, oxides of some active metals can be reduced even in the heating step, thereby increasing regeneration efficiency.

[0068] The cooling step may involve switching to a nitrogen atmosphere to cool the reduced ammonia decomposition catalyst to room temperature. This prevents additional oxidation that may occur during the cooling process.

[0069] The atmosphere gas of the cooling step is not particularly limited as long as it mainly contains nitrogen. More specifically, if the atmosphere gas of the cooling step contains more than 50% nitrogen by volume, the remaining gas components are not particularly limited. According to exemplary embodiments, the cooling step may be performed in a gas atmosphere consisting of nitrogen. However, for the purpose of preventing reoxidation of the active metal, the atmosphere gas of the cooling step may not substantially contain oxygen.

[0070] According to exemplary embodiments, the nitrogen atmosphere gas in the cooling step may be the process tail gas recovered after hydrogen purification in the ammonia decomposition process. Since the process tail gas contains an excess amount of nitrogen, it can form the nitrogen atmosphere in the cooling step. Additionally, undecomposed ammonia contained in the process tail gas can be further decomposed by the catalytic action of the active metal reduced through the regeneration process. As a result, hydrogen production efficiency can be increased.

[0071] The composition of the process tail gas can be determined according to the ammonia conversion rate of the ammonia decomposition process and the hydrogen purification efficiency, but as a non-limiting example, it may include 90 to 100% nitrogen, 10% or less of undecomposed ammonia, and 5% or less of unseparated hydrogen in volume%.

[0072] According to exemplary embodiments, the ammonia decomposition catalyst regeneration method may further include a step of pre-reducing the ammonia decomposition catalyst by contacting the ammonia decomposition catalyst, which has been exposed to ambient air after the ammonia decomposition reaction, with the process tail gas recovered after hydrogen purification in the ammonia decomposition process. This prevents further oxidation and stabilizes the surface of the used ammonia decomposition catalyst, thereby increasing the efficiency of the subsequent regeneration step.

[0073] Furthermore, regarding matters that overlap with the ammonia decomposition catalyst pretreatment method, they are equally applicable to this ammonia decomposition catalyst regeneration method, so a detailed explanation is omitted.

[0074] [Test Example]

[0075] Test Example 1: Verification of the efficiency of the ammonia decomposition catalyst pretreatment method

[0076] (Example 1)

[0077] A catalyst with ruthenium (Ru) as the active metal was prepared, and the reduction of the catalyst was carried out at approximately 650°C using a gas containing 75% ammonia and the remainder nitrogen. At this time, the average heating rate to reach 650°C was controlled to 5°C / min, and the temperature was maintained for 1 hour after reaching the target temperature.

[0078] Subsequently, the reduced ammonia decomposition catalyst was converted into a gas consisting of pure nitrogen and cooled to room temperature.

[0079] (Example 2)

[0080] The catalyst was pretreated in the same manner as in Example 1, except that a catalyst with nickel (Ni) as the active metal was prepared.

[0081] (Comparative Example 1)

[0082] The catalyst was pretreated in the same manner as in Example 1, except that a gas containing 75% hydrogen and the remainder nitrogen was used as the reducing gas.

[0083] (Comparative Example 2)

[0084] The catalyst was pretreated in the same manner as in Example 2, except that a gas containing 75% hydrogen and the remainder nitrogen was used as the reducing gas.

[0085] Ammonia decomposition experiments were conducted for each pretreated catalyst under conditions of approximately 450°C and 500°C. At this time, the space velocity (GHSV) of ammonia was 10,000 mL·g cat -1 ·h-1 The pressure was controlled to 8 barg. Subsequently, the ammonia decomposition efficiency was measured and is shown in Table 1 below. The ammonia decomposition efficiency is the difference in the amount of ammonia before and after the reaction relative to the amount of ammonia supplied.

[0086] Classification Ammonia Decomposition Efficiency (%) Example 1 Comparative Example 1 Example 2 Comparative Example 2 450℃ 88.2 82.5 31.5 24.7 500℃ 97.6 97.0 54.0 38.2

[0087] Referring to Table 1, the examples in which reduction pretreatment was performed using ammonia showed superior decomposition efficiency compared to the comparative examples in which reduction pretreatment was performed using expensive hydrogen gas.

[0088]

[0089] Test Example 2: Verification of the efficiency of the ammonia decomposition catalyst regeneration method

[0090] (Example 3)

[0091] After the ammonia decomposition reaction according to Test Example 1 was completed, the catalyst according to Example 1 was recovered and exposed to ambient air at room temperature for 48 hours. Subsequently, the ammonia decomposition catalyst was regenerated at approximately 650°C using a gas containing 75% ammonia and the remainder nitrogen. At this time, the average heating rate to reach 650°C was controlled to 5°C / min, and the temperature was maintained for 1 hour after reaching the target temperature. The conditions of each regeneration step satisfy Equation 1.

[0092] Subsequently, the ammonia decomposition catalyst, which was regenerated by converting it into a gas consisting of pure nitrogen, was cooled to room temperature.

[0093] (Example 4)

[0094] Except for recovering the catalyst according to Example 2 and conducting the test, the test was conducted in the same manner as Example 3.

[0095] Ammonia decomposition experiments were conducted on each regenerated catalyst under conditions of approximately 450°C and 500°C. At this time, the space velocity (GHSV) of ammonia was 10,000 mL·g cat -1 ·h -1 The pressure was controlled to 8 barg. Subsequently, the ammonia decomposition efficiency was measured and is shown in Table 2 below.

[0096] Classification Example 3 Example 4 Ammonia Decomposition Efficiency (%) Relationship Formula 1 Ammonia Decomposition Efficiency (%) Relationship Formula 1 450℃ 88.4 1.29 24.5 1.29 500℃ 97.6 1.29 45.0 1.29

[0097] Referring to Table 2, the ammonia decomposition catalysts regenerated according to the exemplary examples exhibited ammonia decomposition efficiency equivalent to that before regeneration. In particular, Example 3 showed a higher level of efficiency than the ammonia decomposition efficiency before regeneration at a relatively low temperature (about 450°C).

[0098] Although the invention has been described with reference to the above embodiments, those skilled in the art will understand that various modifications and changes can be made to the invention without departing from the spirit and scope of the invention as described in the following claims.

Claims

A reduction step for reducing an active metal oxide of an ammonia decomposition catalyst in a gas atmosphere containing, in volume %, 51–90% ammonia and the remainder nitrogen, and in a temperature range of 500–900°C; and A method for pretreating an ammonia decomposition catalyst, comprising a cooling step of cooling the reduced ammonia decomposition catalyst to room temperature by switching to a nitrogen atmosphere. In paragraph 1, A method for pre-treating an ammonia decomposition catalyst, further comprising a heating step of heating to the target temperature of the above reduction step at an average heating rate of 1 to 10℃ / min. In paragraph 1, A method for pre-treating an ammonia decomposition catalyst, wherein the holding time of the above reduction step is 0.5 to 5 hours. In paragraph 1, The above cooling step is a method for pre-treating an ammonia decomposition catalyst in a gas atmosphere consisting of nitrogen. In paragraph 1, The nitrogen atmosphere gas in the above cooling step is a process tail gas recovered after hydrogen purification in an ammonia decomposition process, which is a method for pre-treating an ammonia decomposition catalyst. A regeneration step of regenerating the ammonia decomposition catalyst exposed to ambient air after the ammonia decomposition reaction in a gas atmosphere containing 51–90% ammonia and the remainder nitrogen by volume, and in a temperature range of 500–900°C; and A method for regenerating an ammonia decomposition catalyst comprising a cooling step of cooling the ammonia decomposition catalyst to room temperature by switching to a nitrogen atmosphere. In paragraph 6, A method for regenerating an ammonia decomposition catalyst, wherein the above regeneration step is performed to satisfy the following relationship 1. [Relationship 1] 0.1 < log(D) / (T / 500) < 2.0 (In the above Equation 1, D represents the time (h) exposed to ambient air after the ammonia decomposition reaction, and T represents the temperature (°C) during the regeneration stage.) In paragraph 6, The nitrogen atmosphere gas in the above cooling step is a process tail gas recovered after hydrogen purification in an ammonia decomposition process, a method for regenerating an ammonia decomposition catalyst. In paragraph 6, A method for regenerating an ammonia decomposition catalyst, further comprising the step of pre-reducing the ammonia decomposition catalyst by contacting the process tail gas recovered after hydrogen purification in an ammonia decomposition process with the ammonia decomposition catalyst exposed to ambient air after the ammonia decomposition reaction.