Ammonia decomposition catalyst and ammonia decomposition method

Abstract

The present invention relates to an ammonia decomposition catalyst and an ammonia decomposition method.

Description

[Technical Field]

[0001] [Cross-reference to related applications] This application claims the benefit of priority based on Korean Patent Application No. 10-2023-0018962 filed February 13, 2023, and Korean Patent Application No. 10-2023-0096826 filed July 25, 2023, and all contents disclosed in the documents of said Korean patent application are incorporated herein by reference.

[0002] The present invention relates to an ammonia decomposition catalyst and an ammonia decomposition method. [Background technology]

[0003] Recently, as interest in the environment and energy has increased, the issue of the hydrogen economy has also come to the fore.

[0004] The hydrogen economy refers to an economic and industrial structure that uses hydrogen as its primary energy source. In other words, it is an economic system that deviates from the current fossil fuel-centered energy system by increasing the number of power generation systems, heat production systems, automobiles, and other machinery that use hydrogen as an energy source, and to this end, creates new industries and markets in all fields necessary for the stable production, storage, and transportation of hydrogen.

[0005] In such systems, hydrogen can be produced through a variety of means, such as water electrolysis, natural gas reforming, and biomass gasification, and can be distributed through a pipeline network or transported to hydrogen fuel cells. However, because transporting hydrogen directly is expensive and dangerous, there is growing interest in technologies that allow hydrogen to be transported easily and safely at low cost.

[0006] One method for efficiently storing and transporting hydrogen is to transport ammonia and decompose the transported ammonia to use as a hydrogen source.

[0007] The reaction of decomposing ammonia into hydrogen and nitrogen is an endothermic reaction with a large energy difference, and the activation energy of the reaction is also very large. Therefore, a lot of energy is required to obtain a useful amount of hydrogen gas as a product, which results in a large expenditure of money in producing hydrogen.

[0008] This has led to growing interest in research into ammonia decomposition catalysts with high ammonia decomposition efficiency. Summary of the Invention [Problem to be solved by the invention]

[0009] The present specification aims to provide an ammonia decomposition catalyst with high ammonia decomposition efficiency.

[0010] The present specification also provides an ammonia decomposition method using such an ammonia decomposition catalyst. [Means for solving the problem]

[0011] The present specification provides an ammonia decomposition catalyst comprising a support and a catalytically active component supported on the support, the catalytically active component comprising: i) ruthenium (Ru) as a first metal; ii) lanthanum (La) as a second metal; and iii) any one or more of aluminum (Al) and cerium (Ce) as a third metal; and the catalyst has a porosity of 25% or more.

[0012] According to one example, the ammonia decomposition catalyst may have a porosity of about 20% or more, or about 30% or more, and at the same time, about 50% or less, or about 45% or less.

[0013] For example, the median pore size of the ammonia decomposition catalyst may be about 50 to about 150 μm. More specifically, the median pore size of the ammonia decomposition catalyst may be about 50 μm or more, or about 70 μm or more, or about 80 μm or more, or about 100 μm or more, or about 110 μm or more, and may be about 150 μm or less, or about 140 μm or less, or about 130 μm or less.

[0014] According to one example, the support may be an inorganic oxide structure, and more specifically, the inorganic oxide may be an inorganic oxide containing one or more elements selected from the group consisting of silicon, zirconium, aluminum, and cerium.

[0015] According to one example, the first metal may be contained in an amount of about 0.01 to about 0.5 parts by weight, or about 0.001 part by weight or more, or about 0.05 part by weight or more, or about 0.1 part by weight or more, relative to 100 parts by weight of the total of the support and the catalytically active component, and may be contained in an amount of about 0.5 part by weight or less, or about 0.4 part by weight or less, or about 0.35 part by weight or less, or about 0.3 part by weight or less.

[0016] According to one example, the catalytically active component may be about 20 parts by weight or less, or about 0.1 parts by weight or more, or about 0.5 parts by weight or more, or about 1 part by weight or more, relative to 100 parts by weight of the total of the support and the catalytically active component, and may also be about 20 parts by weight or less, less than about 18 parts by weight, or about 15 parts by weight or less, or about 12 parts by weight or less.

[0017] In one example, the weight ratio of (second metal):(third metal) may be about 1:99 to about 3:7, or about 1:99 or more, or about 2:98 or more, or about 3:97 or more, and at the same time about 3:7 or less, or about 25:75 or less.

[0018] According to one example, the first metal may be contained in an amount of about 0.1 to about 10 wt %, or about 0.1 wt % or more, or about 0.5 wt % or more, or about 1.0 wt % or more, or about 1.5 wt % or more, based on the total weight of the catalytically active component, and may be contained in an amount of about 10 wt % or less, or about 7 wt % or less, or about 5 wt % or less, or about 3 wt % or less.

[0019] According to one example, the ammonia decomposition catalyst may be in the shape of a hollow cylinder.

[0020] In one example, the diameter of the cross-sectional circle of the hollow cylinder may be about 1 to about 10 mm, or about 1 mm or more, 2 mm or more, or about 3 mm or more, or about 4 mm or more, and may be about 10 mm or less, or about 8 mm or less, or about 7 mm or less, or about 6 mm or less.

[0021] According to one example, the diameter of the hollow may be 0.1 to 0.5 of the diameter of the circular cross section of the cylinder.

[0022] According to one example, the support may have a structure including a substrate containing alumina and a silica layer formed on the alumina, and the catalytically active component is contained in the catalyst layer formed on the silica layer.

[0023] The present specification also provides a method for decomposing ammonia, in which an ammonia decomposition reaction is carried out in the presence of any one of the ammonia decomposition catalysts described above.

[0024] In one example, the ammonia decomposition method may be carried out at a temperature of about 400 to about 550°C, or at least about 400°C, or above about 400°C, or at least about 420°C, and at a temperature of about 600°C or less, or about 550°C or less, or about 530°C or less.

[0025] In the present invention, terms such as first and second are used to describe various components, and the terms are used only to distinguish one component from another.

[0026] Furthermore, the terms used in this specification are merely used to describe exemplary embodiments and are not intended to limit the present invention.

[0027] Unless otherwise clearly indicated in the context, singular expressions include plural expressions.

[0028] As used herein, terms such as "comprises," "comprises," or "having" are intended to describe embodied features, numbers, steps, components, or combinations thereof, but do not exclude the possibility of one or more other features, numbers, steps, components, combinations thereof, or additional features.

[0029] Furthermore, in this specification, when a layer or element is referred to as being formed "on" or "on" another layer or element, it means that the layer or element is formed directly on the other layer or element, or that other layers or elements can be additionally formed between the layers, on the object, or on the substrate.

[0030] Since the present invention can be modified in various ways and can have various forms, specific embodiments will be illustrated and described in detail below, but it should be understood that this is not to limit the invention to the particular disclosed form, but to include all modifications, equivalents, and alternatives within the spirit and technical scope of the invention.

[0031] In addition, in this specification, a hollow cylinder means a cylindrical shape having a smaller cylindrical hole passing through the circular center of the cylinder, and the circle, cylinder, etc. mentioned here do not necessarily mean only mathematically strict shapes.

[0032] FIG. 1 is a schematic diagram showing the shape of a hollow cylinder of a catalyst according to an example of the present invention.

[0033] Referring to Figure 1, the shape of the hollow cylinder can be seen.

[0034] According to one aspect of the present invention, there is provided an ammonia decomposition catalyst comprising: a support; and a catalytically active component supported on the support, the catalytically active component comprising: i) ruthenium (Ru) as a first metal; and ii) lanthanum (La) as a second metal; and iii) any one or more of aluminum (Al) and cerium (Ce) as a third metal; and the catalyst has a porosity of 25% or more.

[0035] The inventors of the present invention discovered that when a catalyst having specific pore characteristics is prepared by supporting a catalytically active component on a carrier of a specific form, such a catalyst can achieve very high efficiency as an ammonia decomposition catalyst, and thus completed the present invention.

[0036] The ammonia decomposition reaction can be expressed by the following reaction formula:

[0037] [ka]

[0038] This reaction is a reversible process, and three molecules of hydrogen gas can be obtained from two molecules of ammonia. Generally, when the reaction proceeds under high temperature and pressure conditions in the presence of a catalyst, the forward reaction becomes dominant, and all ammonia is decomposed, leaving only a trace amount of undecomposed ammonia.

[0039] However, this forward reaction is an endothermic reaction with a large difference in the energy produced between the product and the reactant, and the activation energy of the reaction is also very high, so the reaction efficiency is low and a large amount of energy must be input.

[0040] Thus, one embodiment of the present invention uses an ammonia decomposition catalyst comprising a support and a catalytically active component supported on the support, the catalytically active component comprising: i) ruthenium (Ru) as a first metal; ii) lanthanum (La) as a second metal; and iii) one or more of aluminum (Al) and cerium (Ce) as a third metal; and the catalyst has a porosity of 25% or more.

[0041] Ruthenium, lanthanum, aluminum, cerium, etc. can be used as catalytically active components in the form of composite metal oxides. Here, composite metal oxide refers to a compound or mixture in which two or more of the metal elements mentioned as catalytically active components are mixed together with the same or different oxidation states.

[0042] Among these catalytically active components, the metal that directly mediates the reaction is known as ruthenium, while lanthanum, aluminum, and cerium can act as promoters.

[0043] In addition, the ammonia decomposition catalyst according to one aspect of the present invention is porous, having a porosity of 25% or more. The use of a porous catalyst not only increases the surface area of ​​the catalytically active material that can come into contact with the reactants, but also prevents thermal agglomeration of the catalytically active material, thereby improving the catalyst's lifespan.

[0044] According to one example, the ammonia decomposition catalyst may have a porosity of about 20% or more, or about 30% or more, and at the same time, about 50% or less, or about 45% or less.

[0045] If the porosity is too low, the reactant, i.e., ammonia, may not be able to contact the catalytically active components present inside the catalyst structure, resulting in a decrease in the efficiency of the ammonia decomposition reaction. If the porosity is too high, the strength of the catalyst may be reduced, resulting in a decrease in physical properties.

[0046] For example, the median pore size of the ammonia decomposition catalyst may be about 50 to about 150 μm. More specifically, the median pore size of the ammonia decomposition catalyst may be about 50 μm or more, or about 70 μm or more, or about 80 μm or more, or about 100 μm or more, or about 110 μm or more, and may be about 150 μm or less, or about 140 μm or less, or about 130 μm or less.

[0047] If the median pore size is too small, the reactants may not flow smoothly within the catalyst, causing a pressure difference at the ammonia inlet, which may result in a decrease in reaction efficiency.If the median pore size is too large, the specific surface area of ​​the catalyst may decrease, which may result in a decrease in the contact area between the reactants and the catalyst, which may also result in a decrease in reaction efficiency.

[0048] In addition, within the above range, the amount of the noble metal ruthenium supported can be minimized, while increasing the efficiency of the ammonia decomposition reaction and improving the catalyst life.

[0049] According to one example, the support may be an inorganic oxide structure, and more specifically, the inorganic oxide may be an inorganic oxide containing one or more elements selected from the group consisting of silicon, zirconium, aluminum, and cerium.

[0050] According to one example, the first metal may be contained in an amount of about 0.01 to about 0.5 parts by weight, or about 0.01 part by weight or more, or about 0.05 part by weight or more, or about 0.1 part by weight or more, relative to 100 parts by weight of the total of the support and the catalytically active component, and may also be contained in an amount of about 0.5 part by weight or less, or about 0.4 part by weight or less, or about 0.35 part by weight or less, or about 0.3 part by weight or less.

[0051] If the content of the first metal is too low, the efficiency of the ammonia decomposition reaction may decrease. If the content of the first metal is too high, the pores of the porous catalyst structure may be closed during the process of increasing the coating amount to increase the content of the first metal, preventing smooth flow of reactants within the catalyst and generating a pressure difference at the ammonia inlet, which may result in a decrease in reaction efficiency and an increase in costs.

[0052] In one example, the content of the catalytically active components, i.e., the total amount of the first metal, the second metal, and the third metal, may be about 20 parts by weight or less, or about 0.1 parts by weight or more, or about 0.5 parts by weight or more, or about 1 part by weight or more, relative to 100 parts by weight of the total of the support and the catalytically active components, and may also be about 20 parts by weight or less, less than about 18 parts by weight, or about 15 parts by weight or less, or about 12 parts by weight or less.

[0053] If the content of catalytically active components is too low, the number of reaction active sites for the ammonia decomposition reaction will decrease, which may result in a problem of reduced ammonia decomposition reaction efficiency. On the other hand, if the content of catalytically active components is too high, the pores of the porous catalyst structure will be closed, preventing smooth flow of reactants within the catalyst, which may result in a pressure difference at the ammonia inlet, which may result in a problem of reduced reaction efficiency.

[0054] In one example, the weight ratio of (second metal):(third metal) may be about 1:99 to about 3:7, or about 1:99 or more, or about 2:98 or more, or about 3:97 or more, and at the same time about 3:7 or less, or about 25:75 or less.

[0055] As mentioned above, among the catalytically active components, the metal that directly mediates the ammonia decomposition reaction is known to be ruthenium, and lanthanum, aluminum, and cerium can also act as promoters.

[0056] Ruthenium, which directly mediates the ammonia decomposition reaction, is attached to the acid sites on the surface of the inorganic oxide support. Therefore, in order for ruthenium to be dispersed uniformly on the surface of the support, the acid sites must be uniformly distributed on the surface of the inorganic oxide support.

[0057] However, inorganic oxide structures used as supports are often heat-treated at high temperatures of approximately 900°C or higher to ensure strength. This heat treatment process eliminates acid sites on the surface of the inorganic oxide structure. Therefore, if ruthenium is directly supported on a typical support, the ruthenium will not be uniformly dispersed on the surface of the inorganic oxide structure but will be supported in the form of large particles, reducing the surface area of ​​ruthenium on the catalyst surface and reducing the efficiency of the ammonia decomposition reaction.

[0058] In the composite metal oxide containing the third metal, the acid sites of the third metal are uniformly distributed on the surface, allowing ruthenium to be supported in a uniformly dispersed form, thereby increasing the surface area of ​​ruthenium on the catalyst surface.

[0059] The second metal can exist in a stable state within the oxide crystal lattice of the third metal and can play a role in facilitating nitrogen-nitrogen recombination during the ammonia decomposition reaction. In addition, the second metal isolates the reactive active sites formed by ruthenium bound to the acid sites of the third metal, preventing the aggregation of adjacent ruthenium during the ammonia decomposition reaction, thereby extending the catalyst life.

[0060] From this perspective, it may be preferable to maintain the weight ratio of the second metal and the third metal within the aforementioned range.

[0061] According to one example, the first metal may be contained in an amount of about 0.1 to about 10 wt %, or about 0.1 wt % or more, or about 0.5 wt % or more, or about 1.0 wt % or more, or about 1.5 wt % or more, based on the total weight of the catalytically active component, and may be contained in an amount of about 10 wt % or less, or about 7 wt % or less, or about 5 wt % or less, or about 3 wt % or less.

[0062] According to one embodiment of the invention, the catalytically active component is in the form of a composite metal oxide containing a first metal, a second metal, and a third metal, and the molar ratio of the first metal in the composite metal oxide may be about 0.1 to about 10, or about 1 to about 5, or about 2 to about 5; the molar ratio of the second metal may be about 0.1 to about 20, or about 0.5 to about 15, or about 1 to about 10; and the molar ratio of the third metal may be about 0.1 to about 35, or about 1 to about 30, or about 3 to about 25.

[0063] According to one example, the ammonia decomposition catalyst may be in the shape of a hollow cylinder.

[0064] A hollow cylinder refers to a cylindrical shape having a smaller cylindrical hole passing through the circular center of the cylinder, and the circle, cylinder, etc. mentioned here do not necessarily refer only to mathematically strict shapes.

[0065] FIG. 1 is a schematic diagram showing the shape of a hollow cylinder of a catalyst according to an example of the present invention.

[0066] Referring to Figure 1, the shape of the hollow cylinder can be seen.

[0067] In one example, the diameter of the cross-sectional circle of the hollow cylinder may be about 1 to about 10 mm, or about 1 mm or more, 2 mm or more, or about 3 mm or more, or about 4 mm or more, and may be about 10 mm or less, or about 8 mm or less, or about 7 mm or less, or about 6 mm or less.

[0068] If the cross-sectional diameter of the hollow cylinder is too large, the catalyst packing density will be low, and the reactant ammonia gas will pass through without making sufficient contact with the catalyst, which may result in a decrease in reaction efficiency. If the cross-sectional diameter of the hollow cylinder is too small, the catalyst packing density will be too high, which may result in a pressure difference, which may result in a decrease in reaction efficiency.

[0069] According to one example, the diameter of the hollow space within the hollow cylinder, i.e., the central hole that crosses the cylinder, may be 0.1 to 0.5 of the diameter of the circular cross section of the cylinder.

[0070] If the diameter of the central pore is too large, the volume of the catalyst structure increases relatively, and the amount of catalytically active component introduced into the reactor decreases relatively, which may result in a decrease in the mechanical strength of the catalyst structure. If the diameter of the central pore is too small, a pressure difference may occur, which may result in a decrease in reaction efficiency, or a localized cold spot may occur in the ammonia decomposition reaction, which is an endothermic reaction, which may result in a decrease in reaction efficiency.

[0071] According to one example, the catalyst may have a structure in which the support includes a substrate containing alumina and a silica layer formed on the alumina, and the catalytically active component is included in a catalyst layer formed on the silica layer.

[0072] In the case of the above structure, the catalytically active component is uniformly coated not only on the surface of the carrier but also in the internal pores, thereby increasing the dispersion of the catalyst and enabling high activity in the reaction even when only a small amount of the catalytically active component is used.

[0073] On the other hand, the above catalyst can be produced by the following method.

[0074] First, an aqueous solution of a ruthenium salt is prepared. Examples of the aqueous solution of the ruthenium salt include an aqueous solution of ruthenium fluoride, an aqueous solution of ruthenium chloride, an aqueous solution of ruthenium nitrate, an aqueous solution of ruthenium sulfate, and an aqueous solution of perruthenate ions.

[0075] Then, La-ceria powder or La-alumina powder is added to this, and basic conditions are created using ammonia water, etc. This is then filtered and washed, and dried in an oven at about 100 to about 150°C for about 6 to about 20 hours to obtain a powder.

[0076] The powder thus obtained is placed in distilled water, and zirconia balls are added and the mixture is stirred with a roller to produce a slurry.

[0077] After immersing the support in the slurry solution, any remaining filtrate is removed using an air gun, and the support is dried in an oven at about 100 to about 150°C for about 6 to about 20 hours. The weight is measured to confirm the amount of coated catalytically active component, and the slurry solution coating process is repeated three more times to obtain a supported catalyst in which the aforementioned first, second, and third metals are supported on the support.

[0078] Meanwhile, the supported catalyst prepared by the above method can be used as an ammonia decomposition catalyst as it is, or can be used as an ammonia decomposition catalyst after calcining or reducing it.

[0079] During calcination and reduction, the catalyst obtained above may be treated with hydrogen gas at a temperature of about 300 to about 400°C, and calcination and reduction conditions generally used in the technical field to which the present invention pertains may be adopted.

[0080] The present specification also provides a method for decomposing ammonia, in which an ammonia decomposition reaction is carried out in the presence of any one of the ammonia decomposition catalysts described above.

[0081] In the ammonia decomposition method according to one example of the present invention, in addition to using the catalyst according to one example of the present invention, reaction conditions generally used in the technical field to which the present invention pertains can be adopted.

[0082] In one example, the ammonia decomposition reaction can be carried out at a temperature of about 400 to about 550°C, or about 400°C or higher, or more than about 400°C, or about 420°C or higher, and at the same time, about 600°C or lower, or about 550°C or lower, or about 530°C or lower.

[0083] According to another example, the ammonia decomposition reaction may be carried out after purging with an inert gas or the like prior to the full-scale reaction.

[0084] The shape of the reactor during the reaction is not particularly limited, and any suitable reactor that can blow ammonia gas into the catalyst of the above-mentioned shape and bring the catalyst and the reactant into direct contact with each other can be selected and used. [Effects of the Invention]

[0085] According to the present invention, an ammonia decomposition catalyst having high ammonia decomposition efficiency can be provided.

[0086] Furthermore, according to the present invention, it is possible to provide an ammonia decomposition method using such an ammonia decomposition catalyst. [Brief explanation of the drawings]

[0087] [Figure 1] 1 is a schematic diagram showing the shape of a hollow cylinder of a catalyst according to an example of the present invention. [Figure 2-4] 1 is a photograph showing catalysts according to an example of the present invention and a comparative example. [Figure 5-6] 1A and 1B are images of the catalysts prepared in Comparative Examples 4 and 5, respectively. [Figure 7] 1 is a SEM image of the catalyst prepared in Example 1. [Figure 8-9] 1A and 1B are SEM images of the catalysts prepared in Comparative Examples 4 and 5, respectively. [Figure 10] 1 is a SEM-EDS image of the catalyst prepared in Example 1. [Figure 11-12] 1A and 1B are SEM-EDS images of the catalysts prepared in Comparative Examples 4 and 5, respectively. DETAILED DESCRIPTION OF THE INVENTION

[0088] The functions and effects of the present invention will be described in more detail below through specific examples of the invention. However, these examples are presented only as examples of the invention and do not define the scope of the invention. [Example]

[0089] <Example> (Examples 1 to 5 and Comparative Example 1) As the source of the metal components, LaCeria synthesized by the coprecipitation method or commercial LaAlOx (material: LaAlOx; manufacturer: Sasol; product name: SCFa-145 / L4) was used.

[0090] The material was added to distilled water and stirred at 300 rpm for 30 minutes, and then ruthenium chloride hydrate was added and stirred for an additional 30 minutes, taking into account the content of each metal element in the catalytically active component. The pH was adjusted to 9 using aqueous ammonia, and the mixture was stirred for 18 hours using a stirrer and magnetic bar. The mixture was filtered and washed with water until the filtered liquid became neutral, and then dried in an oven at 110°C for approximately 6 hours to obtain a powder.

[0091] 18 g of the obtained powder was placed in a milling device and ball milled using 300 g of zirconia balls with a diameter of 3 mm and 60 g of zirconia balls with a diameter of 5 mm at a roller speed of 200 rpm for 6 hours to adjust the particle size.

[0092] Then, 79.2 g of distilled water and 1.8 g of boehmite were added and stirred for 6 hours with a roller at 200 rpm. The boehmite was dissolved and used as a binder by adjusting the pH to 3.5 with 60% nitric acid solution.

[0093] Approximately 50 g of a ceramic hollow cylinder (material: ceramic rings; manufacturer: Saint Gobain NorPro; product name: SA5518) having a silica coating layer formed on an alumina substrate was added to the solution as a support and coated, and the filtrate was then removed using an air gun.

[0094] This was placed in an oven at approximately 110°C and dried for approximately 6 hours. Drying and coating were repeated until 10 wt% of the coated catalyst became a powder catalyst. As a result, a molded catalyst was obtained in which the catalyst was coated on the surface of a ceramic hollow cylinder.

[0095] The metal components in the obtained catalyst material were analyzed using ICP-OES, and the presence or absence of structural changes in the support was confirmed through Hg porosity.

[0096] Figure 2 is an image of the catalyst prepared in Example 1. Referring to Figure 2, the catalyst has a hollow cylindrical shape.

[0097] 7 is an SEM image of the catalyst prepared in Example 1. In the SEM image of the catalyst of Example 1, white, light gray, and dark gray can be observed, except for the black background. The dark gray represents the alumina substrate, the light gray represents the silica layer, and the white represents the catalyst layer, respectively. This clearly shows the layered structure of the catalyst according to one embodiment of the present application, which includes a substrate containing alumina, a silica layer formed on the alumina, and a catalyst layer formed on the silica layer.

[0098] Figure 10 is an SEM-EDS image of the catalyst prepared in Example 1. SEM-EDS allows the distribution of elements such as ruthenium, lanthanum, and cerium in the catalyst to be confirmed. In particular, ruthenium, which can be considered the main active site of the catalyst, appears light in color due to its low content throughout the catalyst, but it can also be clearly seen that it is uniformly and well-dispersed throughout the catalyst.

[0099] (Comparative Examples 2 and 3) In Comparative Examples 2 and 3, the same procedures as in Examples 1 and 2 and Comparative Example 1 were carried out, but without carrying, the obtained powder itself was molded into a catalyst.

[0100] 3 and 4 are photographs of the unsupported catalysts prepared according to Comparative Examples 2 and 3, respectively.

[0101] Comparative Example 4 A spherical supported catalyst was obtained in the same manner as in Example 1, except that i) spherical alumina was used as the support, and ii) potassium was added as a promoter.

[0102] Ru(0.5) / Al2O3; ruthenium content in the final catalyst is 0.5 wt% (Comparative Example 5) A spherical supported catalyst was obtained in the same manner as in Example 1, except that spherical alumina was used as the support.

[0103] Ru(1.5) / Al2O3; ruthenium content in the final catalyst is 1.5 wt% 5 and 6 are images of the catalysts prepared in Comparative Examples 4 and 5, respectively. Referring to FIGS. 5 and 6, the spherical supported catalysts can be seen.

[0104] 8 and 9 are SEM images of the catalysts prepared in Comparative Examples 4 and 5, respectively. In the SEM images of the catalysts prepared in Comparative Examples 4 and 5, light gray and dark gray can be observed in addition to the black background. This is identified as the alumina substrate (dark gray) and the catalyst layer (light gray), respectively.

[0105] Figures 11 and 12 are SEM-EDS images of the catalysts prepared in Comparative Examples 4 and 5, respectively. SEM-EDS allows the distribution of elements such as ruthenium, lanthanum, and potassium in the catalyst to be confirmed, and in particular, ruthenium, which can be considered the main active site of the catalyst, can be clearly seen to be distributed only on the catalyst surface.

[0106] Information about the obtained catalysts is summarized in Table 1 below.

[0107] [Table 1]

[0108] (Stomata characteristics analysis) The pore characteristics of the catalysts prepared in the examples and comparative examples were analyzed by mercury pore analysis using a mercury pressure pore distribution measuring device (manufacturer: Micromeritics; model name: AutoPoreV).

[0109] Without any additional pretreatment, an appropriate amount of sample was placed in the sample cell, and then pressurized in the range of 0.2 to 33,000 psi to inject mercury into the catalyst pores and measure the pore volume. The median value was used as the average diameter of the values ​​obtained in the analysis.

[0110] [Table 2]

[0111] (Ammonia decomposition reaction) 3 g of each of the catalysts prepared in the examples and comparative examples was taken and packed into an OD 1 / 2" reactor, heated to 350°C using nitrogen gas, and reduced at the same temperature for about 1 hour by flowing a hydrogen / nitrogen mixed gas (hydrogen 50 v%).

[0112] The reduced catalyst was purged in a nitrogen atmosphere at about 350°C for about 30 minutes, and the temperature of the reaction system was raised to about 500°C while flowing 99.99% ammonia gas at a rate of 10 sccm, and the ammonia decomposition rate was analyzed at 50°C intervals.

[0113] The analysis results are summarized in Table 3 below.

[0114] [Table 3]

[0115] Referring to Table 3, it can be seen that the catalyst according to the embodiment of the present invention has a very high ammonia conversion rate and that there is almost no pressure difference between the front and rear ends of the reactor, which means that the gas flow is very smooth in the catalyst-packed part of the reactor.

[0116] In addition, in the case of the example, it can be confirmed that the catalyst strength is high and the temperature difference in the catalyst layer is very small.

[0117] In the case of the comparative example, the ammonia conversion rate was lower than that of the examples, and a certain pressure difference was observed between the front and rear ends of the reactor, which means that the gas flow was not smooth in the catalyst-packed part of the reactor.

[0118] In some comparative examples, the catalyst strength was low, and in this case, the catalyst located at the bottom of the catalyst-packed section could not withstand the weight and pressure and break, causing the catalyst-packed section to collapse.

[0119] In addition, it can be seen that the comparative example has a larger difference in catalyst layer temperature than the example. When catalytically active materials are packed densely like this, the reaction (endothermic reaction) occurs suddenly, causing a large temperature drop at the center of the catalyst packing, which can significantly reduce reaction activity.

Claims

1. A catalyst comprising a support and a catalytically active component supported on the support, The catalytically active component comprises: i) a first metal, ruthenium (Ru); ii) a second metal, lanthanum (La); and iii) a third metal, any one or more of aluminum (Al) and cerium (Ce); The porosity is 25% or more. Ammonia decomposition catalyst.

2. 2. The ammonia decomposition catalyst according to claim 1, wherein the median pore size is 50 to 150 μm.

3. 2. The ammonia decomposition catalyst according to claim 1, wherein the support is an inorganic oxide structure.

4. 2. The ammonia decomposition catalyst according to claim 1, wherein the first metal is contained in an amount of 0.01 to 0.5 parts by weight per 100 parts by weight of the total of the support and the catalytically active component.

5. 2. The ammonia decomposition catalyst according to claim 1, wherein the catalytically active component is contained in an amount of 20 parts by weight or less relative to a total of 100 parts by weight of the carrier and the catalytically active component.

6. 2. The ammonia decomposition catalyst according to claim 1, wherein the weight ratio of (second metal):(third metal) is 1:99 to 3:

7.

7. 2. The ammonia decomposition catalyst according to claim 1, wherein the first metal is contained in an amount of 0.1 to 10% by weight based on the total weight of the catalytically active components.

8. 10. The ammonia decomposition catalyst according to claim 1, which is in the shape of a hollow cylinder.

9. 9. The ammonia decomposition catalyst according to claim 8, wherein the diameter of the cross-sectional circle of the hollow cylinder is 1 to 10 mm.

10. 9. The ammonia decomposition catalyst according to claim 8, wherein the diameter of the hollow is 0.1 to 0.5 of the diameter of a circular cross section of a cylinder.

11. the support includes a substrate comprising alumina and a silica layer formed on the alumina; the catalytically active component is contained in a catalyst layer formed on the silica layer; The ammonia decomposition catalyst according to claim 1.

12. An ammonia decomposition method, comprising carrying out an ammonia decomposition reaction in the presence of the ammonia decomposition catalyst according to any one of claims 1 to 11.

13. The method for decomposing ammonia according to claim 12, which is carried out at 400 to 600°C.

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