Trimetal catalyst for ammonia cracking reaction, method for producing same, and method for producing hydrogen using same

Abstract

This invention relates to a method for preparing a triple-metal composite catalyst of ruthenium, yttrium, and potassium using a thermally deformed delta-alumina support, and a method for producing hydrogen through an ammonia cracking reaction using the same. This ammonia cracking catalyst achieves significantly higher ammonia conversion and hydrogen production efficiency at low temperatures compared to catalysts with the same ruthenium metal content, even when using a low ruthenium metal content, by adjusting the ruthenium / [potassium + yttrium] ratio with a specific phase of thermally deformed alumina support, minimizing the content of chlorine and nitrogen compounds as impurities in the catalyst, and specifying the location of the active metal in the catalyst.

Description

[Technical Field]

[0001] The present invention relates to a high-yield trimetal catalyst composition that can stably produce hydrogen even at low temperatures as a catalyst for a cracking reaction that produces hydrogen from ammonia, a method for producing the same, and a method for producing hydrogen using the same. [Background technology]

[0002] In recent years, the demand for energy has increased worldwide due to industrial development and population growth, but the fossil fuels used as energy sources are gradually becoming depleted. In addition, in order to prepare for global warming caused by greenhouse gases, countries around the world are continuing to research clean energy sources that can replace fossil fuels. Among these, the substance that has been most actively researched as an environmentally friendly energy source is hydrogen.

[0003] As an environmentally friendly hydrogen production technology, much research has been conducted on the ammonia cracking reaction process, which produces hydrogen from ammonia. The ammonia cracking reaction is an endothermic reaction in which ammonia is decomposed into hydrogen and nitrogen, and therefore requires the supply of heat. The ammonia cracking reaction has an equilibrium conversion rate of 450-500°C, and because all ammonia is converted to hydrogen at relatively low temperatures, the energy cost is relatively low. However, because the reaction itself is endothermic, high temperatures (above 500°C) are required. Further development is needed to bring this reaction into a more moderate temperature range, and one of the areas of interest is the development of a catalyst that can achieve a high ammonia conversion rate at low temperatures.

[0004] Catalyst compositions developed to date include active metals such as precious metals (platinum, palladium, rhodium, ruthenium, and iridium) and non-precious metals (nickel, copper, chromium, cobalt, and iron), while support materials such as silica, alumina, activated carbon, graphite, mesoporous carbon, and carbon nanotubes have been studied (Muhammad Aziz et al., Energies 2020, 13, 3062). While numerous catalysts have been developed using combinations of active metals and supports, most require operating temperatures above 600°C for 100% conversion of ammonia to hydrogen. Therefore, for commercial crackers, catalysts with high activity at lower temperatures are needed. In particular, catalysts capable of operating at reaction temperatures of 300–500°C are needed for ships and small-scale ammonia co-firing power generation.

[0005] As has been known in the art, many ammonia cracking catalysts have problems such as the need for high reaction temperatures to increase ammonia conversion rates and the need to support large amounts of expensive metals on the catalyst, which significantly reduces economic viability. Improvements to these problems are needed, and the present invention aims to solve these problems by producing a catalyst using a method for combining a low content of ruthenium with an auxiliary metal and a specific catalyst support. Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention has been made to solve the above-mentioned problems, and its object is to provide a method for producing an ammonia cracking catalyst that can improve ammonia conversion at low temperatures and exhibit long-term stability by producing a catalyst using a low content of ruthenium as an ammonia cracking catalyst, potassium and yttrium as auxiliary metals, and a specific support, and a method for producing hydrogen through an ammonia cracking reaction using the same. [Means for solving the problem]

[0007] In order to achieve the above technical objectives, the inventors have manufactured a catalyst using an alumina support having a specific crystalline phase, which allows the reactant ammonia to diffuse within the catalyst and the product to quickly move out of the catalyst. The inventors then arranged ruthenium as the main metal on the manufactured support, and yttrium and potassium as auxiliary metals that can increase the reaction rate of ruthenium, in a trimetallic form, to manufacture a catalyst in which the unique properties of each metal are expressed.

[0008] In the catalyst prepared according to the present invention, yttrium (Y) exists in the form of Al-YO-Al-O bonded to the alumina support, and not only plays a role in decomposing and dissociating and adsorbing H ions from ammonia, but also increases the mobility of H ions to the Ru side, thereby accelerating the rate of H2 generation. Potassium (K) weakens the strength of adsorption of N2 generated after the cracking reaction onto the catalyst, inducing rapid desorption from the catalyst, thereby increasing the catalytic reaction rate and improving durability. Furthermore, a separate process for removing chlorine and nitrogen compounds remaining in the catalyst during the catalyst preparation process was conducted, maximizing the active sites of ruthenium during the ammonia cracking reaction, thereby demonstrating high conversion rates even at low temperatures. The present invention has the following non-limiting configuration.

[0009] (1) A catalyst used to produce nitrogen and hydrogen through an ammonia cracking reaction, characterized in that the catalyst support is delta alumina thermally transformed from alumina hydrate, a ruthenium-yttrium-potassium triple metal composite metal is supported as the active metal, and chlorine and nitrogen compounds are present in the catalyst in an amount of 10 ppm or less based on the weight of the catalyst.

[0010] (2) The support is characterized in that alumina and alumina hydrate manufactured in a shaped form such as a sphere, tablet, or structure are thermally deformed and used, and the delta alumina support that has undergone a phase change after the heat treatment has a volume density of 0.5 to 1.2 g / ml and a specific surface area of ​​100 to 200 m 2 / g, pore volume is 0.4-0.5 cm 3 / g, and an average pore size distribution in the range of 10 to 14 nm.

[0011] (3) An ammonia cracking catalyst characterized in that the main metal in the catalyst, ruthenium, is distributed within 30% of the length from the outer periphery to the center of the catalyst, and the auxiliary metals, yttrium and potassium, are uniformly distributed inside the catalyst.

[0012] (4) The ruthenium is 0.5 to 3.0 wt% based on the weight of the catalyst, and 0.005 to 0.028 wt% / m within 30% of the length from the outer periphery to the center of the catalyst. 2 The content of yttrium and potassium in the catalyst is 0.01 to 0.05 wt% / m 2 1. An ammonia cracking catalyst, characterized in that the catalyst is uniformly present at a content per specific surface area of ​​1.

[0013] (5) An ammonia cracking catalyst characterized in that the weight ratio of (yttrium + potassium) / ruthenium in the active metals is in the range of 4 to 8, the weight ratio of yttrium / ruthenium is 1 to 2, and the weight ratio of potassium / ruthenium is 3 to 6.

[0014] (6) An ammonia cracking catalyst, characterized in that the residual chlorine compounds in the catalyst are removed by an ion exchange method using a basic substance, and the nitrogen compounds are removed by a high-temperature heat treatment method to 10 ppm or less based on the weight of the catalyst.

[0015] (7) A method for producing a catalyst for use in an ammonia cracking reaction, comprising the steps of: a) heat-treating spherical bohemite (AlOOH) at a temperature in the range of 750-900°C to produce an alumina support having a delta crystal phase; b) supporting the produced delta-alumina (δ-Al2O3) support with a solution of an yttrium precursor (Y(NO3)3) dissolved in a solvent by a pressurized spray method at room temperature; c) drying the supported material at 100-120°C and calcining it at 500-600°C; d) supporting the produced yttrium / delta-alumina material with a solution of a ruthenium precursor (RuCl3) dissolved in a solvent by a pressurized spray method at room temperature; and e) supporting the supported material at 100-120°C. a) drying the catalyst at 0-120°C and calcining at 500-600°C, and removing residual Cl through ion exchange; b) loading the resulting ruthenium / yttrium / delta alumina material with a solution of potassium precursor (KNO3) dissolved in a solvent at room temperature using a pressurized spray method; c) drying the resulting catalyst at 100-120°C and calcining at 500-600°C to remove residual NO3; and d) subjecting the resulting potassium / ruthenium / yttrium / delta alumina oxidation catalyst to a rapid reduction process at high temperature using hydrogen gas at 400-500°C to produce a final catalyst.

[0016] (8) Used in ammonia cracking reactions, it produces ammonia gas at a reaction temperature of 300-550°C for GHSV of 2,000-20,000h. -1 The ammonia cracking catalyst is characterized by the reaction occurring under the above conditions, and exhibits a high hydrogen conversion rate. [Effects of the Invention]

[0017] The present invention relates to a ruthenium-based ammonia cracking catalyst, and more particularly to an ammonia cracking catalyst prepared by selecting active metals consisting of ruthenium as the main metal, yttrium as auxiliary metals, and potassium on a delta alumina support, and a method for preparing the same. The ammonia cracking catalyst according to the present invention can achieve a very high ammonia conversion rate and hydrogen production efficiency even at low temperatures compared to catalysts having the same ruthenium content by using a specific phase of thermally deformed alumina support and adjusting the weight ratio of ruthenium / yttrium / potassium to minimize the content of chlorine and nitrogen compounds as impurities in the catalyst and by specifying the position of the active metal in the catalyst, even when using a low content of ruthenium metal. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a flowchart illustrating steps of a manufacturing method according to a first embodiment of the present invention. [Figure 2] 1 shows electron microscope (Video microscopy) and electron probe X-ray microanalyzer (EPMA) photographs of the catalyst prepared in Example 1 of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0019] definition In the present invention, the term "active metal" includes both the main metal and the auxiliary metal, and the support is an oxide for supporting the active metal, and is also called a carrier.

[0020] The present invention relates to an ammonia cracking catalyst for hydrogen production and a manufacturing method thereof, and more particularly to a catalyst and manufacturing method thereof, which are manufactured by the steps of manufacturing a delta alumina support having adjusted acid sites and pore size, selecting active metals in which ruthenium is the main metal and yttrium and potassium are the auxiliary metals, and removing chlorine and nitrogen compounds remaining in the catalyst derived from the metal precursors.

[0021] According to the present invention, hydrogen ions dissociated by the bond between yttrium and the support may generate hydrogen at a rapid rate by ruthenium. If this reaction continues, the ruthenium gradually sinters, causing the particle size to increase and the cracking conversion rate to decrease. However, in order to prevent this sintering phenomenon, potassium is strongly bonded to ruthenium, which prevents the particle growth of ruthenium during the reaction. It has been found that potassium can play a role in suppressing the particle growth of ruthenium during the reaction and improving the durability of the catalyst.

[0022] In addition, when the main metal in the active metal is generally distributed throughout the support, the frequency of contact between the reactants and the support / active metal decreases, resulting in a loss of the amount of hydrogen produced per unit time (ammonia conversion rate). To solve this problem, ruthenium is located on the surface of the support, and the ruthenium concentrated on the catalyst surface increases hydrogen production even when the reactants are drawn into the reactor at a high space velocity. In the case of yttrium and potassium, the catalyst was manufactured by distributing them uniformly within the support to maximize their interaction with the alumina support. Preferred embodiments of the present invention are described in detail below.

[0023] The composite metal catalyst of the present invention, in which ruthenium auxiliary metal is supported on a thermally deformed alumina support having controlled crystal phase and pore characteristics, can be prepared by the following steps. a) heat-treating spherical bohemite (AlOOH) at a temperature in the range of 750-900°C to prepare an alumina support having a delta crystal phase;

[0024] b) Supporting a solution of yttrium precursor (Y(NO)) in a solvent on the prepared delta-alumina (δ-AlO) support by pressurized spraying at room temperature; c) after supporting yttrium, drying at 100 to 120°C and calcining at 500 to 600°C;

[0025] d) supporting a solution of ruthenium precursor (RuCl3) dissolved in a solvent on the prepared yttrium / delta alumina material by pressurized spraying at room temperature; e) after supporting ruthenium, drying at 100 to 120°C and calcining at 500 to 600°C, and removing residual Cl by ion exchange;

[0026] f) supporting a solution of potassium precursor (KNO3) dissolved in a solvent on the prepared ruthenium / yttrium / delta alumina material by pressurized spraying at room temperature; g) After the potassium is supported, drying is performed at 100 to 120°C, and the remaining NO3 is removed by calcination at 500 to 600°C.

[0027] h) The potassium / ruthenium / yttrium / delta alumina oxidation catalyst is subjected to a rapid reduction process at high temperature using hydrogen gas at a temperature of 400 to 500°C to obtain the final catalyst. Each step will be explained in detail.

[0028] In step a), the alumina support can be prepared by using bohemite or gamma alumina as the starting material. To remove acid sites and adjust the pore size of the support, the support can be heat-treated in a heat treatment furnace at 750-900°C for 1-5 hours to transform the support into a crystalline phase containing 90% or more delta alumina. The heat treatment temperature is closely related to the crystalline phase and pore structure of the support. Bohemite has four alumina phases (gamma, delta, theta, and alpha) depending on the heat treatment temperature, and delta alumina is produced by a phase transition between approximately 750-900°C. Table 1 shows the changes in alumina crystalline phase, specific surface area, pore volume, and pore size that occur when bohemite is heat-treated at different temperatures. Table 1 (Pore characteristics by support firing temperature)

[0029] [Table 1]

[0030] Delta alumina has a similar specific surface area to gamma alumina but an increased pore size, which allows for more space for active metals to be located inside the alumina. It also weakens the Lewis acid sites and Bronsted acid sites of gamma alumina, allowing the reactant ammonia to react only with the active metal. The high specific surface area improves metal dispersion when supporting the active metal, and the increased pore size has the advantage of improving the air permeability between the reactants and the catalyst when applied to cracking reactions, potentially increasing the catalytic reaction rate.

[0031] On the other hand, theta or alpha alumina heat-treated at higher temperatures, especially above 900°C, has larger pore diameters, but suffers from the drawback of a rapid decrease in specific surface area and the occurrence of aggregation of metal particles during the process of supporting the active metal, resulting in low dispersion, making it unsuitable as a support for use in the manufacturing method of the present invention. The alumina supports thus produced have a volume density of 0.5 to 1.2 g / ml and a specific surface area of ​​100 to 200 m. 2 / g, pore volume 0.4-0.5 cm 3 / g, the average pore size distribution may be 10 to 14 nm, and the delta alumina / gamma alumina ratio may be 9 or more. The support may be in the form of a sphere, cylinder, pellet, or tube, and these shapes may be manufactured by oil-drop, tableting, or extrusion.

[0032] In step b), the yttrium precursor can be any of yttrium nitrate hydrate, yttrium chloride hydrate, yttrium acetate hydrate, and yttrium sulfate hydrate. Preferably, yttrium nitrate is used, which can enhance ruthenium dispersion. The yttrium precursor can be prepared by dissolving it in ionized water or a dihydric alcohol (e.g., ethanol or ethylene glycol) in a solvent equal to the pore volume of the support, and then supporting it on the support using a pressurized spray method. The yttrium precursor can be supported at 1 to 4 wt% of the final catalyst. If the yttrium precursor is supported at less than 1 wt%, it is difficult to achieve catalytic performance. If the yttrium precursor is supported at more than 4 wt%, it is not absorbed into the support and accumulates on the surface of some of the support, resulting in low ruthenium activity and reduced durability. The yttrium precursor can be prepared at a level of 1 to 2 based on the weight ratio of yttrium / ruthenium, and preferably at a level of 1 based on the weight ratio of yttrium / ruthenium.

[0033] Step c) may include a step of drying the yttrium / delta alumina prepared in step b) at 100-120°C and then heat-treating it at 500-600°C to remove moisture and precursor materials derived from the metal precursor.

[0034] In step d), the ruthenium precursor can be any of ruthenium nitrate hydrate, ruthenium chloride hydrate, ruthenium acetate hydrate, ruthenium hydroxide hydrate, and ruthenium nitrosyl nitrate hydrate. Ruthenium chloride is preferred, as it can enhance ruthenium dispersion. The active metal precursor can be prepared by dissolving it in a solvent of ionized water or a dihydric alcohol (e.g., ethanol or ethylene glycol) in an amount equal to the pore volume of the support, and then supporting it on the support using a pressurized spray method. The ruthenium precursor can be supported at a level of 0.5 to 3 based on the weight ratio of the final catalyst, and for commercial applications, it is preferably prepared at a level of 1 to 2.

[0035] Step e) can include drying the ruthenium / yttrium / delta-alumina material produced in step d) at 100-120°C to remove water and precursor materials derived from the metal precursor, followed by heat treatment in an air atmosphere at 500-600°C. Furthermore, when ruthenium chloride is used as the metal precursor, chloride ions may remain even after the heat treatment, so a step of removing them by ion exchange using a basic substance can be added. The basic substance can be any of ammonium hydroxide, ammonium nitrate, sodium hydroxide, and sodium nitrate, with ammonium hydroxide being preferred for its ease of cleaning.

[0036] In step f), the potassium precursor can be any of potassium nitrate hydrate, potassium chloride hydrate, potassium acetate hydrate, and potassium hydroxide hydrate. Preferably, potassium nitrate is used, which can enhance ruthenium dispersibility. The potassium precursor can be prepared by dissolving it in a solvent of ionized water or a dihydric alcohol (e.g., ethanol or ethylene glycol) in an amount equal to the pore volume of the support, and then supporting it on the support using a pressurized spray method. The potassium precursor can be supported in an amount of 4 to 10 wt% based on the final catalyst. If the amount is less than 4 wt%, it is difficult to achieve catalytic performance. If the amount is more than 10 wt%, the potassium precursor is not absorbed into the support and accumulates on the surface of some of the support, resulting in low ruthenium activity and reduced durability. The potassium precursor can be prepared at a level of 3 to 6 based on the weight ratio of potassium to ruthenium, and preferably at a level of 3 to 4 based on the weight ratio of potassium to ruthenium.

[0037] Step g) may include drying the potassium / ruthenium / yttrium / delta-alumina material prepared in step f) at 100-120°C to remove moisture and precursor materials derived from the metal precursor, followed by heat treatment in an air atmosphere at 500-600°C. The heat treatment temperature may be within a suitable range according to common knowledge, and therefore will not be described in further detail.

[0038] In step h), the potassium / ruthenium / yttrium / delta alumina oxide prepared in step g) is rapidly reduced using hydrogen gas at a temperature between 400 and 600°C, preferably between 400 and 500°C, to obtain the final catalyst. If the reduction temperature is below 400°C, the metal oxide species may not be completely reduced. If the reduction temperature is higher than 600°C, the metal particles may aggregate and sinter, resulting in a decrease in active sites. The reduction process involves raising the temperature to the target temperature in a nitrogen atmosphere in a stepwise manner, followed by flowing hydrogen gas. When the catalyst contains two or more active metal species, immediate exposure to hydrogen gas at a high temperature, as in the reduction method described above, can instantly produce an alloy of the active metal species. However, if the temperature is gradually increased from room temperature to a hydrogen atmosphere, the metal species are each reduced according to their specific oxygen desorption temperatures, making it difficult to form an alloy.

[0039] The catalyst prepared in the present invention can be used in the cracking reaction of ammonia gas after being introduced into a reactor, and can crack ammonia gas at a reaction temperature of 300 to 550°C for a GHSV (Gas Hourly Space Velocity) of 2,000 to 20,000 h. -1Hydrogen can be produced by a gas-phase reaction under the above conditions. The higher the GHSV, the greater the hydrogen production volume. Therefore, the optimum value can be adjusted according to the reactor volume and catalyst amount, and is not limited to a specific value within the range. The reactor for producing hydrogen through the reforming reaction is not particularly limited, but a fixed-bed catalytic reactor, in which a catalyst is packed inside the reactor, can be used. Furthermore, since the cracking reaction is an endothermic reaction, it is important that the catalytic reactor remains adiabatic. It is important to maintain the reaction conditions of the reaction temperature, pressure, and GHSV within the appropriate ranges for the cracking reaction process of the present invention. If the reaction temperature is below 300°C, the cracking reaction will not proceed sufficiently, resulting in a very low amount of hydrogen. If the reaction temperature is above 500°C, the energy cost for application will increase and efficiency will decrease. The technical configuration of the present invention will be described in detail below with reference to the drawings, examples, and comparative examples. Example 1

[0040] The support was a 1.8 mm spherical bohemite (manufacturer: BASF, Germany, specific surface area: 250 m 2 The support was used after calcining at 900°C for 5 hours to induce a phase transformation. The phase-transformed support had a delta alumina crystalline phase and a specific surface area of ​​153 m 2 / g, pore volume 0.47 cm 3The catalyst has physical properties of 0.01g / g and a pore size of 12.6nm. First, to support the metal, yttrium was used as a precursor, yttrium nitrate (Y(NO3)3·6H2O). The yttrium precursor was dissolved in water and impregnated into the phase-transformed delta-alumina support using a spray impregnation method. After impregnation, the catalyst underwent an aging process for approximately one hour to ensure that the metal solution was fully distributed throughout the support. The catalyst was then dried at 120°C for 12 hours to completely remove moisture from the catalyst, and the metal was then immobilized by heat treatment in an air atmosphere at 600°C for six hours. Next, to support ruthenium, the main active metal, ruthenium chloride (RuCl3·xH2O) was used as a precursor, dissolved in water, and impregnated into the yttrium / delta-alumina using a spray impregnation method. The produced ruthenium / yttrium / delta alumina was dried at 120°C for 12 hours to completely remove moisture from the catalyst, and then heat-treated in an air atmosphere at 600°C for 6 hours to immobilize the metal. The heat-treated ruthenium / yttrium / delta alumina oxide was then further treated with ammonia water to ion-exchange the remaining chloride components in the oxide with ammonium chloride, followed by washing and removal.

[0041] Next, potassium nitride (KNO3) was also supported on ruthenium / yttrium / delta-alumina oxide using a spray-loading method. Finally, the metal-loaded potassium / ruthenium / yttrium / delta-alumina composition was heat-treated in an air atmosphere at 550°C for 4 hours to produce a metal-loaded catalyst oxide. Finally, the heat-treated oxide was heated to 500°C in an air atmosphere, purged with nitrogen for 5 minutes, and then rapidly reduced in a hydrogen gas flow to produce a catalyst. The overall manufacturing procedure and method are shown in Figure 1.

[0042] The catalyst prepared in Example 1 was confirmed to contain 1.93 wt% yttrium, 1.7 wt% ruthenium, 6.8 wt% potassium, 4 ppm chloride ions, and 0 ppm nitrate ions. Furthermore, the yttrium and potassium were uniformly distributed within the support, and the ruthenium was distributed to a depth of approximately 30% from the outer periphery of the catalyst. The metal distribution within the catalyst prepared in Example 1 is shown in Figure 2. Example 2

[0043] A catalyst was produced in the same manner as in Example 1, except that the final catalyst was produced so that the metal contents were 3.86 wt % yttrium, 1.7 wt % ruthenium, and 6.8 wt % potassium. Example 3

[0044] A catalyst was produced in the same manner as in Example 1, except that the final catalyst was produced so that the metal contents were 0.57 wt % yttrium, 0.5 wt % ruthenium, and 2.0 wt % potassium.

[0045] Comparative Example 1 A catalyst was produced in the same manner as in Example 1, except that it was produced without containing yttrium.

[0046] Comparative Example 2 A catalyst was produced in the same manner as in Example 1, except that potassium was not added.

[0047] Comparative Example 3 A catalyst was produced in the same manner as in Example 1, except that it was produced without containing yttrium and potassium.

[0048] Comparative Example 4 A catalyst was produced in the same manner as in Comparative Example 3, except that ruthenium was supported at 2 wt %.

[0049] Comparative Example 5 A catalyst was produced in the same manner as in Comparative Example 3, except that ruthenium was supported at 3 wt %.

[0050] Comparative Example 6 A catalyst was produced in the same manner as in Example 1, except that the heat treatment temperature when producing the support used in Example 1 was 1000°C. The crystalline phase of the support of this catalyst was theta phase, and the specific surface area was 93 m 2 / g and the pore diameter was 14.1 nm. Comparative Example 7

[0051] A catalyst was produced in the same manner as in Example 1, except that the heat treatment temperature when producing the support used in Example 1 was 1200°C. The crystalline phase of the support of this catalyst was the alpha phase, and the specific surface area was 3 m 2 / g and the pore diameter was 98 nm.

[0052] The material constitution and active metal composition of the catalysts in the above examples and comparative examples are summarized in Table 2. Table 2 (Manufacturing methods of Examples and Comparative Examples)

[0053] [Table 2]

[0054] Reaction examples The catalysts prepared in the above examples were evaluated for their performance as follows. To measure catalytic activity, a cracking reaction was carried out using ammonia gas. The reactor was evaluated using a fixed-bed reaction system. 3 ml of the catalyst was packed into a tubular reactor. Prior to the reaction, hydrogen gas was supplied at a constant rate of 10 cc / min to remove oxygen species from the catalyst surface, and the catalyst was reduced at 400°C for 1 hour. The reactor temperature was then maintained constant at 300°C, 400°C, and 500°C. Ammonia gas, the raw material used in the reaction, was continuously supplied to the reactor at a constant rate of 100 cc / min, and the GHSV was maintained at 2,000 h. -1The reaction pressure was evaluated under atmospheric pressure. The substances produced after the reaction were transferred to a GC (Gas Chromatography) via an injection line and quantitatively analyzed using a TCD (Thermal Conductivity Detector).

[0055] The conversion rate of ammonia to the reactants was calculated according to the following criteria to compare the activity of the catalysts. The results are shown in Table 3. Ammonia conversion rate (%) = [number of moles of ammonia before reaction - number of moles of ammonia after reaction] / [number of moles of ammonia before reaction] x 100 Table 3 (Ammonia cracking reaction evaluation results for Examples and Comparative Examples)

[0056] [Table 3]

[0057] These catalysts were commonly manufactured with ruthenium, the main active metal, located at approximately 30% of the catalyst's periphery to increase the rate of hydrogen production from the reactants, and with yttrium and potassium, the auxiliary metals, uniformly distributed throughout the catalyst to maximize interaction with the alumina support. The catalysts were also manufactured with all impurities, such as chlorine and nitrogen compounds, removed. Example 1 and Comparative Examples 1-3 were manufactured with or without the addition of potassium and yttrium, the auxiliary metals. Activity evaluation revealed that Example 1 exhibited the highest low-temperature activity, ultimately achieving 100% ammonia conversion at 500°C. This indicates that yttrium contributes to increasing ammonia conversion at low temperatures, while potassium contributes to increasing the overall conversion rate.

[0058] In Comparative Examples 3 to 5, catalysts were prepared by varying the amount of ruthenium, the main active metal, at 1.7 wt%, 2 wt%, and 3 wt%, and the ammonia conversion rate increased with the amount of ruthenium supported, but the conversion rate at 500°C did not reach 100%. However, the catalyst of Example 1, which further supported yttrium and potassium at the same 1.7 wt% ruthenium content as Comparative Example 3, showed a higher ammonia conversion rate than the 3 wt% ruthenium-supported catalyst of Comparative Example 5, demonstrating that the combination of ruthenium and auxiliary metals can contribute to significantly increasing reaction activity.

[0059] In Example 1 and Comparative Examples 6 and 7, catalysts were produced by changing the crystalline phase of the alumina catalyst support. Activity evaluation showed that the catalysts exhibited lower ammonia cracking reaction activity than Example 1. In particular, Comparative Example 7 exhibited 11% lower reactivity at 400°C and 48% lower reactivity at 500°C than Example 1, demonstrating that the crystalline phase of the support has an important effect on the ammonia cracking reaction.

[0060] As a result, by producing a catalyst as in Example 1, with a support crystal phase of delta alumina, metals of 1.7 wt % ruthenium, 6.8 wt % potassium, and 1.93 wt % yttrium, and a weight ratio of [yttrium + potassium] / ruthenium of approximately 5.1, it is possible to produce a catalyst that exhibits a high ammonia cracking conversion rate at a relatively low temperature of 300 to 500°C.

Claims

1. A catalyst for an ammonia cracking reaction, comprising: The catalyst support is delta alumina thermally transformed from alumina hydrate, and a triple metal composite metal of ruthenium-yttrium-potassium is supported as the active metal. The amount of chlorine and nitrogen compounds in the catalyst is 10 ppm or less based on the weight of the catalyst. An ammonia cracking catalyst characterized by:

2. The thermally deformed delta alumina support has a volume density of 0.5 to 1.2 g / ml and a specific surface area of ​​100 to 200 m ２ / g, pore volume is 0.4 to 0.5 cm ３ / g, and the average pore size distribution is in the range of 10 to 14 nm.

2. The ammonia cracking catalyst of claim 1.

3. The ruthenium is distributed within 30% of the length from the outer periphery to the center of the catalyst, and the yttrium and potassium are uniformly distributed inside the catalyst.

2. The ammonia cracking catalyst of claim 1.

4. The ruthenium is contained in an amount of 0.5 to 3.0 wt % based on the weight of the catalyst, and is contained in an amount of 0.005 to 0.028 wt % / m within 30% of the length from the outer periphery to the center of the catalyst. ２ exists at a content of 2. The ammonia cracking catalyst of claim 1.

5. The yttrium and potassium are contained in the catalyst in an amount of 0.01 to 0.05 wt % / m ２ It exists uniformly with a content of 2. The ammonia cracking catalyst of claim 1.

6. The weight ratio of (yttrium + potassium) / ruthenium is in the range of 4 to 8, the weight ratio of yttrium / ruthenium is 1 to 2, and the weight ratio of potassium / ruthenium is 3 to 6.

2. The ammonia cracking catalyst of claim 1.

7. A method for producing a catalyst for use in an ammonia cracking reaction, comprising: a) heat treating spherical bohemite (AlOOH) at a temperature in the range of 750-900°C to produce an alumina support having a delta crystalline phase; b) Produced delta alumina (δ-Al ２ O ３ ) ３ ) on the support. ３ ) ３ ) is mixed and dissolved in a solvent, and the solution is carried by a pressurized spray method at room temperature; c) drying the supported catalyst at 100 to 120°C and calcining the supported catalyst at 500 to 600°C; d) The prepared yttrium / delta alumina material was treated with a ruthenium precursor (RuCl ３ ) is dissolved in a solvent and the solution is carried by a pressurized spray method at room temperature; e) drying the supported catalyst at 100-120°C and calcining it at 500-600°C, and removing residual Cl by ion exchange; f) Adding a potassium precursor (KNO) to the prepared ruthenium / yttrium / delta alumina material ３ ) dissolved in a solvent is dried at room temperature of 100 to 120°C, and the remaining NO is removed by baking at 500 to 600°C. ３ and removing h) subjecting the prepared potassium / ruthenium / yttrium / delta alumina oxidation catalyst to a rapid reduction process at a high temperature using hydrogen gas at a temperature in the range of 400 to 500°C to prepare a final catalyst. A method for producing an ammonia cracking catalyst comprising:

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