Catalysts for ammonia cracking with high efficiency at low temperature, preparation method therefor, and hydrogen production method using same

Abstract

The present invention relates to a ruthenium-based ammonia cracking catalyst and, specifically, to an ammonia cracking catalyst in which ruthenium as an active metal and potassium as an auxiliary metal are supported on a lanthanum-containing yttria-stabilized zirconia support, and to a preparation method therefor. 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 metal content by adjusting the ratio of ruthenium / potassium, in combination with a lanthanum-containing yttria-stabilized zirconia-alumina support, even with the use of a low content of ruthenium metal, minimizing the contents of chlorine and nitrogen compounds, which are impurities in the catalyst, and designating the position of the active metal in the catalyst.

Description

Catalyst for low-temperature, high-efficiency ammonia cracking reaction, method for producing the same, and method for producing hydrogen using the same

[0001] The present invention relates to a catalyst composition in which a composite metal of ruthenium and potassium is supported on a La-containing yttria-stabilized zirconia (YSZ) support, which is a catalyst for a cracking reaction that produces hydrogen from ammonia and enables high efficiency production of hydrogen at low temperatures, a method for producing the same, and a method for producing hydrogen using the same.

[0002] Various catalysts used in the ammonia cracking reaction process, which produces hydrogen from ammonia as an eco-friendly hydrogen production technology, are being studied, and in particular, as a catalyst that enables operation at a reaction temperature of 300-500℃ in the ship and small ammonia co-firing power generation sectors, the applicant proposed a catalyst by combining a low content of ruthenium with a support and a specific catalyst support (Republic of Korea Patent Application No. 2023-49873).

[0003] However, obtaining high yields of hydrogen at low temperatures still requires the use of catalysts with high ruthenium contents, hindering practical commercial application. The present invention addresses this issue by producing a catalyst using a combination of low ruthenium contents with an alkali metal and a lanthanum-containing yttria-stabilized zirconia support.

[0004] The main purpose of the present invention is to solve the above-mentioned problems, and to provide a catalyst for an ammonia cracking reaction in which a composite metal of ruthenium-potassium is supported on a La-containing yttria-stabilized zirconia support, which can achieve a high ammonia conversion rate and hydrogen production efficiency at low temperatures even with a low ruthenium content, and also to provide a method for producing the same and a method for producing hydrogen through an ammonia cracking reaction using the same.

[0005] In order to achieve the above technical object, the inventors of the present invention manufactured a catalyst using an yttria-stabilized zirconia (hereinafter referred to as La-YSZ) support containing lanthanum metal so that ammonia, which is a reactant, can rapidly diffuse within the catalyst and the product can quickly move out of the catalyst, and manufactured a catalyst so that ruthenium (Ru), which is a main active site, and potassium, which is an alkali metal that can increase the reaction rate of ruthenium, are positioned in a bi-metallic form on the manufactured support so that each metal exhibits its own unique characteristics.

[0006] In the catalyst manufactured according to the present invention, La-YSZ not only plays a role in decomposing and dissociating and adsorbing the H ion of ammonia, but also increases the mobility of the H ion toward Ru, thereby accelerating the production rate of H2, and potassium (K) weakens the strength of the N2 generated after the cracking reaction being adsorbed on the catalyst and induces rapid desorption from the catalyst, thereby increasing the catalytic reaction rate and durability. In addition, it was found that a separate process for removing chlorine and nitrogen compounds remaining in the catalyst during the catalyst manufacturing process is configured to maximize the active sites of ruthenium during the ammonia cracking reaction, thereby exhibiting a high ammonia conversion rate at low temperatures.

[0007] The present invention, which shows the above results, is summarized as follows.

[0008] (1) As a catalyst used to produce nitrogen and hydrogen through ammonia cracking reaction,

[0009] An ammonia cracking catalyst characterized in that the catalyst support uses yttria-stabilized zirconia containing lanthanum metal, includes a bimetallic complex metal of ruthenium as an active metal and potassium as an auxiliary metal, and chlorine and nitrogen compounds in the catalyst are present in an amount of 10 ppm or less relative to the weight of the catalyst.

[0010] (2) An ammonia cracking catalyst characterized in that the support is formed into a shape by supporting lanthanum on yttria-stabilized zirconia, the content of yttria in the yttria-stabilized zirconia support being 5 to 14 wt% relative to the weight of the support, and lanthanum is supported on the yttria-stabilized zirconia support at 1 to 5 wt%.

[0011] (3) The yttria-stabilized zirconia support containing the above lanthanum metal has a volume density of 0.5 to 1.2 g / ml and a specific surface area of ​​20 to 100 m 2 / g, pore volume is 0.1 to 0.2 cm 3 / g, an ammonia cracking catalyst characterized by an average pore size distribution in the range of 9 to 20 nm.

[0012] (4) An ammonia cracking catalyst characterized in that ruthenium among the metals in the manufactured catalyst is distributed within 30% of the depth from the catalyst periphery to the center, and potassium is uniformly distributed inside the catalyst.

[0013] (5) Among the metals in the above-mentioned manufactured catalyst, 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 depth from the catalyst periphery to the center. 2 The content per specific surface area of ​​the catalyst is 4 to 10 wt%, and potassium is 0.01 to 0.07 wt% / m in the support. 2 An ammonia cracking catalyst characterized by having a uniform content per surface area.

[0014] (6) An ammonia cracking catalyst characterized in that the weight ratio of potassium / ruthenium among the metals in the manufactured catalyst is in the range of 3 to 6.

[0015] (7) An ammonia cracking catalyst characterized in that residual chlorine compounds in the above-mentioned manufactured catalyst are removed to 10 ppm or less based on the total catalyst weight by using an ion exchange method using a basic substance, and nitrogen compounds are removed to 10 ppm or less based on the total catalyst weight by using a high-temperature heat treatment method.

[0016] (8) A specific method for manufacturing a catalyst used in an ammonia cracking reaction,

[0017] a) A step of preparing YSZ powder by co-precipitating yttria (Y2O3) in a solution in which a zirconium precursor (ZrOCl2) is dissolved in a solvent and calcining at 800-1000°C;

[0018] b) A step of impregnating a solution of a lanthanum precursor (La(NO3)3) dissolved in a solvent onto the manufactured YSZ powder support;

[0019] c) A step of removing residual NO3 by drying the powder containing La at 100-120°C and calcining it at 500-600°C, and then molding it;

[0020] d) A step of applying a solution of ruthenium precursor (RuCl3) dissolved in a solvent to a La-YSZ molded body by means of pressurized spraying at room temperature;

[0021] e) A step of drying at 100-120℃ and calcining at 400-600℃ after immersion, and a step of removing residual Cl through ion exchange;

[0022] f) A step of applying a solution of potassium precursor (KNO3) dissolved in a solvent to the manufactured Ru / La-YSZ molded body by pressurized spraying at room temperature;

[0023] g) A step of removing residual NO3 through drying at 100-120℃ and calcination at 500-600℃ after soaking;

[0024] h) A step of manufacturing the final catalyst by subjecting the manufactured Ru-K / La-YSZ oxidation catalyst to a rapid reduction process at high temperature using hydrogen gas within the range of 400-600°C.

[0025] A method for producing an ammonia cracking catalyst, characterized in that it comprises:

[0026] (9) Used in ammonia cracking reaction to produce ammonia gas at a reaction temperature of 300-550℃ with a gas space velocity of 2,000-20,000h -1 An ammonia cracking catalyst characterized by reacting under conditions and exhibiting a high ammonia conversion rate.

[0027] 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, such as 400°C, compared to a catalyst having the same ruthenium metal content, by controlling the ratio of ruthenium / potassium together with a lanthanum-containing yttria-stabilized zirconia-alumina support, minimizing the content of chlorine and nitrogen compounds, which are impurities in the catalyst, and designating the position of the active metal in the catalyst, even when using a low content of ruthenium metal.

[0028] Figure 1 is a flowchart illustrating the manufacturing method steps of Example 1 of the present invention.

[0029] Figure 2 is an electron microscope (video microscopy) and electron probe X-ray microanalyzer (EPMA) photograph of the catalyst manufactured in Example 1 of the present invention.

[0030] The present invention relates to an ammonia cracking catalyst for hydrogen production, and more particularly, to a catalyst comprising a process for producing yttria-stabilized zirconia doped with lanthanum metal, wherein ruthenium is selected as an active metal and potassium as an auxiliary element, and removing chlorine and nitrogen compounds derived from a metal precursor remaining in the catalyst.

[0031] In this case, the hydrogen ions dissociated through the combination of lanthanum and the support were able to rapidly generate hydrogen by ruthenium, and if this reaction continues, the ruthenium particle size gradually increases due to sintering, which reduces the cracking conversion rate. In order to prevent this sintering phenomenon, it was found that potassium can be strongly combined with ruthenium to suppress the particle growth of ruthenium during the reaction and play a role in increasing the durability of the catalyst.

[0032] In addition, when the active metal is generally distributed throughout the support, the contact frequency between the reactant and the support / active metal decreases, resulting in a loss in the amount of hydrogen produced per unit time (ammonia conversion rate). To solve this problem, ruthenium is positioned on the surface of the support, and the hydrogen production is designed to be increased by the ruthenium concentrated on the catalyst surface even when the reactant is introduced into the reactor at a high space velocity. In the case of lanthanum and potassium, the catalyst is manufactured by uniformly distributing them within the support to maximize their interaction with the alumina support.

[0033] Hereinafter, preferred embodiments of the present invention will be described in detail.

[0034] A composite metal catalyst in the form of a ruthenium-assisted metal supported on a thermally modified La-YSZ carrier with controlled pore characteristics used in an ammonia cracking reaction is manufactured through the following steps.

[0035] a) A step of preparing YSZ powder by co-precipitating yttria (Y2O3) in a solution in which a zirconium precursor (ZrOCl2) is dissolved in a solvent and calcining at 800-1000°C;

[0036] b) Lanthanum precursor (La(NO)) was added to the manufactured YSZ powder support. 3)3 ) is impregnated with a solution dissolved in a solvent;

[0037] c) A step of removing residual NO3 by drying the powder containing La at 100-120°C and calcining it at 500-600°C, and then molding it;

[0038] d) A step of applying a solution of ruthenium precursor (RuCl3) dissolved in a solvent to a La-YSZ molded body by means of pressurized spraying at room temperature;

[0039] e) A step of drying at 100-120℃ and calcining at 400-600℃ after immersion, and a step of removing residual Cl through ion exchange;

[0040] f) A step of applying a solution of potassium precursor (KNO3) dissolved in a solvent to the manufactured Ru / La-YSZ molded body by pressurized spraying at room temperature;

[0041] g) A step of removing residual NO3 through drying at 100-120℃ and calcination at 500-600℃ after soaking;

[0042] h) A step of manufacturing a final catalyst by subjecting the manufactured Ru-K / La-YSZ oxidation catalyst to a rapid reduction process at high temperature using hydrogen gas within the range of 400-600 degrees.

[0043] In the above step a), the yttria-stabilized zirconia (YSZ) can be manufactured and used as a material containing 5 to 14 wt% of yttria in zirconia. The manufacturing method is to generate a double metal hydroxide through a coprecipitation reaction of yttria in a zirconia salt, and then position the yttria within the zirconia framework through a heat treatment process. After the heat treatment, the powder undergoes a phase change into a material with a different pattern from the original zirconia crystal phase. Yttria is manufactured in an amount of 5 to 14 wt%. If it is more than 14 wt%, a yttria-only crystal phase exists, lowering the purity of the YSZ. If it is less than 5 wt%, it has more of the properties of zirconia, so it cannot have the yttria-supporting effect.

[0044] In the step b), as the lanthanum precursor, one of lanthanum nitrate hydrate, lanthanum chloride hydrate, lanthanum acetate hydrate, and lanthanum sulfate hydrate can be used, and preferably, lanthanum nitrate that can increase the dispersion of lanthanum can be used for production. The lanthanum precursor can be produced by dissolving it in a solvent such as ionized water or dihydric alcohol such as ethanol or ethylene glycol in an amount equal to the pore volume of the carrier and supporting it on the carrier using an impregnation method. The lanthanum precursor can be supported in an amount of 1 to 5 wt% based on the final catalyst. If it is supported in an amount of less than 1 wt%, it is difficult to realize catalytic performance, and if it is supported in an amount of more than 5 wt%, the lanthanum precursor cannot be introduced into the carrier and accumulates on the surface of some of the carrier, which may result in low ruthenium activity, resulting in reduced durability.

[0045] In the above step c), the La-YSZ powder manufactured in step b) may be manufactured by including a step of drying at 100-120°C and then heat-treating at 500-600°C to remove moisture and precursor materials derived from the metal precursor. The heat-treatment temperature can be performed within an appropriate range as is common knowledge, so a detailed description thereof will not be provided. However, it is preferable to perform the heat treatment at a temperature higher than the reaction temperature so that deformation of the metal in the catalyst does not occur during the ammonia cracking reaction. Thereafter, the La-YSZ powder is molded into a specific shape through a molding process to be used as a catalyst support, and the shape may be a sphere, a cylinder, a pellet, a tube, etc., and these shapes may be manufactured by methods such as oil-drop, tumbling, tabletting, and extrusion.

[0046] The La-YSZ support manufactured above has a volume density of 0.5 to 1.2 g / ml and a specific surface area of ​​20 to 100 m 2 / g, pore volume is 0.1 to 0.2 cm 3 / g, the average pore size distribution is 9 to 20 nm, and the pore characteristics according to the heat treatment temperature are shown in Table 1.

[0047] Table 1 (Pore characteristics according to heat treatment temperature of La-YSZ)

[0048]

[0049] In the step d), as the ruthenium precursor, one of ruthenium nitrate hydrate, ruthenium chloride hydrate, ruthenium acetate hydrate, ruthenium hydroxide hydrate, and ruthenium nitrosyl nitrate hydrate may be used, and preferably, ruthenium chloride, which can increase ruthenium dispersibility, may be used for the preparation. The active metal precursor may be prepared by dissolving it in a solvent such as ionized water or dihydric alcohol such as ethanol or ethylene glycol in an amount equal to the pore volume of the carrier and supporting it on the carrier using a pressurized spray method. The ruthenium precursor may be supported at a level of 0.5 to 3 based on the weight ratio, and preferably at a level of 1 to 2 for commercial applications.

[0050] In the above step e), the Ru / La-YSZ material manufactured in step d) may be manufactured by including a step of drying at 100-120°C and then heat-treating at 400-600°C in an air atmosphere to remove moisture and precursor materials derived from the metal precursor. The heat-treating temperature can be performed within an appropriate range as is common knowledge, and thus will not be described in detail further. In addition, when ruthenium chloride is used among the metal precursor materials, since chloride ions may remain even after the heat-treating, a process of removing them by an ion exchange method using a base material may be added. The base material may be one of ammonium hydroxide, ammonium nitrate, sodium hydroxide, and sodium nitrate, and preferably, ammonium hydroxide, which is easy to clean, can be used.

[0051] In the step f), as the potassium precursor, one of potassium nitrate hydrate, potassium chloride hydrate, potassium acetate hydrate, and potassium hydroxide hydrate may be used, and preferably, potassium nitrate, which can increase ruthenium dispersibility, may be used for production. The potassium precursor may be produced by dissolving it in a solvent such as ionized water or dihydric alcohol, such as ethanol or ethylene glycol, in an amount equal to the pore volume of the carrier and supporting it on the carrier using a pressurized spray method.

[0052] The potassium precursor may be loaded at 4 to 10 wt% based on the final catalyst. If loaded at less than 4 wt%, it is difficult to realize catalytic performance, and if loaded at more than 10 wt%, the potassium precursor may not be incorporated into the carrier and may accumulate on some of the carrier surface, resulting in low ruthenium activity, which may result in reduced durability. The potassium precursor may be loaded at a level of 3 to 6 based on the potassium / lutetium weight ratio, and preferably, it may be manufactured at a level of 3 to 4 based on the potassium / lutetium weight ratio.

[0053] In the above step g), the K-Ru / La-YSZ material manufactured in step f) may be manufactured by including a step of drying at 100-120°C and then heat-treating at 500 to 600°C in an air atmosphere to remove moisture and precursor material derived from the metal precursor. The heat-treating temperature can be performed within an appropriate range as is common knowledge, and thus will not be described in detail further.

[0054] In the step h), in order to develop catalytic activity in the K-Ru / La-YSZ oxide manufactured in step g), a rapid reduction process is performed using hydrogen gas within the range of 400 to 600°C, preferably within the range of 400 to 500°C, to obtain the final catalyst. If the reduction temperature is lower than 400°C during the reduction process, the metal oxide species may not be completely reduced, and if the reduction temperature is higher than 600°C, agglomeration and sintering of the metal particles may occur, which may result in a decrease in the active sites. In the reduction process, the catalyst was manufactured by heating in a nitrogen atmosphere to the target temperature in a stepwise manner and then flowing hydrogen gas. If two or more active metal species are contained in the catalyst, if it is directly exposed to hydrogen gas at a high temperature as in the reduction method, the active metal species can be manufactured in an alloy form instantly. However, if the temperature is gradually increased from room temperature in a hydrogen atmosphere for reduction, each metal is reduced according to its own oxygen desorption temperature, making it difficult to form an alloy.

[0055] In addition, the catalyst manufactured in the present invention can be used in the cracking reaction of ammonia gas after being introduced into a reactor, and ammonia gas can be cracked at a reaction temperature of 300 to 550°C at a gas hourly space velocity (GHSV) of 2,000 to 20,000 h -1 Hydrogen can be produced by a gas-phase reaction under these conditions. Since the amount of hydrogen produced increases proportionally with increasing gas space velocity, the optimal value can be arbitrarily adjusted based on the reactor volume and catalyst amount, and is not limited to a specific value within the range.

[0056] The reactor that produces hydrogen by the above reforming reaction is not particularly limited, but a fixed-bed catalytic reactor in which a catalyst is filled inside the reactor can be used. In addition, since the cracking reaction is an endothermic reaction, it is important for the catalytic reactor to always maintain an adiabatic state. It is important for the cracking reaction process of the present invention to proceed with the reaction while maintaining the reaction conditions, i.e., reaction temperature, pressure, and gas space velocity, within an appropriate range. If the reaction temperature is less than 300°C, the cracking reaction does not proceed sufficiently, resulting in a very low amount of hydrogen. On the other hand, if the reaction temperature is 550°C or higher, energy costs increase for commercial applications, resulting in low efficiency.

[0057] The technical configuration of the present invention will be described in detail with reference to the following drawings, examples, and comparative examples.

[0058] Example 1

[0059] The yttria-stabilized zirconia (YSZ) support used in Example 1 was manufactured by precipitating yttria (Y2O3) as a hydroxide using ammonia water (NH4OH) in an aqueous solution of zirconyl chloride (ZrOCl2), and then washing, drying, and heat-treating at 800°C. The yttria content in the manufactured YSZ powder was 14 wt%.

[0060] First, lanthanum was used as a precursor for metal loading, and lanthanum nitrate (La(NO3)3.6H2O) was dissolved in water and impregnated into the phase-transferred YSZ support using an impregnation method. After impregnation, an aging process was performed for about 1 hour to ensure that the metal solution was sufficiently distributed throughout the support, and then dried at 120℃ for 12 hours to completely remove moisture within the catalyst. After that, the metal was immobilized through a heat treatment process at 600℃ for 6 hours in an air atmosphere. The manufactured La-YSZ was spheroidized into a 2 mm diameter using a rotating disk assembler and heat-treated at 500℃ to prepare a catalyst support having a bulk density of 0.8 g / ml, a specific surface area of ​​56 m2 / g, a pore volume of 0.19 cm3 / g, and an average pore size distribution of 13.1 nm. Next, ruthenium chloride (RuCl3.xH2O) was used as a precursor to support lutetium, which was used as the main active metal, and this was dissolved in water and impregnated into La-YSZ using a spray loading method. The manufactured Ru / La-YSZ was dried at 120℃ for 12 hours to completely remove moisture in the catalyst, and then heat-treated at 600℃ for 6 hours in an air atmosphere to immobilize the metal. Subsequently, the remaining chloride component in the heat-treated Ru / La-YSZ oxide was ion-exchanged with ammonium chloride using ammonia water, and then washed / removed.

[0061] Next, potassium nitrate (KNO3) was also supported on the Ru / La-YSZ oxide by a spray support method, and finally, the metal-supported K-Ru / La-YSZ composition was heat-treated in an air atmosphere at 550°C for 4 hours to produce a metal-supported 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 while flowing hydrogen gas to produce a catalyst. The overall manufacturing sequence and method are shown in Fig. 1.

[0062] The catalyst manufactured in Example 1 was confirmed to contain 2 wt% lanthanum, 1.7 wt% ruthenium, 6.8 wt% potassium, 4 ppm chloride ions, and 0 ppm nitrate ions. In addition, lanthanum and potassium were uniformly distributed within the support, and ruthenium was manufactured to be distributed to a depth of approximately 30% from the periphery of the catalyst. The metal distribution within the catalyst manufactured in Example 1 is shown in Fig. 2.

[0063] Example 2

[0064] Example 2 was performed in the same manner as Example 1 to manufacture a catalyst, except that the metal content of the final catalyst was such that it contained 2 wt% of lanthanum, 1.7 wt% of lutetium, and 10.2 wt% of potassium.

[0065] Example 3

[0066] Example 3 was performed in the same manner as Example 1 to manufacture a catalyst, except that the metal content of the final catalyst was such that it contained 2 wt% of lanthanum, 1.7 wt% of lutetium, and 1.7 wt% of potassium.

[0067] Example 4

[0068] Example 4 was performed in the same manner as Example 1, except that the yttrium content in the support was 9 wt%, thereby producing a catalyst.

[0069] Example 5

[0070] Example 5 was performed in the same manner as Example 1, except that the yttrium content in the support was 5 wt%, thereby producing a catalyst.

[0071] Example 6

[0072] Example 6 was performed in the same manner as Example 1 to manufacture a catalyst, except that the metal content of the final catalyst was prepared to contain 2 wt% of lanthanum, 0.5 wt% of lutetium, and 2.0 wt% of potassium.

[0073] Example 7

[0074] Example 7 was performed in the same manner as Example 1, except that the lanthanum content of the final catalyst was 5 wt%, thereby producing a catalyst.

[0075] Example 8

[0076] Example 8 was performed in the same manner as Example 1, except that the lanthanum content of the final catalyst was 1 wt%, thereby producing a catalyst.

[0077] Comparative Example 1

[0078] Comparative Example 1 was prepared by the same method as Example 1, except that the final catalyst contained 2 wt% of lanthanum and 3.0 wt% of lutetium, and potassium was not supported.

[0079] Comparative Example 2

[0080] Comparative Example 2 was performed in the same manner as Example 1, except that lanthanum was not supported on the yttria-stabilized zirconia support, thereby producing a catalyst.

[0081] Comparative Example 3

[0082] Comparative Example 3 was performed in the same manner as Example 1, except that alumina was used as a support and lanthanum was not supported, thereby producing a catalyst.

[0083] Comparative Example 4

[0084] Comparative Example 4 was performed in the same manner as Example 1, except that lanthanum-containing alumina was used to manufacture a catalyst.

[0085] The material composition and active metal composition of the catalysts in the above examples and comparative examples are summarized in Table 2.

[0086]

[0087] Example reaction

[0088] The performance of the catalyst manufactured as in the above example was evaluated as follows. To measure the catalytic activity, a cracking reaction was performed using ammonia gas, and the reactor was evaluated using a fixed-bed reaction system. 3 ml of the catalyst was charged into a tubular reactor, and before performing the reaction, hydrogen gas was constantly flowed at 10 cc / min to remove oxygen species on the catalyst surface, and the catalyst was reduced at 400°C for 1 hour. Then, the temperature of the reactor was constantly maintained at 300°C, 400°C, 450°C, and 500°C, and ammonia gas, which was the raw material for the reaction, was continuously supplied to the reactor at a constant rate of 100 cc / min, and the gas space velocity was 2,000 h -1 The reaction pressure was fixed at a constant level. The reaction pressure was evaluated under atmospheric pressure conditions. The substance produced after the reaction was transferred to GC (Gas chromatography) through the injection line and quantitatively analyzed using TCD (thermal conductivity detector).

[0089] The conversion rate of ammonia for the reactants was calculated based on the following criteria, and the activities of the catalysts were compared.

[0090] Conversion rate of ammonia (%) = [number of moles of ammonia before reaction - number of moles of ammonia after reaction] / [number of moles of ammonia before reaction] × 100

[0091] <Comparison of activity evaluations from Examples 1 to 4>

[0092] For each of the examples and comparative examples, an ammonia cracking reaction was performed at a temperature change of 300°C to 500°C, and the results are shown in Table 3. /

[0093]

[0094] These catalysts have in common the following characteristics: ruthenium, the primary active metal, is positioned approximately 30% from the catalyst periphery to increase the rate of hydrogen production from the reactants; lanthanum and potassium, the supporting elements, are uniformly distributed within the catalyst to maximize interaction with the alumina support; and chlorine and nitrogen compounds, which are impurities within the catalyst, are all removed.

[0095] Examples 1 to 3 are the contents of manufacturing catalysts according to the amount of potassium in the subsidy, and the potassium / ruthenium weight ratio was manufactured from 1 to 6. As a result of the activity evaluation, the catalyst of Example 1 with a potassium / ruthenium weight ratio of 4 showed the highest activity, and it was found that when the potassium / ruthenium weight ratio was too high, the ruthenium active site was covered by potassium, preventing the desired ammonia cracking reaction from occurring, and also when the amount of potassium was too small, it was found that the synergistic effect due to mutual bonding with ruthenium could not be observed.

[0096] Examples 1 and 4 and 5 are the results of manufacturing catalysts according to the difference in the amount of yttrium contained in the support, and it was found that the ammonia cracking ratio increased as the yttrium content increased.

[0097] Examples 7 and 8 show the preparation of catalysts according to changes in the content of lanthanum in the support, and it was found that when the content of lanthanum is too high or too low, it cannot have a significant effect on the activity.

[0098] Comparative Example 1 is a catalyst manufactured by increasing only the main active metal ruthenium to 3 wt% without supporting potassium as a support. Despite the increased ruthenium loading, the conversion rates at 400°C and 500°C do not reach 100%. However, the catalyst of Example 1, which additionally supported potassium at a ruthenium content of 1.7 wt%, which is lower than that of Comparative Example 1, showed a higher ammonia conversion rate than the catalyst of Comparative Example 1, indicating that the combination of ruthenium and a support can contribute to greatly increasing the reaction activity in addition to its role as a support.

[0099] Example 1 and Comparative Example 2 are the contents of manufacturing catalysts depending on the presence or absence of lanthanum, which is an auxiliary element, added to the catalyst support, and the results of the activity evaluation showed that the catalyst of Example 1 had a 12% higher ammonia conversion rate at 450°C than that of Comparative Example 2. This shows that lanthanum has an effect on increasing the ammonia conversion rate at low temperatures, and is ultimately used as a factor that can increase the overall reaction conversion rate.

[0100] Example 1 and Comparative Examples 3 and 4 are the contents of manufacturing catalysts by changing the material of the catalyst support, and the results of the activity evaluation show that in the low-temperature region at 400°C, a catalyst using a La-YSZ support shows a significant increase in activity compared to a catalyst using alumina and lanthanum-containing alumina as a support, indicating that the support metal plays a role in promoting the ammonia decomposition reaction.

[0101] Thus, as in Example 1, a catalyst was prepared using a potassium / ruthenium weight ratio of 4.0 on a lanthanum-containing yttria-stabilized zirconia support, thereby producing a catalyst exhibiting a high ammonia cracking conversion rate at a relatively low temperature of 300-500°C.

Claims

1. As a catalyst used in ammonia cracking reaction, An ammonia cracking catalyst characterized in that yttria-stabilized zirconia (La-YSZ) containing lanthanum is used as a support, a bimetallic composite metal of ruthenium as an active metal and potassium as an auxiliary metal is supported, and chlorine and nitrogen compounds in the catalyst are present in an amount of 10 ppm or less relative to the weight of the catalyst.

2. An ammonia cracking catalyst characterized in that, in the first paragraph, the support is formed into a shape by supporting lanthanum on yttria-stabilized zirconia.

3. An ammonia cracking catalyst characterized in that, in the first paragraph, lanthanum is supported on yttria-stabilized zirconia at 1 to 5 wt%.

4. An ammonia cracking catalyst characterized in that, in the first paragraph, the content of yttria in the yttria-stabilized zirconia support is 5 to 14 wt% relative to the weight of the support.

5. In the first paragraph, the yttria-stabilized zirconia support containing lanthanum has a volume density of 0.5 to 1.2 g / ml and a specific surface area of ​​20 to 100 m 2 / g, pore volume is 0.1 to 0.2 cm 3 / g, an ammonia cracking catalyst characterized by an average pore size distribution in the range of 9 to 20 nm.

6. An ammonia cracking catalyst according to claim 1, characterized in that ruthenium is distributed within 30% of the length from the catalyst periphery to the center, and potassium is uniformly distributed inside the catalyst.

7. In the first paragraph, 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 catalyst periphery to the center. 2 An ammonia cracking catalyst characterized by the presence of a content of .

8. In the first paragraph, the potassium is 4 to 10 wt% based on the weight of the catalyst, and 0.01 to 0.07 wt% / m in the catalyst. 2 An ammonia cracking catalyst characterized by the presence of a uniform content of .

9. An ammonia cracking catalyst according to claim 1, characterized in that the weight ratio of potassium / ruthenium is in the range of 3 to 6.

10. An ammonia cracking catalyst according to claim 1, characterized in that the residual chlorine compound in the catalyst is removed to 10 ppm or less by an ion exchange method using a basic substance.

11. An ammonia cracking catalyst according to claim 1, characterized in that residual nitrogen compounds in the catalyst are removed to 10 ppm or less using a high-temperature heat treatment method.

12. In a method for manufacturing a catalyst used in ammonia cracking reaction, a) A step of preparing YSZ powder by co-precipitating yttria (Y2O3) in a solution in which a zirconium precursor (ZrOCl2) is dissolved in a solvent and calcining at 800-1000°C; b) A step of impregnating a solution of a lanthanum precursor (La(NO3)3) dissolved in a solvent onto the manufactured YSZ powder support; c) A step of removing residual NO3 by drying the powder containing La at 100-120°C and calcining it at 500-600°C, and then molding it; d) A step of applying a solution of ruthenium precursor (RuCl3) dissolved in a solvent to a La-YSZ molded body by means of pressurized spraying at room temperature; e) A step of drying at 100-120℃ and calcining at 400-600℃ after immersion, and a step of removing residual Cl through ion exchange; f) A step of applying a solution of potassium precursor (KNO3) dissolved in a solvent to the manufactured Ru / La-YSZ molded body by pressurized spraying at room temperature; g) A step of removing residual NO3 through drying at 100-120℃ and calcination at 500-600℃ after soaking; h) A step of manufacturing the final catalyst by subjecting the manufactured Ru-K / La-YSZ oxidation catalyst to a rapid reduction process at high temperature using hydrogen gas within the range of 400-600°C. A method for producing an ammonia cracking catalyst, characterized in that it comprises:

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