Ammonia decomposition catalyst and method for producing same

Abstract

The present invention relates to an ammonia decomposition catalyst and a manufacturing method thereof, and more particularly to an ammonia decomposition catalyst containing alumina (Al2O3), cerium (Ce), lanthanum (La), ruthenium (Ru) and potassium (K).

Description

[Technical Field]

[0001] The present invention relates to a catalyst for ammonia decomposition and a method for producing the same. [Background technology]

[0002] In order to overcome climate change and various environmental pollution issues, efforts are underway worldwide to restructure carbon-based energy societies into renewable energy-based societies. However, the distribution of renewable energy is uneven depending on region and time, and for the universal use of renewable energy, it is necessary to establish an inter-national or inter-continental trade system that utilizes energy storage devices that can store renewable energy in large quantities.

[0003] Hydrogen is a substance capable of storing large amounts of energy stably for long periods of time, and various countries, including Europe, Japan, Saudi Arabia, and Australia, are working to build a global renewable energy trading system by using hydrogen as a renewable energy storage medium. Meanwhile, the Korean government's Hydrogen Economy Revitalization Roadmap sets a goal of increasing domestic hydrogen supply. However, because hydrogen has a very low energy density relative to its volume, research into chemical and physical hydrogen storage methods is essential in order to economically import large amounts of hydrogen from overseas.

[0004] For this reason, various hydrogen storage materials such as ammonia (NH3), liquid organic hydrogen compounds (LOHCs), and liquefied hydrogen (LH2) are being actively researched. Ammonia in particular is attracting attention as a hydrogen (renewable energy) storage medium with great commercial viability due to its high hydrogen storage capacity (17.6 wt%, 108 g / L), ease of storage (8.74 Kpa, 20°C), and ability to utilize existing ammonia storage and transportation infrastructure.

[0005] One ammonia molecule consists of three hydrogen atoms and one nitrogen atom, and when this ammonia molecule is decomposed at high temperatures, only hydrogen and nitrogen gas, which makes up 78% of air, are produced. Ammonia has the advantage of being able to use existing infrastructure for large-scale storage and long-distance transportation, and in addition, because only hydrogen and nitrogen are produced, carbon dioxide emissions can be minimized.

[0006] However, the biggest problem is that the ammonia decomposition reaction itself takes place at high temperatures and pressures, so a considerable amount of heat must be supplied to heat the reactor. The ammonia decomposition reaction is an endothermic reaction in which two ammonia molecules are decomposed into one nitrogen molecule and three hydrogen molecules, as shown in the following formula, and requires a heat quantity of approximately 46 kJ / mol. 2NH3(g) → N2(g) + 3H2(g)

[0007] The thermodynamic ammonia conversion rate reaches 99.1% at 400°C and 1 atmosphere, but in practice, due to the reaction kinetic energy barrier, the reaction temperature is higher, at 550°C or higher. Therefore, if a solid powder catalyst is used in the reaction, the reaction temperature can be significantly lowered.

[0008] Ruthenium increases the electron density of the catalyst, facilitating nitrogen desorption. The size of the ruthenium metal also affects the degree of reaction activity, with the size of ruthenium showing the best activity in the ammonia dehydrogenation reaction being approximately 3-5 nm. This size of ruthenium metal is known to provide optimal ruthenium-nitrogen bond energy and form a large number of active sites that exhibit high activity in ammonia dehydrogenation.

[0009] The interaction of ruthenium with the alumina support limits the ruthenium agglomeration effect, preventing loss of active sites and reducing loss of active sites due to bulking, where metal particles penetrate into the support.

[0010] On the other hand, the commonly used ruthenium precious metal-based catalyst has high ammonia decomposition activity but is very expensive, which is unfavorable from the viewpoint of process economics. Therefore, there is a need to develop an economical ruthenium catalyst that has a low ruthenium content and exhibits high activity and high durability at temperatures lower than conventional reaction temperatures.

[0011] To date, many ruthenium-based catalysts have been developed both domestically and internationally, but there have been no examples of powder and bead-type ruthenium-based catalysts that have been developed by finely adjusting and experimentally verifying the physicochemical composition and properties to optimize the ruthenium-nitrogen bond energy and ruthenium-support interactions.

[0012] In particular, to efficiently proceed with the ammonia dehydrogenation reaction, it is necessary to promote nitrogen recombination, which is the reaction rate-determining step. For this, an appropriate metal-nitrogen binding energy is required. The size of ruthenium metal also affects the degree of reaction activity, so technological development is needed to obtain the size of ruthenium that shows the best activity in the ammonia dehydrogenation reaction. Summary of the Invention [Problem to be solved by the invention]

[0013] One embodiment of the present invention is to provide a catalyst for ammonia decomposition that can produce high purity hydrogen at temperatures below 500°C.

[0014] Another embodiment of the present invention is to provide an ammonia decomposition catalyst that has excellent ammonia decomposition and hydrogen production capabilities, and is highly active and durable.

[0015] Yet another embodiment of the present invention is to provide a method for producing a catalyst of the above characteristics.

[0016] Yet another embodiment of the present invention is to provide a method for decomposing ammonia using the catalyst of the present invention. [Means for solving the problem]

[0017] According to one aspect of the present invention, there is provided a catalyst for the decomposition of ammonia, comprising alumina (Al2O3), cerium (Ce), lanthanum (La), ruthenium (Ru), and potassium (K).

[0018] According to another aspect of the present invention, there is provided a method for preparing a catalyst for decomposing ammonia, the method comprising the steps of: calcining alumina (Al2O3) to synthesize an alumina support; loading cerium (Ce) on the alumina support to prepare Ce-Al2O3; loading lanthanum (La) on the Ce-Al2O3 to prepare La-Ce-Al2O3; loading ruthenium (Ru) on the La-Ce-Al2O3 to prepare Ru / La-Ce-Al2O3; and mixing and loading potassium (K) on the Ru / La-Ce-Al2O3 to prepare K-Ru / La-Ce-Al2O3. [Effects of the Invention]

[0019] The ammonia decomposition catalyst according to the present invention has excellent hydrogen production capability at temperatures of 550° C. or less, and has high catalytic activity and durability. The ammonia decomposition catalyst according to one embodiment of the present invention can maximize ammonia decomposition efficiency by optimizing metal-support interaction, and can exhibit higher stability and activity with a smaller ruthenium content at the same reaction temperature and gas space velocity compared to conventional ammonia decomposition catalysts. [Brief explanation of the drawings]

[0020] [Figure 1] 1 is an image of a powder in which alumina is extracted from a catalyst for ammonia decomposition according to an embodiment of the present invention. [Figure 2] 1 shows the results of XPS elemental analysis of alumina extracted from a catalyst for ammonia decomposition according to one embodiment of the present invention. [Figure 3] 1 shows STEM images of an ammonia decomposition catalyst according to an embodiment of the present invention with and without hydrogen reduction treatment. [Figure 4]1 is a graph showing the results of XRD evaluation according to the change in cerium content of the catalyst for ammonia decomposition according to one embodiment of the present invention. [Figure 5] 1 is a graph showing the results of TPR evaluation according to the change in cerium content of the catalyst for ammonia decomposition according to one embodiment of the present invention. [Figure 6] 1 is a graph showing the results of XRD evaluation according to the change in cerium content of the catalyst for ammonia decomposition according to one embodiment of the present invention. [Figure 7] 1 is a graph showing the results of evaluating ammonia decomposition performance depending on the change in cerium content of an ammonia decomposition catalyst according to an embodiment of the present invention. [Figure 8] 1 is a graph showing the results of evaluating the ammonia decomposition performance of an ammonia decomposition catalyst according to one embodiment of the present invention with and without hydrogen reduction treatment. [Figure 9] 1 is a graph showing the results of evaluating ammonia decomposition performance according to the change in lanthanum content of an ammonia decomposition catalyst according to an embodiment of the present invention. [Figure 10] 1 is a graph showing the ammonia decomposition performance evaluation results of a catalyst for ammonia decomposition according to an embodiment of the present invention, depending on the cerium content. [Figure 11] 1 is a graph showing the ammonia decomposition performance evaluation results of ammonia decomposition catalysts according to the type of rare earth metal according to an embodiment of the present invention. [Figure 12] 1 is a graph showing the ammonia decomposition performance evaluation results of ammonia decomposition catalysts according to the type of alkali metal and rare earth metal according to an embodiment of the present invention. [Figure 13] 1 is a graph showing the ammonia decomposition performance evaluation results of a catalyst for ammonia decomposition according to an embodiment of the present invention, depending on the potassium content. [Figure 14] 1 is a graph showing the ammonia decomposition performance evaluation results of a catalyst for ammonia decomposition according to an embodiment of the present invention, depending on the calcination temperature. [Figure 15] 1 is a graph showing the ammonia decomposition performance evaluation results over time of a catalyst for ammonia decomposition according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0021] The present invention will be described in detail below with reference to the accompanying drawings, in which: FIG. 1 is a block diagram of a semiconductor device according to a first embodiment of the present invention; FIG. 2 is a block diagram of a semiconductor device according to a first embodiment of the present invention; FIG. 3 is a block diagram of a semiconductor device according to a first embodiment of the present invention;

[0022] According to the present invention, there is provided a catalyst for ammonia decomposition that can produce high-purity hydrogen at temperatures of 550° C. or less. The catalyst of the present invention is a ruthenium-based catalyst for ammonia decomposition that has very high catalytic activity and durability.

[0023] More specifically, the ammonia decomposition catalyst of the present invention can include alumina (Al2O3), cerium (Ce), lanthanum (La), ruthenium (Ru), and potassium (K).

[0024] Alumina is a catalyst support, and cerium doping can be used to increase the concentration of lattice oxygen active sites and maximize metal-support interaction. The alumina can be gamma-alumina (gamma-Al2O3). When alumina is used as a support, cerium ions (Ce 3+ The stability of the cerium-alumina support is increased, allowing for the formation of more surface lattice oxygen-deficient sites. The optimized cerium-alumina support interaction limits the aggregation of ruthenium metal, prevents ruthenium metal from penetrating the support, and also affects the bond energy between ruthenium and nitrogen, resulting in the synthesis of highly active catalysts.

[0025] The ammonia decomposition catalyst of the present invention may contain 5 to 25 wt %, for example, 6 wt %, of cerium. If the cerium content of the catalyst is less than or exceeds the above range, the catalytic activity may decrease.

[0026] The ammonia decomposition catalyst of the present invention may contain any one of rare earth metals, such as lanthanum (La), gadolinium (Gd), strontium (Sr), yttrium (Y), samarium (Sm), and magnesium (Mg), and more preferably lanthanum. The rare earth metal can suppress the bulking phenomenon in which ruthenium penetrates into the support, thereby preventing the loss of active sites.

[0027] The catalyst for ammonia decomposition of the present invention may contain lanthanum in an amount of 2 to 15 wt %, for example, 4 wt %. If the lanthanum content of the catalyst is less than or exceeds the above range, the catalytic activity may decrease.

[0028] When lanthanum is supported on Ce-Al2O3, the thermal stability of alumina (Al2O3) increases, preventing ruthenium from becoming bulky, particularly in a high-temperature reducing atmosphere, and suppressing the decrease in active sites.

[0029] The ammonia decomposition catalyst of the present invention may contain 0.1 to 10 wt %, for example, 3 wt %, of ruthenium. If the ruthenium content of the catalyst is less than or exceeds the above range, the catalytic activity may decrease.

[0030] The ammonia decomposition catalyst of the present invention may contain an alkali metal, such as either potassium (K) or cesium (Cs), which increases the electron density of ruthenium and weakens the bond energy between ruthenium and nitrogen, thereby providing a highly active catalyst.

[0031] The ammonia decomposition catalyst of the present invention may contain 1 to 15 wt %, for example, 7 wt %, of potassium. If the potassium content of the catalyst is less than or exceeds the above range, the catalytic activity may decrease.

[0032] When an alkali metal such as potassium or cesium, which has low electronegativity, is added, the electron density of ruthenium can be increased, which can be used to reduce the nitrogen desorption energy and facilitate nitrogen desorption. Therefore, when an alkali metal is added, a highly active catalyst can be synthesized.

[0033] The catalyst for ammonia decomposition of the present invention can be prepared by the steps of: calcining alumina (Al2O3) to prepare an alumina support; loading cerium (Ce) on the alumina support to prepare Ce-Al2O3; loading lanthanum (La) on the Ce-Al2O3 to prepare La-Ce-Al2O3; loading ruthenium (Ru) on the La-Ce-Al2O3 to prepare Ru / La-Ce-Al2O3; mixing and loading potassium (K) on the Ru / La-Ce-Al2O3 to prepare K-Ru / La-Ce-Al2O3; and reducing K-Ru / La-Ce-Al2O3.

[0034] The step of calcining the alumina to synthesize the alumina support may be performed at a temperature of 700° C. to 1200° C., for example, 700° C. If the calcination temperature is below or above the above range, the catalytic activity may be reduced.

[0035] The step of preparing Ce-Al2O3 by supporting cerium on the alumina support may include mixing a cerium precursor with the alumina support, reducing the mixture of the cerium precursor and the alumina support, and calcining the mixture of the cerium precursor and the alumina support. The step of reducing the mixture of the cerium precursor and the alumina support may be performed at a temperature of 500°C to 800°C, for example, 700°C. The step of calcining the cerium precursor may be performed at a temperature of 300°C to 600°C, for example, 350°C.

[0036] The step of reducing the mixture of the cerium precursor and the alumina support may be performed in a hydrogen atmosphere.

[0037] The cerium precursor can be cerium(III) chloride heptahydrate.

[0038] When the mixture of the cerium precursor and the alumina support is reduced before calcination, the chlorine contained in the cerium (III) chloride heptahydrate extracts the aluminum from the alumina support into AlCl3. 3+ The ions are filled and the concentration of cerium increases. 3+ The more ions there are, the easier they are to interact with ruthenium, increasing the electron density. Higher electron density can reduce the ruthenium-nitrogen desorption energy, facilitating nitrogen desorption.

[0039] The step of preparing La-Ce-Al2O3 by supporting lanthanum (La) on Ce-Al2O3 may include mixing a lanthanum precursor with the Ce-Al2O3 and calcining the mixture of the lanthanum precursor and Ce-Al2O3. The calcination of the lanthanum precursor may be performed at a temperature of 300°C to 600°C, for example, 350°C.

[0040] The lanthanum precursor can be lanthanum(III) nitrate hexahydrate.

[0041] The step of preparing Ru / La-Ce-Al2O3 by supporting ruthenium (Ru) on the La-Ce-Al2O3 may include mixing a ruthenium precursor with the La-Ce-Al2O3 and reducing the mixture of the ruthenium precursor and La-Ce-Al2O3. The step of reducing the ruthenium precursor may be performed at a temperature of 400°C to 700°C, for example, 400°C.

[0042] The ruthenium precursor that can be used in the present invention can be at least one selected from the group consisting of ruthenium chloride (RuCl), ruthenium acetylate (Ru(CHO)), ruthenium oxide (RuO), and hydrates thereof, and preferably ruthenium(III) chloride hydrate can be used.

[0043] The step of preparing K-Ru / La-Ce-Al2O3 by mixing and supporting potassium (K) on the Ru / La-Ce-Al2O3 may include mixing a potassium precursor with the Ru / La-Ce-Al2O3 and reducing the mixture of the potassium precursor and Ru / La-Ce-Al2O3. The step of reducing the potassium precursor may be performed at a temperature of 400°C to 700°C, for example, 400°C. The potassium precursor may be potassium nitrate.

[0044] The step of reducing the ammonia decomposition catalyst may be performed at a temperature of 400 to 800°C, for example, 800°C.

[0045] When using the ammonia decomposition catalyst according to the present invention, the metal-support interaction can be optimized to maximize ammonia decomposition efficiency, and higher stability and activity can be exhibited with a smaller ruthenium content at the same reaction temperature and gas space velocity compared to conventional ammonia decomposition catalysts. [Example]

[0046] (Example) The present invention will be described in more detail with reference to the following examples, which are provided to aid in understanding the present invention and are not intended to limit the present invention.

[0047] Example 1 Gamma-alumina (gamma-Al2O3) was calcined in an air atmosphere at 700°C with a heating rate of 5°C / min for 3 hours.

[0048] The calcined gamma-alumina, cerium precursor, cerium(III) chloride heptahydrate, and ultrapure water (DI water) were then mixed in a rotary evaporator and stirred for 2 hours at a bath temperature of 30°C and a pressure of 0.08 MPa. The mixture was then further stirred for 1 hour at temperatures of 40°C, 50°C, 60°C, and 70°C, and finally stirred for 2 hours at a temperature of 80°C until the solution was completely evaporated. The mixture was then separated in a evaporator and dried in a drying oven for at least 12 hours.

[0049] The mixture was then reduced at 700°C in a 100% H2 (hydrogen) atmosphere for 6 hours, with a heating rate of 5°C / min. After reduction, the mixture was calcined at 350°C in an air atmosphere for 3 hours, with a heating rate of 5°C / min. As a result, a Ce-Al2O3 catalyst containing 6 wt% of the total catalyst weight was produced.

[0050] Comparative Example 1 A catalyst was produced in the same manner as in Example 1, except that the reduction was not carried out at a temperature of 700° C. in a 100% H 2 (hydrogen) atmosphere for 6 hours.

[0051] Example 2 A Ce-Al2O3 catalyst was prepared in the same manner as in Example 1, except that 3 wt% of cerium was contained based on the total catalyst weight.

[0052] Example 3 A Ce-Al2O3 catalyst was prepared in the same manner as in Example 1, except that 12.5 wt% of cerium was contained based on the total weight of the catalyst.

[0053] Example 4 A Ce-Al2O3 catalyst was prepared in the same manner as in Example 1, except that it contained 25 wt% cerium based on the total catalyst weight.

[0054] Example 5 A Ce-Al2O3 catalyst was prepared in the same manner as in Example 1, except that 50 wt% of cerium was contained based on the total weight of the catalyst.

[0055] Comparative Example 2 A Ce-Al2O3 catalyst was prepared in the same manner as in Comparative Example 1, except that 3 wt% of cerium was contained based on the total catalyst weight.

[0056] Comparative Example 3 A Ce-Al2O3 catalyst was prepared in the same manner as in Comparative Example 1, except that 12.5 wt% of cerium was contained based on the total weight of the catalyst.

[0057] Comparative Example 4 A Ce-Al2O3 catalyst was prepared in the same manner as in Comparative Example 1, except that 25 wt% of cerium was contained based on the total weight of the catalyst.

[0058] Comparative Example 5 A Ce-Al2O3 catalyst was prepared in the same manner as in Comparative Example 1, except that 50 wt% of cerium was contained based on the total weight of the catalyst.

[0059] Comparative Example 6 An Al2O3 catalyst was produced in the same manner as in Example 1, except that no cerium precursor was added.

[0060] Comparative Example 7 An Al2O3 catalyst was produced in the same manner as in Comparative Example 1, except that no cerium precursor was added.

[0061] Example 6 The catalyst of Example 1 was mixed with a ruthenium precursor, ruthenium(III) chloride hydrate, and ultrapure water and stirred for 2 hours using a rotary evaporator at a bath temperature of 30°C and a pressure of 0.08 MPa. The mixture was then further stirred at temperatures of 40°C, 50°C, 60°C, and 70°C for 1 hour each, and finally stirred at a temperature of 80°C for 2 hours until the solution was completely evaporated. The mixture was then separated using a condenser and dried in a drying oven for 12 hours or more.

[0062] Then, without calcination, the catalyst was immediately reduced at 500°C in a 75% H2 / N2 (hydrogen / nitrogen) atmosphere for 3 hours at a reduction temperature of 5°C / min, resulting in the production of a Ru / Ce-Al2O3 catalyst containing 6 wt% cerium and 2 wt% ruthenium based on the total catalyst weight.

[0063] Example 7 A Ru / Ce-Al2O3 catalyst was prepared in the same manner as in Example 6, except that 12.5 wt% of cerium was contained based on the total catalyst weight.

[0064] Example 8 A Ru / Ce-Al2O3 catalyst was prepared in the same manner as in Example 6, except that 25 wt% of cerium was contained based on the total catalyst weight.

[0065] Comparative Example 8 The catalyst of Comparative Example 6 was mixed with a ruthenium precursor, ruthenium(III) chloride hydrate, and ultrapure water and stirred for 2 hours using a rotary evaporator at a bath temperature of 30°C and a pressure of 0.08 MPa. The mixture was then further stirred at temperatures of 40°C, 50°C, 60°C, and 70°C for 1 hour each, and finally stirred at a temperature of 80°C for 2 hours until the solution was completely evaporated. The mixture was then separated using a condenser and dried in a drying oven for 12 hours or more.

[0066] Then, without calcination, the catalyst was immediately reduced at 500°C in a 75% H2 / N2 (hydrogen / nitrogen) atmosphere for 3 hours, with a reduction temperature increase rate of 5°C. As a result, a Ru / Al2O3 catalyst containing 2 wt% ruthenium based on the total catalyst weight was produced.

[0067] Comparative Example 9 A Ru / CeO2 catalyst was produced in the same manner as in Comparative Example 8, except that CeO2 was used as the support instead of alumina.

[0068] Comparative Example 10 A Ru / CeO2 catalyst was produced in the same manner as in Comparative Example 9, except that the hydrogen reduction treatment was not carried out.

[0069] Comparative Example 11 The catalyst of Comparative Example 9 was mixed with a lanthanum precursor, lanthanum(III) nitrate hexahydrate, and ultrapure water and stirred for 2 hours using a rotary evaporator at a bath temperature of 30°C and a pressure of 0.08 MPa. The mixture was then further stirred at temperatures of 40°C, 50°C, 60°C, and 70°C for 1 hour each, and finally stirred at a temperature of 80°C for 2 hours until the solution was completely evaporated. The mixture was then separated using a evaporator and dried in a drying oven for 12 hours or more.

[0070] Then, the catalyst was calcined at 350°C in an air atmosphere for 3 hours at a temperature increase rate of 5°C. As a result, a Ru / La-CeO2 catalyst containing 6 wt% cerium, 2 wt% ruthenium, and 2 wt% lanthanum based on the total catalyst weight was prepared.

[0071] Comparative Example 12 A Ru / La-CeO2 catalyst was prepared in the same manner as in Comparative Example 11, except that 4 wt% of lanthanum was added based on the total catalyst weight.

[0072] Comparative Example 13 A Ru / La-CeO2 catalyst was prepared in the same manner as in Comparative Example 11, except that 12 wt% of lanthanum was added based on the total catalyst weight.

[0073] Comparative Example 14 A Ru / Al2O3 catalyst was prepared in the same manner as in Comparative Example 8, except that 3 wt% of ruthenium was contained based on the total catalyst weight.

[0074] Example 9 A Ru / Ce-Al2O3 catalyst was prepared in the same manner as in Example 6, except that it contained 3 wt% of ruthenium based on the total catalyst weight.

[0075] Example 10 A Ru / Ce-Al2O3 catalyst was prepared in the same manner as in Example 7, except that it contained 3 wt% of ruthenium based on the total catalyst weight.

[0076] Example 11 The catalyst of Example 1 was mixed with a lanthanum precursor, lanthanum(III) nitrate hexahydrate, and ultrapure water, and stirred for 2 hours using a rotary evaporator at a bath temperature of 30°C and a pressure of 0.08 MPa. The mixture was then further stirred at temperatures of 40°C, 50°C, 60°C, and 70°C for 1 hour each, and finally stirred at a temperature of 80°C for 2 hours until the solution was completely evaporated. The mixture was then separated using a evaporator and dried in a drying oven for at least 12 hours.

[0077] Then, the catalyst was calcined at 350°C in an air atmosphere for 3 hours, with a temperature increase rate of 5°C. As a result, a La-Ce-Al2O3 catalyst containing 6 wt% cerium and 4 wt% lanthanum based on the total catalyst weight was prepared.

[0078] Comparative Example 15 A catalyst was produced in the same manner as in Example 11, except that gadolinium (Gd) was supported instead of lanthanum.

[0079] Comparative Example 16 A catalyst was produced in the same manner as in Example 11, except that strontium (Sr) was supported instead of lanthanum.

[0080] Comparative Example 17 A catalyst was produced in the same manner as in Example 11, except that yttrium (Y) was supported instead of lanthanum.

[0081] Comparative Example 18 A catalyst was produced in the same manner as in Example 11, except that samarium (Sm) was supported instead of lanthanum.

[0082] Comparative Example 19 A catalyst was produced in the same manner as in Example 11, except that magnesium (Mg) was supported instead of lanthanum.

[0083] Example 12 The catalyst of Example 11 was mixed with a ruthenium precursor, ruthenium(III) chloride hydrate, and ultrapure water and stirred for 2 hours using a rotary evaporator at a bath temperature of 30°C and a pressure of 0.08 MPa. The mixture was then further stirred at temperatures of 40°C, 50°C, 60°C, and 70°C for 1 hour each, and finally stirred at a temperature of 80°C for 2 hours until the solution was completely evaporated. The mixture was then separated using a evaporator and dried in a drying oven for 12 hours or more.

[0084] Then, without calcination, the catalyst was immediately reduced at 500°C in a 75% H2 / N2 (hydrogen / nitrogen) atmosphere for 3 hours at a reduction temperature of 5°C / min, resulting in the production of a Ru / La-Ce-Al2O3 catalyst containing 6 wt% cerium, 4 wt% lanthanum, and 3 wt% ruthenium based on the total catalyst weight.

[0085] Example 13 The catalyst of Example 12 was mixed with potassium nitrate (potassium precursor) and ultrapure water and stirred for 2 hours using a rotary evaporator at a bath temperature of 30°C and a pressure of 0.08 MPa. The mixture was then further stirred at temperatures of 40°C, 50°C, 60°C, and 70°C for 1 hour each, and finally stirred at a temperature of 80°C for 2 hours until the solution was completely evaporated. The mixture was then separated using a condenser and dried in a drying oven for 12 hours or more.

[0086] Then, the catalyst was reduced at 500°C in a 75% H2 / N2 (hydrogen / nitrogen) atmosphere for 3 hours at a reduction temperature of 5°C / min, resulting in a K-Ru / La-Ce-Al2O3 catalyst containing 6 wt% cerium, 4 wt% lanthanum, 3 wt% ruthenium, and 7 wt% potassium based on the total catalyst weight.

[0087] Comparative Example 20 A Cs-Ru / La-Ce-Al2O3 catalyst was prepared in the same manner as in Example 13, except that cesium was supported instead of potassium.

[0088] Comparative Example 21 A Ru / Gd-Ce-Al2O3 catalyst was prepared in the same manner as in Example 12, except that gadolinium was supported instead of lanthanum.

[0089] Comparative Example 22 A K-Ru / Gd-Ce-Al2O3 catalyst was prepared in the same manner as in Example 13, except that gadolinium was supported instead of lanthanum.

[0090] Comparative Example 23 A Cs-Ru / Gd-Ce-Al2O3 catalyst was prepared in the same manner as in Comparative Example 20, except that gadolinium was supported instead of lanthanum.

[0091] Example 14 A K-Ru / La-Ce-Al2O3 catalyst was prepared in the same manner as in Example 13, except that 3.5 wt% of potassium was contained based on the total catalyst weight.

[0092] Example 15 A K-Ru / La-Ce-Al2O3 catalyst was produced in the same manner as in Example 14, except that the alumina calcination temperature was 900°C.

[0093] Example 16 A K-Ru / La-Ce-Al2O3 catalyst was prepared in the same manner as in Example 15, except that 7.0 wt% of potassium was contained based on the total catalyst weight.

[0094] Example 17 A K-Ru / La-Ce-Al2O3 catalyst was prepared in the same manner as in Example 15, except that 10.5 wt% of potassium was contained based on the total catalyst weight.

[0095] Example 18 A Ru / La-Ce-Al2O3 catalyst was prepared in the same manner as in Example 12, except that 2 wt% of ruthenium was contained based on the total catalyst weight, and the alumina was calcined at 1000°C.

[0096] Example 19 A Ru / La-Ce-Al2O3 catalyst was produced in the same manner as in Example 18, except that the alumina was calcined at 900°C.

[0097] Example 20 A Ru / La-Ce-Al2O3 catalyst was produced in the same manner as in Example 18, except that the alumina was calcined at 1100°C.

[0098] Example 21 A Ru / La-Ce-Al2O3 catalyst was produced in the same manner as in Example 18, except that the alumina was calcined at 1200°C.

[0099] Comparative Example 24 A Ru / La-Ce-Al2O3 catalyst was produced in the same manner as in Example 18, except that the alumina was not calcined.

[0100] (Experimental example) Experimental Example 1: Increasing the surface cerium concentration ratio by alumina extraction After loading cerium onto an alumina support, aluminum can be extracted by performing a high-temperature reduction treatment before calcining with oxygen. The chlorine (Cl) contained in cerium(III) chloride heptahydrate extracts a powder containing aluminum in the form of AlCl3·xH2O. An image of the extracted powder is shown in Figure 1.

[0101] XPS elemental analysis confirmed that the extracted powder contained aluminum, chlorine, and oxygen. The results of the XPS elemental analysis of the extracted powder are shown in Table 1, and the results of the XRD analysis are shown in Figure 2.

[0102] [Table 1]

[0103] The EDAX elemental analysis results for the catalyst of Example 1, which was calcined in air after hydrogen reduction treatment, are shown in Table 2, and a STEM (Scanning Transmission Electron Microscope) image is shown in Figure 3(a). The EDAX elemental analysis results for Comparative Example 1, which was calcined in air immediately without hydrogen reduction treatment, are shown in Table 3, and a STEM image is shown in Figure 3(b).

[0104] [Table 2]

[0105] [Table 3]

[0106] When comparing the catalyst of Example 1, which was calcined in oxygen after hydrogen reduction treatment, with the catalyst of Comparative Example 1, which was calcined in air immediately without hydrogen reduction treatment, it was confirmed that in the case of Example 1, which was reduced by hydrogen reduction treatment, the aluminum concentration decreased as aluminum was extracted, and the cerium concentration increased relatively.

[0107] Experimental Example 2: Cerium ion (Ce) depending on cerium concentration 3+ ) and an increase in lattice oxygen deficiency sites FIG. 4(a) shows the results of XPS analysis of the catalysts of Examples 1 to 5, and FIG. 4(b) shows the results of XPS analysis of the catalysts of Comparative Examples 1 to 5.

[0108] The catalysts of Examples 1 to 5 and Comparative Examples 1 to 5 have different cerium concentrations, and it can be seen from the graph of XPS analysis results in FIG. 4 that the degree of alumina extraction varies depending on the cerium concentration. In the case of the catalysts of Examples 1 to 5 that were subjected to hydrogen reduction treatment before calcination, the amount of cerium ions (Ce 3+ ) It can be seen that there are many more peaks.

[0109] Figure 5(a) shows the TPR analysis results for the catalysts of Examples 1, 3, and 4 and Comparative Example 6, and Figure 5(b) shows the XPS analysis results for the catalysts of Comparative Examples 1, 3, 4, and 7. The TPR analysis confirmed that the concentration of lattice oxygen-deficient sites on the surface increased when hydrogen reduction treatment was performed before air calcination during the preparation of the Ce-Al2O3 support. The catalysts of Examples 1, 3, and 4, which were hydrogen-reduced, exhibited a cerium reduction peak at a lower temperature than the catalysts of Comparative Examples 1, 3, and 4, which were directly air-calcined without hydrogen reduction treatment. This is believed to be due to the high dispersion of cerium nanoparticles.

[0110] Figure 6 is a graph showing the XRD analysis results for the catalysts of Examples 1, 3, and 4 and Comparative Examples 1, 3, and 4. The XRD analysis results in Figure 6 confirm that no CeO2 peak was observed in the low-cerium catalysts (less than 12.5 wt.%) that were subjected to hydrogen reduction. Additionally, the catalysts with high cerium concentrations of 25 wt.% or more that were calcined in air without hydrogen reduction had even higher cerium concentrations, but the CeO2 peak was either absent or small, due to the high dispersion of nanoparticles.

[0111] Experimental Example 3: Measurement of ammonia decomposition activity depending on cerium concentration and reduction temperature The catalytic activity of Examples 6 to 8 and Comparative Examples 8 and 9 was evaluated by measuring the ammonia conversion rate, and an ammonia dehydrogenation reaction was carried out under the following conditions. -Space velocity (GHSV): 10,000mL / g cat h -Reaction temperature: 375℃, 400℃, 425℃, 500℃ -Reaction pressure: 1 bar -Analytical equipment: Gas chromatography (GC) - TCD: ammonia, nitrogen -Carrier gas: Helium

[0112] After the ammonia dehydrogenation reaction, the unreacted ammonia was analyzed using a gas chromatograph under the following conditions, and the ammonia conversion rate was calculated based on the analysis results, which are shown in FIG.

[0113] Unlike CeO2-supported catalysts, Ce-Al2O3-supported catalysts show a tendency for activity to increase as the reduction temperature increases. The 2 wt.% Ru / Ce12.5-Al2O3 catalyst of Example 15 showed the highest activity under reduction conditions at 700°C. This is thought to be due to the fact that cerium is dispersed at the atomic level through the alumina extraction and calcination method, and remains as nano-CeO2 even after calcination, resulting in an increased content of lattice oxygen-deficient sites.

[0114] Figure 8 is a graph comparing the ammonia conversion rates of the 2 wt.% Ru / Ce-Al2O3 catalysts of Example 7 and Comparative Example 10 with and without hydrogen reduction treatment. It can be seen that the catalyst of Example 7 with 2 wt.% Ru / Ce-Al2O3 that underwent hydrogen reduction treatment was more active than the catalyst of Comparative Example 10 with 2 wt.% Ru / Ce-Al2O3 that was immediately calcined in air without hydrogen reduction treatment. This is due to the effect of CeO2 being dispersed into nanoparticles through hydrogen reduction treatment, which ultimately resulted in CeO2 being reduced to 0. 3+ This means that the concentration of ruthenium increases, forming more lattice oxygen-deficient sites. The strong metal-support interaction weakens the ruthenium-nitrogen bond energy, which can promote the ammonia dehydrogenation reaction.

[0115] Experimental Example 4: Effect of rare earth metal (lanthanum) addition on ammonia decomposition activity For ammonia decomposition reactions in high-temperature reducing atmospheres, the use of reducible oxide supports (e.g., CeO2, TiO2) requires an appropriate strategy to prevent the loss of active sites. Supporting lanthanum on Ce-Al2O3 increases the thermal stability of Al2O3, particularly in high-temperature reducing atmospheres, preventing ruthenium bulking due to excessive Ru-CeO2 interactions and suppressing the loss of active sites. For example, by suppressing the intrusion of ruthenium metal into oxygen-deficient sites in the bulk lattice rather than the surface, the loss of active sites due to ruthenium bulking can be prevented.

[0116] 9 is a graph showing the ammonia decomposition conversion rate at each ruthenium reduction temperature depending on the lanthanum content in Comparative Examples 9 and 11 to 13. The ammonia decomposition conversion rate was measured under the following conditions. -Space velocity: 10,000mL / g cat h -Ru reduction temperature: 500, 600, 700℃ -Reaction temperature: 500℃ -Reaction pressure: 1 bar -Analytical equipment: Gas chromatography (GC) - TCD: ammonia, nitrogen -Carrier gas: Helium

[0117] As can be seen from Figure 9, when an appropriate amount of lanthanum is supported on CeO2, it acts as a structural stabilizer, preventing the loss of active sites on ruthenium particles in a high-temperature reducing atmosphere, thereby maintaining or increasing activity. In particular, when lanthanum is supported at 4 wt.%, it can be seen that the activity of the catalyst is maintained even at high reduction temperatures.

[0118] Experimental Example 5: Optimization of the physicochemical composition of spherical bead catalysts Using the information obtained through Experimental Examples 1 to 4, a spherical bead catalyst was finally prepared.

[0119] 10 is a graph showing the ammonia conversion rates of the catalysts of Comparative Example 14 and Examples 9 and 10. The ammonia conversion rates were measured under the following conditions. -Space velocity: 10,000mL / g cat h -Reaction temperature: 500℃ -Reaction pressure: 1 bar -Analytical equipment: Gas chromatography (GC) - TCD: ammonia, nitrogen -Carrier gas: Helium

[0120] It can be seen that there is no significant difference in the ammonia conversion rate of the spherical bead catalyst when the catalysts supporting 6 wt.% Ce and 12 wt.% Ce are used.

[0121] 11 is a graph showing the ammonia conversion rates of catalysts supporting rare earth metals La, Gd, Sr, Y, Sm, and Mg in Example 11 and Comparative Examples 15 to 19, and the catalyst supporting no rare earth metal in Example 1. Similar to the catalyst activity evaluation in powder form, it was confirmed that the catalyst supporting 4 wt.% lanthanum (La) exhibited the highest catalytic activity.

[0122] Experimental Example 6: Effect of alkali metal (potassium) addition on ammonia decomposition activity When an alkali metal with low electronegativity is used as a promoter, the ruthenium electron density can be increased, thereby increasing the ammonia dehydrogenation activity.

[0123] 12 is a graph showing a comparison of ammonia conversion rates according to the type and content of alkali metals and rare earth metals in Examples 12 and 13 and Comparative Examples 20 to 23. The ammonia conversion rates were measured under the following conditions. -Space velocity: 10,000mL / g cat h -Reaction temperature: 500℃ -Reaction pressure: 1 bar -Analytical equipment: Gas chromatography (GC) - TCD: ammonia, nitrogen -Carrier gas: Helium

[0124] It can be seen that the activity increased when potassium was added, but the ammonia decomposition ability decreased when cesium was added.

[0125] Experimental Example 7: Effect of alumina calcination temperature and alkali metal content on ammonia decomposition activity 13 is a graph comparing the ammonia conversion rates of spherical bead catalysts with different potassium metal contents in Examples 14 to 17. The effect of alkali metal content on ammonia decomposition activity was confirmed under the following conditions with different alumina calcination temperatures. -Space velocity: 10,000mL / gcat h -Reaction temperature: 500℃ -Reaction pressure: 1 bar -Analytical equipment: Gas chromatography (GC) - TCD: ammonia, nitrogen -Carrier gas: Helium

[0126] When the alumina support was heat-treated in an air atmosphere at 900°C for 5 hours, the activity increased by more than 10%, and the highest activity (95.8%) was observed when the potassium concentration was 7.0 wt.%. However, when an excessive amount of potassium (10.5 wt.%) was doped, the activity actually decreased.

[0127] 14 is a graph comparing the ammonia conversion rates of spherical bead catalysts at different alumina calcination temperatures in Examples 19 to 21 and Comparative Example 24. It can be seen that the catalyst supporting 2 wt. % ruthenium exhibits the highest activity at a calcination temperature of 1000°C.

[0128] Experimental Example 8: Long-term durability evaluation The long-term durability of the K-Ru / La-Ce-Al2O3 (K: 7 wt.%, Ru: 3 wt.%, La: 4 wt.%, Ce: 6 wt.%) spherical bead catalyst of Example 13 was evaluated under the following actual plant-scale reaction conditions. -Space velocity: 10,000mL / g cat h -Reaction temperature: 600℃ -Reaction pressure: 8 bar -Analytical equipment: Gas chromatography (GC) - TCD: ammonia, nitrogen -Carrier gas: Helium

[0129] Figure 15 is a graph showing the ammonia conversion rate over 3000 hours for the catalyst of Example 13. As can be seen from Figure 15, the catalyst is a highly stable catalyst with an activity decrease rate of less than 1% over the final 3000 hours.

[0130] Although various embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and it will be apparent to those skilled in the art that various modifications and variations are possible within the scope of the technical idea of ​​the present invention as set forth in the claims. In addition, some components of the above embodiments may be omitted, and the embodiments may be combined with each other.

Claims

1. Alumina (Al ２ O ３ ), cerium (Ce), lanthanum (La), ruthenium (Ru) and potassium (K).

2. 2. The catalyst for ammonia decomposition according to claim 1, which produces hydrogen at a temperature of 550°C or less.

3. 2. The catalyst for ammonia decomposition according to claim 1, comprising 5 to 25 wt % of cerium, 2 to 15 wt % of lanthanum, 0.1 to 10 wt % of ruthenium, and 1 to 15 wt % of potassium, based on the total catalyst weight.

4. Alumina (Al ２ O ３ ) to synthesize an alumina support; Cerium (Ce) is supported on the alumina support to form Ce-Al ２ O ３ producing The Ce—Al ２ O ３ Lanthanum (La) is supported on the ２ O ３ producing The La-Ce-Al ２ O ３ Ruthenium (Ru) is supported on the ２ O ３ producing The Ru / La-Ce-Al ２ O ３ Potassium (K) was mixed and supported on the surface to form K-Ru / La-Ce-Al ２ O ３ and K-Ru / La-Ce-Al ２ O ３ A method for producing a catalyst for ammonia decomposition, comprising the step of reducing

5. 5. The method for preparing a catalyst for ammonia decomposition according to claim 4, wherein the step of synthesizing the alumina support is performed at a temperature of 700 to 1200°C.

6. The Ce—Al ２ O ３ The step of producing mixing a cerium precursor with the alumina support to form a mixture; reducing the mixture; and 5. The method for producing a catalyst for ammonia decomposition according to claim 4, further comprising the step of calcining the reduced mixture.

7. 7. The method for producing a catalyst for ammonia decomposition according to claim 6, wherein the cerium precursor is cerium (III) chloride heptahydrate.

8. The method for producing an ammonia decomposition catalyst according to claim 6, wherein the reduction is carried out at a temperature of 500°C to 800°C.

9. The method for producing an ammonia decomposition catalyst according to claim 6, wherein the calcination is carried out at a temperature of 300°C to 600°C.

10. The La-Ce-Al ２ O ３ The step of producing The lanthanum precursor was ２ O ３ to form a mixture; and The method for producing a catalyst for ammonia decomposition according to claim 4, further comprising the step of calcining the mixture.

11. 11. The method for producing a catalyst for ammonia decomposition according to claim 10, wherein the lanthanum precursor is lanthanum(III) nitrate hexahydrate.

12. The method for producing a catalyst for ammonia decomposition according to claim 10, wherein the calcination is carried out at a temperature of 300°C to 600°C.

13. The Ru / La-Ce-Al ２ O ３ The step of producing The ruthenium precursor was prepared by the La-Ce-Al ２ O ３ to form a mixture; and 7. The method for producing the ammonia decomposition catalyst according to claim 6, further comprising reducing the mixture.

14. The method for producing a catalyst for ammonia decomposition according to claim 13, wherein the ruthenium precursor is ruthenium(III) chloride hydrate.

15. The method for producing a catalyst for ammonia decomposition according to claim 13, wherein the reduction is carried out at a temperature of 400°C to 700°C.

16. The K-Ru / La-Ce-Al ２ O ３ The step of producing The potassium precursor was added to the Ru / La-Ce-Al ２ O ３ to form a mixture; and 5. The method for producing the ammonia decomposition catalyst according to claim 4, further comprising reducing the mixture.

17. The method for producing a catalyst for ammonia decomposition according to claim 16, wherein the potassium precursor is potassium nitrate.

18. The method for producing a catalyst for ammonia decomposition according to claim 16, wherein the reduction is carried out at a temperature of 400°C to 700°C.

19. The method for producing a catalyst for ammonia decomposition according to claim 4, wherein the reduction is carried out at a temperature of 400°C to 800°C.

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