Ammonia decomposition catalyst

Abstract

An object of the present invention is to provide an ammonia decomposition catalyst that can efficiently decompose ammonia into hydrogen and nitrogen and has high mechanical strength, as well as a method for producing hydrogen and nitrogen using the ammonia decomposition catalyst. The ammonia decomposition catalyst of the present invention is characterized by comprising: cobalt (A); one or more rare earth elements (B) selected from cerium, yttrium, and lanthanum; one or more alkaline earth metal elements (C) selected from barium and strontium; zirconium (D); and a calcium compound (E), wherein the cobalt (A), rare earth element (B), alkaline earth metal element (C), and zirconium (D) are present in the form of metals or oxides.

Description

Technical Field

[0001] The present invention relates to a high-strength ammonia decomposition catalyst capable of efficiently decomposing ammonia into nitrogen and hydrogen, and a method for producing hydrogen and nitrogen using the ammonia decomposition catalyst. Background Art

[0002] Hydrogen easily forms covalent bonds with other atoms, and upon combustion, the only compound produced is water, which has the characteristic of high heat per unit mass. Therefore, hydrogen is used for desulfurization in oil refining and in the manufacture of petroleum products. In recent years, its demand as a fuel for fuel cells has also been increasing. Industrial gas companies and others often install hydrogen production equipment in users' industrial equipment and supply hydrogen on-site. However, it is expected that the supply of hydrogen from production sites to hydrogen stations and other facilities will gradually increase in the future.

[0003] As a means of transporting hydrogen, the transport of high-pressure hydrogen, the transport of liquefied hydrogen, and the transport of organic hydrides have been studied. However, high-pressure hydrogen and liquefied hydrogen are extremely dangerous in the event of an accident. In addition, regarding the transport of organic hydrides, for example, the reduction of toluene to obtain methylcyclohexane has been studied, and the relatively safe methylcyclohexane is transported and then dehydrogenated at the desired location to obtain hydrogen. However, this method has the following problem: after temporarily producing hydrogen, excess energy is required to reduce toluene and dehydrogenate methylcyclohexane.

[0004] Therefore, ammonia has attracted considerable attention as a hydrogen carrier. Ammonia itself has long been industrially produced, and it easily liquefies even at room temperature, boasting a bulk hydrogen density approximately 1.5 to 2.5 times higher than that of liquefied hydrogen. However, the development of technologies to efficiently produce hydrogen from ammonia after transporting it remains a challenge.

[0005] For example, Patent Document 1 discloses an ammonia decomposition catalyst that does not use precious metals and can efficiently decompose ammonia into hydrogen and nitrogen at a relatively low temperature and a high space velocity in a wide range of ammonia concentrations from low to high concentrations, thereby obtaining high-purity hydrogen. The ammonia decomposition catalyst contains an iron group metal and a metal oxide.

[0006] Patent Document 2 discloses a catalyst comprising: an element selected from nickel, cobalt, and iron; an element selected from strontium and barium; and a lanthanoid element excluding lanthanum and cerium, which is capable of efficiently producing hydrogen from ammonia.

[0007] Patent Document 3 discloses a catalyst comprising: an element selected from nickel, cobalt, and iron; an element selected from strontium and barium; a rare earth element, and magnesium, which is capable of efficiently producing hydrogen from ammonia.

[0008] Patent Document 4 discloses a catalyst comprising cobalt, yttrium, and an alkaline earth metal selected from strontium and barium in a specific ratio, which is capable of efficiently producing hydrogen from ammonia.

[0009] Prior art literature

[0010] Patent Literature

[0011] Patent Document 1: Japanese Patent Application Laid-Open No. 2010-94668

[0012] Patent Document 2: Japanese Patent Application Laid-Open No. 2016-203052

[0013] Patent Document 3: Japanese Patent Application Publication No. 2019-11212

[0014] Patent Document 4: Japanese Patent Application No. 2020-027817 Summary of the Invention

[0015] Problems to be solved by the invention

[0016] As described above, various catalysts for efficiently producing hydrogen by decomposing ammonia have been studied. However, as the amount of hydrogen used increases, ammonia decomposition catalysts with higher efficiency and strength are being sought.

[0017] Therefore, an object of the present invention is to provide an ammonia decomposition catalyst that can efficiently decompose ammonia into hydrogen and nitrogen and has high mechanical strength, and a method for producing hydrogen and nitrogen using the ammonia decomposition catalyst.

[0018] Solutions for solving problems

[0019] The present inventors have conducted intensive studies to solve the above-mentioned problems and have found that an ammonia decomposition catalyst containing a specific calcium compound has excellent ammonia decomposition activity and high mechanical strength, thereby completing the present invention.

[0020] The present invention is described below.

[0021] [1] An ammonia decomposition catalyst, characterized in that it contains:

[0022] Cobalt (A);

[0023] One or more rare earth elements (B) selected from cerium, yttrium and lanthanum;

[0024] One or more alkaline earth metal elements (C) selected from barium and strontium;

[0025] Zirconium (D); and

[0026] one or more calcium compounds (E) selected from calcium carbonate, calcium oxide and calcium hydroxide,

[0027] The aforementioned cobalt (A), rare earth element (B), alkaline earth metal element (C), and zirconium (D) are contained in the form of metal or oxide.

[0028] [2] The ammonia decomposition catalyst according to [1], wherein the content of the cobalt (A) is 30% by mass or more in terms of oxide.

[0029] [3] The ammonia decomposition catalyst according to [1] or [2], wherein the content of the rare earth element (B) is 1% by mass or more and 24% by mass or less in terms of oxide,

[0030] The content of the alkaline earth metal element (C) is 0.1% by mass or more and 10% by mass or less in terms of oxide,

[0031] The content of the zirconium (D) is 0.1% by mass or more and 10% by mass or less in terms of oxide.

[0032] [4] The ammonia decomposition catalyst according to any one of [1] to [3], wherein the content of the calcium compound (E) is 10% by mass or more.

[0033] [5] A method for producing hydrogen and nitrogen, characterized in that it comprises the following steps:

[0034] a step of subjecting the ammonia decomposition catalyst described in any one of [1] to [4] above to a reduction treatment; and

[0035] A process of decomposing ammonia into hydrogen and nitrogen by bringing a gas containing ammonia into contact with the aforementioned ammonia decomposition catalyst that has been subjected to reduction treatment.

[0036] [6] A use of a catalyst for decomposing ammonia, characterized in that:

[0037] The catalyst comprises: cobalt (A); one or more rare earth elements (B) selected from cerium, yttrium, and lanthanum; one or more alkaline earth metal elements (C) selected from barium and strontium; zirconium (D); and one or more calcium compounds (E) selected from calcium carbonate, calcium oxide, and calcium hydroxide.

[0038] The cobalt (A), rare earth element (B), alkaline earth metal element (C) and zirconium (D) are contained in the catalyst in the form of metal or oxide.

[0039] [7] The use according to [6], wherein the content of the cobalt (A) in the catalyst is 30% by mass or more in terms of oxide.

[0040] [8] The use according to [6] or [7], wherein the content of the rare earth element (B) in the catalyst is 1% by mass or more and 24% by mass or less in terms of oxide,

[0041] The content of the alkaline earth metal element (C) in the catalyst is 0.1% by mass or more and 10% by mass or less in terms of oxide,

[0042] The content of the zirconium (D) in the catalyst is 0.1% by mass or more and 10% by mass or less in terms of oxide.

[0043] [9] The use according to any one of [6] to [8], wherein the content of the calcium compound (E) in the catalyst is 10% by mass or more.

[0044]

[10] A method for producing hydrogen and nitrogen, characterized in that it comprises the following steps:

[0045] A step of subjecting an ammonia decomposition catalyst to a reduction treatment, the ammonia decomposition catalyst comprising: cobalt (A); one or more rare earth elements (B) selected from cerium, yttrium, and lanthanum; one or more alkaline earth metal elements (C) selected from barium and strontium; zirconium (D); and one or more calcium compounds (E) selected from calcium carbonate, calcium oxide, and calcium hydroxide, wherein the cobalt (A), rare earth element (B), alkaline earth metal element (C), and zirconium (D) are contained in the form of metals or oxides; and

[0046] A process of decomposing ammonia into hydrogen and nitrogen by bringing a gas containing ammonia into contact with the aforementioned ammonia decomposition catalyst that has been subjected to reduction treatment.

[0047]

[11] The method according to

[10] , wherein the content of the cobalt (A) in the catalyst is 30% by mass or more in terms of oxide.

[0048]

[12] The method according to

[10] or

[11] , wherein the content of the rare earth element (B) in the catalyst is 1% by mass or more and 24% by mass or less in terms of oxide,

[0049] The content of the alkaline earth metal element (C) in the catalyst is 0.1% by mass or more and 10% by mass or less in terms of oxide,

[0050] The content of the zirconium (D) in the catalyst is 0.1% by mass or more and 10% by mass or less in terms of oxide.

[0051]

[13] The method according to any one of

[10] to

[12] , wherein the content of the calcium compound (E) in the catalyst is 10% by mass or more.

[0052] Effects of the Invention

[0053] The ammonia decomposition catalyst of the present invention enables efficient production of hydrogen and nitrogen from ammonia. Furthermore, the ammonia decomposition catalyst of the present invention has a long life due to the high mechanical strength of its molded body and the like. Furthermore, the ammonia decomposition catalyst of the present invention does not contain expensive precious metals as active metals, making it relatively inexpensive. Therefore, the present invention is industrially useful as a technology that contributes to the upcoming hydrogen society. DETAILED DESCRIPTION

[0054] Hereinafter, the present invention will be described in detail. It should be noted that combinations of two or more preferred embodiments of the present invention described below are also preferred embodiments of the present invention.

[0055] The ammonia decomposition catalyst described in the present invention (hereinafter sometimes abbreviated as "the catalyst of the present invention") contains cobalt (A); one or more rare earth elements (B) selected from cerium, yttrium and lanthanum; one or more alkaline earth metal elements (C) selected from barium and strontium; zirconium (D); and one or more calcium compounds (E) selected from calcium carbonate, calcium oxide and calcium hydroxide.

[0056] Catalysts that promote the decomposition of ammonia into hydrogen and nitrogen are broadly classified into precious metal-based catalysts, whose active metals include precious metals such as ruthenium, and base metal-based catalysts, whose active metals do not contain precious metals. Practically, the use of expensive precious metals is undesirable. In the present invention, relatively inexpensive base metals are used as active metals.

[0057] In the catalyst of the present invention, as an active metal, cobalt (A) must be contained. The proportion of cobalt (A) in the catalyst of the present invention is preferably 30% by mass or more in terms of oxide conversion. It can be considered that the proportion of each element is converted in the form of oxides in this application because: the catalyst of the present invention is manufactured by finally calcining in air and at a high temperature, and the metal elements exist in the form of oxides. In addition, the catalyst of the present invention is subjected to reduction treatment before use. In this stage, each metal element is completely reduced, or only a part is reduced, or all are not reduced or based on reduction conditions. As the above-mentioned proportion of cobalt (A), it is preferably 40% by mass or more in terms of oxide conversion, more preferably 45% by mass or more, further preferably 50% by mass or more, in addition, it is preferably 80% by mass or less, more preferably 75% by mass or less, and further preferably 70% by mass or less.

[0058] The content of the rare earth element (B) in the catalyst of the present invention is preferably 1% by mass or more and 24% by mass or less, calculated as oxide. This content is preferably 1.5% by mass or more, more preferably 2% by mass or more, and even more preferably 2.5% by mass or more. It is preferably 20% by mass or less, and more preferably 15% by mass or less or 10% by mass or less.

[0059] As the rare earth element (B), cerium, yttrium, or lanthanum may be used alone or in combination of two or three. The rare earth element (B) is preferably cerium and / or yttrium, more preferably cerium or yttrium.

[0060] The content of the alkaline earth metal element (C) in the catalyst of the present invention is preferably 0.1% by mass or more and 10% by mass or less, calculated as oxide. This content is preferably 0.3% by mass or more, more preferably 0.4% by mass or more, and even more preferably 0.5% by mass or more, and is preferably 5% by mass or less, more preferably 3% by mass or less, and even more preferably 2% by mass or less.

[0061] As the alkaline earth metal element (C), barium or strontium can be used alone, or a combination of barium and strontium can be used. The alkaline earth metal element (C) present in the catalyst of the present invention is more preferably barium. The use of barium has been shown to significantly improve ammonia decomposition performance at low temperatures.

[0062] The content of zirconium (D) in the catalyst of the present invention, calculated as oxide, is preferably 0.1% by mass or more and 10% by mass or less. This content is preferably 0.5% by mass or more, more preferably 1% by mass or more, and preferably 8% by mass or less, more preferably 6% by mass or less.

[0063] The zirconium and / or its oxide is a component that, in addition to possibly functioning as a support in the catalyst of the present invention, also contributes to improving the initial activity and durability of the catalyst as an active metal.

[0064] The catalyst of the present invention must contain one or more calcium compounds (E) selected from calcium carbonate, calcium oxide and calcium hydroxide. The catalysts containing base metals such as iron, nickel and cobalt at a content of more than 30% by mass in the past have the following problem: in order to activate these base metal elements, the volume shrinks during the reduction treatment, and the mechanical strength of the catalyst is reduced. Specifically, the molded catalyst is broken or damaged or peeled off and cannot be filled into the reactor, or even if it can be filled, it cannot be used for a long time. Therefore, by adding aluminum oxide, silicon dioxide, various clay minerals and the like to the catalyst, the mechanical strength can be improved, but the content of the active ingredient is reduced, resulting in a decrease in initial activity or a decrease in durability. In response to this, the catalyst of the present invention contains a calcium compound (E), thereby playing the role of a co-catalyst that promotes the decomposition of ammonia, or does not significantly reduce the ammonia decomposition ability of the catalyst, thereby improving the mechanical strength of the catalyst.

[0065] The content of the calcium compound (E) in the catalyst of the present invention is preferably 10% by mass or more and 65% by mass or less. This content is preferably 15% by mass or more or 20% by mass or more, more preferably 25% by mass or more or 30% by mass or more, and is preferably 60% by mass or less, more preferably 50% by mass or less, and even more preferably 45% by mass or less.

[0066] The catalyst of the present invention preferably contains at least one carrier selected from alumina, silica, titanium dioxide and niobium oxide on the basis of the aforementioned cobalt (A), rare earth element (B), alkaline earth metal element (C), zirconium (D) and calcium compound (E). The content ratio of the carrier in the catalyst of the present invention is preferably 0.1% by mass or more and 15% by mass or less. As the content ratio, it is preferably 0.5% by mass or more or 1% by mass or more, more preferably 1.5% by mass or more, further preferably 2% by mass or more, and preferably 10% by mass or less, more preferably 8% by mass or less, further preferably 6% by mass or less. By including a carrier, it is possible to expect the effect of improving the initial activity and durability of the catalyst of the present invention.

[0067] From the viewpoint of improving ammonia decomposition activity, the specific surface area of ​​the carrier component is preferably 10 m 2 / g or more. As the specific surface area, it is more preferably 20m 2 / g or more, more preferably 100m 2 The upper limit of the specific surface area is not particularly limited, and can be set to 300 m 2 / g or less.

[0068] The content ratio of each metal component in the catalyst of the present invention can be determined from the amount of metal element contained in the raw material compound used for its production, or can be determined by directly measuring the catalyst of the present invention using fluorescent X-rays or the like.

[0069] The specific surface area of ​​the catalyst of the present invention can be set to 1 m 2 / g and above and 300m 2 / g or less. If the specific surface area is 1m 2 / g or more, the gas containing ammonia can flow more smoothly into the catalyst layer. 2 / g or less, the contact area between the gas containing ammonia and the catalyst can be more reliably ensured, and the reaction can proceed more smoothly. As the above-mentioned specific surface area, it is preferably 5m 2 / g or more, more preferably 18m 2 / g or more, and preferably 250m 2 / g or less, more preferably 200m 2 It should be noted that the specific surface area of ​​the catalyst of the present invention can be measured mainly by conventional methods, for example, using a common surface area measuring device such as a fully automatic BET surface area measuring device ("Macsorb HM Model-1201", manufactured by MOUNTECH).

[0070] The particle size (crystallite diameter) of the catalyst component constituting the catalyst of the present invention, especially the active ingredient in the above-mentioned catalyst, i.e., cobalt oxide, can be set to be greater than 3 nm and less than 200 nm. As this particle size, it is preferably greater than 5 nm, more preferably greater than 10 nm, and further preferably less than 150 nm, more preferably less than 100 nm. The above-mentioned particle size can be measured by conventional methods. For example, the catalyst of the present invention can be analyzed by X-ray diffraction, and the crystal structure can be assigned based on the obtained analysis results to obtain the 2θ value, which can be calculated according to the Scherrer formula.

[0071] The shape of the catalyst of the present invention is not particularly limited, and examples thereof include granular, spherical, pelletized, crushed, saddle, ring, honeycomb, monolith, mesh, columnar, and cylindrical shapes.

[0072] The catalyst of the present invention can be produced by conventional methods, such as mixing, evaporation to dryness, coprecipitation, and impregnation. Mixing is particularly preferred. More specifically, the catalyst can be produced by the following method, which is characterized by comprising the following steps:

[0073] A step of dissolving or dispersing a raw material compound containing cobalt (A); one or more rare earth elements (B) selected from cerium, yttrium, and lanthanum; one or more alkaline earth metal elements (C) selected from barium and strontium; and zirconium (D) in a solvent to obtain a solution or dispersion;

[0074] A step of distilling the solvent from the solution or dispersion to obtain a dry product;

[0075] The dried product is calcined to obtain a calcined product.

[0076] One or more calcium compounds (E) selected from the group consisting of calcium carbonate, calcium oxide, and calcium hydroxide are added to the solution or dispersion or mixed with the burned product.

[0077] About the raw material of aforementioned catalyst constituent component, it is not particularly limited, as the raw material compound of cobalt (A), it is possible to use solid compounds such as cobalt oxide, basic cobalt carbonate, cobalt hydroxide, and particularly preferably use the basic cobalt carbonate that can improve the specific surface area of ​​the catalyst manufactured. On the other hand, about the raw material compound of rare earth element (B), alkaline earth metal element (C), zirconium (D), as long as solubility or affinity are demonstrated in the solvent used, it is not particularly limited, and it is possible to enumerate such as nitrate, oxide, hydroxide, carbonate, sulfate, acetate, etc. When manufacturing catalyst by the method for carrying out mixing with aforementioned cobalt compound, it is preferred to use nitrate, sulfate or acetate with water solubility. As solvent, water, nitric acid, hydrochloric acid, buffer solution, etc. can be used, and as solvent, it is particularly preferably water.

[0078] As the raw material compound of the calcium compound (E), any of calcium carbonate, calcium oxide and / or calcium hydroxide can be used. From the perspective of the relationship between the raw material compounds of other essential elements, calcium carbonate is preferably used. It should be noted that when calcium carbonate is used, sometimes a portion of the calcium carbonate may be thermally decomposed to form calcium oxide due to calcination at temperatures above 600°C. Alternatively, it is known that calcium oxide reacts with moisture in the air to form calcium hydroxide. Even if calcium carbonate is used as a raw material, it can be confirmed by XRD spectra that a portion of the catalyst of the present invention exists in the form of calcium oxide or calcium hydroxide.

[0079] The method for drying the solution or dispersion is not particularly limited, but preferably, heating is performed at a temperature of, for example, 80°C to 150°C, preferably 100°C or higher. During drying, reduced pressure may be applied. Furthermore, the degree of drying is not particularly limited; it may be dried to a degree that does not hinder the subsequent firing process. For example, the solution or dispersion may be dried to a degree that forms a slurry or paste, or may be solidified. Preferably, at least 90% by mass of the solvent is removed.

[0080] The firing conditions are not particularly limited and may be adjusted appropriately. For example, firing is preferably performed at a temperature of 200°C to 1000°C for 1 to 10 hours. The firing temperature is preferably 300°C or higher, more preferably 400°C or higher, and preferably 700°C or lower, more preferably 600°C or lower. The firing temperature may be increased continuously or in stages.

[0081] The method for producing hydrogen and nitrogen according to the present invention includes: subjecting the ammonia decomposition catalyst to a reduction treatment; and allowing ammonia-containing gas to contact the reduced ammonia decomposition catalyst to decompose ammonia into hydrogen and nitrogen.

[0082] The catalyst of the present invention is preferably subjected to a reduction treatment until the ammonia decomposition step. By forming metallic cobalt from cobalt oxide, in particular, during the reduction treatment, the ammonia decomposition activity of the catalyst of the present invention can be improved. As reduction treatments, there can be cited methods such as methods using reducing gases such as hydrogen, hydrocarbons, carbon monoxide, and methods using reducing agents such as hydrazine, lithium aluminum hydride, and tetramethylborohydride. From the perspective of being able to continuously carry out the subsequent ammonia decomposition step by simply changing the gas, the method using a reducing gas is preferred. The reducing gas can be diluted with an inert gas such as nitrogen, carbon dioxide, and argon. In the case of dilution, the proportion of the reducing gas in the introduced gas can be appropriately adjusted, for example, it can be set to be greater than 5% by volume and less than 50% by volume.

[0083] The reduction treatment conditions are preferably adjusted to sufficiently reduce the cobalt oxide contained in the catalyst of the present invention. For example, when the catalyst of the present invention is subjected to reduction treatment using a reducing gas, the temperature is preferably adjusted to 300°C to 800°C, more preferably 400°C to 700°C. The reduction treatment duration is preferably 0.5 hours to 5 hours. Even if the reduction during the reduction treatment is insufficient, hydrogen is generated by the decomposition of ammonia, and the catalyst layer is in a reduced state. Therefore, it is believed that the ammonia decomposition activity of the catalyst of the present invention gradually increases.

[0084] Next, a gas containing ammonia is brought into contact with the reduction-treated catalyst of the present invention, thereby decomposing the ammonia into hydrogen and nitrogen. The gas containing ammonia may be ammonia gas or a mixed gas of ammonia and an inert gas. When using a mixed gas, the proportion of ammonia gas in the mixed gas can be, for example, 50% by volume or more and 95% by volume or less, preferably 70% by volume or more.

[0085] The flow rate of the ammonia-containing gas introduced into the catalyst layer containing the catalyst of the present invention can be appropriately adjusted within a range in which ammonia can be effectively decomposed into hydrogen and nitrogen. For example, the space velocity of the ammonia-containing gas relative to the ammonia decomposition catalyst is preferably 1000 h / min. -1The catalyst of the present invention has excellent ammonia decomposition activity and high strength, so the space velocity can be set to 2000h -1 Above, it can be set to 3000h -1 The upper limit of the space velocity is not particularly limited, but is preferably 100,000 h / min from the viewpoint of suppressing the amount of unreacted ammonia. -1 More preferably 50000h -1 Below, more preferably 30000h -1 Below, more preferably 20000h -1 the following.

[0086] The temperature of the ammonia decomposition reaction can be appropriately adjusted within a range that allows ammonia to be effectively decomposed into hydrogen and nitrogen. For example, it can be set to 250°C or higher and 800°C or lower. This temperature is preferably 300°C or higher, more preferably 400°C or higher, and preferably 700°C or lower, and more preferably 600°C or lower. The reaction pressure can be set to 0.1 MPa or higher and 20 MPa or lower in absolute pressure. This reaction pressure is preferably 0.5 MPa or higher, more preferably 0.8 MPa or higher, and preferably 10 MPa or lower. The reaction pressure can be adjusted using a back pressure valve or the like.

[0087] If unreacted ammonia is contained in the gas passing through the catalyst layer, the gas after the reaction can be introduced into a dry adsorbent, a wet scrubber such as a sulfuric acid aqueous solution, etc. to remove and recover the ammonia, and further separate and purify hydrogen, nitrogen, and inert gas.

[0088] Conventionally, methods using iron-based metals such as iron, cobalt, and nickel as active ingredients in addition to precious metals are known as ammonia decomposition catalysts. However, these catalysts have low activity and are not able to provide sufficiently durable materials. In contrast, the catalyst of the present invention exhibits high ammonia decomposition activity at relatively low reaction temperatures, despite not containing precious metals. As a result, ammonia can be decomposed at low temperatures, which can reduce operating costs or the amount of catalyst required, thereby reducing equipment costs. In addition, the catalyst of the present invention has high strength due to the inclusion of a calcium compound (E), in addition to its high activity, and thus has a long life and can also decompose ammonia under pressurized conditions. Therefore, by using the catalyst of the present invention, hydrogen and nitrogen, especially hydrogen, can be produced very efficiently from ammonia.

[0089] This application claims the benefit of priority based on Japanese Patent Application No. 2020-163651, filed on September 29, 2020. The entire contents of the specification of Japanese Patent Application No. 2020-163651, filed on September 29, 2020, are incorporated herein by reference.

[0090] Example

[0091] The present invention will be described in more detail below with reference to the following embodiments. However, the present invention is not limited to the following embodiments and can be implemented with appropriate modifications within the scope of the aforementioned / latter descriptions. These modifications are all included within the technical scope of the present invention.

[0092] Example 1: 73.4Co4Y1Ba1.6Zr / / 20CaCO3

[0093] As an ammonia decomposition catalyst, a catalyst having a composition of 73.4Co4Y1Ba1.6Zr / / 20CaCO3 was prepared by a mixing method. It should be noted that in the composition formulas herein, the numerical values ​​preceding each element represent the mass concentration (%) of the oxide. For example, the catalyst of this example contains 73.4% by mass of cobalt oxide, 4.0% by mass of yttrium oxide, 1.0% by mass of barium oxide, 1.6% by mass of zirconium oxide, and 20% by mass of calcium carbonate.

[0094] Specifically, 2.6 g of yttrium nitrate n-hydrate (anhydrous content: 72.3%) and 0.3 g of barium nitrate are dissolved in 10 g of ion exchange water, and 1.3 g of zirconium oxynitrate aqueous solution (containing 25% zirconium in terms of oxide conversion) is further mixed to obtain a nitrate aqueous solution. 23.9 g of basic cobalt (II) carbonate (metal cobalt content: 44.3%) is placed in a magnetic dish, and the above-mentioned nitrate aqueous solution is added and thoroughly mixed. The mixture is properly mixed with a spatula in a hot water bath set at 95°C to form a concentrated paste. The obtained paste is put into a dryer at 110°C and dried to obtain a dried product. The obtained dried product is put into a calcining furnace, calcined at 200°C for 2 hours, and then calcined at 600°C for 2 hours. 3.9 g of calcium carbonate is added to the obtained calcined product and thoroughly mixed, and crushed to less than 150 μm to obtain a catalyst powder.

[0095] Example 2: 55.1Co3Y0.7Ba1.2Zr / / 40CaCO3

[0096] As an ammonia decomposition catalyst, a catalyst having a composition of 55.1Co3Y0.7Ba1.2Zr / / 40CaCO3 was prepared by a kneading method. Specifically, the catalyst was obtained by the same method as in Example 1, except that the amounts of the raw materials added were changed to 2.0 g of yttrium nitrate n-hydrate (anhydrous content: 72.3%), 0.2 g of barium nitrate, 0.9 g of an aqueous zirconium oxynitrate solution (containing 25% zirconium as oxide), 17.9 g of basic cobalt (II) carbonate (metallic cobalt content: 44.3%), and 7.8 g of calcium carbonate.

[0097] Example 3: 55.1Co3Y0.7Ba1.2Zr / 40CaCO3

[0098] As an ammonia decomposition catalyst, a catalyst having a composition of 55.1Co3Y0.7Ba1.2Zr / 40CaCO3 was prepared by a kneading method. Specifically, 2.6 g of yttrium nitrate n-hydrate (anhydrous content: 72.3%) and 0.3 g of barium nitrate were dissolved in 10 g of ion-exchanged water, and 1.3 g of an aqueous zirconium oxynitrate solution (containing 25% zirconium in terms of oxide) was further mixed to obtain an aqueous nitrate solution. 23.9 g of basic cobalt (II) carbonate (metallic cobalt content: 44.3%) was placed in a magnetic dish, the above-mentioned aqueous nitrate solution was added and mixed, and then 10.5 g of calcium carbonate was added and mixed. The mixture was appropriately mixed with a spatula in a hot water bath set at 95°C to prepare a concentrated paste. The obtained paste was placed in a dryer at 110°C and dried to obtain a dried product. The obtained dried product was placed in a calcining furnace and calcined at 200°C for 2 hours, and then calcined at 600°C for 2 hours. The obtained burned product was pulverized to 150 μm or less to obtain a catalyst powder. The XRD spectrum of the obtained catalyst powder confirmed the presence of calcium carbonate, calcium oxide, and calcium hydroxide as calcium compounds.

[0099] Example 4: 53.5Co3.8Y1Ba1.7Zr / 40CaCO3

[0100] As an ammonia decomposition catalyst, a catalyst having a composition of 53.5Co3.8Y1Ba1.7Zr / 40CaCO3 was prepared by a kneading method. Specifically, the catalyst was obtained by the same method as in Example 3, except that the amounts of the raw materials added were changed to 2.5 g of yttrium nitrate n-hydrate (anhydrous content: 72.3%), 0.3 g of barium nitrate, 1.3 g of an aqueous zirconium oxynitrate solution (containing 25% zirconium as oxide), 17.4 g of basic cobalt (II) carbonate (metallic cobalt content: 44.3%), and 7.8 g of calcium carbonate.

[0101] Example 5: 44.7Co3.1Y0.8Ba1.4Zr / 50CaCO3

[0102] As an ammonia decomposition catalyst, a catalyst having a composition of 44.7Co3.1Y0.8Ba1.4Zr / 50CaCO3 was prepared by a kneading method. Specifically, the catalyst was obtained by the same method as in Example 3, except that the amounts of the raw materials added were changed to 2.0 g of yttrium nitrate n-hydrate (anhydrous content: 72.3%), 0.3 g of barium nitrate, 1.1 g of an aqueous zirconium oxynitrate solution (containing 25% zirconium as oxide), 14.5 g of basic cobalt (II) carbonate (metallic cobalt content: 44.3%), and 9.8 g of calcium carbonate.

[0103] Example 6: 35.7Co2.5Y0.7Ba1.1Zr / 60CaCO3

[0104] As an ammonia decomposition catalyst, a catalyst having a composition of 35.7Co2.5Y0.7Ba1.1Zr / 60CaCO3 was prepared by a kneading method. Specifically, the catalyst was obtained by the same method as in Example 3, except that the amounts of the raw materials added were changed to 1.7 g of yttrium nitrate n-hydrate (anhydrous content: 72.3%), 0.2 g of barium nitrate, 0.9 g of an aqueous zirconium oxynitrate solution (containing 25% zirconium as oxide), 11.6 g of basic cobalt (II) carbonate (metallic cobalt content: 44.3%), and 11.8 g of calcium carbonate.

[0105] Example 7: 48Co7.2Ce1.8Ba3Zr / 40CaCO3

[0106] As an ammonia decomposition catalyst, a catalyst having a composition of 48Co7.2Ce1.8Ba3Zr / 40CaCO3 was prepared by a kneading method. Specifically, 2.9 g of an aqueous solution of cerium nitrate (containing 25% of cerium in terms of oxide conversion) was mixed with 1.7 g of an aqueous solution of zirconyl nitrate (containing 18% of zirconium in terms of oxide conversion). 0.2 g of mixed barium carbonate was added to the obtained nitrate aqueous solution to dissolve a portion of the barium carbonate to prepare a slurry solution. 8.0 g of basic cobalt (II) carbonate (metal cobalt content: 44.3%) was placed in a magnetic dish, the above-mentioned slurry solution was added and thoroughly mixed. After further adding 4.0 g of calcium carbonate thereto, the mixture was properly mixed with a spatula in a hot water bath set at 95°C to obtain a concentrated paste. Hereinafter, the catalyst was obtained using the same method as in Example 3.

[0107] Example 8: 56Co8.4Ce2.1Ba3.5Zr / 30CaCO3

[0108] As an ammonia decomposition catalyst, a catalyst having a composition of 56Co8.4Ce2.1Ba3.5Zr / 30CaCO3 was prepared by a kneading method. Specifically, the catalyst was obtained by the same method as in Example 7, except that the amounts of the raw materials added were changed to 3.4 g of an aqueous cerium nitrate solution (containing 25% cerium as oxide), 1.9 g of an aqueous zirconyl nitrate solution (containing 18% zirconium as oxide), 0.3 g of barium carbonate, 9.3 g of basic cobalt (II) carbonate (metallic cobalt content: 44.3%), and 3.0 g of calcium carbonate.

[0109] Example 9: 49.2Co5.4Y3.6Sr1.8Zr / 40CaCO3

[0110] As an ammonia decomposition catalyst, a catalyst having a composition of 49.2Co5.4Y3.6Sr1.8Zr / 40CaCO3 was prepared by a kneading method. Specifically, the catalyst was obtained by the same method as in Example 3, except that the amounts of the raw materials added were changed to 5.9 g of yttrium nitrate n-hydrate (anhydrous content: 72.3%), 3.2 g of an aqueous zirconium oxynitrate solution (containing 18% zirconium as oxide), 2.4 g of strontium nitrate, 26.5 g of basic cobalt (II) carbonate (metallic cobalt content: 44.3%), and 13.0 g of calcium carbonate, and that strontium nitrate was added instead of barium nitrate.

[0111] Comparative Example 1: 91.8Co5Y1.2Ba2Zr

[0112] As an ammonia decomposition catalyst, a catalyst having a composition of 91.8Co5Y1.2Ba2Zr was prepared by a kneading method. Specifically, the catalyst was obtained by the same method as in Example 1, except that the amounts of each raw material added were changed to 3.3 g of yttrium nitrate n-hydrate (anhydrous content: 72.3%) and 0.4 g of barium nitrate dissolved in 10 g of ion-exchanged water; the amounts of each raw material added were changed to 1.6 g of an aqueous zirconium oxynitrate solution (containing 25% zirconium as oxide) and 29.8 g of basic cobalt (II) carbonate (metallic cobalt content: 44.3%); and calcium carbonate was not added.

[0113] Comparative Example 2: 73.4Co4Y1Ba1.6Zr / / 20Al2O3

[0114] As an ammonia decomposition catalyst, a catalyst having a composition of 73.4Co4Y1Ba1.6Zr / / 20Al2O3 was prepared by a kneading method. Specifically, the catalyst was obtained by the same method as in Example 1 except that 3.9 g of aluminum oxide was added instead of calcium carbonate.

[0115] Comparative Example 3: 73.4Co4Y1Ba1.6Zr / / 20SiO2

[0116] As an ammonia decomposition catalyst, a catalyst having a composition of 73.4Co4Y1Ba1.6Zr / / 20SiO2 was prepared by a kneading method. Specifically, the catalyst was obtained by the same method as in Example 1 except that 3.9 g of silicon oxide was added instead of calcium carbonate.

[0117] Comparative Example 4: 73Co16Ce11Zr

[0118] According to Example 12 of Japanese Patent Application Laid-Open No. 2010-94668, a catalyst having a composition of 73Co16Ce11Zr was prepared by a coprecipitation method.

[0119] Comparative Example 5: 5% Ru / Al2O3

[0120] 12.5 g of a ruthenium nitrate aqueous solution having a ruthenium content of 4.0% by mass was uniformly impregnated into the γ-alumina powder (BET specific surface area of ​​103 m 2 / g) 10 g was added and adjusted to 5 mass % in terms of Ru, followed by drying at 120° C. Thereafter, the mixture was calcined at 400° C. for 2 hours to obtain a catalyst powder.

[0121] Test Example 1: Evaluation of Ammonia Decomposition Activity

[0122] The catalyst powders from Examples 1-9 and Comparative Examples 1-5 were packed into a cylindrical container and compacted using a press. The compacted product was crushed and sieved to 300-600 μm, granulated, and used as evaluation samples. 0.6 mL of the resulting evaluation sample was thoroughly mixed with 0.9 mL of quartz sand before being filled into a tubular flow reactor with an inner diameter of 0.8 cm to form a catalyst layer. 3.0 g of quartz sand was further added to the catalyst layer to form a gas preheating layer.

[0123] A tubular flow reactor filled with an evaluation sample was placed in a tubular furnace. The temperature of the tubular furnace was raised to 600°C under a nitrogen flow, and a mixed gas of 10% by volume hydrogen and 90% by volume nitrogen was flowed through the reactor for 1 hour to perform a hydrogen reduction treatment on the catalyst.

[0124] After completing the hydrogen reduction pre-treatment, nitrogen is circulated in the reactor for a short time to replace the gas in the reaction tube, the supply of nitrogen is stopped, and ammonia gas with a filling volume of 100% by volume relative to each catalyst is supplied at 170 mL / min. After the reaction pressure is boosted to 0.9 MPa (absolute pressure) using a back pressure valve, the temperature of the tubular furnace is adjusted to the temperature shown in Table 1, and the ammonia decomposition activity is measured. The reactor outlet gas contains hydrogen, nitrogen and unreacted ammonia. After the unreacted ammonia is captured using sulfuric acid water, a soap film flowmeter is used to measure the flow rate of the remaining gas containing hydrogen and nitrogen. Based on the obtained measured values, the decomposition rate is calculated using the following calculation formula. The results are shown in Table 1. It should be noted that in Table 1, " / / " indicates that calcium carbonate, etc. are added after the calcination of other catalyst components, and " / " indicates that calcium carbonate, etc. are mixed with other catalyst components and calcined.

[0125] Ammonia decomposition rate (%) = [amount of decomposition gas (hydrogen + nitrogen) (L) / amount of supplied ammonia (L) × 2] × 100

[0126] [Table 1]

[0127]

[0128] As shown in the results in Table 1, the catalysts of the Examples did not exhibit a significant decrease in ammonia decomposition activity due to the addition of calcium carbonate, and their activity remained substantially the same compared to Comparative Example 1. Furthermore, it was confirmed that the base metal catalysts of the Examples exhibited significantly superior low-temperature activity compared to the conventional precious metal catalysts shown in Comparative Example 5.

[0129] Test Example 2: Strength Measurement

[0130] As a representative example of the catalyst described in the present invention, the catalyst powders of Examples 1, 3, 7, and 9 and the catalysts of Comparative Examples 1 to 4 were formed into cylindrical pellets, and their strength was measured. Specifically, a molding aid and an appropriate amount of pure water were added to each catalyst powder, and after kneading using a kneader, the mixture was extruded into a cylindrical shape with a diameter of 5 mm and a length of 6 mm, and dried at 120°C. Then, the pellets were calcined at 200°C for 2 hours in the same manner as in Example 3 and Comparative Example 1, and then calcined at 400°C for 2 hours to obtain pellets for strength testing. The strength of the cylindrical side surface direction of the 400°C calcined product of each pellet catalyst and the sample obtained by hydrogen reduction treatment at 600°C for 1 hour in the same manner as in Test Example 1 was measured using a log house hardness tester. The results are shown in Table 2.

[0131] [Table 2]

[0132]

[0133] As shown in the results in Table 2, the comparative catalysts, which do not contain calcium carbonate, exhibited a significant decrease in strength after reduction treatment. On the other hand, the samples of the examples also maintained excellent strength after reduction treatment. This demonstrates that the ammonia decomposition catalysts of the present invention are highly suitable for industrial ammonia decomposition.

Claims

1. An ammonia decomposition catalyst, characterized in that It contains: Cobalt (A); One or more rare earth elements (B) selected from cerium, yttrium and lanthanum; One or more alkaline earth metal elements (C) selected from barium and strontium; Zirconium (D); and one or more calcium compounds (E) selected from calcium carbonate, calcium oxide and calcium hydroxide, The cobalt (A), rare earth element (B), alkaline earth metal element (C) and zirconium (D) are contained in the form of metal or oxide, The content of the calcium compound (E) in the catalyst is 10% by mass or more and 65% by mass or less.

2. The ammonia decomposition catalyst according to claim 1, wherein The content of the cobalt (A) is 30% by mass or more in terms of oxide.

3. The ammonia decomposition catalyst according to claim 1 or 2, wherein The content of the rare earth element (B) is 1% by mass or more and 24% by mass or less in terms of oxide, The content ratio of the alkaline earth metal element (C) is 0.1 mass % or more and 10 mass % or less in terms of oxide, The content of the zirconium (D) is 0.1% by mass or more and 10% by mass or less in terms of oxide.

4. A method for producing hydrogen and nitrogen, characterized in that: It includes the following steps: a step of subjecting the ammonia decomposition catalyst according to any one of claims 1 to 3 to a reduction treatment; and A process of decomposing ammonia into hydrogen and nitrogen by bringing a gas containing ammonia into contact with the ammonia decomposition catalyst that has been subjected to reduction treatment.

5. A use of a catalyst for decomposing ammonia, characterized in that: The catalyst comprises: cobalt (A); one or more rare earth elements (B) selected from cerium, yttrium and lanthanum; one or more alkaline earth metal elements (C) selected from barium and strontium; zirconium (D); and one or more calcium compounds (E) selected from calcium carbonate, calcium oxide and calcium hydroxide. The cobalt (A), rare earth element (B), alkaline earth metal element (C) and zirconium (D) are contained in the catalyst in the form of metal or oxide. The content of the calcium compound (E) in the catalyst is 10% by mass or more and 65% by mass or less.

6. The use according to claim 5, wherein The content of the cobalt (A) in the catalyst is 30% by mass or more in terms of oxide.

7. The use according to claim 5 or 6, wherein The content ratio of the rare earth element (B) in the catalyst is 1 mass % or more and 24 mass % or less in terms of oxide, The content ratio of the alkaline earth metal element (C) in the catalyst is 0.1 mass % or more and 10 mass % or less in terms of oxide, The content of the zirconium (D) in the catalyst is 0.1% by mass or more and 10% by mass or less in terms of oxide.

8. A method for producing hydrogen and nitrogen, characterized in that It includes the following steps: A step of subjecting an ammonia decomposition catalyst to a reduction treatment, the ammonia decomposition catalyst comprising: cobalt (A); one or more rare earth elements (B) selected from cerium, yttrium, and lanthanum; one or more alkaline earth metal elements (C) selected from barium and strontium; zirconium (D); and one or more calcium compounds (E) selected from calcium carbonate, calcium oxide, and calcium hydroxide, wherein the cobalt (A), rare earth element (B), alkaline earth metal element (C), and zirconium (D) are contained in the form of metals or oxides, and the content ratio of the calcium compound (E) in the catalyst is 10% by mass or more and 65% by mass or less; and A process of decomposing ammonia into hydrogen and nitrogen by bringing a gas containing ammonia into contact with the ammonia decomposition catalyst that has been subjected to reduction treatment.

9. The method according to claim 8, wherein The content of the cobalt (A) in the catalyst is 30% by mass or more in terms of oxide.

10. The method according to claim 8 or 9, wherein: The content ratio of the rare earth element (B) in the catalyst is 1 mass % or more and 24 mass % or less in terms of oxide, The content ratio of the alkaline earth metal element (C) in the catalyst is 0.1 mass % or more and 10 mass % or less in terms of oxide, The content of the zirconium (D) in the catalyst is 0.1% by mass or more and 10% by mass or less in terms of oxide.

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