Ammonia decomposition catalyst

Abstract

To provide an ammonia decomposition catalyst which can suppress NH3 slip and suppress the amount of generation of N2O in a temperature range of 250 to 300°C.SOLUTION: An ammonia decomposition catalyst including a base material and a first layer provided on the base material, the first layer including a first zeolite and a platinum group metal attached to the first zeolite.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an ammonia decomposition catalyst. [Background technology]

[0002] Ammonia (NH3) does not emit carbon dioxide when burned, and as part of the recent trend toward a carbon-neutral society, it is being studied as a carbon-free fuel to replace fossil fuels. For example, in the power generation sector, ammonia co-combustion in coal-fired power plants and ammonia mono-combustion technologies are being considered. In addition, in the internal combustion engine sector, technology to use ammonia as a fuel for ocean-going ships and other vessels is being considered.

[0003] When ammonia is used as fuel, NO is released as exhaust gas. x In addition, since ammonia has poor ignition properties, unburned ammonia slips and is contained in the exhaust gas.

[0004] As a means for purifying these exhaust gas components, it is envisaged to apply an SCR (Selective Catalytic Reduction) catalyst and an ammonia decomposition catalyst including an ammonia oxidation catalyst, as shown in, for example, Patent Document 1. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2022-105849 Summary of the Invention [Problem to be solved by the invention]

[0006] The SCR catalyst removes NH3 and NO from the exhaust gas. x and N2O are purified by the SCR reaction. However, when ammonia is used as fuel, it is difficult to sufficiently suppress NH3 slip because the amount of ammonia in the exhaust gas is large.

[0007] Ammonia oxidation catalysts can suppress NH3 slip. However, in the temperature range of 250-300°C, the oxidation of NH3 tends to produce N2O, which has a global warming potential approximately 300 times that of CO2.

[0008] For this reason, there is a need for the development of an ammonia decomposition catalyst that can suppress NH3 slip and reduce the amount of N2O produced in equipment such as ships and generators that use ammonia as fuel.

[0009] The present invention has been made in view of the above problems, and an object of the present invention is to provide an ammonia decomposition catalyst that can suppress NH slip and suppress the amount of N2O produced in a temperature range of 250 to 300°C. [Means for solving the problem]

[0010] The present invention provides various specific embodiments as follows. (1) A substrate and a first layer provided on the substrate, The first layer comprises a first zeolite and a platinum group metal attached to the first zeolite.

[0011] (2) A second layer is further provided on a second surface of the first layer opposite to the first surface facing the substrate, The ammonia decomposition catalyst according to (1), wherein the second layer contains a second zeolite.

[0012] (3) The ammonia decomposition catalyst according to (1) or (2), wherein the first zeolite is a transition metal element ion-exchanged zeolite.

[0013] (4) The ammonia decomposition catalyst according to (2), wherein the second zeolite is a transition metal element ion-exchanged zeolite.

[0014] (5) The ammonia decomposition catalyst according to (3) or (4), wherein the transition metal element ion-exchanged zeolite is a zeolite ion-exchanged with copper.

[0015] (6) The ammonia decomposition catalyst according to (5), wherein the copper content of the copper-ion-exchanged zeolite is 0.1% by mass or more and 10% by mass or less, calculated based on copper oxide.

[0016] (7) The ammonia decomposition catalyst according to any one of (1) to (6), wherein the first zeolite has one or more skeletal structures selected from the group consisting of CHA type, AEI type, AFX type, KFI type, SFW type, MFI type, ERI type, and BEA type.

[0017] (8) The ammonia decomposition catalyst according to (2), wherein the second zeolite has one or more skeletal structures selected from the group consisting of CHA type, AEI type, AFX type, KFI type, SFW type, MFI type, ERI type, and BEA type.

[0018] (9) The ammonia decomposition catalyst according to any one of (1) to (8), wherein the platinum group metal is platinum or palladium.

[0019] (10) The ammonia decomposition catalyst according to any one of (1) to (9), wherein the mass percentage of the platinum or palladium relative to the mass of the first zeolite is 0.1% or more and 5% or less.

[0020] (11) The ammonia decomposition catalyst is composed of the substrate and the first layer provided on the substrate, The ammonia decomposition catalyst according to (1), wherein the thickness of the first layer is 5 μm or more and 200 μm or less.

[0021] (12) The thickness of the first layer is 5 μm or more and 200 μm or less, The ammonia decomposition catalyst according to (2), wherein the second layer has a thickness of 20 μm or more and 250 μm or less. [Effects of the Invention]

[0022] According to the present invention, it is possible to provide an ammonia decomposition catalyst that can suppress NH3 slip in the temperature range of 250 to 300°C and produces a small amount of N2O. [Brief explanation of the drawings]

[0023] [Figure 1] FIG. 1 is a diagram illustrating the mechanism of the ammonia decomposition catalyst according to the first embodiment. [Figure 2] FIG. 1 is a diagram illustrating the mechanism of a conventional ammonia decomposition catalyst. [Figure 3] 1 is a schematic cross-sectional view of an ammonia decomposition catalyst according to a first embodiment. [Figure 4] FIG. 3 is a schematic cross-sectional view of an ammonia decomposition catalyst according to a second embodiment. [Figure 5] 1 is an example of an optical microscope image of a cross section of an ammonia decomposition catalyst. DETAILED DESCRIPTION OF THE INVENTION

[0024] Specific examples of the ammonia decomposition catalyst of the present invention will be described below with reference to the drawings. In the drawings of the present invention, the same reference symbols represent the same or corresponding parts. Furthermore, dimensional relationships such as length, width, thickness, and depth have been appropriately changed for clarity and simplification of the drawings, and do not necessarily represent actual dimensional relationships.

[0025] In this specification, the notation in the form "A to B" means A or more and B or less, and when no unit is specified for A and a unit is specified only for B, the unit of A and the unit of B are the same.

[0026] [Embodiment 1: Ammonia decomposition catalyst] An ammonia decomposition catalyst according to one embodiment of the present invention (hereinafter also referred to as "Embodiment 1") is an ammonia decomposition catalyst comprising a substrate and a first layer provided on the substrate, the first layer including a first zeolite and a platinum group metal adhered to the first zeolite.

[0027] The ammonia decomposition catalyst of embodiment 1 can suppress NH3 slip and also suppress the amount of N2O produced in the temperature range of 250 to 300° C. The reason for this is presumed to be as follows.

[0028] Platinum group metals are catalysts that oxidize NH3. NH3 is oxidized by the catalytic activity of platinum group metals to produce N2, as well as NO and NO2 (hereinafter, NO and NO2 are collectively referred to as NO). x Platinum group metals also act as catalysts for the reaction of NO2 and NH3. When NO2 and NH3 react due to the catalytic activity of platinum group metals, N2O is produced.

[0029] Zeolite adsorbs NH3 and NO on the zeolite. x and NH3 to produce NO x is reduced to N2.

[0030] The ammonia decomposition catalyst of embodiment 1 contains a platinum group metal, which oxidizes NH3 and suppresses NH3 slip. Furthermore, as shown in Figure 1, in the ammonia decomposition catalyst of embodiment 1, the platinum group metal 3 is attached to the first zeolite 2, and the distance between the platinum group metal 3 and the first zeolite 2 is short. This allows the NO generated by the platinum group metal 3 to be oxidized. x reacts easily with NH3 adsorbed on Zeolite 2, and NO x is easily reduced to N2. Therefore, the reaction of NO2 with NH3 by the platinum group metal 3 is suppressed, and the production of N2O is suppressed.

[0031] In conventional ammonia decomposition catalysts such as those disclosed in Patent Document 1, as shown in Figure 2, the platinum group metal 3 does not adhere to the first zeolite 2, and the platinum group metal 3 and the first zeolite 2 are separated from each other. For this reason, in conventional ammonia decomposition catalysts, NO2 produced by the platinum group metal 3 is likely to react again with NH3 by the platinum group metal 3, producing NO.

[0032] <Structure> As shown in FIG. 3, the ammonia decomposition catalyst 1 of embodiment 1 includes a substrate 10 and a first layer 11 provided on the substrate 10. As shown in FIG. 3, the ammonia decomposition catalyst 1 can be composed of a substrate 10 and a first layer 11 provided on the substrate 10. In this case, the thickness of the first layer 11 is preferably 5 μm or more and 200 μm or less, and more preferably 10 μm or more and 180 μm or less. When the thickness of the first layer 11 is 5 μm or more, the performance of suppressing NH slip and the performance of suppressing N2O production can be improved. When the thickness of the first layer 11 is 200 μm or less, the pressure loss when exhaust gas passes through the first layer 11 can be reduced.

[0033] In the present disclosure, "the thickness of the first layer is 5 μm or more and 200 μm or less" means that the thickness of the first layer measured at any five points is in the range of 5 μm or more and 200 μm or less. The same applies to the thickness of the second layer described below.

[0034] The thickness of the first layer at any five locations is measured using the following procedure. The ammonia decomposition catalyst is cut into a cross section parallel to the thickness direction of the first layer to obtain a measurement sample with the cross section of the first layer exposed. The measurement sample is observed under an optical microscope at 30 to 300 magnifications to obtain an observation image. At any five locations within the measurement field, the interface of the first layer on the substrate side is used as a reference, and the shortest distance from this interface to the surface of the first layer is measured. If a second layer is provided on the first layer, the interface of the first layer on the substrate side is used as a reference, and the shortest distance from this interface to the interface of the first layer on the second layer side is measured. Note that if the thickness of the first layer within the measurement field clearly varies, the five locations are set so as to include the location with the smallest thickness and the location with the largest thickness.

[0035] Fig. 5 is an example of an optical microscope image of a measurement sample obtained by cutting an ammonia decomposition catalyst having a honeycomb structure as the substrate 10 at a cross section parallel to the thickness direction of the first layer 11. In Fig. 5, since the thickness of the first layer 11 varies, the five arbitrary locations are set so as to include the location with the smallest thickness (locations indicated by a and b in Fig. 5) and the location with the largest thickness (locations indicated by c and d in Fig. 5).

[0036] The thickness of the second layer, which will be described later, is measured in the same manner as the first layer.

[0037] <Base material> In the ammonia decomposition catalyst of embodiment 1, the substrate can be a honeycomb structure, which is commonly used in ammonia decomposition catalysts. Examples of honeycomb structures include ceramic monolith supports such as cordierite, silicon carbide, and silicon nitride, metal honeycomb supports such as stainless steel supports, wire mesh supports such as stainless steel supports, and steel wool-like knitted wire supports. The shape of the honeycomb structure is not particularly limited, and any shape can be selected, such as a prismatic shape, a cylindrical shape, a spherical shape, a honeycomb shape, or a sheet shape. These structures can be used alone or in combination of two or more.

[0038] Widely known honeycomb structures include flow-through structures in which gas flow paths are connected, and wall-flow structures in which some end faces of the gas flow paths are sealed and gas can flow through the walls of the gas flow paths, and both of these are applicable.

[0039] <First layer> In the ammonia decomposition catalyst of embodiment 1, the first layer is provided on a substrate. The first layer preferably covers at least a portion of the surface of the substrate, and more preferably covers the entire surface of the substrate. As long as the effects of the present invention are not impaired, the scope of the present invention does not deviate even if a portion of the substrate is not covered with the first layer.

[0040] In the ammonia decomposition catalyst of Embodiment 1, the first layer comprises a first zeolite and a platinum group metal attached to the first zeolite.

[0041] <Daiichi Zeolite> In the ammonia decomposition catalyst of embodiment 1, the first zeolite can be any of various zeolites commonly used in ammonia decomposition catalysts. Zeolites include crystalline aluminosilicates as well as crystalline metal aluminophosphates, such as crystalline aluminum phosphate (ALPO) and crystalline aluminum silicate phosphate (SAPO), which have micropores and a layered structure similar to that of zeolites. Specific examples include, but are not limited to, aluminophosphates such as SAPO-34 and SAPO-18.

[0042] Generally, zeolites have cations as counter ions at solid acid sites, and the cations are typically ammonium ions or protons. The first zeolite is preferably a transition metal element ion-exchanged zeolite in which the cation sites of the zeolite are ion-exchanged with a transition metal element. Examples of transition metal elements include, but are not limited to, nickel (Ni), cobalt (Co), copper (Cu), iron (Fe), manganese (Mn), and rhenium (Re). Among these, nickel, cobalt, copper, iron, and manganese are preferred, with copper and iron being more preferred. From the viewpoint of improving the NO generation suppression performance, the first zeolite is preferably a zeolite ion-exchanged with copper or a zeolite ion-exchanged with iron.

[0043] When the first zeolite is a transition metal element ion-exchanged zeolite, the ion exchange rate of the zeolite is preferably 1 to 100%, more preferably 10 to 95%, and even more preferably 30 to 90%, on a molar basis relative to Al serving as the ion exchange sites. An ion exchange rate of 100% means that all of the cationic species in the zeolite have been ion-exchanged with transition metal element ions. All of the transition metal elements may be ion-exchanged, or a portion of them may exist in the form of an oxide such as copper oxide or iron oxide.

[0044] When the first zeolite is a zeolite ion-exchanged with copper, the copper content of the zeolite ion-exchanged with copper, calculated as copper oxide (CuO), is preferably 0.1% by mass to 10% by mass, more preferably 1% by mass to 7% by mass, and even more preferably 2% by mass to 6% by mass. The copper content can be measured by a common measurement method such as fluorescent X-ray or ICP (Inductively Coupled Plasma).

[0045] When the first zeolite is a zeolite ion-exchanged with iron, the iron content of the zeolite ion-exchanged with iron, calculated as iron oxide (FeO), is preferably 0.1% by mass to 10% by mass, more preferably 1% by mass to 9% by mass, and even more preferably 2% by mass to 8% by mass. The iron content can be measured by a common measurement method such as fluorescent X-ray or ICP.

[0046] Examples of zeolites that may constitute the first zeolite include, but are not limited to, zeolites having a Y-type, A-type, L-type, beta-type, mordenite-type, ZSM-5-type, ferrierite-type, mordenite-type, CHA-type, AEI-type, AFX-type, KFI-type, and SFW-type framework structure, as well as crystalline metal aluminophosphates such as SAPO and ALPO. The first zeolite may contain one of these zeolites alone, or two or more of them in any combination and ratio.

[0047] The International Zeolite Association (hereinafter sometimes abbreviated as "IZA") has compiled a database of zeolite framework structures, and zeolites having structures defined in the IUPAC structure code (hereinafter simply referred to as "structure code") can be used without particular restrictions. These structures can be identified by comparing them with the powder X-ray diffraction (hereinafter referred to as "XRD") patterns listed in "Collection of simulated XRD powder patterns for zeolites, Fifth revised edition (2007)" or the XRD patterns listed in "Zeolite Framework Types" on the IZA Structure Committee's website http: / / www.iza-struture.org / databases / . Among these, it is preferable to use zeolites that are heat-resistant and have various known framework structures.

[0048] The first zeolite is preferably a zeolite having a 6-membered oxygen ring structure, a double 6-membered oxygen ring structure, an 8-membered oxygen ring structure, and / or a 12-membered oxygen ring structure. The first zeolite is preferably a zeolite having one or more skeletal structures selected from the group consisting of CHA-type, AEI-type, AFX-type, KFI-type, SFW-type, MFI-type, ERI-type, and BEA-type. From the viewpoint of improving the performance of suppressing NO production, the first zeolite is more preferably a zeolite having a CHA-type skeletal structure. From the viewpoint of improving the performance of suppressing NO production, the first zeolite is preferably a transition metal element ion-exchanged zeolite having a CHA-type skeletal structure, and more preferably a zeolite ion-exchanged with copper having a CHA-type skeletal structure (hereinafter also referred to as "CHA-type Cu ion-exchanged zeolite").

[0049] The number of acid sites of zeolites varies depending on the SiO / AlO ratio (=SAR), and generally, zeolites with low SAR have many acid sites but deteriorate more severely in the presence of water vapor, while zeolites with high SAR tend to have excellent heat resistance but few acid sites. From these viewpoints, the SAR of the first zeolite is preferably 1 to 500, more preferably 1 to 100, and even more preferably 1 to 50.

[0050] The average particle diameter D50 of the first zeolite can be appropriately set depending on the desired performance and is not particularly limited. From the viewpoint of maintaining a large specific surface area, improving heat resistance, and increasing the number of catalytically active sites, the average particle diameter D50 of the first zeolite is preferably 0.5 to 100 μm, more preferably 0.5 to 50 μm, and even more preferably 0.5 to 30 μm. In this specification, the term "average particle diameter D50" refers to the particle diameter when the cumulative value from the smallest particle diameter reaches 50% of the total in the cumulative distribution of particle diameters on a volume basis, and is the so-called median diameter. The average particle diameter D50 is measured using a laser diffraction particle diameter distribution analyzer (e.g., the SALD-3100 laser diffraction particle diameter distribution analyzer manufactured by Shimadzu Corporation).

[0051] The BET specific surface area of ​​the first zeolite is not particularly limited and can be appropriately set depending on the desired performance. From the viewpoint of maintaining a large specific surface area and enhancing catalytic activity, the BET specific surface area of ​​the first zeolite measured by the BET single point method is 10 to 1000 m 2 / g is preferred, and 50 to 1000m 2 / g is more preferable, and 100 to 1000m 2 / g is even more preferable. Zeolites are commercially available in various grades from manufacturers both in Japan and overseas, and various grades of commercially available products can be used depending on the required performance. Zeolites can also be produced by methods known in the art. In this specification, the "BET specific surface area" refers to a value determined by the BET single-point method using a specific surface area / pore distribution measuring device (trade name: BELSORP-mini II, manufactured by Microtrac-Bell Co., Ltd.) and analysis software (trade name: BEL_Master, manufactured by Microtrac-Bell Co., Ltd.).

[0052] The amount of the first zeolite supported in the first layer is not particularly limited, but from the viewpoint of the balance between catalytic performance and pressure loss, it is preferably 10 to 100 g / L, more preferably 20 to 70 g / L per liter of ammonia decomposition catalyst.

[0053] The first zeolite may be provided directly on the substrate, or the first zeolite may be provided on the substrate via a binder, a base layer, or the like.

[0054] ≪Platinum group metals≫ In the ammonia decomposition catalyst of embodiment 1, the platinum group metal is attached to the first zeolite. The manner in which the platinum group metal is attached to the first zeolite is not particularly limited, as long as at least a portion of the surface of the first zeolite is exposed to the outside and the first zeolite can come into contact with an ammonia-containing gas. Particles containing a platinum group metal may be attached to the surface of the first zeolite. In this case, at least a portion of the particles containing a platinum group metal may be attached and exposed to the outside of the first zeolite. Alternatively, a layered platinum group metal may be provided so as to cover a portion of the surface of the first zeolite. In this case, at least a portion of the layered platinum group metal may be attached and exposed to the outside of the first zeolite. The attachment of platinum metal to the first zeolite can be confirmed by observation with a general electron microscope such as a scanning electron microscope (SEM), an electron probe microanalyzer (EPMA), or a transmission electron microscope (TEM).

[0055] The platinum group metal may be at least one selected from the group consisting of platinum (Pt), palladium (Pd), rhodium (Rh), ruthenium (Ru), iridium (Ir), and osmium (Os). From the viewpoints of NH3 oxidation performance and suppression of NO production, the platinum group metal is preferably platinum or palladium.

[0056] The platinum group metal may be present in particles containing the platinum group metal, at least a portion of which is exposed to the outside of the first zeolite. The particles may be platinum group metal particles made of a platinum group metal. Alternatively, the particles may be composite particles having a base particle made of an inorganic material and a platinum group metal supported on the base particle. The platinum group metal particles and composite particles may be used alone. Alternatively, the platinum group metal particles and composite particles may be used in any combination and ratio.

[0057] The platinum group metal particles may be made of at least one metal selected from the group consisting of platinum, palladium, rhodium, ruthenium, iridium, and osmium. From the viewpoints of NH3 oxidation performance and suppression of NO generation, the platinum group metal particles are preferably made of platinum or palladium. The platinum group metal particles may contain inevitable impurities as long as they do not impair the effects of the present invention.

[0058] The average particle diameter D50 of the platinum group metal particles is not particularly limited and can be appropriately set depending on the desired performance. From the viewpoint of maintaining a large specific surface area, improving heat resistance, and increasing the number of catalytically active sites, the average particle diameter D50 of the platinum group metal particles is preferably 0.5 to 100 μm, more preferably 1 to 100 μm, and even more preferably 1 to 50 μm.

[0059] The composite particles may include base particles made of an inorganic material and a platinum group metal supported on the base particles. The base particles may be made of an inorganic compound. Examples of inorganic compounds include oxygen storage / release materials (OSCs) such as zeolite, cerium oxide (CeO), and ceria-zirconia composite oxide (CZ composite oxide); aluminum oxides (AlO) such as γ-alumina, β-alumina, δ-alumina, η-alumina, and θ-alumina; zirconium oxide (ZrO), silicon oxide (SiO), and titanium oxide (TiO); and composite oxides containing these oxides as the main components, although the type of the inorganic compound is not particularly limited. These may also be composite oxides or solid solutions containing rare earth elements such as lanthanum and yttrium, transition metal elements, or alkaline earth metal elements. These base particles may be used singly. Alternatively, two or more types of base particles may be used in any combination and ratio.

[0060] The platinum group metal supported on the base particles can be at least one selected from the group consisting of platinum, palladium, rhodium, ruthenium, iridium, and osmium. From the viewpoints of NH3 oxidation performance and suppression of NO generation, the platinum group metal supported on the base particles is preferably platinum or palladium. The platinum group metal may contain inevitable impurities as long as they do not impair the effects of the present invention.

[0061] The average particle diameter D50 of the base material particles is not particularly limited and can be appropriately set depending on the desired performance. From the viewpoint of maintaining a large specific surface area, improving heat resistance, and increasing the number of catalytically active sites, the average particle diameter D50 of the base material particles is preferably 0.5 to 100 μm, more preferably 1 to 100 μm, and even more preferably 1 to 50 μm.

[0062] The BET specific surface area of ​​the base particles can be appropriately set depending on the desired performance and is not particularly limited. However, from the viewpoint of maintaining a large specific surface area and enhancing catalytic activity, the BET specific surface area measured by the BET single point method is preferably 10 to 500 m 2 / g is preferred, and 20 to 300m 2 / g is more preferable, and 30 to 200m 2 / g is more preferred.

[0063] The platinum group metal content of the composite particles is preferably 0.1 to 5 mass%, more preferably 0.1 to 3 mass%, and even more preferably 0.1 to 2 mass%, from the viewpoints of improving ammonia decomposition performance and suppressing the progress of grain growth (sintering) of the platinum group element on the base particles.

[0064] In the first layer, the percentage by mass of the platinum group metal relative to the mass of the first zeolite is preferably 0.1% to 5%, more preferably 0.1% to 3%, and even more preferably 0.1% to 2%, from the viewpoint of suppressing the generation of NO. In the first layer, the percentage by mass of platinum or palladium relative to the mass of the first zeolite is preferably 0.1% to 5%, more preferably 0.1% to 3%, and even more preferably 0.1% to 2%, from the viewpoint of suppressing the generation of NO.

[0065] The amount of platinum group metal supported in the first layer is not particularly limited, but from the viewpoint of the balance between catalytic performance and pressure loss, it is preferably 0.01 to 2 g / L, more preferably 0.02 to 1 g / L per 1 L of ammonia decomposition catalyst.

[0066] In the first layer, all of the platinum group metal may be attached to the first zeolite. Alternatively, the first layer may contain, in addition to the platinum group metal attached to the first zeolite, platinum group metal that is present independently and not attached to the first zeolite. As long as at least a portion of the platinum group metal is attached to the first zeolite in the first layer, the effects of the present invention can be achieved. The percentage of the mass of the platinum group metal attached to the first zeolite relative to the total mass of the platinum group metal contained in the first layer is not particularly limited, but is preferably 10% or more, and more preferably 30% or more.

[0067] <Binder> The ammonia decomposition catalyst of embodiment 1 may contain a binder for fixing the first zeolite and the platinum group metal on the substrate. Known binders can be used, and the type is not particularly limited. Examples of binders that can be used include oxygen storage / release materials (OSCs) such as silicon (Si), cerium oxide (CeO), and ceria-zirconia composite oxide (CZ composite oxide); aluminum oxides (AlO) such as γ-alumina, β-alumina, δ-alumina, η-alumina, and θ-alumina; zirconium oxide (ZrO), silicon oxide (SiO), and titanium oxide (TiO), as well as composite oxides containing these oxides as the main component. The binder content of the first layer is not particularly limited. The binder content of the first layer is preferably 1 to 10% by mass, and more preferably 1 to 5% by mass.

[0068] <Other ingredients> In the ammonia decomposition catalyst of embodiment 1, the first layer may contain other known catalytic materials, promoters, and various additives, such as cerium (Ce), zirconium (Zr), titanium (Ti), copper (Cu), iron (Fe), nickel (Ni), vanadium (V), and manganese (Mn).

[0069] [Embodiment 2] 4, an ammonia decomposition catalyst 1 according to one embodiment of the present invention (hereinafter also referred to as "Embodiment 2") includes a substrate 10, a first layer 11 provided on the substrate 10, and a second layer 12 provided on a second surface 11B of the first layer 11 opposite to a first surface 11A facing the substrate 10, and the second layer 12 may contain a second zeolite. The ammonia decomposition catalyst of Embodiment 2 can have the same configuration as Embodiment 1, except that it includes the second layer.

[0070] The ammonia decomposition catalyst of embodiment 2 includes the first layer, and therefore, for the same reasons as embodiment 1, can suppress NH3 slip and the amount of N2O produced in the temperature range of 250 to 300°C.

[0071] The ammonia decomposition catalyst of embodiment 2 further comprises a second layer comprising a second zeolite. The second zeolite adsorbs NH3 and NO3 on the zeolite. x and NH3 to produce NO x is reduced to N2. This makes it possible to further suppress NH3 slippage and the amount of N2O produced.

[0072] In the ammonia decomposition catalyst of the second embodiment, the substrate and the first layer can have basically the same configuration as the substrate and the first layer described in the first embodiment.

[0073] In the ammonia decomposition catalyst of embodiment 2, the thickness of the first layer is preferably 5 μm to 200 μm, more preferably 10 μm to 180 μm. The thickness of the second layer is preferably 20 μm to 250 μm, more preferably 25 μm to 250 μm. The total thickness of the first and second layers is preferably 30 μm to 270 μm, more preferably 35 μm to 430 μm.

[0074] <Second layer> In the ammonia decomposition catalyst of embodiment 2, the second layer is provided on a second surface of the first layer opposite to the first surface facing the substrate. The second layer preferably covers at least a portion of the second surface of the first layer, and more preferably covers the entire second surface of the first layer. As long as the effects of the present invention are not impaired, the scope of the present invention does not deviate even if a portion of the second surface of the first layer is not covered with the second layer.

[0075] In the ammonia decomposition catalyst of embodiment 2, the second layer contains a second zeolite. The second zeolite may have the same structure as the first zeolite. The second zeolite is preferably a zeolite having one or more skeletal structures selected from the group consisting of CHA, AEI, AFX, KFI, SFW, MFI, ERI, and BEA types. The second zeolite and the first zeolite may be the same or different.

[0076] From the viewpoint of improving the performance of suppressing NO production, the second zeolite is preferably a transition metal element ion-exchanged zeolite having a CHA-type framework structure, and more preferably a copper ion-exchanged zeolite having a CHA-type framework structure. In the ammonia decomposition catalyst of embodiment 2, the first zeolite and the second zeolite are preferably copper ion-exchanged zeolites having a CHA-type framework structure.

[0077] The amount of the second zeolite supported in the second layer is not particularly limited, but from the viewpoint of the balance between catalytic performance and pressure loss, it is preferably 30 to 350 g / L, more preferably 50 to 200 g / L per liter of ammonia decomposition catalyst.

[0078] The second zeolite may be provided directly on the first layer, or may be provided on the first layer via a binder, a base layer, or the like.

[0079] The ammonia decomposition catalyst of embodiment 2 can contain a binder for fixing the second zeolite on the first layer. The binder can have the same structure as the binder described in embodiment 1. The binder contained in the second layer and the binder contained in the first layer may be the same or different. The content of the binder in the second layer is not particularly limited. The content of the binder in the second layer is, for example, preferably 1 to 10 mass %, more preferably 1 to 5 mass %.

[0080] In the ammonia decomposition catalyst of the second embodiment, the second layer may contain other known catalytic materials, promoters, and various additives of the same type as those contained in the first layer.

[0081] [Application] The ammonia decomposition catalyst of the present disclosure can be suitably used, for example, in facilities such as ships and power generators that use ammonia as fuel. [Example]

[0082] The present embodiment will be described in more detail with reference to examples, although the present embodiment is not limited to these examples.

[0083] The raw materials used in this example are as follows: <Catalyst component> Pt: Monoethanolamine solution of Pt(IV) hexahydroxide (e.g., aqueous solution). Hereinafter, also referred to as Pt salt. Pt(0.3) / TiO2(46): The above Pt salt was mixed with a TiO2 / SiO2 = 90 / 10 (mass ratio) composite oxide (BET = 80 m 2 / g) and Pt is supported on TiO2 at a mass ratio of Pt / TiO2 = 0.3 / 46. Pt(0.07) / Al2O3(29.17): The above Pt salt was dissolved in γ-alumina (BET=140 m 2 / g) and Pt is supported on Al2O3 at a mass ratio of Pt / Al2O3 = 0.07 / 29.17. MFI: MFI-type zeolite (SAR=26) in which Fe was ion-exchanged to 4.0 mass% in terms of Fe2O3. BEA: Beta zeolite (SAR=25) ion-exchanged so that Fe becomes 1.2 mass% in terms of Fe2O3. SiAl2O3: SiO2 / Al2O3 = 1.5 / 98.5 (mass ratio) composite oxide (BET = 100m 2 / g). Hereinafter, this will also be referred to as Si / Al material. Cu-CHA: CHA-type Cu ion-exchanged zeolite. Copper content calculated as copper oxide: 3.2%. Hereinafter, this material will be referred to as Cu-CHA material. Pt(0.07) / Cu(6.112) / SiAl2O3(22.878): A material obtained by impregnating the above Pt salt and copper acetate aqueous solution into the above Si / Al material, and supporting Pt and Cu on SiAl2O3 in a mass ratio of Pt / Cu / SiAl2O3 = 0.07 / 6.112 / 22.878. Pt(0.07) / Cu-CHA(29.17): A material obtained by impregnating the above Pt salt into the above Cu-CHA material, and supporting Pt on Cu-CHA at a mass ratio of Pt / Cu-CHA=0.07 / 29.17. Pt(0.035) + Pd(0.035) / Cu-CHA(29.17): A material obtained by impregnating the Cu-CHA material with a platinum nitrate solution and a palladium nitrate solution, and supporting Pt and Pd on Cu-CHA in a mass ratio of Pt / Pd / Cu-CHA = 0.035:0.035:29.17. Pd(0.07) / Cu-CHA(29.17): A material obtained by impregnating the Cu-CHA material with a palladium nitrate solution to support Pd on Cu-CHA at a mass ratio of Pd / Cu-CHA=0.07:29.17.

[0084] <Binder> Si-Binder: Silica sol binder. Zr-Binder: Zirconium acetate solution. Al2O3-Binder: Boehmite binder.

[0085] <Other> Cerium nitrate solution. The cerium in the cerium nitrate solution has the effect of improving the NOx adsorption function when supported on the SCR.

[0086] [Preparation of ammonia decomposition catalyst] A flow-through cordierite honeycomb was prepared as the substrate. The cell count of the substrate was 300 per square inch, the wall thickness was 5 mil, the size was φ25.4 mm x height 76.2 mm, and the volume was 38.6 cc. The substrate was the same for all samples.

[0087] For each sample, the raw materials listed in the "First Layer" column of "Raw Materials" in Table 1 were mixed in the mass ratio shown in parentheses to obtain a first layer slurry. For example, for Sample 1, the first layer slurry was obtained by mixing the raw materials in a mass ratio of Pt / TiO2:MFI:BEA:Si-Binder = (0.3+46):20:10:10. The first layer slurry was applied to the substrate, dried in a dryer at 150°C for 15 hours, and then fired at 450°C for 30 minutes to form a first layer on the substrate. The thickness of the first layer was consistent for all samples, ranging from 5 μm to 75 μm.

[0088] For each sample, the raw materials listed in the "Second Layer" column of "Raw Materials" in Table 1 were mixed in the mass ratio shown in parentheses to obtain a second layer slurry. The second layer slurry was applied onto the first layer, dried in a dryer at 150°C for 15 hours, and then calcined at 450°C for 30 minutes to form a second layer on the first layer, thereby obtaining an ammonia decomposition catalyst. The thickness of the second layer was the same for all samples, ranging from 100 μm to 250 μm.

[0089] The type of catalyst component contained in the first and second layers of each sample, and the amount of catalyst component supported are shown in Table 2. In addition, the first layer of each sample was observed with an SEM to confirm the form of the catalyst component present.

[0090] <Form of catalyst in the first layer> In Sample 1, Pt-supported TiO2 and SiO2 composite oxide (Pt / TiO2), MFI-type Fe ion-exchanged zeolite (hereinafter also referred to as "Fe-MFI"), and BEA-type Fe ion-exchanged zeolite (hereinafter also referred to as "Fe-BEA") were confirmed. No platinum group metal (Pt) was attached to the MFI-type Fe ion-exchanged zeolite or BEA-type Fe ion-exchanged zeolite.

[0091] In sample 2, Pt-supported SiAl2O3 (Pt / SiAl2O3) was confirmed.

[0092] In sample 3, a composite oxide of SiO2 and Al2O3 carrying Pt and Cu (Pt / Cu-SiAl2O3) was confirmed.

[0093] In sample 4, Pt-supported γ-alumina (Pt / Al2O3) was confirmed.

[0094] In Samples 5 and 6, CHA-type Cu ion-exchanged zeolite with Pt-containing particles attached (hereinafter also referred to as "Pt-attached Cu-CHA") was confirmed. At least a portion of the Pt-containing particles was exposed to the outside of the zeolite. In the Pt-attached Cu-CHA, the percentage of Pt mass relative to the mass of Cu-CHA was 0.24%.

[0095] In sample 7, a CHA-type Cu ion-exchanged zeolite with Pt-containing particles and Pd-containing particles attached (hereinafter also referred to as "Pt- and Pd-attached Cu-CHA") was confirmed. At least a portion of the Pt-containing particles and Pd-containing particles were exposed to the outside of the zeolite. In the Pt- and Pd-attached Cu-CHA, the mass percentage of Pt relative to the mass of Cu-CHA was 0.12%. In the Pt- and Pd-attached Cu-CHA, the mass percentage of Pd relative to the mass of Cu-CHA was 0.12%.

[0096] In sample 8, CHA-type Cu ion-exchanged zeolite with Pd-containing particles attached (hereinafter also referred to as "Pd-attached Cu-CHA") was confirmed. At least a portion of the Pd-containing particles was exposed to the outside of the zeolite. In the Pd-attached Cu-CHA, the percentage of Pd mass relative to the mass of Cu-CHA was 0.24%.

[0097] In sample 9, Pt-supported SiAl2O3 (Pt / SiAl2O3) and CHA-type Cu ion-exchanged zeolite (Cu-CHA) were confirmed. No platinum group metal (Pt) was attached to Cu-CHA.

[0098] [Table 1]

[0099] [Table 2]

[0100] [Evaluation test] As a pretreatment for the measurements, a gas with a composition (volume basis) of 10% O2 and 90% N2 was passed through each sample of ammonia decomposition catalyst at 500°C for 10 minutes. Then, gas was passed through each sample of ammonia decomposition catalyst under the following conditions to evaluate ammonia decomposition activity. The measurement conditions and gas analysis method are as follows:

[0101] <Measurement conditions> Catalyst evaluation equipment: CATA-8000-2 (Best Instruments Co., Ltd.) FT-IR analyzer: BEX-1000FT (Best Instruments Co., Ltd.) ·Space velocity: 24000 / h Total gas flow rate: 15.4L / min Reaction temperature: 200°C, 250°C, 300°C, or 350°C Gas composition (volume basis): NH3 1000ppm, O2 10%, H2O 3%, NO 200ppm, N2 Balance

[0102] <Gas analysis method> While gas was flowing through the ammonia decomposition catalyst, the catalyst was heated to the above reaction temperature in an electric furnace. At each temperature, the gas concentrations of NH3, N2O, NO, and NO2 were measured at the inlet and outlet of the ammonia decomposition catalyst, and the NH3 conversion rate, N2O production amount, NO conversion rate, and NO2 production amount were calculated. The calculation method is as follows. NH3 purification rate (%): 100 - {(outlet NH3 concentration) / (inlet NH3 concentration) x 100} ·N2O generation amount (ppm): (Outlet N2O concentration) - (Inlet N2O concentration) NO purification rate (%): 100 - {(outlet NO concentration) / (inlet NO concentration) x 100} ·NO2 production amount (ppm): (Outlet NO2 concentration) - (Inlet NO2 concentration) The results are shown in Tables 3 and 4. In Tables 3 and 4, "ND" means No Date (not measured). In this evaluation test, if the amount of N2O produced is less than 50 ppm, it is determined that the amount of N2O produced is suppressed. Also, if the NH3 purification rate is 30% or more, it is determined that NH3 slip is suppressed.

[0103] [Table 3]

[0104] [Table 4]

[0105] [Consideration] The ammonia decomposition catalysts of Samples 5 to 8 correspond to examples, with a first layer containing CHA-type Cu ion-exchanged zeolite to which platinum group metals (Pt and / or Pd) are attached. It was confirmed that the ammonia decomposition catalysts of Samples 5 to 8 can suppress NH3 slip and also suppress the amount of NO produced in the temperature range of 250 to 300°C. In particular, it was confirmed that Samples 5 to 6 also suppressed NH3 slip in the temperature range of 250 to 300°C.

[0106] The ammonia decomposition catalysts of Samples 1 to 4 and 9 correspond to comparative examples, as the first layer does not contain zeolite to which a platinum group metal is attached. The ammonia decomposition catalysts of Samples 1 to 4 and 9 did not suppress the amount of NO produced in the temperature range of 250 to 300°C.

[0107] Although the embodiments and examples of the present invention have been described above, it is intended from the beginning that the configurations of the above-described embodiments and examples may be appropriately combined or modified in various ways. The embodiments and examples disclosed herein are illustrative in all respects and should not be considered limiting. The scope of the present invention is defined by the claims rather than the above-described embodiments and examples, and it is intended to include any modifications within the scope of the claims that are equivalent to the claims. [Explanation of symbols]

[0108] 1. Ammonia decomposition catalyst 2. Daiichi Zeolite 3 Platinum group metals 10 Base material 11 First layer 11A Front page 11B Second side 12 Second layer

Claims

1. A substrate and a first layer provided on the substrate, The first layer comprises a first zeolite and a platinum group metal attached to the first zeolite.

2. a second layer provided on a second surface of the first layer opposite to the first surface facing the substrate; 10. The ammonia decomposition catalyst of claim 1, wherein the second layer comprises a second zeolite.

3. 2. The ammonia decomposition catalyst according to claim 1, wherein the first zeolite is a transition metal element ion-exchanged zeolite.

4. 3. The ammonia decomposition catalyst according to claim 2, wherein the second zeolite is a transition metal element ion-exchanged zeolite.

5. 5. The ammonia decomposition catalyst according to claim 3, wherein the transition metal element ion-exchanged zeolite is a zeolite ion-exchanged with copper.

6. 6. The ammonia decomposition catalyst according to claim 5, wherein the copper content of the copper ion-exchanged zeolite is 0.1% by mass or more and 10% by mass or less, calculated based on copper oxide.

7. 3. The ammonia decomposition catalyst according to claim 1, wherein the first zeolite has one or more skeletal structures selected from the group consisting of CHA type, AEI type, AFX type, KFI type, SFW type, MFI type, ERI type, and BEA type.

8. 3. The ammonia decomposition catalyst according to claim 2, wherein the second zeolite has one or more framework structures selected from the group consisting of CHA type, AEI type, AFX type, KFI type, SFW type, MFI type, ERI type, and BEA type.

9. 3. The ammonia decomposition catalyst according to claim 1, wherein the platinum group metal is platinum or palladium.

10. 10. The ammonia decomposition catalyst according to claim 9, wherein the percentage of the mass of the platinum or the palladium relative to the mass of the first zeolite is 0.1% or more and 5% or less.

11. the ammonia decomposition catalyst is composed of the substrate and the first layer provided on the substrate, 2. The ammonia decomposition catalyst according to claim 1, wherein the first layer has a thickness of 5 μm or more and 200 μm or less.

12. The thickness of the first layer is 5 μm or more and 200 μm or less, 3. The ammonia decomposition catalyst according to claim 2, wherein the second layer has a thickness of 20 μm or more and 250 μm or less.

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