Exhaust gas purification catalyst for ammonia engine

Abstract

To solve the following problem that: an exhaust gas purification catalyst for ammonia engines is contacted with unburned ammonia (NH3) and nitrogen oxides (NOx) contained in exhaust gas, which are then purified into nitrogen (N2) and water (H2O); however, during this purification by the exhaust gas purification catalyst for ammonia engines, nitrous oxide (N2O), known as a greenhouse gas, is generated and discharged, and thus to provide a novel exhaust gas purification catalyst for ammonia engines that can purify unburned ammonia (NH3) as exhaust gas and suppress nitrous oxide (N2O) emission.SOLUTION: An exhaust gas purification catalyst for an ammonia engine comprises rhodium and / or platinum 212, wherein the content of palladium is 1.0 mass% or less and the content of barium is 1.0 mass% or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an exhaust gas purification catalyst for an ammonia engine. [Background technology]

[0002] An ammonia engine is an internal combustion engine that burns ammonia (NH3) to obtain driving force. Ammonia does not emit carbon dioxide (CO2) when burned, so there are high hopes for the practical application of ammonia engines. However, when an ammonia engine is running, it emits unburned ammonia and nitrogen oxides (NO x ) are emitted, and in order to purify them, the following exhaust purification devices are known.

[0003] Patent Document 1 discloses an exhaust purification device for purifying exhaust gas from an internal combustion engine fueled by ammonia, the device comprising: a catalyst having a function of reducing nitrogen oxides and a function of oxidizing ammonia; an activation state detection unit for detecting the activation state of the catalyst; a first air-fuel ratio acquisition unit for acquiring the air-fuel ratio in the exhaust gas upstream of the catalyst; and a control unit for controlling the amount of ammonia supplied by a fuel supply unit that supplies ammonia to the internal combustion engine, wherein the control unit temporarily increases the amount of ammonia supplied when the catalyst is activated and a concentration index value calculated using the air-fuel ratio acquired by the first air-fuel ratio acquisition unit, the concentration index value representing the degree of oxygen poisoning in the catalyst, exceeds a predetermined threshold. The exhaust purification device in Patent Document 1 is said to be able to quickly purify nitrogen oxides and ammonia contained in the exhaust gas from an ammonia engine.

[0004] Patent Document 2 discloses an exhaust gas purification device including an internal combustion engine fueled by at least ammonia, a catalyst disposed downstream of the internal combustion engine for oxidizing and reducing unburned ammonia and nitrogen oxides contained in the exhaust gas discharged from the internal combustion engine, an adsorber disposed downstream of the catalyst for adsorbing ammonia, and a control unit for adjusting the equivalence ratio of a mixture containing the fuel and oxygen supplied to the internal combustion engine to 1.1 or more until the catalyst reaches a predetermined temperature. According to the exhaust gas purification device of Patent Document 2, it is possible to provide an exhaust gas purification device that can suppress the emission of unburned ammonia and nitrogen oxides when starting an internal combustion engine fueled by ammonia. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2020-090895 [Patent Document 2] Patent Publication No. 2021-116802 Summary of the Invention [Problem to be solved by the invention]

[0006] The exhaust gas purification catalyst for ammonia engines contains unburned ammonia (NH3) and nitrogen oxides (NO x When an ammonia engine exhaust gas purification catalyst is used, these exhaust gases are purified into nitrogen (N2) and water (H2O). However, when purifying exhaust gases using an ammonia engine exhaust gas purification catalyst, there is an issue in that nitrous oxide (N2O), a known greenhouse gas, is generated and emitted.

[0007] Exhaust gas purification catalysts for ammonia engines have not yet been fully developed, and three-way catalysts, which are exhaust gas purification catalysts for gasoline engines, are being considered as exhaust gas catalysts for ammonia engines, as in Patent Document 1 and Patent Document 2. However, the exhaust gas emitted from an ammonia engine is completely different from that emitted from a gasoline engine in terms of the types and compositions of gases, and exhaust gas purification catalysts for gasoline engines cannot sufficiently purify the exhaust gas emitted from an ammonia engine, and there is also a risk that dinitrogen monoxide (N2O) may be generated and emitted.

[0008] Therefore, an object of the present invention is to provide an exhaust gas purification catalyst for an ammonia engine that can purify unburned ammonia (NH3) in exhaust gas and suppress the emission of dinitrogen monoxide (N2O). [Means for solving the problem]

[0009] The present invention achieves the above object by the following means.

[0010] <Aspect 1> containing rhodium and / or platinum, The palladium content is 1.0 mass% or less, and The barium content is 1.0% by mass or less. Exhaust gas purification catalyst for ammonia engines. <Aspect 2> further comprising carrier particles; and The rhodium and / or platinum are supported on the support particles. 2. The exhaust gas purification catalyst for an ammonia engine according to claim 1. <Aspect 3> Aspect 3. The catalyst for purifying exhaust gases for an ammonia engine according to aspect 2, wherein the support particles comprise support particles selected from alumina support particles, ceria support particles, zirconia support particles, silica support particles, titania support particles, and combinations thereof. <Aspect 4> a substrate and a catalyst layer on the substrate; The catalyst layer comprises the exhaust gas purification catalyst for an ammonia engine according to any one of aspects 1 to 3. Exhaust gas purification catalyst device for ammonia engines. <Aspect 5> A method for purifying exhaust gas, comprising purifying exhaust gas emitted from an ammonia engine by bringing the exhaust gas into contact with the catalyst for exhaust gas purification for an ammonia engine according to any one of aspects 1 to 3. [Effects of the Invention]

[0011] According to the exhaust gas purification catalyst for an ammonia engine of the present invention, it is possible to purify unburned ammonia (NH3) in the exhaust gas and to suppress the emission of dinitrogen monoxide (N2O). [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a schematic diagram for explaining the exhaust gas purification catalyst for an ammonia engine of the present invention. [Figure 2] FIG. 2 is a schematic diagram for explaining the exhaust gas purification catalyst device for an ammonia engine of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, an embodiment of the present invention will be described in detail. Note that the present invention is not limited to the following embodiment, and various modifications can be made within the scope of the gist of the present invention. In addition, in the description of the drawings, the same elements are given the same reference numerals, and duplicated explanations will be omitted.

[0014] <Exhaust gas purification catalyst for ammonia engines> The exhaust gas purification catalyst for an ammonia engine of the present invention comprises: containing rhodium and / or platinum, The palladium content is 1.0 mass% or less, and The barium content is 1.0 mass % or less.

[0015] According to the exhaust gas purification catalyst for an ammonia engine of the present invention, it is possible to purify unburned ammonia (NH3) in the exhaust gas and to suppress the emission of dinitrogen monoxide (N2O).

[0016] The inventors passed exhaust gas (e.g., a mixed gas containing ammonia, oxygen, nitrogen monoxide, and water) emitted from an ammonia engine through each catalytic precious metal contained in a three-way catalyst and examined its purification ability. As a result, they found that catalysts containing rhodium or platinum can purify NH3 in exhaust gas and suppress NO emissions. On the other hand, they found that catalysts containing palladium can purify NH3 in exhaust gas, but generate and emit large amounts of NO. They also found that catalysts containing barium have poor purification performance for NH3 in exhaust gas and generate and emit large amounts of NO.

[0017] Without being limited to theory, it is presumed that the exhaust gas purification catalyst for an ammonia engine contains rhodium and / or platinum, but does not contain palladium or barium, that is, the palladium content in the exhaust gas purification catalyst for an ammonia engine is 1.0 mass% or less, and the barium content is 1.0 mass% or less, so that NH3 in the exhaust gas can be purified and NO emissions can be suppressed.

[0018] In the present invention, an "ammonia engine" may be an internal combustion engine that burns at least ammonia, and therefore may be an internal combustion engine that burns (co-firing) ammonia together with a hydrocarbon fuel such as diesel or gasoline, or an internal combustion engine that burns only ammonia. Here, when the "ammonia engine" is an internal combustion engine that co-firing a hydrocarbon fuel together with ammonia, the ammonia co-firing ratio (the mixing ratio of ammonia based on combustion energy) may be 1% or more, 5% or more, 10% or more, 20% or more, 30% or more, 40% or more, 50% or more, 60% or more, 70% or more, 80% or more, 90% or more, or 95% or more, or may be less than 100%, 95% or less, 90% or less, 80% or less, 70% or less, 60% or less, 50% or less, 40% or less, 30% or less, 20% or less, or 10% or less.

[0019] FIG. 1 is a schematic diagram showing one embodiment of the exhaust gas purification catalyst for an ammonia engine of the present invention, but the present invention is not limited to this case.

[0020] The exhaust gas purification catalyst 210 for an ammonia engine contains rhodium and / or platinum 212. The rhodium and / or platinum 212 may be supported on carrier particles 211.

[0021] <Catalytic precious metals> The exhaust gas purification catalyst for an ammonia engine of the present invention contains rhodium and / or platinum.

[0022] In the present invention, rhodium is particularly excellent from the viewpoint of, for example, suppressing N2O emissions in the ammonia purification reaction, and platinum is particularly excellent from the viewpoint of, for example, early purification (low-temperature purification) of NH3 in the ammonia purification reaction.

[0023] The exhaust gas purification catalyst for an ammonia engine of the present invention may contain, but is not particularly limited to, a metal other than rhodium and platinum. Examples of metals other than rhodium and platinum include ruthenium, iron, cobalt, nickel, tungsten, molybdenum, and vanadium. Among these, from the viewpoint of ammonia purification, it is preferable to contain ruthenium and nickel.

[0024] In the present invention, rhodium and / or platinum may be, but is not particularly limited to, supported on carrier particles or may exist alone as particles.

[0025] The particle size of rhodium (primary particles) may be, for example, 1 nm or more, 5 nm or more, 10 nm or more, 15 nm or more, 20 nm or more, or 30 nm or more, or 100 nm or less, 80 nm or less, or 60 nm or less. Similarly, the particle size of platinum (primary particles) may be, for example, 1 nm or more, 5 nm or more, 10 nm or more, 15 nm or more, 20 nm or more, or 30 nm or more, or 100 nm or less, 80 nm or less, or 60 nm or less. The particle sizes of rhodium and platinum can be determined from the number average particle size in images taken with a transmission electron microscope (TEM).

[0026] When rhodium is supported on the support particles, the rhodium content may be 0.1% by mass or more, 0.2% by mass or more, 0.3% by mass or more, 0.5% by mass or more, or 1.0% by mass or more, and 10% by mass or less, 8% by mass or less, 6% by mass or less, or 4% by mass or less, relative to the support particles. Similarly, when platinum is supported on the support particles, the platinum content may be 0.1% by mass or more, 0.2% by mass or more, 0.3% by mass or more, 0.5% by mass or more, or 1.0% by mass or more, and 10% by mass or less, 8% by mass or less, 6% by mass or less, or 4% by mass or less, relative to the support particles.

[0027] <Catalytic precious metal - Palladium> In the exhaust gas purification catalyst for an ammonia engine of the present invention, the palladium content is 1.0 mass% or less. The palladium content is not particularly limited, but may be 1.0 mass% or less, 0.1 mass% or less, 0.01 mass% or less, 0.001 mass% or less, or 0 mass%, or may be more than 0%. The palladium content can be measured by X-ray fluorescence analysis (XRF). Specifically, the powder can be measured by quantitative analysis (calibration curve method) using an Axios advanced (manufactured by PANalytical).

[0028] Palladium is known as a catalytic precious metal contained in three-way catalysts. For example, palladium can purify NH3 in exhaust gases, but it also produces a large amount of N2O, a by-product of NH3 purification, so the palladium content may be the above amount.

[0029] <Catalytic precious metal - barium> In the exhaust gas purification catalyst for an ammonia engine of the present invention, the barium content is 1.0% by mass or less. The barium content is not particularly limited, but may be 1.0% by mass or less, 0.1% by mass or less, 0.01% by mass or less, 0.001% by mass or less, 0% by mass or less, or more than 0% by mass. The barium content can be measured by X-ray fluorescence analysis (XRF). Specifically, the powder can be measured by quantitative analysis (calibration curve method) using an Axios advanced (manufactured by PANalytical).

[0030] It is known that barium is added to three-way catalysts used in exhaust gas purification catalysts for gasoline engines to suppress hydrocarbon / sulfur poisoning. In contrast, for example, in exhaust gas purification catalysts for ammonia engines that burn only ammonia, unlike exhaust gas purification catalysts for gasoline engines, there is no concern about hydrocarbon / sulfur poisoning, and therefore the barium content may be the above-mentioned amount. Furthermore, for example, the addition of barium deteriorates the purification performance of NH3 and also produces a large amount of NO, so the barium content may be the above-mentioned amount.

[0031] <Carrier particles> The exhaust gas purification catalyst for an ammonia engine of the present invention may further include, but is not limited to, carrier particles. In addition, in the present invention, rhodium and / or platinum may be supported on the carrier particles, but is not limited to.

[0032] The support particles may include, but are not limited to, support particles selected from alumina support particles, ceria support particles, zirconia support particles, silica support particles, titania support particles, and combinations thereof.

[0033] The particle size of the carrier particles (secondary particles) may be, for example, 2 μm or more, 3 μm or more, or 4 μm or more, or 80 μm or less, 50 μm or less, 30 μm or less, 20 μm or less, or 10 μm or less. The particle size of the carrier particles can be determined as the median diameter obtained by dynamic light scattering of a suspension in which the carrier particles are dispersed in an appropriate liquid medium (for example, water).

[0034] Specific examples of methods for supporting rhodium and / or platinum on support particles include contacting the support particles with a precursor of rhodium and / or platinum in an appropriate liquid medium, preferably water, and then drying and calcining the recovered solid content to support rhodium and / or platinum on the support particles. Examples of the precursor of rhodium and / or platinum include, but are not limited to, rhodium nitrate, rhodium sulfate, rhodium chloride, rhodium acetate, platinum nitrate, platinum sulfate, platinum chloride, chloroplatinic acid or a salt thereof, and platinum acetate.

[0035] The exhaust gas purification catalyst for an ammonia engine is not particularly limited, but particles of rhodium and / or platinum may be used as the exhaust gas purification catalyst for an ammonia engine, carrier particles carrying rhodium and / or platinum may be used as the exhaust gas purification catalyst for an ammonia engine, or carrier particles carrying rhodium and / or platinum may be mixed with other carrier particles in a wet or dry manner to be used as the exhaust gas purification catalyst for an ammonia engine.

[0036] <Exhaust gas purification catalyst device for ammonia engine> The exhaust gas purification catalyst device for an ammonia engine of the present invention comprises: a substrate and a catalyst layer on the substrate; The catalyst layer contains the above-mentioned exhaust gas purification catalyst for an ammonia engine.

[0037] According to the exhaust gas purification catalyst device for an ammonia engine of the present invention, it is possible to purify unburned ammonia (NH3) in the exhaust gas and to suppress the emission of nitrous oxide (N2O).

[0038] FIG. 2 is a schematic diagram showing one embodiment of the catalytic device for purifying exhaust gas for an ammonia engine according to the present invention, but the present invention is not limited to this.

[0039] The catalytic device 10 for purifying exhaust gases for an ammonia engine includes a substrate 100 and a catalytic layer 200 on the substrate 100. The catalytic layer 200 includes the above-mentioned catalyst for purifying exhaust gases for an ammonia engine of the present invention, and may include a binder as necessary. By including the catalyst layer 200 with the catalyst for purifying exhaust gases for an ammonia engine of the present invention, it is possible to purify unburned ammonia (NH3) in the exhaust gas and suppress the emission of nitrous oxide (N2O).

[0040] <Base material> The substrate may have a planar shape or a honeycomb shape having a plurality of gas flow paths separated by partition walls. The substrate may be made of a ceramic or metal substrate. Examples of ceramic substrates include, but are not limited to, cordierite (2MgO-2Al2O3-5SiO2), silicon carbide (SiC), alumina (Al2O3), mullite (3Al2O3-2SiO2), and aluminum titanate (Al2TiO5). Examples of metal substrates include, but are not limited to, stainless steel (SUS), Fe-Cr-Al alloys, and Ni-Cr-Al alloys.

[0041] <Catalyst layer> The catalyst layer contains the above-mentioned catalyst for purifying exhaust gas for an ammonia engine, and may contain a binder as necessary. For the catalyst for purifying exhaust gas for an ammonia engine, please refer to the above description of "Catalyst for purifying exhaust gas for an ammonia engine".

[0042] The binder is not particularly limited, but an inorganic binder can be used, etc. Examples of inorganic binders include alumina (Al2O3), titania (TiO2), zirconia (ZrO2), etc., but are not limited to this.

[0043] Specifically, the formation of the catalyst layer may include, for example, preparing a slurry containing the exhaust gas purification catalyst for an ammonia engine, coating the slurry on a substrate, and optionally firing the coating.

[0044] In forming the catalyst layer, the amount of coating on the substrate is not particularly limited, but may be 20 g / L or more, 40 g / L or more, or 80 g / L or more, or may be 400 g / L or less, 350 g / L or less, 300 g / L or less, 250 g / L or less, or 200 g / L or less, relative to the volume of the substrate.

[0045] The amount of catalytic noble metal in the catalyst layer, in terms of metal equivalent mass per 1 L of substrate volume, may be 0.1 g / L or more, 0.2 g / L or more, 0.3 g / L or more, 0.4 g / L or more, or 0.5 g / L or more, and may be 8.00 g / L or less, 6.00 g / L or less, 4.00 g / L or less, 3.00 g / L or less, or 2.00 g / L or less.

[0046] <Exhaust gas purification method> The exhaust gas purification method of the present invention comprises: The method includes purifying exhaust gas emitted from an ammonia engine by bringing the exhaust gas into contact with the above-mentioned exhaust gas purification catalyst for an ammonia engine.

[0047] According to the exhaust gas purification method of the present invention, it is possible to purify unburned ammonia (NH3) in the exhaust gas and suppress the emission of N2O.

[0048] The exhaust gas emitted from an ammonia engine is not particularly limited, but may include unburned fuel residue and harmful substances such as unburned ammonia (NH3) and nitrogen oxides (NO x ) etc.

[0049] The method for contacting the exhaust gas is not particularly limited, and the exhaust gas may be contacted by flowing through the catalyst for exhaust gas purification for an ammonia engine, or may be contacted by flowing through a catalyst device for exhaust gas purification for an ammonia engine including the catalyst for exhaust gas purification for an ammonia engine.

[0050] The temperature at which the exhaust gas is purified is not particularly limited, but may be 100°C or higher, 200°C or higher, or 300°C or higher, or 900°C or lower, 800°C or lower, or 700°C or lower.

[0051] The exhaust gas purification method can be used for any application, for example, but not limited to, an internal combustion engine, a fuel cell, or an ammonia burner. [Example]

[0052] The present invention will be described in more detail with reference to the following examples, but the scope of the present invention is not limited to these examples.

[0053] Example 1 <Production of exhaust gas purification catalyst A1 for ammonia engine> Alumina support particles (Al2O3 support particles) as support particles were added to an aqueous solution in which platinum nitrate as a platinum precursor was dissolved, and mixed. Here, the platinum was adjusted so that 2.5 wt% of the Al2O3 support particles were supported on the platinum. Next, this mixed solution was dried and calcined, thereby reducing the platinum nitrate as a platinum precursor to platinum, and the platinum was supported on the Al2O3 support particles. In this way, an exhaust gas purification catalyst A1 for an ammonia engine in which platinum was supported on Al2O3 support particles was produced.

[0054] <Preparation of catalyst layer B1> Ammonia engine exhaust gas purification catalyst A1 (40 parts by mass) and an alumina-based binder (1 part by mass) were mixed and suspended in a solvent to prepare a slurry containing the ammonia engine exhaust gas purification catalyst A1. This slurry was poured into a cordierite honeycomb substrate (φ30 mm × 50 mm) as a substrate, and unnecessary portions were blown off with a blower to form a coating film of the slurry containing the ammonia engine exhaust gas purification catalyst A1 on the substrate wall surface. Next, this coating film was dried and fired in an electric furnace to produce a catalyst layer B1. Here, the coating amount of the catalyst layer B1 was adjusted so that the coating amount on the substrate was 41 g / L.

[0055] <Performance evaluation of exhaust gas purification catalyst A1 for ammonia engine> For the exhaust gas from an ammonia engine, an ammonia-containing mixed gas having the composition shown in Table 1 was used as a model gas. To evaluate the performance of the exhaust gas purification catalyst A1 for an ammonia engine, a catalyst layer B1 containing the exhaust gas purification catalyst A1 for an ammonia engine was first placed in a thermostatic chamber in which the catalyst layer B1 and the ammonia-containing mixed gas were reacted. The catalyst layer B1 was heated to 500°C, and then 1% hydrogen gas was passed through it for 5 minutes. The catalyst layer B1 was then cooled to 100°C or below. Next, the catalyst layer B1 was heated from 100°C to 500°C at a rate of 20°C / min while the ammonia-containing mixed gas was passed through it, causing the catalyst A1 for exhaust gas purification for an ammonia engine contained in the catalyst layer B1 to react with the ammonia-containing mixed gas. The ammonia (NH3) concentration and nitrous oxide (N2O) concentration were measured for the gas after the reaction at each temperature. The measurement results at each temperature are shown in Table 2.

[0056] [Table 1]

[0057] Example 2 <Preparation of exhaust gas purification catalyst A2 for ammonia engine> Alumina support particles (Al2O3 support particles) as support particles were added to an aqueous solution in which rhodium nitrate as a rhodium precursor had been dissolved, and mixed. The mixture was adjusted so that 0.25 wt% of rhodium was supported on the Al2O3 support particles. Next, this mixed solution was dried and calcined, thereby reducing the rhodium nitrate as a rhodium precursor to rhodium, and the rhodium was supported on the Al2O3 support particles. In this way, an exhaust gas purification catalyst A2 for an ammonia engine in which rhodium was supported on Al2O3 support particles was produced.

[0058] <Preparation of catalyst layer B2 and performance evaluation of exhaust gas purification catalyst A2 for ammonia engine> A catalyst layer B2 was produced in the same manner as in Example 1, except that the catalyst A2 for purifying exhaust gas for an ammonia engine was used instead of the catalyst A1 for purifying exhaust gas for an ammonia engine. Performance evaluation of the catalyst A2 for purifying exhaust gas for an ammonia engine was also carried out in the same manner as in Example 1. The evaluation results of the catalyst A2 for purifying exhaust gas for an ammonia engine are shown in Table 2.

[0059] Example 3 <Production of exhaust gas purification catalyst A3 for ammonia engine> Alumina support particles (Al2O3 support particles) were added to and mixed with an aqueous solution containing rhodium nitrate and platinum nitrate as precursors of rhodium and platinum. The rhodium and platinum support particles were adjusted to a loading of 0.25 wt% and 2.5 wt%, respectively, relative to the Al2O3 support particles. The mixture was then dried and calcined, reducing the rhodium nitrate and platinum nitrate as precursors of rhodium and platinum to rhodium and platinum, which were then supported on the Al2O3 support particles. In this manner, an exhaust gas purification catalyst A3 for an ammonia engine was prepared, in which rhodium and platinum were supported on Al2O3 support particles.

[0060] <Preparation of catalyst layer B3 and performance evaluation of exhaust gas purification catalyst A3 for ammonia engine> A catalyst layer B3 was produced in the same manner as in Example 1, except that the catalyst A3 for purifying exhaust gas for an ammonia engine was used instead of the catalyst A1 for purifying exhaust gas for an ammonia engine. Performance evaluation of the catalyst A3 for purifying exhaust gas for an ammonia engine was also carried out in the same manner as in Example 1. The evaluation results of the catalyst A3 for purifying exhaust gas for an ammonia engine are shown in Table 2.

[0061] Comparative Example 1 <Production of exhaust gas purification catalyst a1 for ammonia engine> Alumina support particles (Al2O3 support particles) as support particles were added to an aqueous solution in which palladium nitrate as a palladium precursor was dissolved, and mixed. Here, the mixture was adjusted so that 2.5 wt% of palladium was supported on the Al2O3 support particles. Next, this mixed solution was dried and calcined, thereby reducing the palladium nitrate as a palladium precursor to palladium, and the palladium was supported on the Al2O3 support particles. In this way, an exhaust gas purification catalyst a1 for an ammonia engine in which palladium was supported on Al2O3 support particles was produced.

[0062] <Preparation of catalyst layer b1 and performance evaluation of exhaust gas purification catalyst a1 for ammonia engine> A catalyst layer b1 was produced in the same manner as in Example 1, except that the catalyst a1 for purifying exhaust gas for an ammonia engine was used instead of the catalyst A1 for purifying exhaust gas for an ammonia engine. Performance evaluation of the catalyst a1 for purifying exhaust gas for an ammonia engine was also carried out in the same manner as in Example 1. The evaluation results of the catalyst a1 for purifying exhaust gas for an ammonia engine are shown in Table 2.

[0063] Comparative Example 2 <Production of exhaust gas purification catalyst a2 for ammonia engine> Alumina support particles (Al2O3 support particles) were added to and mixed with an aqueous solution containing palladium nitrate and rhodium nitrate as precursors of palladium and rhodium. The resulting mixture was adjusted so that palladium was supported at 2.5 wt% and rhodium was supported at 0.25 wt% relative to the Al2O3 support particles. The resulting mixture was then dried and calcined, reducing the palladium nitrate and rhodium nitrate as precursors of palladium and rhodium to palladium and rhodium, which were then supported on the Al2O3 support particles. In this manner, an exhaust gas purification catalyst a2 for an ammonia engine was prepared, in which palladium and rhodium were supported on Al2O3 support particles.

[0064] <Preparation of catalyst layer b2 and performance evaluation of exhaust gas purification catalyst a2 for ammonia engine> A catalyst layer b2 was produced in the same manner as in Example 1, except that the catalyst a2 for purifying exhaust gas for an ammonia engine was used instead of the catalyst A1 for purifying exhaust gas for an ammonia engine. Performance evaluation of the catalyst a2 for purifying exhaust gas for an ammonia engine was also carried out in the same manner as in Example 1. The evaluation results of the catalyst a2 for purifying exhaust gas for an ammonia engine are shown in Table 2.

[0065] [Table 2]

[0066] In Example 1, it was confirmed that the platinum-containing ammonia engine exhaust gas purification catalyst A1 can reduce the NH3 concentration in an NH3-containing mixed gas and suppress an increase in the NO concentration, particularly at low temperatures. In Example 2, it was confirmed that the rhodium-containing ammonia engine exhaust gas purification catalyst A2 can reduce the NH3 concentration in an NH3-containing mixed gas and suppress an increase in the NO concentration, particularly suppressing an increase in the NO concentration. In Example 3, it was confirmed that the platinum and rhodium-containing ammonia engine exhaust gas purification catalyst A3 can also reduce the NH3 concentration in an NH3-containing mixed gas and suppress an increase in the NO concentration. On the other hand, as in Comparative Examples 1 and 2, the palladium-containing ammonia engine exhaust gas purification catalyst was able to reduce the NH3 concentration in an NH3-containing mixed gas, but NO was generated as a by-product, resulting in an increase in the NO concentration.

[0067] Comparative Example 3 <Preparation of a precursor for ammonia engine exhaust gas purification catalyst a3> The catalyst A1 (40 parts by mass) for purifying exhaust gas for an ammonia engine, in which platinum was supported on Al2O3 carrier particles prepared in Example 1, was mixed with barium acetate (10 parts by mass) to prepare a precursor of the catalyst a3 for purifying exhaust gas for an ammonia engine containing barium.

[0068] <Preparation of exhaust gas purification catalyst a3 for ammonia engine and catalyst layer b3> A catalyst a3 precursor for exhaust gas purification for ammonia engines (50 parts by mass) and an alumina-based binder (1 part by mass) were mixed and suspended in a solvent to prepare a slurry containing the catalyst a3 precursor for exhaust gas purification for ammonia engines. This slurry was poured onto a cordierite honeycomb substrate (φ30 mm × 50 mm) as the substrate, and unnecessary portions were blown off with a blower to form a coating film of the slurry containing the catalyst a3 precursor for exhaust gas purification for ammonia engines on the substrate wall. Next, this coating film was dried and fired in an electric furnace. Thus, a catalyst a3 for exhaust gas purification for ammonia engines was formed from the catalyst a3 precursor for exhaust gas purification for ammonia engines, and a catalyst layer b3 containing the catalyst a3 for exhaust gas purification for ammonia engines was produced. Here, the coating amount of the catalyst layer b3 on the substrate was adjusted to be 51 g / L.

[0069] <Performance evaluation of exhaust gas purification catalyst a3 for ammonia engines> The performance evaluation of the catalyst a3 for purifying exhaust gas for an ammonia engine was carried out in the same manner as in Example 1. The evaluation results of the catalyst a3 for purifying exhaust gas for an ammonia engine are shown in Table 3.

[0070] [Table 3]

[0071] Table 3 compares the performance of exhaust gas purification catalysts for ammonia engines with and without barium. The exhaust gas purification catalyst a3 for ammonia engines containing barium in Comparative Example 3 suppressed the reduction in the NH3 concentration contained in the NH3-containing mixed gas at each temperature, and also increased the NO concentration, compared to the exhaust gas purification catalyst A1 for ammonia engines not containing barium.

[0072] From the above, it is presumed that the exhaust gas purification catalysts A1 to A3 for ammonia engines contain rhodium and / or platinum, but do not contain palladium or barium, that is, the palladium content contained in the exhaust gas purification catalysts for ammonia engines is 1.0 mass% or less, and the barium content is 1.0 mass% or less, and therefore it is possible to purify NH3 as exhaust gas and suppress NO emissions.

[0073] Although preferred embodiments of the exhaust gas purification catalyst for an ammonia engine, the exhaust gas purification catalyst device for an ammonia engine, and the exhaust gas purification method of the present invention have been described, those skilled in the art will understand that modifications can be made without departing from the scope of the claims. [Explanation of symbols]

[0074] 10. Exhaust gas purification catalyst device for ammonia engine 100 Base material 200 Catalyst layer 210 Exhaust gas purification catalyst for ammonia engine 211 Carrier particles 212 Rhodium and / or Platinum

Claims

1. containing rhodium and / or platinum, The palladium content is 1.0 mass% or less, and The barium content is 1.0% by mass or less. Exhaust gas purification catalyst for ammonia engines.

2. further comprising carrier particles; and The rhodium and / or platinum is supported on the support particles. The exhaust gas purification catalyst for an ammonia engine according to claim 1.

3. 3. The exhaust gas purification catalyst for an ammonia engine according to claim 2, wherein the support particles comprise support particles selected from alumina support particles, ceria support particles, zirconia support particles, silica support particles, titania support particles, and combinations thereof.

4. a substrate and a catalyst layer on the substrate; The catalyst layer comprises the exhaust gas purification catalyst for an ammonia engine according to any one of claims 1 to 3. Exhaust gas purification catalyst device for ammonia engines.

5. A method for purifying exhaust gas, comprising bringing exhaust gas emitted from an ammonia engine into contact with the exhaust gas purification catalyst for an ammonia engine according to any one of claims 1 to 3, thereby purifying the exhaust gas.

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