Exhaust gas purification catalyst device

Abstract

To provide an exhaust gas purification catalyst device having sufficiently high purification efficiency of NOx, and less in a generation amount of N2O.SOLUTION: An exhaust gas purification catalyst device comprises a substrate and a catalyst coating layer on the substrate, wherein the catalyst coating layer contains a Cu-CHA type zeolite and when analyzed by an electron probe microanalyzer before use, sulfur atoms are observed over an entire region in a thickness direction of the catalyst coating layer, and a ratio of an amount (mol) of sulfur atoms to the amount (mol) of Cu atoms in the Cu-CHA type zeolite is 0.05 or more and 1.00 or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] The selective catalytic reduction (SCR) system is known as a technology for reducing and purifying NOx in exhaust gas emitted from diesel engines before it is released into the atmosphere. The SCR system uses a reducing agent, such as ammonia (or an ammonia source such as urea), to reduce NOx in the exhaust gas. x This is a technology that reduces nitrogen to nitrogen.

[0003] In this SCR system, Cu-zeolite, which is made by ion-exchanging zeolite with copper (Cu) and has a low silica-to-alumina ratio (SAR), is known to have excellent NOx purification capacity in the low temperature range.

[0004] For example, Patent Document 1 describes a bimetallic catalyst for selective ammonia oxidation, which comprises a molecular sieve having a silica-to-alumina ratio (SAR) of less than 30, and the molecular sieve comprises ion-exchanged copper (Cu) and ion-exchanged platinum (Pt).

[0005] Furthermore, Patent Document 2 explains that an exhaust gas purification catalyst using Cu-CHA type zeolite, in which chabazite type zeolite, represented by the structural code "CHA," is ion-exchanged with copper (Cu), has excellent NOx purification ability. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Special Publication No. 2012-507400 [Patent Document 2] International Publication No. 2008 / 106519 Summary of the Invention [Problem to be solved by the invention]

[0007] In SCR systems, low-SAR Cu-zeolite has excellent NOx purification capabilities at low temperatures, but produces NO as a by-product. NO is a greenhouse gas that contributes to global warming, so its emissions should be reduced.

[0008] The present invention has been made in view of the above circumstances, and its object is to provide an exhaust gas purification catalyst device which has a sufficiently high NOx purification efficiency and produces a small amount of N2O. [Means for solving the problem]

[0009] The present invention, which solves the above problems, is as follows.

[0010] Aspect 1: An exhaust gas purification catalyst device including a substrate and a catalyst coating layer on the substrate, the catalyst coating layer contains Cu-CHA type zeolite, Before use, When analyzed by an electron beam microanalyzer, sulfur atoms are observed throughout the entire thickness direction of the catalyst coating layer, and The ratio of the amount (mol) of sulfur atoms to the amount (mol) of Cu atoms in the Cu-CHA type zeolite is 0.05 or more and 1.00 or less. Exhaust gas purification catalytic device. Aspect 2: The exhaust gas purification catalyst device according to Aspect 1, wherein, when the catalyst coating layer is analyzed by an electron probe microanalyzer before use, the ratio C1 / C9 of the sulfur atomic concentration C1 at the outermost surface to the sulfur atomic concentration C9 at the innermost depth is 1.5 or less when the catalyst coating layer is divided into nine depth-wise sections from the outermost surface to the innermost depth. Aspect 3: The exhaust gas purification catalyst device according to aspect 1 or 2, wherein the ratio of the amount (moles) of sulfur atoms to the amount (moles) of Cu atoms in the Cu-CHA type zeolite is 0.10 or more and 0.50 or less. Aspect 4: An exhaust gas purification catalyst device according to any one of aspects 1 to 3, wherein the amount of Cu in the Cu-CHA type zeolite is 0.10 mol / mol-Al or more and 0.40 mol / mol-Al or less, relative to 1 mole of Al atoms in the Cu-CHA type zeolite. Aspect 5: The catalytic device for purifying exhaust gas according to any one of Aspects 1 to 4, wherein the Cu-CHA type zeolite has a silica-alumina ratio (SAR) of 7.5 or more and 15.0 or less. Aspect 6: The catalytic device for purifying exhaust gas according to any one of Aspects 1 to 5, which is an SCR catalytic device. Aspect 7: Preparing a coating liquid containing Cu-CHA zeolite and a sulfur source; Coating the coating liquid on a substrate to obtain a coating layer; and baking the coating to form a catalyst coating layer on the substrate; A method for manufacturing an exhaust gas purification catalyst device, comprising: Aspect 8: The method according to aspect 7, wherein the sulfur source is an organic sulfur compound having a sulfur atom and one or two functional groups selected from a hydroxyl group and a carboxyl group. Aspect 9: The method of aspect 8, wherein the sulfur source is one or more selected from taurine and cysteine. [Effects of the Invention]

[0011] According to the present invention, there is provided an exhaust gas purification catalyst device which has a sufficiently high NOx purification efficiency and produces a small amount of N2O. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a graph showing the desorption behavior of NH 3 adsorbed on the exhaust gas purification catalytic devices obtained in Examples 3 and 4 and Comparative Example 1. [Figure 2] FIG. 2 shows sulfur atom mapping of the exhaust gas purification catalyst device obtained in Example 3 before the hydrothermal durability treatment, measured by EPMA. [Figure 3]FIG. 3 shows sulfur atom mapping of the exhaust gas purification catalyst device obtained in Example 3 after hydrothermal durability treatment, measured by EPMA. [Figure 4] FIG. 4 shows sulfur atom mapping of the exhaust gas purification catalyst device obtained in Comparative Example 5 after sulfur poisoning in an actual device, measured by EPMA. DETAILED DESCRIPTION OF THE INVENTION

[0013] <Exhaust gas purification catalyst device> The exhaust gas purification catalyst device of the present invention is An exhaust gas purification catalyst device comprising a substrate and a catalyst coating layer on the substrate, the catalyst coating layer contains Cu-CHA type zeolite, Before use, When analyzed by an electron beam microanalyzer, sulfur atoms are observed throughout the entire thickness direction of the catalyst coating layer, and The ratio of the amount (mol) of sulfur atoms to the amount (mol) of Cu atoms in the Cu-CHA type zeolite is 0.05 or more and 1.00 or less. It is an exhaust gas purification catalytic device.

[0014] The exhaust gas purification catalyst device of the present invention uses Cu-CHA type zeolite. As described above, Cu-zeolite has excellent NOx purification ability. Furthermore, in the exhaust gas purification catalyst device of the present invention, when a catalyst coating layer containing such Cu-CHA type zeolite is analyzed by an electron probe microanalyzer (EPMA) before use, sulfur atoms are observed throughout the entire thickness direction of the catalyst coating layer. The distribution of sulfur atoms in the thickness direction of the catalyst coating layer is preferably approximately uniform.

[0015] The reason why the amount of N2O emissions is reduced in such an exhaust gas purification catalytic device of the present invention is presumed to be as follows.

[0016] The mechanism by which NOx is purified by the SCR reaction is thought to be the following main reactions (1) and (2). 2NO+4NH3+2O2→3N2+6H2O (1) 2NO2 + 2NO + 2NH3 → 3N2 + 3H2O (2)

[0017] During this SCR reaction, the following side reactions (3) and (4) are thought to occur, resulting in the production of N2O. 2NO2+2NH3→NH4NO3+N2+H2O (3) NH4NO3→N2O+2H2O (4)

[0018] In exhaust gas purification catalyst devices using Cu-CHA type zeolite, it is believed that NH3 adsorbed to Lewis acid sites (Cu ions, etc.) in the catalyst coating layer contributes to the above-mentioned side reaction (3). In the exhaust gas purification catalyst device of the present invention, sulfur components are present in the catalyst coating layer, preferably with a uniform distribution in the thickness direction. It is presumed that these sulfur components cover part of the Lewis acid sites in the catalyst coating layer, reducing the amount of NH3 adsorbed, thereby suppressing the progress of side reaction (3) and reducing the amount of N2O produced via NH4NO3.

[0019] Surprisingly, even if the sulfur components in the catalyst coating layer cover some of the Lewis acid sites in the catalyst coating layer and suppress the progress of side reaction (3), it is believed that the progress of the above-mentioned main reactions (1) and (2) is not hindered. Therefore, in the exhaust gas purification catalyst device of the present invention, the NO2 purification performance is not impaired at all or almost not at all. This is presumably because the NH3 adsorption sites that contribute to the progress of side reaction (3) are different from the sites that contribute to the progress of main reactions (1) and (2), and the sulfur components preferentially cover the former NH3 adsorption sites.

[0020] It is believed that the exhaust gas purification device of the present invention has a sufficiently high NOx purification efficiency and produces a small amount of N2O due to the above-mentioned mechanism of action, but the present invention is not bound by any particular theory.

[0021] Each element of the exhaust gas purification device of the present invention will be described in detail below.

[0022] 《Base material》 The substrate in the exhaust gas purification catalyst device of the present invention may be appropriately selected from known substrates depending on the purpose. The constituent material of the substrate may be, for example, cordierite, metal, etc. The substrate may be of a straight flow type or a wall flow type.

[0023] The substrate in the catalytic device for purifying exhaust gas of the present invention may typically be, for example, a monolith honeycomb substrate of a straight-flow type or a wall-flow type made of cordierite.

[0024] <<Catalyst Coating Layer>> The catalyst coating layer in the exhaust gas purification catalytic device of the present invention is present on a substrate. The catalyst coating layer being present on a substrate means at least one of the following: the catalyst coating layer being present in a layered state on the cell walls that define the cells of the substrate (on the cell-side surfaces of the cell walls), and the catalyst coating layer being present by penetrating into the interior of the cell walls (pores extending in the depth direction of the cell walls). The catalyst coating layer may, for example, include at least a portion that is present in a layered state on the cell walls that define the cells of the substrate.

[0025] <Cu-CHA type zeolite> The catalyst coating layer in the exhaust gas purification catalytic device of the present invention contains Cu-CHA type zeolite. "Cu-CHA type zeolite" is a chabazite type zeolite, which is represented by the structure code "CHA", ion-exchanged with Cu and doped with Cu.

[0026] The Cu-CHA zeolite in the present invention may have a silica-alumina ratio (SAR) of 15.0 or less. By using a Cu-CHA zeolite with an SAR of 15.0 or less, the NOx purification rate by the SCR reaction, particularly in the low temperature range, becomes high. This SAR value is expressed as the ratio (SiO2 / Al2O3) of the molar amount of silica (SiO2) to the molar amount of alumina (Al2O3) in the zeolite.

[0027] From the viewpoint of increasing the NOx purification rate, the SAR of the Cu-CHA zeolite in the present invention may be 14.0 or less, 13.0 or less, 12.0 or less, 11.0 or less, 10.0 or less, 9.0 or less, or 8.0 or less. On the other hand, if the SAR is too low, it may be difficult to synthesize the zeolite, which may result in an excessive increase in catalyst costs. To avoid such a situation, the SAR of the Cu-CHA zeolite may be 4.0 or more, 5.0 or more, 6.0 or more, or 7.0 or more.

[0028] The SAR of the Cu-CHA zeolite in the present invention may typically be, for example, 7.5 or more and 15.0 or less.

[0029] From the viewpoint of increasing the SCR activity of the exhaust gas purification catalyst device of the present invention, the amount of Cu in the Cu-CHA type zeolite may be 0.10 mol / mol-Al or more, 0.15 mol / mol-Al or more, 0.20 mol / mol-Al or more, 0.25 mol / mol-Al or more, or 0.30 mol / mol-Al or more per mole of Al atom in the Cu-CHA type zeolite.

[0030] There is no upper limit on the amount of Cu in Cu-CHA zeolite from the viewpoint of SCR activity. However, even if the amount of Cu in Cu-CHA zeolite is excessively increased, the SCR activity does not increase without limit. Therefore, from the viewpoint of maintaining the manufacturing cost of the exhaust gas purification catalyst device at an appropriate level, the amount of Cu in Cu-CHA zeolite may be 0.50 mol / mol-Al or less, 0.45 mol / mol-Al or less, 0.40 mol / mol-Al or less, 0.35 mol / mol-Al or less, 0.30 mol / mol-Al or less, or 0.25 mol / mol-Al or less, relative to 1 mole of Al atoms in the Cu-CHA zeolite.

[0031] The amount of Cu in the Cu-CHA zeolite may typically be, for example, 0.10 mol / mol-Al or more and 0.40 mol / mol-Al or less relative to 1 mole of Al atoms in the Cu-CHA zeolite.

[0032] <Sulfur components> When the exhaust gas purification catalyst device of the present invention is analyzed by an electron probe microanalyzer (EPMA) before use, sulfur atoms are observed throughout the entire thickness of the catalyst coating layer, and the distribution of sulfur atoms in the thickness of the catalyst coating layer is preferably nearly uniform.

[0033] The sulfur atoms observed by EPMA analysis of the catalyst coating layer of the exhaust gas purification catalytic device of the present invention may be any chemical species. Hereinafter, in this specification, chemical species containing sulfur atoms may be collectively referred to as "sulfur components."

[0034] Quantitatively, when the exhaust gas purification catalyst device of the present invention is analyzed by EPMA before use, the ratio C1 / C9 of the sulfur atomic concentration C1 in the outermost surface portion to the sulfur atomic concentration C9 in the innermost portion when the catalyst coating layer is divided into nine portions in the depth direction from the outermost surface to the innermost portion may be 1.5 or less, 1.4 or less, 1.3 or less, or 1.2 or less.

[0035] The ratio C1 / C9 is ideally 1.0. However, even if the distribution of sulfur atoms in the thickness direction of the catalyst coating layer is not completely uniform, the desired effect of the present invention can be achieved as long as the ratio C1 / C9 is 1.5 or less. Therefore, the ratio C1 / C9 may be, for example, 0.9 or more, 1.0 or more, or 1.1 or more.

[0036] When an exhaust gas purification catalyst device is installed in the exhaust system of a real vehicle and used in practice, it is thought that the catalyst coating layer will be sulfur-poisoned by sulfur components contained in the fuel. EPMA analysis of such a sulfur-poisoned catalyst coating layer detects sulfur atoms. However, in a sulfur-poisoned catalyst coating layer, the sulfur components are unevenly distributed in the region near the surface of the catalyst coating layer.

[0037] Interestingly, the inventors' investigations revealed that when a catalyst coating layer in which sulfur components are concentrated in the region near the surface is used, the amount of N2O produced is reduced, but the NOx purification performance is significantly impaired.

[0038] This is thought to be because in a sulfur-poisoned catalyst coating layer, an excessive amount of sulfur components covers not only the NH3 adsorption sites that contribute to the production of N2O via NH4NO3, but also the sites that contribute to NOx purification near the surface of the coating layer that first comes into contact with exhaust gas, resulting in a decrease in the amount of N2O produced and a decrease in NOx purification activity.

[0039] In contrast, in the exhaust gas purification catalyst device of the present invention, the sulfur components are uniformly dispersed in the catalyst coating layer, and in particular, the sulfur components are uniformly dispersed at an appropriate concentration in the catalyst coating layer. As a result, the NH3 adsorption points that contribute to the production of N2O via NH4NO3 are covered throughout the entire thickness direction of the catalyst coating layer, while the sites that contribute to NOx purification are not covered, and it is thought that NOx purification activity is maintained.

[0040] In the present invention, the ratio of the amount (moles) of sulfur atoms to the amount (moles) of Cu atoms in the Cu-CHA zeolite is 0.05 or more and 1.00 or less. From the viewpoint of further suppressing the amount of NO produced, the ratio of the amount (moles) of sulfur atoms to the amount (moles) of Cu atoms in the Cu-CHA zeolite is 0.05 or more, and may be 0.10 or more, 0.15 or more, 0.20 or more, 0.25 or more, or 0.30 or more. On the other hand, from the viewpoint of maintaining a high level of NOx purification performance, this ratio may be 1.00 or less, and may be 0.80 or less, 0.50 or less, 0.40 or less, 0.35 or less, 0.30 or less, or 0.25 or less.

[0041] The ratio of the amount (moles) of sulfur atoms to the amount (moles) of Cu atoms in the Cu-CHA zeolite may typically be 0.10 or more and 0.50 or less.

[0042] In the exhaust gas purification catalyst device of the present invention, the amount of sulfur atoms supported may be 0.05 g / substrate-L or more, or 0.10 g / substrate-L or more, and may be 3.0 g / substrate-L or less, 2.5 g / substrate-L or less, 2.0 g / substrate-L or less, 1.5 g / substrate-L or less, or 1.0 g / substrate-L or less.

[0043] The amount of sulfur atoms in the catalyst coating layer of the exhaust gas purification catalyst device of the present invention may be quantified, for example, by the following method. For example, the exhaust gas purification catalyst device is pulverized to prepare a fine powder sample, which is then combusted in a carbon-sulfur analyzer (CS analyzer). The amounts of CO2 and SO2 generated are measured, and the carbon content (mass%) and sulfur content (mass%) in the fine powder sample are quantified. Then, the amount of components derived from the substrate are removed from the obtained quantitative value, and the mass percentage is converted to the mass per liter of substrate, thereby determining the amount of sulfur atoms in the catalyst coating layer.

[0044] <Optional ingredients> In the exhaust gas purification catalyst device of the present invention, the catalyst coating layer may contain optional components other than the Cu-CHA type zeolite and the sulfur component, such as inorganic oxides other than the Cu-CHA type zeolite, alkali metals, alkaline earth metals, noble metals, binders, etc.

[0045] The inorganic oxide other than Cu-CHA zeolite contained in the catalyst coating layer may be, for example, an oxide of one or more elements selected from aluminum, silicon, titanium, zirconium, rare earth elements, etc. Specific examples of inorganic oxides include alumina, zirconia, etc.

[0046] The noble metal may be selected from platinum group elements, particularly palladium (Pd), platinum (Pt), and rhodium (Rh). The noble metal may be supported on one or more of Cu-CHA type zeolite and inorganic oxides other than Cu-CHA type zeolite.

[0047] The binder contained in the catalyst coating layer may be, for example, alumina sol, zirconia sol, silica sol, titania sol, or the like.

[0048] The amount of the specified Cu-CHA type zeolite of the present invention contained in the catalyst coating layer of the exhaust gas purification catalyst device of the present invention may be 40 mass% or more, 50 mass% or more, 60 mass% or more, 70 mass% or more, or 80 mass% or more, relative to the total mass of the catalyst coating layer, and may be 100 mass% or less, 99 mass% or less, or 95 mass% or less.

[0049] <<Uses of exhaust gas purification catalyst devices>> The catalytic device for purifying exhaust gas of the present invention may be suitably used as an SCR catalytic device using ammonia as a reducing agent. The ammonia source as a reducing agent supplied to the catalytic device for purifying exhaust gas of the present invention may be ammonia, urea, etc.

[0050] <<Method for manufacturing an exhaust gas purification catalyst device>> The exhaust gas purification catalyst device of the present invention may be produced by any method as long as it has the above-mentioned configuration.

[0051] The exhaust gas purification catalyst device of the present invention may be produced, for example, by the following method: preparing a coating liquid containing Cu-CHA zeolite and a sulfur source; Coating the coating liquid on a substrate to obtain a coating layer; and baking the coating to form a catalyst coating layer on the substrate; A method for manufacturing an exhaust gas purification catalyst device, comprising:

[0052] <Base material> The substrate may be appropriately selected depending on the substrate of the desired exhaust gas purification catalytic device, and may be, for example, a straight-flow monolith honeycomb substrate made of cordierite.

[0053] <Coating liquid> The coating liquid contains Cu-CHA type zeolite and a sulfur source.

[0054] The Cu-CHA type zeolite may be appropriately selected depending on the Cu-CHA type zeolite contained in the catalyst coating layer of the desired exhaust gas purification catalyst device. For example, it may be a Cu-CHA type zeolite having a silica-alumina ratio (SAR) of 7.5 or more and 15.0 or less, and having a Cu amount per mole of Al atom of 0.10 mol / mol-Al or more and 0.40 mol / mol-Al or less.

[0055] (sulfur source) The sulfur source may be an organic sulfur compound having a sulfur atom and one or two functional groups selected from a hydroxyl group and a carboxyl group. When the sulfur source has one or two functional groups selected from a hydroxyl group and a carboxyl group, the affinity with the substrate is increased, and the sulfur component preferably remains in the catalyst coating layer even after calcination.

[0056] The sulfur source contained in the coating liquid may be one or two selected from taurine and cysteine.

[0057] The amount of sulfur source in the coating liquid, as the ratio of the amount of sulfur atoms (moles) to the amount of Cu atoms (moles) in the Cu-CHA type zeolite (S / Cu ratio), may be 0.3 or more, 0.5 or more, 0.7 or more, 1.0 or more, 1.2 or more, or 1.5 or more from the viewpoint of further suppressing the amount of NO produced, and may be 3.0 or less, 2.5 or less, 2.2 or less, 2.0 or less, 1.8 or less, or 1.5 or less from the viewpoint of maintaining high NOx purification performance.

[0058] (solvent) The coating liquid may contain a suitable solvent, and each component may be dissolved or dispersed in the solvent. The solvent may be one or more selected from water and water-soluble organic solvents. The water-soluble organic solvent may be, for example, alcohol. The solvent for the coating liquid in the present invention is typically water.

[0059] The coating liquid of the present invention may further contain optional components such as an acid, a base, a thickener, a preservative, and an antifoaming agent in addition to the Cu-CHA type zeolite, a sulfur source, and a solvent.

[0060] (Coating and baking of coating liquid) Coating with the coating liquid and baking may be carried out by a known method or a method with appropriate modifications made by a person skilled in the art. [Example]

[0061] <<Manufacturing of exhaust gas purification catalyst devices>> Example 1 Cu-CHA type zeolite A (SAR 7.5, Cu ion exchange capacity 0.25 mol / mol-Al) was added to pure water, and a pH adjuster and dispersant were added while stirring to adjust the pH to within the range of 7 to 10. Silica sol as a binder and taurine as a sulfur source were then added, and the mixture was stirred at room temperature for 30 minutes to obtain a raw material mixture. The amount of taurine added was 0.31 mol per 1 mol of Cu atoms in the Cu-CHA type zeolite.

[0062] The obtained raw material mixture was subjected to wet pulverization using a bead mill to obtain granules having an average particle size D50 of 1.5 to 1.5 mm. The mixture was pulverized to a particle size of 4.0 μm to obtain a washcoat slurry.

[0063] The washcoat slurry was applied to a cordierite straight-flow honeycomb substrate with rectangular cell cross-sections, followed by firing at 500°C for 2 hours to form a catalytic coating layer, yielding an exhaust gas purification catalyst device. The amount of sulfur atoms contained in the catalytic coating layer of this exhaust gas purification catalyst device per 1 L of honeycomb substrate was determined to be 0.21 g / L using a carbon-sulfur analyzer.

[0064] In the exhaust gas purification catalyst device obtained in this example, the ratio of the amount (mol) of sulfur atoms to the amount (mol) of Cu atoms in the Cu-CHA type zeolite was 0.059.

[0065] Examples 2 to 7 and Comparative Examples 1 to 5 Exhaust gas purification catalyst devices were produced in the same manner as in Example 1, except that the type of Cu-CHA zeolite and the type and amount of the sulfur source added to the raw material mixture were changed as shown in Table 2. In Comparative Examples 1 and 5, no sulfur source was used.

[0066] The "Cu-CHA type zeolite B" used in Example 7 and Comparative Example 5 is a zeolite with SAR14 and a Cu ion exchange amount of 0.35 mol / mol-Al.

[0067] Comparative Example 6 A catalytic device for purifying exhaust gases manufactured in the same manner as in Comparative Example 1 was subjected to sulfur poisoning under the following conditions to obtain an actual sulfur-poisoned catalytic device for purifying exhaust gases.

[0068] The obtained pre-sulfur-poisoned exhaust gas purification catalyst device was installed in the exhaust system of a 2,800cc diesel engine vehicle, and the engine was operated using diesel fuel with a sulfur content of 420 ppm. Exhaust gas was passed through the catalyst at an inlet temperature of 350°C for 20 minutes to perform sulfur poisoning. The amount of sulfur contained in the passed exhaust gas per 1 L of honeycomb substrate was 9.1 g / L, and the amount of sulfur poisoning was 0.59 g / L.

[0069] The sulfur poisoning conditions employed in this comparative example were an accelerated sulfur poisoning test.

[0070] 《Rating 1: SCR Performance》 The exhaust gas purification catalyst devices obtained in each of the Examples and Comparative Examples were subjected to hydrothermal durability treatment under the conditions below, and then the SCR performance (NOx purification rate and N2O production amount) was evaluated.

[0071] <Hydrothermal durability treatment> The obtained exhaust gas purification catalyst device was subjected to hydrothermal durability treatment by heating it in air containing 10% by volume of water vapor at 630°C for 50 hours.

[0072] Evaluation of SCR responses After the hydrothermal durability treatment, the inlet gas temperature of the exhaust gas purification catalyst device was raised from room temperature to 600°C at a rate of 20°C / min. The gas of "Composition 1" shown in Table 1 was passed through the catalyst for SV83,000h. -1 Next, the gas (nitrogen gas) of the composition 2 shown in Table 1 was introduced at a flow rate of SV83,000h while the inlet gas temperature was decreased from 600°C to 200°C at a rate of 10°C / min. -1 The temperature was lowered by flowing the solution at a flow rate of 1000 kJ / min.

[0073] After that, the gas temperature was increased stepwise by 50°C from 200°C, and the gas of the composition 3 shown in Table 1 was used for SV83,000h. -1 The amount of NO generated and the NOx conversion rate at each temperature were monitored. Each temperature was maintained for 10 minutes, and the temperature was increased at a rate of 20°C / min. The flow of the gas of composition 3 was continued during the temperature increase. The concentrations of each component in Table 1 are based on volume.

[0074] Table 2 shows the amount of N2O generated (amount of N2O in exhaust gas (ppm)) and NOx purification rate (percentage (%) of NOx concentration in exhaust gas relative to the NOx concentration in inlet gas) at 250°C for the exhaust gas purification catalyst devices of each Example and Comparative Example.

[0075] Table 3 also shows the amount of N2O generated and the NOx purification rate at each temperature for the exhaust gas purification catalyst devices obtained in Example 2 and Comparative Example 1.

[0076] [Table 1]

[0077] [Table 2]

[0078] [Table 3]

[0079] In the exhaust gas purification devices of Examples 1 to 6, the catalyst coating layer contains "Cu-CHA type zeolite A" and 0.05 moles or more of sulfur components per mole of Cu in the Cu-CHA type zeolite. In contrast, in the exhaust gas purification device of Comparative Example 1, the catalyst coating layer contains "Cu-CHA type zeolite A" but does not contain sulfur components. Furthermore, in the exhaust gas purification devices of Comparative Examples 2 to 4, the catalyst coating layer contains "Cu-CHA type zeolite A" and sulfur components, but the amount of sulfur components per mole of Cu in the Cu-CHA type zeolite is less than 0.05 moles. Furthermore, the exhaust gas purification device of Comparative Example 6 is the exhaust gas purification device of Comparative Example 1 mounted on an actual vehicle (actual machine) and subjected to sulfur poisoning.

[0080] According to Table 2, it was confirmed that, compared to the exhaust gas purification apparatus of Comparative Example 1, the exhaust gas purification apparatuses of Examples 1 to 6, in which the catalyst coating layer contained 0.05 moles or more of sulfur components per mole of Cu in the Cu-CHA type zeolite, reduced the amount of NO produced without impairing the NOx purification rate at 250° C. In contrast, the exhaust gas purification apparatuses of Comparative Examples 2 to 4, in which the amount of sulfur components per mole of Cu in the Cu-CHA type zeolite in the catalyst coating layer was less than 0.05 moles, did not show any effect in reducing the amount of NO produced.

[0081] Furthermore, compared to the exhaust gas purification device of Comparative Example 1, the exhaust gas purification device of Comparative Example 6, which has a catalyst coating layer that has been sulfur-poisoned by an actual device, reduced the amount of N2O produced, but the NOx purification rate was significantly impaired.

[0082] Referring to Table 3, it can be seen that, compared to the exhaust gas purification device of Comparative Example 1, the exhaust gas purification device of Example 2, in which the catalyst coating layer contains 0.116 moles of sulfur components per mole of Cu in the Cu-CHA type zeolite, reduces the amount of NO produced without impairing the NOx purification rate in the low temperature range of approximately 550°C or less.

[0083] In the exhaust gas purification device of Example 7, the catalyst coating layer contains "Cu-CHA type zeolite B" and 0.117 moles of sulfur components per mole of Cu in the Cu-CHA type zeolite. In contrast, in the exhaust gas purification device of Comparative Example 5, the catalyst coating layer contains "Cu-CHA type zeolite B" and does not contain sulfur components.

[0084] According to Table 2, it was confirmed that, compared to the exhaust gas purification device of Comparative Example 5, the exhaust gas purification device of Example 7 reduced the amount of N2O produced at 250°C without substantially impairing the NOx purification rate.

[0085] Evaluation 2: NH3 desorption profile The exhaust gas purification catalyst devices obtained in Examples 2 and 3 and Comparative Example 1 were examined for NH3 desorption profiles.

[0086] For each exhaust gas purification catalyst device, hydrothermal durability treatment was performed under the same conditions as the hydrothermal durability treatment performed prior to the evaluation of the SCR reaction. After that, the inlet gas temperature was raised from room temperature to 600°C at a rate of 20°C / min. The gas of "Composition 4" shown in Table 4 was used for SV83,000h. -1 Next, the gas (nitrogen gas) of the composition "Composition 5" shown in Table 4 was introduced at a flow rate of SV83,000h while the inlet gas temperature was decreased from 600°C to 100°C at a rate of 10°C / min. -1 The temperature was lowered by flowing the solution at a flow rate of 1000 kJ / min.

[0087] Furthermore, while maintaining the inlet gas temperature at 100°C, a gas with the composition "Composition 6" shown in Table 4 was passed for 50 minutes to adsorb NH3 into the exhaust gas purification catalyst device. After that, while increasing the inlet gas temperature from 100°C at a rate of 20°C / min, a gas with the composition "Composition 7" shown in Table 4 was passed for 83,000 hours. -1 The NH3 concentration in the exhaust gas was tracked by flowing the gas at a flow rate of 1000 kJ / min. The concentration of each component in Table 4 is based on the volume.

[0088] The results are shown in Figure 1.

[0089] [Table 4]

[0090] 1, the desorption of NH3 from the exhaust gas purification catalyst devices obtained in Examples 2 and 3 and Comparative Example 1 exhibited a two-peak desorption behavior, with a desorption peak having a peak top at about 180° C. and another peak having a peak top at about 220 to 230° C. Of these, the desorption peak having a peak top at about 180° C. is thought to be the desorption of NH3 physically adsorbed on the Lewis acid sites of the catalyst coating layer, and the desorption peak having a peak top at about 220 to 230° C. is thought to be the desorption of NH3 chemically adsorbed on the Lewis acid sites of the catalyst coating layer.

[0091] In the exhaust gas purification catalyst devices of Examples 2 and 3, the amount of NH3 desorbed from the Lewis acid sites was reduced compared to the exhaust gas purification catalyst device of Comparative Example 1. From this, it is presumed that the catalyst coating layer contains a sulfur component derived from a predetermined sulfur source, which reduces the number of Lewis acid sites in the catalyst coating layer, thereby reducing the amount of NH3 adsorption and the amount of N2O produced via NH4NO3.

[0092] Evaluation 3: Sulfur atom distribution The sulfur atom distribution of the exhaust gas purification catalyst device obtained in Example 2 was examined before and after hydrothermal durability treatment, and compared with the sulfur atom distribution of the exhaust gas purification catalyst device obtained in Comparative Example 6 after being subjected to sulfur poisoning in an actual machine.

[0093] Each exhaust gas purification catalyst device was cut into 1 cm squares and fixed using resin and a resin curing agent. After that, osmium was vapor-deposited to obtain an observation sample of a cross section perpendicular to the length direction of the honeycomb substrate. The obtained observation sample was examined by elemental analysis using electron beam microanalysis (EPMA) to obtain a sulfur atom map. The measurement conditions were as follows: Accelerating voltage: 20 kV Probe current: 100nA Acquisition time: 30ms Resolution: 256 x 256 pixels Sample heat history: None (measured freshly prepared sample) Observation magnification: 500x

[0094] The obtained sulfur atom mappings are shown in Figures 2 to 4. Figure 2 shows the sulfur atom mapping of the exhaust gas purification catalytic device obtained in Example 2 before the hydrothermal durability treatment, Figure 3 shows the sulfur atom mapping of the exhaust gas purification catalytic device obtained in Example 2 after the hydrothermal durability treatment, and Figure 4 shows the sulfur atom mapping of the exhaust gas purification catalytic device obtained in Comparative Example 6 after the actual device was sulfur-poisoned.

[0095] In these sulfur atom mappings, the catalyst coating layer was divided into nine equal sections in the depth direction along an imaginary line extending from the center of the rectangular cell cross section to one of the corners. The sulfur atom concentrations in the nine regions were then read from the sulfur atom mapping color scale. The sulfur atom concentrations in the nine regions were designated C1, C2, ... C9, starting from the shallowest, and evaluated as relative values to the sulfur atom concentration C9 at the deepest point.

[0096] The results are shown in Table 5.

[0097] [Table 5]

[0098] 2 and 3, and Table 5, in the exhaust gas purification catalyst device before the hydrothermal durability test in Example 2, sulfur atoms were observed at a substantially uniform concentration throughout the entire region in the thickness direction of the catalyst coating layer in the EPMA analysis. In contrast, in the exhaust gas purification device of Comparative Example 6, which had a catalyst coating layer that had been sulfur-poisoned in an actual test, sulfur atoms were unevenly distributed in the region near the surface of the catalyst coating layer.

[0099] Furthermore, even after the catalytic device for purifying exhaust gas of Example 2 was subjected to hydrothermal durability testing, no substantial change was observed in the distribution of sulfur atoms in the thickness direction of the catalyst coating layer.

Claims

1. An exhaust gas purification catalyst device comprising a substrate and a catalyst coating layer on the substrate, the catalyst coating layer contains Cu-CHA type zeolite, Before use, When analyzed by an electron beam microanalyzer, sulfur atoms are observed throughout the entire region of the catalyst coating layer in the thickness direction, and the ratio of the amount (mol) of sulfur atoms to the amount (mol) of Cu atoms in the Cu-CHA type zeolite is 0.05 or more and 1.00 or less; Exhaust gas purification catalytic device.

2. When the catalyst coating layer was analyzed by an electron microanalyzer before use, the sulfur atom concentration C of the outermost surface portion was determined by dividing the catalyst coating layer into nine portions in the depth direction from the outermost surface to the deepest portion. １ and the sulfur atom concentration C at the deepest part ９ Relative to C １ / C ９ 2. The exhaust gas purification catalyst device according to claim 1, wherein the ratio of the total mass of the exhaust gas to the total mass of the catalyst is 1.5 or less.

3. the ratio of the amount (mol) of sulfur atoms to the amount (mol) of Cu atoms in the Cu-CHA type zeolite is 0.10 or more and 0.50 or less; 3. The exhaust gas purification catalyst device according to claim 1 or 2.

4. The exhaust gas purification catalyst device according to any one of claims 1 to 3, wherein the Cu amount in the Cu-CHA type zeolite is 0.10 mol / mol-Al or more and 0.40 mol / mol-Al or less relative to 1 mole of Al atoms in the Cu-CHA type zeolite.

5. 5. The exhaust gas purification catalyst device according to claim 1, wherein the Cu-CHA type zeolite has a silica-alumina ratio (SAR) of 7.5 or more and 15.0 or less.

6. The exhaust gas purification catalyst device according to any one of claims 1 to 5, which is an SCR catalyst device.

7. A method for manufacturing an exhaust gas purification catalyst device according to any one of claims 1 to 6, comprising: preparing a coating liquid containing Cu-CHA type zeolite and a sulfur source; Coating the coating liquid on a substrate to obtain a coating layer; and baking the coating to form a catalyst coating layer on the substrate; Including, A method for manufacturing an exhaust gas purification catalyst device.

8. 8. The method according to claim 7, wherein the sulfur source is an organic sulfur compound having a sulfur atom and one or two functional groups selected from a hydroxyl group and a carboxyl group.

9. The method according to claim 8, wherein the sulfur source is one or two selected from taurine and cysteine.

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