Exhaust gas purification catalyst system

Abstract

To provide a lamination type SCR-ASC which is excellent in initial activity and is also excellent in ammonia purification performance at low temperatures after hydrothermal endurance.SOLUTION: An exhaust gas purification catalyst device has a honeycomb substrate having a plurality of exhaust gas flow channels divided by partition walls, a catalyst noble metal particle support layer in or on the partition walls of the substrate, and a zeolite layer containing copper ion exchange zeolite on a side closer to the exhaust gas flow channel than the catalyst noble metal particle support layer, wherein the catalyst noble metal particle support layer contains catalyst noble metal particles, inorganic oxide particles other than silica are contained between the catalyst noble metal particle support layer and the zeolite layer, and a content of the catalyst noble metal is less than 0.01 g / L.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] As a technique for reducing and purifying NOx in exhaust gas discharged from a diesel engine before it is released into the atmosphere, a selective catalytic reduction (SCR) system is known. The SCR system is a technique for reducing NO in exhaust gas to N2 using a reducing agent, for example, ammonia. x to N2.

[0003] In this SCR system, Cu-zeolite obtained by ion-exchanging zeolite with a low silica / alumina ratio (SAR) with copper (Cu) is known to be excellent in NOx purification ability in the low temperature range.

[0004] For example, in Patent Document 1, an exhaust gas purification catalyst using Cu-CHA type zeolite obtained by ion-exchanging chabazite type zeolite represented by the structure code "CHA" with copper (Cu) is described as being excellent in NOx purification ability.

[0005] In this SCR system, in order to improve the reduction purification rate of NO x , a reducing agent may be used in excess. In this case, the unreacted reducing agent that was not used for the reduction of NO x is discharged from the SCR catalyst. When ammonia is used as the reducing agent, the discharge of ammonia from the SCR catalyst is sometimes called "ammonia slip".

[0006] It is desirable that the slipped ammonia be purified (oxidatively purified) by an ASC (Ammonia Slip Catalyst) and then released into the atmosphere. Therefore, in the SCR system, the ASC is often used in combination, for example, laminated with the SCR layer or arranged in the subsequent stage of the SCR layer.

[0007] As an example of ASC, Patent Document 2 describes a catalyst in which an oxidation catalyst metal consisting of platinum or a combination of platinum and palladium is supported on a metal oxide support with a high surface area. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Special Publication No. 2012-507400 [Patent Document 2] Special Publication No. 2016-532548 [Overview of the project] [Problems that the invention aims to solve]

[0009] In SCR systems, stacking the SCR layer and ASC layer allows for a more compact exhaust gas purification catalyst, which is advantageous in terms of exhaust system design. However, while such stacked SCR-ASC systems exhibit excellent initial activity, their NH3 purification performance may deteriorate after hydrothermal endurance.

[0010] Therefore, the present invention aims to provide a stacked SCR-ASC that exhibits excellent initial activity and also excellent ammonia purification performance at low temperatures after hydrothermal endurance. [Means for solving the problem]

[0011] The present invention is as follows:

[0012] <Aspect 1> A honeycomb substrate having multiple exhaust gas passages partitioned by partition walls, The catalyst noble metal particle supporting layer within or on the partition wall of the substrate, and A zeolite layer containing copper ion exchange zeolite, located on the exhaust gas flow path side of the catalyst noble metal particle supporting layer. An exhaust gas purification catalyst device having, The catalyst noble metal particle supporting layer contains catalyst noble metal particles, The material further comprises an inorganic oxide particle layer between the catalyst noble metal particle-supported layer and the zeolite layer, the inorganic oxide particle layer containing inorganic oxide particles other than silica and having a catalyst noble metal content of less than 0.01 g / L. Exhaust gas purification catalyst device. <Aspect 2> The exhaust gas purification catalyst apparatus according to aspect 1, wherein the coating thickness of the inorganic oxide particle layer is 2.0 μm or more and 25.0 μm or less. <Aspect 3> The exhaust gas purification catalyst apparatus according to aspect 1 or 2, wherein the inorganic oxide particles contained in the inorganic oxide particle layer are particles of oxides of one or more metals selected from Ce, Ti, Zr, Al, La, Fe, Co, Mn, V, W, Cu, and Ni. <Aspect 4> An exhaust gas purification catalyst device according to any one of aspects 1 to 3, wherein the particle size (D50) of the inorganic oxide particles contained in the inorganic oxide particle layer is 0.5 μm or more and 5.0 μm or less. <Aspect 5> An exhaust gas purification catalyst device according to any one of aspects 1 to 4, wherein the silica-alumina ratio (SAR) of the copper ion-exchange type zeolite contained in the zeolite layer is 15.0 or less. Appearance 6: An exhaust gas purification catalyst apparatus according to any one of Appearances 1 to 5, wherein the amount of Cu in the copper ion exchange zeolite contained in the zeolite layer is 0.10 mol or more and 0.50 mol or less per mole of Al atoms in the copper ion exchange zeolite. <Aspect 7> An exhaust gas purification catalyst device according to any one of aspects 1 to 6, wherein the amount of copper ion exchange zeolite in the zeolite layer is 30 g / L or more and 200 g / L or less. <Aspect 8> An exhaust gas purification catalyst device according to any one of aspects 1 to 7, wherein the copper ion exchange zeolite is a Cu-CHA type zeolite. <Aspect 9> The exhaust gas purification catalyst apparatus according to any one of aspects 1 to 7, wherein the catalyst precious metal particle supporting layer contains particles of a catalyst precious metal selected from Pt, Rh, and Pd. <Aspect 10> An exhaust gas purification catalyst apparatus according to any one of aspects 1 to 9, wherein the catalyst precious metal particles are directly supported within the partition wall of the substrate to form a catalyst precious metal particle supported layer. <<Aspect 11>> The exhaust gas purification catalyst device according to any one of Aspects 1 to 9, wherein the catalytic noble metal particles are supported on inorganic oxide particles other than silica, and the catalytic noble metal particles supported on the inorganic oxide particles other than silica are disposed on the partition walls of the base material to form a catalytic noble metal particle support layer.

Advantages of the Invention

[0013] According to the present invention, there is provided a laminated SCR-ASC that is particularly excellent in the purification performance of ammonia at low temperatures after hydrothermal durability.

Brief Description of the Drawings

[0014] [Figure 1] FIG. 1 is a scanning electron microscope image of the exhaust gas purification catalyst device obtained in Example 1. [Figure 2] FIG. 2 is a scanning electron microscope image of the exhaust gas purification catalyst device obtained in Comparative Example 1.

Modes for Carrying Out the Invention

[0015] <<Exhaust Gas Purification Catalyst Device>> The exhaust gas purification catalyst device of the present invention has a honeycomb base material having a plurality of exhaust gas flow paths partitioned by partition walls, a catalytic noble metal particle support layer inside or on the partition walls of the base material, and a zeolite layer containing copper ion-exchanged zeolite on the exhaust gas flow path side of the catalytic noble metal particle support layer is an exhaust gas purification catalyst device, wherein the catalytic noble metal particle support layer contains catalytic noble metal particles, and further has an inorganic oxide particle layer containing inorganic oxide particles other than silica and having a catalytic noble metal content of less than 0.01 g / L between the catalytic noble metal particle support layer and the zeolite layer. It is an exhaust gas purification catalyst device.

[0016] <The inventors conducted a detailed investigation into the reasons why the ammonia purification performance, particularly at low temperatures, deteriorates after hydrothermal endurance in a stacked SCR-ASC system. As a result, they found that silica in the zeolite contained in the SCR layer migrates to the ASC layer, reducing the NH3 purification activity of the catalytic noble metal in the ASC layer.

[0017] This invention is based on this finding. Specifically, the present invention is an exhaust gas purification catalyst device in which, in a stacked SCR-ASC system, an inorganic oxide particle layer is provided between the zeolite layer (SCR layer) and the catalyst noble metal particle supported layer (ASC layer) as a barrier layer to prevent silica migration, thereby maintaining low-temperature ammonia purification performance even after hydrothermal endurance.

[0018] However, the present invention is not bound by any particular theory.

[0019] The elements of the exhaust gas purification catalyst device of the present invention will be described in detail below.

[0020] As described above, the exhaust gas purification catalyst device of the present invention comprises a honeycomb substrate, a catalyst precious metal particle supporting layer, and a zeolite layer, and further comprises an inorganic oxide particle layer between the catalyst precious metal particle supporting layer and the zeolite layer.

[0021] <Base material> The substrate in the exhaust gas purification catalyst device of the present invention is a honeycomb substrate having a plurality of exhaust gas flow paths partitioned by partition walls. The partition walls of the substrate may have pores that allow fluid communication between adjacent exhaust gas flow paths.

[0022] This substrate may be appropriately selected according to the desired configuration of the exhaust gas purification catalyst. The constituent material of the substrate may be, for example, a refractory inorganic oxide such as cordierite. The substrate may be of the straight-flow type or the wall-flow type.

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

[0024] <Catalyst precious metal particle supported layer> The exhaust gas purification catalyst device of the present invention has a catalyst precious metal particle supported layer within or on the partition wall of the substrate. The catalyst precious metal particle supported layer contains particles of the catalyst precious metal. These catalyst precious metal particles function as a catalyst for oxidative purification of ammonia.

[0025] The catalyst precious metal particles in the catalyst precious metal particle support layer may be particles of a precious metal selected from platinum group metals, specifically, particles of one or more precious metals selected from Pt, Rh, and Pd, or particles of one or two precious metals selected from Pt and Pd.

[0026] The particle size (primary particle size) of the catalyst precious metal particles may be, for example, 15 nm or more, 20 nm or more, or 30 nm or more, and may be 100 nm or less, 80 nm or less, or 60 nm or less. The particle size of these catalyst precious metal particles may be the number-average particle size determined from images taken with a scanning electron microscope, transmission electron microscope, etc.

[0027] The amount of catalyst noble metal particles in the catalyst noble metal particle supporting layer may be 0.01 g / L or more, 0.02 g / L or more, 0.03 g / L or more, 0.04 g / L or more, or 0.05 g / L or more, as a metal equivalent mass per 1 L of substrate volume, and may be 2.00 g / L or less, 1.50 g / L or less, 1.00 g / L or less, 0.50 g / L or less, 0.30 g / L or less, or 0.10 g / L or less.

[0028] In the exhaust gas purification catalyst device of the present invention, the catalyst noble metal particles are They may be directly supported within the partition walls of the substrate to form a catalyst noble metal particle supporting layer, The catalyst noble metal particles may be supported on inorganic oxide particles other than silica, and these catalyst noble metal particles supported on inorganic oxide particles other than silica may be arranged on the partition wall of the substrate to form a catalyst noble metal particle supporting layer.

[0029] Here, "catalytic precious metal particles are directly supported within the partition walls of the substrate" means that the catalytic precious metal particles are supported on the pore walls of the partition walls of the substrate without the need for carrier particles. Furthermore, "catalytic precious metal particles supported on inorganic oxide particles other than silica are arranged on the partition walls of the substrate" means that at least a portion of the inorganic oxide particles other than silica on which the catalytic precious metal particles are supported are arranged on the partition walls without entering the pores of the partition walls of the substrate.

[0030] When the catalyst noble metal particles in the catalyst noble metal particle supporting layer are supported on inorganic oxide particles other than silica, these inorganic oxide particles may be oxide particles of one or more metals selected from titanium, zirconium, aluminum, and rare earth elements other than cerium.

[0031] Furthermore, if the catalyst precious metal particles in the catalyst precious metal particle support layer are supported on inorganic oxide particles containing silica, there is a concern that the NH3 purification activity of the catalyst precious metal may be impaired, which is therefore undesirable.

[0032] <Zeolite layer> The zeolite layer is a layer containing copper ion exchange zeolite and is located on the exhaust gas flow path side of the catalyst noble metal particle supported layer.

[0033] The silica-alumina ratio (SAR) of the copper ion-exchange zeolite in the zeolite layer may be 15.0 or less. Using zeolite with an SAR of 15.0 or less results in a high NOx purification rate through the SCR reaction. 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.

[0034] The SAR of copper ion exchange zeolite 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, from the perspective of increasing the NOx purification rate. On the other hand, if the SAR is too low, the synthesis of the zeolite becomes difficult, which may lead to an excessive increase in catalyst costs. To avoid such a situation, the SAR of copper ion exchange zeolite may be 4.0 or higher, 5.0 or higher, 6.0 or higher, or 7.0 or higher.

[0035] The copper ion-exchange zeolite in the zeolite layer is a zeolite that has been ion-exchanged with Cu. The amount of Cu in the copper ion-exchange zeolite may be 0.08 mol or more, 0.10 mol / mol or more, 0.15 mol / mol or more, 0.20 mol / mol or more, or 0.25 mol / mol or more per mole of Al atoms in the zeolite, from the viewpoint of increasing the SCR activity of the exhaust gas purification catalyst device of the present invention.

[0036] There are no upper limits on the amount of Cu in copper ion exchange zeolite from the standpoint of SCR activity. However, there are manufacturing limitations on the amount of Cu in copper ion exchange zeolite, and from the viewpoint of maintaining appropriate manufacturing costs for exhaust gas purification catalysts, the amount of Cu in copper ion exchange zeolite may be 0.80 mol / mol or less, 0.50 mol / mol or less, 0.45 mol / mol or less, or 0.40 mol / mol or less per mole of Al atoms in the zeolite.

[0037] The amount of Cu in the copper ion-exchange zeolite is typically between 0.10 mol and 0.50 mol per mole of Al atoms in the zeolite.

[0038] The crystal structure of the copper ion exchange zeolite in the zeolite layer is arbitrary. Examples of copper ion exchange zeolites applicable to the present invention, along with their respective structural codes (indicated in parentheses), include type A (LTA), ferrielite (FER), MCM-22 (MWW), ZSM-5 (MFI), mordenite (MOR), L-type (LTL), X-type or Y-type (FAU), beta-type (BEA), chabasite (CHA), etc.

[0039] The copper ion exchange zeolite contained in the zeolite layer of the exhaust gas purification catalyst of the present invention may be, in particular, a Cu-CHA type zeolite obtained by ion exchange of chabasite (CHA) type zeolite with Cu.

[0040] The copper ion exchange zeolite in the zeolite layer may be in particulate form. The particle size (secondary particle size) of the particulate copper ion exchange zeolite may be, for example, 0.5 μm or larger, 1 μm or larger, 3 μm or larger, or 5 μm or larger, and may be 40 μm or smaller, 20 μm or smaller, or 10 μm or smaller. The particle size of these carrier particles may be the median diameter (D50) obtained by dynamic light scattering of a suspension in which the carrier particles are dispersed in a suitable liquid medium (e.g., water).

[0041] The zeolite layer in the exhaust gas purification catalyst device of the present invention may contain any components other than copper ion exchange zeolite. These optional components may be, for example, inorganic oxides other than copper ion exchange zeolite, binders, etc. However, the zeolite layer does not need to contain any zeolite other than copper ion exchange zeolite.

[0042] The amount of copper ion exchange zeolite in the zeolite layer may be 30 g / L or more, 40 g / L or more, 50 g / L or more, 60 g / L or more, or 80 g / L or more per liter of substrate volume, from the viewpoint of increasing the SCR activity of the exhaust gas purification catalyst device of the present invention. On the other hand, in order to avoid an excessive increase in the pressure drop of the exhaust gas purification catalyst device, the amount of copper ion exchange zeolite per liter of substrate volume may be 200 g / L or less, 180 g / L or less, 150 g / L or less, 120 g / L or less, or 100 g / L or less.

[0043] The amount of copper ion-exchange zeolite in the zeolite layer may typically be between 30 g / L and 200 g / L.

[0044] The amount of zeolite layer may be 30 g / L or more, 40 g / L or more, 50 g / L or more, 60 g / L or more, or 80 g / L or more per 1 L of base material volume, and may be 180 g / L or less, 150 g / L or less, 120 g / L or less, or 100 g / L or less.

[0045] <Inorganic oxide particle layer> The exhaust gas purification catalyst device of the present invention further comprises an inorganic oxide particle layer between the catalyst precious metal particle supporting layer and the zeolite layer. This inorganic oxide particle layer contains inorganic oxide particles other than silica, and the catalyst precious metal content is 0.01 g / L or less as mass per 1 L of substrate volume. Here, the "catalyst precious metal content" of the inorganic oxide particle layer refers to the total content of Pt, Rh, and Pd contained in the inorganic oxide particle layer.

[0046] The inorganic oxide particle layer functions as a barrier layer that prevents silica migration, thereby suppressing the migration of silica from the copper ion exchange zeolite contained in the zeolite layer (SCR layer) to the catalyst precious metal particle support layer (ASC layer), which would reduce the NH3 purification activity of the catalyst precious metal in the catalyst precious metal particle support layer. Therefore, the inorganic oxide particle layer does not need to contain silica in any substantial amount. The amount of silica in the inorganic oxide particle layer, including the amount contained in the composite oxide of silicon and other inorganic elements, may be 1.0 g / L or less, 0.5 g / L or less, 0.1 g / L or less, 0.05 g / L or less, or 0.01 g / L or less as a mass per 1 L of substrate volume, or it may be 0 g / L.

[0047] The fact that the catalytic precious metal content of the inorganic oxide particle layer is 0.01 g / L or less means that the inorganic oxide particle layer does not need to substantially contain catalytic precious metals having NH3 purification activity. The catalytic precious metal content in the inorganic oxide particle layer may be 0.005 g / L or less, 0.001 g / L or less, 0.0005 g / L or less, or 0.0001 g / L or less, or it may be 0 g / L.

[0048] The inorganic oxide particles other than silica contained in the inorganic oxide particle layer may be oxide particles of one or more metals selected from Ce, Ti, Zr, Al, La, Fe, Co, Mn, V, W, Cu, and Ni. In particular, they may be one or more inorganic oxide particles selected from alumina, titania, and ceria.

[0049] The particle size of the inorganic oxide particles contained in the inorganic oxide particle layer may be 0.5 μm or larger, 0.7 μm or larger, 1.0 μm or larger, 1.2 μm or larger, 1.5 μm or larger, 2.0 μm or larger, or 2.5 μm or larger, and may be 5.0 μm or smaller, 4.5 μm or smaller, 4.0 μm or smaller, 3.5 μm or smaller, 3.0 μm or smaller, 2.5 μm or smaller, or 2.0 μm or smaller, from the viewpoint of achieving both the function of preventing silica migration and gas permeability.

[0050] The particle size of the inorganic oxide particles may typically be between 0.5 μm and 5.0 μm.

[0051] The particle size of the inorganic oxide particles contained in the inorganic oxide particle layer described above is the median diameter (D50) obtained by dynamic light scattering.

[0052] The inorganic oxide particle layer in the exhaust gas purification catalyst device of the present invention may contain arbitrary integrals such as a binder in addition to inorganic oxide particles.

[0053] The coating thickness of the inorganic oxide particle layer in the exhaust gas purification catalyst device of the present invention may be appropriately determined from the viewpoint of achieving both the function of preventing silica migration and gas permeability. The coating thickness of the inorganic oxide particle layer may be 2.0 μm or more, 3.0 μm or more, 5.0 μm or more, 10.0 μm or more, 15.0 μm or more, or 20.0 μm or more, and may be 30.0 μm or less, 25.0 μm or less, 20.0 μm or less, 15.0 μm or less, or 10.0 μm or less.

[0054] The coating thickness of the inorganic oxide particle layer may typically be between 2.0 μm and 25.0 μm.

[0055] The coating thickness of the inorganic oxide particle layer can be set to a desired thickness by adjusting, for example, the particle size of the inorganic oxide particles contained in the inorganic oxide particle layer, the amount of the inorganic oxide particle layer coating, etc.

[0056] The amount of the inorganic oxide particle layer coating may be set appropriately, taking into consideration the particle size of the inorganic oxide particles contained in the inorganic oxide particle layer, so that the inorganic oxide particle layer has an appropriate coating thickness. The amount of the inorganic oxide particle layer coating may be 3.0 g / L or more, 5.0 g / L or more, 10.0 g / L or more, 20.0 g / L or more, 30.0 g / L or more, 4.0 g / L or more, or 50.0 g / L or more, as mass per 1 L of substrate volume, and may be 100.0 g / L or less, 90.0 g / L or less, 80.0 g / L or less, 7.0 g / L or less, 60.0 g / L or less, or 50.0 g / L or less.

[0057] Method for manufacturing an exhaust gas purification catalyst device The exhaust gas purification catalyst device of the present invention is not limited in its manufacturing method, as long as it has the above-described configuration. However, the exhaust gas purification catalyst device of the present invention is, for example, Forming a layer supporting noble metal catalyst particles within or on the partition wall of the substrate. Forming an inorganic oxide particle layer on a substrate on which a noble metal catalyst particle support layer is formed, and Forming a zeolite layer on a substrate on which a noble metal catalyst particle support layer and an inorganic oxide particle layer are formed. It may be manufactured by a method for manufacturing an exhaust gas purification catalyst, which includes [the specified component].

[0058] <Base material> The substrate may be appropriately selected depending on the substrate in the desired exhaust gas purification catalyst device. For example, it may be a cordierite monolithic honeycomb substrate of the straight-flow or wall-flow type.

[0059] <Formation of a layer supporting precious metal catalyst particles> As described above, in the noble metal catalyst particle supporting layer of the exhaust gas purification catalyst device of the present invention, the noble metal catalyst particles may be directly supported within or on the partition walls of the substrate, or they may be supported on suitable carrier particles. The formation of the noble metal catalyst particle supporting layer in the cases where the noble metal catalyst particles are directly supported within or on the partition walls of the substrate, and in the case where the noble metal catalyst particles are supported on carrier particles will be described in order below.

[0060] (Formation of a noble metal catalyst particle supported layer in which noble metal catalyst particles are directly supported within or on the partition walls of a substrate) In this case, for example, a wash coat solution 1 containing a noble metal precursor and a suitable solvent may be coated onto a substrate and fired to form a noble metal catalyst particle support layer. This wash coat solution 1 may contain a thickening agent and may be adjusted to an appropriate viscosity.

[0061] The precious metal precursor may be a halide, strong acid salt, complex compound, etc., of the precious metal constituting the desired precious metal catalyst particles. If the precious metal catalyst particles are, for example, platinum particles, the precious metal precursor may be, for example, tetraammineplatinum hydroxide, tetraammineplatinum chloride, ammonium tetrachloroplatinate, ammonium hexachloroplatinate, dinitrodiammineplatinum (in nitric acid solution), etc.

[0062] The thickening agent may be, for example, a polysaccharide, a solvent-soluble polymer, and more specifically, hydroxyethylcellulose, carboxymethylcellulose, chlorine seed gum, xanthan gum, polyacrylic acid, polyether, etc.

[0063] The solvent of washcoat solution 1 may be one or more selected from water and water-soluble organic solvents, and is typically water.

[0064] The coating of the wash coat liquid 1 onto the substrate and the firing may be carried out by known methods or by methods thereon with appropriate modifications by those skilled in the art.

[0065] Here, by appropriately adjusting the viscosity of the wash coat liquid 1, the coating conditions, the time from the end of coating to firing, etc., a layer supporting noble metal catalyst particles can be formed on the partition wall of the substrate or within the partition wall at any depth.

[0066] (Formation of a noble metal catalyst particle support layer in which noble metal catalyst particles are supported on support particles) In this case, for example, a layer supporting precious metal catalyst particles may be formed by coating a substrate with a wash coat liquid 1' containing carrier particles on which precious metal catalyst particles are supported and a suitable solvent, and then firing it. This wash coat liquid 1' may contain any components of the layer supporting precious metal catalyst particles, and may also contain a thickening agent and be adjusted to an appropriate viscosity.

[0067] The carrier particles may be appropriately selected depending on the carrier particles in the desired noble metal catalyst particle support layer. Therefore, these carrier particles may be particles of inorganic oxides other than silica, and may be particles of one or more oxides selected from titanium, zirconium, aluminum, and rare earth elements other than cerium.

[0068] The loading of noble metal catalyst particles onto carrier particles may be carried out by contacting the carrier particles with the noble metal precursor and then calcining. This contact may be carried out in the presence of a suitable solvent, such as one or more selected from water and water-soluble organic solvents, typically water, or it may be carried out without a solvent. Calcination may be carried out by known methods or by methods thereon with appropriate modifications by those skilled in the art.

[0069] The optional components contained in the wash coat liquid 1' may be appropriately selected according to the desired configuration of the noble metal catalyst particle support layer. The wash coat liquid 1' may contain, for example, inorganic oxide particles other than the support particles, a binder, etc.

[0070] The thickener and solvent contained in wash coat liquid 1' may be the same as those in wash coat liquid 1 used for forming a noble metal catalyst particle supported layer in which noble metal catalyst particles are directly supported on a substrate.

[0071] The coating of the wash coat liquid 1' onto the substrate and the firing may be carried out by known methods or by methods thereon with appropriate modifications by those skilled in the art.

[0072] <Formation of inorganic oxide particle layer> The formation of an inorganic oxide particle layer on a substrate on which a precious metal catalyst particle support layer is formed may be carried out by coating the substrate on which the precious metal catalyst particle support layer is formed with a wash coat liquid 2 containing inorganic oxide particles of a predetermined particle size and a suitable solvent, and then firing it. This wash coat liquid 2 may contain a thickening agent and may be adjusted to a suitable viscosity.

[0073] The inorganic oxide particles may be appropriately selected depending on the inorganic oxide particles in the desired inorganic oxide particle layer.

[0074] The thickener and solvent contained in wash coat solution 2 may be the same as those in wash coat solution 1.

[0075] The coating of the wash coat liquid 2 onto the substrate on which the precious metal catalyst particle support layer is formed, and the subsequent firing, may be carried out by known methods or by methods thereon with appropriate modifications by those skilled in the art.

[0076] <Formation of zeolite layers> In the manufacturing method of the exhaust gas purification device of the present invention, the zeolite layer may be formed by coating a substrate having a noble metal catalyst particle support layer and an inorganic oxide particle layer with a wash coat liquid 3 containing copper ion exchange zeolite and a suitable solvent, and then firing it. This wash coat liquid 3 may contain a thickening agent and may be adjusted to a suitable viscosity. Furthermore, the wash coat liquid 3 may further contain optional components such as inorganic oxides other than copper ion exchange zeolite and binders, and the type and amount of these optional components may be appropriately selected according to the desired configuration of the zeolite layer.

[0077] The thickener and solvent contained in wash coat solution 3 may be the same as those in wash coat solution 1.

[0078] The coating of the wash coat liquid 3 onto the substrate having a noble metal catalyst particle support layer and an inorganic oxide particle layer, and the firing, may be carried out by known methods or by methods thereon with appropriate modifications by those skilled in the art.

[0079] By the above method, the exhaust gas purification catalyst device of the present invention can be obtained. [Examples]

[0080] Example 1 <Manufacturing of exhaust gas purification catalyst equipment> (1) Preparation of Wash Coat Solution 1 An aqueous solution of tetraammineplatinum(II) hydroxide as a precious metal precursor and pure water were mixed, and a polysaccharide as a thickening agent was added to obtain wash coat solution 1 containing the precious metal precursor. The Pt concentration in wash coat solution 1 was set to 0.030% by mass in terms of metallic Pt equivalent.

[0081] (2) Preparation of Wash Coat Solution 2 Alumina particles (median diameter (D50) 1.0 μm) as inorganic oxide particles and pure water were mixed, and a polysaccharide as a thickening agent was added to obtain wash coat solution 2 containing inorganic oxide particles. The inorganic oxide particle content in wash coat solution 2 was 20% by mass.

[0082] (3) Preparation of wash coat solution 3 A wash coat solution 3 containing Cu-CHA type zeolite was obtained by mixing a Cu-CHA type zeolite with a silica-alumina ratio (SAR) of 13.5 and a Cu content of 0.28 mol / mol-Al per Al atom, a silica-based binder, and pure water, and then adding a polysaccharide as a thickening agent.

[0083] (4) Formation of each coating layer (manufacturing of exhaust gas purification catalyst device) A straight-flow honeycomb substrate made of cordierite with a capacity of 17 mL was coated with the wash coat solution 1 obtained above, such that the amount of Pt in terms of metallic Pt was 0.05 g / L. Then, it was fired in air at 500°C for 15 minutes to form a noble metal catalyst particle supported layer in which Pt particles were directly supported within the partition walls of the substrate, thereby obtaining catalyst device precursor 1.

[0084] Next, the catalyst precursor 1 was coated with the wash coat liquid 2 obtained above, such that the amount of inorganic oxide particles was 50.0 g / L. Then, it was calcined in air at 500°C for 15 minutes to form an inorganic oxide particle layer on the partition wall of the substrate, thereby obtaining catalyst precursor 2.

[0085] Furthermore, the wash coat liquid 3 obtained above was coated onto the catalyst precursor 2 so that the amount of Cu-CHA type zeolite was 100 g / L. Then, it was calcined in air at 500°C for 15 minutes to form a zeolite layer containing Cu-CHA type zeolite on the inorganic oxide particle layer, thereby obtaining the exhaust gas purification catalyst device of Example 1.

[0086] The coating thickness of the inorganic oxide particle layer in the exhaust gas purification catalyst device of Example 1 was found to be 12.4 μm when examined using a scanning electron microscope.

[0087] Furthermore, Figure 1 shows a scanning electron microscope image of the exhaust gas purification catalyst device of Example 1.

[0088] (5) Evaluation of exhaust gas purification catalysts The NH3 purification performance of the obtained exhaust gas purification catalyst was investigated before and after hydrothermal endurance testing. Hydrothermal endurance testing was performed by heating the exhaust gas purification catalyst at 700°C for 50 hours while circulating air with a moisture concentration of 10% by volume.

[0089] The NH3 purification performance was evaluated by introducing a model gas containing NH3 of known concentration, set to a predetermined temperature, into the exhaust gas purification catalyst before and after hydrothermal endurance testing, circulating it, measuring the NH3 in the exhaust gas, and determining the NH3 purification rate using the following formula. NH3 purification rate (%) = {(NH3 concentration in intake gas - NH3 concentration in exhaust gas) / NH3 concentration in intake gas} × 100

[0090] The introduction conditions for the model gas were set as follows: Model gas composition: NH3: 500 ppm, O2: 10%, H2O: 5%, and N2 balance Space velocity when introducing model gas: 60,000hr -1

[0091] Table 2 shows the NH3 purification rate at an inlet gas temperature of 300°C as an evaluation result before hydrothermal endurance testing, and the NH3 purification rates at inlet gas temperatures of 300°C, 350°C, and 400°C as an evaluation result after hydrothermal endurance testing.

[0092] Examples 2-8 Except for changing the type and particle size of inorganic oxide particles contained in wash coat liquid 2, and the amount and thickness of the inorganic oxide layer, as shown in Table 1, an exhaust gas purification catalyst device was manufactured and evaluated in the same manner as in Example 1. The evaluation results are shown in Table 2.

[0093] Comparative Example 1 Except for not forming an inorganic oxide particle layer with washcoat liquid 2, an exhaust gas purification catalyst device was manufactured and evaluated in the same manner as in Example 1. The evaluation results are shown in Table 2.

[0094] Furthermore, Figure 2 shows a scanning electron microscope image of the exhaust gas purification catalyst device of Comparative Example 1.

[0095] [Table 1]

[0096] [Table 2]

[0097] The abbreviations for each component in the table have the following meanings: <Precious metal precursors> Pt ammine:tetraammineplatinum(II) hydroxide aqueous solution <Zeolite> Cu-CHA: A Cu-CHA type zeolite with a silica-alumina ratio (SAR) of 13.5 and a Cu content of 0.28 mol / mol-Al per Al atom.

[0098] As can be seen from Tables 1 and 2, the exhaust gas purification catalysts of Examples 1 to 8, which have an inorganic oxide particle layer between the noble metal particle support layer and the zeolite layer, showed superior NH3 purification performance after hydrothermal endurance compared to the exhaust gas purification catalyst of Comparative Example 1, which does not have an inorganic oxide particle layer.

[0099] In particular, the exhaust gas purification catalyst devices of Examples 1 to 6, which met the requirement that the coating thickness of the inorganic oxide particle layer be between 2.0 μm and 25.0 μm, exhibited extremely high NH3 purification performance after hydrothermal endurance testing.

Claims

1. A honeycomb substrate having multiple exhaust gas passages partitioned by partition walls, The catalyst noble metal particle supporting layer within or on the partition wall of the substrate, and A zeolite layer containing copper ion exchange zeolite, located on the exhaust gas flow path side of the catalyst noble metal particle supporting layer. An exhaust gas purification catalyst device having, The catalyst noble metal particle supporting layer contains catalyst noble metal particles, The catalyst precious metal particle supporting layer and the zeolite layer further contain an inorganic oxide particle layer containing inorganic oxide particles other than silica, wherein the amount of silica is 1.0 g / L or less and the amount of catalyst precious metal is less than 0.01 g / L. The amount of Cu in the copper ion exchange zeolite contained in the zeolite layer is 0.25 mol or more and 0.50 mol or less per mole of Al atoms in the zeolite, and The coating thickness of the inorganic oxide particle layer is 10.0 μm or more and 25.0 μm or less. Exhaust gas purification catalyst device.

2. The exhaust gas purification catalyst apparatus according to claim 1, wherein the coating thickness of the inorganic oxide particle layer is 10.0 μm or more and 20.0 μm or less.

3. The exhaust gas purification catalyst apparatus according to claim 1 or 2, wherein the inorganic oxide particles contained in the inorganic oxide particle layer are particles of oxides of one or more metals selected from Ce, Ti, Zr, Al, La, Fe, Co, Mn, V, W, Cu, and Ni.

4. The exhaust gas purification catalyst apparatus according to any one of claims 1 to 3, wherein the particle size (D50) of the inorganic oxide particles contained in the inorganic oxide particle layer is 0.5 μm or more and 5.0 μm or less.

5. The exhaust gas purification catalyst device according to any one of claims 1 to 4, wherein the silica-alumina ratio (SAR) of the copper ion exchange zeolite contained in the zeolite layer is 15.0 or less.

6. The exhaust gas purification catalyst apparatus according to any one of claims 1 to 5, wherein the amount of Cu in the copper ion exchange zeolite contained in the zeolite layer is 0.25 mol or more and 0.40 mol or less per mole of Al atoms in the zeolite.

7. The exhaust gas purification catalyst device according to any one of claims 1 to 6, wherein the amount of copper ion exchange zeolite in the zeolite layer is 30 g / L or more and 200 g / L or less.

8. The exhaust gas purification catalyst device according to any one of claims 1 to 7, wherein the copper ion exchange zeolite is a Cu-CHA type zeolite.

9. The exhaust gas purification catalyst apparatus according to any one of claims 1 to 8, wherein the catalyst precious metal particle supporting layer comprises particles of a catalyst precious metal selected from Pt, Rh, and Pd.

10. The exhaust gas purification catalyst apparatus according to any one of claims 1 to 9, wherein the catalyst noble metal particles are directly supported within the partition walls of the substrate to form a noble metal catalyst particle supporting layer.

11. The exhaust gas purification catalyst apparatus according to any one of claims 1 to 9, wherein the catalyst noble metal particles are supported on inorganic oxide particles other than silica, and the catalyst noble metal particles supported on the inorganic oxide particles other than silica are arranged on a partition wall of a substrate to form a noble metal catalyst particle supported layer.

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