Catalyst for exhaust gas purification and method for manufacturing the same

Abstract

To provide a catalyst for exhaust gas purification which is excellent in gas diffusion property of the whole catalyst layer, and has both a high PM collection ratio and a low pressure loss, and a method for producing the same.SOLUTION: A catalyst 100 for exhaust gas purification includes at least a base material 11, and a catalyst layer 21 provided on the base material 11, wherein the catalyst layer 21 contains two or more metal oxide particles, the metal oxide particles contain at least first metal oxide particles carrying first catalyst metal and second metal oxide particles carrying the second catalyst metal, the first metal oxide particles are alumina particles, the second metal oxide particles are non-alumina particles, and in total particle size distribution of all the particles contained in the catalyst layer, cumulative frequency having a modal particle diameter of 40 μm or less and a particle diameter of 5 μm or more is 65% or more.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an exhaust gas purification catalyst and a method for producing the same, and more particularly to an exhaust gas purification catalyst using a catalyst layer having a predetermined particle size distribution and a method for producing the same. [Background technology]

[0002] Exhaust gases emitted from internal combustion engines contain particulate matter (PM), which is mainly composed of carbon, and ash, which consists of non-combustible components, and are known to cause air pollution. Traditionally, diesel engines, which tend to emit more particulate matter than gasoline engines, have been subject to stricter regulations on particulate matter emissions. However, in recent years, regulations on particulate matter emissions from gasoline engines have also been strengthened.

[0003] One known method for reducing particulate matter emissions is to install a particulate filter (PF) in the exhaust gas flow path of an internal combustion engine, which is designed to deposit and collect particulate matter. In particular, in recent years, from the perspective of saving installation space, there has been consideration of coating the particulate filter with a catalyst slurry and firing it to create a catalyst layer, in order to simultaneously suppress particulate matter emissions and remove harmful components such as carbon monoxide (CO), hydrocarbons (HC), and nitrogen oxides (NOx).

[0004] For example, Patent Document 1 discloses a method for forming a first catalyst layer and a second catalyst layer having a predetermined overlap in the stretching direction of the partition wall and a predetermined thickness in the thickness direction of the partition wall, by adjusting the properties of the catalyst slurry to be coated, such as viscosity and solid content, and by pressurizing one of the inlet-side cell or the outlet-side cell to create a pressure difference between the inlet-side cell and the outlet-side cell, thereby adjusting the penetration of the catalyst slurry into the partition wall.

[0005] Patent Document 2 discloses a method for forming a catalyst coating layer with excellent gas diffusion properties, in which 0.5 to 50% of the total volume of voids are high aspect ratio pores having an aspect ratio of 5 or more, using fibrous organic materials such as PET fibers as a pore-forming material. This method involves using a catalyst slurry containing catalytically active noble metal particles, metal oxide particles, and fibrous organic materials having an average fiber diameter in the range of 1.7 to 8.0 μm and an average aspect ratio in the range of 9 to 40 to form a catalyst coating layer in the upstream region in the exhaust gas flow direction, occupying a range from the upstream end of the substrate to 40 to 60% of the total length of the substrate.

[0006] Patent Document 3 discloses a method for forming a catalyst layer with improved exhaust gas diffusion properties, which involves forming a catalyst layer on a substrate using a catalyst slurry in which the particle size of the supported material is adjusted so that the most frequent particle size is 6 μm and the cumulative frequency in the range of most frequent particle size + 2 μm is 40% or more.

[0007] Patent Document 4 discloses an exhaust gas purification catalyst having a catalyst coating layer provided on a substrate, wherein the catalyst coating layer has a total secondary particle diameter D50 of 2 to 12 μm, and includes first metal oxide particles supported with a catalyst metal and second metal oxide particles not supported with a catalyst metal, wherein the second metal oxide particles have a secondary particle diameter D50 of 3 μm or less, and their content ratio to the total material particles of the catalyst coating layer is in the range of 5 to 55% by weight, and furthermore, the secondary particle diameter of the first metal oxide particles is larger than that of the second metal oxide particles. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] International Publication No. 2016 / 060048 [Patent Document 2] Japanese Patent Publication No. 2016-182586 [Patent Document 3] Japanese Patent Application Laid-Open No. 2021-53604 [Patent Document 4] Japanese Patent Application Laid-Open No. 2017-189735 [Summary of the Invention] [Problems to be Solved by the Invention]

[0009] Conventionally, when preparing a catalyst slurry by adding various particles to a solvent for noble metal-supported particles used in the catalyst layer of an exhaust gas purification catalyst, wet milling treatment has been performed using a bead mill, a ball mill, etc. for particle size adjustment. Since the milling treatment can crush aggregated secondary particles or primary particles, and reduce the average particle diameter of the whole particles, it has been considered that the surface area of the whole catalyst layer is improved or the particles are uniformly dispersed, thereby improving the catalytic efficiency and the supported amount of the catalytic metal.

[0010] However, according to the study by the present inventors, when performing the above-described milling treatment, fine particles are inevitably by-produced. As a result of these fine particles being arranged between coarse particles, it has been found that the pore (void) size is narrowed or the communication between pores is inhibited, which in turn causes the occlusion of pores or macropores. When these events occur frequently, the uniform diffusion of exhaust gas in the catalyst layer is inhibited, causing a decrease in the purification rate per supported catalyst amount, and also causing an excessive increase in pressure loss or an excessive decrease in collection performance, etc.

[0011] Therefore, the present invention has been made in view of the above circumstances, and its object is to provide an exhaust gas purification catalyst having excellent gas diffusibility throughout the catalyst layer, having a high PM collection rate and a low pressure loss, and a method for manufacturing the same, etc. [Means for Solving the Problems]

[0012] In order to solve the above problems, the present inventors have conducted intensive studies focusing on the particle size distribution of metal oxide particles. As a result, they have found that, unexpectedly, there are an excessive number of fine particles in the prior art, and by adopting a specific particle size distribution that corrects this, a catalyst layer excellent in gas diffusibility and having a high PM collection rate and a low pressure loss can be realized, leading to the completion of the present invention. That is, the present invention provides various specific embodiments shown below.

[0013] (1) An exhaust gas purification catalyst comprising at least a substrate and a catalyst layer provided on the substrate, wherein the catalyst layer contains two or more metal oxide particles, the metal oxide particles include at least first metal oxide particles supporting a first catalyst metal and second metal oxide particles supporting a second catalyst metal, the first metal oxide particles are alumina particles, the second metal oxide particles are non-alumina particles, and the total particle size distribution of all particles contained in the catalyst layer satisfies that the most frequent particle diameter is 40.0 μm or less and the cumulative frequency of particle diameters of 5.0 μm or more is 65.0% or more.

[0014] (2) The exhaust gas purification catalyst according to (1), wherein the first metal oxide particles have a particle size distribution with the most frequent particle diameter of 5.0 μm or more and 40.0 μm or less.

[0015] It is (3) The exhaust gas purification catalyst according to (1) or (2), wherein the second metal oxide particles have a particle size distribution with the most frequent particle diameter of 5.0 μm or more and 40.0 μm or less and the cumulative particle diameter distribution of the most frequent particle diameter ± 5.0 μm being 1 / 3 or more of the whole.

[0016] (4) The exhaust gas purification catalyst according to any one of (1) to (3), wherein the second metal oxide particles contain one or more selected from the group consisting of ceria and zirconia.

[0017] (5) The exhaust gas purification catalyst according to any one of (1) to (4), wherein based on a total of 100 parts by mass of the first metal oxide particles and the second metal oxide particles, 20 to 80 parts by mass of the first metal oxide particles and 80 to 20 parts by mass of the second metal oxide particles are contained.

[0018] (6) The exhaust gas purification catalyst according to any one of (1) to (5), wherein the first catalytic metal comprises one or more selected from the group consisting of platinum, palladium, rhodium, and ruthenium.

[0019] (7) The exhaust gas purification catalyst according to any one of (1) to (6), wherein the second catalytic metal comprises one or more selected from the group consisting of platinum, palladium, rhodium, and ruthenium.

[0020] (8) A method for producing an exhaust gas purification catalyst, comprising the steps of: preparing a catalyst slurry containing two or more metal oxide particles, wherein the metal oxide particles include at least first metal oxide particles supporting a first catalyst metal and second metal oxide particles supporting a second catalyst metal, the first metal oxide particles being alumina particles and the second metal oxide particles being non-alumina particles, and the total particle size distribution of all particles contained in the catalyst slurry satisfying that the most frequent particle size is 40 μm or less and the cumulative frequency of particles with a particle size of 5 μm or more is 65% or more; and applying the catalyst slurry onto a substrate to form a catalyst layer.

[0021] (9) The method for producing an exhaust gas purification catalyst according to (8), wherein the catalyst slurry having the total particle size distribution is prepared without performing wet milling on the first metal oxide particles and the second metal oxide particles. [Effects of the Invention]

[0022] According to the present invention, it is possible to realize an exhaust gas purification catalyst and a method for producing the same that exhibits excellent gas diffusion throughout the catalyst layer, high PM collection efficiency, and low pressure loss. Furthermore, according to the present invention, because of the excellent gas diffusion throughout the catalyst layer, it is possible to remove harmful components such as carbon monoxide (CO), hydrocarbons (HC), and nitrogen oxides (NOx) at lower temperatures compared to catalysts using the same amount of catalyst, and to realize an exhaust gas purification catalyst with enhanced catalytic activity. [Brief explanation of the drawing]

[0023] [Figure 1] This is a schematic cross-sectional view showing the general configuration of the exhaust gas purification catalyst 100 of this embodiment. [Modes for carrying out the invention]

[0024] The embodiments of the present invention will be described in detail below. The following embodiments are examples (representative examples) of embodiments of the present invention, and the present invention is not limited thereto. Furthermore, the present invention can be modified and implemented as appropriate without departing from its spirit. In this specification, positional relationships such as up, down, left, and right shall be based on the positional relationships shown in the drawings unless otherwise specified. Furthermore, the dimensional ratios in the drawings are not limited to the ratios shown. Furthermore, in this specification, when a numerical value or physical property value is enclosed before and after using "~", it is used to include the values ​​before and after it. For example, the notation of a numerical range "1~100" shall include both the lower limit value "1" and the upper limit value "100". The same applies to other numerical range notations.

[0025] [Exhaust gas purification catalyst] Figure 1 is a schematic cross-sectional view showing the general configuration of the exhaust gas purification catalyst 100 of this embodiment. The exhaust gas purification catalyst 100 of this embodiment is placed in the exhaust gas passage of an internal combustion engine, such as a gasoline engine, and functions as a catalytic coated particulate filter that purifies exhaust gases such as carbon monoxide (CO), hydrocarbons (HC), and nitrogen oxides (NOx) emitted from the gasoline engine, and traps particulate matter (PM) mainly composed of carbon and ash consisting of combustion components. This exhaust gas purification catalyst 100 comprises at least a substrate 11 and a catalyst layer 21 provided on the substrate 11. Each component will be described in detail below.

[0026] As the base material 11, for example, a honeycomb structure widely used in automotive exhaust gas applications is preferably used. Examples of such honeycomb structures include ceramic monolith carriers such as cordierite, silicon carbide, and silicon nitride, metal honeycomb carriers such as those made of stainless steel, wire mesh carriers such as those made of stainless steel, and knit wire carriers in the form of steel wool. Also, the shape thereof is not particularly limited, and for example, any shape such as a prismatic shape, a cylindrical shape, a spherical shape, a honeycomb shape, or a sheet shape can be selected. These can be used alone or in appropriate combination of two or more. Note that as a honeycomb structure for automotive exhaust gas applications, a through-flow type structure in which gas flow paths are connected and a wall-flow type structure in which a part of the end face of the gas flow path is sealed and gas can flow through the wall surface of the gas flow path are widely known, but from the viewpoint of collecting particulate matter and the like, the wall-flow type structure is preferably used.

[0027] As shown in FIG. 1, the wall-flow type base material 11 is a structure (catalyst carrier) in which a plurality of introduction-side cells S IN and discharge-side cells S EM are arranged in parallel. Specifically, the wall-flow type base material 11 includes an introduction-side cell S in which only the end portion 11a on the exhaust gas introduction side is open IN and a discharge-side cell S adjacent to this introduction-side cell S IN in which only the end portion 11b on the exhaust gas discharge side is open, and a partition wall 12 made of a porous body and having pores through which exhaust gas permeates, the partition wall 12 defining the introduction-side cell S EM and the discharge-side cell S IN and the discharge-side cell S EM In this wall-flow type base material 11, the openings at one end portion 11a and the other end portion 11b in the extending direction (cell extending direction) of the partition wall 12 are alternately sealed by a sealing wall 13, whereby the introduction-side cells S adjacent to each other through the partition wall 12 IN and the discharge-side cells S EM are alternately partitioned and formed.

[0028] The introduction-side cell S IN and the discharge-side cell S EMThese are arranged in a regular, parallel, and alternating manner along the axial direction of the columnar shape, and as described above, adjacent cells are alternately sealed at one end 11a and the other end 11b in the extension direction. These introduction-side cells S IN and discharge cell S EM The shape and size can be set to an appropriate size considering the flow rate and composition of the supplied exhaust gas. For example, the introduction cell S IN and discharge cell S EM The opening shape can be a triangle; a rectangle such as a square, parallelogram, rectangle, and trapezoid; other polygons such as a hexagon and an octagon; or a circle. Also, the introduction side cell S IN The cross-sectional area and the discharge side cell S EM It may also have a High Ash Capacity (HAC) structure with a different cross-sectional area. Note that the introduction cell S IN and discharge cell S EM The density can be set appropriately to promote the generation of turbulence in the exhaust gas and suppress clogging by particulate matter contained in the exhaust gas, and is not particularly limited, but is usually preferably 200 cpsi to 400 cpsi. Similarly, the thickness of the partition wall 12 can be set appropriately, for example, 8 mil to 12 mil is preferred.

[0029] The partition walls 12 separating adjacent cells are not particularly limited as long as they have a porous structure through which exhaust gas can pass, and their configuration can be appropriately adjusted from the viewpoint of exhaust gas purification performance, suppression of pressure loss increase, and improvement of the mechanical strength of the substrate. For example, when the pore diameter (e.g., mode diameter (the pore diameter with the largest proportion of appearance in the frequency distribution of pore diameters (maximum value of the distribution))) or pore volume of the pores is small, the pressure loss tends to increase, but the ability to collect particulate matter improves, and the mechanical strength of the wall-flow type substrate 11 tends to improve. On the other hand, when the pore diameter of the pores is large, the opposite trend occurs. From this viewpoint, the pore volume of the partition walls 12 of the wall-flow type substrate 11 is preferably 0.2 to 1.5 cm³ by the mercury intrusion method. 3 / g, more preferably 0.25~0.9cm 3The density is / g, and more preferably 0.3 to 0.8 cm. 3 The value is / g. Furthermore, the porosity of the partition wall 12 is preferably 20-80%, more preferably 40-70%, and even more preferably 60-70%. When the pore volume or porosity is above the lower limit, the increase in pressure loss tends to be further suppressed. Also, when the pore volume or porosity is below the upper limit, the strength of the wall-flow type substrate 11 tends to be further improved.

[0030] As the base material 11 consisting of such a structure, various materials and shapes conventionally used for this type of application can be used. For example, the material of the base material 11 is preferably made of a heat-resistant material so that it can withstand exposure to high-temperature exhaust gas (e.g., 400°C or higher) generated when an internal combustion engine is operated under high-load conditions, or when particulate matter is burned and removed at high temperatures. Examples of heat-resistant materials include ceramics such as cordierite, silicon carbide, silicon nitride, mullite, aluminum titanate, and silicon carbide (SiC); and alloys such as stainless steel. Furthermore, the shape of the base material 11 can be appropriately adjusted from the viewpoint of exhaust gas purification performance and suppression of pressure loss increase. For example, the outer shape of the base material 11 can be cylindrical, elliptical, or polygonal. Also, although it varies depending on the space in which it will be incorporated, the capacity of the base material 11 (total volume of cells) is usually preferably 0.1 to 5 L, and more preferably 0.5 to 3 L. Furthermore, the total length of the base material 11 in the stretching direction (the total length of the partition wall 12 in the stretching direction) also varies depending on the space where it is to be incorporated, but is usually preferably 10 to 500 mm, and more preferably 50 to 300 mm. In this embodiment, the introduction side cell S IN The exhaust gas introduced from the end 11a side is directed to the introduction cell S IN , partition wall 12 and discharge side cell S EM It passes through in this order, and discharge cell S EM The exhaust gas is discharged from the end 11b side to the outside of the system. The black arrows in Figure 1 indicate the direction of exhaust gas introduction and discharge.

[0031] In this embodiment, a catalyst layer 21 is provided on the outer wall surface 12a of the partition wall 12 of the wall-flow type substrate 11 by a wash-coat method, extending from the exhaust gas inlet end 11a along the direction of extension of the partition wall 12. In the exhaust gas purification catalyst 100 of this embodiment, exhaust gas discharged from the gasoline engine enters the introduction cell S from the exhaust gas introduction end 11a (opening). IN It flows inward, passes through the pores of the partition wall 12, and enters the adjacent discharge cell S EM The exhaust gas flows inward, flows out from the exhaust gas discharge end 12a (opening), and is discharged outside the system. In this process, the exhaust gas comes into contact with the catalyst layer 21, where carbon monoxide (CO) and hydrocarbons (HC) contained in the exhaust gas are oxidized to water (H2O) and carbon dioxide (CO2), and nitrogen oxides (NOx) are reduced to nitrogen (N2), thus purifying (detoxifying) harmful components. In addition, particulate matter (PM) contained in the exhaust gas is generally removed from the inlet cell S IN The particulate matter is collected and separated (removed) on the outer wall surface 12a of the inner partition wall 12 and / or within the pores of the partition wall 12. The collected and accumulated particulate matter is removed, if necessary, by the catalytic function of the catalyst layer 21 or by combustion at a predetermined temperature (for example, around 500-700°C).

[0032] The catalyst layer 21 includes two or more composite particles having a base material particle and a catalytic metal as a catalytic active species supported on the base material particle. Specifically, the catalyst layer 21 includes at least a first metal oxide particle (first composite particle) on which a first catalytic metal is supported and a second metal oxide particle (second composite particle) on which a second catalytic metal is supported. These composite particles have a composite structure in which catalytic active species on the order of several nanometers to several hundred nanometers are highly dispersed and supported on the surface of the base material particle. The presence of catalytic active species on the base material particle can be determined by various measurement methods, such as observation with a transmission electron microscope (TEM), powder X-ray diffraction (XRD), electron probe microanalyzer (EPMA), and X-ray photoelectron spectroscopy (XPS, or ESCA). By supporting the first and second catalytic metals in a highly dispersed manner on the surface of the base material particles in this way, high exhaust gas purification performance can be obtained.

[0033] Alumina particles are used as the first metal oxide particles (matrix particles) of the first composite particles. Examples of constituent materials for alumina particles include α-alumina (α-Al2O3), δ-alumina (δ-Al2O3), γ-alumina (γ-Al2O3), δ-alumina (δ-Al2O3), η-alumina (η-Al2O3), θ-alumina (θ-Al2O3), and composite oxides containing alumina such as silica-alumina, silica-alumina-zirconia, and silica-alumina-ceria, but are not particularly limited to these. The alumina particles may also be composite oxides or solid solutions to which rare earth elements such as lanthanum and yttrium, transition metal elements, or alkaline earth metal elements are added as needed. Among these, γ-alumina is preferred, and γ-alumina to which base earth elements such as lanthanum, zirconia, and ceria are added is more preferred because it has excellent heat resistance and exhibits high catalytic activity. These alumina particles can be used individually or in any combination and ratio of two or more types.

[0034] On the other hand, as the second metal oxide particles (matrix particles) of the second composite particle, non-alumina particles other than the alumina particles, which are the first metal oxide particles mentioned above, are used. As the constituent material of the non-alumina particles, oxygen storage and release materials (OSC materials) are preferred. Oxygen storage and release materials have oxygen storage capacity, absorbing oxygen from the exhaust gas when the air-fuel ratio of the exhaust gas is lean (i.e., an oxygen-rich atmosphere) and releasing the absorbed oxygen when the air-fuel ratio of the exhaust gas is rich (i.e., a fuel-rich atmosphere). Examples include cerium oxide (ceria) and ceria-zirconia composite oxides (ceria-zirconia, etc.). The oxygen storage and release material may also be a composite oxide or solid solution to which rare earth elements such as lanthanum and yttrium, transition metal elements, or alkaline earth metal elements are added, as needed. These non-alumina particles can be used individually or in any combination and ratio of two or more types.

[0035] The proportion of first metal oxide particles used can be appropriately set according to the desired performance and is not particularly limited, but preferably the first metal oxide particles are 20 to 80 parts by mass, more preferably 25 to 75 parts by mass, and even more preferably 30 to 70 parts by mass, based on a total of 100 parts by mass of first and second metal oxide particles.

[0036] On the other hand, the proportion of second metal oxide particles used can be appropriately set according to the desired performance and is not particularly limited, but based on a total of 100 parts by mass of first and second metal oxide particles, it is preferable that the first metal oxide particles make up 80 to 20 parts by mass, more preferably 75 to 25 parts by mass, and even more preferably 70 to 30 parts by mass.

[0037] Platinum group elements (PGMs) are preferably used as the first and second catalytic metals supported on the base material particles (first metal oxide particles and second metal oxide particles). Specifically, examples include platinum (Pt), palladium (Pd), rhodium (Rh), iridium (Ir), ruthenium (Ru), osmium (Os), etc., among which platinum (Pt), palladium (Pd), rhodium (Rh), and ruthenium (Ru) are preferred. These can be used individually or in any combination and ratio of two or more elements. The first and second catalytic metals may be of the same type or different types.

[0038] The content ratio of the first catalytic metal and the second catalytic metal contained in the catalyst layer 21 can be appropriately set according to the desired performance and is not particularly limited, but from the viewpoint of keeping the amount of relatively expensive platinum group elements used relatively low and obtaining high catalytic performance, the total content ratio of platinum group elements (mass of platinum group elements per 1L of wall-flow type substrate 11) is usually preferably 0.1 to 10.0 g / L, more preferably 0.2 to 5.0 g / L, and even more preferably 0.3 to 3.0 g / L. In this specification, "per 1L of wall-flow type substrate 11" means not only the net volume of the wall-flow type substrate 11 but also the introduction-side cell S formed inside the wall-flow type substrate 11. IN Discharge side cell SEM This means "per 1 liter of total bulk volume," including the volume of pores P (voids) within the partition wall 12.

[0039] The catalyst layer 21 may contain other matrix particles in addition to the first and second metal oxide particles described above. Examples of other matrix particles include, but are not limited to, metal oxides or metal composite oxides such as silica, lanthanum oxide, neodymium oxide, and praseodymium oxide; perovskite-type oxides; barium compounds, anatase-type titania, and zeolites. Among these, anatase-type titania and zeolites are preferred. Examples of zeolites include, but are not limited to, at least one selected from the group consisting of β-type zeolite, γ-type zeolite, and ZSM-5 type zeolite. These other matrix particles can be used individually or in any combination and ratio of two or more types.

[0040] Furthermore, the catalyst layer 21 may contain various binders known in the industry in addition to the essential components mentioned above. The type of binder is not particularly limited, but examples include various sols such as boehmite, alumina sol, titania sol, and silica sol. Soluble salts such as aluminum nitrate, aluminum acetate, titanium nitrate, titanium acetate, zirconium nitrate, and zirconium acetate can also be used as binders. Acids such as acetic acid, nitric acid, hydrochloric acid, and sulfuric acid can also be used as binders. The amount of binder used is not particularly limited, but a total of 0.01 to 15% by mass of each binder is preferred, a total of 0.05 to 10% by mass of each binder is more preferred, and a total of 0.1 to 8% by mass of each binder is even more preferred, relative to the total amount of the catalyst layer 21.

[0041] Furthermore, the catalyst layer 21 may contain, in addition to the components described above, other catalyst materials, co-catalysts, and various additives known in the industry. Examples include, but are not limited to, Ba-containing compounds; dispersion stabilizers such as nonionic surfactants and anionic surfactants; pH adjusters; viscosity adjusters; alkali metals; alkaline earth metals; etc.

[0042] The total coating amount of the catalyst layer 21 can be set appropriately according to the desired performance and is not particularly limited, but from the viewpoint of balancing catalyst performance, collection performance and pressure loss, it is preferably 1 to 500 g / L per liter of wall-flow type substrate 11, more preferably 5 to 400 g / L, and even more preferably 10 to 300 g / L.

[0043] In this embodiment, the exhaust gas purification catalyst 100 is configured such that the total particle size distribution of all particles contained in the catalyst layer 21 satisfies the conditions that the most frequent particle size is 40.0 μm or less and the cumulative frequency of particles with a particle size of 5.0 μm or more is 65.0% or more. By employing a catalyst layer 21 that satisfies such a total particle size distribution, it is possible to realize an exhaust gas purification catalyst 100 that has excellent gas diffusion properties throughout the catalyst layer, and combines a high PM collection rate with low pressure loss. In this specification, the total particles contained in the catalyst layer 21 include not only the first metal oxide particles and the second metal oxide particles described above, but also particles contained in the catalyst layer 21 as optional components (for example, other base material particles, binders, other catalyst materials, co-catalysts, various additives, etc.).

[0044] Conventionally, when manufacturing exhaust gas purification catalysts, a slurry containing base material particles such as alumina particles was prepared, and then the catalyst slurry was wet-milled using a bead mill or ball mill to mill the particles and adjust them to the target particle size. However, it has become clear that while wet milling makes it easy to adjust the most frequent particle size and average particle size D50, it causes problems such as an unexpected increase in the proportion of fine particles, for example, 5 μm or smaller. It has also become clear that such fine particles clog the pores of the honeycomb support and the macropores formed during the wash coat, leading to a decrease in gas diffusivity and an increase in pressure loss. In contrast, in the exhaust gas purification catalyst 100 of this embodiment, the proportion of fine particles is reduced and the proportion of coarse particles is increased, thereby suppressing the clogging of pores or macropores, and as a result, a catalyst layer with excellent gas diffusivity and low pressure loss is realized.

[0045] The most frequent particle size of all particles contained in the catalyst layer 21 can be appropriately set according to the desired performance and is not particularly limited, but is preferably 38.0 μm or less, more preferably 36.0 μm or less, even more preferably 34.0 μm or less, and especially preferably 32.0 μm or less. The lower limit of the most frequent particle size can also be appropriately set according to the desired performance and is not particularly limited, but is preferably 6.0 μm or more, more preferably 8.0 μm or more, even more preferably 10.0 μm or more, and especially preferably 12.0 μm or more.

[0046] Furthermore, the cumulative frequency of particles with a particle size of 5.0 μm or larger in the catalyst layer 21 can be appropriately set according to the desired performance and is not particularly limited, but is preferably 67.0% or more, more preferably 69.0% or more, even more preferably 71.0% or more, and especially preferably 73.0% or more. The upper limit of the cumulative frequency can be appropriately set according to the desired performance and is not particularly limited, but is preferably 100% or less, more preferably 99.0% or less, even more preferably 98.0% or less, and especially preferably 97.0% or less.

[0047] Furthermore, the cumulative frequency of particles with a particle size of 10.0 μm or larger in the catalyst layer 21 can be appropriately set according to the desired performance and is not particularly limited, but is preferably 40.0% or more, more preferably 45.0% or more, even more preferably 50.0% or more, and especially preferably 55.0% or more. The upper limit of the cumulative frequency can be appropriately set according to the desired performance and is not particularly limited, but is preferably 100% or less, more preferably 95.0% or less, even more preferably 90.0% or less, and especially preferably 85.0% or less.

[0048] The cumulative frequency of particles within ±5.0 μm of the most frequent particle size of all particles contained in the catalyst layer 21 can be appropriately set according to the desired performance and is not particularly limited, but is preferably 6.0% or more, more preferably 9.0% or more, even more preferably 12.0% or more, and especially preferably 15.0% or more. The upper limit of the cumulative frequency can be appropriately set according to the desired performance and is not particularly limited, but is preferably 32.0% or less, more preferably 33.0% or less, even more preferably 34.0% or less, and especially preferably 35.0% or less.

[0049] In this specification, the most frequent particle size and cumulative frequency refer to values ​​measured using a laser diffraction particle size distribution analyzer (for example, the Shimadzu Corporation SALD-3100 laser diffraction particle size distribution analyzer).

[0050] The catalyst layer 21 having the above-described total particle size distribution can also be understood as having a relatively small proportion of fine particles, a relatively large particle size, and a relatively monodisperse particle size distribution. That is, the total particle size distribution of the catalyst layer 21 can also be defined by the average particle sizes D10, D50, and D90 of all particles contained in the catalyst layer 21. Here, "average particle size D10" represents the particle size when the cumulative value from small particle sizes reaches 10% of the total volume in the cumulative distribution of particle size based on volume, "average particle size D50" represents the particle size when the cumulative value from small particle sizes reaches 50% of the total volume in the cumulative distribution of particle size based on volume, and represents the so-called median diameter, and "average particle size D90" represents the particle size when the cumulative value from small particle sizes reaches 90% of the total volume in the cumulative distribution of particle size based on volume. In this specification, the average particle diameters D10, D50, and D90 also refer to values ​​measured using a laser diffraction particle size distribution analyzer (for example, the SALD-3100 laser diffraction particle size distribution analyzer manufactured by Shimadzu Corporation).

[0051] The average particle size D10 of all particles contained in the catalyst layer 21 can be appropriately set according to the desired performance and is not particularly limited, but is preferably 0.6 μm or more, more preferably 0.8 μm or more, even more preferably 1.0 μm or more, and especially preferably 1.2 μm or more. Furthermore, the upper limit of the average particle size D10 can be appropriately set according to the desired performance and is not particularly limited, but is preferably 12.0 μm or less, more preferably 10.0 μm or less, even more preferably 8.0 μm or less, and especially preferably 6.0 μm or less.

[0052] The average particle size D50 of all particles contained in the catalyst layer 21 can be appropriately set according to the desired performance and is not particularly limited, but is preferably 3.0 μm or more, more preferably 4.0 μm or more, even more preferably 5.0 μm or more, and especially preferably 6.0 μm or more. Furthermore, the upper limit of the average particle size D50 can be appropriately set according to the desired performance and is not particularly limited, but is preferably 40.0 μm or less, more preferably 35.0 μm or less, even more preferably 30.0 μm or less, and especially preferably 25.0 μm or less.

[0053] The average particle size D90 of all particles contained in the catalyst layer 21 can be appropriately set according to the desired performance and is not particularly limited, but is preferably 10.0 μm or more, more preferably 12.0 μm or more, even more preferably 14.0 μm or more, and especially preferably 16.0 μm or more. Furthermore, the upper limit of the average particle size D90 can be appropriately set according to the desired performance and is not particularly limited, but is preferably 70.0 μm or less, more preferably 65.0 μm or less, even more preferably 60.0 μm or less, and especially preferably 55.0 μm or less.

[0054] To achieve a catalyst layer 21 having the above-described total particle size distribution, particularly a catalyst layer 21 with a reduced proportion of fine particles, it can be obtained, for example, by preparing it without milling the catalyst slurry, which was previously considered essential, or by pulverizing the base material particles such as alumina particles using a method that does not generate a large amount of fine particles, such as dry pulverization, and then blending them into the catalyst slurry. Furthermore, a catalyst layer 21 having the above-described total particle size distribution can also be achieved by individually adjusting the particle size of the single-metal oxide particles, two-metal oxide particles, or particles of arbitrary components contained in the catalyst layer 21.

[0055] For example, it can vary depending on the particle size distribution of other particles, and can be set appropriately according to the desired performance. However, the most frequent particle size of a single metal oxide particle contained in the catalyst layer 21 is preferably 5.0 μm or more and 40.0 μm or less, more preferably 7.5 μm or more and 30.0 μm or less, and even more preferably 9.0 μm or more and 20.0 μm or less.

[0056] On the other hand, it also varies depending on the particle size distribution of other particles, and can be set appropriately according to the desired performance. Although not particularly limited, the most frequent particle size of the two metal oxide particles contained in the catalyst layer 21 is preferably 5.0 μm or more and 40.0 μm or less, more preferably 10.0 μm or more and 35.0 μm or less, and even more preferably 15.0 μm or more and 30.0 μm or less.

[0057] Furthermore, it varies depending on the particle size distribution of other particles, and can be set appropriately according to the desired performance. While not particularly limited, the cumulative frequency of the most frequent particle size ± 5.0 μm of a single metal oxide particle contained in the catalyst layer 21 is preferably 5.0% or more, more preferably 10.0% or more, and even more preferably 15.0% or more. The upper limit of this cumulative frequency can be set appropriately according to the desired performance. While not particularly limited, it is preferably 40.0% or less, more preferably 35.0% or less, and even more preferably 30.0% or less.

[0058] On the other hand, it also varies depending on the particle size distribution of other particles, and can be set appropriately according to the desired performance, and is not particularly limited, but the cumulative frequency of the most frequent particle size ± 5.0 μm of the two metal oxide particles contained in the catalyst layer 21 is preferably 5.0% or more, more preferably 10.0% or more, and even more preferably 15.0% or more. The upper limit of the cumulative frequency can be set appropriately according to the desired performance, and is not particularly limited, but is preferably 50.0% or less, more preferably 45.0% or less, and even more preferably 40.0% or less. In this case, the cumulative frequency of the most frequent particle size ± 5.0 μm of the two metal oxide particles contained in the catalyst layer 21 is preferably 1 / 3 or more of the total, and more preferably 2 / 5 or more.

[0059] Furthermore, it also varies depending on the particle size distribution of other particles, and can be set appropriately according to the desired performance. Although not particularly limited, the average particle diameter D10 of the metal oxide particles contained in the catalyst layer 21 is preferably 0.5 μm or more, more preferably 0.6 μm or more, and even more preferably 0.7 μm or more. Also, the upper limit of the average particle diameter D10 can be set appropriately according to the desired performance. Although not particularly limited, it is preferably 15.0 μm or less, more preferably 13.5 μm or less, and even more preferably 12.0 μm or less.

[0060] On the other hand, it also varies depending on the particle size distribution of other particles, and can be set appropriately according to the desired performance, and is not particularly limited, but the average particle diameter D10 of the two metal oxide particles contained in the catalyst layer 21 is preferably 1.0 μm or more, more preferably 1.2 μm or more, and even more preferably 1.4 μm or more. Furthermore, the upper limit of the average particle diameter D10 can be set appropriately according to the desired performance, and is not particularly limited, but is preferably 10.0 μm or less, more preferably 7.0 μm or less, and even more preferably 4.0 μm or less.

[0061] Furthermore, it varies depending on the particle size distribution of other particles, and can be set appropriately according to the desired performance. While not particularly limited, the average particle diameter D50 of the metal oxide particles contained in the catalyst layer 21 is preferably 2.0 μm or more, more preferably 3.0 μm or more, and even more preferably 4.0 μm or more. The upper limit of the average particle diameter D50 can be set appropriately according to the desired performance. While not particularly limited, it is preferably 40.0 μm or less, more preferably 35.0 μm or less, and even more preferably 30.0 μm or less.

[0062] On the other hand, the particle size distribution of other particles also varies and can be set appropriately according to the desired performance, and is not particularly limited, but the average particle diameter D50 of the two metal oxide particles contained in the catalyst layer 21 is preferably 4.0 μm or more, more preferably 6.0 μm or more, and even more preferably 8.0 μm or more. Furthermore, the upper limit of the average particle diameter D50 can be set appropriately according to the desired performance, and is not particularly limited, but is preferably 25.0 μm or less, more preferably 20.0 μm or less, and even more preferably 15.0 μm or less.

[0063] [Method for manufacturing exhaust gas purification catalyst] The exhaust gas purification catalyst 100 described above can be manufactured by applying methods known in the industry, and the manufacturing method is not particularly limited. For example, the exhaust gas purification catalyst 100 can be manufactured by applying a catalyst slurry to the outer wall surface 12a of the partition wall 12 of a wall-flow type substrate 11, and blowing away any excess catalyst slurry as needed to form a catalyst layer 21. In this case, it is preferable to use a catalyst slurry that contains the first composite particles and the second composite particles described above, as well as optional components as needed, and satisfies the condition that the total particle size distribution of all particles is such that the most frequent particle size is 40 μm or less and the cumulative frequency of particles with a particle size of 5 μm or more is 65% or more.

[0064] The catalyst slurry for forming the catalyst layer 21 will now be described. The catalyst slurry contains first metal oxide particles supporting a first catalyst metal, second metal oxide particles supporting a second catalyst metal, and a solvent such as water. From the viewpoint of coating into the pores of the partition wall 12, the solid content of the catalyst slurry is preferably 1 to 50% by mass, more preferably 15 to 40% by mass, and even more preferably 20 to 35% by mass. Such a solid content tends to make it easier to coat the catalyst slurry onto the partition wall 12.

[0065] The method for applying the catalyst slurry to the wall-flow type substrate 11 can be carried out according to conventional methods and is not particularly limited. Various known coating methods, wash-coat methods, zone-coat methods, impregnation methods, etc., can be applied. The method for preparing the catalyst slurry can be carried out according to conventional methods and is not particularly limited. In this case, as described above, it is preferable not to wet-mill the catalyst slurry with a bead mill or ball mill. When adjusting the particle size distribution of the first metal oxide particles and the second metal oxide particles, it is preferable to dry-mill the first metal oxide particles and the second metal oxide particles beforehand prior to preparing the catalyst slurry, and then mix the first metal oxide particles and the second metal oxide particles after adjusting the particle size distribution. After applying the catalyst slurry to the wall-flow type substrate 11, drying or calcination can be carried out according to conventional methods. The drying temperature is not particularly limited, but for example, 70 to 200°C is preferred, and 80 to 150°C is more preferred. Furthermore, the firing temperature is not particularly limited, but is preferably 300°C to 1200°C, and more preferably 400°C to 600°C. The heating means used at this time can be known heating means such as an electric furnace or a gas furnace. The firing time is preferably 0.5 to 4.0 hours, and more preferably 0.5 to 3.0 hours. The firing atmosphere can be an oxidizing atmosphere, a reducing atmosphere, or a neutral atmosphere.

[0066] As described in detail above, the exhaust gas purification catalyst 100 of this embodiment is useful as a catalyst-coated particulate filter that purifies carbon monoxide (CO), hydrocarbons (HC), nitrogen oxides (NOx), etc., contained in exhaust gas, and also captures particulate matter and ash, etc., consisting of combustion components. In particular, the exhaust gas purification catalyst 100 for gasoline engines of this embodiment is particularly useful in light vehicles and small passenger cars where it is difficult to secure space for catalyst installation, as it has excellent purification performance as a three-way catalyst (TWC) that reduces NOx, CO, HC, etc. in exhaust gas, despite using a relatively small amount of precious metals, and has high PM collection performance while having low pressure loss.

[0067] In the above embodiment, an exhaust gas purification catalyst 100 comprising at least a catalyst layer 21 on a substrate 11 was exemplified. However, the exhaust gas purification catalyst 100 may comprise two or more catalyst layers 21, or two or more catalyst layers in addition to the catalyst layer 21. Furthermore, any other layer (e.g., a primer layer, an adhesive layer, etc.) may be interposed between these layers. The primer layer, underlayer, etc., can be one known in the industry, and its type is not particularly limited. For example, oxygen storage and release materials (OSCs) such as zeolite, cerium oxide (ceria: CeO2), ceria-zirconia composite oxide (CZ composite oxide), aluminum oxide (alumina: Al2O3) such as γ-alumina, β-alumina, δ-alumina, η-alumina, θ-alumina, etc., zirconium oxide (zirconia: ZrO2), silicon oxide (silica: SiO2), titanium oxide (titania: TiO2), etc., or composite oxides mainly composed of these oxides can be used. The amount of primer layer, undercoat, etc. applied is not particularly limited, but is preferably 1 to 150 g / L per liter of wall-flow type substrate 11, and more preferably 10 to 100 g / L.

[0068] In other words, in this specification, "at least a catalyst layer 21 is provided on the substrate 11" means that the substrate 11 and the catalyst layer 21 are arranged in this order, and the presence of other catalyst layers or other layers is not excluded. For example, the laminated structure of the exhaust gas purification catalyst 100 may be in any configuration in which the substrate 11 and the catalyst layer 21 are directly placed on each other (substrate 11 / catalyst layer 21, substrate 11 / catalyst layer 21 / other catalyst layer, substrate 11 / catalyst layer 21 / other layer, substrate 11 / catalyst layer 21 / other layer / other catalyst layer), or in any configuration in which the substrate 11 and the catalyst layer 21 are spaced apart via any other layer (for example, substrate 11 / other catalyst layer / catalyst layer 21, substrate 11 / other layer / catalyst layer 21, substrate 11 / other layer / other catalyst layer / catalyst layer 21, substrate 11 / other catalyst layer / other layer / catalyst layer 21). [Examples]

[0069] The features of the present invention will be further described in detail below with reference to examples and comparative examples, but the present invention is not limited in any way by these. That is, the materials, amounts used, proportions, processing content, processing procedures, etc., shown in the following examples can be changed as appropriate, as long as they do not depart from the spirit of the present invention. Furthermore, the various manufacturing conditions and evaluation result values ​​in the following examples have meaning as preferred upper or lower limits in embodiments of the present invention, and the preferred range may be defined by a combination of the aforementioned upper or lower limits and the values ​​of the following examples or the values ​​of the examples themselves.

[0070] [Raw materials used] Table 1 shows the various raw materials used in the examples and comparative examples. [Table 1] • Alumina particles 1: Commercially available alumina particles • Alumina particles 2: Alumina particles 1, dry-ground • Alumina particles 3: Commercially available alumina particles • CZ particles 1: Commercially available ceria-zirconia composite oxide particles (Composition ratio based on CeO2 / ZrO2: 3 / 7) • CZ particles 2: Commercially available ceria-zirconia composite oxide particles (Composition ratio based on CeO2 / ZrO2: 3 / 7)

[0071] [Honeycomb structure] The honeycomb structure 1 used in the examples and comparative examples of the present invention is as follows. The porosity and average pore diameter of the honeycomb structure below were determined from values ​​obtained by the mercury intrusion method measured at an intrusion pressure of 400 MPa. • Honeycomb type: Wall-flow type honeycomb structure • Material: Cordierite • Shape: Cylindrical • Size: Diameter 118.4mm, Height 127mm • Cell shape: Square • Cell density: 46.5 cel / cm 2 (300 cel / inch 2 ) • Cell partition thickness: 0.2 mm (8 milliinches) • Porosity: 63% • Average pore size (D50): 16 μm

[0072] [Pressure loss performance evaluation] The honeycomb catalysts of the obtained examples and comparative examples were installed in a pressure loss measuring device (manufactured by Tsukuba Rika Seiki Co., Ltd.), and room temperature air was introduced into the installed exhaust gas purification catalysts. The amount of air discharged from each honeycomb catalyst was 4 m³. 3 The differential pressure (kPa) between the air inlet and outlet sides of the honeycomb catalyst was measured when the pressure was at / min, and these values ​​were defined as the respective pressure losses.

[0073] [Evaluation of soot component collection performance] The honeycomb catalysts of the obtained examples and comparative examples were installed in vehicles equipped with 1.5L direct-injection turbo engines, respectively, and the amount of soot emitted during WLTC mode driving (PNtest) was measured using a solid particle count analyzer (manufactured by Horiba, Ltd., product name: MEXA-2100 SPCS). The soot collection efficiency was calculated based on the following formula 1 as the percentage reduction from the amount of soot components (PNblank) measured when the above test was performed without the exhaust gas purification catalyst. <Expression 1> Soot component collection rate (%) = 100 × (PNblank - PNtest) / PNblank (%)

[0074] (Example 1) A raw material slurry was prepared by mixing the following components with water and stirring it using a stirrer equipped with stirring blades. Without adjusting the particle size distribution by wet milling, a catalyst slurry 1 (solid content concentration: 36% by mass) containing alumina particles supported with the catalyst metals Pd and Rh, and non-alumina particles supported with the catalyst particles Pd and Rh was prepared. <Catalyst slurry 1> • Palladium nitrate aqueous solution (Pd metal equivalent): 0.667 g / L • Alumina particles 1: 10.67 g / L Rhodium nitrate aqueous solution (based on Rh metal): 0.1 g / L ·CZ particles 1:7.33g / L • Lanthanum hydroxide: 1.33 g / L • Neodymium hydroxide: 0.67 g / L

[0075] After supplying a predetermined amount of the catalyst slurry 1 to the honeycomb structure 1 from the open end face on the exhaust gas inlet side, an air blow treatment was performed from the open end face on the exhaust gas inlet side at an adjusted pressure and time, and the catalyst slurry 1 was spread onto the honeycomb structure 1 to a predetermined coating amount W1 and coating length T1 as shown in Table 2. In this way, the catalyst layer was coated onto the partition wall on the exhaust gas inlet side of the honeycomb structure 1 by the wash coat method from the open end face of each cell of the honeycomb structure 1, and after drying the obtained catalyst-coated honeycomb structure 1, a firing treatment was performed at 500°C for 2 hours in an atmospheric atmosphere to obtain the wall-flow type honeycomb catalyst (exhaust gas purification catalyst) of Example 1.

[0076] (Example 2) Except for using alumina particle 2 instead of alumina particle 1, the procedure was carried out in the same manner as in Example 1 to obtain the wall-flow type honeycomb catalyst (exhaust gas purification catalyst) of Example 2.

[0077] (Comparative Example 1) A catalyst slurry 2 was prepared by mixing the following components with water, stirring and mixing the raw material slurry using a stirrer equipped with stirring blades, and then adjusting the particle size distribution by wet milling using a ball mill, thereby preparing alumina particles supported with the catalyst metals Pd and Rh, and non-alumina particles supported with the catalyst particles Pd and Rh. <Catalyst Slurry 2> • Palladium nitrate aqueous solution (Pd metal equivalent): 0.667 g / L Alumina particles 1:20g / L Alumina particles 3: 20g / L Rhodium nitrate aqueous solution (based on Rh metal): 0.1 g / L ·CZ particles 2: 20g / L • Lanthanum hydroxide: 1.33 g / L • Neodymium hydroxide: 0.67 g / L

[0078] The procedure was carried out in the same manner as in Example 1, except that catalyst slurry 2 was used instead of catalyst slurry 1, and the coating amount W1 and coating length T1 of the catalyst layer were changed as shown in Table 2, to obtain Comparative Example 1, a wall-flow type honeycomb catalyst (exhaust gas purification catalyst).

[0079] (Comparative Example 2) The procedure was carried out in the same manner as in Comparative Example 1, except that the amounts of alumina particles 1, alumina particles 3, and CZ particles 2 used were each changed to 10 g / L, and the coating amount W1 of the catalyst layer was changed to 30 g / L, to obtain the wall-flow type honeycomb catalyst (exhaust gas purification catalyst) of Comparative Example 2.

[0080] (Comparative Example 3) The procedure was carried out in the same manner as in Comparative Example 1, except that the amounts of alumina particles 1, alumina particles 3, and CZ particles 2 used were each changed to 5 g / L, and the coating amount W1 of the catalyst layer was changed to 15 g / L, to obtain the wall-flow type honeycomb catalyst (exhaust gas purification catalyst) of Comparative Example 3.

[0081] Table 2 shows the particle size distribution of the catalyst slurry and the performance evaluation results of the honeycomb catalyst. [Table 2] [Industrial applicability]

[0082] The exhaust gas purification catalyst of the present invention exhibits excellent gas diffusion throughout the catalyst layer, and combines high PM capture efficiency with low pressure loss. Therefore, it can be widely and effectively used as a catalyst-coated particulate filter. In particular, it has excellent purification performance as a three-way catalyst (TWC) that reduces NOx, CO, HC, etc. in exhaust gas, and because it has high PM capture efficiency while having low pressure loss, it is especially useful as a GPF catalyst in light vehicles and small passenger cars where it is difficult to secure space for catalyst installation. According to the present invention, it is possible to realize an exhaust gas purification catalyst and a method for producing the same that exhibits excellent gas diffusion throughout the catalyst layer, high PM collection efficiency, and low pressure loss. Furthermore, according to the present invention, because of the excellent gas diffusion throughout the catalyst layer, it is possible to remove harmful components such as carbon monoxide (CO), hydrocarbons (HC), and nitrogen oxides (NOx) at lower temperatures compared to catalysts using the same amount of catalyst, and to realize an exhaust gas purification catalyst with enhanced catalytic activity. [Explanation of Symbols]

[0083] 100 ··· Catalyst for exhaust gas purification 11...Base material 11a... End on the exhaust gas inlet side 11b... End on the exhaust gas discharge side 12...Bulkhead 12a...Outer wall surface 13...Sealing wall 21 ···Catalyst layer S IN ...Introduction side cell S EM ...Discharge side cell P ···Stomata

Claims

1. A catalyst for purifying exhaust gas, comprising at least a substrate and a catalyst layer provided on the substrate, The catalyst layer contains two or more metal oxide particles, The metal oxide particles comprise at least first metal oxide particles supporting a first catalyst metal and second metal oxide particles supporting a second catalyst metal, wherein the first metal oxide particles are alumina particles and the second metal oxide particles are non-alumina particles, the average particle diameter D10 of the first metal oxide particles is 0.8 μm or more and 10.9 μm or less and the average particle diameter D50 is 4.9 μm or more and 28.2 μm or less, and the average particle diameter D10 of the second metal oxide particles is 1.0 μm or more and 10.0 μm or less. The total particle size distribution of all particles contained in the catalyst layer satisfies the following conditions: the most frequent particle size is 40.0 μm or less, and the cumulative frequency of particles with a diameter of 5.0 μm or more is 65.0% or more. Catalyst for exhaust gas purification.

2. The first metal oxide particles have a particle size distribution in which the most frequent particle size is 5.0 μm or more and 40.0 μm or less. The exhaust gas purification catalyst according to claim 1.

3. The second metal oxide particles have a particle size distribution in which the most frequent particle size is 5.0 μm or more and 40.0 μm or less, and the cumulative particle size distribution of the most frequent particle size ± 5.0 μm accounts for 1 / 3 or more of the total. The exhaust gas purification catalyst according to claim 1 or 2.

4. The second metal oxide particles include one or more selected from the group consisting of ceria and zirconia. A catalyst for exhaust gas purification according to any one of claims 1 to 3.

5. Based on a total of 100 parts by mass of the first metal oxide particles and the second metal oxide particles, the mixture contains 20 to 80 parts by mass of the first metal oxide particles and 80 to 20 parts by mass of the second metal oxide particles. A catalyst for exhaust gas purification according to any one of claims 1 to 4.

6. The first catalyst metal includes one or more selected from the group consisting of platinum, palladium, rhodium, and ruthenium. A catalyst for exhaust gas purification according to any one of claims 1 to 5.

7. The second catalyst metal includes one or more selected from the group consisting of platinum, palladium, rhodium, and ruthenium. A catalyst for exhaust gas purification according to any one of claims 1 to 6.

8. A method for manufacturing a catalyst for exhaust gas purification, A catalyst slurry containing two or more metal oxide particles, wherein the metal oxide particles include at least first metal oxide particles supporting a first catalyst metal and second metal oxide particles supporting a second catalyst metal, the first metal oxide particles are alumina particles and the second metal oxide particles are non-alumina particles, the average particle diameter D10 of the first metal oxide particles is 0.8 μm or more and 10.9 μm or less and the average particle diameter D50 is 4.9 μm or more and 28.2 μm or less, the average particle diameter D10 of the second metal oxide particles is 1.0 μm or more and 10.0 μm or less, and the total particle size distribution of all particles contained in the catalyst slurry satisfies the most frequent particle diameter being 40 μm or less and the cumulative frequency of particles with a particle diameter of 5 μm or more being 65% or more, and The process includes applying the catalyst slurry onto a substrate to form a catalyst layer. A method for manufacturing a catalyst for exhaust gas purification.

9. The catalyst slurry having the above-mentioned total particle size distribution is prepared without performing wet milling on the first metal oxide particles and the second metal oxide particles. A method for producing an exhaust gas purification catalyst according to claim 8.

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