Exhaust gas purification catalyst composition, exhaust gas purification catalyst using said exhaust gas purification catalyst composition, and method for manufacturing said exhaust gas purification catalyst composition

Abstract

The purpose of the present invention is to provide an exhaust gas purification catalyst composition which has improved heat resistance. In order to achieve this purpose, the present invention provides an exhaust gas purification catalyst composition which contains a composite that contains a Zr-based oxide, an Al oxide that is present independently of the Zr-based oxide, an alkaline earth metal oxide that is present independently of the Zr-based oxide, and a platinum group element, wherein: the content of Al in the composite in terms of oxide is 1% by mass to 15% by mass inclusive based on the mass of the composite; the content of the alkaline earth metal element in the composite in terms of oxide is 0.1% by mass to 7% by mass inclusive based on the mass of the composite; and the X-ray diffraction pattern of the exhaust gas purification catalyst composition after a heat treatment satisfies formula (1) 1 ≤ IA / IB (wherein IA represents the integrated intensity of a peak located at 2θ = 27.0°-29.0° and IB represents the integrated intensity of a peak located at 2θ = 29.0°-30.8°).

Description

Exhaust gas purification catalyst composition, exhaust gas purification catalyst using the exhaust gas purification catalyst composition, and method for manufacturing the exhaust gas purification catalyst composition.

[0001] The present invention relates to a catalytic composition for exhaust gas purification, a catalytic converter for exhaust gas purification using the catalytic composition, and a method for producing the catalytic composition.

[0002] Exhaust gases emitted from internal combustion engines of automobiles, motorcycles, and other vehicles contain harmful components such as hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NOx). To purify and neutralize these harmful components, platinum group elements such as Pt, Pd, and Rh are used as catalytic active components in exhaust gas purification catalysts. Pt and Pd are mainly involved in the oxidation and purification of HC and CO, while Rh is mainly involved in the reduction and purification of NOx.

[0003] As a support for carrying catalytically active components, zirconia (ZrO ２ ) is used (for example, Patent Document 1). However, zirconia has extremely low heat resistance. In this specification, "heat resistance" means that the phenomenon of sintering (a decrease in specific surface area) does not occur when exposed to high temperatures, and "high temperature" means usually 700°C or higher, preferably 850°C or higher, and more preferably 950°C or higher.

[0004] Given the extremely low heat resistance of zirconia, rare-earth element-stabilized zirconia, obtained by solid-solving rare-earth elements such as Y, La, and Nd into zirconia, is used as a carrier for supporting catalytically active components (for example, Patent Documents 2 and 3). Although the heat resistance of rare-earth element-stabilized zirconia has been improved, it is still insufficient.

[0005] As a technique to improve the heat resistance of zirconia, a technique has been proposed in which the surface of zirconia particles is modified with alumina particles (for example, Patent Document 4). The alumina particles present on the surface of the zirconia particles function as a physical barrier between the zirconia particles and can suppress sintering between them. However, when exposed to high temperatures, some of the alumina particles present on the surface of the zirconia particles solid-solve into the zirconia particles, so sintering between the zirconia particles cannot be sufficiently suppressed.

[0006] Japanese Patent Publication No. 2008-284553, Japanese Patent Publication No. 2000-051699, Japanese Patent Publication No. 2015-073961, International Publication No. 2002 / 066153 (brochure)

[0007] The present invention aims to provide an exhaust gas purification catalyst composition with improved heat resistance, an exhaust gas purification catalyst using the exhaust gas purification catalyst composition, and a method for producing the exhaust gas purification catalyst composition.

[0008] To solve the above problems, the present invention provides the following exhaust gas purification catalyst composition, exhaust gas purification catalyst, and method for producing the exhaust gas purification catalyst composition. [1] An exhaust gas purification catalyst composition comprising a composite comprising a Zr-based oxide, an Al oxide independently present from the Zr-based oxide, an alkaline earth metal oxide independently present from the Zr-based oxide, and a platinum group element, wherein the content of Al in the composite on an oxide basis is 1% by mass or more and 15% by mass or less based on the mass of the composite, the content of the alkaline earth metal element in the composite on an oxide basis is 0.1% by mass or more and 7% by mass or less based on the mass of the composite, and the X-ray diffraction pattern of the exhaust gas purification catalyst composition obtained by performing an X-ray diffraction method after heat treatment of the exhaust gas purification catalyst composition at 1000°C for 10 hours is given by the following formula (1): 1 ≤ I Ａ / I Ｂ ...(1) [wherein, I Ａ This represents the integrated intensity of the peak located between 2θ = 27.0° and 29.0°, and I Ｂ[1] The exhaust gas purification catalyst composition that satisfies the following conditions: [2] The exhaust gas purification catalyst composition according to [1], wherein the complex further comprises a rare earth oxide that exists independently of the Zr-based oxide. [3] The exhaust gas purification catalyst composition according to [2], wherein the content of the rare earth element in the complex, on an oxide basis, is 0.1% by mass or more and 5% by mass or less, based on the mass of the complex. [4] The exhaust gas purification catalyst composition according to [2] or [3], wherein the rare earth oxide is composed of one or more selected from the group consisting of La oxide, Nd oxide, Pr oxide and Y oxide. [5] The exhaust gas purification catalyst composition according to [4], wherein the rare earth oxide is composed of one or more selected from the group consisting of La oxide, Nd oxide and Pr oxide. [6] The exhaust gas purification catalyst composition according to [5], wherein the rare earth oxide is composed of La oxide. [7] The exhaust gas purification catalyst composition according to any one of [1] to [6], wherein the alkaline earth metal oxide is composed of Ba oxide. [8] The exhaust gas purification catalyst composition according to any one of [1] to [7], wherein the platinum group element is composed of Rh. [9] An exhaust gas purification catalyst comprising a substrate and a catalyst layer provided on the substrate, wherein the catalyst layer is composed of the exhaust gas purification catalyst composition according to any one of [1] to [8].

[10] A method for producing an exhaust gas purification catalyst composition, comprising the following steps: (a) preparing first Zr-based oxide particles having a monoclinic crystal structure; (b) supporting Al, an alkaline earth metal element, a platinum group element, and optionally a rare earth element on the first Zr-based oxide particles to produce an intermediate; and (c) calcining the intermediate to produce a composite comprising second Zr-based oxide particles, an Al oxide independently of the second Zr-based oxide particles, an alkaline earth metal oxide independently of the second Zr-based oxide particles, a platinum group element, and optionally a rare earth oxide independently of the Zr-based oxide particles.

[0009] The present invention provides an exhaust gas purification catalyst composition with improved heat resistance, an exhaust gas purification catalyst using the exhaust gas purification catalyst composition, and a method for producing the exhaust gas purification catalyst composition.

[0010] FIG. 1 is a partial end view showing a state in which an exhaust gas purification catalyst according to an embodiment is disposed in an exhaust passage of an internal combustion engine. FIG. 2 is an end view taken along line A-A of FIG. 1. FIG. 3 is an enlarged view of a region indicated by reference numeral R in FIG. 2. FIG. 4 is an end view taken along line B-B of FIG. 1. FIG. 5 is a diagram showing powder X-ray diffraction patterns of the catalyst compositions of Example 2 and 9 and Comparative Examples 1 to 3 and 5 after heat treatment.

[0011] <<Explanation of Terms>> The following explains the terms used in this specification. The following explanations apply to the whole of this specification unless otherwise specified.

[0012] <Abbreviations> "SEM" means a scanning electron microscope, "EDX" means energy dispersive X-ray spectroscopy, "SEM-EDX" means a scanning electron microscope-energy dispersive X-ray analysis method, "EPMA" means an electron probe microanalyzer, "XRF" means X-ray fluorescence analysis, "WDX" means wavelength dispersive X-ray analysis, and "ICP-AES" means inductively coupled plasma atomic emission spectrometry.

[0013] <Platinum Group Elements> The "platinum group elements" include Pt, Pd, Rh, Ru, Os, and Ir.

[0014] <Alkaline Earth Metal Elements> The "alkaline earth metal elements" include Mg, Ca, Sr, and Ba.

[0015] <Rare Earth Elements> The "rare earth elements" include Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu.

[0016] <Oxides> The meaning of the "oxides" of metal elements is as follows. Rare earth oxides excluding Ce oxide, Pr oxide, and Tb oxide are sesquioxides (M ２ O ３ , where M represents a rare earth element other than Ce, Pr, and Tb), Ce oxide is CeO ２ , Pr oxide is Pr ６ O １１ , Tb oxide is Tb ４ O ７ , and Al oxide is Al ２ O ３Zr oxide is ZrO ２ Mg oxide refers to MgO, Ca oxide refers to CaO, Sr oxide refers to SrO, and Ba oxide refers to BaO.

[0017] <Mass of Platinum Group Elements in Metallic Equivalents> "Mass of platinum group elements in metallic equivalents" refers to the mass of metals obtained by assuming that platinum group elements exist as metals composed of platinum group elements. For example, the metallic equivalent mass of Pd, the metallic equivalent mass of Pt, and the metallic equivalent mass of Rh refer to the mass of metallic Pd, metallic Pt, and metallic Rh, respectively.

[0018] <Mass of non-platinum group metal elements in terms of oxides> "Mass of non-platinum group metal elements in terms of oxides" refers to the mass of oxides obtained by assuming that the metal element exists as an oxide of the metal element. The meaning of "oxide" of a metal element is as described above.

[0019] For example, "mass of Al in terms of oxides" means that Al is Al ２ O ３ Assuming it exists as Al ２ O ３ The mass of an alkaline earth metal element is calculated as follows: "Mass of alkaline earth metal elements in terms of oxides" refers to the mass of an oxide calculated assuming that the alkaline earth metal element exists as an oxide of an alkaline earth metal element; and "Mass of rare earth elements in terms of oxides" refers to the mass of an oxide calculated assuming that the rare earth element exists as an oxide of a rare earth element.

[0020] <Mass of the composite> The "mass of the composite" refers to the total mass obtained by classifying all the metallic elements contained in the composite into platinum group elements and non-platinum group elements, calculating the metallic mass of the platinum group elements and the oxide mass of the non-platinum group elements, and then summing these two masses. In other words, the "mass of the composite" refers to the calculated mass obtained by summing the metallic mass of the platinum group elements contained in the composite and the oxide mass of the non-platinum group elements contained in the composite.

[0021] <Mass of Catalyst Composition> The "mass of the catalyst composition" refers to the total mass obtained by classifying all metal elements contained in the catalyst composition into platinum group elements and non-platinum group elements, determining the mass of the platinum group elements in terms of metal equivalent, and determining the mass of the non-platinum group elements in terms of oxide equivalent. In other words, the "mass of the catalyst composition" refers to the calculated mass obtained by adding the mass of the platinum group elements contained in the catalyst composition in terms of metal equivalent and the mass of the non-platinum group elements contained in the catalyst composition in terms of oxide equivalent.

[0022] <Metal content of platinum group elements in the composite and oxide content of non-platinum group metal elements in the composite> The "metal content of platinum group elements in the composite" (mass%) is defined by the following formula: Metal content of platinum group elements in the composite (mass%) = (Mass of platinum group elements in the composite in metal equivalent) / (Mass of the composite) × 100

[0023] The "content of non-platinum group metal elements in the composite, in terms of oxides" (mass%) is defined by the following formula: Content of non-platinum group metal elements in the composite, in terms of oxides (mass%) = (mass of non-platinum group metal elements in the composite, in terms of oxides) / (mass of the composite) × 100

[0024] For example, the "amount of Al in the composite as an oxide" (mass%), the "amount of alkaline earth metal elements in the composite as an oxide" (mass%), and the "amount of rare earth elements in the composite as an oxide" (mass%) are defined by the following formulas: Amount of Al in the composite as an oxide (mass%) = (Amount of Al in the composite) ２ O ３ (Converted mass) / (Mass of composite) × 100 Concentration of alkaline earth metal elements in the composite (mass%) = (Converted mass of alkaline earth metal elements in the composite) / (Mass of composite) × 100 Concentration of rare earth elements in the composite (mass%) = (Converted mass of rare earth elements in the composite) / (Mass of composite) × 100

[0025] If information on the raw materials used to form the composite is known, the content of platinum group elements in the composite (in terms of metal equivalent, mass%) and the content of non-platinum group metal elements in the composite (in terms of oxide equivalent, mass%) can be determined from the raw material information.

[0026] If information on the raw materials used to form the composite is unknown, the content of platinum group elements in metal equivalent (mass%) and the content of non-platinum group metal elements in oxide equivalent (mass%) can be determined by conventional methods such as SEM-EDX. Specifically, this is as follows:

[0027] Elemental analysis of the composites is performed using conventional methods such as SEM-EDX to identify the types of constituent elements of the composites and to determine the molar percentage of each identified metal element. For each of the 100 composites observed by SEM, the molar percentage of each metal element is determined, and the average value of the molar percentages of each metal element in the 100 composites is taken as the molar percentage of each metal element in the composite.

[0028] For each platinum group element in the composite, the V value is calculated using the following formula: V value = (molar percentage of each platinum group element in the composite) × (molar mass of each platinum group element)

[0029] For each metal element other than the platinum group elements in the composite, the W value is calculated using the following formula: W value = (molar percentage of each metal element other than the platinum group elements in the composite) × (molar mass of oxides of each metal element other than the platinum group elements)

[0030] The metallic content (mass %) of each platinum group element in the composite can be calculated using the following formula: Metallic content (mass %) of each platinum group element in the composite = (V value for each platinum group element) / {(Sum of V values ​​for all platinum group elements) + (Sum of W values ​​for all non-platinum metal elements)} × 100

[0031] The oxide content (mass %) of each metal element other than platinum group elements in the composite can be calculated using the following formula: Oxide content (mass %) of each metal element other than platinum group elements in the composite = (W value for each metal element other than platinum group elements) / {(Sum of V values ​​for all platinum group elements) + (Sum of W values ​​for all metal elements other than platinum group elements)} × 100

[0032] <Particles> The term "particles" includes primary particles, secondary particles, and mixtures thereof. Secondary particles are aggregated particles formed by the aggregation of primary particles. Examples of primary particle shapes include spherical, flake-shaped, columnar, needle-shaped, polyhedral, and irregular shapes. Spherical shapes include perfect spheres and ellipsoids. Flake-shaped shapes include flaky, thin, and flattened shapes. Columnar shapes include cylindrical, elliptical, and polygonal prism shapes, as well as shapes in which parts of cylindrical, elliptical, and polygonal prism shapes are missing.

[0033] <<Exhaust Gas Purification Catalyst Composition>> The exhaust gas purification catalyst composition of the present invention (hereinafter referred to as "this catalyst composition") will be described below.

[0034] The catalyst composition is, for example, in powder form. The catalyst composition may also be molded into any desired form, such as pellets or layers.

[0035] This catalyst composition contains a composite (hereinafter referred to as "this composite") comprising a Zr-based oxide, an Al oxide independently present from the Zr-based oxide, an alkaline earth metal oxide independently present from the Zr-based oxide, and a platinum group element.

[0036] This composite is, for example, particulate.

[0037] The platinum group elements consist of one or more elements selected from the group consisting of Pt, Pd, Rh, Ru, Os, and Ir. The platinum group elements may consist of one element selected from the above group, or two or more elements selected from the above group. From the viewpoint of improving exhaust gas purification performance, it is preferable that the platinum group elements consist of one or more elements selected from the group consisting of Pt, Pd, and Rh, and more preferably that they consist of Rh. The platinum group elements are included in this composite in the form of a catalytically active component containing platinum group elements, such as a metal composed of platinum group elements, an alloy containing platinum group elements, or a compound containing platinum group elements (for example, an oxide of a platinum group element). From the viewpoint of improving exhaust gas purification performance, it is preferable that the catalytically active component containing platinum group elements be in particulate form.

[0038] From the viewpoint of improving exhaust gas purification performance, the content of platinum group elements in this composite, in terms of metal equivalent, is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, and even more preferably 0.1% by mass or more, based on the mass of this composite. The upper limit can be adjusted as appropriate, taking into consideration the balance between exhaust gas purification performance and cost. The upper limit is preferably 10% by mass or less, more preferably 5% by mass or less, and even more preferably 1% by mass or less. Each of the above lower limits may be combined with any of the above upper limits.

[0039] From the viewpoint of improving exhaust gas purification performance, it is preferable that at least a portion of the catalytic active component containing platinum group elements is supported on a Zr-based oxide.

[0040] In this specification, "at least a portion of the catalytically active component is supported on a Zr-based oxide" means a state in which at least a portion of the catalytically active component is physically or chemically adsorbed or retained on the outer surface and / or the inner surface of the pores of the Zr-based oxide.

[0041] The fact that at least a portion of the catalytically active component is supported on a Zr-based oxide can be confirmed, for example, using SEM-EDX. Specifically, if, in the elemental mapping obtained by analyzing a sample obtained from this catalyst composition with SEM-EDX, at least a portion of the catalytically active component and the Zr-based oxide are present in the same region, it can be determined that at least a portion of the catalytically active component is supported on a Zr-based oxide.

[0042] "Zr-based oxides" are oxides containing Zr, and ZrO ２ This refers to oxides whose converted content is 50% by mass or more, based on the mass of the oxide.

[0043] Zr oxides are, for example, particulate. Zr oxides are used as carriers for components such as catalytic active components containing platinum group elements. From the viewpoint of improving the support of components such as catalytic active components containing platinum group elements, it is preferable that the Zr oxide is porous.

[0044] From the viewpoint of improving the support of components such as catalytic active components containing platinum group elements, the specific surface area of ​​the Zr-based oxide is preferably 10 m². ２ / g or more, more preferably 20m ２ / g or more, more preferably 50m ２ The amount is greater than or equal to / g. There is no particular upper limit. For example, the upper limit is 250m. ２ / g or less, 200m ２ / g or less or 150m ２ It may be less than or equal to / g. Each of the above lower limits may be combined with any of the above upper limits.

[0045] The specific surface area of ​​Zr-based oxides can be measured according to the "(3.5) Multi-point method" in "6.1 Quantitative Method" of JIS R1626:1996 "Method for Measuring Specific Surface Area of ​​Fine Ceramic Powders by Gas Adsorption BET Method". Specifically, nitrogen, which is the adsorbent gas, is used, and five measurements can be taken within the equilibrium relative pressure range of 0.05 to 0.35. The "BELSORP-miniX" manufactured by Microtrac-Bell can be used as the measuring device.

[0046] Zr-based oxides are distinguished from zirconia sols in terms of their average particle size. The average particle size of Zr-based oxides is preferably 0.1 μm to 100 μm, more preferably 0.5 μm to 50 μm, and even more preferably 1 μm to 20 μm. The lower limits above may be combined with any of the upper limits above. The method for measuring the average particle size of Zr-based oxides is as follows: A sample containing Zr-based oxides is observed using a scanning electron microscope (SEM), and the directional diameter (Ferret diameter) of 100 Zr-based oxides arbitrarily selected from within the field of view is measured, and the average value is taken as the average particle size of the Zr-based oxides.

[0047] As described later, the Zr-based oxide may contain additional elements other than Zr (hereinafter referred to as "additional element M"), as long as the X-ray diffraction pattern of the catalyst composition obtained by performing an X-ray diffraction method after heat treatment at 1000°C for 10 hours satisfies formula (1). Additional element M may consist of one metal element or two or more metal elements. Examples of additional element M include Al, alkaline earth metal elements, rare earth elements, etc.

[0048] In Zr-based oxides, the additional element M is a solid solution phase (for example, ZrO ２ It forms a solid solution phase with an oxide of the additional element M.

[0049] Examples of Zr-based oxides include zirconia (ZrO ２ Examples include oxides obtained by solid-solving an additional element M or its oxide in zirconia.

[0050] "Al oxide existing independently of Zr-based oxides" means Al oxide that is not solid-dissolved in Zr-based oxides. This composite may contain Al oxide that is solid-dissolved in Zr-based oxides, in addition to Al oxide that exists independently of Zr-based oxides.

[0051] Al oxides that exist independently of Zr-based oxides are, for example, particulate.

[0052] "Alkaline earth metal oxides existing independently of Zr-based oxides" means alkaline earth metal oxides that are not solid-dissolved in the Zr-based oxide. This composite may contain alkaline earth metal oxides that are solid-dissolved in the Zr-based oxide, in addition to alkaline earth metal oxides that exist independently of the Zr-based oxide.

[0053] The alkaline earth metal oxide, which exists independently of the Zr-based oxide, is composed of one or more selected from the group consisting of Mg oxide, Ca oxide, Sr oxide, and Ba oxide. The alkaline earth metal oxide may be composed of one selected from the above group, or it may be composed of two or more selected from the above group.

[0054] Alkaline earth metal oxides that exist independently of Zr-based oxides are, for example, particulate.

[0055] The X-ray diffraction pattern of the catalyst composition obtained by heat treatment at 1000°C for 10 hours followed by X-ray diffraction is given by the following formula (1): 1 ≤ I Ａ / I Ｂ ... (1) is satisfied.

[0056] In equation (1), I Ａ This represents the integrated intensity of the peak located between 2θ = 27.0° and 29.0°, and I Ｂ This represents the integrated intensity of the peak located between 2θ = 29.0° and 30.8°.

[0057] Hereafter, the heat treatment performed at 1000°C for 10 hours will simply be referred to as "heat treatment".

[0058] As will be described later, the I in the X-ray diffraction pattern of the catalyst composition after heat treatment Ａ / I Ｂ The value is preferably 100 or less, more preferably 50 or less, and even more preferably 20 or less.

[0059] Heat treatment is, for example, O ２ Gas: 0.50 vol%, Propylene: 0.11 vol%, Water vapor: 10 vol% and N ２ Gas: This can be carried out in an atmosphere where the gas consisting of the remaining portion is circulated.

[0060] After heat treatment and before X-ray diffraction analysis, the temperature of the catalyst composition is returned to room temperature. Therefore, the temperature of the catalyst composition when performing X-ray diffraction is room temperature. "Room temperature" usually means 20°C ± 10°C, preferably 20°C ± 5°C.

[0061] X-ray diffraction analysis is a powder X-ray diffraction method that typically uses CuKα rays as the X-ray source. X-ray diffraction analysis can be performed using commercially available X-ray diffractometers. The conditions for X-ray diffraction analysis can be those described in the examples. An X-ray diffraction pattern is obtained by X-ray diffraction analysis. The horizontal axis of the X-ray diffraction pattern is 2θ, and the vertical axis is intensity. The detection of each peak and the measurement of the integrated intensity can be performed as follows: Using the software included with the commercially available X-ray diffractometer, background intensity is removed from the X-ray diffraction pattern. Then, peak fitting (peak separation) is performed using a pseudo-Voigt function, the area of ​​each separated peak is determined, and the area of ​​each peak is taken as the integrated intensity of each peak.

[0062] The peak located at 2θ = 27.0° to 29.0° is a peak originating from the monoclinic crystal structure in Zr-based oxides. The integrated intensity of the peak located at 2θ = 27.0° to 29.0° is the largest among the integrated intensities of peaks originating from the monoclinic crystal structure in Zr-based oxides.

[0063] The peak located between 2θ = 29.0° and 30.8° is a peak originating from the tetragonal or cubic crystal structure in Zr-based oxides. The integrated intensity of the peak located between 2θ = 29.0° and 30.8° is the highest among the integrated intensities of peaks originating from the tetragonal or cubic crystal structure in Zr-based oxides.

[0064] The fact that the X-ray diffraction pattern of the catalyst composition after heat treatment satisfies formula (1) means that the main phase of the Zr-based oxide after heat treatment has a monoclinic crystal structure. The "main phase" refers to the crystal phase from which the peak with the maximum integrated intensity (main peak) originates in the X-ray diffraction pattern of the catalyst composition after heat treatment.

[0065] Zr-based oxides are ZrO ２ When composed of the above, both the X-ray diffraction pattern of the catalyst composition before heat treatment and the X-ray diffraction pattern of the catalyst composition after heat treatment satisfy formula (1).

[0066] When a Zr-based oxide contains an additional element M, the content of tetragonal or cubic phases in the Zr-based oxide after heat treatment increases with increasing content of the additional element M in terms of oxide, while the content of monoclinic phases in the Zr-based oxide after heat treatment decreases. Therefore, if the X-ray diffraction pattern of the catalyst composition after heat treatment satisfies formula (1), it means that the content of the additional element M in terms of oxide in the Zr-based oxide is small.

[0067] If the oxide content of additional element M in the Zr-based oxide is high, when exposed to high temperatures, a reaction is more likely to occur between the additional element M dissolved in the Zr-based oxide and Al oxide and / or alkaline earth metal oxides that exist independently of the Zr-based oxide. When a reaction occurs, atomic migration occurs inside and / or on the surface of the Zr-based oxide, reducing the specific surface area. From the viewpoint of suppressing the reduction in specific surface area caused by atomic migration inside and / or on the surface of the Zr-based oxide, it is necessary that the X-ray diffraction pattern of this catalyst composition after heat treatment satisfies formula (1).

[0068] In the Zr-based oxide before heat treatment, the additional element M may be present locally. The locally present additional element M is dispersed in the Zr-based oxide by heat treatment. As a result, even if the X-ray diffraction pattern of the catalyst composition before heat treatment satisfies formula (1), the X-ray diffraction pattern of the catalyst composition after heat treatment may not satisfy formula (1), and even if the X-ray diffraction pattern of the catalyst composition before heat treatment does not satisfy formula (1), the X-ray diffraction pattern of the catalyst composition after heat treatment may satisfy formula (1). The former case is not included in the present invention, but the latter case is included in the present invention.

[0069] The content of Al in oxide form in this composite is between 1% by mass and 15% by mass, based on the mass of the composite.

[0070] "The content of Al in oxide terms in this composite" means the content of Al in oxide terms derived from Al oxides that exist independently of the Zr-based oxide when the Zr-based oxide does not contain Al as an additional element M, and the sum of the content of Al in oxide terms derived from Al oxides that exist independently of the Zr-based oxide and the content of Al in oxide terms derived from the Zr-based oxide when the Zr-based oxide does contain Al as an additional element M.

[0071] The oxide content of alkaline earth metal elements in this composite is between 0.1% and 7% by mass, based on the mass of the composite.

[0072] "The content of alkaline earth metal elements in oxide form in this composite" means, if the Zr-based oxide does not contain alkaline earth metal elements as additional element M, the content of alkaline earth metal elements derived from alkaline earth metal oxides existing independently of the Zr-based oxide in oxide form; and if the Zr-based oxide contains alkaline earth metal elements as additional element M, it means the sum of the content of alkaline earth metal elements derived from alkaline earth metal oxides existing independently of the Zr-based oxide in oxide form and the content of alkaline earth metal elements derived from the Zr-based oxide in oxide form.

[0073] As described above, the fact that the X-ray diffraction pattern of the catalyst composition after heat treatment satisfies formula (1) means that the oxide content of the additional element M in the Zr-based oxide is small. Therefore, all or most of the oxide content of Al in this complex originates from Al oxides that exist independently of the Zr-based oxide, and the oxide content of Al in this complex reflects the content of Al oxides that exist independently of the Zr-based oxide. Similarly, all or most of the oxide content of alkaline earth metal elements in this complex originates from alkaline earth metal oxides that exist independently of the Zr-based oxide, and the oxide content of alkaline earth metal elements in this complex reflects the content of alkaline earth metal oxides that exist independently of the Zr-based oxide.

[0074] The heat resistance of this catalyst composition is improved when the composite contains a Zr-based oxide, an Al oxide independently present from the Zr-based oxide, and an alkaline earth metal oxide independently present from the Zr-based oxide, and the content of Al in oxide terms in this composite is 1% to 15% by mass based on the mass of the composite, and the content of alkaline earth metal elements in oxide terms in this composite is 0.1% to 7% by mass based on the mass of the composite. The mechanism is thought to be as follows.

[0075] Due to the interaction between Al oxides existing independently of Zr-based oxides and alkaline earth metal oxides existing independently of Zr-based oxides, these Al oxides and alkaline earth metal oxides, even when exposed to high temperatures, are less likely to solid dissolve in Zr-based oxides. Therefore, even when exposed to high temperatures, these Al oxides and alkaline earth metal oxides maintain their function as physical barriers between Zr-based oxides, suppressing sintering between Zr-based oxides, and as a result, the heat resistance of this catalyst composition is improved. In particular, at least a portion of the Al oxides existing independently of Zr-based oxides and at least a portion of the alkaline earth metal oxides existing independently of Zr-based oxides react to form a composite oxide (i.e., a composite oxide containing Al and alkaline earth metal elements). Since the composite oxide is more stable at high temperatures than Al oxide alone or alkaline earth metal oxide alone, it is less likely to solid dissolve in Zr-based oxides even when exposed to high temperatures. Therefore, even when exposed to high temperatures, the composite oxide maintains its function as a physical barrier between Zr-based oxides and can suppress sintering between Zr-based oxides, thereby improving the heat resistance of the catalyst composition. Hereinafter, the effect of suppressing sintering between Zr-based oxides will be referred to as the "sintering suppression effect."

[0076] The expression "This composite comprises an Al oxide independently of a Zr-based oxide and an alkaline earth metal oxide independently of a Zr-based oxide" also includes embodiments in which at least a portion of the Al oxide independently of a Zr-based oxide and at least a portion of the alkaline earth metal oxide independently of a Zr-based oxide form a composite oxide. The composite oxide may contain one alkaline earth metal element or two or more alkaline earth metal elements. In the composite oxide, the Al oxide and the alkaline earth metal oxide are chemically bonded. The composite oxide also includes solid solutions of Al oxide and alkaline earth metal oxide.

[0077] As a result of improved heat resistance, the catalyst composition can maintain its specific surface area even after exposure to high temperatures. The specific surface area of ​​the catalyst composition, measured after heat treatment at 1000°C for 10 hours, is preferably 26.6 m². ２ / g or more, more preferably 28.0m ２ / g or more, more preferably 29.0m ２ The amount is 100mg or more. There is no particular upper limit. For example, the upper limit is 100mg. ２ / g or less, 50m ２ / g or less or 40m ２ It may be less than or equal to / g. Each of the above lower limits may be combined with any of the above upper limits.

[0078] The specific surface area of ​​this catalyst composition can be measured by the method described in the examples. The heat treatment is, for example, O ２ Gas: 0.50 vol%, Propylene: 0.11 vol%, Water vapor: 10 vol% and N ２ Gas: This can be carried out in an atmosphere where the gas consisting of the remaining portion is circulated.

[0079] Preferred embodiments of the catalyst composition will be described below. Two or more preferred embodiments can be combined, and combinations of two or more preferred embodiments are also included in the present invention.

[0080] From the viewpoint of improving the sintering suppression effect and suppressing the decrease in specific surface area caused by atomic movement inside and / or on the surface of Zr-based oxides, the X-ray diffraction pattern of the catalyst composition after heat treatment is important. Ａ / I Ｂ The value of is preferably 2 or more, more preferably 3 or more, and even more preferably 4 or more. From the same viewpoint, the I value in the X-ray diffraction pattern of the catalyst composition after heat treatment Ａ / I Ｂ The value of is preferably 100 or less, more preferably 50 or less, and even more preferably 20 or less. Each of the above lower limits may be combined with any of the above upper limits.

[0081] From the viewpoint of improving the certainty that the X-ray diffraction pattern of the catalyst composition after heat treatment satisfies formula (1), the X-ray diffraction pattern of the catalyst composition before heat treatment is I Ａ / I Ｂ The value of is preferably 1 or more, more preferably 2 or more, even more preferably 3 or more, and even more preferably 4 or more. From the same viewpoint, the I value in the X-ray diffraction pattern of the catalyst composition before heat treatment Ａ / I Ｂ The value of is preferably 100 or less, more preferably 50 or less, and even more preferably 20 or less. Each of the above lower limits may be combined with any of the above upper limits.

[0082] From the viewpoint of improving the sintering suppression effect, it is preferable that at least a portion of the Al oxide, which exists independently of the Zr-based oxide, is present on the outer surface of the Zr-based oxide (i.e., supported on the outer surface of the Zr-based oxide).

[0083] From the viewpoint of improving the sintering suppression effect, it is preferable that at least a portion of the alkaline earth metal oxide, which exists independently of the Zr-based oxide, is present on the outer surface of the Zr-based oxide (i.e., supported on the outer surface of the Zr-based oxide).

[0084] From the viewpoint of improving the sintering suppression effect, it is preferable that at least a portion of the composite oxide formed by at least a portion of Al oxide that exists independently of the Zr-based oxide and at least a portion of alkaline earth metal oxide that exists independently of the Zr-based oxide is present on the outer surface of the Zr-based oxide (i.e., supported on the outer surface of the Zr-based oxide).

[0085] Because the ionic radius of Ba is relatively large, Ba oxide (including when existing as a composite oxide) that exists independently of Zr-based oxides does not easily dissolve in Zr-based oxides even when exposed to high temperatures. For this reason, Ba oxide (including when existing as a composite oxide) that exists independently of Zr-based oxides maintains its function as a physical barrier between Zr-based oxides even when exposed to high temperatures, suppressing sintering between Zr-based oxides, and as a result, the heat resistance of this catalyst composition is improved. Therefore, it is preferable that the alkaline earth metal oxide that exists independently of Zr-based oxides is composed of Ba oxide.

[0086] When platinum group elements receive an appropriate supply of electron pairs from coexisting components, their catalytic activity improves. On the other hand, ZrO ２This component has the property of attracting electron pairs, i.e., a Lewis acid. Therefore, in order to enhance the catalytic activity of platinum group elements in this composite, it is necessary that the composite contains an appropriate amount of a component that has the property of supplying electron pairs to platinum group elements, i.e., a Lewis base. Examples of Lewis bases include rare earth oxides. When rare earth element-stabilized zirconia, as described in the background art, is used as a support for the catalytically active component, the rare earth oxide acts as a Lewis base. This composite is advantageous over rare earth element-stabilized zirconia in that sintering between Zr-based oxides is suppressed. However, as described above, the fact that the X-ray diffraction pattern of this catalyst composition after heat treatment satisfies formula (1) means that the oxide-equivalent content of the additional element M in the Zr-based oxide is small. Therefore, the oxide-equivalent content of rare earth elements in the Zr-based oxide is small, and the Lewis base content in the Zr-based oxide is small. For this reason, the effect of suppressing sintering between Zr-based oxides is not easily reflected in the improvement of the exhaust gas purification performance of the catalytically active component. Therefore, it is preferable that the composite further contains rare earth oxides that exist independently of the Zr-based oxides. This allows the X-ray diffraction pattern of the catalyst composition after heat treatment to satisfy formula (1), while allowing Lewis bases to be present on the surface of the Zr-based oxides, thereby achieving both a sintering suppression effect and an improvement in the exhaust gas purification performance of the catalytic active components. Hereinafter, the improvement in the exhaust gas purification performance of the catalytic active components will be referred to as the "purification performance improvement effect." Furthermore, the rare earth oxides that exist independently of the Zr-based oxides do not readily dissolve in the Zr-based oxides even when exposed to high temperatures, and maintain their function as a physical barrier between the Zr-based oxides, thus contributing to the sintering suppression effect. Moreover, even when exposed to high temperatures, the reaction between the additional element M dissolved in the Zr-based oxides and the rare earth oxides that exist independently of the Zr-based oxides is unlikely to occur, so a decrease in specific surface area due to atomic movement inside and / or on the surface of the Zr-based oxides is unlikely to occur.

[0087] "Rare earth oxides existing independently of Zr-based oxides" means rare earth oxides that are not solid-dissolved in the Zr-based oxide. This composite may contain not only rare earth oxides existing independently of Zr-based oxides, but also rare earth oxides that are solid-dissolved in the Zr-based oxide.

[0088] Rare earth oxides that exist independently of Zr-based oxides are, for example, particulate.

[0089] From the viewpoint of improving the sintering suppression effect and the purification performance improvement effect, it is preferable that at least a portion of the rare earth oxide that exists independently of the Zr-based oxide is present on the outer surface of the Zr-based oxide (i.e., supported on the outer surface of the Zr-based oxide).

[0090] At least a portion of rare earth oxides existing independently of Zr-based oxides, at least a portion of Al oxides existing independently of Zr-based oxides, and / or at least a portion of alkaline earth metal oxides existing independently of Zr-based oxides may form a composite oxide (i.e., a composite oxide containing a rare earth element and Al and / or an alkaline earth metal element). The expression "This composite contains Al oxides existing independently of Zr-based oxides, alkaline earth metal oxides existing independently of Zr-based oxides, and rare earth oxides existing independently of Zr-based oxides" also includes embodiments in which at least a portion of rare earth oxides existing independently of Zr-based oxides, at least a portion of Al oxides existing independently of Zr-based oxides, and / or at least a portion of alkaline earth metal oxides existing independently of Zr-based oxides form a composite oxide. The composite oxide may contain one alkaline earth metal element or two or more alkaline earth metal elements. The composite oxide may contain one rare earth element or two or more rare earth elements. In the composite oxide, the rare earth oxide and Al oxide and / or alkaline earth metal oxide are chemically bonded. The composite oxide also includes solid solutions of the rare earth oxide and Al oxide and / or alkaline earth metal oxide. From the viewpoint of improving the sintering suppression effect and the purification performance improvement effect, it is preferable that at least a portion of the composite oxide exists on the outer surface of the Zr-based oxide (i.e., is supported on the outer surface of the Zr-based oxide).

[0091] The rare earth oxides, which exist independently of Zr-based oxides, consist of one or more selected from the group consisting of Sc oxide, Y oxide, La oxide, Ce oxide, Pr oxide, Nd oxide, Pm oxide, Sm oxide, Eu oxide, Gd oxide, Tb oxide, Dy oxide, Ho oxide, Er oxide, Tm oxide, Yb oxide, and Lu oxide. The rare earth oxide may consist of one selected from the above group, or it may consist of two or more selected from the above group.

[0092] From the viewpoint of improving the sintering suppression effect and the purification performance improvement effect, it is preferable that the rare earth oxide consists of one or more selected from the group consisting of La oxide, Nd oxide, Pr oxide and Y oxide, and more preferably that it consists of one or more selected from the group consisting of La oxide, Nd oxide and Pr oxide.

[0093] Because La has a relatively large ionic radius, La oxides existing independently of Zr-based oxides (including those existing as composite oxides) are less likely to solid dissolve in Zr-based oxides even when exposed to high temperatures. Therefore, La oxides existing independently of Zr-based oxides (including those existing as composite oxides) can maintain their function as a physical barrier between Zr-based oxides even when exposed to high temperatures, effectively suppressing sintering between Zr-based oxides, and as a result, the heat resistance of this catalyst composition is improved. For this reason, it is even more preferable that the rare earth oxide existing independently of Zr-based oxides is composed of La oxide.

[0094] From the viewpoint of improving the certainty that the X-ray diffraction pattern of the catalyst composition after heat treatment satisfies formula (1), the content of the additional element M in the Zr-based oxide on an oxide basis (hereinafter referred to as "content C1") is preferably 5% by mass or less, more preferably 3% by mass or less, and even more preferably 1% by mass or less, based on the mass of the Zr-based oxide. The lower limit is 0% by mass.

[0095] Zr in Zr oxides ２Since the converted content (hereinafter referred to as "content C2") = 100% by mass - content C1, content C2 is preferably 95% by mass or more, more preferably 97% by mass or more, and even more preferably 99% by mass or more, based on the mass of Zr-based oxide. The upper limit is 100% by mass.

[0096] The content C1 and C2 are defined by the following formulas: Content C1 = (mass of additional element M in Zr oxide in oxide form) / (mass of Zr oxide) × 100 Content C2 = (Zr in Zr oxide) ２ (Converted mass) / (Mass of Zr-based oxide) × 100

[0097] "Mass of Zr-based oxides" refers to the total mass of oxides of the metal elements in the Zr-based oxide, calculated assuming that each metal element exists as an oxide. The meaning of "oxide" of a metal element is as described above.

[0098] If the additional element M consists of one type of metallic element, the content C1 refers to the content of that one type of metallic element in terms of oxides. If the additional element M consists of two or more types of metallic elements, the content C1 refers to the total content of those two or more metallic elements in terms of oxides.

[0099] If the composition of the Zr-based oxide is known, the C1 and C2 content can be determined from the composition of the Zr-based oxide.

[0100] If the composition of the Zr oxide is unknown, the content C1 and C2 can be determined by analyzing a sample containing the Zr oxide by EDX, obtaining an elemental mapping, and performing an EDX elemental analysis of the specified Zr oxide. Specifically, by qualitatively identifying (color-coding) the Zr oxide and other particles using elemental mapping, and then performing a compositional analysis (elemental analysis) on the specified Zr oxide, the content C1 and C2 for the specified Zr oxide can be determined.

[0101] From the viewpoint of improving the sintering suppression effect, the content of Al in oxide terms in this composite is preferably 1% to 15% by mass, more preferably 2% to 10% by mass, and even more preferably 3% to 7% by mass, based on the mass of this composite. Each of the above lower limits may be combined with any of the above upper limits.

[0102] From the viewpoint of improving the sintering suppression effect, the content of alkaline earth metal elements in oxide terms in this composite is preferably 0.1% to 7% by mass, more preferably 0.5% to 5% by mass, and even more preferably 1% to 3% by mass, based on the mass of this composite. Each of the above lower limits may be combined with any of the above upper limits.

[0103] From the viewpoint of improving the sintering suppression effect and the purification performance improvement effect, the content of rare earth elements in oxide form in this composite is preferably 0.05% to 10% by mass, more preferably 0.1% to 5% by mass, and even more preferably 0.5% to 3% by mass, based on the mass of this composite. Each of the above lower limits may be combined with any of the above upper limits.

[0104] "The oxide content of rare earth elements in this composite" means, if the Zr-based oxide does not contain any rare earth elements as additional element M, the oxide content of rare earth elements derived from rare earth oxides existing independently of the Zr-based oxide; and if the Zr-based oxide contains rare earth elements as additional element M, it means the sum of the oxide content of rare earth elements derived from rare earth oxides existing independently of the Zr-based oxide and the oxide content of rare earth elements derived from the Zr-based oxide.

[0105] As described above, the fact that the X-ray diffraction pattern of the catalyst composition after heat treatment satisfies formula (1) means that the oxide-equivalent content of the additional element M in the Zr-based oxide is small. Therefore, all or most of the oxide-equivalent content of rare earth elements in this complex originates from rare earth oxides existing independently of the Zr-based oxide, and the oxide-equivalent content of rare earth elements in this complex reflects the content of rare earth oxides existing independently of the Zr-based oxide.

[0106] If the content of rare earth oxides, which exist independently of Zr-based oxides, is excessive, platinum group elements will have an excess of electron pairs, and the amount of O in the exhaust gas will increase. ２ When the excess electron pairs react, platinum group elements are more likely to be converted into oxides with low catalytic activity. If the oxide content of rare earth elements in this composite is within the above range, the content of rare earth oxides existing independently of Zr-based oxides will be within a suitable range, and the occurrence of such problems can be suppressed.

[0107] This catalyst composition may contain other components in addition to the composite. Other components include, for example, composites of catalytically active components and carriers other than the composite, and oxygen storage materials. Examples of carriers included in composites of catalytically active components and carriers other than the composite include Al-containing oxide particles (e.g., alumina particles, modified alumina particles obtained by modifying the surface of alumina particles with a metal element other than Al or its oxide, Al-containing composite oxide particles obtained by solid-solving a metal element other than Al or its oxide in alumina, etc.), and Ti-containing oxide particles, etc. Examples of oxygen storage materials include composite oxides containing Ce and Zr, etc.

[0108] The content of this composite in the catalyst composition is preferably 10% by mass or more, more preferably 20% by mass or more, and even more preferably 50% by mass or more, based on the mass of the catalyst composition. The upper limit is 100% by mass.

[0109] The mass percentage (%) of the composite compound in this catalyst composition is defined by the following formula: Mass percentage (%) of the composite compound in this catalyst composition = (Mass of the composite compound in this catalyst composition) / (Mass of the catalyst composition) × 100

[0110] If information on the raw materials used in the manufacture of this catalyst composition is known, the content of this composite in this catalyst composition can be determined from the information on the raw materials.

[0111] If information on the raw materials used in the production of this catalyst composition is unknown, the content of this composite in the catalyst composition can be determined by conventional methods such as SEM-EDX. Specifically, it is as follows:

[0112] (1) Elemental mapping is performed on a sample obtained from the catalyst composition using a standard method such as SEM-EDX to identify the types of particles contained in the sample (this composite and other particles). (2) For each type of particle, elemental analysis is performed on a randomly selected number of particles (e.g., 50 particles) using SEM-EDX to identify the types of constituent elements of the particles and to determine the oxide content (mass%) of each identified metal element. For each type of particle, the average value of the oxide content (mass%) of each metal element is calculated from the analysis results of a number of particles (e.g., 50 particles), and this average value is taken as the oxide content (mass%) of each metal element in each type of particle. (3) Elemental analysis is performed on a sample obtained from the catalyst composition using a standard method such as SEM-EDX to identify the types of constituent elements of the entire sample. Of the identified metal elements, the oxide content (mass%) of each metal element in the sample is determined for the metal elements identified in (2) above. (4) The content of each type of particle in the sample is determined by creating and solving an equation that expresses the relationship between the content of each metal element in terms of oxides (mass%) in the sample, the content of each metal element in terms of oxides (mass%) in each type of particle, and the content of each type of particle in the sample (mass%). The content of this composite in the sample (mass%) is then taken as the content of this composite in the catalyst composition (mass%).

[0113] ≪Method for Manufacturing Exhaust Gas Purification Catalyst Composition≫ The method for manufacturing an exhaust gas purification catalyst composition (hereinafter referred to as "this manufacturing method") is described below. This manufacturing method is suitable for manufacturing this catalyst composition, but the composition manufactured by this manufacturing method is not limited to this catalyst composition.

[0114] This manufacturing method includes the following steps: (a) preparing first Zr-based oxide particles having a monoclinic crystal structure; (b) supporting Al, alkaline earth metal elements, platinum group elements, and optionally rare earth elements on the first Zr-based oxide particles to produce an intermediate; and (c) calcining the intermediate to produce a composite containing second Zr-based oxide particles, Al oxide independently of the second Zr-based oxide particles, alkaline earth metal oxide independently of the second Zr-based oxide particles, platinum group elements, and optionally rare earth oxide independently of the Zr-based oxide particles.

[0115] The first Zr-based oxide particles prepared in step (a) will be described below.

[0116] The explanation regarding Zr-based oxides given in the section on "Compositions for Exhaust Gas Purification" also applies to the first Zr-based oxide particles prepared in step (a), unless otherwise specified.

[0117] The fact that the first Zr-based oxide particles have a monoclinic crystal structure can be confirmed by performing X-ray diffraction on the first Zr-based oxide particles. Unless otherwise specified, the explanation of the X-ray diffraction analysis method performed in the section on "Compositions for Exhaust Gas Purification" also applies to the X-ray diffraction method for the first Zr-based oxide particles. The X-ray diffraction method for the first Zr-based oxide particles is performed at room temperature without heat treatment of the first Zr-based oxide particles. The meaning of "room temperature" is as described above.

[0118] In the X-ray diffraction pattern of the first Zr-based oxide particles, if one or more peaks, preferably two or more, more preferably three or more, are present at all positions selected from 2θ = 27.0° to 29.0°, 2θ = 30.5° to 32.5°, 2θ = 23.0° to 25.5°, and 2θ = 39.2° to 42.4°, it can be determined that the first Zr-based oxide particles have a monoclinic crystal structure.

[0119] When producing the catalyst composition by this manufacturing method, from the viewpoint of improving the certainty that the X-ray diffraction pattern of the catalyst composition after heat treatment satisfies formula (1), the X-ray diffraction pattern of the first Zr-based oxide particles isＡ / I Ｂ The value of is preferably 1 to 100, more preferably 3 to 50, and even more preferably 4 to 20. Each of the above lower limits may be combined with any of the above upper limits. Ａ The significance and I Ｂ The significance of this is as stated above.

[0120] When producing the catalyst composition by this manufacturing method, from the viewpoint of improving the certainty that the X-ray diffraction pattern of the catalyst composition after heat treatment satisfies formula (1), the content of the additional element M in the first Zr-based oxide particles on an oxide basis (hereinafter referred to as "content C3") is preferably 5% by mass or less, more preferably 3% by mass or less, and even more preferably 1% by mass or less, based on the mass of the first Zr-based oxide particles. The lower limit is 0% by mass.

[0121] Zr in the first Zr-based oxide particles ２ Since the converted content (hereinafter referred to as "content C4") = 100% by mass - content C3, content C4 is preferably 95% by mass or more, more preferably 97% by mass or more, and even more preferably 99% by mass or more, based on the mass of the first Zr-based oxide particles. The upper limit is 100% by mass.

[0122] The C3 and C4 content are defined by the following formulas: C3 content = (mass of additional element M in the first Zr-based oxide particles in oxide form) / (mass of the first Zr-based oxide particles) × 100 C4 content = (Zr in the first Zr-based oxide particles) ２ (Converted mass) / (Mass of the first Zr-based oxide particle) × 100

[0123] "The mass of the first Zr-based oxide particle" refers to the total mass of the oxides of the metal elements, calculated by assuming that each metal element in the first Zr-based oxide particle exists as an oxide. The meaning of "oxide" of a metal element is as described above.

[0124] If the additional element M consists of one type of metallic element, the content C3 refers to the content of that one type of metallic element in terms of oxides. If the additional element M consists of two or more types of metallic elements, the content C3 refers to the total content of those two or more metallic elements in terms of oxides.

[0125] The following describes process (b).

[0126] Step (b) includes a step of supporting a platinum group element on the first Zr-based oxide particles (hereinafter referred to as the "PG supporting step"), a step of supporting Al on the first Zr-based oxide particles (hereinafter referred to as the "Al supporting step"), and a step of supporting an alkaline earth metal element on the first Zr-based oxide particles (hereinafter referred to as the "AE supporting step"). Step (b) may optionally include a step of supporting a rare earth element on the first Zr-based oxide particles (hereinafter referred to as the "RE supporting step").

[0127] The order in which the PG loading process, Al loading process, AE loading process, and RE loading process are carried out is not particularly limited. Two or more processes may be carried out simultaneously.

[0128] When producing the catalyst composition by this manufacturing method, it is preferable that the Al and alkaline earth metal elements are supported on the first Zr oxide particles in close proximity to each other in order to facilitate the interaction between Al oxide, which exists independently of the Zr oxide, and alkaline earth metal oxide, which exists independently of the Zr oxide, and in particular, the formation of a composite oxide (i.e., a composite oxide containing Al and alkaline earth metal elements) through the reaction of at least a portion of the Al oxide, which exists independently of the Zr oxide, and at least a portion of the alkaline earth metal oxide, which exists independently of the Zr oxide. Therefore, it is preferable to carry out the PG supporting step and the RE supporting step after carrying out the Al supporting step and the AE supporting step. The Al supporting step may be carried out before the AE supporting step, after the AE supporting step, or simultaneously with the AE supporting step. The PG supporting step may be carried out before the RE supporting step, after the RE supporting step, or simultaneously with the RE supporting step.

[0129] <PG Loading Process> The PG loading process will be explained below.

[0130] The PG loading process can be carried out by impregnation. Specifically, the PG loading process can be carried out by mixing a platinum group element source and first Zr-based oxide particles in a solvent. The first Zr-based oxide particles subjected to the PG loading process may be first Zr-based oxide particles that have not been subjected to any of the PG loading process, Al loading process, AE loading process, or RE loading process, or they may be first Zr-based oxide particles that have been subjected to one or more of the Al loading process, AE loading process, and RE loading process.

[0131] The amount of platinum group elements supported on the first Zr-based oxide particles is adjusted so that the metallic content of the platinum group elements in the composite produced by step (c) falls within a desired range based on the mass of the composite.

[0132] The solvent used in the PG loading process is preferably water. The water is preferably pure water, such as deionized water.

[0133] Examples of platinum group element sources include platinum group element-containing compounds such as platinum group element salts, platinum group element oxides, platinum group element hydroxides, and platinum group element organic complex compounds, as well as platinum group element metal nanoparticles. One type of platinum group element source may be used alone, or two or more types of platinum group element sources may be used in combination.

[0134] The platinum group element source may exist in the solvent in its original state, or in an ionized state.

[0135] Examples of platinum group element salts include nitrates, ammine complex salts, acetates, chlorides, and sulfates.

[0136] Examples of Rh oxides include, ２ O ３ , RhO ２ Examples include Rh(OH) ３ , RhO ２ ・xH ２ Examples include O.

[0137] Examples of Pt oxides include PtO, PtO ２ , Pt３ O ４ Examples include Pt hydroxides such as Pt(OH) ２ Pt(OH) ４ These are some examples.

[0138] Examples of Pd oxides include PdO, and examples of Pd hydroxides include Pd(OH) ２ , Pd(OH) ４ These are some examples.

[0139] From the viewpoint of sufficiently dispersing the platinum group element source on the surface of the first Zr-based oxide, the platinum group element source is preferably a salt of a platinum group element, and the salt of the platinum group element is preferably water-soluble.

[0140] Examples of water-soluble Rh salts include rhodium nitrate, rhodium chloride, and rhodium sulfate.

[0141] Examples of water-soluble Pt salts include dinitrodiamine platinum(II), platinum(IV) chloride, platinum(IV) bromide, platinum(IV) iodide, tetradichloroammineplatinum(IV), platinum(II) acetylacetonate, tetraammineplatinum(II) nitrate, tetraammineplatinum(II) hydroxide, and tetraammineplatinum(II) chloride.

[0142] Examples of water-soluble Pd salts include palladium nitrate, palladium chloride, palladium acetate, palladium sulfate, and dinitrodiamine palladium nitrate.

[0143] <Al loading process> The Al loading process will be explained below.

[0144] The Al loading process can be carried out by impregnation. Specifically, the Al loading process can be carried out by mixing an Al source and first Zr-based oxide particles in a solvent. The first Zr-based oxide particles subjected to the Al loading process may be first Zr-based oxide particles that have not been subjected to any of the PG loading process, Al loading process, AE loading process, or RE loading process, or they may be first Zr-based oxide particles that have been subjected to one or more of the PG loading process, AE loading process, and RE loading process.

[0145] The amount of Al to be supported on the first Zr-based oxide particles is the amount of Al in the composite produced by step (c). ２ O ３ The converted content is adjusted to fall within the desired range based on the mass of the complex.

[0146] The solvent used in the Al loading process is the same as the solvent used in the PG loading process.

[0147] Examples of Al sources include Al-containing compounds such as Al salts, Al oxides, Al hydroxides, and Al oxide hydrates. One type of Al source may be used alone, or two or more types of Al sources may be used in combination.

[0148] The Al source may exist in the solvent in its original state, or in an ionized state.

[0149] Examples of Al salts include nitrates, sulfates, and chlorides.

[0150] From the viewpoint of sufficiently dispersing the Al source on the surface of the first Zr-based oxide, the Al salt is preferably water-soluble.

[0151] Examples of water-soluble Al salts include nitrates, sulfates, and chlorides.

[0152] Examples of Al oxides include alumina sol and aluminum oxide powder. Aluminum oxide powder is distinguished from alumina sol in terms of its average particle size.

[0153] The average particle size of the aluminum oxide powder is preferably 0.5 μm to 50 μm, more preferably 1 μm to 30 μm, and even more preferably 3 μm to 20 μm. Each of the above lower limits may be combined with any of the above upper limits.

[0154] The average particle size of the alumina sol is preferably 1 nm to 300 nm, more preferably 2 nm to 100 nm, and even more preferably 3 nm to 50 nm. Each of the above lower limits may be combined with any of the above upper limits.

[0155] The method for measuring the average particle size of aluminum oxide powder and alumina sol is the same as the method for measuring the average particle size of Zr-based oxides.

[0156] Al hydroxide is Al(OH) ３ That is the case.

[0157] Examples of Al oxide hydrates include alumina monohydrate and alumina trihydrate. Examples of alumina monohydrate include boehmite (α-AlOOH) and diaspore (β-AlOOH). Boehmite may be a so-called pseudo-boehmite containing one or more water molecules between its layers. Examples of alumina trihydrate include gibbsite (α-Al(OH)) ３ ), Byerlite (β-Al(OH) ３ Examples include:

[0158] From the viewpoint of sufficiently dispersing the Al source on the surface of the first Zr-based oxide, the Al source preferably comprises at least one selected from Al salts and alumina sols, and more preferably comprises at least alumina sol. In addition to at least one selected from Al salts and alumina sols, the Al source may also comprise Al oxides other than alumina sol (e.g., aluminum oxide powder). In one embodiment, the Al source is composed of an Al salt. In another embodiment, the Al source is composed of alumina sol. In yet another embodiment, the Al source is composed of alumina sol and Al oxides other than alumina sol (e.g., aluminum oxide powder).

[0159] <AE Supporting Process> The AE supporting process will be explained below.

[0160] The AE loading process can be carried out by impregnation. Specifically, the AE loading process can be carried out by mixing an alkaline earth metal element source with the first Zr-based oxide particles in a solvent. The first Zr-based oxide particles subjected to the AE loading process may be first Zr-based oxide particles that have not been subjected to any of the PG loading process, Al loading process, AE loading process, or RE loading process, or they may be first Zr-based oxide particles that have been subjected to one or more of the PG loading process, Al loading process, and RE loading process.

[0161] The amount of alkaline earth metal element supported on the first Zr-based oxide particles is adjusted so that the oxide content of the alkaline earth metal element in the composite produced by step (c) falls within a desired range based on the mass of the composite.

[0162] The solvent used in the AE loading process is the same as the solvent used in the PG loading process.

[0163] Examples of alkaline earth metal element sources include alkaline earth metal element-containing compounds such as alkaline earth metal element salts, alkaline earth metal element oxides, and alkaline earth metal element hydroxides. One type of alkaline earth metal element source may be used alone, or two or more types of alkaline earth metal element sources may be used in combination.

[0164] The alkaline earth metal element source may exist in the solvent in its original state or in an ionized state.

[0165] Examples of salts of alkaline earth metal elements include acetates, carbonates, and sulfates.

[0166] The significance of oxides of alkaline earth metal elements is as described above.

[0167] Mg hydroxide is Mg(OH) ２ Ca hydroxide is Ca(OH) ２ Sr hydroxide is Sr(OH) ２ Ba hydroxide is (OH) ２ That is the case.

[0168] From the viewpoint of sufficiently dispersing the alkaline earth metal source on the surface of the first Zr-based oxide, the alkaline earth metal element source is preferably a salt of an alkaline earth metal element, and the alkaline earth metal element salt is preferably water-soluble.

[0169] Examples of water-soluble alkaline earth metal element salts include acetates and nitrates.

[0170] <RE Loading Process> The RE loading process will be explained below.

[0171] The RE loading step can be carried out by an impregnation method. Specifically, the RE loading step can be carried out by mixing a rare earth element source and the first Zr-based oxide particles in a solvent. The first Zr-based oxide particles subjected to the RE loading step may be the first Zr-based oxide particles that have not been subjected to any of the PG loading step, the Al loading step, the AE loading step, or the RE loading step, or may be the first Zr-based oxide particles after being subjected to one or more of the PG loading step, the Al loading step, and the AE loading step.

[0172] The amount of the rare earth element to be loaded onto the first Zr-based oxide particles is adjusted so that the content of the rare earth element in terms of oxide in the composite produced in step (c) is within a desired range based on the mass of the composite.

[0173] The solvent used in the RE loading step is the same as the solvent used in the PG loading step.

[0174] Examples of the rare earth element source include rare earth element-containing compounds such as salts of rare earth elements, oxides of rare earth elements, and hydroxides of rare earth elements. One type of rare earth element source may be used alone, or two or more types of rare earth element sources may be used in combination.

[0175] The rare earth element source may be present in the solvent as it is, or may be present in the solvent in an ionized state.

[0176] Examples of the salts of rare earth elements include acetates, nitrates, chlorides, sulfates, etc.

[0177] The meaning of the oxides of rare earth elements is as described above.

[0178] The hydroxides of rare earth elements excluding Ce and Eu are M(OH) ３ [where M represents a rare earth element other than Ce and Eu.] And the Ce hydroxide is Ce(OH) ４ And the Eu hydroxide is Eu(OH) ２ And so on.

[0179] From the viewpoint of sufficiently dispersing the rare earth element source on the surface of the first Zr-based oxide, the rare earth element source is preferably a salt of a rare earth element, and the salt of the rare earth element is preferably water-soluble.

[0180] Examples of water-soluble salts of rare earth elements include acetates, nitrates, and sulfates.

[0181] In one embodiment of step (b), an Al source and an alkaline earth metal source are added to a solvent (preferably water, more preferably pure water such as deionized water), followed by the addition of a first Zr-based oxide particle, and then a platinum group element source and optionally a rare earth element source. The resulting mixture is then stirred to obtain an intermediate. In the addition of the Al source and the alkaline earth metal source, the Al source may be added before, after, or simultaneously with the alkaline earth metal source. In the addition of the platinum group element source and the rare earth element source, the platinum group element source may be added before, after, or simultaneously with the rare earth element source.

[0182] Step (b) produces a slurry containing an intermediate.

[0183] The intermediate contains first Zr-based oxide particles, Al, alkaline earth metal elements, platinum group elements, and optionally rare earth elements.

[0184] The following describes process (c).

[0185] The intermediate may be dried before calcining. When drying the intermediate, the drying temperature is, for example, 50°C to 300°C, preferably 70°C to 200°C, and the drying time is, for example, 3 minutes to 24 hours, preferably 5 minutes to 12 hours. Drying can be carried out, for example, in an atmospheric environment.

[0186] Before calcining the intermediate, the dried intermediate may be pulverized. Pulverization can be carried out dry or wet using, for example, a mortar and pestle, hammer mill, ball mill, bead mill, jet mill, roller mill, etc.

[0187] When firing the intermediate, the firing temperature is, for example, 400°C to 800°C, preferably 450°C to 600°C, and the firing time is, for example, 0.25 hours to 12 hours, preferably 0.5 hours to 8 hours. The firing can be carried out, for example, in an atmospheric environment.

[0188] The composite produced by step (c) comprises a second Zr-based oxide particle, an Al oxide independently of the second Zr-based oxide particle, an alkaline earth metal oxide independently of the second Zr-based oxide particle, a platinum group element, and optionally a rare earth oxide independently of the Zr-based oxide particle.

[0189] By calcining the intermediate, second Zr-based oxide particles are formed from first Zr-based oxide particles. By calcining the intermediate, some of the Al, some of the alkaline earth metal elements, and some of the rare earth elements can be dissolved in the first Zr-based oxide particles. By calcining the intermediate, Al oxides that exist independently of the second Zr-based oxide particles are formed from at least some of the Al, alkaline earth metal oxides that exist independently of the second Zr-based oxide particles are formed from at least some of the alkaline earth metal elements, and rare earth oxides that exist independently of the second Zr-based oxide particles are formed from at least some of the rare earth elements.

[0190] The description of this composite given in the section on "Compositions for Exhaust Gas Purification" also applies to the composite manufactured by process (c). The second Zr-based oxide particles correspond to the Zr-based oxide contained in this composite.

[0191] <<Exhaust Gas Purification Catalyst>> The exhaust gas purification catalyst of the present invention will be described below.

[0192] Hereinafter, an exhaust gas purification catalyst 1 (hereinafter sometimes referred to as "catalyst 1") according to one embodiment of the present invention will be described based on Figures 1 to 4.

[0193] As shown in Figure 1, the catalyst 1 is located in the exhaust passage within the exhaust pipe P of an internal combustion engine. The internal combustion engine is, for example, a gasoline engine. Exhaust gas discharged from the internal combustion engine flows through the exhaust passage within the exhaust pipe P from one end to the other and is purified by the catalyst 1 installed in the exhaust pipe P. In the drawings, the direction of exhaust gas flow is indicated by the symbol X. In this specification, the upstream side of the exhaust gas flow direction X may be referred to as the "exhaust gas inlet side" or "upstream side," and the downstream side of the exhaust gas flow direction X may be referred to as the "exhaust gas outlet side" or "downstream side."

[0194] Other exhaust gas purification catalysts may be placed in the exhaust passage within the exhaust pipe P, upstream and / or downstream of catalyst 1.

[0195] As shown in Figures 2 to 4, the catalyst 1 comprises a substrate 10 and a catalyst layer 20 provided on the substrate 10.

[0196] <Base Material> The base material 10 will be described below.

[0197] The material constituting the base material 10 can be appropriately selected from known materials. Examples of materials constituting the base material 10 include ceramic materials and metallic materials, but ceramic materials are preferred. Examples of ceramic materials include carbide ceramics such as silicon carbide, titanium carbide, tantalum carbide, and tungsten carbide; nitride ceramics such as aluminum nitride, silicon nitride, boron nitride, and titanium nitride; and oxide ceramics such as alumina, zirconia, cordierite, mullite, zircon, aluminum titanate, and magnesium titanate. Examples of metallic materials include alloys such as stainless steel.

[0198] As shown in Figures 2 to 4, the base material 10 has a cylindrical portion 11, a partition wall portion 12 provided inside the cylindrical portion 11, and cells 13 separated by the partition wall portion 12. The base material 10 is preferably a honeycomb structure.

[0199] As shown in Figure 2, the cylindrical portion 11 defines the outer shape of the base material 10, and the axial direction of the cylindrical portion 11 coincides with the axial direction of the base material 10. As shown in Figure 2, the shape of the cylindrical portion 11 is cylindrical, but it may also be other shapes such as an elliptical cylinder or a polygonal cylinder.

[0200] As shown in Figures 2-4, a partition wall 12 exists between adjacent cells 13, and adjacent cells 13 are separated by the partition wall 12. The partition wall 12 may have a porous structure through which exhaust gas can pass. The thickness of the partition wall 12 is, for example, 20 μm or more and 1500 μm or less.

[0201] As shown in Figure 4, cell 13 extends in the exhaust gas flow direction X and has an end on the exhaust gas inlet side and an end on the exhaust gas outlet side.

[0202] As shown in Figure 4, both the exhaust gas inlet and exhaust gas outlet ends of cell 13 are open. Therefore, exhaust gas flowing in from the exhaust gas inlet end (opening) of cell 13 flows out from the exhaust gas outlet end (opening) of cell 13. This type of configuration is called a flow-through type.

[0203] As shown in Figures 2 and 3, the plan view shape of the exhaust gas inlet end (opening) of cell 13 is a rectangle, but it may be a hexagon, octagon, or other shape. The same applies to the plan view shape of the exhaust gas outlet end (opening) of cell 13.

[0204] The cell density per square inch of the substrate 10 is, for example, 100 cells or more and 1000 cells or less. The cell density per square inch of the substrate 10 refers to the total number of cells 13 per square inch in a cross-section obtained by cutting the substrate 10 with a plane perpendicular to the exhaust gas flow direction X.

[0205] The volume of the base material 10 is, for example, 0.1 L or more and 20 L or less. The volume of the base material 10 refers to the apparent volume of the base material 10. For example, if the base material 10 is cylindrical, and the outer diameter of the base material 10 is 2r and the length of the base material 10 is L10, then the volume of the base material 10 is given by the formula: Volume of base material 10 = π × r ２ It is represented as ×L10. In this specification, "length" means the axial dimension of the base material 10.

[0206] <Catalyst Layer> The catalyst layer 20 will be described below.

[0207] As shown in Figures 3 and 4, the catalyst layer 20 is provided on the substrate 10. Specifically, the catalyst layer 20 is provided on the cell 13 side surface of the partition wall 12. The "cell 13 side surface of the partition wall 12" means the outer surface of the partition wall 12 that extends in the exhaust gas flow direction X. The catalyst layer 20 may be provided directly on the cell 13 side surface of the partition wall 12 or via another layer, but is usually provided directly on the cell 13 side surface of the partition wall 12. The "catalyst layer 20 provided on the substrate 10" includes both embodiments in which the catalyst layer 20 is provided directly on the cell 13 side surface of the partition wall 12 and embodiments in which the catalyst layer 20 is provided on the cell 13 side surface of the partition wall 12 via another layer.

[0208] The catalyst layer 20 may be composed of a portion that rises from the cell 13 side surface of the partition wall portion 12 toward the cell 13 (hereinafter referred to as the "raised portion"), or it may be composed of a portion that exists inside the partition wall portion 12 (hereinafter referred to as the "internal portion"), or it may have both a raised portion and an internal portion. The "catalyst layer 20 provided on the substrate 10" includes any embodiment in which the catalyst layer 20 is composed of a raised portion, an embodiment in which the catalyst layer 20 is composed of an internal portion, and an embodiment in which the catalyst layer 20 has both a raised portion and an internal portion.

[0209] As shown in Figure 4, the catalyst layer 20 extends along the exhaust gas flow direction X from the exhaust gas inlet end of the partition wall 12 to the exhaust gas outlet end of the partition wall 12. The catalyst layer 20 may extend along the exhaust gas flow direction X from the exhaust gas inlet end of the partition wall 12 so as not to reach the exhaust gas outlet end of the partition wall 12, or it may extend along the direction opposite to the exhaust gas flow direction X from the exhaust gas outlet end of the partition wall 12 so as not to reach the exhaust gas inlet end of the partition wall 12.

[0210] From the viewpoint of achieving a good balance between exhaust gas purification performance and suppression of pressure loss, the mass of the catalyst layer 20 per unit volume of the portion of the substrate 10 on which the catalyst layer 20 is formed (hereinafter referred to as "WC amount of catalyst layer 20") is preferably 20 g / L or more and 250 g / L or less, more preferably 40 g / L or more and 200 g / L or less, and even more preferably 60 g / L or more and 150 g / L or less. Each of the above lower limits may be combined with any of the above upper limits.

[0211] The amount of WC in the catalyst layer 20 is calculated by the formula: (mass of catalyst layer 20) / (volume of substrate 10) × (length L of catalyst layer 20) ２０ Length L of base material 10 １０ It is calculated from ).

[0212] Length L of the catalyst layer 20 ２０ An example of the measurement method is as follows:

[0213] The catalyst 1 extends in the axial direction of the substrate 10, and the length L of the substrate 10 is... １０ A sample having the same length as the sample is cut out. The sample is, for example, cylindrical with a diameter of 25.4 mm. The diameter of the sample can be changed as needed. If the catalyst layer 20 extends from the exhaust gas inlet end of the partition wall 12 along the exhaust gas flow direction X, the sample is cut at 5 mm intervals by a plane perpendicular to the axial direction of the base material 10, and the first cut piece, second cut piece, ..., nth cut piece are obtained in order from the exhaust gas inlet end of the sample. If the catalyst layer 20 extends from the exhaust gas outlet end of the partition wall 12 along the direction opposite to the exhaust gas flow direction X, the sample is cut at 5 mm intervals by a plane perpendicular to the axial direction of the base material 10, and the first cut piece, second cut piece, ..., nth cut piece are obtained in order from the exhaust gas outlet end of the sample. The length of the cut piece is 5 mm. The composition of the slicing piece is analyzed using XRF (e.g., EDX, WDX, etc.), ICP-AES, SEM-EDX, etc., and based on the composition of the slicing piece, it is confirmed whether or not the slicing piece contains a portion of the catalyst layer 20.

[0214] Regarding a cut piece that clearly includes a part of the catalyst layer 20, it is not always necessary to perform a compositional analysis. For example, SEM, EPMA, etc. can be used to observe the cut surface to confirm whether the cut piece includes a part of the catalyst layer 20. When observing the cut surface, elemental mapping of the cut surface may be performed.

[0215] After confirming whether the cut piece includes a part of the catalyst layer 20, based on the following formula, calculate the length of the catalyst layer 20 included in the sample. Length of the catalyst layer 20 included in the sample = 5 mm × (number of cut pieces including a part of the catalyst layer 20)

[0216] For example, when the first cut piece to the k-th cut piece include a part of the catalyst layer 20, but the (k + 1)-th to the n-th cut pieces do not include a part of the catalyst layer 20, the length of the catalyst layer 20 included in the sample is (5 × k) mm.

[0217] An example of a more detailed measurement method for the length of the catalyst layer 20 included in the sample is as follows. The k-th cut piece (when the catalyst layer 20 extends along the exhaust gas flow direction X from the end on the exhaust gas inflow side of the partition portion 12, the k-th cut piece is the cut piece obtained from the most exhaust gas outflow side of the sample among the cut pieces including a part of the catalyst layer 20. When the catalyst layer 20 extends along the direction opposite to the exhaust gas flow direction X from the end on the exhaust gas outflow side of the partition portion 12, the k-th cut piece is the cut piece obtained from the most exhaust gas inflow side of the sample among the cut pieces including a part of the catalyst layer 20.) is cut in the axial direction of the base material 10, and by observing a part of the catalyst layer 20 present on the cut surface using SEM, EPMA, etc., measure the length of a part of the catalyst layer 20 in the k-th cut piece. Then, based on the following formula, calculate the length of the catalyst layer 20 included in the sample. Length of the catalyst layer 20 included in the sample = (5 mm × (k - 1)) + (length of a part of the catalyst layer 20 included in the k-th cut piece)

[0218] The length of the catalyst layer 20 included in one sample may be adopted as the length L of the catalyst layer 20 ２０ or the average value of the lengths of the catalyst layer 20 included in a plurality of samples may be adopted as the length L of the catalyst layer 20 ２０It may be adopted as such, but the latter is preferred. In the latter case, for example, 8 to 16 samples are arbitrarily cut out from catalyst 1, the length of the catalyst layer 20 contained in each sample is measured, and the average value of these is the length L of the catalyst layer 20. ２０ It may be adopted as such.

[0219] The catalyst layer 20 is composed of this catalyst composition.

[0220] <Manufacturing of Catalyst> Catalyst 1 can be manufactured by forming a catalyst layer 20 on a substrate 10.

[0221] The catalyst layer 20 can be formed by applying a slurry containing the intermediate obtained in step (b) of this manufacturing method onto the substrate 10, drying it, and firing it. Drying and firing can be carried out in the same manner as in step (c) of this manufacturing method.

[0222] <Example 1> In a stirring container containing pure water, barium acetate, alumina sol (average particle size: 5 nm), and Zr-based oxide powder (zirconium oxide powder, crystal structure: monoclinic, specific surface area: 110 m²) were added. ２ / g, Zr of ZrO ２ The converted content was approximately 100% by mass (>99.5% by mass), with an average particle size of 3 μm. Rhodium nitrate aqueous solution was added sequentially and thoroughly stirred to obtain a slurry. The composition of the slurry (based on the total mass of solids) was Al ２ O ３ Conversion content: 5.0 mass%, Ba content in BaO equivalent: 1.0 mass%, Rh content in metal equivalent: 0.50 mass%, Zr content in ZrO ２ The converted content was adjusted to the remainder. The slurry was transferred to an evaporating dish and dried at 120°C for 12 hours, and the dried material was ground in a mortar. The ground material was calcined at 500°C for 1 hour in an air atmosphere to obtain a powdered catalyst composition (hereinafter referred to as "the catalyst composition of Example 1").

[0223] <Example 2> The composition of the slurry (based on the total mass of solids) is Al ２ O ３ Conversion content: 5.0 mass%, Ba content in BaO equivalent: 2.0 mass%, Rh content in metal equivalent: 0.50 mass%, Zr content in ZrO ２A powdered catalyst composition (hereinafter referred to as "the catalyst composition of Example 2") was obtained in the same manner as in Example 1, except that the content was adjusted to be the remainder.

[0224] <Example 3> A powdered catalyst composition (hereinafter referred to as "the catalyst composition of Example 3") was obtained in the same manner as in Example 2, except that aluminum nitrate was added instead of alumina sol.

[0225] <Example 4> The composition of the slurry (based on the total mass of solids) is Al ２ O ３ Conversion content: 5.0 mass%, Ba content in BaO equivalent: 5.0 mass%, Rh content in metal equivalent: 0.50 mass%, Zr content in ZrO ２ A powdered catalyst composition (hereinafter referred to as "the catalyst composition of Example 4") was obtained in the same manner as in Example 1, except that the content was adjusted to be the remainder.

[0226] <Example 5> In a stirring container containing pure water, barium acetate, alumina sol, Zr-based oxide powder, rhodium nitrate aqueous solution, and yttrium acetate were added in order and thoroughly stirred to obtain a slurry. Furthermore, the composition of the slurry (based on the total mass of solids) was described as Al's Al ２ O ３ Conversion content: 5.0 mass%, Ba content in BaO equivalent: 2.0 mass%, Rh content in metal equivalent: 0.50 mass%, Y content ２ O ３ Converted content: 2.0% by mass, Zr of ZrO ２ A powdered catalyst composition (hereinafter referred to as "the catalyst composition of Example 5") was obtained in the same manner as in Example 1, except that the content was adjusted to be the remainder.

[0227] <Example 6> The difference is that praseodymium acetate was added instead of yttrium acetate, and the composition of the slurry (based on the total mass of solids) was changed to Al ２ O ３ Conversion content: 5.0 mass%, Ba content in BaO equivalent: 2.0 mass%, Rh content in metal equivalent: 0.50 mass%, Pr content ６ O １１ Converted content: 2.0% by mass, Zr of ZrO ２A powdered catalyst composition (hereinafter referred to as "the catalyst composition of Example 6") was obtained in the same manner as in Example 5, except that the content was adjusted to be the remainder.

[0228] <Example 7> The difference is that neodymium acetate was added instead of yttrium acetate, and the composition of the slurry (based on the total mass of solids) was changed to Al ２ O ３ Conversion content: 5.0 mass%, Ba content in BaO equivalent: 2.0 mass%, Rh content in metal equivalent: 0.50 mass%, Nd content ２ O ３ Converted content: 2.0% by mass, Zr of ZrO ２ A powdered catalyst composition (hereinafter referred to as "the catalyst composition of Example 7") was obtained in the same manner as in Example 5, except that the content was adjusted to be the remainder.

[0229] <Example 8> The difference is that lanthanum acetate was added instead of yttrium acetate, and the composition of the slurry (based on the total mass of solids) was changed to Al ２ O ３ Conversion content: 5.0 mass%, Ba content in BaO equivalent: 2.0 mass%, Rh content in metal equivalent: 0.50 mass%, La content ２ O ３ Conversion content: 0.1% by mass, Zr of ZrO ２ A powdered catalyst composition (hereinafter referred to as "the catalyst composition of Example 8") was obtained in the same manner as in Example 5, except that the content was adjusted to be the remainder.

[0230] <Example 9> The composition of the slurry (based on the total mass of solids) is Al ２ O ３ Conversion content: 5.0 mass%, Ba content in BaO equivalent: 2.0 mass%, Rh content in metal equivalent: 0.50 mass%, La content ２ O ３ Converted content: 1.0 mass%, ZrO ２ A powdered catalyst composition (hereinafter referred to as "the catalyst composition of Example 9") was obtained in the same manner as in Example 8, except that the content was adjusted to be the remainder.

[0231] <Example 10> The composition of the slurry (based on the total mass of solids) is Al ２ O ３ Conversion content: 5.0 mass%, Ba content in BaO equivalent: 2.0 mass%, Rh content in metal equivalent: 0.50 mass%, La content ２ O ３ Converted content: 2.0% by mass, Zr of ZrO ２ A powdered catalyst composition (hereinafter referred to as "the catalyst composition of Example 10") was obtained in the same manner as in Example 8, except that the content was adjusted to be the remainder.

[0232] <Example 11> The composition of the slurry (based on the total mass of solids) is Al ２ O ３ Conversion content: 5.0 mass%, Ba content in BaO equivalent: 2.0 mass%, Rh content in metal equivalent: 0.50 mass%, La content ２ O ３ Converted content: 8.0% by mass, Zr of ZrO ２ A powdered catalyst composition (hereinafter referred to as "the catalyst composition of Example 11") was obtained in the same manner as in Example 8, except that the content was adjusted to be the remainder.

[0233] <Comparative Example 1> The differences are that zirconia sol was added instead of alumina sol, barium acetate was not added, and the composition of the slurry (based on the total mass of solids) was: Rh content in metal equivalent: 0.50% by mass, Zr derived from zirconia sol ZrO ２ Converted content: 5.0% by mass, Zr derived from Zr-based oxide powder ２ A powdered catalyst composition (hereinafter referred to as "Comparative Example 1 catalyst composition") was obtained in the same manner as in Example 1, except that the content was adjusted to be the remainder.

[0234] <Comparative Example 2> Barium acetate was not added, and the composition of the slurry (based on the total mass of solids) was as follows: Rh content in metal equivalent: 0.50% by mass, Al content: Al ２ O ３ Converted content: 5.0% by mass, Zr of ZrO ２A powdered catalyst composition (hereinafter referred to as "Comparative Example 2 catalyst composition") was obtained in the same manner as in Example 1, except that the content was adjusted to be the remainder.

[0235] <Comparative Example 3> Zr-Nd composite oxide powder (crystal structure: cubic, specific surface area: 74 m²) is used instead of zirconia oxide powder as the Zr-based oxide powder. ２ / g, Zr of ZrO ２ Conversion content: 90% by mass, Nd of Nd ２ O ３ The added content (converted to 10% by mass) and the composition of the slurry (based on the total mass of solids) were: Rh content (metal equivalent): 0.50% by mass, Al content: Al ２ O ３ Conversion content: 5.0% by mass, Nd of Nd ２ O ３ Converted content: 9.5% by mass, Zr of ZrO ２ A powdered catalyst composition (hereinafter referred to as "the catalyst composition of Comparative Example 3") was obtained in the same manner as in Comparative Example 2, except that the content was adjusted to be the remainder.

[0236] <Comparative Example 4> Zr-Nd composite oxide powder (crystal structure: cubic, specific surface area: 74 m²) is used instead of zirconia oxide powder as the Zr-based oxide powder. ２ / g, Zr of ZrO ２ Conversion content: 90% by mass, Nd of Nd ２ O ３ The added content (converted to 10% by mass) of Rh was 0.50% by mass, the content of Ba (converted to BaO) was 2.0% by mass, and the content of Al was Al ２ O ３ Conversion content: 5.0% by mass, Nd of Nd ２ O ３ Converted content: 9.3% by mass, Zr of ZrO ２ A powdered catalyst composition (hereinafter referred to as "Comparative Example 4 catalyst composition") was obtained in the same manner as in Example 2, except that the content was adjusted to be the remainder.

[0237] <Comparative Example 5> Barium nitrate, aluminum nitrate, zirconium oxynitrate, and lanthanum nitrate were added in order to a stirring vessel containing pure water, and the mixture was stirred thoroughly at room temperature to dissolve them. The resulting aqueous solution was added dropwise to an excess amount of basic ammonium oxalate solution (pH: 10.2) to obtain a slurry containing a white precipitate. The obtained slurry was filtered and thoroughly washed with pure water to obtain a cake layer. The obtained cake layer was dried at 120°C, then crushed in a mortar, and calcined at 500°C for 1 hour under an air atmosphere to obtain the composite oxide of Comparative Example 5. The composite oxide of Comparative Example 5 was in an amorphous state. The composition of the composite oxide of Comparative Example 5 (based on the mass of the composite) was: Ba content in terms of BaO: 2.0% by weight, Al content: Al ２ O ３ Conversion content: 5.0% by weight, La of La ２ O ３ Conversion content: 1.0% by weight, Zr of ZrO ２ The converted content was: the remainder.

[0238] The above-mentioned composite oxide and rhodium nitrate aqueous solution were added sequentially to a stirring vessel containing pure water and stirred thoroughly to obtain a slurry. The composition of the slurry (based on the total mass of solids) was adjusted so that the Rh content (on a metal basis) was 0.50% by mass and the composite oxide content was the remainder. Using the obtained slurry, a powdered catalyst composition (hereinafter referred to as "comparative example 5 catalyst composition") was obtained in the same manner as in Example 1.

[0239] <Comparative Example 6> The composition of the slurry (based on the total mass of solids) is Al ２ O ３ Conversion content: 5.0 mass%, Ba content in BaO equivalent: 10.0 mass%, Rh content in metal equivalent: 0.50 mass%, Zr content in ZrO ２ A powdered catalyst composition (hereinafter referred to as "Comparative Example 6 catalyst composition") was obtained in the same manner as in Example 1, except that the content was adjusted to be the remainder.

[0240] <Example 12> In a stirring container containing pure water, barium acetate, alumina sol, and aluminum oxide powder (average particle size: 8 μm, Al of Al) were added. ２ O ３The converted content was approximately 100% by mass (>99.5% by mass), with Zr-based oxide powder and rhodium nitrate aqueous solution added in sequence, and the composition of the slurry (based on the total mass of solids) was determined to be Al derived from aluminum oxide powder. ２ O ３ Converted content: 5.0% by mass, Al derived from alumina sol ２ O ３ Conversion content: 5.0 mass%, Ba content in BaO equivalent: 2.0 mass%, Rh content in metal equivalent: 0.50 mass%, Zr content in ZrO ２ A powdered catalyst composition (hereinafter referred to as "the catalyst composition of Example 12") was obtained in the same manner as in Example 1, except that the content was adjusted to be the remainder.

[0241] <Comparative Example 7> In contrast to the absence of barium acetate, the composition of the slurry (based on the total mass of solids) was determined by the amount of Al derived from aluminum oxide powder. ２ O ３ Converted content: 5.0% by mass, Al derived from alumina sol ２ O ３ Conversion content: 5.0 mass%, Rh content in metal equivalent: 0.50 mass%, Zr content: ZrO ２ A powdered catalyst composition (hereinafter referred to as "the catalyst composition of Comparative Example 7") was obtained in the same manner as in Example 12, except that the content was adjusted to be the remainder.

[0242] <Comparative Example 8> In comparison with the absence of alumina sol, the composition of the slurry (based on the total mass of solids) was determined by the amount of Al derived from aluminum oxide powder. ２ O ３ Conversion content: 5.0 mass%, Ba content in BaO equivalent: 5.0 mass%, Rh content in metal equivalent: 0.50 mass%, Zr content in ZrO ２ A powdered catalyst composition (hereinafter referred to as "the catalyst composition of Comparative Example 8") was obtained in the same manner as in Example 12, except that the content was adjusted to be the remainder.

[0243] <Comparative Example 9> In this example, alumina sol and barium acetate were not added, and the composition of the slurry (based on the total mass of solids) was determined by the amount of Al derived from aluminum oxide powder. ２ O ３ Conversion content: 5.0 mass%, Rh content in metal equivalent: 0.50 mass%, Zr content: ZrO ２ A powdered catalyst composition (hereinafter referred to as "the catalyst composition of Comparative Example 9") was obtained in the same manner as in Example 12, except that the content was adjusted to be the remainder.

[0244] <Test Examples> (1) Heat treatment of catalysts For the catalyst compositions of Examples 1 to 12 and Comparative Examples 1 to 9, a quartz tubular furnace was used to heat them. ２ Gas: 0.50 vol%, Propylene: 0.11 vol%, Water vapor: 10 vol% and N ２ Gas: The remaining material was subjected to heat treatment at 1000°C for 10 hours in an atmosphere through which the gas was circulated.

[0245] (2) Measurement of specific surface area The specific surface area of ​​the catalyst compositions of Examples 1 to 12 and Comparative Examples 1 to 9 after heat treatment was measured according to the "(3.5) Multi-point method" in "6.1 Quantitative method" of JIS R1626:1996 "Method for measuring the specific surface area of ​​fine ceramic powder by gas adsorption BET method". Nitrogen was used as the adsorption gas, and five measurements were taken within the equilibrium relative pressure range of 0.05 to 0.35. A BELSORP-miniX manufactured by Microtrac-Bell was used as the measuring device.

[0246] (3) Powder X-ray diffraction measurement The catalyst compositions of Examples 1 to 12 and Comparative Examples 1 to 9 were analyzed by powder X-ray diffraction before and after heat treatment to obtain powder X-ray diffraction patterns. The powder X-ray diffraction method was performed under the following conditions. Figure 5 shows the powder X-ray diffraction patterns of the catalyst compositions of Examples 2 and 9 and Comparative Examples 1 to 3 and 5 after heat treatment. <Conditions for powder X-ray diffraction> Powder X-ray diffractometer: MiniFlex 600 (manufactured by Rigaku Corporation) X-ray source: CuKα Operating axis: 2θ / θ Measurement method: Continuous Counting unit: cps Starting angle: 5° Ending angle: 90° Sampling width: 0.02° Scan speed: 10° / min Voltage: 40kV Current: 150mA

[0247] I in each powder X-ray diffraction pattern Ａ / I Ｂ The value of I was calculated. Ａ This represents the integrated intensity of the peak located between 2θ = 27.0° and 29.0°, and I Ｂ This represents the integrated intensity of the peak located between 2θ = 29.0 and 30.8°. The detection and integrated intensity of each peak were obtained by using the integrated powder X-ray diffraction software PDXL (manufactured by Rigaku Corporation). After removing the background intensity from the powder X-ray diffraction pattern, peak fitting (peak separation) was performed using a pseudo-Voigt function, the area of ​​each separated peak was calculated, and the calculated area of ​​each peak was taken as the integrated intensity of each peak.

[0248] (4) Evaluation of exhaust gas purification performance (T50) In each of the examples from 1 to 12, a ceramic honeycomb substrate was immersed in the slurry obtained in each example, and excess slurry was removed using an air blower to coat the ceramic honeycomb substrate with the slurry. The ceramic honeycomb substrate coated with the slurry was dried at 120°C for 10 minutes, and then fired at 500°C for 1 hour in an air atmosphere to obtain a catalyst comprising a ceramic honeycomb substrate and a catalyst layer formed on the ceramic honeycomb substrate. The amount of catalyst layer formed on the ceramic honeycomb substrate was 100 g / L in all cases. "Amount of catalyst layer formed on the ceramic honeycomb substrate" means the mass of the catalyst layer per unit volume of the portion of the substrate on which the catalyst layer is formed.

[0249] Each of the obtained catalysts was subjected to the same heat treatment as in (1). After heat treatment, each catalyst was placed in the exhaust passage, and the exhaust model gas (CO 0.30 vol%, O ２ 0.28vol%, NO 500volppm, C ３ H ６ 1000volppm, CO ２ 14 vol%, H ２ O 10 vol%, N ２The remaining material was circulated at a space velocity of 60,000 / h while the temperature was increased to 500°C at a rate of 20°C / min. The nitrogen oxide (NOx) purification rate was continuously measured, and the temperature at which the nitrogen oxide (NOx) purification rate reached 50% (light-off temperature T50) (°C) was determined. The light-off temperature T50 was determined during the heating process.

[0250] The results of Examples 1 to 12, Comparative Examples 1 to 9, and the test examples are shown in Tables 1A, 1B, 2, and 3.

[0251]

[0252]

[0253]

[0254]

[0255] P... Exhaust pipe of an internal combustion engine 1... Catalyst for exhaust gas purification 10... Base material 11... Cylindrical section 12... Partition section 13... Cell 20... Catalyst layer

Claims

1. An exhaust gas purification catalyst composition comprising a composite containing a Zr-based oxide, an Al oxide independently present from the Zr-based oxide, an alkaline earth metal oxide independently present from the Zr-based oxide, and a platinum group element, wherein the content of Al in the composite on an oxide basis is 1% by mass or more and 15% by mass or less based on the mass of the composite, and the content of the alkaline earth metal element in the composite on an oxide basis is 0.1% by mass or more and 7% by mass or less based on the mass of the composite, and the X-ray diffraction pattern of the exhaust gas purification catalyst composition obtained by performing an X-ray diffraction method after heat treatment of the exhaust gas purification catalyst composition at 1000°C for 10 hours is given by the following formula (1): 1 ≤ I Ａ / I Ｂ ...(1) [wherein, I Ａ This represents the integrated intensity of the peak located between 2θ = 27.0° and 29.0°, and I Ｂ This represents the integrated intensity of the peak located at 2θ = 29.0° to 30.8°. The exhaust gas purification catalyst composition that satisfies the following conditions.

2. The exhaust gas purification catalyst composition according to claim 1, wherein the complex further comprises a rare earth oxide that exists independently of the Zr-based oxide.

3. The exhaust gas purification catalyst composition according to claim 2, wherein the content of rare earth elements in the composite, in terms of oxides, is 0.1% by mass or more and 5% by mass or less, based on the mass of the composite.

4. The exhaust gas purification catalyst composition according to claim 2, wherein the rare earth oxide is composed of one or more selected from the group consisting of La oxide, Nd oxide, Pr oxide, and Y oxide.

5. The exhaust gas purification catalyst composition according to claim 4, wherein the rare earth oxide is composed of one or more selected from the group consisting of La oxide, Nd oxide, and Pr oxide.

6. The exhaust gas purification catalyst composition according to claim 5, wherein the rare earth oxide is composed of La oxide.

7. The exhaust gas purification catalyst composition according to claim 1, wherein the alkaline earth metal oxide is composed of a Ba oxide.

8. The exhaust gas purification catalyst composition according to claim 1, wherein the platinum group element is composed of Rh.

9. An exhaust gas purification catalyst comprising a base material and a catalyst layer provided on the base material, wherein the catalyst layer is composed of the exhaust gas purification catalyst composition described in any one of claims 1 to 8.

10. A method for producing an exhaust gas purification catalyst composition, comprising the following steps: (a) preparing first Zr-based oxide particles having a monoclinic crystal structure; (b) supporting Al, an alkaline earth metal element, a platinum group element, and optionally a rare earth element on the first Zr-based oxide particles to produce an intermediate; and (c) calcining the intermediate to produce a composite comprising second Zr-based oxide particles, an Al oxide independently of the second Zr-based oxide particles, an alkaline earth metal oxide independently of the second Zr-based oxide particles, a platinum group element, and optionally a rare earth oxide independently of the Zr-based oxide particles.

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