Exhaust gas purification catalyst device

Abstract

To provide an exhaust gas purification catalyst device that reduces HC emissions in cold regions as well as NOx emissions in cold regions.SOLUTION: Disclosed is an exhaust gas purification catalyst device which has a base material and a catalyst coating layer disposed on the base material, wherein: the catalyst coating layer is a single layer or a multilayer body that is composed of two or more layers; the uppermost layer of the catalyst coating layer has an upper layer first zone that contains Pd, an upper layer second zone that contains Rh, and an upper layer third zone that contains Rh in this order from the upstream side of the exhaust gas flow; and the Rh concentration in the upper layer second zone is higher than the Rh concentration in the upper layer third zone.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Nitrogen oxides (NO x These exhaust gases contain NOx, carbon monoxide (CO), hydrocarbons (HC), etc. These exhaust gases are purified by an exhaust gas purification catalyst that oxidizes CO and HC and reduces NOx before being released into the atmosphere.

[0003] With a view to reducing air pollution, each country regulates the weight of components contained in exhaust gases emitted per unit distance traveled by automobiles. These exhaust gas regulations are becoming stricter every year. Currently, the United States is subject to LEV III regulations, Europe to Euro 6 regulations, and China to Country 6 regulations, but it is expected that these will be replaced by LEV IV regulations, Euro 7 regulations, and Country 7 regulations, respectively, in the near future.

[0004] The Euro 7 regulations require a reduction in NOx emissions in the cold region, for example, during engine start-up. The exhaust gas atmosphere during engine start-up is in the rich to stoichiometric region. Therefore, it is difficult to reduce NOx emissions in the cold region using conventional NOx purification technologies that are based on lean-burn engines.

[0005] As a conventional NOx emission reduction technology, for example, Patent Document 1 discloses: a lower catalyst layer containing a first composite oxide containing Ce and Zr and Pd supported on the first composite oxide; and an upper catalyst layer containing a second composite oxide containing Ce and Zr and Rh supported on the second composite oxide; and an alkaline earth metal selected from Ca, Sr, and Mg is dissolved in at least one of the first composite oxide and the second composite oxide.

[0006] Furthermore, Patent Document 2 describes an oxidation-reduction catalyst in which palladium and an alkaline earth metal are supported on an oxide having oxygen storage and release capacity. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-119994 [Patent Document 2] Japanese Patent Application Laid-Open No. 2001-198461 Summary of the Invention [Problem to be solved by the invention]

[0008] The above-mentioned Patent Documents 1 and 2 both belong to the category of prior art exhaust gas purification catalysts, and are insufficient in reducing NOx emissions in the cold region, such as at engine start-up.

[0009] The present invention has been made in view of the above circumstances, and has as its object to provide an exhaust gas purification catalyst device that reduces NOx emissions in the cold region as well as HC emissions in the cold region. [Means for solving the problem]

[0010] The present invention is as follows.

[0011] Aspect 1: An exhaust gas purification catalyst device having a substrate and a catalyst coating layer on the substrate, the catalyst coating layer is a single layer or a laminate consisting of two or more layers, the uppermost layer of the catalyst coating layer has, from the upstream side of the exhaust gas flow, an upper layer first zone containing Pd, an upper layer second zone containing Rh, and an upper layer third zone containing Rh, in this order; the Rh concentration in the upper second zone is higher than the Rh concentration in the upper third zone; Exhaust gas purification catalytic device. Aspect 2: The Rh concentration in the upper second zone is 0.20 g / L or more and 0.50 g / L or less in terms of metal, and the Rh concentration in the upper third zone in terms of metal is 0.05 g / L or more and less than 0.20 g / L; 2. The catalytic converter for exhaust gas purification according to claim 1. Aspect 3: The catalytic device for purifying exhaust gas according to aspect 1, wherein the Rh concentration in the upper second zone is 1.5 to 4.0 times the Rh concentration in the upper third zone. Aspect 4: The catalytic device for purifying exhaust gas according to Aspect 1, wherein the concentration of elemental Ce in the upper second zone is lower than the concentration of elemental Ce in the upper third zone. Aspect 5: The concentration of Ce element in terms of ceria in the upper second zone is 7.0 g / L or less, and The concentration of Ce element in terms of ceria in the upper third zone is 5.0 g / L or more and 15.0 g / L or less. 2. The catalytic converter for exhaust gas purification according to claim 1. Aspect 6: The concentration of Ce element in terms of ceria in the upper second zone is 7.0 g / L or less, and The concentration of Ce element in terms of ceria in the upper third zone is 5.0 g / L or more and 15.0 g / L or less. 3. The catalytic converter for exhaust gas purification according to claim 2. Aspect 7: The concentration of Ce element in terms of ceria in the upper second zone is 7.0 g / L or less, and The concentration of Ce element in terms of ceria in the upper third zone is 5.0 g / L or more and 15.0 g / L or less. A catalytic converter for exhaust gas purification according to aspect 3. Aspect 8: At least a portion of the Rh contained in the upper second zone is supported on inorganic oxide particles containing Ce element, and the Rh contained in the upper third zone is supported on inorganic oxide particles containing Ce element; A catalytic device for purifying exhaust gas according to any one of aspects 1 to 7. Aspect 9: At least a portion of the Rh contained in the upper second zone is supported on inorganic oxide particles that are substantially free of Ce element, and the Rh contained in the upper third zone is supported on inorganic oxide particles containing Ce element; A catalytic device for purifying exhaust gas according to any one of aspects 1 to 7. Aspect 10: At least a portion of the Rh contained in the upper second zone is supported on inorganic oxide particles that are substantially free of Ce element, the upper second zone further contains inorganic oxide particles containing Ce element, and the Rh contained in the upper third zone is supported on inorganic oxide particles containing Ce element; A catalytic device for purifying exhaust gas according to any one of aspects 1 to 7. <Embodiment 11> The catalyst coating layer is a laminate consisting of two layers, The lower layer of the catalyst coating layer is, from the upstream side of the exhaust gas flow, The lower first zone containing Rh, and a lower second zone containing one or two elements selected from Pd and Pt; in that order, A catalytic device for purifying exhaust gas according to any one of aspects 1 to 7. Aspect 12: The catalytic device for purifying exhaust gas according to Aspect 11, wherein the Rh concentration in the upper second zone is substantially the same as the Rh concentration in the lower first zone. Aspect 13: A method for purifying exhaust gas, comprising: disposing an exhaust gas purification catalyst device according to any one of aspects 1 to 7 in an exhaust system of an internal combustion engine, with the upper first zone facing upstream in the exhaust gas flow, and purifying exhaust gas emitted from the internal combustion engine. [Effects of the Invention]

[0012] According to the present invention, there is provided an exhaust gas purification catalyst device that reduces NOx emissions in the cold region as well as HC emissions in the cold region. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a schematic diagram showing the configuration of the exhaust gas purification catalyst device produced in Example 1. As shown in FIG. [Figure 2]FIG. 2 is a schematic diagram showing the configuration of the exhaust gas purification catalyst device produced in Example 2. [Figure 3] FIG. 3 is a schematic diagram showing the configuration of the exhaust gas purification catalyst device produced in Example 3. [Figure 4] FIG. 4 is a schematic diagram showing the configuration of the exhaust gas purification catalyst device produced in Example 4. [Figure 5] FIG. 5 is a schematic diagram showing the configuration of the exhaust gas purification catalyst device produced in Example 5. [Figure 6] FIG. 6 is a schematic diagram showing the configuration of the exhaust gas purification catalyst device produced in Example 6. [Figure 7] FIG. 7 is a schematic diagram showing the configuration of the exhaust gas purification catalyst device produced in Example 7. [Figure 8] FIG. 8 is a schematic diagram showing the configuration of the exhaust gas purification catalyst device produced in Comparative Example 1. As shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0014] <Exhaust gas purification catalyst device> The exhaust gas purification catalyst device of the present invention comprises: An exhaust gas purification catalyst device having a substrate and a catalyst coating layer on the substrate, the catalyst coating layer is a single layer or a laminate consisting of two or more layers, the uppermost layer of the catalyst coating layer has, from the upstream side of the exhaust gas flow, an upper layer first zone containing Pd, an upper layer second zone containing Rh, and an upper layer third zone containing Rh, in this order; the Rh concentration in the upper second zone is higher than the Rh concentration in the upper third zone; It is an exhaust gas purification catalytic device.

[0015] In the exhaust gas purification catalyst device of the present invention, the uppermost layer of the catalyst coating layer has, from the upstream side of the exhaust gas flow, an upper layer first zone containing Pd, an upper layer second zone containing Rh, and an upper layer third zone containing Rh, in this order, and the Rh concentration in the upper layer second zone is set higher than the Rh concentration in the upper layer third zone.

[0016] In the exhaust gas purification catalyst device of the present invention, the upper layer first zone, which is the most upstream of the uppermost layer, contains Pd, thereby enhancing the HC purification capacity in the cold region. Furthermore, the upper layer second zone and upper layer third zone, which are located downstream of the first zone, contain Rh, which thoroughly purifies HC.

[0017] In the exhaust gas purification catalyst device of the present invention, the high concentration of Rh contained in the upper second zone increases the NOx purification ability in the cold region. Furthermore, an upper third zone containing Rh is also arranged downstream of the upper second zone to capture and purify NOx that passes through the upper second zone in the high-speed region. Here, since most of the NOx is purified in the upper second zone, the Rh concentration in the upper third zone can be low.

[0018] In the exhaust gas purification catalyst device of the present invention, the amount of catalytic precious metal used is suppressed by the above-mentioned mechanism of action, and at the same time, NOx emissions in the cold region as well as HC emissions in the cold region are reduced.

[0019] However, the present invention is not bound by any particular theory.

[0020] In a preferred embodiment of the exhaust gas purification catalyst device of the present invention, the catalyst coating layer is a laminate consisting of two layers, and the lower layer of the catalyst coating layer may have, from the upstream side of the exhaust gas flow, a lower layer first zone containing Rh, and a lower layer second zone containing one or two species selected from Pd and Pt, in this order.

[0021] The components of the exhaust gas purification catalyst device of the present invention will be described below in order.

[0022] <Base material> The substrate in the catalytic converter for exhaust gas purification of the present invention may be a substrate having a plurality of cell flow paths separated by partition walls, or may be a honeycomb substrate used in conventional catalytic converters for exhaust gas purification. The partition walls of the substrate may or may not have pores that fluidly connect adjacent exhaust gas flow paths.

[0023] The constituent material of the substrate may be, for example, a refractory inorganic oxide such as cordierite, or may be a metal. The substrate may be of either a straight flow type or a wall flow type.

[0024] The substrate in the exhaust gas purification catalyst device of the present invention may typically be, for example, a straight-flow type monolith honeycomb substrate made of cordierite, a wall-flow type monolith honeycomb substrate made of cordierite, or a metal honeycomb substrate.

[0025] The shape of the substrate may be a cylinder, an elliptical cylinder, a polygonal pillar, or the like.

[0026] The capacity of the substrate, as an apparent volume expressed as the base area x length, may be, for example, 500 mL or more, 800 mL or more, 1.0 L or more, or 1.2 L or more, and may be, for example, 5.0 L or less, 3.0 L or less, 2.0 L or less, 1.5 L or less, or 1.2 L or less.

[0027] <Catalyst Coating Layer> The exhaust gas purification catalyst device of the present invention has a catalyst coating layer on a substrate.

[0028] The catalyst coating layer in the catalytic device for purifying exhaust gas of the present invention may be a single layer or a laminate consisting of two or more layers.

[0029] (Top layer) The uppermost layer of the catalyst coating layer in the exhaust gas purification catalytic device has, from the upstream side of the exhaust gas flow, an upper layer first zone containing Pd, an upper layer second zone containing Rh, and an upper layer third zone containing Rh, in this order.

[0030] The "top layer" of the catalyst coating layer means the single layer if the catalyst coating layer is a single layer, or means the layer that is located farthest from the cell flow path surface of the substrate and has a surface that comes into direct contact with the exhaust gas flow if the catalyst coating layer is a laminate consisting of two or more layers.

[0031] The length of the top layer may typically be the same as the length of the substrate.

[0032] -Upper Zone 1- The upper first zone mainly contributes to the purification of HC, and is particularly effective in purifying cold HC.

[0033] To achieve this purpose, the upper first zone contains Pd. In addition to Pd, the upper first zone may contain inorganic oxide particles, a binder, and the like.

[0034] The Pd concentration in the first upper zone, expressed as the metal-equivalent Pd mass per unit volume of the substrate, may be 0.5 g / L or more, 1.0 g / L or more, 1.2 g / L or more, 1.4 g / L or more, or 1.6 g / L or more, and may be 5.0 g / L or less, 4.0 g / L or less, 3.0 g / L or less, or 2.0 g / L or less. A Pd concentration within this range ensures good cold HC purification performance without excessively increasing the amount of Pd used.

[0035] The upper first zone may or may not contain catalytic precious metals other than Pd. Examples of catalytic precious metals other than Pd include platinum (Pt) and rhodium (Rh). The upper first zone may be substantially free of catalytic precious metals other than Pd. The amount of catalytic precious metals other than Pd in ​​the upper first zone may be 5 mass% or less, 3 mass% or less, 1 mass% or less, 0.5 mass% or less, 0.3 mass% or less, or 0.1 mass% or less, based on the mass of all catalytic precious metals in the upper first zone. Alternatively, the upper first zone may be completely free of catalytic precious metals other than Pd.

[0036] The upper first zone may contain inorganic oxide particles. The inorganic oxide particles in the upper first zone may be selected from, for example, alumina, silica, titania, zirconia, ceria, and rare earth metal oxides other than ceria, and may be one or more selected from these. When two or more types of inorganic oxide particles are contained, they may be a mixture of multiple inorganic oxide particles, particles of a composite oxide containing two or more inorganic elements, a mixture of particles of two or more composite oxides, or a mixture of one or more inorganic oxide particles and one or more composite oxide particles.

[0037] The upper first zone may contain particles of one or more inorganic oxides selected from alumina and composite oxides containing aluminum (Al). The composite oxide containing Al may be a composite oxide containing Al and a rare earth metal element other than Ce, and in particular, may be a composite oxide containing Al and a rare earth metal element selected from lanthanum (La), praseodymium (Pr), yttrium (Y), neodymium (Nd), etc.

[0038] The upper first zone may be substantially free of inorganic oxide particles selected from composite oxides containing ceria and Ce. That is, the upper first zone may be substantially free of Ce. By being substantially free of Ce, the oxidation catalytic activity of Pd, which contributes to HC purification, is effectively exhibited. The Ce concentration in the upper first zone may be 1.0 g / L or less, 0.5 g / L or less, 0.3 g / L or less, or 0.1 g / L or less, in terms of ceria-equivalent mass per unit volume of the substrate, or the upper first zone may be completely free of composite oxides containing ceria and Ce.

[0039] The particle size of the inorganic oxide particles in the upper first zone may be, for example, 3 μm or more and 8 μm or less.

[0040] The amount of inorganic oxide particles in the upper first zone may be, for example, 10 g / L or more, 15 g / L or more, 20 g / L or more, 25 g / L or more, or 30 g / L or more, in terms of the mass of inorganic oxide particles per unit volume of the substrate, and may be, for example, 100 g / L or less, 80 g / L or less, 70 g / L or less, or 60 g / L or less.

[0041] The Pd in ​​the upper first zone may be in the form of particles, and may be supported on inorganic oxide particles as Pd particles. The particle size of the Pd particles supported on the inorganic oxide particles may be, for example, 1 nm or more and 15 nm or less.

[0042] The inorganic oxide particles supporting Pd in ​​the upper first zone may be, for example, one or more types selected from alumina and composite oxides containing Al element.

[0043] The binder in the upper first zone may be, for example, a boehmite binder, an alumina sol, a silica sol, or the like.

[0044] The length of the upper first zone may be 5% or more, 10% or more, 15% or more, 20% or more, 25% or more, or 30% or more of the length of the upper layer to ensure sufficiently high cold HC purification capacity, and may be 50% or less, 45% or less, 40% or less, or 35% or less of the length of the upper layer to maintain the lengths of the upper second zone and upper third zone that contribute to cold NOx purification.

[0045] -Upper Zone 2- The upper second zone mainly contributes to purifying NOx, and is particularly effective in purifying cold NOx.

[0046] To achieve this purpose, the upper second zone contains Rh. The upper second zone may contain inorganic oxide particles, a binder, and the like in addition to Rh.

[0047] The Rh concentration in the second upper zone, expressed as the metal mass of Rh per unit volume of the substrate, may be 0.05 g / L or more, 0.10 g / L or more, 0.15 g / L or more, 0.20 g / L or more, or 0.25 g / L or more, and may be 0.50 g / L or less, 0.40 g / L or less, 0.35 g / L or less, or 0.30 g / L or less. A Rh concentration within this range ensures good cold NOx purification performance without excessively increasing the amount of Rh used.

[0048] The upper second zone may or may not contain catalytic precious metals other than Rh. Examples of catalytic precious metals other than Rh include Pt and Pd. The upper second zone may be substantially free of catalytic precious metals other than Rh. The amount of catalytic precious metals other than Rh in the upper second zone may be 5% by mass or less, 3% by mass or less, 1% by mass or less, 0.5% by mass or less, 0.3% by mass or less, or 0.1% by mass or less, based on the mass of all catalytic precious metals in the upper second zone. Alternatively, the upper second zone may be completely free of catalytic precious metals other than Rh.

[0049] The second upper zone may contain inorganic oxide particles. The inorganic oxide particles in the second upper zone may be appropriately selected from the inorganic oxide particles exemplified above for the first upper zone.

[0050] The upper second zone may contain particles of one or more inorganic oxides selected from ceria, composite oxides containing Ce element, alumina, and composite oxides containing Al element (except when Ce element is contained).

[0051] The composite oxide containing Ce element may be a composite oxide containing Ce element and one or two inorganic elements selected from zirconium (Zr) element and Al element, or may be a composite oxide further containing a rare earth metal element other than Ce together with these.Specific examples of the composite oxide containing Ce element include Ce-Zr composite oxide, Al-Ce-Zr composite oxide, etc., and composite oxides thereof further containing a rare earth metal element other than Ce.

[0052] Examples of composite oxides containing Al include composite oxides containing Al and Zr, and composite oxides of these that further contain a rare earth metal element other than Ce.

[0053] In the above, the rare earth metal element other than Ce may be selected from, for example, La, Pr, Y, Nd, and the like.

[0054] The second upper zone may contain inorganic oxide particles selected from ceria and a composite oxide containing Ce. The Ce concentration in the second upper zone, expressed as a ceria-equivalent mass per unit volume of the substrate, may be 2.0 g / L or more, 2.5 g / L or more, 3.0 g / L or more, 3.5 g / L or more, or 4.0 g / L or more, or 12.0 g / L, 10.0 g / K or less, 7.0 g / L or less, 6.0 g / L or less, 5.0 g / L or less, 4.0 g / L or less, 3.0 g / L or less, 2.0 g / L or less, or 1.0 g / L or less. Alternatively, the second upper zone may not contain Ce.

[0055] The particle size of the inorganic oxide particles in the upper second zone may be, for example, 3 μm or more and 8 μm or less.

[0056] The amount of inorganic oxide particles in the upper second zone may be, for example, 40 g / L or more, 45 g / L or more, 50 g / L or more, 55 g / L or more, or 60 g / L or more, in terms of the mass of inorganic oxide particles per unit volume of the substrate, and may be, for example, 150 g / L or less, 120 g / L or less, 100 g / L or less, or 80 g / L or less.

[0057] --Rh carrier in the upper second zone-- The Rh in the upper second zone may be in the form of particles, and may be supported on inorganic oxide particles as Rh particles. The particle size of the Rh particles supported on the inorganic oxide particles may be, for example, 1 nm or more and 15 nm or less.

[0058] In another embodiment of the present invention, at least a portion of the Rh in the upper second zone is supported on inorganic oxide particles containing elemental Ce. The inorganic oxide particles containing elemental Ce may be, for example, ceria, a Ce-Zr composite oxide, or an Al-Ce-Zr composite oxide.

[0059] In yet another embodiment of the present invention, at least a portion of the Rh contained in the upper second zone is supported on inorganic oxide particles substantially free of Ce element. The inorganic oxide particles substantially free of Ce element may be, for example, alumina, Al-Zr composite oxide, etc.

[0060] In yet another embodiment of the present invention, at least a portion of the Rh in the upper second zone is supported on inorganic oxide particles containing elemental Ce, and the upper second zone further contains inorganic oxide particles substantially free of elemental Ce, which may not support Rh.

[0061] In yet another embodiment of the present invention, at least a portion of the Rh contained in the upper second zone is supported on inorganic oxide particles that are substantially free of Ce element, and the upper second zone further contains inorganic oxide particles containing Ce element, which may not support Rh.

[0062] The binder in the upper second zone may be, for example, a boehmite binder, an alumina sol, a silica sol, or the like.

[0063] The length of the upper second zone may be 5% or more, 7% or more, 10% or more, 12% or more, or 15% or more of the length of the upper layer in order to ensure sufficiently high cold NOx purification capacity, and may be 30% or less, 28% or less, 25% or less, 23% or less, or 20% or less of the length of the upper layer in order to maintain the lengths of the upper first zone, which contributes to cold HC purification, and the upper third zone, which contributes to the purification of NOx that cannot be completely purified in the upper second zone.

[0064] -Upper Zone 3- The upper third zone mainly contributes to purifying NOx, and is particularly effective in purifying cold NOx that could not be completely purified in the upper second zone.

[0065] To achieve this purpose, the upper third zone contains Rh. The upper third zone may contain inorganic oxide particles, a binder, and the like in addition to Rh.

[0066] The Rh concentration in the upper third zone, expressed as the metal mass of Rh per unit volume of the substrate, may be 0.05 g / L or more, 0.07 g / L or more, 0.10 g / L or more, 0.11 g / L or more, or 0.13 g / L or more, or 0.50 g / L or less, 0.40 g / L or less, 0.30 g / L or less, 0.20 g / L or less, less than 0.20 g / L, or 0.15 g / L or less. An Rh concentration within this range can further improve NOx purification ability without excessively increasing the amount of Rh used.

[0067] The Rh concentration in the upper third zone may be lower than the Rh concentration in the upper second zone. In one embodiment of the present invention, the Rh concentration in the upper second zone is 0.20 g / L or more and 0.50 g / L or less, and the Rh concentration in the upper third zone is 0.05 g / L or more and less than 0.20 g / L.

[0068] The upper third zone may or may not contain catalytic precious metals other than Rh. Examples of catalytic precious metals other than Rh include Pt and Pd. The upper third zone may be substantially free of catalytic precious metals other than Rh. The amount of catalytic precious metals other than Rh in the upper third zone may be 5 mass% or less, 3 mass% or less, 1 mass% or less, 0.5 mass% or less, 0.3 mass% or less, or 0.1 mass% or less, based on the mass of all catalytic precious metals in the upper third zone. Alternatively, the upper third zone may be free of catalytic precious metals other than Rh.

[0069] The upper third zone may contain inorganic oxide particles. The inorganic oxide particles in the upper third zone may be appropriately selected from the inorganic oxide particles exemplified above for the upper first zone.

[0070] The upper third zone may contain particles of one or more inorganic oxides selected from ceria, a composite oxide containing Ce, alumina, and a composite oxide containing Al (excluding those containing Ce). Here, examples of the composite oxide containing Ce and the composite oxide containing Al are the same as those in the upper second zone.

[0071] The upper third zone preferably contains inorganic oxide particles selected from ceria and a composite oxide containing Ce. The Ce concentration in the upper third zone, in terms of ceria-equivalent mass per unit volume of the substrate, may be 5.0 g / L or more, 6.0 g / L or more, 7.0 g / L or more, or 8.0 g / L or more, and may be 15.0 g / L or less, 14.0 g / L or less, 13.0 g / L or less, 12.0 g / L or less, 11.0 g / L or less, or 10.0 g / L or less.

[0072] The Ce element concentration in the upper third zone may be higher than the Ce element concentration in the upper second zone. In one embodiment of the present invention, the Ce element concentration in terms of ceria in the upper third zone is 5.0 g / L or more and 15.0 g / L or less, the Ce element concentration in terms of ceria in the upper second zone is 7.0 g / L or less, and the Ce element concentration in the upper third zone is higher than the Ce element concentration in the upper second zone.

[0073] The particle size of the inorganic oxide particles in the upper third zone may be, for example, 3 μm or more and 8 μm or less.

[0074] The amount of inorganic oxide particles in the upper third zone may be, for example, 50 g / L or more, 60 g / L or more, 70 g / L or more, or 80 g / L or more, in terms of the mass of inorganic oxide particles per unit volume of the substrate, and may be, for example, 200 g / L or less, 150 g / L or less, 120 g / L or less, or 100 g / L or less.

[0075] --Rh carrier in the upper third zone-- The Rh in the upper third zone may be in the form of particles, and may be supported on inorganic oxide particles as Rh particles. The particle size of the Rh particles supported on the inorganic oxide particles may be, for example, 1 nm or more and 15 nm or less.

[0076] In one embodiment of the present invention, at least a portion of the Rh in the upper third zone is supported on inorganic oxide particles containing element Ce.

[0077] In another embodiment of the present invention, at least a portion of the Rh in the upper third zone is supported on inorganic oxide particles containing elemental Ce, and the upper second zone further contains inorganic oxide particles substantially free of elemental Ce, which may not support Rh.

[0078] The binder in the upper third zone may be, for example, a boehmite binder, an alumina sol, a silica sol, or the like.

[0079] The length of the upper third zone may be 20% or more, 30% or more, 35% or more, 40% or more, or 45% or more of the length of the upper layer to ensure sufficiently high NOx purification capacity, and may be 90% or less, 80% or less, 70% or less, or 60% or less of the length of the upper layer to maintain the lengths of the upper first zone, which contributes to cold HC purification, and the upper second zone, which contributes to cold NOx purification.

[0080] (lower layer) The catalyst coating layer of the exhaust gas purification catalyst device of the present invention may be a single-layer structure having only the top layer described above, or may be a two-layer laminate structure having a lower layer between the substrate and the top layer.

[0081] The lower layer of the catalyst coating layer is, for example, The lower first zone containing Rh, and a lower second zone containing one or two elements selected from Pd and Pt; in that order.

[0082] The length of the underlayer may typically be the same as the length of the substrate.

[0083] -Lower Zone 1- The lower first zone contains Rh and contributes to the purification of HC and NOx during cold to warm-up periods. Rh has high catalytic activity in the cold region, and the temperature of the catalyst coating layer rises from the upstream side of the exhaust gas flow during warm-up periods. Therefore, the lower first zone containing Rh contributes greatly to the purification of HC and NOx during cold to warm-up periods.

[0084] The composition of the lower first zone may be appropriately selected from the ranges described above for the composition of the upper second zone, or may be the same as the composition of the upper second zone.

[0085] The length of the lower first zone may be 10% or more, 15% or more, 20% or more, 25% or more, or 30% or more of the length of the lower layer to ensure a sufficiently high purification effect of HC and NOx, and may be 60% or less, 50% or less, 45% or less, 40% or less, or 30% or less of the length of the lower layer to maintain the length of the lower second zone that contributes to sweeping HC.

[0086] -Lower Zone 2- The lower second zone contains one or two elements selected from Pt and Pd. Due to the high oxidation activity of the one or two elements selected from Pt and Pd, the lower second zone contributes to purifying (sweeping) HC that could not be completely purified in the upper first zone and the lower first zone under high load.

[0087] To achieve this purpose, the first lower layer zone contains one or two selected from Pd and Pt. In addition to Pd and Pt, the first lower layer zone may contain inorganic oxide particles, a binder, etc.

[0088] The concentration of one or both of Pd and Pt in the second lower zone may be, in terms of the total mass of Pd and Pt in metal equivalent per unit volume of the substrate, 0.1 g / L or more, 0.3 g / L or more, 0.5 g / L or more, 0.6 g / L or more, or 0.8 g / L or more, and may be 3.0 g / L or less, 2.5 g / L or less, 2.0 g / L or less, 1.8 g / L or less, 1.5 g / L or less, or 1.5 g / L or less. A concentration within this range ensures good HC purification ability without excessively increasing the amounts of Pd and Pt used.

[0089] The lower second zone may or may not contain catalytic precious metals other than Pd and Pt. Examples of catalytic precious metals other than Pd and Pt include rhodium (Rh). The lower second zone may be substantially free of catalytic precious metals other than Pd and Pt. The amount of catalytic precious metals other than Pd and Pt in the lower second zone may be 5% by mass or less, 3% by mass or less, 1% by mass or less, 0.5% by mass or less, 0.3% by mass or less, or 0.1% by mass or less, based on the mass of all catalytic precious metals in the upper first zone. Alternatively, the upper first zone may be completely free of catalytic precious metals other than Pd and Pt.

[0090] The second lower zone may contain inorganic oxide particles. The inorganic oxide particles in the second lower zone may be appropriately selected from the inorganic oxide particles exemplified above for the first upper zone.

[0091] The lower second zone may contain particles of one or more inorganic oxides selected from alumina and composite oxides containing Al (except for those containing Ce), where the Al-containing composite oxides may be the same as those in the upper first zone.

[0092] The second lower zone may contain particles of an inorganic oxide selected from ceria and a composite oxide containing elemental Ce. The concentration of elemental Ce in the second lower zone may be 10 g / L or more, 20 g / L or more, 30 g / L or more, or 40 g / L or more, and 100 g / L or less, 80 g / L or less, 70 g / L or less, or 60 g / L or less, in terms of the ceria-equivalent mass per unit volume of the substrate.

[0093] The particle size of the inorganic oxide particles in the lower second zone may be, for example, 3 μm or more and 8 μm or less.

[0094] The amount of inorganic oxide particles in the lower second zone may be, for example, 10 g / L or more, 20 g / L or more, or 30 g / L or more, in terms of the mass of inorganic oxide particles per unit volume of the substrate, and may be, for example, 80 g / L or less, 70 g / L or less, 60 g / L or less, or 50 g / L or less.

[0095] The Pd and Pt in the lower second zone may be in particulate form and may be supported on inorganic oxide particles as Pd particles and Pt particles, respectively. The particle size of the Pd particles and Pt particles supported on the inorganic oxide particles may be, for example, 1 nm or more and 15 nm or less.

[0096] The binder in the lower second zone may be, for example, a boehmite binder, an alumina sol, a silica sol, or the like.

[0097] The length of the lower second zone may be 40% or more, 45% or more, 50% or more, 55% or more, or 60% or more of the length of the lower layer to ensure sufficiently high HC purification capacity, and may be 90% or less, 85% or less, 80% or less, 75% or less, 70% or less, or 60% or less of the length of the lower layer to maintain the length of the lower first zone that contributes to the purification of HC and NOx, particularly in the cold region.

[0098] (3rd layer) The catalyst coating layer of the exhaust gas purification catalytic device of the present invention may or may not have any additional layers other than the uppermost and lower layers described above. Examples of the additional layers include a layer having an adsorption function for HC, NH3, NOx, etc., and a layer having a purification function for HC, NOx, etc.

[0099] In some embodiments, the catalyst coating has no layers other than the top and bottom layers.

[0100] <Relative component concentration ratio between each layer> -Rh concentration- The Rh concentration in the lower first zone may be substantially the same as the Rh concentration in the upper second zone. "Substantially the same as the Rh concentration in the lower first zone" means that the Rh concentration in the lower first zone is 0.90 times or more, 0.95 times or more, or 0.98 times or more, and 1.10 times or less, 1.05 times or less, or 1.02 times or less, of the Rh concentration in the upper second zone.

[0101] The Rh concentration (mass of Rh per unit volume of substrate) in the second upper zone may be higher than the Rh concentration (mass of Rh per unit volume of substrate) in the third upper zone. The Rh concentration in the second upper zone may be 1.5 times or more, 2.0 times or more, 2.5 times or more, or 3.0 times or more, and may be 4.0 times or less, 3.5 times or less, 3.0 times or less, or 2.5 times or less, of the Rh concentration in the third upper zone.

[0102] The amount of Rh contained in the exhaust gas purification catalyst device of the present invention may be, in terms of the total mass of Rh per unit volume of the substrate, 0.1 g / L or more, 0.2 g / L or more, 0.3 g / L or more, or 0.4 g / L or more, and may be 1.0 g / L or less, 0.8 g / L or less, 0.6 g / L or less, or 0.5 g / L or less.

[0103] -Ce concentration- The Ce element concentration in the lower first zone may be substantially the same as the Ce element concentration in the upper second zone. "The Ce element concentration in the lower first zone being substantially the same as the Ce element concentration in the upper second zone" means that the Ce element concentration in the lower first zone is 0.90 times or more, 0.95 times or more, or 0.98 times or more, and 1.10 times or less, 1.05 times or less, or 1.02 times or less, of the Ce element concentration in the upper second zone.

[0104] The Ce element concentration in the upper second zone may be the same as or lower than the Ce element concentration in the upper third zone. By making the Ce element concentration in the upper second zone lower than the Ce element concentration in the upper third zone, the catalytic activity of Rh on the upstream side of the exhaust gas flow in the cold region can be increased, which is advantageous in purifying HC and NOx in the cold region.

[0105] The Ce element concentration (ceria-equivalent mass per unit volume of the substrate) in the upper second zone may be 1.0 times or less, 0.8 times or less, 0.6 times or less, 0.5 times or less, 0.4 times or less, or 0.3 times or less of the Ce element concentration (ceria-equivalent mass per unit volume of the substrate) in the upper third zone.

[0106] In one embodiment of the present invention, the upper second zone does not contain elemental Ce, and the upper third zone contains elemental Ce.

[0107] The Ce element concentration in the lower second zone may be higher than that in the upper third zone, which has the advantage of maintaining NOx purification performance at high loads while exhibiting effective OSC performance.

[0108] The Ce element concentration (ceria equivalent mass per unit volume of the substrate) in the lower second zone may be 2.0 times or more, 3.0 times or more, 4.0 times or more, 5.0 times or more, or 6.0 times or more, and may be 12.0 times or less, 10.0 times or less, 8.0 times or less, or 7.0 times or less, of the Ce element concentration (ceria equivalent mass per unit volume of the substrate) in the upper third zone.

[0109] Furthermore, as described above, the upper first zone may be substantially free of Ce elements. That is, the Ce element concentrations in each zone may be in the order of (upper first zone) < (lower first zone ≈ upper second zone) < (upper third zone) < (lower second zone). This concentration order means that the Ce element concentration on the upstream side of the exhaust gas flow is lower than the Ce element concentration on the downstream side. Therefore, in the exhaust gas purification catalytic device of the present invention, the low-temperature purification activity on the upstream side of the catalyst coating layer is relatively high.

[0110] <<Method for manufacturing an exhaust gas purification catalyst device>> The exhaust gas purification catalyst device of the present invention may be produced by any method as long as it has the above-mentioned configuration.

[0111] As a non-limiting example, we will explain one example of a method for manufacturing an exhaust gas purification catalyst device in which the catalyst coating layer is a two-layer laminate consisting of a top layer and a bottom layer, and the composition of the upper layer second zone and the composition of the lower layer first zone are the same.

[0112] Such an exhaust gas purification catalytic device may be manufactured, for example, by sequentially forming each zone in a predetermined length on a substrate. The order of forming the zones may be, for example, any of the following: The order is lower zone 2, upper zone 3, lower zone 1, upper zone 2, and upper zone 1; the lower second zone, the lower first zone, the upper second zone, the upper third zone, and the upper first zone; or The order is lower zone 2, lower zone 1, upper zone 2, upper zone 1, and upper zone 3.

[0113] In the above, the lower first zone and the upper second zone may be formed simultaneously.

[0114] Each zone may be formed by applying a coating solution prepared according to the desired zone composition, drying (solvent removal) as necessary, and then baking. Baking may be performed for each zone formed, or may be performed all at once after all zones have been coated.

[0115] The coating liquid may be a liquid composition containing a component to be contained in the desired zone or a precursor thereof, and a solvent. The coating liquid may contain, for example, the following components: One or more inorganic oxide particles, a precious metal precursor, and optional components used as needed, and a solvent (first coating liquid); or Inorganic oxide particles carrying precious metal particles, other inorganic oxide particles as required, and optional components used as required, and a solvent (second coating liquid).

[0116] When the first coating liquid contains two or more inorganic oxide particles and a precious metal precursor, it is believed that the precious metal particles will be supported on all of the two or more inorganic oxide particles. However, when the coating liquid is prepared by contacting the first inorganic oxide particles on which the precious metal particles are to be supported with the precious metal precursor in a solvent and then adding the second inorganic oxide particles, it is believed that most of the precious metal particles will be supported on the first inorganic oxide particles.

[0117] The inorganic oxide particles carrying the noble metal particles in the second coating fluid may be produced according to a known method.

[0118] The coating of the coating liquid, drying, and baking may each be carried out according to a known method.

[0119] <Exhaust gas purification method> According to another aspect of the present invention, there is provided a method for purifying exhaust gas.

[0120] The exhaust gas purification method of the present invention is a method comprising arranging the exhaust gas purification catalyst device of the present invention in the exhaust system of an internal combustion engine with the upper layer first zone facing upstream of the exhaust gas flow, and purifying the exhaust gas emitted from the internal combustion engine.

[0121] The internal combustion engine may be, for example, a gasoline engine, a diesel engine, a hybrid engine, or the like of an automobile. [Example]

[0122] <<Preparation of Coating Solution for Forming Upper Layer First Zone>> Palladium nitrate as a PGM source in an amount equivalent to 1.745 g / L of metallic Pd mass, alumina as inorganic oxide particles in an amount equivalent to 80 g / L, and boehmite binder in an amount equivalent to 4 g / L were added to pure water and stirred thoroughly to prepare a coating solution for forming the first upper layer zone.

[0123] <<Preparation of Coating Solution for Forming Lower Layer Second Zone>> Platinum nitrate as a PGM source in an amount equivalent to 1.085 g / L of metal Pt mass, alumina as inorganic oxide particles in an amount equivalent to 40 g / L, and boehmite binder in an amount equivalent to 5.0 g / L were added to pure water and stirred thoroughly to prepare a coating solution for forming the second lower layer zone.

[0124] Preparation of Coating Solution (1) for Forming Lower Layer Zone 1 and Upper Layer Zone 2 Rhodium nitrate (equivalent to 0.279 g / L of metallic Rh) and 30.0 g / L of Al·Zr composite oxide (Al2O3:ZrO2 = 30:60 (mass ratio), AZ) were added to pure water as a PGM source and stirred at room temperature for at least 30 minutes. Next, 35.0 g / L of alumina and 10.0 g / L of Al·Ce·Zr composite oxide (Al2O3:CeO2:ZrO2 = 30:20:42 (mass ratio), ACZ) were added in this order, and 3.0 g / L of boehmite binder was added as a binder. The mixture was then thoroughly stirred to prepare coating solution (1) for forming the lower first and upper second zones.

[0125] Preparation of Coating Solutions (2) to (5) for Forming Lower Layer Zone 1 and Upper Layer Zone 2 Coating Liquids (2) to (5) for forming the lower first zone and the upper second zone were prepared in the same manner as in "Preparation of Coating Liquid (1) for forming the lower first zone and the upper second zone" above, except that the amount of rhodium nitrate and the amount of ACZ were changed so that the amount of metallic Rh and the amount of CeO2 in the coating liquid were adjusted to the values ​​shown in Table 1.

[0126] Preparation of Coating Solution (6) for Forming Lower Layer First Zone and Upper Layer Second Zone Coating solution (6) for forming the lower first zone and the upper second zone was prepared in the same manner as in "Preparation of coating solution (1) for forming the lower first zone and the upper second zone" above, except that ACZ was not used.

[0127] Preparation of Coating Solution (7) for Forming Lower Layer First Zone and Upper Layer Second Zone Rhodium nitrate (equivalent to 0.279 g / L of metallic Rh mass) as a PGM source and ACZ (equivalent to 10.0 g / L) were added to pure water and stirred at room temperature for 30 minutes or more. Next, 35.0 g / L of alumina and 3.0 g / L of boehmite binder were added and stirred thoroughly to prepare Coating Solution (7) for forming the lower first zone and upper second zone.

[0128] [Table 1]

[0129] <<Preparation of Coating Solution for Forming Upper Layer Zone 3>> A coating liquid for forming the upper third zone was prepared in the same manner as in the above "Preparation of Coating Liquid (7) for Forming the Lower First Zone and the Upper Second Zone," except that the amount of rhodium nitrate charged was set to an amount equivalent to 0.139 g / L in terms of metallic Rh mass, the amount of ACZ charged was set to an amount equivalent to 45.0 g / L, and the amount of alumina charged was set to an amount equivalent to 35.0 g / L.

[0130] Preparation of Coating Solution for Forming Lower Layer First Zone for Comparative Example 1 A coating solution for forming the first lower layer zone for Comparative Example 1 was prepared in the same manner as in the above "Preparation of Coating Solution (1) for Forming the First Lower Layer Zone and the Second Upper Layer Zone" except that the amount of rhodium nitrate charged was set to an amount equivalent to 0.139 g / L in terms of metallic Rh mass.

[0131] Preparation of Coating Solution for Forming Upper Layer Second Zone for Comparative Example 1 The coating solution for forming the second upper layer zone for Comparative Example 1 was prepared in the same manner as in "Preparation of Coating Solution (7) for Forming the Lower First Zone and the Upper Second Zone" above, except that the amount of rhodium nitrate charged was set to an amount equivalent to 0.100 g / L in terms of metallic Rh mass, and the amount of ACZ charged was set to an amount equivalent to 45.0 g / L.

[0132] Each of the above coating solutions was prepared each time in an amount that would give the component concentrations in the coated area the values ​​described above when the entire amount was applied to a predetermined coating length, taking into consideration the coating width, and the entire amount was used.

[0133] Example 1 The substrate has a diameter of 127 mm, a length of 102 mm, an apparent volume of 1.29 L, and 750 cells / cm. 2 A straight-flow type substrate made of cordierite with a wall thickness of 2.5 μm was used.

[0134] The coating liquid for forming the lower second zone was applied to an area of ​​67% of the substrate length from the downstream side of the exhaust gas flow of the substrate, and the substrate was baked at 500°C for 1 hour to form the lower second zone on the substrate. Next, the coating liquid for forming the upper third zone was applied to an area of ​​50% of the substrate length from the downstream side of the substrate on which the lower second zone had been formed, and the substrate was baked at 500°C for 1 hour to form the upper third zone.

[0135] Furthermore, the coating liquid (1) for forming the lower first zone and upper second zone was coated onto the substrate on which the lower second zone and upper third zone had been formed, covering an area of ​​50% of the substrate length from the upstream side, and the substrate was baked at 500°C for 1 hour to form the lower first zone and upper second zone. The length of the formed lower first zone was 33% of the total length of the substrate, and the length of the upper second zone was 17% of the total length of the substrate.

[0136] Finally, the coating liquid for forming the upper first zone was applied to a region of 33% of the length of the substrate from the upstream side on which the lower first zone, lower second zone, upper second zone, and upper third zone had been formed, and the substrate was baked at 500°C for 1 hour to form the upper first zone, thereby producing the exhaust gas purification catalyst device of Example 1. Figure 1 shows an outline of the configuration of the exhaust gas purification catalyst device of Example 1.

[0137] Examples 2 to 7 Exhaust gas purification catalyst devices of Examples 2 to 7 were produced in the same manner as in Example 1, except that the lower first zone and upper second zone forming coating liquids with the numbers shown in the "Coating Liquid Type" column in Table 2 were used instead of the lower first zone and upper second zone forming coating liquid (1). Figures 2 to 7 show the outline of the configuration of these exhaust gas purification catalyst devices.

[0138] Comparative Example 1 As the substrate, a straight flow type substrate made of cordierite of the same kind as that used in Example 1 was used.

[0139] The coating liquid for forming the second lower layer zone was coated on the substrate from the downstream side of the exhaust gas flow to a region covering 67% of the substrate length, and then baked at 500°C for 1 hour to form the second lower layer zone on the substrate. Next, the coating liquid for forming the first lower layer zone for Comparative Example 1 was prepared and coated on the substrate on which the second lower layer zone had been formed to a region covering 33% of the substrate length from the upstream side, and then baked at 500°C for 1 hour to form the first lower layer zone.

[0140] Furthermore, the upper second zone forming coating liquid for Comparative Example 1 was coated on a region of the substrate on which the lower first zone and lower second zone were formed, covering 67% of the substrate length from the upstream side, and baked at 500°C for 1 hour to form the upper second zone. Finally, the upper first zone forming coating liquid was coated on a region of the substrate on which the lower first zone, lower second zone, and upper second zone were formed, covering 33% of the substrate length from the upstream side, and baked at 500°C for 1 hour to form the upper first zone, thereby producing the exhaust gas purification catalyst device of Comparative Example 1. Figure 8 shows an outline of the configuration of the exhaust gas purification catalyst device of Comparative Example 1.

[0141] <Evaluation of exhaust gas purification catalyst devices> Each of the exhaust gas purification catalyst devices manufactured as described above was subjected to durability testing by the following method, and then its exhaust gas purification ability was evaluated.

[0142] (1) Durability The exhaust gas purification catalyst devices obtained in the above examples and comparative examples were installed in the exhaust system of a 2.7L TC (turbocharged) gasoline engine so that the upper first zone and the lower first zone were located upstream of the exhaust gas flow, and the exhaust gas was alternately stoichiometric and lean atmospheres at predetermined intervals to perform a durability test equivalent to driving 150,000 miles.

[0143] (2) Evaluation of exhaust gas purification capacity After the durability test, each exhaust gas purification catalyst device was installed in the exhaust system of a 2.7L gasoline engine (turbocharged) vehicle, with the upper and lower first zones positioned upstream of the exhaust gas flow, and the exhaust gas purification performance was evaluated using the FTP75. The evaluation results are shown in Tables 2 to 4.

[0144] [Table 2]

[0145] [Table 3]

[0146] [Table 4]

[0147] The inorganic oxide particles in Tables 2 to 4 are listed in the order of addition when preparing the coating liquid. The results shown in Tables 2 and 3 verify that the exhaust gas purification catalyst devices of Examples 1 to 7 of the present invention suppress NOx emissions compared to the exhaust gas purification catalyst device of Comparative Example 1, which belongs to the prior art.

[0148] In particular, in the exhaust gas purification catalyst devices of Examples 1 to 5, in which the Ce element concentration in the upper second zone is lower than the Ce element concentration in the upper third zone, it was verified that NOx emissions were suppressed in Bag 1, which corresponds to a cold start, Bag 2, which corresponds to a transient period, and Bag 3, which corresponds to high-speed driving.

Claims

1. An exhaust gas purification catalyst device having a base material and a catalyst coat layer on the base material, where the outermost layer of the catalyst coat layer has, in this order from the upstream side of the exhaust gas flow, an upper layer first zone containing Pd, an upper layer second zone containing Rh, and an upper layer third zone containing Rh, where the Rh concentration in the upper layer second zone is 0.10 g / L or more and 0.50 g / L or less in terms of the mass of Rh in terms of metal per unit volume of the base material, and the Rh concentration in the upper layer third zone is 0.05 g / L or more and 0.40 g / L or less in terms of the mass of Rh in terms of metal per unit volume of the base material, and the Rh concentration in the upper layer second zone is higher than the Rh concentration in the upper layer third zone, where the Ce element concentration in terms of ceria in the upper layer second zone is 7.0 g / L or less, and the Ce element concentration in the upper layer second zone is lower than the Ce element concentration in the upper layer third zone, where the catalyst coat layer is a laminate composed of two or more layers having a lower layer between the base material and the outermost layer, An exhaust gas purification catalyst device.

2. where the Rh concentration in terms of metal in the upper layer second zone is 0.20 g / L or more and 0.50 g / L or less, and where the Rh concentration in terms of metal in the upper layer third zone is 0.05 g / L or more and less than 0.20 g / L, The exhaust gas purification catalyst device according to Claim 1.

3. where the Rh concentration in the upper layer second zone is 1.5 times or more and 4.0 times or less the Rh concentration in the upper layer third zone, The exhaust gas purification catalyst device according to Claim 1.

4. The exhaust gas purification catalyst device according to Claim 1, where the Ce element concentration in the upper layer second zone is 0.8 times or less the Ce element concentration in the upper layer third zone.

5. where the Ce element concentration in terms of ceria in the upper layer third zone is 5.0 g / L or more and 15.0 g / L or less, The exhaust gas purification catalyst device according to Claim 1.

6. where the Ce element concentration in terms of ceria in the upper layer third zone is 5.0 g / L or more and 15.0 g / L or less, The exhaust gas purification catalyst device according to Claim 2.

7. where the Ce element concentration in terms of ceria in the upper layer third zone is 5.0 g / L or more and 15.0 g / L or less, The exhaust gas purification catalyst device according to Claim 3.

8. where at least a part of the Rh contained in the upper layer second zone is supported on inorganic oxide particles containing the Ce element, and where the Rh contained in the upper layer third zone is supported on inorganic oxide particles containing the Ce element. The exhaust gas purification catalyst device according to any one of claims 1 to 7.

9. At least a portion of the Rh contained in the upper second zone is supported on inorganic oxide particles that are substantially free of Ce element, and the Rh contained in the upper third zone is supported on inorganic oxide particles containing Ce; The exhaust gas purification catalyst device according to any one of claims 1 to 7.

10. at least a portion of the Rh contained in the upper second zone is supported on inorganic oxide particles that are substantially free of Ce element; the upper second zone further contains inorganic oxide particles containing Ce element, and the Rh contained in the upper third zone is supported on inorganic oxide particles containing Ce; The exhaust gas purification catalyst device according to any one of claims 1 to 7.

11. The lower layer of the catalyst coating layer is, from the upstream side of the exhaust gas flow, a lower first zone containing Rh; and a lower second zone containing one or two selected from Pd and Pt; in that order, The exhaust gas purification catalyst device according to any one of claims 1 to 7.

12. 12. The catalytic device for purifying exhaust gas according to claim 11, wherein the Rh concentration in the upper second zone is substantially the same as the Rh concentration in the lower first zone.

13. 10. A method for purifying exhaust gas, comprising: disposing the exhaust gas purification catalyst device according to any one of claims 1 to 7 in an exhaust system of an internal combustion engine, with the upper layer first zone facing upstream in an exhaust gas flow, and purifying exhaust gas emitted from the internal combustion engine.

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