Exhaust purification catalyst device

Abstract

This exhaust gas purification catalyst device is provided with a substrate and a catalyst coating layer on the substrate, and is characterized in that: the catalyst coating layer is a single layer or a laminate comprising two or more layers; the uppermost layer of the catalyst coating layer has an upper layer first region containing Pd, an upper layer second region containing Rh, and an upper layer third region containing Rh in this order from the upstream side of the exhaust gas flow, and the Rh concentration of the upper layer second region is higher than the Rh concentration of the upper layer third region.

Description

Technical Field

[0001] This invention relates to an exhaust gas purification catalyst device. Background Technology

[0002] Exhaust gases from internal combustion engines, such as automobile engines, contain nitrogen oxides (NOx). x These exhaust gases contain carbon monoxide (CO), hydrocarbons (HC), etc. These gases are released into the atmosphere after being purified by an exhaust purification catalyst that oxidizes CO and HC and reduces NOx.

[0003] To mitigate air pollution, various countries have set emission limits for vehicles per unit distance traveled, based on the composition of exhaust gases. These emission regulations are being strengthened annually. Currently, the United States uses LEV III regulations, Europe uses the Euro VI standard, and China uses the China VI standard. It is believed that in the near future, these standards will transition to LEV IV, Euro VII, and China VII, respectively.

[0004] Euro 7 standards, for example, require reductions in NOx emissions in cold regions, such as during engine start-up. The exhaust atmosphere during engine start-up is in the rich-to-then-stoichiometric range. Therefore, existing NOx purification technologies based on lean-burn engines are insufficient to reduce NOx emissions in cold regions.

[0005] As a prior art NOx emission reduction technology, for example, Patent Document 1 describes a catalyst for exhaust gas purification, which has a lower catalyst layer and an upper catalyst layer.

[0006] The lower catalyst layer contains a first composite oxide and Pd supported on the first composite oxide, wherein the first composite oxide comprises Ce and Zr.

[0007] The upper catalyst layer contains a second composite oxide and Rh supported on the second composite oxide, wherein the second composite oxide comprises Ce and Zr.

[0008] At least one of the first and second composite oxides contains an alkaline earth metal selected from Ca, Sr, and Mg in solid solution.

[0009] In addition, Patent Document 2 describes a redox catalyst obtained by supporting palladium and alkaline earth metals on an oxide with oxygen storage and release capabilities.

[0010] Existing technical documents

[0011] Patent Document 1: Japanese Patent Application Publication No. 2010-119994

[0012] Patent Document 2: Japanese Patent Application Publication No. 2001-198461 Summary of the Invention

[0013] The aforementioned patent documents 1 and 2 are both prior art exhaust purification catalysts, which are insufficient in reducing NOx emissions in cold areas such as during engine start-up.

[0014] The present invention was made in view of the above circumstances, and its object is to provide an exhaust gas purification catalyst device that reduces both HC emissions and NOx emissions in the cold zone.

[0015] The present invention is described below.

[0016] <Solution 1> An exhaust gas purification catalyst device, comprising a substrate and a catalyst coating on the substrate.

[0017] The catalyst coating is a single layer or a laminate consisting of two or more layers.

[0018] The uppermost layer of the catalyst coating, starting from the upstream side of the exhaust flow, sequentially comprises an upper layer zone 1 containing Pd, an upper layer zone 2 containing Rh, and an upper layer zone 3 containing Rh.

[0019] The Rh concentration in the upper second zone is higher than the Rh concentration in the upper third zone.

[0020] <Scheme 2> The exhaust gas purification catalyst device described in Scheme 1

[0021] The Rh concentration in the upper second zone, calculated as metal, is above 0.20 g / L and below 0.50 g / L.

[0022] The Rh concentration in the upper third zone, calculated in metal terms, is above 0.05 g / L and below 0.20 g / L.

[0023] <Scheme 3> According to the exhaust purification catalyst device described in Scheme 1, the Rh concentration in the upper second zone is more than 1.5 times and less than 4.0 times the Rh concentration in the upper third zone.

[0024] <Scheme 4> According to the exhaust purification catalyst device described in Scheme 1, the Ce element concentration in the upper second zone is lower than the Ce element concentration in the upper third zone.

[0025] <Scheme 5> The exhaust gas purification catalyst device described in Scheme 1.

[0026] The Ce element concentration (converted to cerium dioxide) in the upper second zone is below 7.0 g / L, and,

[0027] The Ce element concentration in the upper third zone, as converted from cerium dioxide, is above 5.0 g / L and below 15.0 g / L.

[0028] <Scheme 6> The exhaust gas purification catalyst device described in Scheme 2

[0029] The Ce element concentration (converted to cerium dioxide) in the upper second zone is below 7.0 g / L, and,

[0030] The Ce element concentration in the upper third zone, as converted from cerium dioxide, is above 5.0 g / L and below 15.0 g / L.

[0031] <Scheme 7> The exhaust gas purification catalyst device described in Scheme 3.

[0032] The Ce element concentration (converted to cerium dioxide) in the upper second zone is below 7.0 g / L, and,

[0033] The Ce element concentration in the upper third zone, as converted from cerium dioxide, is above 5.0 g / L and below 15.0 g / L.

[0034] <Scheme 8> An exhaust gas purification catalyst device according to any one of Schemes 1 to 7,

[0035] At least a portion of the Rh contained in the upper second region is supported on inorganic oxide particles containing Ce.

[0036] The Rh contained in the upper third region is supported on inorganic oxide particles containing Ce.

[0037] <Scheme 9> An exhaust gas purification catalyst device according to any one of Schemes 1 to 7,

[0038] At least a portion of the Rh contained in the upper second region is supported on inorganic oxide particles that are substantially free of Ce.

[0039] The Rh contained in the upper third region is supported on inorganic oxide particles containing Ce.

[0040] <Scheme 10> An exhaust gas purification catalyst device according to any one of Schemes 1 to 7,

[0041] At least a portion of the Rh contained in the upper second region is supported on inorganic oxide particles that are substantially free of Ce.

[0042] The upper second region also contains inorganic oxide particles containing Ce, and,

[0043] The Rh contained in the upper third region is supported on inorganic oxide particles containing Ce.

[0044] <Scheme 11> An exhaust gas purification catalyst device according to any one of Schemes 1 to 7,

[0045] The catalyst coating is a laminate consisting of two layers.

[0046] The lower layer of the catalyst coating, starting from the upstream side of the exhaust flow, sequentially comprises:

[0047] The lower zone 1 containing Rh; and

[0048] It contains a lower second zone selected from one or two of Pd and Pt.

[0049] <Scheme 12> According to the exhaust gas purification catalyst device described in Scheme 11, the Rh concentration in the upper second zone is substantially the same as the Rh concentration in the lower first zone.

[0050] <Scheme 13> An exhaust purification method includes the following steps: in the exhaust system of an internal combustion engine, an exhaust purification catalyst device as described in any one of Schemes 1 to 7 is arranged in such a way that the upper first zone faces the upstream side of the exhaust flow, and the exhaust gas discharged from the internal combustion engine is purified.

[0051] According to the present invention, an exhaust gas purification catalyst device is provided that reduces both HC emissions and NOx emissions in the cold region. Attached Figure Description

[0052] Figure 1 This is a schematic diagram showing the configuration of the exhaust gas purification catalyst device manufactured in Example 1.

[0053] Figure 2 This is a schematic diagram showing the configuration of the exhaust gas purification catalyst device manufactured in Example 2.

[0054] Figure 3 This is a schematic diagram showing the configuration of the exhaust gas purification catalyst device manufactured in Example 3.

[0055] Figure 4 This is a schematic diagram showing the configuration of the exhaust gas purification catalyst device manufactured in Example 4.

[0056] Figure 5 This is a schematic diagram showing the configuration of the exhaust gas purification catalyst device manufactured in Example 5.

[0057] Figure 6 This is a schematic diagram showing the configuration of the exhaust gas purification catalyst device manufactured in Example 6.

[0058] Figure 7 This is a schematic diagram showing the configuration of the exhaust gas purification catalyst device manufactured in Example 7.

[0059] Figure 8 This is a schematic diagram showing the configuration of the exhaust gas purification catalyst device manufactured in Comparative Example 1. Detailed Implementation

[0060] <Exhaust gas purification catalyst device>

[0061] The exhaust gas purification catalyst device of the present invention,

[0062] It is an exhaust gas purification catalyst device having a substrate and a catalyst coating on the substrate.

[0063] The catalyst coating is a single layer or a laminate consisting of two or more layers.

[0064] The uppermost layer of the catalyst coating, starting from the upstream side of the exhaust flow, sequentially comprises an upper layer zone 1 containing Pd, an upper layer zone 2 containing Rh, and an upper layer zone 3 containing Rh.

[0065] The Rh concentration in the upper second zone is higher than the Rh concentration in the upper third zone.

[0066] In the exhaust gas purification catalyst device of the present invention, the uppermost layer of the catalyst coating has, sequentially from the upstream side of the exhaust flow, an upper first zone containing Pd, an upper second zone containing Rh, and an upper third zone containing Rh, wherein the Rh concentration in the upper second zone is set to be higher than the Rh concentration in the upper third zone.

[0067] The exhaust gas purification catalyst device of the present invention contains Pd in ​​the uppermost first zone on the uppermost upstream side, thus improving the HC purification capacity in the cold region. In addition, by containing Rh in the upper second and upper third zones located downstream of the first zone, HC can be thoroughly purified.

[0068] Furthermore, in the exhaust gas purification catalyst device of the present invention, the high concentration of Rh contained in the upper second zone enhances the NOx purification capacity in the cold zone. In addition, to supplement the purification of NOx escaping from the upper second zone in the high-speed zone, an upper third zone containing Rh is also provided downstream of the upper second zone. Here, since most of the NOx is purified in the upper second zone, the Rh concentration in the upper third zone can be low.

[0069] In the exhaust gas purification catalyst device of the present invention, through the above-mentioned mechanism of action, the amount of precious metals used in the catalyst is suppressed while reducing HC emissions and NOx emissions in the cold zone.

[0070] However, this invention is not subject to any specific theoretical constraints.

[0071] In a preferred embodiment of the exhaust gas purification catalyst device of the present invention, the catalyst coating is a laminate consisting of two layers, wherein the lower layer of the catalyst coating sequentially comprises a lower first zone containing Rh and a lower second zone containing one or two of Pd and Pt from the upstream side of the exhaust flow.

[0072] The constituent elements of the exhaust gas purification catalyst device of the present invention will be described in turn below.

[0073] <Substrate>

[0074] The substrate in the exhaust gas purification catalyst device of the present invention can be a substrate having multiple pore flow paths divided by partitions, or it can be a honeycomb substrate used in prior art exhaust gas purification catalyst devices. The partitions of the substrate may or may not have fine pores that fluidly connect adjacent exhaust flow paths.

[0075] The substrate can be made of refractory inorganic oxides such as cordierite, or it can be a metal. The substrate can be either direct-flow or wall-flow type.

[0076] The substrate in the exhaust gas purification catalyst device of the present invention can typically be, for example, a direct-flow monolithic honeycomb substrate made of cordierite, a wall-flow monolithic honeycomb substrate made of cordierite, a metal honeycomb substrate, etc.

[0077] The substrate can be cylindrical, elliptical, polygonal, or similar shapes.

[0078] The capacity of the substrate is expressed as an apparent volumetric measure of base area × length, for example, it can be 500 mL or more, 800 mL or more, 1.0 L or more, or 1.2 L or more, for example, it can be less than 5.0 L, less than 3.0 L, less than 2.0 L, less than 1.5 L or less.

[0079] <Catalyst Coating>

[0080] The exhaust gas purification catalyst device of the present invention has a catalyst coating on a substrate.

[0081] The catalyst coating in the exhaust gas purification catalyst device of the present invention can be a single layer or a laminate composed of two or more layers.

[0082] (Top layer)

[0083] The top layer of the catalyst coating in the exhaust gas purification catalyst device has, in sequence from the upstream side of the exhaust flow: an upper layer zone 1 containing Pd, an upper layer zone 2 containing Rh, and an upper layer zone 3 containing Rh.

[0084] The term "top layer" in catalyst coating refers to the single layer when the catalyst coating is a single layer, and to the layer located at the position furthest from the surface of the unit flow path of the substrate and having a surface that is in direct contact with the exhaust gas flow when the catalyst coating is a laminate consisting of two or more layers.

[0085] The length of the top layer can typically be the same as the length of the substrate.

[0086] -Upper Level, Section 1-

[0087] The upper first zone is mainly helpful for purifying HC, especially for purifying cold HC.

[0088] To achieve this purpose, the upper first layer contains Pd. In addition to Pd, the upper first layer may also contain inorganic oxide particles, binders, etc.

[0089] The Pd concentration in the upper first zone, as the Pd mass per unit capacity of the substrate (converted to metal), can be 0.5 g / L or higher, 1.0 g / L or higher, 1.2 g / L or higher, 1.4 g / L or higher, or 1.6 g / L or higher, and can be below 5.0 g / L, 4.0 g / L or lower, 3.0 g / L or lower, or 2.0 g / L or lower. If the Pd concentration is within this range, good cold HC purification capability can be ensured without excessively increasing the amount of Pd used.

[0090] The upper first layer may or may not contain catalyst noble metals other than Pd. Examples of catalyst noble metals other than Pd include platinum (Pt) and rhodium (Rh). The upper first layer may substantially not contain catalyst noble metals other than Pd. The amount of catalyst noble metals other than Pd in ​​the upper first layer may be less than 5% by mass, less than 3% by mass, less than 1% by mass, less than 0.5% by mass, less than 0.3% by mass, or less than 0.1% by mass, or the upper first layer may be completely free of catalyst noble metals other than Pd.

[0091] 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, silicon dioxide, titanium dioxide, zirconium dioxide, cerium dioxide, and rare earth metal oxides other than cerium dioxide, and may be selected from one or more of these. When containing two or more inorganic oxide particles, it 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.

[0092] The upper first zone may contain particles of one or more inorganic oxides selected from alumina and aluminum (Al)-containing composite oxides. The Al-containing composite oxides may be composite oxides containing rare earth metal elements other than Al and Ce, and in particular, may be composite oxides containing Al and rare earth metal elements selected from lanthanum (La), praseodymium (Pr), yttrium (Y), neodymium (Nd), etc.

[0093] The upper first layer may substantially be free of inorganic oxide particles selected from cerium dioxide and Ce-containing composite oxides. That is, the upper first layer may substantially be free of Ce. By substantially being free of Ce in the upper first layer, the oxidation catalytic activity of Pd, which is conducive to HC purification, is efficiently demonstrated. The Ce concentration in the upper first layer, as the mass per unit capacity of the substrate converted to cerium dioxide, may be less than 1.0 g / L, less than 0.5 g / L, less than 0.3 g / L, or less than 0.1 g / L, or the upper first layer may be completely free of cerium dioxide and Ce-containing composite oxides.

[0094] The particle size of inorganic oxide particles in the upper first zone can be, for example, greater than 3 μm and less than 8 μm.

[0095] The amount of inorganic oxide particles in the upper first zone, and the mass of inorganic oxide particles per unit volume of the substrate, can 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, or for example, 100 g / L or less, 80 g / L or less, 70 g / L or less, or 60 g / L or less.

[0096] The Pd in ​​the upper first region can be in particle form, and can be supported on inorganic oxide particles in the form of Pd particles. The particle size of the Pd particles supported on the inorganic oxide particles can be, for example, greater than 1 nm and less than 15 nm.

[0097] The inorganic oxide particles carrying Pd in ​​the upper first zone can be, for example, one or more selected from alumina and Al-containing composite oxides.

[0098] The adhesive in the upper first zone can be, for example, boehm adhesive, alumina sol, silica sol, etc.

[0099] To ensure a sufficiently high cold HC purification capacity, the length of the upper first zone can be more than 5%, 10%, 15%, 20%, 25%, or 30% of the total upper length. To maintain the lengths of the upper second and third zones, which are conducive to cold NOx purification, the length of the upper first zone can be less than 50%, 45%, 40%, or 35% of the total upper length.

[0100] -Upper Level, Section 2-

[0101] The upper second zone mainly helps with NOx purification, especially effective for purifying cold NOx.

[0102] To achieve this purpose, the upper second layer contains Rh. In addition to Rh, the upper second layer may also contain inorganic oxide particles, binders, etc.

[0103] The Rh concentration in the upper second zone, as the Rh mass per unit capacity of the substrate converted to metal, can be above 0.05 g / L, above 0.10 g / L, above 0.15 g / L, above 0.20 g / L, or above 0.25 g / L, or below 0.50 g / L, below 0.40 g / L, below 0.35 g / L, or below 0.30 g / L. If the Rh concentration is within this range, good cold NOx purification capacity can be ensured without excessively increasing the amount of Rh used.

[0104] The upper second layer may or may not contain catalyst noble metals other than Rh. Examples of catalyst noble metals other than Rh include Pt and Pd. The upper second layer may be implemented without catalyst noble metals other than Rh. The amount of catalyst noble metals other than Rh in the upper second layer may be less than 5% by mass, less than 3% by mass, less than 1% by mass, less than 0.5% by mass, less than 0.3% by mass, or less than 0.1% by mass, or the upper second layer may be completely free of catalyst noble metals other than Rh.

[0105] The upper second layer may contain inorganic oxide particles. The inorganic oxide particles in the upper second layer may be appropriately selected from the substances exemplified above, which are the inorganic oxide particles in the upper first layer.

[0106] The upper second zone may contain particles of one or more inorganic oxides selected from cerium dioxide, Ce-containing composite oxides, aluminum oxide, and Al-containing composite oxides (except for those containing Ce).

[0107] Ce-containing composite oxides can be composite oxides containing Ce and one or two inorganic elements selected from zirconium (Zr) and Al, or composite oxides that also contain rare earth metal elements other than Ce. Specifically, examples of Ce-containing composite oxides include Ce-Zr composite oxides, Al-Ce-Zr composite oxides, and composite oxides that also contain rare earth metal elements other than Ce.

[0108] Examples of Al-containing composite oxides include composite oxides containing Al and Zr, as well as composite oxides containing rare earth metal elements other than Ce.

[0109] In the above, rare earth metal elements other than Ce can be selected from, for example, La, Pr, Y, Nd, etc.

[0110] The upper second layer may contain particles of inorganic oxides selected from cerium dioxide and composite oxides containing Ce. The Ce concentration in the upper second layer, as the mass of the substrate per unit volume converted to cerium dioxide, 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 may be 12.0 g / L or less, 10.0 g / L 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 upper second layer may not contain Ce.

[0111] The particle size of inorganic oxide particles in the upper second zone can be, for example, greater than 3 μm and less than 8 μm.

[0112] The amount of inorganic oxide particles in the upper second zone, as the mass of inorganic oxide particles per unit volume of the substrate, can 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, or for example, 150 g / L or less, 120 g / L or less, 100 g / L or less, or 80 g / L or less.

[0113] --The carrier of Rh in the upper second zone--

[0114] The Rh in the upper second region can be in particle form, and can be supported on inorganic oxide particles in the form of Rh particles. The particle size of the Rh particles supported on the inorganic oxide particles can be, for example, greater than 1 nm and less than 15 nm.

[0115] In another embodiment of the present invention, at least a portion of Rh in the upper second region is supported by inorganic oxide particles containing Ce. These Ce-containing inorganic oxide particles may be, for example, cerium dioxide, Ce-Zr composite oxides, Al-Ce-Zr composite oxides, etc.

[0116] In another embodiment of the present invention, at least a portion of the Rh contained in the upper second region is supported on inorganic oxide particles that are substantially free of Ce. These inorganic oxide particles that are substantially free of Ce may be, for example, alumina, Al-Zr composite oxides, etc.

[0117] In another embodiment of the invention, at least a portion of the Rh in the upper second region is supported by inorganic oxide particles containing Ce, and the upper second region also includes inorganic oxide particles that are substantially free of Ce. These inorganic oxide particles that are substantially free of Ce may not support Rh.

[0118] In another embodiment of the present invention, at least a portion of the Rh contained in the upper second region is supported on inorganic oxide particles that are substantially free of Ce, and the upper second region also contains inorganic oxide particles containing Ce. These Ce-containing inorganic oxide particles may not be supported on Rh.

[0119] The adhesive in the upper second zone can be, for example, boehmite adhesive, alumina sol, silica sol, etc.

[0120] To ensure a sufficiently high cold NOx purification capacity, the length of the upper second zone can be more than 5%, 7%, 10%, 12%, or 15% of the length of the upper layer. To maintain the lengths of the upper first and upper third zones, the length of the upper second zone can be less than 30%, 28%, 25%, 23%, or 20% of the length of the upper layer. The upper first zone helps with cold HC purification, and the upper third zone helps with the purification of NOx that was not completely purified in the upper second zone.

[0121] -Upper Level, Section 3-

[0122] The upper third zone is mainly helpful for NOx purification, especially for the purification of cold NOx that was not completely purified in the upper second zone.

[0123] To achieve this purpose, the upper third zone contains Rh. In addition to Rh, the upper third zone may also contain inorganic oxide particles, binders, etc.

[0124] The Rh concentration in the upper third zone, as the Rh mass per unit volume of the substrate converted to metal, can be above 0.05 g / L, above 0.07 g / L, above 0.10 g / L, above 0.11 g / L, or above 0.13 g / L, or below 0.50 g / L, below 0.40 g / L, below 0.30 g / L, below 0.20 g / L, less than 0.20 g / L, or below 0.15 g / L. If the Rh concentration is within this range, the NOx purification capacity can be further improved without excessively increasing the amount of Rh used.

[0125] The Rh concentration in the upper third zone can 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.

[0126] The upper third zone may or may not contain catalyst noble metals other than Rh. Examples of catalyst noble metals other than Rh include Pt and Pd. The upper third zone may be substantially free of catalyst noble metals other than Rh. The amount of catalyst noble metals other than Rh in the upper third zone may be less than 5% by mass, less than 3% by mass, less than 1% by mass, less than 0.5% by mass, less than 0.3% by mass, or less than 0.1% by mass, or the upper third zone may be free of catalyst noble metals other than Rh.

[0127] The upper third zone may contain inorganic oxide particles. As inorganic oxide particles in the upper third zone, appropriate selections can be made from the inorganic oxide particles in the upper first zone, using the substances exemplified above.

[0128] The upper third zone may contain particles of one or more inorganic oxides selected from cerium dioxide, Ce-containing composite oxides, aluminum oxide, and Al-containing composite oxides (except for those containing Ce). Here, the same composite oxides as those in the upper second zone can be used as examples of Ce-containing composite oxides and Al-containing composite oxides.

[0129] The upper third layer preferably contains particles of inorganic oxides selected from cerium dioxide and composite oxides containing Ce. The Ce element concentration in the upper third layer, as the mass of the substrate per unit capacity converted to cerium dioxide, can 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 can 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.

[0130] The Ce element concentration in the upper third zone can be higher than that in the upper second zone. In one embodiment of the present invention, the Ce element concentration converted from cerium dioxide in the upper third zone is 5.0 g / L or more and 15.0 g / L or less, the Ce element concentration converted from cerium dioxide 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 that in the upper second zone.

[0131] The particle size of inorganic oxide particles in the upper third zone can be, for example, greater than 3 μm and less than 8 μm.

[0132] The amount of inorganic oxide particles in the upper third zone is measured by the mass of inorganic oxide particles per unit volume of the substrate. For example, it can be 50 g / L or more, 60 g / L or more, 70 g / L or more, or 80 g / L or more, or it can be 200 g / L or less, 150 g / L or less, 120 g / L or less, or 100 g / L or less.

[0133] --The carrier of Rh in the upper third zone--

[0134] The Rh particles in the upper third region can be in particle form, and can be supported on inorganic oxide particles. The particle size of the Rh particles supported on the inorganic oxide particles can be, for example, greater than 1 nm and less than 15 nm.

[0135] In one embodiment of the present invention, at least a portion of Rh in the upper third region is supported by inorganic oxide particles containing Ce.

[0136] In another embodiment of the invention, at least a portion of the Rh in the upper third region is supported by inorganic oxide particles containing Ce, and the upper second region further comprises inorganic oxide particles that are substantially free of Ce. These substantially Ce-free inorganic oxide particles may not support Rh.

[0137] The adhesive in the upper third zone can be, for example, boehmite adhesive, alumina sol, silica sol, etc.

[0138] To ensure a sufficiently high NOx purification capacity, the length of the upper third zone can be more than 20%, 30%, 35%, 40%, or 45% of the length of the upper layer. To maintain the lengths of the upper first and second zones, the length of the upper third zone can be less than 90%, 80%, 70%, or 60% of the length of the upper layer. The upper first zone is conducive to cold HC purification, and the upper second zone is conducive to cold NOx purification.

[0139] (Lower level)

[0140] The catalyst coating of the exhaust gas purification catalyst device of the present invention can be a single-layer structure having only the uppermost layer described above, or it can be a laminate consisting of two layers having a lower layer between the substrate and the uppermost layer described above.

[0141] The lower layer of the catalyst coating, starting from the upstream side of the exhaust flow, may, for example, sequentially have:

[0142] The lower zone 1 containing Rh; and

[0143] It contains a lower second zone selected from one or two of Pd and Pt.

[0144] The length of the lower layer can typically be the same as the length of the substrate.

[0145] -Lower Level, Section 1-

[0146] The lower zone 1 contains Rh, which helps purify HC and NOx during the cold zone to preheating process. Rh has high catalytic activity in the cold zone, and the catalyst coating temperature rises from the upstream side of the exhaust flow during preheating. Therefore, the Rh-containing lower zone 1 makes a significant contribution to the purification of HC and NOx during the cold zone to preheating process.

[0147] The composition of the lower layer 1 can be appropriately selected from the range described above, which is the composition of the upper layer 2. The composition of the lower layer 1 can also be the same as the composition of the upper layer 2.

[0148] To ensure a sufficiently high purification effect of HC and NOx, the length of the lower first zone can be more than 10%, 15%, 20%, 25%, or 30% of the length of the lower layer. To maintain the length of the lower second zone, which is conducive to HC removal, the length of the lower first zone can be less than 60%, 50%, 45%, 40%, or 30% of the length of the lower layer.

[0149] -Lower Level, Section 2-

[0150] The lower second zone contains one or two of Pt and Pd. The lower second zone, through the high oxidizing activity of one or two of Pt and Pd, helps to purify (remove) HC that was not completely purified in the upper and lower first zones under high load.

[0151] To achieve this purpose, the lower first layer contains one or two of Pd and Pt. In addition to Pd and Pt, the lower first layer may also contain inorganic oxide particles, binders, etc.

[0152] The concentration of one or two of Pd and Pt in the lower second zone, as the total mass of Pd and Pt per unit volume of the substrate (converted to metal), can be 0.1 g / L or higher, 0.3 g / L or higher, 0.5 g / L or higher, 0.6 g / L or higher, or 0.8 g / L or higher, and can be below 3.0 g / L, below 2.5 g / L, below 2.0 g / L, below 1.8 g / L, below 1.5 g / L, or below 1.5 g / L. If the concentration is within this range, good HC purification capacity can be ensured without excessively increasing the amount of Pd and Pt used.

[0153] The lower second zone may or may not contain catalyst noble metals other than Pd and Pt. Examples of catalyst noble metals other than Pd and Pt include rhodium (Rh). The lower second zone may be substantially free of catalyst noble metals other than Pd and Pt. The amount of catalyst noble metals other than Pd and Pt in the lower second zone may be less than 5% by mass, less than 3% by mass, less than 1% by mass, less than 0.5% by mass, less than 0.3% by mass, or less than 0.1% by mass relative to the total mass of catalyst noble metals in the upper first zone, or the upper first zone may be completely free of catalyst noble metals other than Pd and Pt.

[0154] The lower second layer may contain inorganic oxide particles. The inorganic oxide particles in the lower second layer may be appropriately selected from the substances exemplified above, which are the inorganic oxide particles in the upper first layer.

[0155] The lower second zone may contain particles of one or more inorganic oxides selected from alumina and Al-containing composite oxides (except those containing Ce). Here, the same composite oxide as the one in the upper first zone can be used as an example of an Al-containing composite oxide.

[0156] The lower second layer may contain particles of inorganic oxides selected from cerium dioxide and composite oxides containing Ce. The Ce concentration in the lower second layer, as the mass of the substrate per unit volume converted to cerium dioxide, may be 10 g / L or more, 20 g / L or more, 30 g / L or more, or 40 g / L or more, or less than 100 g / L, 80 g / L or less, 70 g / L or less, or 60 g / L or less.

[0157] The particle size of the inorganic oxide particles in the lower second zone can be, for example, greater than 3 μm and less than 8 μm.

[0158] The amount of inorganic oxide particles in the lower second layer, measured by the mass of inorganic oxide particles per unit volume of the substrate, can be, for example, 10 g / L or more, 20 g / L or more, or 30 g / L or more, or, for example, 80 g / L or less, 70 g / L or less, 60 g / L or less, or 50 g / L or less.

[0159] The Pd and Pt in the lower second region can be in particle form, and can be supported on inorganic oxide particles in the form of Pd particles and Pt particles. The particle size of the Pd particles and Pt particles supported on the inorganic oxide particles can be, for example, greater than 1 nm and less than 15 nm.

[0160] The adhesive in the lower second zone can be, for example, boehmite adhesive, alumina sol, silica sol, etc.

[0161] To ensure a sufficiently high HC purification capacity, the length of the second lower zone can be more than 40%, 45%, 50%, 55%, or 60% of the length of the lower zone. In particular, to maintain the length of the first lower zone, which is conducive to the purification of HC and NOx in the cold zone, the length of the second lower zone can be less than 90%, 85%, 80%, 75%, 70%, or 60% of the length of the lower zone.

[0162] (3rd floor)

[0163] The catalyst coating of the exhaust gas purification catalyst device of the present invention may optionally have layers other than the uppermost and lowermost layers described above. Examples of layers other than the uppermost and lowermost layers include layers with adsorption functions for HC, NH3, NOx, etc., and layers with purification functions for HC, NOx, etc.

[0164] In one embodiment, the catalyst coating does not have layers other than the topmost and bottommost layers.

[0165] <Relative component concentration ratio between layers>

[0166] -Rh concentration-

[0167] The Rh concentration in the lower zone 1 can be substantially the same as the Rh concentration in the upper zone 2. "Substantially the same Rh concentration in the lower zone 1 as in the upper zone 2" means that the Rh concentration in the lower zone 1 is 0.90 times, 0.95 times, or 0.98 times higher than the Rh concentration in the upper zone 2, and less than 1.10 times, 1.05 times, or 1.02 times higher, respectively.

[0168] The Rh concentration (Rh mass per unit volume of the substrate) in the upper second layer can be higher than that in the upper third layer (Rh mass per unit volume of the substrate). The Rh concentration in the upper second layer can be more than 1.5 times, more than 2.0 times, more than 2.5 times, or more than 3.0 times the Rh concentration in the upper third layer, or it can be less than 4.0 times, less than 3.5 times, less than 3.0 times, or less than 2.5 times the Rh concentration in the upper third layer.

[0169] Furthermore, the amount of Rh contained in the exhaust gas purification catalyst device of the present invention, based on the total mass of Rh per unit capacity of the substrate, can be 0.1 g / L or more, 0.2 g / L or more, 0.3 g / L or more, 0.4 g / L or more, or less than 1.0 g / L, less than 0.8 g / L, less than 0.6 g / L or less than 0.5 g / L.

[0170] -Ce concentration-

[0171] The Ce element concentration in the lower layer, zone 1, can be substantially the same as the Ce element concentration in the upper layer, zone 2. "Substantially the same Ce element concentration in the lower layer, zone 1, and upper layer 2" means that the Ce element concentration in the lower layer, zone 1, and upper layer 2 is 0.90 times, 0.95 times, or 0.98 times higher than the Ce element concentration in the upper layer, and less than 1.10 times, 1.05 times, or 1.02 times higher, respectively.

[0172] The Ce concentration in the upper second zone can be the same as or lower than that in the upper third zone. By having a lower Ce concentration in the upper second zone than in the upper third zone, the catalytic activity of Rh on the upstream side of the exhaust gas flow in the cold zone can be improved. Therefore, this provides an advantage for the purification of HC and NOx in the cold zone.

[0173] The Ce element concentration (equivalent mass of cerium dioxide per unit capacity of the substrate) in the upper layer 2 zone can be less than 1.0 times, 0.8 times, 0.6 times, 0.5 times, 0.4 times, or 0.3 times that of the Ce element concentration (equivalent mass of cerium dioxide per unit capacity of the substrate) in the upper layer 3 zone.

[0174] In one embodiment of the present invention, the upper second region does not contain Ce elements, and the upper third region contains Ce elements.

[0175] Furthermore, the Ce concentration in the lower second zone can be higher than that in the upper third zone. If the Ce concentration in the lower second zone is higher than that in the upper third zone, it is possible to achieve the advantage of maintaining NOx purification capacity at high loads while also exhibiting effective OSC capacity.

[0176] The Ce element concentration (equivalent mass of cerium dioxide per unit capacity of the substrate) in the lower layer 2 zone can be more than 2.0 times, 3.0 times, 4.0 times, 5.0 times, or 6.0 times that of the Ce element concentration (equivalent mass of cerium dioxide per unit capacity of the substrate) in the upper layer 3 zone, or it can be less than 12.0 times, less than 10.0 times, less than 8.0 times, or less than 7.0 times.

[0177] Furthermore, as mentioned above, the upper zone 1 can be substantially free of Ce. That is, the Ce concentration in each zone can be in the order of (upper zone 1) < (lower zone 1 ≈ upper zone 2) < (upper zone 3) < (lower zone 2). This concentration order means that the Ce concentration on the upstream side of the exhaust flow is lower than the Ce concentration on the downstream side. Therefore, in the exhaust purification catalyst device of the present invention, the low-temperature purification activity on the upstream side of the catalyst coating is relatively higher.

[0178] <Manufacturing Method of Exhaust Gas Purification Catalyst Device>

[0179] The exhaust gas purification catalyst device of the present invention can be manufactured by various methods as long as it has the above-described structure.

[0180] As a non-limiting example, an example of a method for manufacturing an exhaust gas purification catalyst device is described, wherein the catalyst coating is a two-layer stack consisting of an uppermost layer and a lower layer, and the composition of the upper second layer is the same as that of the lower first layer.

[0181] Such an exhaust gas purification catalyst device can be manufactured, for example, by sequentially forming zones of predetermined length on a substrate. The formation order of the zones can be, for example, any of the following.

[0182] The order of lower level zone 2, upper level zone 3, lower level zone 1, upper level zone 2, and upper level zone 1;

[0183] The order of lower level zone 2, lower level zone 1, upper level zone 2, upper level zone 3, and upper level zone 1; or

[0184] The order is: Lower Zone 2, Lower Zone 1, Upper Zone 2, Upper Zone 1, and Upper Zone 3.

[0185] In the above, the lower first zone and the upper second zone can be formed simultaneously.

[0186] The formation of each zone can be carried out by applying a coating solution prepared according to the expected zone composition, drying it as needed (removing the solvent), and then firing it. Firing can be carried out according to the formation of each zone, or it can be carried out all at once after all zones have been coated.

[0187] The application solution can be a liquid composition containing the components or precursors contained in the intended area, and a solvent. For example, the application solution may contain the following components.

[0188] One or more inorganic oxide particles, a noble metal precursor, and optional components as needed, and a solvent (first coating solution); or

[0189] Inorganic oxide particles carrying precious metal particles, other inorganic oxide particles as needed, optional components as needed, and solvent (second coating solution).

[0190] It is believed that when the first coating solution contains two or more inorganic oxide particles and a noble metal precursor, the noble metal particles are entirely supported on the two or more inorganic oxide particles. However, it is believed that when the coating solution is prepared by contacting the first inorganic oxide particle to be supported on the noble metal particles and the noble metal precursor in a solvent, and then adding the second inorganic oxide particle, most of the noble metal particles will be supported on the first inorganic oxide particle.

[0191] The inorganic oxide particles carrying precious metal particles in the second coating solution can be manufactured according to known methods.

[0192] The application, drying, and firing of the coating solution can be carried out according to known methods.

[0193] <Exhaust Gas Purification Methods>

[0194] According to another aspect of the present invention, an exhaust gas purification method is provided.

[0195] The exhaust purification method of the present invention includes the following steps: in the exhaust system of an internal combustion engine, the exhaust purification catalyst device of the present invention is arranged in the upper first zone facing the upstream side of the exhaust flow to purify the exhaust gas discharged from the internal combustion engine.

[0196] Internal combustion engines can be, for example, gasoline engines, diesel engines, and hybrid engines in automobiles.

[0197] Example

[0198] <Preparation of the coating solution for forming the upper first zone>

[0199] Palladium nitrate (equivalent to 1.745 g / L of metallic Pd as a PGM (platinum group metals) source), alumina (equivalent to 80 g / L of inorganic oxide particles), and boehmite binder (equivalent to 4 g / L of binder) are added to pure water and stirred thoroughly to prepare the coating solution for forming the upper first zone.

[0200] <Preparation of the coating solution for forming the lower second zone>

[0201] Platinum nitrate (equivalent to 1.085 g / L of metallic Pt as the PGM source), alumina (equivalent to 40 g / L of inorganic oxide particles), and boehmite binder (equivalent to 5.0 g / L of binder) are added to pure water and stirred thoroughly to prepare the coating solution for forming the lower layer of Zone 2.

[0202] <Preparation of coating liquid (1) for forming the lower layer 1 and upper layer 2>

[0203] Rhodium nitrate (equivalent to 0.279 g / L of metallic Rh as a PGM source) and Al-Zr composite oxide (Al2O3:ZrO2 = 30:60 (mass ratio), AZ) (equivalent to 30.0 g / L) were added to pure water and stirred at room temperature for at least 30 minutes. Then, alumina (equivalent to 35.0 g / L) and Al-Ce-Zr composite oxide (equivalent to 10.0 g / L, ACZ) (equivalent to 30:20:42 (mass ratio), ACZ) were added sequentially, and then boehmite binder (equivalent to 3.0 g / L) was added as a binder. The mixture was stirred thoroughly to prepare the coating solution (1) for forming the lower zone 1 and the upper zone 2.

[0204] <Preparation of coating solutions (2) to (5) for forming the lower layer 1 and upper layer 2>

[0205] By changing the amount of rhodium nitrate and the amount of ACZ, the amount of metal Rh and CeO2 in the coating solution are adjusted to the values ​​recorded in Table 1. Otherwise, the coating solutions (2) to (5) for forming the lower layer 1 and the upper layer 2 are prepared in the same way as the above-mentioned "Preparation of coating solution (1) for forming the lower layer 1 and the upper layer 2".

[0206] <Preparation of the coating solution (6) for forming the lower layer 1 and the upper layer 2>

[0207] ACZ was not used. In addition, the coating liquid (6) for forming the lower layer 1 and the upper layer 2 was prepared in the same manner as the above-mentioned "Preparation of coating liquid (1) for forming the lower layer 1 and the upper layer 2".

[0208] <Preparation of the coating liquid (7) for forming the lower layer 1 and the upper layer 2>

[0209] Add rhodium nitrate (equivalent to 0.279 g / L of metallic Rh and ACZ (equivalent to 10.0 g / L) as the PGM source to pure water and stir at room temperature for at least 30 minutes. Then, add alumina (equivalent to 35.0 g / L) and boehmite binder (equivalent to 3.0 g / L) as a binder and stir thoroughly to prepare the coating solution (7) for forming the lower zone 1 and the upper zone 2.

[0210] Table 1. Coating solution for forming the lower layer zone 1 and upper layer zone 2

[0211]

[0212] <Preparation of the coating solution for forming the upper third zone>

[0213] The amount of rhodium nitrate added is set to be equivalent to 0.139 g / L of metallic Rh, the amount of ACZ added is set to be equivalent to 45.0 g / L, and the amount of alumina added is set to be equivalent to 35.0 g / L. Otherwise, the coating liquid for forming the upper third zone is prepared in the same way as the above-mentioned "Preparation of coating liquid (7) for forming the lower first zone and the upper second zone".

[0214] <Comparative Example 1: Preparation of the coating solution for forming the lower layer, zone 1>

[0215] The amount of rhodium nitrate added was equivalent to 0.139 g / L of metallic Rh. Otherwise, the coating solution for forming the lower first zone used in Comparative Example 1 was prepared in the same manner as the above-mentioned "Preparation of coating solution (1) for forming the lower first zone and the upper second zone".

[0216] <Comparative Example 1: Preparation of the coating solution for the upper second zone>

[0217] The amount of rhodium nitrate added was set to be equivalent to 0.100 g / L of metallic Rh, and the amount of ACZ added was set to be equivalent to 45.0 g / L. Otherwise, the coating solution for forming the upper second zone used in Comparative Example 1 was prepared in the same manner as the above-mentioned "Preparation of coating solution (7) for forming the lower first zone and the upper second zone".

[0218] Each of the above-mentioned coating solutions, taking into account the coating width, is prepared in an amount such that the concentration of the components in the coated portion is the value described above, while the total amount is applied to a predetermined coating length, and the total amount is then used.

[0219] <Example 1>

[0220] As a substrate, a material with a diameter of 127 mm, a length of 102 mm, an apparent capacity of 1.29 L, and 750 cells / cm² was used. 2 It is a DC-type substrate made of cordierite with a wall thickness of 2.5μm.

[0221] The lower second layer is formed by applying a coating liquid to a region extending 67% of the substrate length from the downstream side of the substrate where the lower second layer is formed, and then firing it at 500°C for 1 hour. Next, the upper third layer is formed by applying a coating liquid to a region extending 50% of the substrate length from the downstream side of the substrate where the lower second layer is formed, and then firing it at 500°C for 1 hour.

[0222] Then, the lower first layer and the upper second layer are formed by coating liquid (1) on a region extending 50% of the length of the substrate from the upstream side of the substrate on which the lower second layer and the upper third layer are formed, and then fired at 500°C for 1 hour to form the lower first layer and the upper second layer. The length of the lower first layer is 33% of the total length of the substrate, and the length of the upper second layer is 17% of the total length of the substrate.

[0223] Finally, the upper first zone forming coating liquid is applied to a region extending 33% of the substrate length from the upstream side of the substrate on which the lower first zone, lower second zone, upper second zone, and upper third zone are formed, and the mixture is fired at 500°C for 1 hour to form the upper first zone, thereby manufacturing the exhaust gas purification catalyst device of Example 1. Figure 1 This shows a general outline of the configuration of the exhaust gas purification catalyst device in Example 1.

[0224] <Examples 2-7>

[0225] The exhaust gas purification catalyst devices of Examples 2 to 7 were manufactured in the same manner as in Example 1, except that the coating liquids for forming the lower layer 1 and upper layer 2, as indicated in the "Type of Coating Liquid" column of Table 2, were used instead of the coating liquids for forming the lower layer 1 and upper layer 2. Figures 2-7 This indicates a general outline of the composition of these exhaust gas purification catalyst devices.

[0226] <Comparative Example 1>

[0227] As the substrate, a DC-type substrate made of the same type of cordierite as used in Example 1 was used.

[0228] The lower layer second region forming liquid was applied to a region extending 67% of the substrate length from the downstream side of the exhaust flow of the substrate, and then fired at 500°C for 1 hour to form the lower layer second region on the substrate. Next, a modified liquid of the lower layer first region forming liquid used in Comparative Example 1 was applied to a region extending 33% of the substrate length from the upstream side of the substrate on which the lower layer second region was formed, and then fired at 500°C for 1 hour to form the lower layer first region.

[0229] Next, the upper second region forming liquid used in Comparative Example 1 was applied to a region extending 67% of the substrate length from the upstream side of the substrate on which the lower first region and the lower second region were formed, and then fired at 500°C for 1 hour to form the upper second region. Finally, the upper first region forming liquid was applied to a region extending 33% of the substrate length from the upstream side of the substrate on which the lower first region, the lower second region, and the upper second region were formed, and then fired at 500°C for 1 hour to form the upper first region, thereby manufacturing the exhaust gas purification catalyst device of Comparative Example 1. Figure 8 This shows a general outline of the configuration of the exhaust gas purification catalyst device in Comparative Example 1.

[0230] Evaluation of Exhaust Gas Purification Catalyst Devices

[0231] The exhaust purification catalyst devices manufactured above are subjected to durability testing using the following methods to evaluate their exhaust purification capabilities.

[0232] (1) Durable

[0233] The exhaust purification catalyst devices obtained in the above embodiments and comparative examples were installed in the exhaust system of a 2.7L TC (turbocharged) gasoline engine with the upper first zone and the lower first zone located upstream of the exhaust flow. The theoretically balanced atmosphere and lean atmosphere were repeatedly exhausted at predetermined intervals to achieve a durability equivalent to 150,000 miles of driving.

[0234] (2) Evaluation of exhaust purification capacity

[0235] The durable exhaust purification catalyst units were installed on the exhaust system of a TC (turbocharged) car with a 2.7L gasoline engine, with the upper and lower zones 1 positioned upstream of the exhaust flow. The exhaust purification capability was evaluated using the "FTP75" standard. The evaluation results are shown in Tables 2-4.

[0236]

[0237]

[0238] Table 4

[0239]

[0240] The inorganic oxide particles in Tables 2-4 are listed in the order of addition during the preparation of the coating solution.

[0241] The results shown in Tables 2 and 3 verify that the exhaust gas purification catalyst devices according to Examples 1 to 7 of the present invention can suppress NOx emissions compared to the exhaust gas purification catalyst device of Comparative Example 1, which belongs to the prior art.

[0242] In particular, in the exhaust gas purification catalyst devices of Examples 1 to 5, which verified that the Ce element concentration in the upper second zone was lower than that in the upper third zone, Bag 1 (sampling bag 1) which corresponds to cold start, Bag 2 (sampling bag 2) which corresponds to transition period, and Bag 3 (sampling bag 3) which corresponds to high speed driving, all were able to suppress NOx emissions.

Claims

1. An exhaust gas purification catalyst device, comprising a substrate and a catalyst coating on the substrate, The catalyst coating is a single layer or a laminate consisting of two or more layers. The uppermost layer of the catalyst coating, starting from the upstream side of the exhaust flow, sequentially comprises an upper layer zone 1 containing Pd, an upper layer zone 2 containing Rh, and an upper layer zone 3 containing Rh. The Rh concentration in the upper second zone is higher than the Rh concentration in the upper third zone.

2. The exhaust gas purification catalyst device according to claim 1, The Rh concentration in the upper second zone, calculated as metal, is above 0.20 g / L and below 0.50 g / L. The Rh concentration in the upper third zone, calculated in metal terms, is above 0.05 g / L and below 0.20 g / L.

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

4. The exhaust gas purification catalyst device according to claim 1, The Ce element concentration in the upper second zone is lower than the Ce element concentration in the upper third zone.

5. The exhaust gas purification catalyst device according to claim 1, The Ce element concentration (converted to cerium dioxide) in the upper second zone is below 7.0 g / L, and, The Ce element concentration in the upper third zone, as converted from cerium dioxide, is above 5.0 g / L and below 15.0 g / L.

6. The exhaust gas purification catalyst device according to claim 2, The Ce element concentration (converted to cerium dioxide) in the upper second zone is below 7.0 g / L, and, The Ce element concentration in the upper third zone, as converted from cerium dioxide, is above 5.0 g / L and below 15.0 g / L.

7. The exhaust gas purification catalyst device according to claim 3, The Ce element concentration (converted to cerium dioxide) in the upper second zone is below 7.0 g / L, and, The Ce element concentration in the upper third zone, as converted from cerium dioxide, is above 5.0 g / L and below 15.0 g / L.

8. The exhaust gas purification catalyst device according to any one of claims 1 to 7, At least a portion of the Rh contained in the upper second region is supported on inorganic oxide particles containing Ce. The Rh contained in the upper third region is supported on inorganic oxide particles containing Ce.

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

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

11. The exhaust gas purification catalyst device according to any one of claims 1 to 7, The catalyst coating is a laminate consisting of two layers. The lower layer of the catalyst coating, starting from the upstream side of the exhaust flow, sequentially comprises: The lower zone 1 containing Rh; and It contains a lower second zone selected from one or two of Pd and Pt.

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

13. An exhaust purification method comprising the following steps: in the exhaust system of an internal combustion engine, purifying the exhaust gas discharged from the internal combustion engine by arranging the exhaust purification catalyst device according to any one of claims 1 to 7 in such a manner as if the upper first zone were facing the upstream side of the exhaust flow.

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