Exhaust gas purification catalyst system

Abstract

To provide an exhaust gas purifying catalyst device where an adsorption amount of NOx in a cold region is large and NOx emission in the cold region is reduced.SOLUTION: In an exhaust gas purifying catalyst device having a first catalyst coat layer 200 and a second catalyst coat layer 300 on a base material 100: the first catalyst coat layer 200 contains first inorganic oxide particles 10 and first catalyst noble metal particles 40; the second catalyst coat layer 300 contains second inorganic oxide particles 60 and second catalyst noble metal particles 70; the first inorganic oxide particles 10 contain a composite oxide carrier 30 containing an OSC material 11 and an alkaline earth metal oxide 20; the first catalyst noble metal particles 40 contain one or two kinds selected from Pt and Pd; the second inorganic oxide particles 60 contain the OSC material 11; the second catalyst noble metal particles 70 contain Rh; the first catalyst coat layer 200 does not substantially contain Rh; and the second catalyst coat layer 300 does not substantially contain Pt, Pd and the alkaline earth metal oxide.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] Exhaust gas from internal combustion engines such as automobile engines contains nitrogen oxides (NO , , ), 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, and then released into the atmosphere.

[0003] Regarding the three components of CO, HC, and NOx contained in the exhaust gas, from the perspective of alleviating air pollution, etc., in each country, the emission weight per unit driving distance of automobiles is regulated.

[0004] Exhaust gas regulations are being strengthened year by year. Currently, in the United States, the LEV III regulation is applied, and in Europe, the Euro 6 regulation is applied. In Europe, it is considered that the Euro 7 regulation will be introduced in the near future.

[0005] In the Euro 7 regulation, for example, reduction of NOx emissions in cold regions such as at engine startup is required. The exhaust gas atmosphere at engine startup is in the rich to stoichiometric region. Therefore, it is difficult to reduce NOx emissions in cold regions by the conventional NOx purification technology premised on a lean burn engine.

[0006] As a NOx emission reduction technology in the prior art, for example, in Patent Document 1, 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 The present invention describes an exhaust gas purification catalyst comprising a first composite oxide and a second composite oxide, wherein an alkaline earth metal selected from Ca, Sr, and Mg is in solid solution in at least one of them.

[0007] Patent Document 1 explains that the NOx adsorption properties of a composite oxide are improved by solid solution of an alkaline earth metal into the composite oxide.

[0008] Furthermore, Patent Document 2 describes a redox catalyst comprising palladium and an alkaline earth metal supported on an oxide having oxygen storage and release capabilities.

[0009] Patent Document 2 explains that by configuring the catalyst as described above, alkaline earth metals are preferably involved in the adsorption or reaction of NOx. [Prior art documents] [Patent Documents]

[0010] [Patent Document 1] Japanese Patent Publication No. 2010-119994 [Patent Document 2] Japanese Patent Publication No. 2001-198461 [Overview of the project] [Problems that the invention aims to solve]

[0011] The aforementioned Patent Documents 1 and 2 both belong to the category of conventional exhaust gas purification catalysts, and their NOx adsorption capacity in cold regions such as during engine startup is insufficient.

[0012] The present invention has been made in view of the above circumstances, and aims to provide an exhaust gas purification catalyst device that has a large amount of NOx adsorption in the cold region and reduces NOx emissions in the cold region. [Means for solving the problem]

[0013] The present invention is as follows:

[0014] <Aspect 1> Having a substrate, a first catalyst coating layer on the substrate, and a second catalyst coating layer on the first catalyst coating layer, The first catalyst coating layer comprises first inorganic oxide particles and first catalyst noble metal particles. The second catalyst coating layer comprises second inorganic oxide particles and second catalyst noble metal particles. The first inorganic oxide particles include OSC material and alkaline earth metal oxides. The first catalyst noble metal particles comprises one or two selected from Pt and Pd. The second inorganic oxide particles include OSC material, The second catalyst noble metal particles contain Rh, In the first catalyst coating layer, the amount of Rh in terms of metal per 1 L of substrate volume is 0.05 g / L or less. In the second catalyst coating layer, the total amount of Pt and Pd in ​​terms of metal per liter of substrate is 0.05 g / L or less, and the amount of alkaline earth metal oxide per liter of substrate is 0.5 g / L or less. Exhaust gas purification catalyst device. <Aspect 2> The first inorganic oxide particles are A composite oxide carrier containing OSC material and a first alkaline earth metal oxide, A second alkaline earth metal oxide is supported on the composite oxide carrier, including, Exhaust gas purification catalyst device according to Embodiment 1. <Aspect 3> The exhaust gas purification catalyst apparatus according to aspect 2, wherein at least a portion of the first catalyst noble metal particles is supported on the composite oxide carrier together with the second alkaline earth metal oxide. <Aspect 4> The exhaust gas purification catalyst device according to aspect 2 or 3, wherein the first alkaline earth metal oxide is magnesium oxide. "Aspect 5": The exhaust gas purification catalyst device according to any one of Aspects 2 to 4, wherein the second alkaline earth metal oxide is one or more selected from the group consisting of magnesium oxide, barium oxide, and strontium oxide. "Aspect 6": The exhaust gas purification catalyst device according to any one of Aspects 2 to 5, wherein the amount of the first alkaline earth metal oxide is 0.1% by mass or more and 20% by mass or less when the total mass of the composite oxide carrier is 100% by mass. "Aspect 7": The exhaust gas purification catalyst device according to any one of Aspects 2 to 6, wherein the supported amount of the second alkaline earth metal oxide is 0.5% by mass or more and 25% by mass or less when the total mass of the composite oxide carrier is 100% by mass. "Aspect 8": The exhaust gas purification catalyst device according to any one of Aspects 2 to 7, wherein the amount of the first catalytic noble metal particles per liter of the volume of the base material is 0.5 g / L or more and 10.0 g / L or less. "Aspect 9": The exhaust gas purification catalyst device according to any one of Aspects 2 to 8, wherein the first inorganic oxide particles further contain alumina. "Aspect 10": The exhaust gas purification catalyst device according to any one of Aspects 1 to 9, wherein the amount of the second catalytic noble metal particles per liter of the volume of the base material is 0.05 g / L or more and 2.0 g / L or less. "Aspect 11": The exhaust gas purification catalyst device according to any one of Aspects 1 to 10, wherein the second inorganic oxide particles further contain alumina. "Aspect 12": The exhaust gas purification catalyst device according to any one of Aspects 1 to 11, wherein the OSC material contains ceria in the cerium-zirconium composite oxide. " "Aspect 13": The exhaust gas purification catalyst device according to any one of Aspects 1 to 12, wherein the first catalytic noble metal particles contain both Pt and Pd. "Aspect 14": The exhaust gas purification catalyst device according to any one of Aspects 1 to 13, wherein the coating length of the first catalyst coating layer is 35% or more of the total length of the base material. "Aspect 15": The exhaust gas purification catalyst device according to any one of Aspects 1 to 14, wherein the coating length of the second catalyst coating layer is 70% or more of the total length of the base material. An exhaust gas purification method including contacting exhaust gas with the exhaust gas purification catalyst device according to any one of Aspects 1 to 15.

Advantages of the Invention

[0015] The exhaust gas purification catalyst device of the present invention has a large NOx adsorption amount in the cold region and reduces NOx emissions in the cold region.

Brief Description of the Drawings

[0016] [Figure 1] FIG. 1 is a conceptual diagram for explaining an example of the configuration of the exhaust gas purification catalyst device of the present invention.

Embodiments for Carrying Out the Invention

[0017] 《《Exhaust Gas Purification Catalyst Device》》 The exhaust gas purification catalyst device of the present invention has a substrate, a first catalyst coat layer on the substrate, and a second catalyst coat layer on the first catalyst coat layer, the first catalyst coat layer contains first inorganic oxide particles and first catalyst noble metal particles, the second catalyst coat layer contains second inorganic oxide particles and second catalyst noble metal particles, the first inorganic oxide particles contain an OSC material and an alkaline earth metal oxide, the first catalyst noble metal particles contain one or two selected from Pt and Pd, the second inorganic oxide particles contain an OSC material, the second catalyst noble metal particles contain Rh, in the first catalyst coat layer, the amount of Rh in terms of metal per 1 L of the substrate volume is 0.05 g / L or less, in the second catalyst coat layer, the total amount of Pt and Pd in terms of metal per 1 L of the substrate volume is 0.05 g / L or less, and the amount of the alkaline earth metal oxide per 1 L of the substrate volume is 0.5 g / L or less.

[0018] The exhaust gas purification catalyst device of the present invention has a lower catalyst coating layer, which is a first catalyst coating layer, and an upper catalyst coating layer, on a substrate.

[0019] The first catalyst coating layer contains an OSC material, an alkaline earth metal oxide, and first catalyst noble metal particles selected from Pt and Pd.

[0020] The exhaust gas atmosphere at engine startup (cold state) is in the rich to stoichiometric range. Therefore, OSC materials such as ceria are in a reduced state and are thought to have oxygen deficiencies at engine startup. In the exhaust gas purification catalyst device of the present invention, the first catalyst coating layer contains an OSC material that has oxygen deficiencies at engine startup, thereby increasing the number of NOx adsorption sites at cold state.

[0021] Furthermore, the first catalyst coating layer contains alkaline earth metal oxides. This increases the amount of basic sites in the first catalyst coating layer, thereby increasing the number of NOx adsorption sites.

[0022] Furthermore, the first catalyst coating layer contains first catalyst noble metal particles selected from Pt and Pd. Since these first catalyst noble metal particles have an oxidation catalytic function, they convert NOx into, for example, NO3. - It is converted into ions to facilitate NOx adsorption to base sites.

[0023] Furthermore, the first catalyst coating layer is substantially free of Rh. As a result, the catalytic activity of the first catalyst noble metal particles (Pd, Pt) in the first catalyst coating layer is not impaired, and a high level of NOx adsorption capacity is achieved.

[0024] Furthermore, the first catalyst coat is positioned in the lower layer of the exhaust gas purification catalyst device of the present invention. Therefore, the first catalyst coat is less likely to warm up during engine startup, etc., and can exert its NOx adsorption capacity as described above very effectively.

[0025] NOx adsorbed on the first catalytic coating is gradually released as the engine warms up after starting.

[0026] Here, the second catalyst coating layer contains OSC material and second catalyst noble metal particles, which are Rh.

[0027] The second catalytic precious metal particles contained in the second catalytic coating layer have a reducing catalytic function. Therefore, NOx released from the first catalytic coating is reduced and purified by the second catalytic precious metal particles in the second catalytic coating layer. Furthermore, the second catalytic coating layer contains OSC material. Therefore, even if the exhaust gas atmosphere fluctuates, the exhaust gas atmosphere is mitigated by the OSC material, allowing the second catalytic precious metal particles to maintain their reducing catalytic activity.

[0028] Furthermore, the second catalyst coating layer is substantially free of Pt, Pd, and alkaline earth metal oxides. As a result, the NOx reduction and purification activity of the second catalyst noble metal particles (Rh) in the second catalyst coating layer is not impaired, and a high level of NOx purification performance is achieved.

[0029] Furthermore, the second catalytic coat is positioned on top of the exhaust gas purification catalyst device of the present invention. Therefore, the second catalytic coat is quickly warmed up after engine start-up, and can exert its NOx reduction and purification ability very effectively.

[0030] The exhaust gas purification catalyst of the present invention exhibits excellent NOx removal performance through the mechanism of action described above. However, the present invention is not bound by any particular theory.

[0031] The components of the exhaust gas purification catalyst device of the present invention will be described in order below.

[0032] 《Base material》 The substrate used in the exhaust gas purification catalyst device of the present invention may be the same as the substrate used in exhaust gas purification catalyst devices. The substrate may be, for example, a honeycomb substrate having a plurality of exhaust gas flow paths partitioned by partition walls. The partition walls of the substrate may have pores that allow fluid communication between adjacent exhaust gas flow paths.

[0033] The constituent material of the substrate may be, for example, a refractory inorganic oxide such as cordierite. The substrate may be of the straight-flow type or the wall-flow type.

[0034] The substrate in the exhaust gas purification catalyst device of the present invention may typically be, for example, a straight-flow or wall-flow monolithic honeycomb substrate made of cordierite.

[0035] 《First catalyst coating layer》 In the exhaust gas purification catalyst device of the present invention, the first catalyst coating layer is disposed on a substrate. Furthermore, a second catalyst coating layer may be disposed on at least a part, preferably all, of the first catalyst coating layer. Therefore, the first catalyst coating layer may be the lower layer of a two-layer catalyst coating layer.

[0036] The first catalyst coating layer comprises first inorganic oxide particles and first catalyst noble metal particles.

[0037] <First type of inorganic oxide particle> The first inorganic oxide particles contained in the first catalyst coating layer include OSC material and alkaline earth metal oxides. "OSC" is an abbreviation for "Oxygen Storage Capacity" or "Oxygen Storage / release Capacity," meaning "oxygen absorption and release capacity." "OSC material" means "a material that has oxygen absorption and release capacity."

[0038] The OSC material contained in the first inorganic oxide particles is, for example, ceria (CeO2). The concept of ceria as an OSC material includes cases where it exists as a single species of ceria in the first inorganic oxide particles, as well as cases where it constitutes a composite oxide of cerium and other metals.

[0039] If the OSC material is ceria and constitutes a composite oxide of cerium and another metal, the composite oxide may be, for example, a cerium-zirconium composite oxide. When ceria is present as ceria in the cerium-zirconium composite oxide, the amount of oxygen vacancies of the ceria in the rich-stoichiometric region is increased, which further increases the number of NOx adsorption sites of the first inorganic oxide particles in the cold state.

[0040] The ceria content in a cerium-zirconium composite oxide may be 5% by mass or more, 10% by mass or more, 15% by mass or more, or 20% by mass or more, as a percentage of the total mass of the composite oxide, where the mass of cerium atoms in the composite oxide expressed in terms of ceria (Ce2O3) is 5% by mass or more, 10% by mass or more, 15% by mass or more, or 20% by mass or more, and may be 50% by mass or less, 45% by mass or less, 40% by mass or less, 35% by mass or less, 30% by mass or less, or 25% by mass or less.

[0041] The alkaline earth metal oxide contained in the first inorganic oxide particles may be one or more selected from beryllium oxide, magnesium oxide, calcium oxide, strontium oxide, barium oxide, and radium oxide, and in particular, one or more selected from magnesium oxide, calcium oxide, strontium oxide, and barium oxide.

[0042] The first inorganic oxide particles may contain other components in addition to the OSC material and alkaline earth metal oxides. Other components contained in the first inorganic oxide particles include, for example, alumina, silica, titania, etc.; and one or more rare earth oxides selected from oxides of rare earth elements other than ceria.

[0043] The amount of OSC material (typically ceria) contained in the first inorganic oxide particles may be 5% by mass or more, 7.5% by mass or more, or 15% by mass or more, when the total mass of the first inorganic oxide particles is taken as 100% by mass, in order to ensure a sufficient number of NOx adsorption sites when cold. On the other hand, the amount of OSC material contained in the first inorganic oxide particles may be 50% by mass or less, 45% by mass or less, 40% by mass or less, 35% by mass or less, 30% by mass or less, 25% by mass or less, or 20% by mass or less, when the total mass of the first inorganic oxide particles is taken as 100% by mass, in order to enjoy the benefits of the first inorganic oxide particles containing other components.

[0044] Furthermore, the amount of OSC material (typically ceria) in the first catalyst coating layer may be 3.0 g / L or more, 4.0 g / L or more, 5.0 g / L or more, or 6.0 g / L or more, as the mass of OSC material per 1 L of substrate volume, and may be 20.0 g / L or less, 15.0 g / L or less, 12.0 g / L or less, 11.0 g / L or less, or 10.0 g / L or less.

[0045] When ceria is used as an OSC material, if ceria constitutes a composite oxide with other metals, the amount of ceria is the amount of cerium atoms in the composite oxide expressed in terms of ceria (CeO2).

[0046] The amount of alkaline earth metal oxide in the first inorganic oxide particles may be 1% by mass or more, 3% by mass or more, 5% by mass or more, 8% by mass or more, 10% by mass or more, 12% by mass or more, 15% by mass or more, or 20% by mass or more, when the mass of the first inorganic oxide particles is taken as 100% by mass. It may also be 50% by mass or less, 40% by mass or less, 35% by mass or less, 30% by mass or less, or 25% by mass or less.

[0047] Furthermore, the amount of alkaline earth metal oxide in the first catalyst coating layer may be 3.0 g / L or more, 3.5 g / L or more, 4.0 g / L or more, 4.5 g / L or more, 5.0 g / L or more, or 5.5 g / L or more, as the mass of alkaline earth metal oxide per 1 L of substrate volume, and may be 15.0 g / L or less, 12.0 g / L or less, 10.0 g / L or less, 9.0 g / L or less, 8.0 g / L or less, or 7.5 g / L or less.

[0048] The first inorganic oxide particles in the exhaust gas purification catalyst device of the present invention are A composite oxide carrier containing OSC material and a first alkaline earth metal oxide, A second alkaline earth metal oxide is supported on this composite oxide support, It may include.

[0049] The composite oxide support contains an OSC material and a first alkaline earth metal oxide.

[0050] The OSC material contained in the composite oxide carrier may be of the same type as the OSC material contained in the first inorganic oxide particles as described above. The OSC material content in the composite oxide carrier may be 5% by mass or more, 7.5% by mass or more, 15% by mass or more, or 20% by mass or more, and may be 50% by mass or less, 45% by mass or less, 40% by mass or less, 35% by mass or less, 30% by mass or less, or 25% by mass or less, when the total mass of the composite oxide carrier is taken as 100% by mass.

[0051] The first alkaline earth metal oxide contained in the composite oxide support may be one or more selected from, for example, magnesium oxide, calcium oxide, and strontium oxide, and may be magnesium oxide in particular.

[0052] The first alkaline earth metal oxide may exist in the composite oxide carrier as a single type of alkaline earth metal oxide, or it may form a solid solution with an OSC material or a composite oxide containing an OSC material (for example, a cerium-zirconium composite oxide).

[0053] The amount of the first alkaline earth metal oxide contained in the composite oxide support may be 0.1% by mass or more, 0.5% by mass or more, 1.0% by mass or more, 2.0% by mass or more, 3.0% by mass or more, or 4.0% by mass or more, when the total mass of the composite oxide support is 100% by mass, from the viewpoint of sufficiently increasing the number of NOx adsorption sites of the composite oxide support. On the other hand, in order to enjoy the benefits of the composite oxide containing other components, the amount of the first alkaline earth metal oxide may be 20% by mass or less, 15% by mass or less, 12% by mass or less, 10% by mass or less, or 8% by mass or less, when the total mass of the composite oxide support is 100% by mass.

[0054] Furthermore, the amount of the first alkaline earth metal oxide in the first catalyst coating layer may be 0.1 g / L or more, 0.2 g / L or more, 0.3 g / L or more, 0.5 g / L or more, 0.7 g / L or more, 1.0 g / L or more, 1.5 g / L or more, or 2.0 g / L or more, as the mass of the first alkaline earth metal oxide per 1 L of substrate volume, and may be 10.0 g / L or less, 8.0 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, or 2.0 g / L or less.

[0055] When the first alkaline earth metal oxide forms a solid solution with an OSC material or a composite oxide containing an OSC material, the amount of the first alkaline earth metal oxide is the amount of the first alkaline earth metal in the solid solution expressed in terms of oxide.

[0056] The composite oxide carrier may further contain components other than the OSC material and the first alkaline earth metal oxide.

[0057] As described above, the OSC material in the composite oxide support may exist, for example, as ceria in the cerium-zirconium composite oxide, so the composite oxide support may contain zirconia. The amount of zirconia in the composite oxide support may be 20% by mass or more, 30% by mass or more, 40% by mass or more, 50% by mass or more, 60% by mass or more, or 65% by mass or more, when the total mass of the composite oxide support is taken as 100% by mass. On the other hand, in order to enjoy the benefits of the composite oxide support containing other components, the amount of the first alkaline earth metal oxide may be 90% by mass or less, 85% by mass or less, 80% by mass or less, 75% by mass or less, or 70% by mass or less, when the total mass of the composite oxide support is taken as 100% by mass.

[0058] Furthermore, the amount of zirconia in the first catalyst coating layer may be 10.0 g / L or more, 12.0 g / L or more, 15.0 g / L or more, 17.0 g / L or more, or 20.0 g / L or more, as the mass of zirconia per 1 L of substrate volume, and may be 70.0 g / L or less, 60.0 g / L or less, 50.0 g / L or less, 40.0 g / L or less, or 30.0 g / L or less.

[0059] When zirconium constitutes a composite oxide with other metals, the amount of zirconia is the amount of zirconium atoms in the composite oxide expressed in terms of zirconia (ZrO2).

[0060] Furthermore, the composite oxide support may contain one or more oxides selected from alumina, silica, titania, and other rare earth elements other than ceria. When the composite oxide support contains two or more of these, these two or more oxides may exist as single oxides or as a composite oxide containing two or more metal atoms.

[0061] The second alkaline earth metal oxide is supported on the composite oxide support described above.

[0062] The second alkaline earth metal oxide may be one or more selected from the group consisting of magnesium oxide, barium oxide, and strontium oxide. In particular, the second alkaline earth metal oxide may be barium oxide or strontium oxide.

[0063] The second alkaline earth metal oxide may be particulate. The particle size of the second alkaline earth metal oxide particles may be 5 nm or more, 10 nm or more, 15 nm or more, 20 nm or more, or 25 nm or more, as a number average of the primary particle size calculated from XRD, and may be 50 nm or less, 45 nm or less, 40 nm or less, or 35 nm or less.

[0064] The amount of the second alkaline earth metal oxide supported may be 0.5% by mass or more, 1.0% by mass or more, 2.0% by mass or more, 3.0% by mass or more, 4.0% by mass or more, 5.0% by mass or more, or 6.0% by mass or more, when the mass of the composite oxide support is set to 100% by mass, from the viewpoint of ensuring a sufficient amount of NOx adsorption.

[0065] However, increasing the amount of the second alkaline earth metal oxide does not mean that the amount of NOx adsorbed will increase indefinitely. From this perspective, the amount of the second alkaline earth metal oxide supported may be 25% by mass or less, 20% by mass or less, 15% by mass or less, 12% by mass or less, 10% by mass or less, or 8% by mass or less, when the mass of the composite oxide support is taken as 100% by mass.

[0066] The amount of first inorganic oxide particles in the first catalyst coating layer may be 5.0 g / L or more, 10.0 g / L or more, 20.0 g / L or more, 30.0 g / L or more, 50.0 g / L or more, or 60.0 g / L or more, as the mass of first inorganic oxide particles per 1 L of substrate volume, and may be 200.0 g / L or less, 150.0 g / L or less, 120.0 g / L or less, 100.0 g / L or less, or 80.0 g / L or less.

[0067] <Other ingredients> The first catalyst coating layer may contain other components in addition to the first inorganic oxide particles described above. These other components may be, for example, inorganic oxide particles other than the first inorganic oxide particles, a binder, and so on.

[0068] The inorganic oxide particles other than the first inorganic oxide particles may be, for example, one inorganic oxide selected from alumina, silica, titania, zirconia, etc., or a composite oxide composed of two or more of these, or a composite oxide of these inorganic oxides or composite oxides with one or more rare earth elements selected from oxides other than ceria.

[0069] The first inorganic oxide particles are preferable in terms of heat resistance of the exhaust gas purification catalyst if they contain alumina. The alumina content in the first inorganic oxide particles may be 10% by mass or more, 20% by mass or more, 30% by mass or more, 40% by mass or more, or 50% by mass or more, when the total mass of the first inorganic oxide particles is taken as 100% by mass, and may be 90% by mass or less, 80% by mass or less, 70% by mass or less, 60% by mass or less, or 50% by mass or less.

[0070] The amount of alumina in the first catalyst coating layer may be 5.0 g / L or more, 10.0 g / L or more, 20.0 g / L or more, 30.0 g / L or more, 50.0 g / L or more, or 60.0 g / L or more, as the mass of alumina per 1 L of substrate volume, and may be 200.0 g / L or less, 150.0 g / L or less, 120.0 g / L or less, 100.0 g / L or less, or 80.0 g / L or less.

[0071] <First catalyst noble metal particles> The first catalyst coating layer contains first catalyst noble metal particles along with first inorganic oxide particles. These first catalyst noble metal particles include one or two selected from Pt and Pd, and in particular may include both Pt and Pd.

[0072] The amount of the first catalyst noble metal particles in the first catalyst coating layer may be 0.5 g / L or more, 0.7 g / L or more, 1.0 g / L or more, 2.0 g / L or more, 3.0 g / L or more, or 4.0 g / L or more, as the mass of the first catalyst noble metal particles per 1 L of substrate volume (total mass if multiple types of noble metals are included), and may be 10.0 g / L or less, 8.0 g / L or less, 7.0 g / L or less, 6.0 g / L or less, or 5.0 g / L or less.

[0073] In the first catalyst coating layer, the amount of Rh in terms of metal per liter of substrate is 0.05 g / L or less. Having an Rh content of 0.05 g / L or less in the first catalyst coating layer means that the first catalyst coating layer is substantially Rh-free. By substantially free of Rh in the first catalyst coating layer, the reduction in activity due to alloying between the first catalyst noble metal particles and Rh can be suppressed.

[0074] The amount of Rh in metal equivalent per liter of substrate volume in the first catalyst coating layer may be 0.03 g / L or less, 0.01 g / L or less, 0.005 g / L or less, 0.003 g / L or less, or 0.001 g / L or less, or the first catalyst coating layer may not contain any Rh at all.

[0075] The first catalyst noble metal particles in the first catalyst coating layer may be supported on the first inorganic oxide particles.

[0076] The first catalyst noble metal particles in the first catalyst coating layer may be supported on the first inorganic oxide particles.

[0077] When the first catalyst coating layer contains inorganic oxide particles other than the first inorganic oxide particles along with the first inorganic oxide particles, the first catalyst noble metal particles may be supported on either the first inorganic oxide particles or the inorganic oxide particles other than the first inorganic oxide particles, or on both.

[0078] When the first catalyst noble metal particles are supported on the first inorganic oxide particles, at least a portion of the first catalyst noble metal particles are supported on the composite oxide support together with the second alkaline earth metal oxide.

[0079] <Coat length of the first catalyst coating layer> The coating length of the first catalyst coating layer may be 35% or more, 50% or more, 60% or more, 70% or more, 80% or more, 90% or more, or 95% or more of the total length of the substrate, from the viewpoint of ensuring a sufficient amount of NOx adsorption, or the first catalyst coating layer may be arranged over the entire length of the substrate.

[0080] When the coating length of the first catalyst coating layer is shorter than the total length of the substrate, it is desirable to position the first catalyst coating layer as far upstream of the exhaust gas flow as possible on the substrate, from the viewpoint of bringing the first catalyst coating layer into contact with the exhaust gas as quickly as possible to contribute to NOx adsorption, and it is preferable that the upstream end of the first catalyst coating layer coincides with the upstream end of the substrate.

[0081] 《Second catalyst coating layer》 In the exhaust gas purification catalyst device of the present invention, the second catalyst coating layer is disposed on the first catalyst coating layer. Furthermore, the first catalyst coating layer may be disposed beneath at least a portion, preferably all, of the second catalyst coating layer. Therefore, the second catalyst coating layer may be the upper layer of a two-layer catalyst coating layer. When the first catalyst coating layer is not disposed beneath the second catalyst coating layer, that portion of the second catalyst coating layer may be disposed directly on the substrate.

[0082] This second catalyst coating layer contains second inorganic oxide particles and second catalyst noble metal particles.

[0083] <Second type of inorganic oxide particle> The second set of inorganic oxide particles includes OSC material.

[0084] The OSC material contained in the second inorganic oxide particles is, for example, ceria (CeO2). The concept of ceria as an OSC material includes cases where it exists as a single species of ceria in the second inorganic oxide particles, as well as cases where it constitutes a composite oxide of cerium and other metals.

[0085] When the OSC material is ceria and constitutes a composite oxide of cerium and another metal, the composite oxide may be, for example, a cerium-zirconium composite oxide. When ceria exists as ceria in a cerium-zirconium composite oxide, it can exist metastable even if the amount of oxygen vacancies in the ceria increases, thereby increasing the atmospheric relaxation ability of the ceria.

[0086] The OSC material content in the second inorganic oxide particles may be 5% by mass or more, 7.5% by mass or more, 15% by mass or more, or 20% by mass or more, when the total mass of the second inorganic oxide particles is taken as 100% by mass, and may be 50% by mass or less, 45% by mass or less, 40% by mass or less, 35% by mass or less, 30% by mass or less, or 25% by mass or less.

[0087] Furthermore, the amount of OSC material (typically ceria) in the second catalyst coating layer may be 3.0 g / L or more, 4.0 g / L or more, 5.0 g / L or more, 6.0 g / L or more, or 8.0 g / L or more, as the mass of OSC material per 1 L of substrate volume, and may be 20.0 g / L or less, 15.0 g / L or less, 12.0 g / L or less, 11.0 g / L or less, or 10.0 g / L or less.

[0088] <Other ingredients> The second inorganic oxide particles contained in the second catalyst coating layer may contain other components in addition to the second inorganic oxide particles described above. These other components may be, for example, inorganic oxide particles other than the second inorganic oxide particles, a binder, etc.

[0089] The inorganic oxide particles other than the second inorganic oxide particles may be, for example, one inorganic oxide selected from alumina, silica, titania, zirconia, etc., or a composite oxide composed of two or more of these, or a composite oxide of these inorganic oxides or composite oxides with one or more rare earth elements selected from oxides other than ceria.

[0090] The second inorganic oxide particles are preferable in terms of heat resistance of the exhaust gas purification catalyst if they contain alumina. The alumina content in the second inorganic oxide particles may be 20% by mass or more, 30% by mass or more, 40% by mass or more, 50% by mass or more, or 60% by mass or more, and may be 90% by mass or less, 80% by mass or less, 70% by mass or less, or 60% by mass or less, when the total mass of the second inorganic oxide particles is taken as 100% by mass.

[0091] The amount of alumina in the second catalyst coating layer may be 10.0 g / L or more, 20.0 g / L or more, 30.0 g / L or more, 50.0 g / L or more, 60.0 g / L or more, or 70.0 g / L or more, as the mass of alumina per 1 L of substrate volume, and may be 200.0 g / L or less, 150.0 g / L or less, 120.0 g / L or less, 100.0 g / L or less, or 80.0 g / L or less.

[0092] <Second catalyst: precious metal particles> The second catalyst coating layer contains second catalyst noble metal particles along with second inorganic oxide particles. These second catalyst noble metal particles contain Rh.

[0093] The amount of second catalyst noble metal particles in the second catalyst coating layer may be 0.03 g / L or more, 0.05 g / L or more, 0.06 g / L or more, 0.08 g / L or more, 0.10 g / L or more, or 0.12 g / L or more, as the mass of first catalyst noble metal particles per 1 L of substrate volume (total mass if multiple types of noble metals are included), and may be 2.0 g / L or less, 1.5 g / L or less, 1.00 g / L or less, 0.50 g / L or less, 0.30 g / L or less, 0.20 g / L or less, 0.18 g / L or less, or 0.15 g / L or less.

[0094] In the second catalyst coating layer, the total amount of Pt and Pd in ​​terms of metal per liter of substrate is 0.05 g / L or less. A total amount of Pt and Pd in ​​the second catalyst coating layer of 0.05 g / L or less means that the second catalyst coating layer is substantially free of Pt and Pd. The substantially free content of Pt and Pd in ​​the second catalyst coating layer improves the NOx reduction and purification capacity.

[0095] The total amount of Pt and Pd in ​​metal equivalent per liter of substrate volume in the first catalyst coating layer may be 0.03 g / L or less, 0.01 g / L or less, 0.005 g / L or less, 0.003 g / L or less, or 0.001 g / L or less, or the second catalyst coating layer may not contain any Pt or Pd at all.

[0096] The second catalyst noble metal particles in the second catalyst coating layer may be supported on the second inorganic oxide particles.

[0097] The second catalyst noble metal particles in the second catalyst coating layer may be supported on the second inorganic oxide particles.

[0098] When the second catalyst coating layer contains inorganic oxide particles other than the second inorganic oxide particles along with the second inorganic oxide particles, the second catalyst noble metal particles may be supported on either the second inorganic oxide particles or the inorganic oxide particles other than the second inorganic oxide particles, or on both.

[0099] <Amount of alkaline earth metal oxides in the second catalyst coating layer> In the second catalyst coating layer, the amount of alkaline earth metal oxide per liter of substrate volume is 0.5 g / L or less. Having 0.5 g / L or less of alkaline earth metal oxide in the second catalyst coating layer means that the second catalyst coating layer is substantially free of alkaline earth metal oxide. By substantially free of alkaline earth metal oxide in the second catalyst coating layer, the decrease in Rh's NOx reduction and purification activity due to the interaction between Rh and alkaline earth metal oxide can be suppressed.

[0100] The amount of alkaline earth metal oxide per liter of substrate volume in the second catalyst coating layer may be 0.3 g / L or less, 0.01 g / L or less, 0.05 g / L or less, 0.03 g / L or less, or 0.01 g / L or less, or the second catalyst coating layer may not contain any alkaline earth metal oxide at all.

[0101] <Coat length of the second catalyst coating layer> The coating length of the second catalyst coating layer may be 70% or more, 75% or more, 80% or more, 85% or more, 90% or more, or 95% or more of the total length of the substrate, from the viewpoint of ensuring sufficient NOx reduction and purification capacity, or the second catalyst coating layer may be arranged over the entire length of the substrate.

[0102] When the coating length of the second catalyst coating layer is shorter than the total length of the substrate, from the viewpoint of ensuring contact with NOx released from the first catalyst coating layer, it is desirable to position the second catalyst coating layer as far downstream of the exhaust gas flow as possible on the substrate, and it is preferable that the downstream end of the second catalyst coating layer coincides with the downstream end of the substrate.

[0103] 《Specific Examples of Exhaust Gas Purification Catalyst System Configurations》 Figure 1 shows an example of the configuration of the exhaust gas purification catalyst device of the present invention.

[0104] The exhaust gas purification catalyst device shown in Figure 1 comprises a substrate (100), a first catalyst coating layer (200) on the substrate (100), and a second catalyst coating layer (300) on the first catalyst coating layer (200).

[0105] The first catalyst coating layer (200) includes first inorganic oxide particles (10) and first catalyst noble metal particles (40), and may further include other inorganic oxide particles (50) other than the first inorganic oxide particles (10).

[0106] The first inorganic oxide particles (10) contain an OSC material (11) and an alkaline earth metal oxide (20). The first inorganic oxide particles (10) also contain a composite oxide carrier (30) and a second alkaline earth metal oxide (22) supported on the composite oxide carrier (30). The composite oxide carrier (30) contains the OSC material (11) and the first alkaline earth metal oxide (21), and may optionally contain other components (12).

[0107] The first catalyst precious metal particles (40) in the first catalyst coating layer (200) include one or two selected from Pt and Pd. These first catalyst precious metal particles (40) are supported on the first inorganic oxide particles (10), and may also be supported on other inorganic oxide particles (50).

[0108] In other words, the first catalyst coating layer (200) is, in one embodiment, A composite oxide carrier (30) comprising OSC material (11) and a first alkaline earth metal oxide (21), Other inorganic oxide particles (50) and Includes, The composite oxide support (30) has a first catalyst noble metal particle (40) and a second alkaline earth metal oxide (22) supported on it. The other inorganic oxide particles (50) have the first catalyst noble metal particles (40) supported on them.

[0109] Furthermore, the first catalyst coating layer (200) is substantially Rh-free.

[0110] The second catalyst coating layer (300) includes second inorganic oxide particles (60) and second catalyst noble metal particles (70), and may further include other inorganic oxide particles (80) other than the second inorganic oxide particles (60).

[0111] The second inorganic oxide particles (60) contain the OSC material (11). These second inorganic oxide particles (60) contain the OSC material (11) and may optionally contain other components (13).

[0112] The second catalyst noble metal particles (70) in the second catalyst coating layer (300) contain Rh. These second catalyst noble metal particles (70) are supported on the second inorganic oxide particles (60), and may also be supported on other inorganic oxide particles (80).

[0113] In other words, the second catalyst coating layer (300) is, in one embodiment, A second inorganic oxide particle (60) containing OSC material (11), Other inorganic oxide particles (80) and Includes, The second inorganic oxide particles (60) and other inorganic oxide particles (80) are supported with the second catalyst noble metal particles (70).

[0114] Furthermore, the second catalyst coating layer (300) is substantially free of Pd, Pt, and alkaline earth metal oxides.

[0115] Method for manufacturing an exhaust gas purification catalyst device The exhaust gas purification catalyst device of the present invention may be manufactured by any method, as long as it has the above-described configuration.

[0116] The exhaust gas purification catalyst device of the present invention is, for example, Forming a first catalyst coating layer on a substrate containing first inorganic oxide particles and first catalyst noble metal particles (first catalyst coating layer formation step), and Forming a second catalyst coating layer on a substrate on which the first catalyst coating layer has been formed (second catalyst coating layer formation step) It may be manufactured by a method that includes [a certain component].

[0117] Hereinafter, as a typical example of the exhaust gas purification catalyst device of the present invention, we will describe the manufacturing process of the exhaust gas purification catalyst device shown in Figure 1 above.

[0118] <First catalyst coating layer formation process> The first catalyst coating layer formation step may be carried out, for example, by coating a substrate with the first catalyst coating layer forming coating liquid and firing it. After coating and before firing, the coating layer may be dried as needed.

[0119] The substrate may be appropriately selected and used according to the desired configuration of the exhaust gas purification catalyst device. The substrate may be, for example, a straight-flow or wall-flow monolithic honeycomb substrate made of cordierite.

[0120] In the exhaust gas purification catalyst device shown in Figure 1, the first catalyst coating layer (200) is, in one embodiment, A composite oxide carrier (30) comprising OSC material (11) and a first alkaline earth metal oxide (21), Other inorganic oxide particles (50) and Includes, The composite oxide support (30) has a first catalyst noble metal particle (40) and a second alkaline earth metal oxide (22) supported on it. The other inorganic oxide particles (50) have the first catalyst noble metal particles (40) supported on them.

[0121] The first catalyst coating liquid for forming such a first catalyst coating layer (200) may be a liquid composition containing a composite oxide support (30), other inorganic oxide particles (50), a precursor of a first catalyst noble metal particle (40), and a precursor of a second alkaline earth metal oxide (22), with other components optionally dissolved or suspended in a suitable solvent.

[0122] The composite oxide support (30) may be produced, for example, by a coprecipitation method. Specifically, it may be produced by adding a suitable precipitating agent to a liquid mixture (preferably an aqueous solution) containing a precursor of the OSC material (11), a precursor of the first alkaline earth metal oxide (21), and, if necessary, precursors of any other components, drying and calcining the precipitate obtained, and then grinding and classifying it.

[0123] The precursors for the OSC material (11), the first alkaline earth metal oxide (21), and the precursors for the optional components may be nitrates, sulfates, hydrochlorides, acetates, etc., of the desired metal, respectively. The precipitating agent may be an alkali, such as sodium hydroxide, potassium hydroxide, or ammonium hydroxide, and may be used as a solution of these, preferably an aqueous solution.

[0124] The drying and calcination of the precipitate, and the grinding and classification of the calcined product, may be carried out by known methods or by methods thereon with appropriate modifications by those skilled in the art.

[0125] The precursor of the first catalyst noble metal particles (40) and the precursor of the second alkaline earth metal oxide (22) may be nitrates, sulfates, hydrochlorides, acetates, etc. of the desired metal, respectively. Other components may be, for example, binders. The solvent may be, for example, water, a mixture of water and a water-soluble organic solvent, and is typically water.

[0126] The coating of the first catalyst coating layer onto the substrate, as well as the drying and firing after coating, may be carried out according to known methods.

[0127] <Second catalyst coating layer formation process> In the second catalyst coating layer formation step, for example, the second catalyst coating layer is formed on the substrate on which the first catalyst coating layer has been formed as described above.

[0128] In the exhaust gas purification catalyst device shown in Figure 1, the second catalyst coating layer (300) is, in one embodiment, A second inorganic oxide particle (60) containing OSC material (11), Other inorganic oxide particles (80) and Includes, The second inorganic oxide particles (60) and other inorganic oxide particles (80) are supported with the second catalyst noble metal particles (70).

[0129] The second catalyst coating layer forming liquid for forming such a second catalyst coating layer (300) may be a liquid composition containing a precursor of a second inorganic oxide particle (60), other inorganic oxide particles (80), and a second catalyst noble metal particle (70), with other components optionally dissolved or suspended in a suitable solvent.

[0130] The precursor of the second catalyst noble metal particles (70) may be a nitrate, sulfate, hydrochloride, acetate, etc. of the desired metal. Other components may be, for example, a binder. The solvent may be, for example, water, a mixture of water and a water-soluble organic solvent, and is typically water.

[0131] The coating of the second catalyst coating layer, as well as the drying and firing after coating, may be carried out according to known methods.

[0132] Exhaust gas purification methods The exhaust gas purification catalyst device of the present invention is suitable as a catalyst device for purifying exhaust gas emitted from engines of automobiles and the like. When using the exhaust gas purification catalyst device of the present invention, NOx emissions are effectively reduced even in cold conditions such as immediately after engine startup, when the exhaust gas contains NOx.

[0133] Therefore, according to the present invention, in another aspect, an exhaust gas purification method is provided, which includes contacting exhaust gas with the exhaust gas purification catalyst device of the present invention.

[0134] Bringing the exhaust gas into contact with the exhaust gas purification catalyst of the present invention may be achieved by, for example, placing the exhaust gas purification catalyst of the present invention within the exhaust system of an engine, according to known methods. [Examples]

[0135] Synthesis of Composite Oxide Support 1 Zirconium oxynitrate, cerium nitrate, aluminum nitrate, neodymium nitrate, lanthanum nitrate, and magnesium acetate (a precursor of the first alkali metal oxide (MgO)) were dissolved in pure water in such a mass ratio in terms of oxides as shown below to obtain an acidic mixed solution. Sodium hydroxide aqueous solution was added to this mixed solution until the pH became 7, and a coprecipitation operation was performed to obtain a precipitate. The precipitate was filtered, thoroughly washed with pure water, dried in air at 250°C for 8 hours, and then calcined in air at 500°C for 2 hours to obtain a calcined product. The obtained calcined product was crushed in an agate mortar and classified to obtain a powdered composite oxide carrier 1 with a particle size range of 2 to 10 μm.

[0136] The mass ratios of each component in the above composite oxide support 1, in terms of oxides, are as follows: ZrO2: 69.0% by mass CeO2:21.0% by mass Nd2O3: 5.3% by mass La2O3: 1.7% by mass MgO: 3.0% by mass

[0137] Other Oxide Supports Other oxide supports include the following: Composite oxide support 2: A composite oxide support in which the mass ratio of each component in terms of oxide is as follows. ZrO2:66.0% by mass CeO2:21.0% by mass Nd2O3: 5.3% by mass La2O3: 1.7% by mass MgO: 6.0% by mass

[0138] Composite oxide support 3: A composite oxide support in which the mass ratio of each component in terms of oxide is as follows. ZrO2:72.0% by mass CeO2:21.0% by mass Nd2O3: 5.3% by mass La2O3: 1.7% by mass MgO: 0% by mass

[0139] Composite oxide support 4: A composite oxide support (spinel) in which the mass ratio of each component in terms of oxide is as follows. Al2O3:65.0% by mass CeO2: 17.0% by mass La2O3: 2.0% by mass MgO: 16.0% by mass

[0140] Other inorganic oxide particles 1: Cerium-zirconium composite oxide particles containing 40% by mass of CeO2, with trace amounts of Pr2O3 and La2O3 added, and calcined at 800°C for 5 hours. Other inorganic oxide particles 2: La2O3 composite alumina, La2O3 content 4.0% by mass Other inorganic oxide particles 3: Cerium-zirconium composite oxide particles containing 20% ​​by mass of CeO2, with trace amounts of Nd2O3, La2O3, and Y2O3 added, and calcined at 800°C for 5 hours.

[0141] 《Base material》 As the substrate, a cordierite honeycomb substrate with a rectangular prism shape, 600 cells, a total substrate length of 115 mm, a wall thickness of 2 mil (0.0508 mm), and a capacity of 1,259 mL was used.

[0142] Example 1 (1) Preparation of coating solution for Pt-Pd layer formation Palladium nitrate, platinum nitrate, barium sulfate (a precursor of the second alkaline earth metal oxide), the powdered composite oxide carrier 1 obtained in the "Synthesis of Composite Oxide Carrier 1" described above, other inorganic oxide particles 1 and other inorganic oxide particles 2, and an alumina-based binder were added to pure water and thoroughly stirred to obtain a suspension-like coating liquid for forming a Pt-Pd layer.

[0143] The content of each component in the obtained Pt-Pd layer forming coating solution was as follows, expressed as mass per liter of substrate volume: Barium sulfate: 5.0 g / L (calculated as barium oxide) Palladium nitrate: 3.0 g / L (calculated as palladium metal equivalent) Platinum nitrate: 1.39 g / L (equivalent to platinum metal). Composite oxide support 1:40g / L Other inorganic oxide particles 1: 40 g / L Other inorganic oxide particles 2: 40 g / L

[0144] (2) Preparation of coating solution for Rh layer formation By adding rhodium nitrate, other inorganic oxide particles 2, and other inorganic oxide particles 3 to pure water and stirring thoroughly, a suspension-like coating solution for Rh layer formation was obtained.

[0145] The content of each component in the obtained Rh layer forming coating solution was as follows, expressed as mass per liter of substrate volume: Rhodium nitrate: 0.13 g / L (calculated as rhodium metal equivalent) Other inorganic oxide particles 2: 70 g / L Other inorganic oxide particles 3: 50 g / L

[0146] (3) Manufacturing of exhaust gas purification catalysts After pouring the Pt-Pd layer forming coating liquid onto the substrate, any excess was blown away with a blower to coat the entire length of the substrate with the Pt-Pd layer forming coating liquid. The coated substrate was then left to dry for 2 hours in a dryer heated to 120°C, and then fired in an electric furnace at 500°C for 2 hours to form a Pt-Pd layer on the substrate.

[0147] After pouring a coating liquid for Rh layer formation onto a substrate with a Pt-Pd layer formed on it, the excess was blown away with a blower to coat the entire length of the substrate with the coating liquid. The coated substrate was then left to dry for 2 hours in a dryer heated to 120°C, and then fired in an electric furnace at 500°C for 2 hours to form the Rh layer, thereby obtaining an exhaust gas purification catalyst device having a Pt-Pd layer and an Rh layer in that order on the substrate.

[0148] (4) Evaluation The resulting exhaust gas purification catalyst was installed in the exhaust system of a 4,608cc V8 engine, and the durability of the catalyst was tested by repeatedly passing exhaust gas in a stoichiometric atmosphere and a lean atmosphere at predetermined intervals for 50 hours at a catalyst bed temperature of 1,000°C.

[0149] Using the exhaust gas purification catalyst system after durability testing, NOx emissions in the cold zone were measured according to the WLTC driving mode. The reduction rate, with the amount of NOx in the exhaust gas in the cold zone set to 100%, was calculated using the following formula. The results are shown in Table 1. NOx reduction rate (%) = (Amount of NOx in exhaust gas - NOx emissions) / Amount of NOx in exhaust gas × 100

[0150] Examples 2-7, and Comparative Examples 1 and 2 Except for changing the compositions of the coating liquid for forming the Pt-Pd layer and the coating liquid for forming the Rh layer, respectively, an exhaust gas purification catalyst device was manufactured and evaluated in the same manner as in Example 1. The results are shown in Table 1 or Table 2.

[0151] Comparative Example 3 Except for reversing the formation order of the Pt-Pd layer and the Rh layer, an exhaust gas purification catalyst device having the Rh layer and Pt-Pd layer in that order was manufactured on a substrate in the same manner as in Comparative Example 2. The obtained exhaust gas purification catalyst device was evaluated in the same manner as in Example 1. The results are shown in Table 2.

[0152] Comparative Example 4 Except for changing the compositions of the coating liquid for forming the Pt-Pd layer and the coating liquid for forming the Rh layer, respectively, as shown in Table 2, an exhaust gas purification catalyst device was manufactured and evaluated in the same manner as in Comparative Example 3. The results are shown in Table 2.

[0153] [Table 1]

[0154] [Table 2]

[0155] As can be seen from Table 1 above, on the substrate, A composite oxide support containing OSC material, and a first catalyst coating layer containing one or two first catalyst noble metal particles selected from Pt and Pd, A second catalyst coating layer comprising a second inorganic oxide particle and a second catalyst noble metal particle containing Rh, In an exhaust gas purification catalyst device having, When the first catalyst coating layer is placed on the lower layer and the second catalyst coating layer is placed on the upper layer, Comparative Example 1 exhaust gas purification catalyst device, in which both the first catalyst coating layer and the second catalyst coating layer do not contain alkaline earth metal oxides, and Comparative Example 2: Exhaust gas purification catalyst device in which both the first catalyst coating layer and the second catalyst coating layer contain alkaline earth metal oxides. In all cases, the reduction rate of NOx in the exhaust gas in the cold region was insufficient.

[0156] In response to this, The first catalyst coating layer is placed on the lower layer, and the second catalyst coating layer is placed on the upper layer. The first catalyst coating layer contains an alkaline earth metal oxide, and The second catalyst coating layer does not contain a significant amount of alkaline earth metal oxide. Examples 1 to 7 demonstrated a significant reduction in NOx in the exhaust gas in the cold region.

[0157] however, Even if the first catalyst coating layer contains alkaline earth metal oxides and the second catalyst coating layer does not contain alkaline earth metal oxides, The second catalyst coating layer was placed as the lower layer, and the first catalyst coating layer was placed as the upper layer. In Comparative Examples 3 and 4, it was confirmed that the reduction rate of NOx in the exhaust gas in the cold region was insufficient.

[0158] From the above, it has been verified that the exhaust gas purification catalyst device of the present invention exhibits particularly excellent NOx purification performance in the cold region. [Explanation of Symbols]

[0159] 10. First inorganic oxide particles 11 OSC material 12, 13 Other ingredients 20 Alkaline earth metal oxides 21. First alkaline earth metal oxides 22. Second Alkaline Earth Metal Oxides 30. Composite Oxide Supports 40 First catalyst precious metal particles 50, 80 Other inorganic oxide particles 60 Second inorganic oxide particles 70 Second catalyst precious metal particles 100 Base material 200 First catalyst coating layer 300 Second catalyst coating layer

Claims

1. The material comprises a substrate, a first catalyst coating layer on the substrate, and a second catalyst coating layer on the first catalyst coating layer. The first catalyst coating layer comprises first inorganic oxide particles and first catalyst noble metal particles. The second catalyst coating layer comprises second inorganic oxide particles and second catalyst noble metal particles. The first inorganic oxide particles include OSC material and alkaline earth metal oxide. The first catalyst noble metal particles include both Pt and Pd. The first inorganic oxide particles are A composite oxide carrier containing OSC material and a first alkaline earth metal oxide, A second alkaline earth metal oxide is supported on the composite oxide carrier, Includes, The aforementioned composite oxide support OSC material and The first alkaline earth metal oxide, Oxides of rare earth elements other than ceria, Zirconia or alumina Includes, The amount of the first alkaline earth metal oxide is 0.1% by mass or more and 15% by mass or less, when the total mass of the composite oxide carrier is 100% by mass. The second inorganic oxide particles include OSC material, The second catalyst noble metal particles contain Rh, In the first catalyst coating layer, the amount of Rh in terms of metal per liter of substrate is 0.05 g / L or less. In the second catalyst coating layer, the total amount of Pt and Pd in ​​terms of metal per liter of substrate is 0.05 g / L or less, and the amount of alkaline earth metal oxide per liter of substrate is 0.5 g / L or less. Exhaust gas purification catalyst device.

2. The first alkaline earth metal oxide is magnesium oxide, The oxide of a rare earth element other than ceria is selected from neodymium oxide and lanthanum oxide. The exhaust gas purification catalyst device according to claim 1.

3. The exhaust gas purification catalyst apparatus according to claim 1 or 2, wherein at least a portion of the first catalyst noble metal particles is supported on the composite oxide carrier together with the second alkaline earth metal oxide.

4. The exhaust gas purification catalyst device according to any one of claims 1 to 3, wherein the second alkaline earth metal oxide is one or more selected from the group consisting of magnesium oxide, barium oxide, and strontium oxide.

5. The exhaust gas purification catalyst device according to any one of claims 1 to 4, wherein the amount of the second alkaline earth metal oxide supported is 0.5% by mass or more and 25% by mass or less, when the total mass of the composite oxide carrier is 100% by mass.

6. The exhaust gas purification catalyst device according to any one of claims 1 to 5, wherein the amount of the first catalyst noble metal particles per 1 L of the base material is 0.5 g / L or more and 10.0 g / L or less.

7. The exhaust gas purification catalyst apparatus according to any one of claims 1 to 6, wherein the first inorganic oxide particles further comprise alumina.

8. The exhaust gas purification catalyst device according to any one of claims 1 to 7, wherein the amount of the second catalyst noble metal particles per 1 L of the base material is 0.05 g / L or more and 2.0 g / L or less.

9. The exhaust gas purification catalyst apparatus according to any one of claims 1 to 8, wherein the second inorganic oxide particles further contain alumina.

10. The exhaust gas purification catalyst device according to any one of claims 1 to 9, wherein the OSC material contained in at least one of the first inorganic oxide particles and the second inorganic oxide particles contains ceria in a cerium-zirconium composite oxide.

11. The exhaust gas purification catalyst apparatus according to any one of claims 1 to 10, wherein the coating length of the first catalyst coating layer is 35% or more of the total length of the substrate.

12. The exhaust gas purification catalyst apparatus according to any one of claims 1 to 11, wherein the coating length of the second catalyst coating layer is 70% or more of the total length of the substrate.

13. A method for purifying exhaust gas, comprising contacting exhaust gas with an exhaust gas purification catalyst device according to any one of claims 1 to 12.

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