Exhaust gas purification catalyst device for gasoline engines

Abstract

To provide an exhaust gas purification catalyst device for a gasoline engine, which reduces ammonia emissions even in a low temperature state such as at the start of the engine. [Solution] An exhaust gas purification catalyst device for a gasoline engine has a substrate, an NH3 adsorption layer containing a proton-type zeolite, and a PGM layer containing a catalytic precious metal selected from Pd, Pt, and Rh, wherein the proton-type zeolite contained in the NH3 adsorption layer has an average pore diameter of 0.60 nm or less, the NH3 adsorption layer is arranged on the substrate side of the PGM layer and is arranged at a length from the upstream end of the exhaust gas flow of the substrate shorter than the entire length of the substrate, and the PGM layer is arranged at a length from the upstream end of the exhaust gas flow of the substrate longer than the NH3 adsorption layer, the PGM layer has a first PGM layer containing a catalytic precious metal selected from Pd and Pt, and a second PGM layer containing Rh, and the first PGM layer contains ceria.

Description

[Technical field]

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

[0002] The exhaust gases emitted from gasoline engines contain substances such as HC (hydrocarbons), CO (carbon monoxide), and NOx (nitrogen oxides), which are purified by an exhaust gas purification catalyst device installed in the engine's exhaust system before being discharged into the atmosphere.

[0003] As an exhaust gas purification catalytic device, a three-way catalyst capable of purifying all of HC, CO, and NOx is known. For example, Patent Document 1 describes an exhaust gas purification catalyst having a multi-layered alumina layer on a substrate, with rhodium supported on the inner alumina layer and at least one of platinum and palladium supported on the surface alumina layer. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 63-039633 Summary of the Invention [Problem to be solved by the invention]

[0005] In a gasoline engine, when the mixture of gasoline and air is rich, ammonia (NH3) is easily generated by the reduction of NOx by a three-way catalyst. In particular, the amount of ammonia generated tends to be large when the engine is started.

[0006] The generated ammonia can be purified by a three-way catalyst. However, when the engine is started or at other low temperatures before the catalyst is warmed up, the catalyst may not be able to purify all of the generated ammonia, and some of it may be discharged.

[0007] The next EU exhaust gas regulations, "Euro 7," will regulate ammonia emissions not only for large vehicles but also for passenger cars and vans.

[0008] The present invention has been made in view of the above circumstances. An object of the present invention is to provide an exhaust gas purification catalyst device for a gasoline engine, which reduces ammonia emissions even in low temperature conditions such as at the start of the engine. [Means for solving the problem]

[0009] The present invention is as follows.

[0010] Aspect 1: A substrate, an NH3 adsorption layer containing proton type zeolite; a PGM layer containing a catalytic precious metal selected from Pd, Pt, and Rh; An exhaust gas purification catalyst device for a gasoline engine, comprising: The proton-type zeolite contained in the NH3 adsorption layer has an average pore diameter of 0.60 nm or less, The NH3 adsorption layer is is disposed closer to the substrate than the PGM layer; The exhaust gas flow upstream end of the substrate is arranged at a length shorter than the entire length of the substrate, and the PGM layer is disposed at a length longer than the NH3 adsorption layer from the upstream end of the exhaust gas flow of the substrate, the PGM layer comprises a first PGM layer containing a catalytic precious metal selected from Pd and Pt, and a second PGM layer containing Rh; the first PGM layer comprises ceria; Exhaust gas purification catalytic converter. Aspect 2: The exhaust gas purification catalyst device according to aspect 1, wherein the proton type zeolite contains 80 mass% or more of small-ring proton type zeolite, the basic skeleton of which is composed only of rings selected from 4-, 6-, and 8-membered rings, based on the total mass of the proton type zeolite. <Aspect 3> The small ring proton type zeolite is H-ACO, H-AEI, H-AEN, H-AFN, H-AFT, AFX, H-ANA, H-APC, H-APD, H-ATT, H-CDO, H-CHA, H-DDR, H-DFT, H-EAB, H-EDI, H-EPI, H-ERI, H-GIS, H-GOO, H-IHW, H-ITE, H-ITW, H- The catalytic converter according to claim 2, wherein the catalytic converter is one or more selected from the group consisting of LEV, H-LTA, H-KFI, H-MER, H-MON, H-NSI, H-OWE, H-PAU, H-PHI, H-RHO, H-RTH, H-SAT, H-SAV, H-SIV, H-THO, H-TSC, H-UEI, H-UFI, H-VNI, H-YUG, and H-ZON. Aspect 4: The catalyst device for purifying exhaust gas according to aspect 1, wherein the amount of ceria contained in the first PGM layer is 4.0 g / L or more and 45.0 g / L or less, calculated as the mass of ceria per 1 L of substrate volume. Aspect 5: The catalyst device for purifying exhaust gas according to aspect 2, wherein the amount of ceria contained in the first PGM layer is 4.0 g / L or more and 45.0 g / L or less, calculated as the mass of ceria per 1 L of substrate volume. Aspect 6: The first PGM layer is a top layer that is in direct contact with the exhaust gas over a length of 10% or more of the entire length of the substrate from the upstream end of the exhaust gas flow of the substrate, and The second PGM layer is a top layer that is in direct contact with the exhaust gas over a length of 20% or more of the entire length of the substrate from the downstream end of the exhaust gas flow of the substrate. A catalytic device for purifying exhaust gas according to any one of aspects 1 to 5. Aspect 7: An exhaust gas purification catalyst device as described in Aspect 6, wherein the first PGM layer is disposed over a length greater than 70% of the total length of the substrate from the exhaust gas upstream end of the substrate. Aspect 8: An exhaust gas purification catalyst device according to Aspect 6, wherein the second PGM layer is disposed over a length of 20% to 90% of the total length of the substrate from the exhaust gas downstream end of the substrate. Aspect 9: The first PGM layer is disposed over a length of more than 70% of the entire length of the substrate from the exhaust gas upstream end of the substrate; the second PGM layer is disposed over a length of 30% to 90% of the total length of the substrate from the exhaust gas downstream end of the substrate, the sum of the length of the first PGM layer and the length of the second PGM layer exceeds the total length of the substrate; and In a region where the first PGM layer and the second PGM layer overlap, the second PGM layer is the uppermost layer in direct contact with the exhaust gas. 7. An exhaust gas purification catalyst device according to claim 6. A method for purifying exhaust gas, comprising placing the exhaust gas purification catalyst device according to any one of Aspects 1 to 5 in an exhaust system of a gasoline engine, and purifying exhaust gas discharged from the gasoline engine. An upstream purification catalyst device arranged on the upstream side of an exhaust gas flow in an exhaust system of a gasoline engine; a downstream purification catalyst device disposed downstream of the exhaust gas flow in the exhaust system; A catalyst system for purifying exhaust gas for a gasoline engine, comprising: the upstream purification catalyst device is a three-way exhaust gas purification catalyst device containing a platinum group catalytic precious metal, The downstream purification catalyst device is an exhaust gas purification catalyst device according to any one of aspects 1 to 5. Exhaust gas purification catalyst system. A method for purifying exhaust gas, comprising disposing the exhaust gas purification catalyst system according to Aspect 11 in an exhaust system of a gasoline engine, and purifying exhaust gas discharged from the gasoline engine. Effect of the Invention

[0011] According to the present invention, there is provided an exhaust gas purification catalyst device for a gasoline engine, which reduces ammonia emissions even in low temperature conditions such as at the start of the engine. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a schematic cross-sectional view showing the configuration of an exhaust gas purification catalyst device in an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Exhaust gas purification catalyst device The exhaust gas purification catalyst device of the present invention is A substrate; an NH3 adsorption layer containing proton type zeolite; a PGM layer containing a catalytic precious metal selected from Pd, Pt, and Rh; A catalytic converter for exhaust gas purification for a gasoline engine, comprising: The proton-type zeolite contained in the NH3 adsorption layer has an average pore diameter of 0.60 nm or less, The NH3 adsorption layer is is disposed closer to the substrate than the PGM layer; The exhaust gas flow upstream end of the substrate is arranged at a length shorter than the entire length of the substrate, and the PGM layer is disposed at a length longer than the NH3 adsorption layer from the upstream end of the exhaust gas flow of the substrate, the PGM layer comprises a first PGM layer containing a catalytic precious metal selected from Pd and Pt, and a second PGM layer containing Rh; the first PGM layer comprises ceria; It is an exhaust gas purification catalytic device.

[0014] The configuration of an exhaust gas purification catalyst device in one embodiment of the present invention is shown in Figure 1. In Figure 1, the bold arrows indicate the direction of exhaust gas flow.

[0015] The exhaust gas purification catalyst device (100) of Fig. 1 has a substrate (10), an NH3 adsorption layer (20), and a PGM layer (30). The PGM layer (30) includes a first PGM layer (31) and a second PGM layer (32).

[0016] In the exhaust gas purification catalyst device (100), the NH3 adsorption layer (20) is disposed closer to the substrate (10) than the PGM layer (30), with a length from the upstream end of the substrate (10) in the exhaust gas flow direction to a length shorter than the entire length of the substrate (10). The PGM layer (30) (i.e., the laminate of the first PGM layer (31) and the second PGM layer (32)) is disposed with a length from the upstream end of the substrate (10) in the exhaust gas flow direction to a length longer than the NH3 adsorption layer (20), and covers the NH3 adsorption layer (20).

[0017] In the exhaust gas purification catalytic device (100) having such a configuration, ammonia is likely to be generated by reduction of NOx by the upper PGM layer (30) at low temperatures before the catalytic device is warmed up, such as at the start of the engine. At low temperatures, the generated ammonia is adsorbed by the NH3 adsorption layer (20) that is in direct contact with the PGM layer (30), and thus, emission to the outside is suppressed.

[0018] When the catalytic converter is warmed up, the ammonia adsorbed in the NH3 adsorption layer (20) is desorbed from the NH3 adsorption layer (20). The ammonia desorbed from the NH3 adsorption layer (20) comes into contact with the PGM layer (30) that covers the NH3 adsorption layer (20), where it is purified and then released into the atmosphere.

[0019] In the exhaust gas purification catalyst device of the present invention, due to such an action mechanism, ammonia emissions are reduced both before and after warm-up.

[0020] The components constituting the exhaust gas purification catalyst device of the present invention will be described below in order.

[0021] <Base material> The substrate in the exhaust gas purification catalyst device of the present invention may be a substrate having a plurality of cell flow paths divided by partition walls, or may be a honeycomb substrate used in conventional exhaust gas purification catalyst devices. The partition walls of the substrate may have pores that fluidly connect adjacent exhaust gas flow paths, or may not have such pores.

[0022] The constituent material of the substrate may be, for example, a refractory inorganic oxide such as cordierite, or may be a metal. The substrate may be of either a straight flow type or a wall flow type.

[0023] The substrate in the manufacturing method of the exhaust gas purification catalyst device of the present invention may typically be, for example, a straight-flow type monolith honeycomb substrate made of cordierite, a wall-flow type monolith honeycomb substrate made of cordierite, a metal honeycomb substrate, or the like.

[0024] The shape of the substrate may be a cylinder, an elliptical cylinder, a polygonal column, or the like.

[0025] The capacity of the substrate, as an apparent capacity expressed by the base area x the length, may be, for example, 500 mL or more, 800 mL or more, 1.0 L or more, or 1.2 L or more, and may be, for example, 5.0 L or less, 3.0 L or less, 2.0 L or less, 1.5 L or less, or 1.2 L or less.

[0026] <NH3 adsorption layer> The NH3 adsorption layer contains proton-type zeolite.

[0027] In normal zeolites, the charge compensation cations are metal ions, so the charge compensation cations tend to dissolve after durability tests, causing a loss of NH3 adsorption capacity. In contrast, proton-type zeolites have high heat resistance because the charge compensation cations in zeolites are protons, and the loss of NH3 adsorption capacity due to the dissolution of the charge compensation cations is suppressed.

[0028] The average pore size of the proton-type zeolite contained in the NH3 adsorption layer is 0.60 nm or less. The adsorption performance of zeolite depends on the relationship between the pore size of the zeolite and the molecular size of the adsorbate. Since the molecular size of NH3 is about 0.26 nm, it can be adsorbed with high efficiency by zeolite with an average pore size of 0.60 nm or less.

[0029] The average pore diameter of the proton type zeolite may be 0.55 nm or less, 0.50 nm or less, 0.45 nm or less, 0.40 nm or less, 0.35 nm or less, or 0.30 nm or less, for example, 0.25 nm or more, 0.30 nm or more, 0.35 nm or more, or 0.40 nm or more.

[0030] The pore size of a proton type zeolite is uniquely determined according to the crystal structure from the database of the International Zeolite Association Structure Committee. When a proton type zeolite is a mixture of multiple crystal structures, the average pore size of the proton type zeolite is defined as the average value of the pore sizes of the crystal structures shown in the database.

[0031] The proton type zeolite contained in the NH3 adsorption layer in the exhaust gas purification catalyst device of the present invention may include a small-ring proton type zeolite. In this specification, the term "small-ring proton type zeolite" refers to a proton type zeolite whose basic skeleton is composed only of rings selected from 4-, 6-, and 8-membered rings.

[0032] The small ring proton type zeolite may be H-ACO, H-AEI, H-AEN, H-AFN, H-AFT, AFX, H-ANA, H-APC, H-APD, H-ATT, H-CDO, H-CHA, H-DDR, H-DFT, H-EAB, H-EDI, H-EPI, H-ERI, H-GIS, H-GOO, H-IHW, H-ITE, H-ITW, H-LEV, H-LTA, H-KFI, H-MER, H-MON, H-NSI, H-OWE, H-PAU, H-PHI, H-RHO, H-RTH, H-SAT, H-SAV, H-SIV, H-THO, H-TSC, H-UEI, H-UFI, H-VNI, H-YUG, or H-ZON tower, and one or more types selected from these may be used.

[0033] From the viewpoint of more effectively adsorbing NH3, the proton type zeolite in the NH3 adsorption layer in the present invention may contain 80 mass% or more, 85 mass% or more, 90 mass% or more, 95 mass% or more, 98 mass% or more, or 99 mass% or more of small ring proton type zeolite relative to the total mass of the proton type zeolite, or 100 mass% of the proton type zeolite may be small ring proton type zeolite.

[0034] The SiO2 / Al2O3 ratio (SAR) of the proton type zeolite is not particularly limited and may be, for example, 5 or more, 10 or more, 20 or more, 30 or more, 40 or more, or 50 or more, and may be, for example, 500 or less, 300 or less, 200 or less, 100 or less, or 50 or less.

[0035] The NH3 adsorption layer may contain an optional component other than the proton-type zeolite. The optional component contained in the NH3 adsorption layer may be, for example, a zeolite other than the proton-type zeolite, an inorganic oxide other than the zeolite, a compound containing an alkali metal element, an alkaline earth metal element, or the like, or a binder.

[0036] The inorganic oxide other than zeolite, which is an optional component contained in the NH3 adsorption layer, may be, for example, an oxide of one or more elements selected from Al, Si, Ti, Zr, Ce, rare earth elements other than Ce, etc. The binder may be, for example, selected from alumina sol, zirconia sol, titania sol, etc.

[0037] Here, the NH3 adsorption layer may or may not contain an iron group element or a copper group element (particularly iron and copper). If the NH3 adsorption layer contains an iron group element or a copper group element, the proton-type zeolite may be ion-exchanged with these elements. If the exchanged ions are desorbed from the ion-exchanged zeolite, the zeolite framework may collapse, and the NH3 adsorption ability may be impaired. From this viewpoint, the NH3 adsorption layer may not contain an iron group element or a copper group element.

[0038] In addition, the NH3 adsorption layer may or may not contain a catalytic precious metal (e.g., a platinum group element). The catalytic precious metal in the NH3 adsorption layer may agglomerate during use, which may impair the catalytic performance, so the NH3 adsorption layer may not contain a catalytic precious metal.

[0039] From the viewpoint of more effectively adsorbing NH3, the proportion of proton-type zeolite in the NH3 adsorption layer may be, for example, 50 mass% or more, 60 mass% or more, 70 mass% or more, 80 mass% or more, 90 mass% or more, or 95 mass% or more, as the mass proportion of proton-type zeolite relative to the total mass of the NH3 adsorption layer, and may be less than 100 mass%, 98 mass% or less, 95 mass% or less, 90 mass% or less, or 80 mass% or less.

[0040] In the exhaust gas purification catalytic device of the present invention, the NH3 adsorption layer is disposed closer to the substrate than the PGM layer described later. The NH3 adsorption layer may be disposed, for example, so as to be in contact with the partition wall of the substrate, forming a lower layer of the catalyst layer.

[0041] In the exhaust gas purification catalyst device of the present invention, the NH3 adsorption layer is disposed from the exhaust gas flow upstream end of the substrate at a length shorter than the entire length of the substrate. In other words, the NH3 adsorption layer is not disposed near the downstream end of the substrate. This configuration is suitable from the viewpoint of reducing NH3 emissions, since it can efficiently adsorb NH3 flowing into the exhaust gas purification catalyst device, and it can reduce the probability that NH3 desorbed from the NH3 adsorption layer after the exhaust gas purification catalyst device is warmed up is discharged from the exhaust gas purification catalyst device without contacting the PGM layer on top.

[0042] From the viewpoint of efficiently adsorbing NH3, the length of the NH3 adsorption layer may be 30% or more, 40% or more, 50% or more, or 60% or more of the entire length of the substrate from the upstream end of the substrate. On the other hand, from the viewpoint of ensuring contact of desorbed NH3 with the PGM layer for purification, the length of the NH3 adsorption layer may be 95% or less, 90% or less, 85% or less, 80% or less, 75% or less, or 70% or less of the entire length of the substrate from the upstream end of the substrate.

[0043] The amount of the NH3 adsorption layer in the exhaust gas purification catalyst device of the present invention, as the mass of the NH3 adsorption layer per volume of the substrate including the portion where the NH3 adsorption layer is not arranged, may be 20 g / L or more, 50 g / L or more, 80 g / L or more, or 100 g / L or more, from the viewpoint of ensuring an effective NH3 adsorption amount, and may be 300 g / L or less, 250 g / L or less, 200 g / L or less, or 150 g / L or less, from the viewpoint of not excessively increasing pressure loss.

[0044] <PGM layer> The PGM layer has a first PGM layer containing a catalytic precious metal selected from Pd and Pt, and a second PGM layer containing Rh as a catalytic precious metal, and the first PGM layer contains ceria (CeO2).

[0045] The catalytic precious metal selected from Pd and Pt in the first PGM layer may be in the form of fine particles supported on an inorganic oxide. The average particle size of the catalytic precious metal particles may be, for example, 1 nm or more, 2 nm or more, or 3 nm or more, and may be 15 nm or less, 10 nm or less, 7 nm or less, or 5 nm or less.

[0046] The catalytic precious metal content in the first PGM layer may be, in terms of the combined mass of Pd and Pt per volume of the substrate, including portions where the first PGM layer is not disposed, 0.05 g / L or more, 0.10 g / L or more, 0.20 g / L or more, 0.30 g / L or more, or 0.40 g / L or more, and may be, for example, 1.50 g / L or less, 1.20 g / L or less, 1.00 g / L or less, 0.80 g / L or less, 0.60 g / L or less, or 0.50 g / L or less.

[0047] The catalytic precious metals in the first PGM layer may be supported on one or more of the inorganic oxides contained in the first PGM layer.

[0048] The first PGM layer contains ceria and may contain other inorganic oxides. The inorganic oxides other than ceria contained in the first PGM layer may be appropriately selected from the inorganic oxides listed above as examples of the inorganic oxides contained in the NH3 adsorption layer. The first PGM layer may particularly contain ceria and alumina, and may further contain other inorganic oxides.

[0049] Ceria is an inorganic oxide having oxygen storage and release capacity. Ceria may be in the form of a single substance, or may be contained in a composite oxide of Ce and another inorganic element (for example, a ceria-zirconia composite oxide).

[0050] The first PGM layer contains a certain amount of ceria, which improves the three-way catalytic activity. The content of ceria in the first PGM layer may be 5% by mass or more, 10% by mass or more, 12% by mass or more, or 15% by mass or more, and may be 60% by mass or less, 50% by mass or less, 40% by mass or less, 30% by mass or less, or 20% by mass or less, as the mass ratio of ceria to the total mass of the PGM layer. When ceria is in the form of a complex oxide of Ce and another inorganic element, the above mass ratio of ceria is the value obtained by converting the mass ratio of the complex oxide into the ceria equivalent amount.

[0051] From the viewpoint of maintaining good three-way catalyst performance both under lean and rich conditions, the amount of ceria contained in the first PGM layer may be, in terms of the ceria mass per 1 L of substrate volume, 4.0 g / L or more, 8.0 g / L or more, 12.0 g / L or more, 15.0 g / L or more, 20.0 g / L or more, or 30.0 g / L or more, and may be 45.0 g / L or less, 40.0 g / L or less, 35.0 g / L or less, 30.0 g / L or less, or 25.0 g / L or less.

[0052] The first PGM layer may or may not contain zeolite. However, if the first PGM layer contains zeolite, there is a concern that the purpose of the present invention, which aims to efficiently adsorb NH3 and efficiently purify desorbed NH3 by disposing the NH3 adsorption layer and the PGM layer as separate layers, may be lost. From this point of view, the first PGM layer does not need to contain zeolite.

[0053] The first PGM layer may contain an alkaline component. The alkaline component may be selected from compounds containing an alkaline metal or an alkaline earth metal. Examples of the alkaline metal include lithium, sodium, and potassium, and examples of the alkaline earth metal include calcium, strontium, and barium. One or more of these may be used.

[0054] The alkaline component may be, for example, an oxide, sulfate, or the like, of an alkali metal or alkaline earth metal.

[0055] The content of the alkaline component in the first PGM layer, expressed as a mass per volume of the substrate including the portion where the first PGM layer is not disposed, may be 1.0 g / L or more, 3.0 g / L or more, 5.0 g / L or more, or 7.5 g / L or more, and may be 20.0 g / L or less, 18.0 g / L or less, 15.0 g / L or less, or 12.0 g / L or less.

[0056] The amount of the first PGM layer in the exhaust gas purification catalyst device of the present invention, as the mass of the first PGM layer per volume of the substrate including the portion where the first PGM layer is not arranged, may be 80 g / L or more, 90 g / L or more, 100 g / L or more, 120 g / L or more, or 150 g / L or more, from the viewpoint of ensuring effective three-way catalytic activity (particularly oxidation purification catalytic activity), and may be 300 g / L or less, 250 g / L or less, 200 g / L or less, 180 g / L or less, 150 g / L or less, or 130 g / L or less, from the viewpoint of not excessively increasing pressure loss.

[0057] The second PGM layer contains Rh as a catalytic precious metal.

[0058] The catalytic precious metal Rh in the second PGM layer may be in the form of fine particles supported on an inorganic oxide. The average particle size of the Rh particles may be, for example, 1 nm or more, 2 nm or more, or 3 nm or more, and may be 15 nm or less, 10 nm or less, 7 nm or less, or 5 nm or less.

[0059] The content of Rh in the second PGM layer, expressed as the mass of Rh per volume of the substrate including portions where the second PGM layer is not disposed, may be 0.05 g / L or more, 0.10 g / L or more, 0.15 g / L or more, or 0.20 g / L or more, and may be, for example, 1.00 g / L or less, 0.80 g / L or less, 0.50 g / L or less, 0.40 g / L or less, or 0.30 g / L or less.

[0060] The catalytic precious metals in the second PGM layer may be supported on one or more of the inorganic oxides contained in the second PGM layer.

[0061] The inorganic oxide contained in the second PGM layer may be appropriately selected from the inorganic oxides listed above as examples of the inorganic oxide contained in the NH3 adsorption layer. The second PGM layer may contain alumina, and may further contain ceria, or may contain inorganic oxides other than these. Here, the ceria may be in the form of a simple substance, or may be contained in a composite oxide of Ce and another inorganic element (e.g., a ceria-zirconia composite oxide).

[0062] The second PGM layer may contain a certain amount of ceria. The content of ceria in the second PGM layer may be 1% by weight or more, 3% by weight or more, 5% by weight or more, or 7% by weight or more, and may be 20% by weight or less, 15% by weight or less, 10% by weight or less, or 8% by weight or less, expressed as a mass ratio of ceria to the total mass of the second PGM layer. When the ceria is in the form of a complex oxide of Ce and another inorganic element, the mass ratio of ceria mentioned above is a value obtained by converting the mass ratio of the complex oxide into a ceria equivalent amount.

[0063] From the viewpoint of maintaining good three-way catalyst performance both under lean and rich conditions, the amount of ceria contained in the second PGM layer may be, in terms of the ceria mass per 1 L of substrate volume, 2.0 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, and may be 20.0 g / L or less, 20.0 g / L or less, 15.0 g / L or less, 12.0 g / L or less, or 10.0 g / L or less.

[0064] The second PGM layer may or may not contain a zeolite.The second PGM layer may or may not contain a zeolite.

[0065] The second PGM layer may or may not contain an alkaline component. The second PGM layer may or may not contain an alkaline component.

[0066] The amount of the second PGM layer in the exhaust gas purification catalyst device of the present invention, as the mass of the NH3 adsorption layer per volume of the substrate including the portion where the second PGM layer is not arranged, may be 80 g / L or more, 90 g / L or more, 100 g / L or more, or 120 g / L or more, from the viewpoint of ensuring effective three-way catalytic activity (particularly reduction purification catalytic activity), and may be 200 g / L or less, 180 g / L or less, 150 g / L or less, or 130 g / L or less, from the viewpoint of not excessively increasing pressure loss.

[0067] The PGM layer (a laminate of a first PGM layer and a second PGM layer) is disposed from the upstream end of the exhaust gas flow of the substrate with a length longer than that of the NH3 adsorption layer. With this configuration, the NH3 adsorption layer is covered with the PGM layer over its entire length, and in particular, the downstream end of the NH3 adsorption layer is covered with the PGM layer. This is advantageous in that NH3 desorbed from the NH3 adsorption layer is reliably brought into contact with the PGM layer and purified.

[0068] The PGM layer is arranged in a range from the upstream end of the exhaust gas flow of the substrate to a length greater than 100% of the length of the NH3 adsorption layer and equal to the entire length of the substrate. The length of the PGM layer may be 105% or more, 110% or more, or 120% or more of the length of the NH3 adsorption layer, provided that the length is equal to or less than the entire length of the substrate. The PGM layer may be arranged from the upstream end of the exhaust gas flow of the substrate to a length equal to the entire length of the substrate.

[0069] In the exhaust gas purification catalyst device of the present invention, the PGM layer is disposed on the opposite side of the substrate with respect to the NH3 adsorption layer. In the region where the NH3 adsorption layer is disposed on the substrate, the PGM layer may be disposed on the NH3 adsorption layer, and in the region where the NH3 adsorption layer is not disposed on the substrate, the PGM layer may be disposed so as to contact the partition wall of the substrate.

[0070] The sum of the lengths of the first PGM layer and the second PGM layer may be equal to or theoretically greater than the total length of the substrate.

[0071] The first PGM layer may be disposed to extend from an upstream end of the substrate in the exhaust gas flow direction toward a downstream end of the exhaust gas flow direction. The length of the first PGM layer may be greater than 70%, at least 75%, at least 80%, at least 85%, at least 90%, or at least 95% of the total length of the substrate, for example, at most 100%, at most 99%, at most 95%, at most 90%, at most 80%, or at most 75%.

[0072] The first PGM layer may be the top layer in direct contact with the exhaust gas near the upstream end of the substrate in the exhaust gas flow direction, which is preferable because it can effectively purify HC and CO even before the exhaust gas purification catalyst device is warmed up.

[0073] The length of the first PGM layer that is the uppermost layer in direct contact with the exhaust gas near the upstream end of the substrate in the exhaust gas flow may be, for example, at least 10%, at least 20%, at least 30%, at least 40%, or at least 50% of the total length of the substrate, and may be, for example, at most 80%, at most 70%, at most 60%, or at most 50%.

[0074] The second PGM layer may be disposed to extend from the downstream end of the substrate in the exhaust gas flow direction toward the upstream end of the exhaust gas flow direction. The length of the second PGM layer may be at least 20%, at least 30%, at least 40%, at least 50%, or at least 60% of the total length of the substrate, and may be, for example, at most 90%, at most 80%, at most 70%, or at most 60%.

[0075] The second PGM layer may be the top layer in direct contact with the exhaust gas near the downstream end of the substrate in the exhaust gas flow. This configuration is preferable because it can effectively purify NOx before the exhaust gas purification catalyst device is warmed up, and can effectively purify NOx and NH3 desorbed from the NH3 adsorption layer after the exhaust gas purification catalyst device is warmed up.

[0076] The length of the second PGM layer that is the uppermost layer in direct contact with the exhaust gas near the downstream end of the substrate in the exhaust gas flow may be, for example, at least 20%, at least 30%, at least 40%, at least 50%, or at least 60% of the total length of the substrate, and may be, for example, at most 90%, at most 80%, at most 70%, or at most 60%.

[0077] If the combined length of the first and second PGM layers is greater than the overall length of the substrate, the first and second PGM layers will overlap in the region near the center of the substrate, and so will be arranged in a stacked manner, with the second PGM layer being the uppermost layer in direct contact with the exhaust gas where the two layers overlap.

[0078] In one embodiment, the PGM layer in the exhaust gas purification catalyst device of the present invention is the first PGM layer is disposed over a length greater than 70% of the total length of the substrate from an exhaust gas upstream end of the substrate; the second PGM layer is disposed over a length of 30% to 90% of the total length of the substrate from the exhaust gas downstream end of the substrate; the sum of the length of the first PGM layer and the length of the second PGM layer exceeds the total length of the substrate; and In the area where the first and second PGM layers overlap, the second PGM layer is the uppermost layer in direct contact with the exhaust gas.

[0079] <<Method of manufacturing an exhaust gas purification catalyst device>> The exhaust gas purification catalyst device of the present invention may be produced by any method so long as it has the above-mentioned configuration.

[0080] A non-limiting example of the method for producing an exhaust gas purification catalyst device of the present invention will be described below.

[0081] The exhaust gas purification catalyst device of the present invention may be produced, for example, by a method in which an NH3 adsorption layer, a first PGM layer, and a second PGM layer are disposed in this order on partition walls that separate the cell flow paths of a substrate.

[0082] The NH3 adsorption layer may be disposed, for example, by applying an NH3 adsorption layer-forming coating liquid to the partition wall of the substrate over a predetermined length from the upstream end in the exhaust gas flow direction, followed by drying and baking.

[0083] The substrate may be appropriately selected depending on the substrate of the desired exhaust gas purification catalytic device. For example, a straight-flow type monolith honeycomb substrate made of cordierite may be used.

[0084] The coating liquid for forming the NH3 adsorption layer may be, for example, a liquid in which a predetermined proton-type zeolite and other optional components are dissolved or dispersed in a suitable solvent (typically water). It is preferable to add a suitable thickener to the coating liquid for forming the NH3 adsorption layer to adjust the viscosity of the coating liquid, since this facilitates control of the coating length of the coating liquid. Examples of the thickener include polyvinyl alcohol (PVA)-based resins; cellulose-based resins such as methyl cellulose, ethyl cellulose, hydroxyethyl cellulose (HEC), and carboxymethyl cellulose; rosin-based resins, acrylic resins, and the like, and one or more selected from these may be used.

[0085] Drying and baking after application of the coating liquid may be carried out according to a known method or with appropriate modifications made by a person skilled in the art.

[0086] Next, the first PGM layer is deposited.

[0087] The first PGM layer may be disposed, for example, by applying a coating liquid for forming the first PGM layer onto the partition wall of the substrate on which the NH3 adsorption layer is disposed, over a predetermined length from the upstream end of the exhaust gas flow, followed by drying and baking.

[0088] The first PGM layer forming coating liquid may be, for example, a liquid obtained by dissolving or dispersing predetermined amounts of a predetermined inorganic oxide, a precursor of a catalytic precious metal selected from Pd and Pt, and other optional components in a suitable solvent (typically water).

[0089] The catalytic noble metal precursors may be the nitrates, sulfates, hydrochlorides, acetates, etc., of the desired catalytic noble metal.

[0090] In the case of the coating liquid for forming the first PGM layer, by adding a thickener similar to that used in the coating liquid for forming the NH3 adsorption layer, the viscosity of the coating liquid can be adjusted, making it easier to control the coating length of the coating liquid.

[0091] Drying and baking after application of the coating liquid may be carried out according to a known method or with appropriate modifications made by a person skilled in the art.

[0092] Furthermore, a second PGM layer is disposed.

[0093] The second PGM layer may be disposed, for example, by applying a coating liquid for forming a second PGM layer onto the partition wall of the substrate on which the NH3 adsorption layer and the first PGM layer are disposed, over a predetermined length from the downstream end of the exhaust gas flow, followed by drying and baking.

[0094] The second PGM layer forming coating fluid may be similar to the first PGM layer forming coating fluid except that a Rh nitrate, sulfate, hydrochloride, acetate, or the like is used as the catalytic precious metal precursor.

[0095] Drying and baking after application of the coating liquid may be carried out according to a known method or with appropriate modifications made by a person skilled in the art.

[0096] An exhaust gas purification catalyst device in which the PGM layer has a first PGM layer and a second PGM layer may be manufactured by the above-mentioned method or by a method which is appropriately modified by a person skilled in the art.

[0097] <Exhaust gas purification catalyst system> According to another aspect of the present invention, there is provided an exhaust gas purification catalyst system.

[0098] The exhaust gas purification catalyst system of the present invention comprises: an upstream purification catalyst device disposed upstream of an exhaust gas flow in an exhaust system of a gasoline engine; a downstream purification catalyst device disposed downstream of the exhaust gas flow in the exhaust system; A catalyst system for purifying exhaust gas for a gasoline engine, comprising: the upstream purification catalyst device is a three-way exhaust gas purification catalyst device containing a platinum group catalytic precious metal, The downstream side purification catalyst device is the above-described exhaust gas purification catalyst device of the present invention.

[0099] As the upstream purification catalyst device, a known three-way exhaust gas purification catalyst device may be used, and in particular, a three-way exhaust gas purification catalyst device containing one or more selected from Pd and Pt and Rh is preferable.

[0100] <Exhaust gas purification method> According to yet another aspect of the present invention, there is provided a method for purifying exhaust gas.

[0101] The exhaust gas purification method of the present invention comprises the steps of: The method for purifying exhaust gas includes arranging the exhaust gas purification catalyst device or the exhaust gas purification catalyst system of the present invention in the exhaust system of a gasoline engine to purify exhaust gas discharged from the gasoline engine. EXAMPLES

[0102] 1. Preparation of coating solution In preparing the coating liquid, the following alumina, OSC material, and binder were used. Alumina: Alumina containing 4.0% La2O3 and 96.0% Al2O3 OSC material of the coating liquid for forming the first PGM layer: a composite oxide containing 40.0 mass% CeO2, 50.0 mass% ZrO2, 5.0 mass% Pr2O3, and 5.0 mass% La2O3 OSC material of the coating liquid for forming the second PGM layer: a composite oxide containing 21.0 mass% CeO2, 72.0 mass% ZrO2, 5.3 mass% Nd2O3, and 1.7 mass% La2O3 Binder: Alumina binder

[0103] In the following Comparative Example 1-1 and Examples 1-1 to 1-7, the effect of the amount of OSC material mixed in the first PGM layer was investigated.

[0104] Comparative Example 1-1 (1) Coating solution for forming NH3 adsorption layer 106.0 g / L of H-CHA, 7.0 g / L of an alumina binder, and a cellulose-based resin as a thickener were added to ion-exchanged water and stirred to prepare a coating liquid for forming an NH3 adsorption layer.

[0105] (2) Preparation of coating solution for forming first PGM layer Platinum nitrate (equivalent to 1.1 g / L of Pt metal), 180.0 g / L of alumina, 10.0 g / L of BaSO4, 4.0 g / L of alumina binder, and a cellulose-based resin as a thickener were added to ion-exchanged water and stirred to prepare a first PGM layer-forming coating solution. No OSC material was added to the first PGM layer-forming coating solution of Comparative Example 1-1.

[0106] (3) Preparation of coating solution for forming second PGM layer Rhodium nitrate (equivalent to 0.22 g / L of Rh metal), 43.0 g / L of OSC material (equivalent to 8.6 g / L of CeO2), 75.0 g / L of alumina, 2.0 g / L of alumina binder, and a cellulose-based resin as a thickener were added to ion-exchanged water and stirred to prepare a coating solution for forming the second PGM layer.

[0107] 2. Manufacturing of exhaust gas purification catalyst devices The entire amount of the coating liquid for forming the NH3 adsorption layer was applied to a cordierite honeycomb substrate (diameter 105.7 mm, total length 114.3 mm, apparent volume 1.003 L, cell number 400 cpsi) over an area ranging from the upstream end of the exhaust gas flow to 75% of the substrate's total length, and the substrate was dried under air at 90°C for 2 hours and then fired at 500°C for 2 hours to form an NH3 adsorption layer on the substrate with a coating amount of 113.0 g / L.

[0108] Next, the entire amount of the coating liquid for forming the first PGM layer was applied from the upstream end of the exhaust gas flow of the substrate after the NH3 adsorption layer was formed over the entire length of the substrate, and the substrate was dried by ventilation at 90°C for 2 hours and then baked at 500°C for 2 hours to form a first PGM layer (Pt layer) with a coating amount of 195.1 g / L on the upstream side of the exhaust gas flow.

[0109] Furthermore, the entire amount of the coating liquid for forming the second PGM layer was applied over an area of ​​70% of the entire length of the substrate from the downstream end of the exhaust gas flow after the formation of the NH3 adsorption layer and Pt layer, and the substrate was dried by ventilation at 90°C for 2 hours and then baked at 500°C for 2 hours to form a second PGM layer (Rh layer) with a coating amount of 120.22 g / L on the downstream side of the exhaust gas flow, thereby producing the exhaust gas purification catalyst device of Comparative Example 1-1.

[0110] 3. Evaluation of exhaust gas purification catalyst devices The exhaust gas purification catalyst device of Comparative Example 1-1 obtained above was combined with a three-way catalyst device (substrate apparent volume 1.003 L) containing Pd and Rh as catalytic precious metals to form an exhaust gas purification catalyst system, which was evaluated by the following method.

[0111] (1) Durability An exhaust gas purification catalyst system was constructed by arranging a three-way catalyst device on the upstream side of the exhaust system of a V-type 8-cylinder, 4,600cc gasoline engine and the exhaust gas purification catalyst device of Comparative Example 1-1 on the downstream side.The engine was then operated at an average engine speed of 3,000 rpm, with the inlet gas temperature to the downstream exhaust gas purification catalyst device at 850°C, and exhaust gases of stoichiometric atmosphere and lean atmosphere were alternately circulated through the exhaust gas purification catalyst system for a certain period of time for 46 hours to test the durability of the exhaust gas purification catalyst system.

[0112] (2) Measurement of NH3 emissions A three-way catalytic converter was placed directly under the engine of an actual vehicle equipped with a 1,500cc gasoline engine as an underfloor catalyst, and the exhaust gas purification catalytic converter of Comparative Example 1-1 after the above durability test was placed thereon to configure an exhaust gas purification catalytic converter system. The outlet side of the exhaust gas purification catalytic converter of Comparative Example 1-1 was connected to an FT-IR device. The actual vehicle in this state was driven on a chassis dynamometer in a driving mode simulating an RDE (Real Driving Emission) test. Then, the NH3 concentration in the exhaust gas discharged from the exhaust gas purification catalytic converter of Comparative Example 1-1 was measured by FT-IR to obtain the NH3 emission. A commercially available automobile exhaust gas measuring device was also connected to the outlet side of the exhaust gas purification catalytic converter of Comparative Example 1-1 to measure the CO emission and the THC (total hydrocarbon) emission. The results are shown in Table 1.

[0113] Examples 1-1 to 1-7 In "(2) Preparation of the first PGM layer forming coating liquid", the blending amounts of the OSC material and alumina were changed as shown in Table 1, respectively, and an exhaust gas purification catalyst device was manufactured and evaluated in the same manner as in Comparative Example 1-1. The results are shown in Table 1.

[0114] [Table 1]

[0115] The following can be understood from Table 1.

[0116] In the exhaust gas purification catalyst device of Comparative Example 1-1, in which no OSC material exists in the first PGM layer, NH3 emission was extremely high. In contrast, in the exhaust gas purification catalyst devices of Examples 1-1 to 1-7, in which the OSC material is included in the first PGM layer, NH3 emission was suppressed. In particular, in the exhaust gas purification catalyst devices of Examples 1-1 to 1-6, in which the amount of OSC material (CeO2) in the first PGM layer is in the range of 5.0 g / L or more and 50.0 g / L or less, NH3 emission could be suppressed without significantly impairing the effect of suppressing NOx emission.

[0117] In Examples 2-1 to 2-5, the effect of the amount of OSC material in the second PGM layer was investigated.

[0118] Example 2-1 (1) Coating solution for forming NH3 adsorption layer The NH3 adsorption layer forming coating liquid of Example 2-1 was prepared in the same manner as the NH3 adsorption layer forming coating liquid of Comparative Example 1-1.

[0119] (2) Preparation of coating solution for forming first PGM layer Platinum nitrate equivalent to 1.1 g / L in terms of Pt metal, 45.0 g / L of OSC material (18.0 g / L in terms of CeO2), 135.0 g / L of alumina, 10.0 g / L of BaSO4, 4.0 g / L of alumina binder, and a cellulose-based resin as a thickener were added to ion-exchanged water and stirred to prepare a coating liquid for forming the first PGM layer.

[0120] (3) Preparation of coating solution for forming second PGM layer Rhodium nitrate (equivalent to 0.22 g / L of Rh metal), 118.0 g / L of alumina, 2.0 g / L of alumina binder, and a cellulose-based resin as a thickener were added to ion-exchanged water and stirred to prepare a second PGM layer-forming coating fluid. No OSC material was added to the second PGM layer-forming coating fluid of Example 2-1.

[0121] 2. Manufacturing of exhaust gas purification catalyst devices An exhaust gas purification catalyst device was manufactured in the same manner as in Comparative Example 1-1, except that the coating fluids prepared above were used as the "NH3 adsorption layer forming coating fluid," the "first PGM layer forming coating fluid," and the "second PGM layer forming coating fluid," respectively.

[0122] 3. Evaluation of exhaust gas purification catalyst devices The exhaust gas purification catalyst device of Example 2-1 obtained above was evaluated in the same manner as in Comparative Example 1-1. The results are shown in Table 2.

[0123] Examples 2-2 to 2-5 In "(3) Preparation of the second PGM layer forming coating liquid", the blending amounts of the OSC material and alumina were changed as shown in Table 2, respectively, and an exhaust gas purification catalyst device was manufactured and evaluated in the same manner as in Example 2-1. The results are shown in Table 2.

[0124] [Table 2]

[0125] From the results in Table 2, it was confirmed that the presence or absence and amount of OSC material in the second PGM layer does not substantially affect the NH3 and NOx emissions of the exhaust gas purification catalyst device. [Explanation of symbols]

[0126] 10 Base material 20 NH3 adsorption layer 30 PGM layers 31 1st PGM layer 32 Second PGM Layer 100 Exhaust gas purification catalyst device

Claims

1. A substrate; NH containing proton type zeolite ３ An adsorption layer; a PGM layer containing a catalytic precious metal selected from Pd, Pt, and Rh; An exhaust gas purification catalyst device for a gasoline engine, comprising: Said NH ３ The proton type zeolite contained in the adsorption layer has an average pore diameter of 0.60 nm or less, Said NH ３ The adsorption layer is The PGM layer is disposed closer to the substrate, The exhaust gas flow upstream end of the substrate is arranged at a length shorter than the entire length of the substrate, The PGM layer is formed by mixing the NH ３ It is arranged with a length longer than the adsorption layer, the PGM layer comprises a first PGM layer containing a catalytic precious metal selected from Pd and Pt, and a second PGM layer containing Rh; the first PGM layer comprises ceria; The first PGM layer is a top layer that is in direct contact with the exhaust gas over a length of 10% or more of the entire length of the substrate from the upstream end of the exhaust gas flow of the substrate, and The second PGM layer is a top layer that is in direct contact with the exhaust gas over a length of 20% or more of the entire length of the substrate from the downstream end of the exhaust gas flow of the substrate. Exhaust gas purification catalytic device.

2. 2. The exhaust gas purification catalyst device according to claim 1, wherein the proton type zeolite contains 80 mass% or more of small-ring proton type zeolite whose basic skeleton is composed only of rings selected from 4-, 6-, and 8-membered rings, based on the total mass of the proton type zeolite.

3. The small ring proton type zeolite is H-ACO, H-AEI, H-AEN, H-AFN, H-AFT, AFX, H-ANA, H-APC, H-APD, H-ATT, H-CDO, H-CHA, H-DDR, H-DFT, H-EAB, H-EDI, H-EPI, H-ERI, H-GIS, H-GOO, H-IHW, H-ITE, H-ITW, H-LEV , H-LTA, H-KFI, H-MER, H-MON, H-NSI, H-OWE, H-PAU, H-PHI, H-RHO, H-RTH, H-SAT, H-SAV, H-SIV, H-THO, H-TSC, H-UEI, H-UFI, H-VNI, H-YUG, and H-ZON. The exhaust gas purification catalyst device according to claim 2, wherein the catalyst is one or more selected from the group consisting of 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 9

4. 2. The exhaust gas purification catalyst device according to claim 1, wherein the amount of ceria contained in the first PGM layer is 4.0 g / L or more and 45.0 g / L or less in terms of the mass of ceria per 1 L of substrate volume.

5. 3. The exhaust gas purification catalyst device according to claim 2, wherein the amount of ceria contained in the first PGM layer is 4.0 g / L or more and 45.0 g / L or less in terms of the mass of ceria per 1 L of substrate volume.

6. 2. The exhaust gas purification catalyst device according to claim 1, wherein the first PGM layer is disposed over a length of more than 70% of the entire length of the substrate from the exhaust gas upstream end of the substrate.

7. 2. The exhaust gas purification catalyst device according to claim 1, wherein the second PGM layer is disposed over a length of 20% to 90% of the entire length of the substrate from the exhaust gas downstream end of the substrate.

8. The first PGM layer is disposed over a length of more than 70% of the total length of the substrate from the exhaust gas upstream end of the substrate; The second PGM layer is disposed over a length of 30% to 90% of the entire length of the substrate from the exhaust gas downstream end of the substrate, The sum of the length of the first PGM layer and the length of the second PGM layer exceeds the total length of the substrate; and In the region where the first PGM layer and the second PGM layer overlap, the second PGM layer is the uppermost layer that is in direct contact with exhaust gas. The exhaust gas purification catalyst device according to claim 1.

9. 9. A method for purifying exhaust gas, comprising: disposing the exhaust gas purification catalyst device according to any one of claims 1 to 8 in an exhaust system of a gasoline engine, and purifying exhaust gas discharged from the gasoline engine.

10. an upstream purification catalyst device disposed upstream of an exhaust gas flow in an exhaust system of a gasoline engine; a downstream purification catalyst device disposed downstream of the exhaust gas flow in the exhaust system; A catalyst system for purifying exhaust gas for a gasoline engine, comprising: the upstream purification catalyst device is a three-way exhaust gas purification catalyst device containing a platinum group catalytic precious metal, The downstream purification catalyst device is an exhaust gas purification catalyst device according to any one of claims 1 to 8. Exhaust gas purification catalyst system.

11. 11. A method for purifying exhaust gas, comprising: disposing the exhaust gas purification catalyst system according to claim 10 in an exhaust system of a gasoline engine, and purifying exhaust gas discharged from the gasoline engine.

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