Exhaust gas purification catalyst device for gasoline engine

Abstract

Provided is an exhaust gas purification catalyst device for a gasoline engine. The exhaust gas purification catalyst device has: a substrate; an NH3 adsorption layer containing a proton-type zeolite; and a PGM layer containing a catalytic noble metal selected from among Pd, Pt, and Rh. 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 disposed closer to the substrate than the PGM layer and is disposed at a length shorter than the entire length of the substrate from the upstream end of the substrate in the exhaust gas flow direction. The PGM layer is disposed at a length longer than the NH3 adsorption layer from the upstream end of the substrate in the exhaust gas flow direction. The PGM layer has a first PGM layer containing a catalytic noble metal selected from among Pd and Pt, and a second PGM layer containing Rh. The first PGM layer contains ceria.

Description

Exhaust gas purification catalyst device for gasoline engines

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

[0002] The exhaust gas emitted from a gasoline engine contains hydrocarbons (HC), carbon monoxide (CO), nitrogen oxides (NOx), etc., which are purified by an exhaust gas purification catalyst device installed in the engine's exhaust system before being released into the atmosphere.

[0003] Three-way catalysts capable of purifying all of HC, CO, and NOx are known as exhaust gas purification catalytic devices. For example, Patent Document 1 describes an exhaust gas purification catalyst that has a multilayer alumina layer structure 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.

[0004] Japanese Patent Application Publication No. 63-039633

[0005] In a gasoline engine, when the mixture of gasoline and air is rich, ammonia (NH ３ In particular, a large amount of ammonia tends to be produced 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 low temperatures before the catalyst is warmed up, the generated ammonia may not be purified completely and some of it may be emitted.

[0007] The EU's next emission 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, and an object of the present invention is to provide an exhaust gas purification catalyst device for a gasoline engine that reduces ammonia emissions even in low temperature conditions such as at the time of engine start-up.

[0009] The present invention is as follows.

[0010] <<Aspect 1>> A substrate and an NH containing proton type zeolite ３ An exhaust gas purification catalyst device for a gasoline engine, comprising: an adsorption layer; and a PGM layer containing a catalytic noble metal selected from Pd, Pt, and Rh, wherein the NH ３ The proton-type zeolite contained in the adsorption layer has an average pore diameter of 0.60 nm or less, ３ The adsorption layer is disposed closer to the substrate than the PGM layer, and is disposed from the upstream end of the substrate in the exhaust gas flow direction by a length shorter than the entire length of the substrate. The PGM layer is disposed from the upstream end of the substrate in the exhaust gas flow direction by a length shorter than the entire length of the substrate. ３The catalytic converter for exhaust gas purification 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, and 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, and the small-ring .... <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 device for purifying exhaust gases according to Aspect 2, wherein the first PGM layer 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 5> The catalytic device for exhaust gas purification 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 in terms of the mass of ceria per 1 L of substrate volume. <Aspect 6> The catalytic device for exhaust gas purification according to any one of Aspects 1 to 5, wherein the first PGM layer is the uppermost layer in direct contact with exhaust gas over a length of 10% or more of the entire substrate length from the upstream end of the exhaust gas flow of the substrate, and the second PGM layer is the uppermost layer in direct contact with exhaust gas over a length of 20% or more of the entire substrate length from the downstream end of the exhaust gas flow of the substrate. <Aspect 7> The catalytic device for exhaust gas purification according to Aspect 6, wherein the first PGM layer is arranged over a length of more than 70% of the entire substrate length from the upstream end of the exhaust gas flow of the substrate.<Aspect 8> The catalytic device for exhaust gas purification according to Aspect 6, wherein the second PGM layer is disposed over a length of 20% to 90% of the entire length of the substrate from the downstream end of the exhaust gas of the substrate. <Aspect 9> The catalytic device for exhaust gas purification according to Aspect 6, wherein the first PGM layer is disposed over a length of more than 70% of the entire length of the substrate from the upstream end of the exhaust gas 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 downstream end of the exhaust gas of the substrate, the sum of the lengths of the first PGM layer and the second PGM layer exceeds the entire length of the substrate, and in an overlapping region of the first PGM layer and the second PGM layer, the second PGM layer is the uppermost layer in direct contact with exhaust gas. <Aspect 10> A method for exhaust gas purification, comprising arranging the catalytic device for exhaust gas purification according to any one of Aspects 1 to 5 in an exhaust system of a gasoline engine, and purifying exhaust gas emitted from the gasoline engine. <Aspect 11> A catalyst system for purifying exhaust gas for a gasoline engine, comprising: an upstream purification catalyst device arranged upstream of the exhaust gas flow in an exhaust system of the gasoline engine; and a downstream purification catalyst device arranged downstream of the exhaust gas flow in the exhaust system, wherein the upstream purification catalyst device is a three-way exhaust gas purification catalyst device containing a platinum group catalytic precious metal, and the downstream purification catalyst device is the exhaust gas purification catalyst device according to any one of Aspects 1 to 5. <Aspect 12> A method for purifying exhaust gas, comprising arranging the exhaust gas purification catalyst system according to Aspect 11 in the exhaust system of the gasoline engine, and purifying exhaust gas emitted from the gasoline engine.

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

[0012] FIG. 1 is a schematic cross-sectional view showing the configuration of an exhaust gas purification catalyst device according to an embodiment of the present invention.

[0013] The catalytic converter for exhaust gas purification of the present invention comprises a substrate and an NH 3 catalyst containing proton-type zeolite. ３An exhaust gas purification catalyst device for a gasoline engine, comprising: an adsorption layer; and a PGM layer containing a catalytic noble metal selected from Pd, Pt, and Rh, wherein the NH ３ The proton-type zeolite contained in the adsorption layer has an average pore diameter of 0.60 nm or less, ３ The adsorption layer is disposed closer to the substrate than the PGM layer, and is disposed from the upstream end of the substrate in the exhaust gas flow direction by a length shorter than the entire length of the substrate. The PGM layer is disposed from the upstream end of the substrate in the exhaust gas flow direction by a length shorter than the entire length of the substrate. ３ The exhaust gas purification catalyst device is arranged with a length longer than that of the adsorption layer, and 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.

[0014] The configuration of an exhaust gas purification catalyst device according to an 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. ３ The adsorption layer (20) and the PGM layer (30) are included. 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), NH ３ The 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 that is 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 on the substrate (10) from the upstream end of the exhaust gas flow direction. ３ The adsorption layer (20) is arranged with a length longer than that of the NH ３ It is coated with an adsorbent layer (20).

[0017] In the exhaust gas purification catalytic device (100) having such a configuration, ammonia is easily generated by the reduction of NOx by the upper PGM layer (30) in a low temperature state before the catalyst device is warmed up, such as when starting the engine. The generated ammonia is easily generated by the reduction of NOx by the upper PGM layer (30) in a low temperature state. ３ The adsorption layer (20) adsorbs the carbon dioxide, thereby preventing the carbon dioxide from being discharged to the outside.

[0018] Once the catalyst is warmed up, NH ３ The ammonia adsorbed in the adsorption layer (20) is NH ３ Desorbed from the adsorption layer (20). ３ The ammonia desorbed from the adsorption layer (20) is NH ３ It comes into contact with the PGM layer (30) that coats the 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, the above-described mechanism of action reduces ammonia emissions both before and after warm-up.

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

[0021] The substrate in the catalytic converter for exhaust gas purification of the present invention may be a substrate having a plurality of cell flow paths separated by partition walls, or may be a honeycomb substrate used in conventional catalytic converters for exhaust gas purification. The partition walls of the substrate may or may not have pores that fluidly connect adjacent exhaust gas flow paths.

[0022] The constituent material of the substrate may be, for example, a refractory inorganic oxide such as cordierite or silicon carbide, 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 or silicon carbide, a wall-flow type monolith honeycomb substrate made of cordierite or silicon carbide, a metal honeycomb substrate, or the like.

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

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

[0026] <NH ３ Adsorption layer> NH ３ The adsorption layer contains a proton-type zeolite.

[0027] In ordinary zeolites, the charge compensation cations are metal ions, so after durability testing, the charge compensation cations are eluted and become NH ３ In contrast, proton-type zeolite has high heat resistance because the charge compensation cations of the zeolite are protons, and the adsorption capacity is often impaired. ３ The decrease in adsorption capacity is suppressed.

[0028] NH ３ The average pore size of the proton-type zeolite contained in the adsorption layer is 0.60 nm or less. The adsorption performance of the zeolite depends on the relationship between the pore size of the zeolite and the molecular size of the adsorbate. ３ Since the molecular size of is about 0.26 nm, it can be adsorbed with high efficiency into zeolites with an average pore diameter 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, and may be, 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 its crystal structure from the database of the Structure Committee of the International Zeolite Society. 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] NH in the exhaust gas purification catalyst device of the present invention ３ The proton-type zeolite contained in the adsorption layer 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] Small ring proton type zeolites include 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, and H-LE. H-V, 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] NH in the present invention ３ The proton type zeolite in the adsorption layer is NH ３ From the viewpoint of more effectively adsorbing the compound, the small ring proton type zeolite may be contained in an amount of 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 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] SiO of proton type zeolite ２ / Al ２ O ３ The ratio (SAR) 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] NH ３ The adsorption layer may contain any component other than the proton-type zeolite.３ The optional components contained in the adsorption layer may be, for example, zeolites other than proton-type zeolites, inorganic oxides other than zeolites, compounds containing alkali metal elements, alkaline earth metal elements, or the like, binders, and the like.

[0036] NH ３ The inorganic oxide other than zeolite, which is an optional component contained in the adsorption layer, may be, for example, an oxide of one or more elements selected from Al, Si, Ti, Zr, Ce, and rare earth elements other than Ce. The binder may be, for example, selected from alumina sol, zirconia sol, titania sol, etc.

[0037] Here, NH ３ The adsorption layer may or may not contain iron group elements or copper group elements (particularly iron and copper). ３ If an iron group element or a copper group element is contained in the adsorption layer, the proton type zeolite may be ion-exchanged with these elements. When the exchanged ions are released from the ion-exchanged zeolite, the zeolite framework collapses, and NH ３ From this point of view, the adsorption capacity may be impaired. ３ The adsorption layer may not contain iron group elements or copper group elements.

[0038] Also, NH ３ The adsorption layer may or may not contain a catalytic noble metal (e.g., a platinum group element). ３ The catalytic noble metals in the adsorption layer may aggregate during use and impair catalytic performance. ３ The adsorbent layer may be free of catalytic noble metals.

[0039] NH ３ The proportion of proton-type zeolite in the adsorption layer is NH ３ From the viewpoint of more effectively adsorbing NH ３ The mass ratio of the proton-type zeolite to the total mass of the 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, 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 catalyst device of the present invention, NH ３ The adsorption layer is disposed closer to the substrate than the PGM layer described below. ３ The adsorption layer may be disposed, for example, so as to be in contact with the partition wall of the substrate, and form a lower layer of the catalyst layer.

[0041] In the exhaust gas purification catalyst device of the present invention, NH ３ The adsorption layer is disposed from the upstream end of the substrate in the exhaust gas flow direction over a length shorter than the entire length of the substrate. ３ The adsorption layer is not disposed near the downstream end of the substrate. With this configuration, NH ３ and after the exhaust gas purification catalyst device is warmed up, ３ NH desorbed from the adsorption layer ３ However, the probability of NH being discharged from the exhaust gas purification catalyst device without coming into contact with the upper PGM layer can be reduced. ３ This is preferable from the viewpoint of reducing emissions.

[0042] NH ３ From the viewpoint of efficient adsorption of NH ３ The length of the adsorption layer may be 30% or more, 40% or more, 50% or more, or 60% or more of the total length of the substrate from the upstream end of the substrate. ３ From the viewpoint of ensuring that NH ３ The length of the 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 total length of the substrate from the upstream end of the substrate.

[0043] NH in the exhaust gas purification catalyst device of the present invention ３ The amount of the adsorption layer is NH ３ NH per volume of the substrate, including the portion where the adsorption layer is not placed ３ As the mass of the adsorption layer, the effective NH ３From the viewpoint of ensuring an adsorption amount of 20 g / L or more, 50 g / L or more, 80 g / L or more, or 100 g / L or more, and from the viewpoint of not excessively increasing the pressure loss, the adsorption amount may be 300 g / L or less, 250 g / L or less, 200 g / L or less, or 150 g / L or less.

[0044] <PGM Layer> The PGM layer has a first PGM layer containing a catalytic noble metal selected from Pd and Pt, and a second PGM layer containing Rh as a catalytic noble metal, and the first PGM layer is made of ceria (CeO ２ ) is included.

[0045] The catalytic noble metal selected from Pd and Pt in the first PGM layer may be in the form of fine particles supported on an inorganic oxide, and the average particle size of the catalytic noble 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 content of catalytic precious metals in the first PGM layer may be, as the total mass of Pd and Pt per volume of the substrate, including the portion 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 noble metal 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 are NH ３ The inorganic oxide contained in the adsorption layer may be appropriately selected from those exemplified above. The first PGM layer may particularly contain ceria and alumina, and may further contain inorganic oxides other than these.

[0049] Ceria is an inorganic oxide having oxygen storage and release capacity. Ceria may be in the form of a single substance or 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 the ceria is in the form of a complex oxide of Ce and another inorganic element, the mass ratio of ceria is the value obtained by converting the mass ratio of the complex oxide into a 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 liter 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, NH ３ By disposing the adsorption layer and the PGM layer as separate layers, NH ３ Efficiently adsorbs and desorbs NH ３ In this respect, the first PGM layer does not necessarily need to contain zeolite.

[0053] The first PGM layer may contain an alkali component selected from compounds containing alkali metals and alkaline earth metals. Examples of alkali metals include lithium, sodium, and potassium, and examples of alkaline earth metals 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 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, in terms of mass per volume of the substrate, including the portion where the first PGM layer is not disposed, 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 may be, as the mass of the first PGM layer per volume of the substrate including the portion where the first PGM layer is not disposed, 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 noble 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 Rh content in the second PGM layer 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, in terms of the mass of Rh per volume of the substrate, including the portion where the second PGM layer is not disposed, 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 noble metal 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 is NH ３ The inorganic oxide contained in the adsorption layer may be appropriately selected from those exemplified above. The second PGM layer may contain alumina, ceria, or other inorganic oxides. Here, the ceria may be in the form of simple ceria or may be contained in a composite oxide of Ce and another inorganic element (e.g., 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 20% by weight or less, 15% by weight or less, 10% by weight or less, or 8% by weight or less, 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 is the 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 zeolite. The second PGM layer may or may not contain 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 is determined based on the NH ３ The mass of the adsorption layer 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 formed by absorbing NH ３ The length of the adsorption layer is longer than that of the NH ３ The adsorption layer is coated over its entire length with the PGM layer, in particular with NH ３ The downstream end of the adsorption layer is covered with the PGM layer. ３ NH desorbed from the adsorption layer ３ This is advantageous in that the PGM layer is reliably contacted and purified.

[0068] The PGM layer is arranged in the range from the upstream end of the exhaust gas flow of the substrate to the ３ The length of the PGM layer is in the range of more than 100% of the length of the adsorption layer and up to the same length as the entire length of the substrate. ３ The PGM layer may be disposed over a length equal to the entire length of the substrate from the upstream end of the substrate in the exhaust gas flow direction.

[0069] In the exhaust gas purification catalyst device of the present invention, the PGM layer is ３ The PGM layer is disposed on the opposite side of the substrate from the adsorption layer.３ In the region where the adsorption layer is disposed, the NH ３ The substrate may be disposed on the adsorption layer, and NH ３ In the region where no adsorption layer is disposed, the adsorption layer may be disposed so as to be in contact with 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 greater than the total length of the substrate.

[0071] The first PGM layer may be disposed so as to extend from the upstream end of the substrate in the exhaust gas flow direction toward the downstream end of the exhaust gas flow direction. The length of the first PGM layer may be more than 70%, 75% or more, 80% or more, 85% or more, 90% or more, or 95% or more of the total length of the substrate, and may be, for example, 100% or less, 99% or less, 95% or less, 90% or less, 80% or less, or 75% or less.

[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. This configuration is advantageous because it can effectively purify HC and CO even before the exhaust gas purification catalytic device is warmed up.

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

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

[0075] The second PGM layer may be the uppermost layer in direct contact with the exhaust gas near the downstream end of the substrate in the exhaust gas flow. With this configuration, the second PGM layer is capable of trapping NOx before the exhaust gas purification catalytic device is warmed up, and trapping NOx and NH after the exhaust gas purification catalytic device is warmed up. ３NH desorbed from the adsorption layer ３ are preferably capable of effectively purifying the above-mentioned components.

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

[0077] When the total length of the first and second PGM layers is longer than the total length of the substrate, the first and second PGM layers overlap in the region near the center of the substrate, resulting in a stacked arrangement, with the second PGM layer being the top layer in direct contact with the exhaust gas.

[0078] In one embodiment, the PGM layers in the exhaust gas purification catalyst device of the present invention are such that: the first PGM layer is arranged 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 arranged 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 lengths of the first PGM layer and 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 in direct contact with the exhaust gas.

[0079] <<Method for Manufacturing the 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.

[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, for example, a catalyst containing NH ３ It may be manufactured by a method in which an adsorption layer, a first PGM layer, and a second PGM layer are arranged in this order.

[0082] NH ３ The adsorption layer is, for example, formed on the partition wall of the substrate over a predetermined length from the upstream end of the exhaust gas flow. ３The adsorption layer may be disposed by applying a coating liquid for forming the adsorption layer, followed by drying and baking.

[0083] The substrate may be appropriately selected depending on the substrate of the desired exhaust gas purification catalyst device, and for example, a straight-flow type monolith honeycomb substrate made of cordierite or silicon carbide may be used.

[0084] NH ３ The coating liquid for forming the adsorption layer may be, for example, a liquid obtained by dissolving or dispersing predetermined amounts of a predetermined proton-type zeolite and other optional components in an appropriate solvent (typically water). ３ It is preferable to add a suitable thickener to the coating liquid for forming the adsorption layer to adjust the viscosity of the coating liquid, since this facilitates control of the coating length of the coating liquid. Examples of thickeners include polyvinyl alcohol (PVA)-based resins; cellulose-based resins such as methyl cellulose, ethyl cellulose, hydroxyethyl cellulose (HEC), and carboxymethyl cellulose; rosin-based resins; and acrylic resins. 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 is, for example, NH ３ The first PGM layer may be disposed by applying a coating liquid for forming the first PGM layer on the partition wall of the substrate on which the adsorption layer is disposed, over a predetermined length from the upstream end of the exhaust gas flow, followed by drying and baking.

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

[0089] The catalytic noble metal precursor may be the nitrate, sulfate, hydrochloride, acetate, etc., of the desired catalytic noble metal.

[0090] In the case of the coating liquid for forming the first PGM layer, NH３ By adding a thickener similar to that of the coating liquid for forming the adsorption layer to adjust the viscosity of the coating liquid, it becomes 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 is, for example, NH ３ The second PGM layer may be disposed by applying a coating liquid for forming the second PGM layer onto the partition wall of the substrate on which the adsorption layer and the first PGM layer are disposed, over a predetermined length from the downstream end of the exhaust gas flow, and then drying and baking the coating liquid.

[0094] The second PGM layer forming coating liquid may be the same as the first PGM layer forming coating liquid except that a nitrate, sulfate, hydrochloride, acetate, etc. of Rh is used as the catalytic noble 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 method or by a method which is appropriately modified by a person skilled in the art.

[0097] <<Catalyst System for Purifying Exhaust Gas>> According to another aspect of the present invention, there is provided a catalyst system for purifying exhaust gas.

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

[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 elements selected from Pd and Pt and Rh is preferred.

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

[0101] The method for purifying exhaust gas of the present invention is a method for purifying exhaust gas, which comprises 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, and purifying exhaust gas emitted from the gasoline engine.

[0102] 1. Preparation of Coating Solution In preparing the coating solution, the following alumina, OSC material, and binder were used: Alumina: 4.0% La ２ O ３ and 96.0% Al ２ O ３ Alumina containing: OSC material of coating liquid for forming first PGM layer: 40.0 mass% CeO ２ , 50.0 mass% ZrO ２ , 5.0 wt% Pr ２ O ３ , and 5.0% by mass of La ２ O ３ OSC material of the coating liquid for forming the second PGM layer: 21.0 mass% CeO ２ , 72.0 mass% ZrO ２ , 5.3% by weight of Nd ２ O ３ , and 1.7% by mass of La ２ O ３ Composite oxide containing Binder: Alumina binder

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

[0104] <Comparative Example 1-1> (1) NH ３Coating solution for forming an adsorption layer 106.0 g / L of H-CHA, 7.0 g / L of alumina binder, and a cellulose-based resin as a thickener were added to ion-exchanged water and stirred to form a coating solution for forming an adsorption layer. ３ A coating liquid for forming an adsorption layer was prepared.

[0105] (2) Preparation of coating liquid for forming first PGM layer Platinum nitrate equivalent to 1.1 g / L in terms of Pt metal, 180.0 g / L of alumina, 10.0 g / L of BaSO ４ 4.0 g / L of an alumina binder and a cellulose-based resin as a thickener were added and stirred to prepare a first PGM layer-forming coating solution. No OSC material was blended into the first PGM layer-forming coating solution of Comparative Example 1-1.

[0106] (3) Preparation of coating liquid for forming second PGM layer Rhodium nitrate equivalent to 0.22 g / L in terms of Rh metal, 43.0 g / L of OSC material (CeO ２ A coating liquid for forming a second PGM layer was prepared by adding 75.0 g / L of alumina, 2.0 g / L of alumina binder, and a cellulose-based resin as a thickener, and stirring the mixture.

[0107] 2. Manufacture of an exhaust gas purification catalyst device A straight-flow type honeycomb substrate made of cordierite (diameter 105.7 mm, total length 114.3 mm, apparent volume 1.003 L, number of cells 400 cpsi) was treated with NH3 over a range from the upstream end of the exhaust gas flow to 75% of the substrate's total length. ３ The entire amount of the coating liquid for forming the adsorption layer was applied, and the coating was dried by ventilation at 90°C for 2 hours, and then baked at 500°C for 2 hours. ３ An adsorption layer was formed.

[0108] Next, NH ３ After the adsorption layer was formed, 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 along 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) on the upstream side of the exhaust gas flow with a coating amount of 195.1 g / L.

[0109] Furthermore, NH３ After the formation of the adsorption layer and Pt layer, 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, 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) on the downstream side of the exhaust gas flow with a coating amount of 120.22 g / L, thereby producing the exhaust gas purification catalyst device of Comparative Example 1-1.

[0110] 3. Evaluation of Exhaust Gas Purification Catalyst Device The exhaust gas purification catalyst device of Comparative Example 1-1 obtained above was evaluated as an exhaust gas purification catalyst system in combination with a three-way catalyst device (apparent volume of substrate: 1.003 L) containing Pd and Rh as catalytic precious metals 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 V8 gasoline engine with a displacement of 4,600 cc and an 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 in a stoichiometric atmosphere and a lean atmosphere were alternately passed through the exhaust gas purification catalyst system for a fixed period of time for 46 hours to test the durability of the exhaust gas purification catalyst system.

[0112] (2) NH ３ Emission Measurement An exhaust gas purification catalyst system was constructed by placing a three-way catalyst device as an underfloor catalyst directly below the engine of an actual vehicle equipped with a 1,500cc gasoline engine, and the exhaust gas purification catalyst device of Comparative Example 1-1 after the durability test described above. In addition, the outlet side of the exhaust gas purification catalyst device 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, FT-IR was used to measure NH in the exhaust gas emitted from the exhaust gas purification catalyst device of Comparative Example 1-1. ３ The concentration was measured and NH ３The emissions were measured. A commercially available automobile exhaust gas measuring instrument was connected to the outlet side of the exhaust gas purification catalyst device of Comparative Example 1-1 to measure CO emissions and THC (total hydrocarbon) emissions. The results are shown in Table 1.

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

[0114]

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

[0116] In the exhaust gas purification catalyst device of Comparative Example 1-1 in which the OSC material is not present in the first PGM layer, NH ３ On the other hand, in the exhaust gas purification catalyst devices of Examples 1-1 to 1-7, which contained the OSC material in the first PGM layer, the NH ３ The emission was suppressed. In particular, the presence of an OSC material (CeO ２ In the exhaust gas purification catalyst devices of Examples 1-1 to 1-6 in which the amount of NH2 was in the range of 5.0 g / L or more and 50.0 g / L or less, the effect of suppressing NOx emissions was not significantly impaired, and NH3 ３ Emissions could be reduced.

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

[0118] Example 2-1 (1) NH ３ Coating liquid for forming adsorption layer NH of Example 2-1 ３ The coating liquid for forming the adsorption layer was NH ３ The coating liquid for forming the adsorption layer was prepared in the same manner as above.

[0119] (2) Preparation of coating liquid for forming first PGM layer Platinum nitrate equivalent to 1.1 g / L of Pt metal, 45.0 g / L of OSC material (CeO ２ (equivalent to 18.0 g / L), 135.0 g / L alumina, 10.0 g / L BaSO ４4.0 g / L of an alumina binder and a cellulose-based resin as a thickener were added and stirred to prepare a coating liquid for forming a first PGM layer.

[0120] (3) Preparation of Coating Solution for Forming Second PGM Layer Rhodium nitrate equivalent to 0.22 g / L in terms of Rh metal, 118.0 g / L alumina, 2.0 g / L 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 a second PGM layer. No OSC material was blended into the coating solution for forming the second PGM layer of Example 2-1.

[0121] 2. Manufacturing of exhaust gas purification catalyst equipment "NH ３ An exhaust gas purification catalyst device was manufactured in the same manner as in Comparative Example 1-1, except that the coating liquids prepared above were used as the "coating liquid for forming the adsorption layer," "coating liquid for forming the first PGM layer," and "coating liquid for forming the second PGM layer."

[0122] 3. Evaluation of the exhaust gas purification catalyst device 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 Exhaust gas purification catalyst devices were manufactured and evaluated in the same manner as in Example 2-1, except that in "(3) Preparation of coating liquid for forming second PGM layer," the blending amounts of the OSC material and alumina were changed as shown in Table 2. The results are shown in Table 2.

[0124]

[0125] From the results in Table 2, the presence or absence and amount of the OSC material in the second PGM layer depend on the NH ３ It was confirmed that there was no substantial effect on emissions and NOx emissions.

[0126] 10 base material 20 NH ３ Adsorption layer 30 PGM layer 31 First PGM layer 32 Second PGM layer 100 Exhaust gas purification catalyst device

Claims

1. A substrate and NH containing proton type zeolite ３ An exhaust gas purification catalyst device for a gasoline engine, comprising: an adsorption layer; and a PGM layer containing a catalytic precious metal selected from Pd, Pt, and Rh, ３ The proton type zeolite contained in the adsorption layer has an average pore diameter of 0.60 nm or less, ３ The adsorption layer is disposed on the substrate side of the PGM layer, and is disposed from the upstream end of the substrate in the exhaust gas flow direction with a length shorter than the entire length of the substrate. The PGM layer is disposed on the substrate side of the exhaust gas flow direction with a length shorter than the entire length of the substrate. ３ An exhaust gas purification catalyst device, the device being arranged to have a length longer than an adsorption layer, the PGM layer having 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 containing ceria.

2. An exhaust gas purification catalyst device as described in 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, or 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. An 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, calculated as the mass of ceria per 1 L of substrate volume.

5. An 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, calculated as the mass of ceria per 1 L of substrate volume.

6. An exhaust gas purification catalyst device as described in any one of claims 1 to 5, wherein the first PGM layer is the uppermost layer in direct contact with exhaust gas for a length of at least 10% 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 the uppermost layer in direct contact with exhaust gas for a length of at least 20% of the entire length of the substrate from the downstream end of the exhaust gas flow of the substrate.

7. The exhaust gas purification catalyst device according to claim 6, 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.

8. An exhaust gas purification catalyst device according to claim 6, wherein the second PGM layer is disposed over a length of 20% to 90% of the entire length of the substrate from the downstream end of the exhaust gas of the substrate.

9. An exhaust gas purification catalyst device as described in claim 6, wherein the first PGM layer is arranged 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 arranged 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 lengths of the first PGM layer and the second PGM layer exceeds the entire 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 in direct contact with the exhaust gas.

10. A method for purifying exhaust gas, comprising arranging an exhaust gas purification catalyst device according to any one of claims 1 to 5 in an exhaust system of a gasoline engine, and purifying exhaust gas discharged from the gasoline engine.

11. An exhaust gas purification catalyst system for a gasoline engine, comprising: an upstream purification catalyst device arranged on the upstream side of the exhaust gas flow in the exhaust system of a gasoline engine; and a downstream purification catalyst device arranged on the downstream side of the exhaust gas flow in the exhaust system, wherein the upstream purification catalyst device is a three-way exhaust gas purification catalyst device containing a platinum group catalytic precious metal, and the downstream purification catalyst device is the exhaust gas purification catalyst device according to any one of claims 1 to 5.

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

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