Layered catalyst article and method for manufacturing the catalyst article

Abstract

The present invention relates to a layered catalyst article, particularly useful for three-way conversion, comprising: a) a top layer having a front section and a rear section, the front section comprising a palladium component and a rhodium component supported individually or together on a support, and the rear section comprising a platinum component, a rhodium component, and optionally a palladium component supported individually or together on a support, b) a bottom layer comprising a platinum component and a palladium component supported individually or together on a support, and c) a substrate, wherein the palladium component and the platinum component are present in the layered catalyst article in a Pd / Pt mass ratio, calculated as elemental palladium and platinum, ranging from about 20:1 to about 5:4. The present invention also relates to an exhaust treatment system comprising the layered catalyst article, and to a method of using the layered catalyst article for the reduction of hydrocarbons, carbon monoxide, and nitrogen oxides in an exhaust stream.

Description

[Technical Field]

[0001] The present invention relates to a layered catalyst article useful for treating exhaust gases and a method for manufacturing the layered catalyst article. In particular, the present invention relates to a layered catalyst article having a regionized structure and a method for manufacturing the same. [Background technology]

[0002] To meet emission standards for unburned hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NOx), catalytic converters containing ternary conversion (TWC) catalysts (hereinafter interchangeably referred to as TWC catalysts or TWC) have been used for several years. TWC catalysts are well known as catalysts that simultaneously oxidize unburned hydrocarbons and carbon monoxide in the exhaust flow from internal combustion engines, especially gasoline engines, and reduce nitrogen oxides.

[0003] TWC catalysts utilize platinum group metals (PGMs) as catalytic active species. Palladium, in particular, is typically used as a major platinum group metal, along with small amounts of rhodium. In recent years, the supply shortage of palladium has become severe, leading to a continuous rise in palladium prices, which are approximately 2.6 times higher than platinum. This has created a significant challenge in the TWC catalyst field, increasing manufacturing costs. Simultaneously, a decline in platinum prices is expected due to the decreasing production volume of diesel-powered vehicles that typically use diesel oxidation catalysts containing platinum as the main catalytic active species. Therefore, TWC catalysts containing platinum in place of at least some of the palladium are desirable for significantly reducing catalyst costs. However, simply replacing palladium with platinum is expected to result in undesirable or unsatisfactory catalyst performance. Over the past several decades, various TWC catalysts containing different amounts of platinum have been developed.

[0004] As regulations on engine emissions become increasingly stringent, there is a continuing need for TWC catalysts that can efficiently remove HC, CO, and NOx while being manufactured at a reduced cost. [Overview of the project] [Problems that the invention aims to solve]

[0005] The object of the present invention is to provide a catalyst article containing platinum for replacing the amount of palladium used in a TWC catalyst, which has overall catalytic performance equivalent to or even improved with respect to the reduction of HC, CO, and NOx. [Means for solving the problem]

[0006] Therefore, the present invention is as follows: a) A top layer comprising a front section and a rear section, wherein the front section comprises palladium and rhodium components supported individually or together on a support, and the rear section comprises platinum, rhodium, and optionally palladium components supported individually or together on a support, b) A bottom layer comprising platinum and palladium components supported individually or together on a support, c) Base material This provides a layered catalyst article containing the following: Here, the palladium and platinum components are present in the layered catalyst article in a Pd / Pt mass ratio ranging from approximately 20:1 to approximately 5:4, calculated as palladium and platinum elements.

[0007] In another embodiment, the present invention provides a method for producing a layered catalyst article as described herein, the method being - A step of depositing a bottom coat slurry onto a substrate to obtain a bottom layer, - A step of obtaining the front region of the top layer by depositing a top coat front region slurry from one end of the substrate onto a bottom layer of a certain length, - A step of depositing a topcoat rear region slurry onto the bottom layer of the remaining length of the substrate to obtain the rear region of the top layer. Includes.

[0008] In a further embodiment, the present invention provides an exhaust treatment system comprising a layered catalyst article described herein, located downstream of a gasoline engine.

[0009] In yet another embodiment, the present invention provides a method for treating an exhaust flow, comprising bringing the exhaust flow into contact with a layered catalyst article or exhaust treatment system described herein. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1A is a schematic diagram of an exemplary layered Pd / Rh2 metal catalyst article prepared according to Example 1.

[0011] Figure 1B is a schematic diagram of an exemplary layered Pd / Pt / Rh trimetal catalyst article prepared according to Example 2. [Figure 2] Figure 2A is a schematic diagram of an exemplary layered Pd / Rh2 metal catalyst article prepared according to Example 3.

[0012] Figure 2B is a schematic diagram of an exemplary layered Pd / Pt / Rh trimetal catalyst article prepared according to Example 4. [Figure 3] Figure 3A is a schematic diagram of layered and regionalized Pd / Pt / Rh3 metal catalyst article designs according to several embodiments of the present invention. Figure 3B is a schematic diagram of an exemplary layered and regionalized Pd / Pt / Rh3 catalyst article prepared according to Example 5. [Figure 4] Figure 4A is a schematic diagram of an exemplary layered and regionly structured Pd / Rh2 metal catalyst article prepared according to Example 6. Figure 4B is a schematic diagram of an exemplary layered and regionly structured Pd / Pt / Rh3 metal catalyst article prepared according to Example 7. [Figure 5] Figure 5 is a schematic diagram of an exemplary layered and regioned Pd / Pt / Rh trimetal catalyst article prepared according to Example 8. [Figure 6] Figure 6 is a graph showing the tailpipe emissions in terms of THC, CO, and NOx after treating the engine exhaust with the Group 1 samples. [Figure 7]Figure 7 is a graph showing the tailpipe emissions in terms of THC, CO, and NOx after treating the engine exhaust with the Group 2 samples. [Figure 8] Figure 8 is a graph showing the tailpipe emissions in terms of THC, CO, and NOx after treating the engine exhaust for the Group 3 samples. [Figure 9] Figure 9 is a graph showing the tailpipe emissions in terms of THC, CO, and NOx after treating the engine exhaust for the Group 4 samples. [Figure 10] Figure 10 is a graph showing the tailpipe emissions in terms of THC, CO, and NOx after treating the engine exhaust for the Group 5 samples. [Modes for carrying out the invention]

[0013] The present invention is described in detail below. It should be understood that the present invention can be embodied in many different ways and is not construed as being limited to the embodiments described herein.

[0014] The singular forms "a," "an," and "the" include multiple references unless the context clearly indicates otherwise. Terms such as "contains" and "includes" are used interchangeably with "contains" and "includes," and are interpreted in a non-restrictive and open manner; that is, for example, there may be further components or elements. Expressions such as "consist of" or "essentially consist of" or their synonyms may be encompassed within "contains" or its synonyms.

[0015] The term "about" as used throughout this specification is used to describe and explain small variations that do not significantly alter the physicochemical properties. For example, the term "about" refers to ±5% or less, e.g., ±2% or less, ±1% or less, ±0.5% or less, ±0.2% or less, ±0.1% or less, or ±0.05% or less. The value modified by the term "about" of course includes a specific value. For example, "about 5.0" must include 5.0.

[0016] The terms "palladium component," "platinum component," and "rhodium component" are intended to describe the presence of these platinum group metals in any possible valency state, which may be, for example, the respective metal or metal oxide in a catalytically active form, or the respective metal compounds, complexes, etc., which decompose or convert to a catalytically active form during catalytic combustion or use.

[0017] The term "layered catalyst article" refers to a catalyst article in which the substrate is coated with a catalyst composition in layers.

[0018] The term "forward area" is used interchangeably with "inlet area" and refers to the first area into which the exhaust flow from the engine makes contact. The term "rear area" is used interchangeably with "outlet area" and refers to the area following the first area into which the exhaust flow from the first area makes contact.

[0019] The term "NOx" refers to nitrogen oxides, such as NO and / or NO2.

[0020] According to one aspect of the present invention, a layered catalyst article is provided, which is as follows: a) A top layer comprising a front section and a rear section, wherein the front section comprises palladium and rhodium components supported individually or together on a support, and the rear section comprises platinum, rhodium, and optionally palladium components supported individually or together on a support, b) A bottom layer comprising platinum and palladium components supported individually or together on a support, c) base material; Includes, Here, the palladium and platinum components are present in the layered catalyst article in a Pd / Pt mass ratio ranging from approximately 20:1 to approximately 5:4, calculated as palladium and platinum elements.

[0021] The layered catalyst article according to the present invention is effective for carrying out ternary conversion (TWC).

[0022] In some embodiments, the forward region of the top layer in the layered catalyst article according to the present invention is substantially free of platinum components or substantially free of any PGMs other than Pd and Rh. Alternatively or additionally, the backward region of the top layer in the layered catalyst article according to the present invention contains platinum components, rhodium components and palladium components. Furthermore, the backward region of the top layer in the layered catalyst article according to the present invention is substantially free of any PGMs other than Pt, Pd and Rh. Alternatively or additionally, the bottom layer in the layered catalyst article according to the present invention is substantially free of rhodium components or substantially free of any PGMs other than Pt and Pd.

[0023] References to areas or layers substantially free of PGMs are intended to mean that the identified PGMs are not intentionally added to or used in that area or layer. Those skilled in the art will understand that the migration of trace amounts of PGMs to an area or layer may occur inadvertently during loading, coating, and / or calcination, and that trace amounts of the identified PGMs may be present in the area or layer. Generally, there are less than 1 wt% of the identified PGMs, such as less than 0.75 wt%, less than 0.5 wt%, less than 0.25 wt%, or less than 0.1 wt%.

[0024] According to the present invention, there are no particular limitations on the relative lengths of the front and rear sections. In some embodiments, the top layer is sectioned such that the front section covers about 20 to about 70% of the substrate length and the rear section covers about 30 to about 80% of the substrate length. In some other embodiments, the top layer is sectioned such that the front section covers about 30 to about 60% of the substrate length and the rear section covers about 40 to about 70% of the substrate length. In some further embodiments, the top layer is sectioned such that the front section covers about 30 to about 50% of the substrate length and the rear section covers about 50 to about 70% of the substrate length. The front and rear sections may be strictly adjacent, but it will be understood that they may alternatively overlap or be interrupted by a gap, depending on the precision of the process of applying the coating to the two sections of the top layer.

[0025] The mass ratio of palladium to platinum components in the layered catalyst article according to the present invention may vary in the range of about 20:1 to about 5:4, calculated as palladium and platinum elements. For example, the mass ratio of palladium to platinum components in the layered catalyst article may be about 4:3 or more, about 3:2 or more, or about 2:1 or more. The mass ratio of palladium to platinum components in the layered catalyst article may be about 15:1 or less, about 10:1 or less, about 6:1 or less, about 5:1 or less, or about 4:1 or less. Therefore, in some preferred embodiments, the palladium and platinum components may be included in the layered catalyst article according to the present invention in a Pd / Pt mass ratio of about 15:1 to about 4:3, about 10:1 to about 3:2, about 6:1 to about 3:2, about 5:1 to about 2:1, or about 4:1 to about 2:1, calculated as palladium and platinum elements.

[0026] In the layered catalyst article according to the present invention, there are no particular restrictions on the mass ratio of the rhodium component to the palladium component or the platinum component or the total mass of the palladium component and the platinum component. For example, in the layered catalyst article according to the present invention, the mass ratio of the rhodium component to the total mass of the palladium component and the platinum component may be in the range of about 2:3 to about 1:200, about 1:2 to about 1:50, about 1:3 to about 1:20, or about 1:3 to about 1:10 when calculated for each element.

[0027] In the layered catalyst article according to the present invention, the mass ratio of palladium component to platinum component to rhodium component may be, for example, in the range of about 10:1:0.2 to about 2:1:1, or about 5:1:0.5 to about 2:1:1, when calculated for each element.

[0028] In the bottom layer on the substrate of the layered catalyst article according to the present invention, the palladium component is calculated as approximately 1 to approximately 250 g / ft of palladium element. 3 , about 5~150g / ft 3 , or approximately 5 to 100 g / ft 3 It may be loaded in the following quantity. The platinum component, calculated as elemental platinum, should be approximately 0.5 to 150 g / ft. 3 , about 1~100g / ft 3 , or approximately 5 to 50 g / ft 3It may be loaded in an amount of. In particular, the palladium component and the platinum component may be present in the bottom layer on the substrate in the layered catalyst article according to the present invention in a range of about 3:1 to about 2:3, or a Pd / Pt mass ratio of about 2.5:1 to about 1:1, calculated as palladium element and platinum element.

[0029] In the top layer of the layered catalyst article according to the present invention, the palladium component is calculated as palladium element in an amount of about 0.5 to about 250 g / ft 3 about 1 to about 150 g / ft 3 or about 2 to about 100 g / ft 3 and may be loaded into each area. The loading amount of the palladium component may be the same or different in the front area and the rear area. The rhodium component is calculated as rhodium element in an amount of about 0.5 to about 100 g / ft 3 about 1 to about 50 g / ft 3 or about 2 to about 20 g / ft 3 and may be loaded into each area. The loading amount of the rhodium component may also be the same or different in the front area and the rear area. The platinum component is calculated as platinum element in an amount of about 0.5 to about 150 g / ft 3 about 1 to about 100 g / ft 3 or about 5 to about 50 g / ft 3 and may be loaded in an amount of.

[0030] In some specific embodiments, the platinum component in the rear area of the top layer may include about 30% to about 70%, about 40% to about 60%, or about 50% of the total amount of the platinum component in the layered catalyst article according to the present invention.

[0031] In the forward region of the top layer of the layered catalyst article according to the present invention, the palladium component and the rhodium component may be loaded in a Pd / Rh mass ratio of approximately 50:1 to approximately 1:1, approximately 10:1 to approximately 1.5:1, approximately 5:1 to approximately 1.5:1, or approximately 4:1 to approximately 2:1, calculated as palladium element and rhodium element. In the backward region of the top layer of the layered catalyst article according to the present invention, the platinum component and the rhodium component may be loaded in a Pt / Rh mass ratio of approximately 10:1 to approximately 1:5, approximately 2:1 to approximately 1:2, or approximately 1.5:1 to approximately 1:1.5, calculated as platinum element and rhodium element.

[0032] The total load capacity of the top layer is approximately 1.5-4.0 g / in. 3 Or approximately 2-3 g / in 3 Within this range, the loading amount in the bottom layer should be approximately 0.75-2.0 g / in. 3 It is within the range of [the specified range].

[0033] In the context of the present invention, “support” refers to a material that accepts and supports one or more platinum group metals, which may accept and support other components, such as stabilizers, accelerators, and binders. The support is selected from refractory metal oxides, oxygen storage components, and any combination thereof.

[0034] Refractory metal oxides are widely used as supports for platinum group metals in exhaust gas treatment catalyst articles, and are generally high-surface-area alumina-based materials, zirconia-based materials, or combinations thereof. In the context of this invention, “alumina-based material” means a material containing alumina as a base and any dopant. Similarly, “zirconia-based material” refers to a material containing zirconia as a base and any dopant.

[0035] Suitable examples of alumina-based materials include, but are not limited to, alumina, mixtures of gamma and delta phases of alumina which may contain substantial amounts of ethanol, kappa and theta-alumina phases, lantana-doped alumina, barrier-doped alumina, ceria-doped alumina, zirconia-doped alumina, ceria-zirconia-doped alumina, lantana-zirconia-doped alumina, barrier-lantana-doped alumina, barrier-lantana-neodymia-doped alumina, and any combination thereof. Suitable examples of zirconia-based materials include, but are not limited to, zirconia, lantana-doped zirconia, yttria-doped zirconia, neodymia-doped zirconia, praseodymia-doped zirconia, titania-doped zirconia, titania-lantana-doped zirconia, lantana-yttria-doped zirconia, and any combination thereof. For example, refractory metal oxides are selected from alumina, lantana-doped alumina, lantana-zirconia-doped alumina, ceria-doped alumina, zirconia-doped alumina, ceria-zirconia-doped alumina, zirconia, lantana-doped zirconia, lantana-yttria-doped zirconia, and any combination thereof. Generally, the amount of refractory metal oxide is 10 to 90 wt% based on the total mass of the bottom or top layer.

[0036] Oxygen storage components (OSCs) refer to entities that have a polyvalent state and can react actively with oxidizing agents, such as oxygen or nitrogen oxides, under oxidizing conditions, or with reducing agents, such as carbon monoxide (CO) or hydrogen, under reducing conditions. Typically, OSCs include one or more reducible rare earth metal oxides, such as ceria. OSCs include one or more of lantana, praseodymia, neodymia, europia, samaria, ytterbia, yttria, zirconia, hafnia, and any combination thereof, to constitute a complex oxide with ceria. Preferably, the oxygen storage components are selected from ceria-zirconia complex oxides and rare earth-stabilized ceria-zirconia complex oxides. Generally, the amount of oxygen storage components is 20 to 80 wt% based on the total mass of the bottom or top layer.

[0037] Please understand that the supports for the platinum, palladium, and rhodium components in the layered catalyst article may be the same or different. Similarly, the supports for the same platinum group metal in different layers or regions within the layered catalyst article may be the same or different.

[0038] In some embodiments, the layered catalyst article according to the present invention is as follows: a) A top layer comprising a front section and a rear section, wherein the front section comprises palladium and rhodium components supported individually or together on a support, and the rear section comprises platinum, palladium, and rhodium components supported individually or together on a support, b) A bottom layer comprising platinum and palladium components supported individually or together on a support, c) base material; Includes, Here, the support in each case is independently a refractory metal oxide selected from alumina, lantana-doped alumina, lantana-zirconia-doped alumina, ceria-doped alumina, zirconia, zirconia-doped alumina, ceria-zirconia-doped alumina, lantana-doped zirconia and lantana-yttria-doped zirconia, an oxygen storage component selected from ceria-zirconia composite oxide and rare earth-stabilized ceria-zirconia composite oxide, or any combination thereof, and The palladium and platinum components are present in the layered catalyst article in a Pd / Pt mass ratio ranging from approximately 20:1 to approximately 5:4, calculated as palladium and platinum elements.

[0039] In some exemplary embodiments, the layered catalyst article according to the present invention is as follows: a) A top layer comprising a front section and a rear section, wherein the front section comprises a palladium component individually supported by a combination of alumina and an oxygen storage component, and a rhodium component individually supported by a combination of alumina or zirconia and an oxygen storage component, and the rear section comprises a palladium component individually supported by a combination of alumina and an oxygen storage component, a platinum component supported by an oxygen storage component, and a rhodium component, wherein a portion of the rhodium component is supported by the oxygen storage component together with the platinum component, and the remaining portion of the rhodium component is supported by alumina or zirconia, where In each case, the oxygen storage component is independently selected from ceria-zirconia composite oxide and rare-earth stabilized ceria-zirconia composite oxide, in the top layer. b) A bottom layer comprising a platinum component and a palladium component, wherein the platinum component, together with a portion of the palladium component, is supported by ceria-doped alumina, and the remaining portion of the palladium component is supported by an oxygen storage component selected from ceria-zirconia composite oxide and rare-earth stabilized ceria-zirconia composite oxide, and c) Base material Includes, Here, the palladium and platinum components are present in the layered catalyst article in Pd / Pt mass ratios ranging from approximately 20:1 to approximately 5:4, approximately 15:1 to approximately 4:3, approximately 10:1 to approximately 3:2, approximately 6:1 to approximately 3:2, approximately 5:1 to approximately 2:1, or approximately 4:1 to approximately 2:1, calculated as palladium and platinum elements.

[0040] According to the exemplary embodiments described above, the palladium component supported by the oxygen storage component in the bottom layer may comprise about 50% to about 95% or about 70% to about 95% of the total amount of palladium component in the bottom layer. Alternatively or additionally, the rhodium component supported by the oxygen storage component in the rear section of the top layer may comprise about 50% to about 90% or about 60% to about 80% of the total amount of rhodium component in the rear section.

[0041] In some specific embodiments of the layered catalyst article according to the present invention, the bottom layer is applied to a substrate, and the top layer is applied to the bottom layer without any intermediate layer.

[0042] The substrate used here typically refers to a structure suitable for withstanding the conditions encountered in the exhaust flow of a combustion engine, on which a catalyst composition is supported, usually in the form of a washcoat. The substrate is generally a ceramic or metal honeycomb structure with fine, parallel gas passages extending from one end of the structure to the other.

[0043] The term "wash coat" has its common meaning in the art and refers to a thin coating of a catalyst or other material applied to a substrate. Wash coats are generally formed by preparing a slurry containing a certain amount of solid particles (e.g., 15-60% by mass) in a liquid medium, which is then applied to a substrate, dried, and calcined to provide a wash coat layer.

[0044] Metallic materials useful for forming the base material include heat-resistant metals and metal alloys, such as titanium and stainless steel, as well as other alloys in which iron is a substantial or major component. Such alloys may contain one or more nickel, chromium, and / or aluminum, and the total amount of these metals may, advantageously, contain at least 15 wt% of the alloy, for example, 10-25 wt% of chromium, 3-8% of aluminum, and 20 wt% or less of nickel. The alloy may also contain small or trace amounts of one or more metals, such as manganese, copper, vanadium, titanium, etc. The surface of the metal base material may be oxidized at a high temperature, for example, 1000°C or higher, to form an oxide layer on the surface of the base material, thereby improving the corrosion resistance of the alloy and facilitating the adhesion of the wash coat layer to the metal surface.

[0045] Useful ceramic materials for constructing the substrate include any suitable refractory material, such as cordierite, mullite, cordierite-alumina, silicon nitride, zircon mullite, spodumene, alumina-silica-magnesia, zircon silicate, sillimanite, magnesium silicate, zircon, petalite, alumina, and aluminosilicate.

[0046] In the context of the present invention, a monolithic flow-through substrate is preferred, which is a substrate having a plurality of fine, parallel gas flow channels extending from an inlet to an outlet surface of the substrate, with the channels open to the flow of fluid through them. The channels are essentially linear paths from their fluid inlet to their fluid outlet and are defined by walls to which a catalytic material is applied as a wash coat so that the gas flowing through the channels comes into contact with the catalytic material. The flow channels of the monolithic substrate are thin-walled channels and can have any preferred cross-sectional shape and size, e.g., trapezoidal, rectangular, square, sinusoidal, hexagonal, elliptical, circular, etc. Such a structure may contain about 60 to about 900 or more gas inlet openings (i.e., cells) per square inch of cross-section. For example, a substrate may have about 400 to 900, more typically about 600 to 750 cells / square inch ("cpsi"). The wall thickness of the flow-through substrate may vary, typically ranging from 2 mil to 0.1 inch. Typical commercially available flow-through substrates are cordierite substrates having a cell density of 750 cpsi and a wall thickness of 2 mils, or a cell density of 600 cpsi and a wall thickness of 4 mils.

[0047] The substrate is a wall-flow substrate having multiple fine, parallel gas flow channels extending from the inlet to the outlet surface of the substrate, and it is also possible that the alternating channels are blocked at opposite ends. The configuration requires that the gas flow reaches the outlet surface through the porous walls of the wall-flow substrate. The wall-flow substrate may contain about 700 cells / square inch (cpsi) or less, e.g., about 100-400 cpsi, and more typically about 200-300 cpsi. The cross-sectional shape of the cells can vary as described above. The flow channels of the monolithic substrate are thin-walled channels and can have any suitable cross-sectional shape and size, e.g., trapezoidal, rectangular, square, sinusoidal, hexagonal, elliptical, circular, etc. The wall thickness of the wall-flow substrate can vary, with a typical range of 2 mil to 0.1 inches.

[0048] According to another aspect of the present invention, a method for producing a layered catalyst article described herein is provided, which is, - A step of depositing a bottom coat slurry onto a substrate to obtain a bottom layer, - A step of obtaining the front region of the top layer by depositing a top coat front region slurry from one end of the substrate onto a bottom layer of a certain length, - A step of depositing a topcoat rear region slurry onto the bottom layer of the remaining length of the substrate to obtain the rear region of the top layer. Includes.

[0049] Generally, a slurry comprises supported PGM(s) catalyst particles, a solvent (e.g., water), an optional binder, and an optional auxiliary agent, such as a surfactant, pH adjuster, and thickener. For bottom coat slurries, supported platinum and palladium catalyst particles are included. For top coat forward-region slurries, supported platinum and rhodium catalyst particles are included. For top coat backward-region slurries, supported platinum, rhodium, and optional palladium catalyst particles are included. The supports(s) for the PGM in each slurry are as described above herein, generally or specifically, for the layered catalyst articles according to the present invention.

[0050] These supported PGM(s) catalyst particles are prepared by impregnating PGM(s), for example, soluble salts and / or complexes thereof, onto their respective supports via conventional techniques, such as dry impregnation (also called initial wet impregnation or capillary impregnation) or wet impregnation, and optionally subsequently drying and / or calcining. Suitable PGM precursors may be selected from ammine complex salts, hydroxyl salts, nitrates, carboxylates, ammonium salts, and oxides. Non-limiting examples include palladium nitrate, tetraamminepalladium nitrate, rhodium nitrate, tetraammineplatinum acetate, and platinum nitrate, tetraammineplatinum acetate, hexahydroxyplatinate diethanolamine salt ((HOCH2CH2NH3)2[Pt(OH)6]).

[0051] The binder may be selected from alumina, boehmite, silica, zirconium acetate, colloidal zirconia, or zirconium hydroxide. If present, the binder is typically used in an amount of about 0.5 to about 5.0 wt% of the total washcoat load.

[0052] The slurry may have a solid content of, for example, about 20-60 wt%, more specifically about 30-50 wt%. The slurry is often pulverized to reduce particle size. Typically, after pulverization, the slurry is measured by a laser diffraction particle size analyzer to have a particle size of about 3.0-40 microns, preferably about 10-30 microns, more preferably less than 20 microns. 90 It is likely the particle size.

[0053] The deposition of the slurry onto the substrate or undercoat may be carried out by any technique known in the art. For example, the substrate may be immersed in the slurry one or more times, or coated with the slurry to a desired length, then dried at a high temperature (e.g., 100-150°C) for a period of time (e.g., 10 minutes to 3 hours), and then baked at an even higher temperature (e.g., 400-700°C) typically for about 10 minutes to about 3 hours. The amount of washcoat loaded after baking can be determined by finding the mass difference between the coated substrate and the uncoated substrate. As will be apparent to those skilled in the art, the amount of washcoat loaded can be varied by changing the slurry rheology. Furthermore, the deposition process, including coating, drying, and baking to produce the washcoat, can be repeated as needed to build the layer to a desired loading level or thickness, meaning that multiple washcoats may be applied.

[0054] A further embodiment of the present invention provides an exhaust treatment system comprising a layered catalyst article described herein, located downstream of a gasoline engine. The layered catalyst article is located in close proximity downstream of the gasoline engine, downstream of the close proximity, or both.

[0055] According to yet another aspect of the present invention, a method for treating an exhaust flow is provided, which includes bringing the exhaust flow into contact with a layered catalyst article or exhaust treatment system described herein.

[0056] The terms "exhaust flow," "exhaust gas," etc., refer to any engine exhaust gas that may contain solid or liquid particulate matter.

[0057] The layered catalyst article according to the present invention is particularly useful for reducing hydrocarbons, carbon monoxide, and nitrogen oxides in the exhaust flow from a gasoline engine.

[0058] Embodiment Various embodiments are listed below. It will be understood that the embodiments listed below may be combined in any way and in any way with other embodiments within the scope of the present invention.

[0059] Embodiment 1. a) A top layer comprising a front region and a rear region, wherein the front region comprises a palladium component and a rhodium component supported individually or together on a support, and the rear region comprises a platinum component, a rhodium component and optionally a palladium component supported individually or together on a support, b) A bottom layer comprising platinum and palladium components supported individually or together on a support, c) Base material A layered catalyst article particularly useful for ternary conversion, comprising: A layered catalyst article in which palladium and platinum components are present in a Pd / Pt mass ratio in the range of approximately 20:1 to approximately 5:4, calculated as palladium and platinum elements.

[0060] Embodiment 2. The layered catalyst article according to Embodiment 1, wherein the rear region comprises platinum, rhodium, and palladium components supported individually or together on a support.

[0061] Embodiment 3. A layered catalyst article according to Embodiment 1 or 2, wherein the front area of ​​the top layer comprises about 20 to about 70% of the substrate length and the rear area of ​​the top layer comprises about 30 to about 80% of the substrate length, or the front area of ​​the top layer comprises about 30 to about 60% of the substrate length and the rear area of ​​the top layer comprises about 40 to about 70% of the substrate length, or the front area of ​​the top layer comprises about 30 to about 50% of the substrate length and the rear area of ​​the top layer comprises about 50 to about 70% of the substrate length.

[0062] Embodiment 4. A layered catalyst article according to any of the preceding embodiments, wherein the mass ratio of palladium component to platinum component contained in the layered catalyst article may be about 4:3 or more, about 3:2 or more, or about 2:1 or more when calculated as palladium element and platinum element.

[0063] Embodiment 5. A layered catalyst article according to any of the preceding embodiments, wherein the mass ratio of palladium component to platinum component contained in the layered catalyst article may be about 15:1 or less, about 10:1 or less, about 6:1 or less, about 5:1 or less, or about 4:1 or less, calculated as palladium element and platinum element.

[0064] Embodiment 6. A layered catalyst article according to any of the preceding embodiments, wherein the mass ratio of palladium component to platinum component contained in the layered catalyst article is in the range of about 15:1 to about 4:3, or about 10:1 to about 3:2, or about 6:1 to about 3:2, or about 5:1 to about 2:1, or about 4:1 to about 2:1, calculated as palladium and platinum elements.

[0065] Embodiment 7. A layered catalyst article according to any of the preceding embodiments, wherein the mass ratio of the rhodium component to the total mass of the palladium and platinum components in the layered catalyst article may be in the range of about 2:3 to about 1:200, or about 1:2 to about 1:50, or about 1:3 to about 1:20, or about 1:3 to about 1:10, when calculated as each element.

[0066] Embodiment 8. A layered catalyst article according to any of the preceding embodiments, wherein the mass ratio of palladium, platinum, and rhodium components in the layered catalyst article is in the range of approximately 10:1:0.2 to approximately 2:1:1, or approximately 5:1:0.5 to approximately 2:1:1, when calculated for each element.

[0067] Embodiment 9. A layered catalyst article according to any of the preceding embodiments, wherein the mass ratio of palladium to platinum components in the bottom layer is in the range of approximately 3:1 to approximately 2:3 or approximately 2.5:1 to approximately 1:1 when calculated for each element.

[0068] Embodiment 10. A layered catalyst article according to any of the preceding embodiments, wherein palladium and rhodium components are loaded into the forward region of the top layer in a Pd / Rh mass ratio of approximately 50:1 to approximately 1:1, or approximately 10:1 to approximately 1.5:1, or approximately 5:1 to approximately 1.5:1, or approximately 4:1 to approximately 2:1, calculated as individual elements.

[0069] Embodiment 11. A layered catalyst article according to any of the preceding embodiments, wherein platinum and rhodium components are loaded in the rear region of the top layer in a Pt / Rh mass ratio of approximately 10:1 to approximately 1:5, or approximately 2:1 to approximately 1:2, or approximately 1.5:1 to approximately 1:1.5, calculated as individual elements.

[0070] Embodiment 12. A layered catalyst article according to any of the preceding embodiments, wherein the support for each of the platinum, palladium, and rhodium components is independently selected from refractory metal oxides, oxygen storage components, and any combination thereof.

[0071] Embodiment 13. A layered catalyst article according to any of the prior embodiments, wherein: a) A top layer comprising a front section and a rear section, wherein the front section comprises palladium and rhodium components supported individually or together on a support, and the rear section comprises platinum, palladium, and rhodium components supported individually or together on a support, b) A bottom layer comprising platinum and palladium components supported individually or together on a support, c) base material; Includes, Herein, the support in each case is independently a refractory metal oxide selected from alumina, lantana-doped alumina, lantana-zirconia-doped alumina, ceria-doped alumina, zirconia, zirconia-doped alumina, ceria-zirconia-doped alumina, lantana-doped zirconia and lantana-yttria-doped zirconia, an oxygen storage component selected from ceria-zirconia composite oxides and rare earth-stabilized ceria-zirconia composite oxides, or any combination thereof, as described in any of the preceding embodiments.

[0072] Embodiment 14. A layered catalyst article according to any of the prior embodiments, wherein: a) A top layer comprising a front section and a rear section, wherein the front section comprises a palladium component individually supported by a combination of alumina and an oxygen storage component, and a rhodium component individually supported by a combination of alumina or zirconia and an oxygen storage component, and the rear section comprises a palladium component individually supported by a combination of alumina and an oxygen storage component, a platinum component supported by an oxygen storage component, and a rhodium component, wherein a portion of the rhodium component is supported by the oxygen storage component together with the platinum component, and the remaining portion of the rhodium component is supported by alumina or zirconia, where In each case, the oxygen storage component is independently selected from ceria-zirconia composite oxide and rare-earth stabilized ceria-zirconia composite oxide, in the top layer. b) A bottom layer comprising a platinum component and a palladium component, wherein the platinum component, together with a portion of the palladium component, is supported by ceria-doped alumina, and the remaining portion of the palladium component is supported by an oxygen storage component selected from ceria-zirconia composite oxide and rare-earth stabilized ceria-zirconia composite oxide, and c) Base material A layered catalyst article according to any of the prior embodiments, including the following:

[0073] Embodiment 15. A layered catalyst article according to any of the preceding embodiments, wherein the forward region of the top layer substantially does not contain a platinum component, or substantially does not contain any PGM other than Pd and Rh.

[0074] Embodiment 16. A layered catalyst article according to any of the preceding embodiments, wherein the rear region of the top layer substantially does not contain any PGM other than Pd, Pt, and Rh.

[0075] Embodiment 17. A layered catalyst article according to any of the preceding embodiments, wherein the bottom layer substantially does not contain rhodium components, or substantially does not contain any PGM other than Pt and Pd.

[0076] Embodiment 18. A layered catalyst article according to any of the preceding embodiments, wherein the palladium component supported by the oxygen storage component in the bottom layer comprises about 50% to about 95% or about 70% to about 95% of the total amount of palladium component in the bottom layer.

[0077] Embodiment 19. A layered catalyst article according to any of the preceding embodiments, wherein the rhodium component supported by the oxygen storage component in the rear region of the top layer comprises about 50% to about 90% or about 60% to about 80% of the total amount of rhodium component in the rear region.

[0078] Embodiment 20. A layered catalyst article according to any of the preceding embodiments, wherein the platinum component in the rear region of the top layer comprises about 30% to about 70%, or about 40% to about 60%, or about 50% of the total amount of platinum component in the layered catalyst article.

[0079] Embodiment 21. A layered catalyst article according to any of the preceding embodiments, wherein a bottom layer is applied to a substrate and a top layer is applied to the bottom layer without any intermediate layer.

[0080] Embodiment 22. Total loading volume of the top layer is approximately 1.5 to 4.0 g / in.3 The range is approximately 2-3 g / in 3 And the loading capacity of the bottom layer is approximately 0.75~2.0g / in 3 A layered catalyst article according to any of the prior embodiments, within the range of [specified range].

[0081] Embodiment 23. A layered catalyst article according to any of the preceding embodiments, wherein the substrate is a flow-through substrate or a wall-flow substrate, preferably a flow-through substrate.

[0082] Embodiment 24. A method for manufacturing a layered catalyst article according to any of the prior embodiments, comprising the following steps: - A step of depositing a bottom coat slurry onto a substrate to obtain a bottom layer, - A step of obtaining the front region of the top layer by depositing a top coat front region slurry from one end of the substrate onto a bottom layer of a certain length, - A step of depositing a topcoat rear region slurry onto the bottom layer of the remaining length of the substrate to obtain the rear region of the top layer. A method that includes this.

[0083] Embodiment 25. The method according to Embodiment 24, wherein each slurry comprises supported PGM(s) catalyst particles, a solvent, an optional binder, and an optional auxiliary agent.

[0084] Embodiment 26. The method according to Embodiment 24, wherein the supported PGM(s) catalyst particles are prepared by impregnating a support material with a PGM precursor selected from ammine complex salts, hydroxyl salts, nitrates, carboxylates, ammonium salts, and oxides.

[0085] Embodiment 27. The method according to Embodiment 26, wherein the precursor of Pt is hexahydroxyplaty diethanolamine salt ((HOCH2CH2NH3)2[Pt(OH)6]).

[0086] Embodiment 28. A method for using a layered catalyst article according to any one of Embodiments 1 to 23 for reducing hydrocarbons, carbon monoxide, and nitrogen oxides in an exhaust stream.

[0087] Embodiment 29. An exhaust treatment system comprising a layered catalyst article according to any one of Embodiments 1 to 23, located downstream of a gasoline engine.

[0088] Embodiment 30. The exhaust treatment system according to Embodiment 29, wherein the layered catalyst article is located in close proximity downstream of the gasoline engine, under the floor, or both.

[0089] Embodiment 31. The exhaust gas treatment system according to Embodiment 29 or 30, wherein the four-way catalytic converter is directly or indirectly followed by a layered catalytic article.

[0090] Embodiment 32. A method for treating an exhaust flow, comprising bringing the exhaust flow into contact with a layered catalyst article described in any of Embodiments 1 to 23 or an exhaust treatment system described in any of Embodiments 29 to 31.

[0091] Embodiment 33. The method according to Embodiment 32, wherein the layered catalyst article is particularly useful for reducing hydrocarbons, carbon monoxide, and nitrogen oxides in the exhaust flow from a gasoline engine. [Examples]

[0092] Aspects of the present invention are described more fully by the following examples, which are provided to illustrate specific aspects of the invention and are not intended to limit them.

[0093] Example 1 Preparation of layered bimetallic catalyst article (Reference example, BMC-1, Pd / Pt / Rh 50 / 0 / 10, g / ft) 3 ) A catalyst article was prepared containing a bottom coat with palladium (Pd) as the sole PGM and a top coat containing palladium (Pd) and rhodium (Rh) as PGMs. A schematic diagram of this catalyst article is shown in Figure 1A.

[0094] Bottom coat slurry: 18.91 grams of 20% Pd-nitrate aqueous solution was used to impregnate 283 grams of alumina and 700 grams of ceria-zirconia (50% zirconia) via initial wetting impregnation. This product was mixed with water and then D into particles less than 18 μm. 90 It was ground to this extent. After adding nitric acid to adjust the pH to approximately 3.0-4.0, 13 grams of alumina binder was added.

[0095] Topcoat Slurry: The first component was prepared by impregnating 490 grams of alumina and 410 grams of ceria-zirconia (50% zirconia) with 75.65 grams of a 20% Pd-nitrate aqueous solution via initial wetting impregnation. Following this process, the PGM was fixed to the support by drying at 150°C for 1 hour, followed by calcination at 500°C for 2 hours. The product was mixed with water and then D into particles less than 18 μm. 90 It was pulverized to that extent.

[0096] The second component was prepared by impregnating 250 grams of alumina and 410 grams of ceria-zirconia (50% zirconia) with 37.83 grams of a 10% Rh-nitrate aqueous solution via initial wetting impregnation. This product was mixed with water and D 90 The material was ground down to a size of 18 μm or less.

[0097] Two components in slurry form were blended. After adjusting the pH to approximately 7.0-9.0 by adding barium hydroxide and nitric acid, 20 grams of alumina binder were added.

[0098] This bottom coat slurry was applied to a 750 / 2 (cpsi / mill) flow-through ceramic substrate with a diameter of 118.4 mm and a length of 90 mm, dried at 150°C for 1 hour, and then baked at 500°C for 2 hours. The wash coat loading amount was 1.53 g / in. 3 The bottom coating has a Pd load capacity of 10g / ft 3A bottom coat was obtained. Next, a top coat slurry was applied and dried at 150°C for 1 hour, then baked at 500°C for 2 hours. The wash coat loading amount was 2.45 g / in. 3 A top coat is obtained, and the PGM load of the top coat is 40g / ft 3 Pd and 10g / ft 3 It consisted of Rh.

[0099] Example 2 Preparation of a layered tri-metal catalyst article (Reference example, TMC-1, Pd / Pt / Rh 40 / 10 / 10, g / ft) 3 ) A catalyst article was prepared containing a bottom coat with palladium (Pd) as the sole PGM, and a top coat containing palladium (Pd), platinum (Pt), and rhodium (Rh) as PGMs. A schematic diagram of this catalyst article is shown in Figure 1B. This catalyst article (TMC-1) represents a modification of catalyst article (BMC-1) by simply replacing 20% ​​Pd in ​​the top coat with Pt.

[0100] Bottom coat slurry: 18.91 grams of 20% Pd-nitrate aqueous solution was used to impregnate 283 grams of alumina and 700 grams of ceria-zirconia (50% zirconia) via initial wetting impregnation. This product was mixed with water and then D into particles less than 18 μm. 90 It was ground to this extent. After adding nitric acid to adjust the pH to approximately 3.0-4.0, 13 grams of alumina binder was added.

[0101] Topcoat Slurry: The first component was prepared by first impregnating 490 grams of alumina and 410 grams of ceria-zirconia (50% zirconia) with 7.09 grams of an aqueous solution of 16% hexahydroxyplaty diethanolamine salt via initial wetting impregnation, and then impregnating with 56.75 grams of an aqueous solution of 20% Pd-nitrate. Following this process, the PGM was fixed to the support by drying at 150°C for 1 hour, followed by calcination at 500°C for 2 hours. The product was mixed with water and then D into a material less than 18 μm thick. 90 It was pulverized to that extent.

[0102] The second component was prepared by impregnating 250 grams of alumina and 410 grams of ceria-zirconia (50% zirconia) with 37.83 grams of an aqueous solution of 10% Rh-nitrate via initial wetting impregnation, and then impregnating with 16.55 grams of an aqueous solution of 16% hexahydroxyplaty diethanolamine salt. This product was mixed with water and then fermented to a size of less than 18 μm. 90 It was pulverized to that extent.

[0103] Two components in slurry form were blended. After adjusting the pH to approximately 7.0-9.0 by adding barium hydroxide and nitric acid, 20 grams of alumina binder were added.

[0104] This bottom coat slurry was applied to a 750 / 2 (cpsi / mill) flow-through ceramic substrate with a diameter of 118.4 mm and a length of 90 mm, dried at 150°C for 1 hour, and then baked at 500°C for 2 hours. The wash coat loading amount was 1.53 g / in. 3 The bottom coating has a Pd load capacity of 10g / ft 3 A bottom coat was obtained. Next, a top coat slurry was applied and dried at 150°C for 1 hour, then baked at 500°C for 2 hours. The wash coat loading amount was 2.45 g / in. 3 A top coat is obtained, and the PGM load of the top coat is 30g / ft 3 Pd, 10g / ft 3 Pt and 10g / ft 3 It consisted of Rh.

[0105] Example 3 Preparation of a layered two-metal catalyst article (Reference example, BMC-2, Pd / Pt / Rh 100 / 0 / 14, g / ft) 3 ) A catalyst article was prepared containing a bottom coat with palladium (Pd) as the sole PGM and a top coat containing palladium (Pd) and rhodium (Rh) as PGMs. A schematic diagram of this catalyst article is shown in Figure 2A.

[0106] Bottom coat slurry: 47.02 grams of 20% Pd-nitrate aqueous solution was used to impregnate 283 grams of alumina and 700 grams of ceria-zirconia (50% zirconia) via initial wetting impregnation. This product was mixed with water and then divided into layers less than 18 μm. 90 It was ground to this extent. After adding nitric acid to adjust the pH to approximately 3.0-4.0, 13 grams of alumina binder was added.

[0107] Topcoat Slurry: The first component was prepared by impregnating 490 grams of alumina and 410 grams of ceria-zirconia (50% zirconia) with 141.06 grams of a 20% Pd-nitrate aqueous solution via initial wetting impregnation. Following this process, the PGM was fixed to the support by drying at 150°C for 1 hour, followed by calcination at 500°C for 2 hours. The product was mixed with water and then D into a material less than 18 μm thick. 90 It was pulverized to that extent.

[0108] The second component was prepared by impregnating 250 grams of alumina and 410 grams of ceria-zirconia (50% zirconia) with 52.66 grams of a 10% Rh-nitrate aqueous solution via initial wetting impregnation. This product was mixed with water and D 90 The material was ground down to a size of 18 μm or less.

[0109] Two components in slurry form were blended. After adjusting the pH to approximately 7.0-9.0 by adding barium hydroxide and nitric acid, 20 grams of alumina binder were added.

[0110] This bottom coat slurry was applied to a 750 / 2 (cpsi / mil) flow-through ceramic substrate with a diameter of 101.6 mm and a length of 118 mm, dried at 150°C for 1 hour, and then baked at 500°C for 2 hours. The wash coat loading amount was 1.54 g / in. 3 The bottom coating has a Pd load capacity of 25g / ft 3A bottom coat was obtained. Next, a top coat slurry was applied and dried at 150°C for 1 hour, then baked at 500°C for 2 hours. The wash coat loading amount was 2.47 g / in. 3 A top coat is obtained, and the PGM load of the top coat is 75g / ft 3 Pd and 14g / ft 3 It consisted of Rh.

[0111] Three samples were prepared following this process.

[0112] Example 4 Preparation of a layered three-metal catalyst article (Reference example, TMC-2, Pd / Pt / Rh 80 / 20 / 14, g / ft) 3 ) A catalyst article representing a deformation of catalyst article (BMC-2) was prepared by replacing 20% ​​of the total Pd load with Pt and placing the Pt in the bottom coat. A schematic diagram of this catalyst article is shown in Figure 2B.

[0113] Bottom coat slurry: The first component was prepared by first impregnating 283 grams of ceria-alumina (90% alumina) with 46.67 grams of an aqueous solution of 16% hexahydroxyplaty diethanolamine salt via initial wetting impregnation, and then impregnating with 7.47 grams of an aqueous solution of 20% Pd-nitrate. Following this process, the PGM was fixed to the support by drying at 150°C for 1 hour, followed by calcination at 500°C for 2 hours. The product was mixed with water and then D less than 18 μm 90 It was pulverized to that extent.

[0114] The second component was prepared by impregnating 700 grams of ceria-zirconia (50% zirconia) with 39.20 grams of a 20% Pd-nitrate aqueous solution via initial wetting impregnation. This product was mixed with water and D 90 The material was ground down to a size of 18 μm or less. Two components in slurry form were blended. Nitric acid was added to adjust the pH to approximately 3.0-4.0, and then 13 grams of alumina binder were added.

[0115] Topcoat Slurry: The first component was prepared by impregnating 490 grams of alumina and 410 grams of ceria-zirconia (50% zirconia) with 102.67 grams of a 20% Pd-nitrate aqueous solution via initial wetting impregnation. Following this process, the PGM was fixed to the support by drying at 150°C for 1 hour, followed by calcination at 500°C for 2 hours. The product was mixed with water and then D into particles less than 18 μm. 90 It was pulverized to that extent.

[0116] The second component was prepared by impregnating 250 grams of alumina and 410 grams of ceria-zirconia (50% zirconia) with 52.27 grams of a 10% Rh-nitrate aqueous solution via initial wetting impregnation. This product was mixed with water and D 90 The material was ground down to a size of 18 μm or less.

[0117] Two components in slurry form were blended. After adjusting the pH to approximately 7.0-9.0 by adding barium hydroxide and nitric acid, 20 grams of alumina binder were added.

[0118] This bottom coat slurry was applied to a 750 / 2 (cpsi / mil) flow-through ceramic substrate with a diameter of 101.6 mm and a length of 118 mm, dried at 150°C for 1 hour, and then baked at 500°C for 2 hours. The wash coat loading amount was 1.55 g / in. 3 A bottom coat is obtained, and the PGM load of the bottom coating is 20g / ft 3 Pt and 25g / ft 3 It consisted of Pd. Next, a topcoat slurry was applied, dried at 150°C for 1 hour, and then baked at 500°C for 2 hours. The washcoat load was 2.46 g / in. 3 A top coat is obtained, and the PGM load of the top coat is 55 g / ft 3 Pd and 14g / ft 3 It consisted of Rh.

[0119] Example 5 Preparation of a layered three-metal catalyst article (Example of the present invention, TMC-3, Pd / Pt / Rh 80 / 20 / 14, g / ft 3 ) A catalyst article according to the present invention was prepared, comprising a bottom coat having palladium (Pd) and platinum (Pt) as PGMs, and a top coat having palladium (Pd) and rhodium (Rh) as PGMs in the front region, and palladium (Pd), platinum (Pt), and rhodium (Rh) as PGMs in the rear region. A schematic diagram of this catalyst article is shown in Figure 3B.

[0120] Bottom coat slurry: The first component was prepared by first impregnating 283 grams of ceria-alumina (90% alumina) with 23.42 grams of an aqueous solution of 16% hexahydroxyplaty diethanolamine salt via initial wetting impregnation, and then impregnating with 3.75 grams of an aqueous solution of 20% Pd-nitrate. Following this process, the PGM was fixed to the support by drying at 150°C for 1 hour, followed by calcination at 500°C for 2 hours. The product was mixed with water and then D into a material less than 18 μm thick. 90 It was pulverized to that extent.

[0121] The second component was prepared by impregnating 700 grams of ceria-zirconia (50% zirconia) with 43.10 grams of a 20% Pd-nitrate aqueous solution via initial wetting impregnation. This product was mixed with water and D 90 The material was ground down to a size of 18 μm or less. Two components in slurry form were blended. Nitric acid was added to adjust the pH to approximately 3.0-4.0, and then 13 grams of alumina binder were added.

[0122] Topcoat forward area slurry: The first component was prepared by impregnating 490 grams of alumina and 410 grams of ceria-zirconia (50% zirconia) with 103.06 grams of a 20% Pd-nitrate aqueous solution via initial wetting impregnation. Following this process, the PGM was fixed to the support by drying at 150°C for 1 hour, followed by calcination at 500°C for 2 hours. The product was mixed with water and then D into a material less than 18 μm thick. 90 It was pulverized to that extent.

[0123] The second component was prepared by impregnating 250 grams of alumina and 410 grams of ceria-zirconia (50% zirconia) with 52.46 grams of a 10% Rh-nitrate aqueous solution via initial wetting impregnation. This product was mixed with water and D 90 The material was ground down to a size of 18 μm or less.

[0124] Two components in slurry form were blended. After adjusting the pH to approximately 7.0-9.0 by adding barium hydroxide and nitric acid, 20 grams of alumina binder were added.

[0125] Topcoat rear area slurry: The first component was prepared by impregnating 490 grams of alumina and 410 grams of ceria-zirconia (50% zirconia) with 103.06 grams of a 20% Pd-nitrate aqueous solution via initial wetting impregnation. Following this process, the PGM was fixed to the support by drying at 150°C for 1 hour, followed by calcination at 500°C for 2 hours. The product was mixed with water and then D into a material less than 18 μm thick. 90 It was pulverized to that extent.

[0126] The second component was prepared by impregnating 250 grams of alumina with 22.24 grams of a 10% Rh-nitrate aqueous solution via initial wetting impregnation. This product was mixed with water and D 90 The material was ground down to a size of 18 μm or less.

[0127] The third component was prepared via initial wetting impregnation, first by impregnating 410 grams of ceria-zirconia (50% zirconia) with 30.22 grams of a 10% Rh-nitrate aqueous solution, and then by impregnating with 46.84 grams of a 16% hexahydroxyplaty diethanolamine salt aqueous solution. Following this process, the PGM was fixed to the support by drying at 150°C for 1 hour, followed by calcination at 500°C for 2 hours. The product was mixed with water and then D into a material less than 18 μm thick. 90 It was pulverized to that extent.

[0128] Three components in slurry form were blended. After adjusting the pH to approximately 7.0-9.0 by adding barium hydroxide and nitric acid, 20 grams of alumina binder were added.

[0129] This bottom coat slurry was applied to a 750 / 2 (cpsi / mil) flow-through ceramic substrate with a diameter of 101.6 mm and a length of 118 mm, dried at 150°C for 1 hour, and then baked at 500°C for 2 hours. The wash coat loading amount was 1.54 g / in. 3 And the PGM load is 10g / ft 3 Pt and 25g / ft 3 A bottom coat made of Pd was obtained. Next, the top coat front section slurry was applied from one end to half the length of the substrate and dried at 150°C for 1 hour, and then the top coat rear section slurry was applied to the remaining half of the substrate length and dried at 150°C for 1 hour. The resulting product was baked at 500°C for 2 hours. The wash coat loading amount was 2.47 g / in. 3 The PGM load in the forward area is 55g / ft 3 Pd and 14g / ft 3 It consists of Rh, and the PGM load capacity in the rear area is 20g / ft 3 Pt, 55g / ft 3 Pd and 14g / ft 3 A top coat consisting of Rh was obtained.

[0130] Example 6 Preparation of a layered two-metal catalyst article (Reference example, BMC-3, Pd / Pt / Rh 32.5 / 0 / 10, g / ft)3 ) A catalyst article was prepared containing a bottom coat with palladium (Pd) as the sole PGM and a top coat with a combination of palladium (Pd) and rhodium (Rh) as PGMs in both the forward and backward regions. A schematic diagram of this catalyst article is shown in Figure 4A.

[0131] Bottom coat slurry: 18.91 grams of 20% Pd-nitrate aqueous solution was used to impregnate 283 grams of alumina and 700 grams of ceria-zirconia (50% zirconia) via initial wetting impregnation. This product was mixed with water and then D into particles less than 18 μm. 90 It was ground to this extent. After adding nitric acid to adjust the pH to approximately 3.0-4.0, 13 grams of alumina binder was added.

[0132] Topcoat forward area slurry: The first component was prepared by impregnating 490 grams of alumina and 410 grams of ceria-zirconia (50% zirconia) with 75.65 grams of a 20% Pd-nitrate aqueous solution via initial wetting impregnation. Following this process, the PGM was fixed to the support by drying at 150°C for 1 hour, followed by calcination at 500°C for 2 hours. The product was mixed with water and then D into particles less than 18 μm. 90 It was pulverized to that extent.

[0133] The second component was prepared by impregnating 250 grams of zirconia and 410 grams of ceria-zirconia (50% zirconia) with 37.83 grams of a 10% Rh-nitrate aqueous solution via initial wetting impregnation. This product was mixed with water and D 90 The material was ground down to a size of 18 μm or less.

[0134] Two components in slurry form were blended. After adjusting the pH to approximately 7.0-9.0 by adding barium hydroxide and nitric acid, 20 grams of alumina binder were added.

[0135] Topcoat rear area slurry: The first component was prepared by impregnating 9.46 grams of a 20% Pd-nitrate aqueous solution via incipient wetness impregnation into 490 grams of alumina and 410 grams of ceria-zirconia (50% zirconia). Following this step, drying was carried out at 150 °C for 1 hour, and then calcination was performed at 500 °C for 2 hours to fix the PGM on the support. The product was mixed with water and then milled to a D 90 less than 18 μm.

[0136] The second component was prepared by impregnating 37.83 grams of a 10% Rh-nitrate aqueous solution via incipient wetness impregnation into 250 grams of zirconia and 410 grams of ceria-zirconia (50% zirconia). The product was mixed with water and milled so that the D 90 was 18 μm or less. The two components in the form of slurries were blended. Barium hydroxide and nitric acid were added to adjust the pH to approximately 7.0 - 9.0, and then 20 grams of an alumina binder was added.

[0137] This bottom coat slurry was coated on a 750 / 2 (cpsi / mil) through-flow ceramic substrate with a diameter of 118.4 mm and a length of 90 mm, dried at 150 °C for 1 hour, and then calcined at 500 °C for 2 hours. The washcoat loading was 1.53 g / in 3 and a bottom coat consisting of 10 g / ft 3 of Pd was obtained. Next, the top coat front region slurry was applied from one end to half of the substrate length and dried at 150 °C for 1 hour, and then subsequently the top coat rear region slurry was applied to the remaining half of the substrate length and dried at 150 °C for 1 hour. The resulting product was calcined at 500 °C for 2 hours. The washcoat loading was 2.45 g / in 3 and the top coat consisted of 40 g / ft 3 of Pd and 10 g / ft 3 of Rh in the front region, and 5 g / ft 3 of Pd and 10 g / ft 3 of Rh in the rear region. 3 3 3 3 A top coat was obtained.

[0138] Example 7 Preparation of a layered three-metal catalyst article (Example of the present invention, TMC-4, Pd / Pt / Rh 22.5 / 10 / 10, g / ft 3 ) A catalyst article according to the present invention was prepared, comprising a bottom coat having palladium (Pd) and platinum (Pt) as PGMs, and a top coat having palladium (Pd) and rhodium (Rh) as PGMs in the forward region, and palladium (Pd), platinum (Pt), and rhodium (Rh) as PGMs in the backward region. A schematic diagram of this catalyst article is shown in Figure 4B.

[0139] Bottom coat slurry: The first component was prepared by first impregnating 283 grams of ceria-alumina (90% alumina) with 11.82 grams of an aqueous solution of 16% hexahydroxyplaty diethanolamine salt via initial wetting impregnation, and then impregnating with 1.87 grams of an aqueous solution of 20% Pd-nitrate. Following this process, the PGM was fixed to the support by drying at 150°C for 1 hour, followed by calcination at 500°C for 2 hours. The product was mixed with water and then D less than 18 μm 90 It was pulverized to that extent.

[0140] The second component was prepared by impregnating 700 grams of ceria-zirconia (50% zirconia) with 7.59 grams of a 20% Pd-nitrate aqueous solution via initial wetting impregnation. This product was mixed with water and D 90 The material was ground down to a size of 18 μm or less. Two components in slurry form were blended. Nitric acid was added to adjust the pH to approximately 3.0-4.0, and then 13 grams of alumina binder were added.

[0141] Topcoat forward area slurry: The first component was prepared by impregnating 62.40 grams of a 20% Pd-nitrate aqueous solution via incipient wetness impregnation into 490 grams of alumina and 410 grams of ceria-zirconia (50% zirconia). Following this step, drying was carried out at 150 °C for 1 hour, and then calcination was performed at 500 °C for 2 hours to fix the PGM on the support. This product was mixed with water and then milled to D 90 down to less than 18 μm.

[0142] The second component was prepared by impregnating 37.83 grams of a 10% Rh-nitrate aqueous solution via incipient wetness impregnation into 250 grams of alumina and 410 grams of ceria-zirconia (50% zirconia). This product was mixed with water and milled so that D 90 was 18 μm or less.

[0143] The two components in the form of slurries were blended. Barium hydroxide and nitric acid were added to adjust the pH to approximately 7.0 - 9.0, and then 20 grams of an alumina binder was added.

[0144] Top coat rear area slurry: The first component was prepared by impregnating 3.78 grams of a 20% Pd-nitrate aqueous solution via incipient wetness impregnation into 490 grams of alumina and 410 grams of ceria-zirconia (50% zirconia). Following this step, drying was carried out at 150 °C for 1 hour, and then calcination was performed at 500 °C for 2 hours to fix the PGM on the support. This product was mixed with water and then milled to D 90 down to less than 18 μm.

[0145] The second component was prepared by impregnating 16.01 grams of a 10% Rh-nitrate aqueous solution via incipient wetness impregnation into 250 grams of zirconia. This product was mixed with water and milled so that D 90 was 18 μm or less.

[0146] The third component was prepared via initial wetting impregnation, first by impregnating 410 grams of ceria-zirconia (50% zirconia) with 21.82 grams of a 10% Rh-nitrate aqueous solution, and then by impregnating with 23.64 grams of a 16% hexahydroxyplaty diethanolamine salt aqueous solution. Following this process, the PGM was fixed to the support by drying at 150°C for 1 hour, followed by calcination at 500°C for 2 hours. The product was mixed with water and then D into a material less than 18 μm thick. 90 It was pulverized to that extent.

[0147] Three components in slurry form were blended. After adjusting the pH to approximately 7.0-9.0 by adding barium hydroxide and nitric acid, 20 grams of alumina binder were added.

[0148] This bottom coat slurry was applied to a 750 / 2 (cpsi / mill) flow-through ceramic substrate with a diameter of 118.4 mm and a length of 90 mm, dried at 150°C for 1 hour, and then baked at 500°C for 2 hours. The wash coat loading amount was 1.53 g / in. 3 And the PGM load capacity is 5g / ft 3 Pt and 5g / ft 3 A bottom coat made of Pd was obtained. Next, the top coat front section slurry was applied from one end to half the length of the substrate and dried at 150°C for 1 hour, and then the top coat rear section slurry was applied to the remaining half of the substrate length and dried at 150°C for 1 hour. The obtained product was baked at 500°C for 2 hours. The wash coat loading amount was 2.45 g / in. 3 The PGM load in the forward area is 33g / ft 3 Pd and 10g / ft 3 It consists of Rh, and the PGM load capacity in the rear area is 10g / ft 3 Pt, 2g / ft 3 Pd and 10g / ft 3 A top coat consisting of Rh was obtained.

[0149] Example 8 Preparation of layered three-metal catalyst article (Comparative example, TMC-5, Pd / Pt / Rh 50 / 50 / 14, g / ft3 ) A catalyst article having the regional configuration of the present invention, comprising a bottom coat having palladium (Pd) and platinum (Pt) as PGMs, and a top coat having palladium (Pd) and rhodium (Rh) as PGMs in the forward region and palladium (Pd), platinum (Pt), and rhodium (Rh) as PGMs in the backward region, was prepared, but with a lower Pd / Pt ratio. A schematic diagram of this catalyst article is shown in Figure 5.

[0150] Bottom coat slurry: The first component was prepared by first impregnating 283 grams of ceria-alumina (90% alumina) with 58.55 grams of an aqueous solution of 16% hexahydroxyplaty diethanolamine salt via initial wetting impregnation, and then impregnating with 9.38 grams of an aqueous solution of 20% Pd-nitrate. Following this process, the PGM was fixed to the support by drying at 150°C for 1 hour, followed by calcination at 500°C for 2 hours. The product was mixed with water and then D into a material less than 18 μm thick. 90 It was pulverized to that extent.

[0151] The second component was prepared by impregnating 700 grams of ceria-zirconia (50% zirconia) with 37.47 grams of a 20% Pd-nitrate aqueous solution via initial wetting impregnation. This product was mixed with water and D 90 The material was ground down to a size of 18 μm or less. Two components in slurry form were blended. Nitric acid was added to adjust the pH to approximately 3.0-4.0, and then 13 grams of alumina binder were added.

[0152] Topcoat forward area slurry: The first component was prepared by impregnating 490 grams of alumina and 410 grams of ceria-zirconia (50% zirconia) with 46.85 grams of a 20% Pd-nitrate aqueous solution via initial wetting impregnation. Following this process, the PGM was fixed to the support by drying at 150°C for 1 hour, followed by calcination at 500°C for 2 hours. The product was mixed with water and then D into particles less than 18 μm. 90It was pulverized to that extent.

[0153] The second component was prepared by impregnating 250 grams of alumina and 410 grams of ceria-zirconia (50% zirconia) with 52.46 grams of a 10% Rh-nitrate aqueous solution via initial wetting impregnation. This product was mixed with water and D 90 The material was ground down to a size of 18 μm or less.

[0154] Two components in slurry form were blended. After adjusting the pH to approximately 7.0-9.0 by adding barium hydroxide and nitric acid, 20 grams of alumina binder were added.

[0155] Topcoat rear area slurry: The first component was prepared by impregnating 490 grams of alumina and 410 grams of ceria-zirconia (50% zirconia) with 46.85 grams of a 20% Pd-nitrate aqueous solution via initial wetting impregnation. Following this process, the PGM was fixed to the support by drying at 150°C for 1 hour, followed by calcination at 500°C for 2 hours. The product was mixed with water and then D into particles less than 18 μm. 90 It was pulverized to that extent.

[0156] The second component was prepared by impregnating 250 grams of alumina with 22.24 grams of a 10% Rh-nitrate aqueous solution via initial wetting impregnation. This product was mixed with water and D 90 The material was ground down to a size of 18 μm or less.

[0157] The third component was prepared by first impregnating 410 grams of ceria-zirconia (50% zirconia) with 30.22 grams of an aqueous 10% Rh-nitrate solution via initial wetting impregnation, and then impregnating with 117.12 grams of an aqueous 16% hexahydroxyplaty diethanolamine salt solution. Following this process, the PGM was fixed to the support by drying at 150°C for 1 hour, followed by calcination at 500°C for 2 hours. The product was mixed with water and then D into a material less than 18 μm thick. 90 It was pulverized to that extent.

[0158] Three components in slurry form were blended. After adjusting the pH to approximately 7.0-9.0 by adding barium hydroxide and nitric acid, 20 grams of alumina binder were added.

[0159] This bottom coat slurry was applied to a 750 / 2 (cpsi / mil) flow-through ceramic substrate with a diameter of 101.6 mm and a length of 118 mm, dried at 150°C for 1 hour, and then baked at 500°C for 2 hours. The wash coat loading amount was 1.55 g / in. 3 And the PGM load capacity is 25g / ft 3 Pt and 25g / ft 3 A bottom coat made of Pd was obtained. Next, the top coat front section slurry was applied from one end to half the length of the substrate and dried at 150°C for 1 hour, and then the top coat rear section slurry was applied to the remaining half of the substrate length and dried at 150°C for 1 hour. The resulting product was baked at 500°C for 2 hours. The wash coat loading amount was 2.46 g / in. 3 The PGM load in the forward area is 25g / ft 3 Pd and 14g / ft 3 It consists of Rh, and the PGM load capacity in the rear area is 50g / ft 3 Pt, 25g / ft 3 Pd and 14g / ft 3 A top coat consisting of Rh was obtained.

[0160] Example 9: Catalyst Performance Test The catalyst samples summarized in Table 1 were subjected to thermal aging in a GM8.1L V8 engine at an inlet temperature of 875°C.

[0161] [Table 1]

[0162] Aged samples were tested on a Daimler 2.0L engine bench using the Worldwide Unified Test Cycle (WLTC) in accordance with China-6 "Type I" (GB18352.6-2016). The performance of the test samples was evaluated by measuring tailpipe total hydrocarbon (THC), CO, and NOx emissions in the following four phases included in one test cycle in accordance with China-6 "Type I".

[0163] P1: Low-speed phase from 0 seconds to 589 seconds. P2: Medium speed phase from 590 seconds to 1022 seconds. P3: High-speed phase from 1023 seconds to 1477 seconds, and P4: An ultra-fast phase from 1478 seconds to 1800 seconds.

[0164] Each sample was tested three times, and the average of the test results is summarized in Tables 2 to 4.

[0165] [Table 2]

[0166] [Table 3]

[0167] [Table 4]

[0168] It should be understood that the composition of engine exhaust gases can vary depending on the engine's condition, such as the time and distance the engine has been running. The samples in the same group shown in the table above were tested under substantially the same engine conditions to ensure that the inlet exhaust gases of the test samples had substantially the same composition, and to allow for comparisons between samples with respect to the measured emissions.

[0169] As can be seen from the measured emissions, Sample 2 (reference example) showed 25% higher THC, 6% higher CO, and 30% higher NOx compared to Sample 1 (reference example). Comparison of the test results of Sample 1 and Sample 2 confirmed that incorporating Pt by simply replacing some of the Pd in ​​the TWC catalyst worsens THC, CO, and NOx emissions, as is generally recognized in the art.

[0170] Similarly, Sample 4 (reference example), which is a variation of Sample 3 obtained by replacing 20% ​​of the total Pd load with Pt and placing Pt in the bottom coat, shows that it has 9% higher THC and 13% higher CO compared to Sample 3 (reference example).

[0171] Contrary to the trend that replacing Pd with Pt worsens emissions, sample 6, having the catalyst composition and configuration according to the present invention, shows a 4% reduction in THC, a 24% reduction in CO, and a 15% reduction in NOx compared to sample 5 (reference example). Similarly, sample 8, having the catalyst composition and configuration according to the present invention, showed a 2% lower THC, a 5% lower CO, and a 5% lower NOx compared to sample 7 (reference example).

[0172] A comparison of the test results of Sample 10 (Comparative Example) and Sample 9 (Reference Example) shows that the positive effect achieved by incorporating Pt in the TWC catalyst having the regionalized configuration according to the present invention disappears when 50% of the total Pd load is replaced with Pt. Sample 10, which has the configuration according to the present invention but has a composition outside the scope of the present invention, showed 17% higher THC, 7% higher CO, and 25% higher NOx compared to Sample 9 (Reference Example).

[0173] While this specification has described the present invention with reference to specific embodiments, it should be understood that these embodiments are merely illustrative of the principles and applications of the present invention. It will be apparent to those skilled in the art that various modifications and variations can be made to the methods and apparatus of the present invention without departing from the spirit and scope of the invention. Thus, the present invention is intended to include modifications and variations that fall within the scope of the appended claims and their equivalents.

Claims

1. A layered catalyst article, a) A top layer comprising a front region and a rear region, wherein the front region comprises palladium and rhodium components supported individually or together on a support, and the rear region comprises platinum, rhodium, and palladium components supported individually or together on a support, b) A bottom layer comprising platinum and palladium components supported individually or together on a support, c) base material; Includes, The palladium component and the platinum component are present in a Pd / Pt mass ratio in the range of 20:1 to 5:4 when calculated as palladium and platinum elements, and The palladium and rhodium components are loaded into the front region of the top layer in a Pd / Rh mass ratio in the range of 50:1 to 1:1, calculated as separate elements. The platinum component and the rhodium component are loaded into the rear section of the top layer in a Pt / Rh mass ratio in the range of 10:1 to 1:5, calculated as separate elements. The front portion of the top layer comprises 20-70% of the substrate length, and the rear portion of the top layer comprises 30-80% of the substrate length. The mass ratio of the rhodium component to the total mass of the palladium component and platinum component in the layered catalyst article is in the range of 2:3 to 1:200 when calculated for each element. A layered catalyst article wherein the mass ratio of the palladium component to the platinum component to the rhodium component in the layered catalyst article is in the range of 10:1:0.2 to 2:1:1 when calculated for each element.

2. The layered catalyst article according to claim 1, wherein the rear region comprises platinum, rhodium, and palladium components supported individually or together on a support.

3. The layered catalyst article according to claim 1 or 2, wherein the front portion of the top layer comprises 30 to 60% of the substrate length and the rear portion of the top layer comprises 40 to 70% of the substrate length, or the front portion of the top layer comprises 30 to 50% of the substrate length and the rear portion of the top layer comprises 50 to 70% of the substrate length.

4. The layered catalyst article according to any one of claims 1 to 3, wherein the mass ratio of the palladium component to the platinum component contained in the layered catalyst article is in the range of 4:1 to 5:4 when calculated as palladium element and platinum element.

5. The layered catalyst article according to any one of claims 1 to 4, wherein the mass ratio of the rhodium component to the total mass of the palladium component and the platinum component in the layered catalyst article is in the range of 1:2 to 1:50, 1:3 to 1:20, or 1:3 to 1:10 when calculated for each element.

6. The layered catalyst article according to any one of claims 1 to 5, wherein the mass ratio of the palladium component to the platinum component to the rhodium component in the layered catalyst article is 5:1:0.5 to 2:1:1 when calculated as individual elements.

7. The layered catalyst article according to any one of claims 1 to 6, wherein the palladium component and the rhodium component are loaded into the front region of the top layer in a Pd / Rh mass ratio of 10:1 to 1.5:1, or 5:1 to 1.5:1, or 4:1 to 2:1, calculated as individual elements.

8. The layered catalyst article according to any one of claims 1 to 7, wherein the platinum component and the rhodium component are loaded into the rear region of the top layer in a Pt / Rh mass ratio of 2:1 to 1:2 or 1.5:1 to 1:1.5 when calculated as individual elements.

9. The layered catalyst article according to any one of claims 1 to 8, wherein the support for each of the platinum, palladium, and rhodium components is independently selected from refractory metal oxides, oxygen storage components, and any combination thereof.

10. a) A top layer comprising a front region and a rear region, wherein the front region comprises palladium and rhodium components supported individually or together on a support, and the rear region comprises platinum, palladium, and rhodium components supported individually or together on a support, b) A bottom layer comprising platinum and palladium components supported individually or together on a support, c) base material; Includes, In each case, the support is independently a refractory metal oxide selected from alumina, lantana-doped alumina, lantana-zirconia-doped alumina, ceria-doped alumina, zirconia, zirconia-doped alumina, ceria-zirconia-doped alumina, lantana-doped zirconia, and lantana-yttria-doped zirconia, an oxygen storage component selected from ceria-zirconia composite oxides and rare-earth stabilized ceria-zirconia composite oxides, or any combination thereof. A layered catalyst article according to any one of claims 1 to 9.

11. a) A top layer comprising a front region and a rear region, wherein the front region comprises a palladium component individually supported by a combination of alumina and an oxygen storage component, and a rhodium component individually supported by a combination of alumina or zirconia and an oxygen storage component, and the rear region comprises a palladium component individually supported by a combination of alumina and an oxygen storage component, a platinum component supported by an oxygen storage component, and a rhodium component, wherein a portion of the rhodium component is supported by the oxygen storage component together with the platinum component, and the remaining portion of the rhodium component is supported by alumina or zirconia, wherein the oxygen storage component in each case is independently selected from ceria-zirconia composite oxide and rare-earth stabilized ceria-zirconia composite oxide, b) A bottom layer comprising a platinum component and a palladium component, wherein the platinum component, together with a portion of the palladium component, is supported by ceria-doped alumina, and the remaining portion of the palladium component is supported by an oxygen storage component selected from ceria-zirconia composite oxide and rare-earth stabilized ceria-zirconia composite oxide, and c) Base material A layered catalyst article according to any one of claims 1 to 10, comprising:

12. The layered catalyst article according to any one of claims 1 to 11, wherein the forward region of the top layer substantially does not contain a platinum component, or substantially does not contain any PGM other than Pd and Rh.

13. The layered catalyst article according to any one of claims 1 to 12, wherein the rear region of the top layer substantially does not contain any PGM other than Pd, Pt, and Rh.

14. The layered catalyst article according to any one of claims 1 to 13, wherein the bottom layer substantially does not contain rhodium components, or substantially does not contain any PGM other than Pt and Pd.

15. The layered catalyst article according to any one of claims 1 to 14, wherein the palladium component supported by the oxygen storage component in the bottom layer comprises 50% to 95% or 70% to 95% of the total amount of the palladium component in the bottom layer.

16. The layered catalyst article according to any one of claims 1 to 15, wherein the rhodium component supported by the oxygen storage component in the rear region of the top layer comprises 50% to 90% or 60% to 80% of the total amount of the rhodium component in the rear region.

17. The layered catalyst article according to any one of claims 1 to 16, wherein the platinum component in the rear region of the top layer comprises 30% to 70%, 40% to 60%, or 50% of the total amount of platinum component in the layered catalyst article.

18. The layered catalyst article according to any one of claims 1 to 17, wherein the bottom layer is applied on the substrate and the top layer is applied on the bottom layer without any intermediate layer.

19. The layered catalyst article according to any one of claims 1 to 18, wherein the substrate is a flow-through substrate.

20. The following steps, - A process of depositing a bottom coat slurry onto a substrate to obtain a bottom layer, - A step of depositing a topcoat front region slurry from one end of the substrate onto the bottom layer of a certain length to obtain the front region of the top layer, - A step of depositing a topcoat rear region slurry on the bottom layer over the remaining length of the substrate to obtain the rear region of the top layer. A method for producing a layered catalyst article according to any one of claims 1 to 19, including the method described above.

21. A method for using the layered catalyst article according to any one of claims 1 to 19 for reducing hydrocarbons, carbon monoxide, and nitrogen oxides in the exhaust flow.

22. An exhaust treatment system comprising a layered catalyst article according to any one of claims 1 to 19, located downstream of a gasoline engine.

23. The exhaust treatment system according to claim 22, wherein the layered catalyst article is located in close proximity downstream of the gasoline engine, under the floor, or both.

24. The exhaust gas treatment system according to claim 22 or 23, wherein a four-way catalytic converter directly or indirectly follows the layered catalytic article.

25. A method for treating an exhaust flow, comprising bringing the exhaust flow into contact with a layered catalyst article according to any one of claims 1 to 19 or an exhaust treatment system according to any one of claims 22 to 24.

26. The method according to claim 25, wherein the layered catalyst article is particularly useful for reducing hydrocarbons, carbon monoxide, and nitrogen oxides in the exhaust flow from a gasoline engine.

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