Ternary Conversion Catalyst Article

Abstract

The claimed invention is a catalyst article comprising: a first layer comprising at least one first platinum group metal supported on a first support, the first support comprising alumina and a first oxygen storage component, the first oxygen storage component comprising ceria-zirconia; a second layer comprising at least one second platinum group metal supported on a second support, the second support comprising alumina and a second oxygen storage component, the second oxygen storage component comprising ceria-zirconia; and a substrate. the total amount of alumina, calculated as Al2O3, from the first and second layers is 1.4 grams per cubic inch of substrate or greater, the total amount of ceria, calculated as CeO2, from the first and second layers is 0.6 grams per cubic inch of substrate or greater, the weight ratio of ceria present in the first layer to ceria present in the second layer is greater than 1.7:1, and the total amount of the first or second platinum group metal is in the range of 0.001 to 0.2 grams per cubic inch of substrate. The present invention also provides a process for preparing the catalyst article.

Description

[Technical Field]

[0001] The claimed invention relates to a catalyst article useful for treating exhaust gas and reducing pollutants contained therein. Specifically, the claimed invention relates to a layered platinum group metal-based ternary conversion catalyst article having improved thermal stability. [Background technology]

[0002] Generally, a vehicle's fuel efficiency is improved by minimizing fuel enrichment under high-load conditions. However, low fuel enrichment typically leads to increased exhaust temperatures, which in turn creates greater thermal stress on the components of the exhaust system. This problem is more serious in larger vehicles than in smaller ones.

[0003] Three-way converter (TWC) catalysts (hereinafter referred to as three-way converter catalysts, three-way catalysts, TWC catalysts, and TWC-compatible catalysts) have been used for several years to treat exhaust gas flows from internal combustion engines. Generally, catalytic converters containing three-way converter catalysts are used in the exhaust gas lines of internal combustion engines to treat or purify exhaust gases containing pollutants such as hydrocarbons, nitrogen oxides, and carbon monoxide. Three-way converter catalysts are typically known to oxidize unburned hydrocarbons and carbon monoxide and reduce nitrogen oxides.

[0004] While various TWC catalysts are known, it remains important to develop catalyst technologies with increased thermal endurance that can provide excellent TWC functionality even after severe aging. [Overview of the project]

[0005] The claimed invention is, a) A first layer comprising at least one first platinum group metal supported on a first carrier, The first carrier comprises alumina and a first oxygen storage component. The first oxygen storage component is a first layer containing ceria-zirconia, b) A second layer comprising at least one second platinum group metal supported on a second carrier, The second carrier comprises alumina and a second oxygen storage component. The second oxygen storage component is a second layer containing ceria-zirconia, c) A catalyst article comprising a base material, The total amount of alumina calculated as Al2O3 from the first and second layers is 1.4 grams or more per cubic inch of the substrate. The total amount of ceria calculated as CeO2 from the first and second layers is 0.6 grams or more per cubic inch of the substrate. The weight ratio of ceria in the first layer to ceria in the second layer, calculated using CeO2, is greater than 1.7:1. The present invention provides a catalyst article in which the total amount of the first or second platinum group metal is in the range of 0.001 to 0.2 grams per cubic inch of the substrate.

[0006] The claimed invention also provides a process for preparing the catalyst article of the present invention. The claimed invention further provides an exhaust system for an internal combustion engine comprising the catalyst article of the present invention, and a method for treating a gaseous exhaust flow comprising hydrocarbons, carbon monoxide, and nitrogen oxides, comprising contacting the exhaust flow with the catalyst article or exhaust system according to the present invention. [Brief explanation of the drawing]

[0007] To provide an understanding of embodiments of the present invention, the accompanying drawings are referenced, which are not necessarily to scale, and the reference numerals indicate components of exemplary embodiments of the present invention. The drawings are for illustrative purposes only and should not be construed as limiting the present invention. The above and other features, their nature, and various advantages of the claimed present invention will become more apparent by considering the modes for carrying out the invention below in conjunction with the accompanying drawings.

[0008] [Figure 1]The results of comparative tests of cumulative NMHC, NOx, and CO emissions for catalyst D and the reference catalyst of the present invention are shown. [Figure 2] This shows the comparative oxygen storage capacity of catalyst D and the reference catalyst of the present invention. [Figure 3A] This is a perspective view of a honeycomb-type substrate support that may contain a catalyst composition according to one claimed embodiment of the present invention. [Figure 3B] This is an enlarged view compared to Figure 3A, showing a partial cross-sectional view taken along a plane parallel to the end face of the substrate carrier in Figure 3A, and illustrating an enlarged view of the multiple gas channels shown in Figure 3A. [Figure 4] Figure 3A shows a broken cross-section of an enlarged view of the honeycomb substrate, representing the wall flow filter substrate monolith. [Modes for carrying out the invention]

[0009] The claimed invention is described more fully below. The claimed invention may be embodied in many different forms and should not be construed as being limited to the embodiments described herein, but rather these embodiments are provided so as to fully convey the scope of the claimed invention to those skilled in the art, making it thorough and complete. Nothing in this specification should be construed as indicating that any unclaimed element is essential to the practice of the disclosed materials and methods.

[0010] All methods described herein may be performed in any preferred order, unless otherwise indicated herein or unless clearly contradicted by the context. The use of any and all examples or illustrative language provided herein (e.g., "etc.") is intended solely to better describe the materials and methods and is not intended to limit their scope unless otherwise claimed.

[0011] Definition: The use of the terms "a", "an", "the", and similar referents in the context describing the materials and methods discussed herein (particularly in the context of the claims set forth below) should be construed to cover both the singular and the plural, unless otherwise indicated herein or otherwise clearly contradicted by context.

[0012] The term "about" as used throughout this specification is employed to describe and account for small variations. For example, the term "about" refers to ±5% or less, such as ±2% or less, ±1% or less, ±0.5% or less, ±0.2% or less, ±0.1% or less, or ±0.05% or less. All numerical values, whether explicitly stated or not, are modified by the term "about". It goes without saying that the value modified by the term "about" includes the specific value. For example, "about 5.0" should include 5.0.

[0013] In the context of the present invention, the term "first layer" is used interchangeably with "lower layer" or "bottom coat", while the term "second layer" is used interchangeably with "upper layer" or "top coat". The first layer is deposited on at least a portion of a substrate, and the second layer is deposited on at least a portion of the first layer.

[0014] The terms "catalyst", "catalytic article", or "catalyst article" refer to a component in which a substrate is coated with a catalyst composition used to promote a desired reaction. The catalyst article may be a layered catalyst article. The term layered catalyst article refers to a catalyst article in which a substrate is coated in layers with catalyst compositions. These catalyst compositions may be referred to as washcoats. Preferably, the catalyst composition comprises at least one PGM as a catalytically active metal. Platinum group metals, also referred to as "PGM", are ruthenium, rhodium, palladium, osmium, iridium, and platinum.

[0015] The term "ternary conversion catalyst" refers to a catalyst that simultaneously promotes: a) the reduction of nitrogen oxides to nitrogen and oxygen, b) the oxidation of carbon monoxide to carbon dioxide, and c) the oxidation of unburned hydrocarbons to carbon dioxide and water.

[0016] The term "NOx" refers to nitrogen oxide compounds such as NO or NO2.

[0017] "Supporting material" refers to a material on which metals (e.g., PGMs), stabilizers, accelerators, binders, etc., are fixed by precipitation, association, dispersion, impregnation, or other suitable methods.

[0018] The terms "deposited" and "supported" are used interchangeably. The deposition of catalytically active metals onto a support can be achieved by various methods known to those skilled in the art. These include coating techniques, impregnation techniques such as initial wetting, precipitation techniques, and atomic deposition techniques such as chemical porous deposition. In these techniques, a suitable precursor containing the catalytically active metal is brought into contact with the support, thereby undergoing chemical or physical bonding with the support. In this way, the precursor containing the catalytically active metal is deposited on the support. Through interaction with the support, the precursor containing the catalytically active metal may be converted into another species containing the catalytically active metal. Different treatment steps, such as chemical fixation and / or thermal fixation, can be performed to increase the chemical or physical bonding between the deposited species and the support.

[0019] The term "thermal fixation" refers to depositing catalytically active metals onto each support, for example, via an initial wet impregnation method, followed by calcining the resulting catalytically active metal / support mixture. In one embodiment, the mixture is calcined at 400-700°C for 1.0-3.0 hours at a gradient rate of 1-25°C / min.

[0020] The term "chemical fixation" refers to the process of depositing catalytically active metals onto each support material, followed by fixation using additional reagents such as barium hydroxide, thereby chemically converting the precursor containing the catalytically active metal. As a result, the catalytically active metal is chemically fixed as an insoluble component within the pores and on the surface of the support material.

[0021] The term "initial wet impregnation," also known as capillary impregnation or dry impregnation, refers to the process of dissolving a catalyst-active metal precursor in an aqueous or organic solution and adding the resulting catalyst-active metal-containing solution to a support. The solution is drawn into the pores of the support by capillary action. The resulting composition is then dried and calcined to remove volatile components from the solution and deposit the metal on the surface of the support.

[0022] As used herein, the term “substrate” refers to the material on which the catalyst material is typically placed in the form of a washcoat. The substrate is sufficiently porous to allow the passage of the gas stream to be processed.

[0023] The terms "monolithic substrate" or "honeycomb substrate" refer to a single, uniform, and continuous structure from inlet to outlet.

[0024] As used herein, the term “washcoat” has the common meaning in the art of a thin, adhesive coating of a catalyst or other material applied to a substrate (such as a honeycomb substrate). The washcoat is formed by preparing a slurry containing particles of a specific solid content (e.g., 15–60% by weight) in a liquid vehicle, which is then coated onto the substrate and dried to provide a washcoat layer.

[0025] As used herein, “refractory metal oxide material” refers to a metal-containing oxide that exhibits chemical and physical stability at high temperatures, such as those associated with gasoline and diesel engine exhaust.

[0026] "BET surface area" has its usual meaning, referring to the Brunauer, Emmett, and Teller method for determining surface area by N2 adsorption.

[0027] The term "oxygen storage component" (OSC) refers to an entity that has a polyvalent state and can actively react with reducing agents such as carbon monoxide (CO) and / or hydrogen under reducing conditions, and then react with oxidizing agents such as oxygen or nitrogen oxides under oxidizing conditions.

[0028] In the current context, OSC refers to ceria-zirconia. In a preferred embodiment, OSC refers to ceria-zirconia that is essentially stabilized by at least one rare earth element, which may exist in oxide form, such as lanthanum, yttrium, neodymium, and praseodymium.

[0029] The term "ceria-zirconia composite" refers to a mixture of ceria and zirconia that is not inherently stabilized by any rare earth element.

[0030] As used herein, the term “flow” broadly refers to any combination of flowing gases that may contain solid or liquid particulate matter.

[0031] As used herein, the terms “upstream” and “downstream” refer to the relative directions corresponding to the flow of engine exhaust gases from the engine to the tailpipe, with the engine located upstream and the tailpipe and any contaminant mitigation items, such as filters and catalysts, located downstream of the engine.

[0032] The claimed object of the present invention is to develop a catalyst technology with increased thermal durability that can provide excellent TWC functionality even after severe high-temperature aging.

[0033] The technical challenge of achieving high thermal stability is solved by the synergistic effect between the amount of alumina, the amount of ceria, and the specific distribution of ceria in the two layers. It is found that the specific amount and distribution of ceria maintain OSC function even after harsh high-temperature aging, and the specific alumina load provides a support for the PGM, maintaining the structural stability of the wash coat. Overall, the higher thermal stability helps maintain PGM activity even after harsh high-temperature aging, thereby improving the conversion of HC, CO, and NOx.

[0034] Therefore, the claimed invention is, a) A first layer comprising at least one first platinum group metal supported on a first carrier, The first carrier comprises alumina and a first oxygen storage component. The first oxygen storage component is a first layer containing ceria-zirconia, b) A second layer comprising at least one second platinum group metal supported on a second carrier, The second carrier comprises alumina and a second oxygen storage component. The second oxygen storage component is a second layer containing ceria-zirconia, c) A catalyst article comprising a base material, The total amount of alumina calculated as Al2O3 from the first and second layers is 1.4 grams or more per cubic inch of the substrate. The total amount of ceria calculated as CeO2 from the first and second layers is 0.6 grams or more per cubic inch of the substrate. The weight ratio of ceria present in the first layer to ceria present in the second layer is greater than 1.7:1. The present invention provides a catalyst article in which the total amount of the first or second platinum group metal is in the range of 0.001 to 0.2 grams per cubic inch of the substrate.

[0035] Platinum group metals: Platinum group metals, also known as "PGM," are ruthenium, rhodium, palladium, osmium, iridium, and platinum. The first platinum group metal is preferably selected from palladium, platinum, or rhodium. The second platinum group metal is preferably selected from palladium, platinum, or rhodium. More preferably, the first platinum group metal is palladium and the second platinum group metal is rhodium.

[0036] The amount of the first platinum group metal or the amount of the second platinum group metal is in the range of 0.001 to 0.2 grams per cubic inch of the substrate. Preferably, the amount of the first platinum group metal is in the range of 0.029 to 0.174 grams per cubic inch (50 to 300 grams per cubic foot) of the substrate. Preferably, the amount of the second platinum group metal is in the range of 0.001 to 0.017 grams per cubic inch (2.0 to 30 grams per cubic foot) of the substrate.

[0037] Carrier: A. Alumina (refractory metal oxide component): Generally, refractory metal oxides include alumina, silica, zirconia, titania, ceria, and physical or chemical mixtures thereof, including atomically doped combinations. The refractory metal oxide component may be a high-surface-area refractory metal oxide carrier, specifically referring to carrier particles having pores larger than 20 Å and a broad pore distribution.

[0038] In this invention, the refractory metal oxide component used is alumina. The term "alumina" refers to stabilized or unstabilized aluminum oxide. Stabilized and unstabilized aluminum oxides may exist in different phase modifications.

[0039] Stabilized aluminum oxide is a composite oxide comprising Al2O3 and one or more dopants selected from rare earth metal oxides, alkali metal oxides, alkaline earth metal oxides, silicon dioxide, or any combination thereof. Preferred dopants are lanthanum oxide (La2O3), cerium oxide (CeO2), zirconium oxide (ZrO2), barium oxide (BaO), neodymium oxide (Nd2O3), a combination of lanthanum oxide and zirconium oxide, a combination of barium oxide, lanthanum oxide, and neodymium oxide, or a combination of cerium oxide and zirconium oxide. Dopants can impart different properties to aluminum oxide. Dopants can delay undesirable phase transitions of aluminum oxide, stabilize the surface area, introduce defect sites, and / or alter the acidity of the aluminum oxide surface.

[0040] Exemplary aluminas include large-pore boehmite, gamma-alumina, and delta / theta-alumina. Useful commercially available aluminas include high-bulk-density gamma-alumina, low- or medium-bulk-density large-pore gamma-alumina, and activated aluminas such as low-bulk-density large-pore boehmite and gamma-alumina. Such materials are generally thought to provide durability to the resulting catalyst. High-surface-area alumina carriers, also called "gamma-alumina" or "activated alumina," typically have a surface area of ​​60 square meters ("m") per gram. 2 / g) often exceeding approximately 300m 2 This shows the BET surface area of ​​fresh material up to 1 / g or more. Such activated alumina is usually a mixture of the gamma and delta phases of alumina, but may also contain substantial amounts of eta, kappa, and theta alumina phases.

[0041] The BET surface area of ​​alumina is approximately 100 to 150 m². 2 It could be in the range of / g.

[0042] The total amount of alumina calculated as Al2O3 in the first layer is approximately 20-70% by weight, based on the total weight of the first layer, and the total amount of alumina in the second layer is approximately 20-70% by weight, based on the total weight of the second layer.

[0043] Alumina can be doped with dopants selected from lantana, lantana, ceria, ceria-zirconia, zirconia, lantana-zirconia, barrier, barrier-lantana, barrier-lantana-neodymia, or combinations thereof. The amount of dopant in the alumina ranges from 0.01 to 15% by weight of the total weight of the alumina.

[0044] B. Oxygen storage components: The oxygen storage component includes ceria-zirconia. The term ceria-zirconia refers to a composite or mixed oxide containing CeO2 and ZrO2. In one embodiment, the oxygen storage component is a solid solution containing CeO2 and ZrO2 that can form a single phase as detected by XRD. In addition to CeO2 and ZrO2, ceria-zirconia may contain additional rare earth metal oxides different from CeO2 and ZrO2. The presence of rare earth metal oxides provides stability to the ceria-zirconia mixed metal oxide. In the context of the present invention, exemplary oxygen storage components include ceria-zirconia-lantana, ceria-zirconia-yttria, ceria-zirconia-lantana-yttria, ceria-zirconia-neodymia, ceria-zirconia-praseodymia, ceria-zirconia-lantana-neodymia, ceria-zirconia-lantana-praseodymia, ceria-zirconia-lantana-neodymia-praseodymia, or any combination thereof.

[0045] Preferably, the amount of CeO2 in the oxygen storage component is in the range of 20 to 50% by weight, based on the weight of the oxygen storage component.

[0046] The oxygen storage components present in the first and / or second layers are the same. Preferably, the first oxygen storage component includes ceria-zirconia stabilized with lantana (La2O3). Preferably, the second oxygen storage component includes ceria-zirconia stabilized with lantana (La2O3).

[0047] The total amount of oxygen storage components in the first layer is approximately 30-80% by weight, based on the total weight of the first layer, and the total amount of oxygen storage components in the second layer is approximately 20-70% by weight, based on the total weight of the second layer.

[0048] The amount of ceria in the first oxygen storage component is approximately 20-45% by weight, based on the total weight of the first oxygen storage component. The amount of ceria in the second oxygen storage component is approximately 20-45% by weight, based on the total weight of the second oxygen storage component.

[0049] The amount of ceria calculated as CeO2 in the first layer is approximately 10-50% by weight, while the amount of ceria in the second layer is also approximately 10-50% by weight.

[0050] The amount of oxygen storage components present in the first layer is preferably in the range of 30 to 60% by weight, based on the total weight of the first layer. The amount of oxygen storage components present in the second layer is preferably in the range of 30 to 60% by weight, based on the total weight of the second layer.

[0051] C. ceria-zirconia composite: An exemplary ceria-zirconia composite is a mixture of ceria and zirconia. In one embodiment, the composite is a mixed oxide, where each oxide has its different chemical and physical state, but the oxides can interact through their interfaces. Any physical state or combination of states of CeO2 can be present or coexist on the surface of zirconia or within the bulk. Surface CeO2 modification of zirconia can be in the form of separate parts (particles or clusters) or form a layer of ceria that partially or completely covers the surface of the zirconia.

[0052] In one embodiment, the ceria-zirconia composite contains 50% by weight of ceria based on the total weight of the ceria-zirconia composite. The amount of ceria-zirconia composite in the second layer is about 1.0 to 25% by weight. The ceria-zirconia composite can be added as a binder to the catalyst article of the present invention.

[0053] Base material: The substrate of the catalyst article of the claimed invention may be constructed from any material typically used to prepare automotive catalysts. In one embodiment, the substrate is a ceramic substrate, a metal substrate, a ceramic foam substrate, a polymer foam substrate, or a woven fiber substrate. In one embodiment, the substrate is a ceramic or metal monolithic honeycomb structure.

[0054] The substrate is coated and adhered with a wash coat containing the catalyst composition described herein, thereby providing multiple wall surfaces that act as carriers for the catalyst composition.

[0055] Exemplary metal substrates include heat-resistant metals and metal alloys, such as titanium and stainless steel, and 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 constitute at least 15% by weight of the alloy, for example, 10-25% by weight of chromium, 3-8% by weight of aluminum, and up to 20% by weight of nickel. The alloys may also contain small or trace amounts of one or more metals, such as manganese, copper, vanadium, and titanium. The surface of the metal substrate may be oxidized at a high temperature, for example, above 1000°C, to form an oxide layer on the surface of the substrate, which improves the corrosion resistance of the alloy and facilitates the adhesion of the wash coat layer to the metal surface.

[0056] The ceramic materials used to construct the substrate may 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, aluminosilicate, and the like.

[0057] Any suitable substrate may be used, such as a monolithic flow-through substrate having multiple fine, parallel gas channels extending from the inlet to the outlet surface of the substrate, so that the passage is open to the fluid flow. The passage, which is essentially a straight path from inlet to outlet, is defined by walls on which the catalyst material is coated as a wash coat, so that the gas flowing through the passage comes into contact with the catalyst material. The channels of the monolithic substrate are thin-walled channels, and these thin-walled channels are of any suitable cross-sectional shape, such as trapezoidal, rectangular, square, sinusoidal, hexagonal, elliptical, and circular. Such structures accommodate gas inlet openings with a cross-sectional area of ​​approximately 60 to approximately 1200 or more (i.e., "cells") per square inch (cpsi), more commonly about 300 to 900 cpsi. The wall thickness of the flow-through substrate may vary, with a typical range of 0.002 to 0.1 inches. Typical commercially available flow-through substrates are cordierite substrates having a wall thickness of 6 mils at 400 cpsi or a wall thickness of 4 mils at 600 cpsi. However, it will be understood that the present invention is not limited to a particular substrate type, material, or shape. In an alternative embodiment, the substrate may be a wall-flow substrate, where each passage is closed at one end of the substrate body by a non-porous plug, and alternating passages are closed at the opposite end face. This requires the gas to flow through the porous walls of the wall-flow substrate to reach the outlet. Such monolithic substrates may have a maximum of about 700 cpsi or more, for example, about 100 to 400 cpsi, more typically about 200 to about 300 cpsi. The cross-sectional shape of the cells may vary as described above. Wall-flow substrates typically have a wall thickness of 0.002 to 0.1 inches. Typical commercially available wall flow substrates are constructed from porous cordierite, with examples having wall thicknesses of 200 cpsi and 10 mil or 300 cpsi and 8 mil, and wall porosity of 45-65%. Other ceramic materials such as aluminum titanate, silicon carbide, and silicon nitride are also used as wall flow filter substrates. However, it will be understood that the present invention is not limited to specific substrate types, materials, or shapes.It should be noted that, when the substrate is a wall-flow substrate, the catalyst composition can penetrate into the pore structure of the porous wall in addition to being placed on the wall surface (i.e., partially or completely blocking the pore openings). In one embodiment, the substrate has a flow-through ceramic honeycomb structure, a wall-flow ceramic honeycomb structure, or a metal honeycomb structure.

[0058] Figures 3A and 3B illustrate an exemplary substrate 2 in the form of a flow-through substrate coated with the wash-coat composition described herein. Referring to Figure 3A, the exemplary substrate 2 has a cylindrical shape and has a cylindrical outer surface 4, an upstream end surface 6, and a corresponding downstream end surface 8 identical to end surface 6. The substrate 2 has a plurality of fine, parallel gas channels 10 formed inside. As seen in Figure 3B, the channels 10 are formed by walls 12 and extend through the substrate 2 from the upstream end surface 6 to the downstream end surface 8, and the channels 10 are not obstructed in order to allow a fluid, such as a gas flow, to flow longitudinally through the substrate 2 via the gas channels 10. As is more readily seen in Figure 3B, the walls 12 are dimensioned and constructed such that the gas channels 10 have a substantially regular polygonal shape. As shown, the wash-coat composition can be applied in a plurality of distinct layers as needed. In the illustrated embodiment, the washcoat consists of a separate first washcoat layer 14 adhered to the wall 12 of the substrate member and a separate second washcoat layer 16 coated on the first washcoat layer 14. In one embodiment, the claimed invention can also be carried out with two or more (e.g., three or four) washcoat layers and is not limited to the illustrated two-layer embodiment.

[0059] Figure 4 illustrates an exemplary substrate 2 of a wall flow filter substrate coated with the washcoat composition described herein. As seen in Figure 4, the exemplary substrate 2 has a plurality of passages 52. The passages are tubularly enclosed by the inner wall 53 of the filter substrate. The substrate has an inlet end 54 and an outlet end 56. The alternating passages are blocked by inlet plugs 58 at the inlet end and by outlet plugs 60 at the outlet end, forming a checkerboard pattern that is reversed at the inlet 54 and outlet 56. The gas flow 62 enters through the unblocked channel inlet 64, is stopped by the outlet plugs 60, and diffuses through the (porous) channel wall 53 to the outlet side 66. The gas cannot pass back to the inlet side of the wall due to the inlet plugs 58. The porous wall flow filter used in the present invention is catalyzed because the wall of the element has one or more catalytic materials on it or contains one or more catalytic materials within it. The catalyst material may be present only on the inlet side of the element's wall, only on the outlet side, or on both the inlet and outlet sides, or the wall itself may be composed entirely or partially of the catalyst material. The present invention includes the use of one or more catalyst material layers in the inlet and / or outlet walls of an element.

[0060] Wash coat on the substrate: First layer (bottom coat) The bottom coat is deposited on the substrate. Preferably, the bottom coat covers 90-100% of the substrate surface. More preferably, the bottom coat covers 95-100% of the substrate surface, and even more preferably, the bottom coat covers the entire accessible surface of the substrate. The term "accessible surface" refers to the surface of the substrate that can be covered by conventional coating techniques used in the field of catalyst preparation, such as impregnation techniques.

[0061] The first layer contains at least one first platinum group metal supported on the first carrier. The first platinum group metal is selected from palladium, platinum, and rhodium. Preferably, the first platinum group metal is palladium. Preferably, the second platinum group metal is rhodium. The amount of the first platinum group metal is in the range of 0.001 to 0.2 grams per cubic inch of the substrate. Preferably, the amount of the first platinum group metal is in the range of 0.029 to 0.174 grams per cubic inch (50 to 300 grams per cubic foot) of the substrate.

[0062] Preferably, the first carrier comprises alumina and a first oxygen storage component. The first oxygen storage component comprises ceria-zirconia. The alumina used as the carrier may include dopants selected from lantana, lantana, ceria, ceria-zirconia, zirconia, lantana-zirconia, barrier, barrier-lantana, barrier-lantana-neodymia, or combinations thereof. The amount of ceria in the first oxygen storage component is about 20 to about 45% by weight, based on the total weight of the first oxygen storage component. Preferably, the amount of ceria in the first oxygen storage component is about 30 to about 45% by weight, based on the total weight of the first oxygen storage component. More preferably, the amount of ceria is 40%, based on the total weight of the first oxygen storage component. The first layer may contain at least one alkaline earth metal oxide, including barium oxide, strontium oxide, or any combination thereof, in an amount of 1.0 to 20% by weight, based on the total weight of the first layer. The first layer may further contain barium and zirconium.

[0063] Second layer (top coat) The second layer contains at least one second platinum group metal supported on the second carrier. The second platinum group metal is selected from palladium, platinum, and rhodium. Preferably, the second platinum group metal is rhodium. The amount of the second platinum group metal is in the range of 0.001 to 0.2 grams per cubic inch of the substrate. Preferably, the amount of the second platinum group metal is in the range of 0.001 to 0.017 grams per cubic inch (2.0 to 30 grams per cubic foot) of the substrate.

[0064] The second carrier comprises alumina and a second oxygen storage component. The alumina used as the carrier may include dopants selected from lantana, lantana, ceria, ceria-zirconia, zirconia, lantana-zirconia, barrier, barrier-lantana, barrier-lantana-neodymia, or combinations thereof. The second oxygen storage component comprises ceria-zirconia. The amount of ceria in the second oxygen storage component is about 20 to about 45% by weight, based on the total weight of the second oxygen storage component. Preferably, the amount of ceria in the first oxygen storage component is about 30 to about 45% by weight, based on the total weight of the first oxygen storage component. More preferably, the amount of ceria is 40%, based on the total weight of the second oxygen storage component. The second layer may further comprise a ceria-zirconia composite.

[0065] The total amount of alumina calculated as Al2O3 from the first and second layers is 1.4 grams or more per cubic inch of the substrate. Preferably, the total amount of alumina from the first and second layers is 1.4 to 2.5 grams per cubic inch of the substrate.

[0066] The total amount of ceria calculated as CeO2 from the first and second layers is 0.6 grams or more per cubic inch of the substrate. Preferably, the total amount of ceria from the first and second layers is 0.6 to 1 gram per cubic inch of the substrate.

[0067] The weight ratio of ceria present in the first layer to ceria present in the second layer is greater than 1.7:1. Preferably, the weight ratio of ceria present in the first layer to ceria present in the second layer is in the range of approximately 1.7:1 to approximately 3.5:1.

[0068] The total amount of the first or second platinum group metal is in the range of 0.001 to 0.2 grams per cubic inch of the substrate.

[0069] Preparation of catalyst articles: In yet another aspect, the claimed invention is a process for preparing a catalyst article, -a) prepare a first layer slurry comprising at least one first platinum group metal, b) alumina, c) and a first oxygen storage component comprising ceria-zirconia, - To deposit the first layer slurry onto the substrate to obtain the first layer, -a) prepare a second layer slurry comprising at least one second platinum group metal, b) alumina, and c) a second oxygen storage component including ceria-zirconia. - A process is provided which includes depositing a slurry of a second layer on a first layer and subsequently firing it at a temperature in the range of 400 to 700°C to obtain a second layer, wherein the step of preparing the slurry of the first layer or the slurry of the second layer includes a technique selected from initial wet impregnation, initial wet co-impregnation, and post-addition.

[0070] In the process of preparing the catalyst article, the first layer is prepared using alumina and a first oxygen storage component containing ceria-zirconia, and the second layer is prepared using alumina, ceria-zirconia, and optionally a second oxygen storage component containing ceria-zirconia. The total amount of ceria from the first and second layers is 0.6 to 1 gram per cubic inch. The total amount of alumina from the first and second layers is 1.4 to 2.5 grams per cubic inch. The weight ratio of ceria present in the first layer to ceria present in the second layer is in the range of 1.7:1 to 3.5:1.

[0071] The process may involve a pre-process in which platinum, palladium, or both are fixed onto a support material by heat or chemical means.

[0072] Substrate coating: The catalyst compositions described above are typically prepared in the form of catalyst particles. These catalyst particles are mixed with water to form a slurry for coating catalyst substrates, such as honeycomb substrates. In addition to the catalyst particles, the slurry may optionally contain binders in the form of alumina, silica, zirconium acetate, zirconia, or zirconium hydroxide, associative thickeners, and / or surfactants (including anionic, cationic, nonionic, or amphoteric surfactants). Other exemplary binders include boehmite, gamma-alumina, or delta / theta-alumina, and silica sol. If present, binders are generally used in amounts of about 1–5% by weight of the total washcoat filling. Acidic or basic species are added to the slurry to adjust the pH. For example, in some embodiments, the pH of the slurry is adjusted by adding ammonium hydroxide, aqueous nitric acid solution, or acetic acid. The typical pH range of the slurry is about 3–12.

[0073] The slurry can be pulverized to reduce the particle size and promote particle mixing. Pulverization is achieved using a ball mill, continuous mill, or other similar equipment, and the solid content of the slurry may be, for example, about 20–60% by weight, more specifically, about 20–40% by weight. In one embodiment, the slurry after pulverization is characterized by a D90 particle size of about 3–40 microns, preferably 10–30 microns, and more preferably 10–15 microns. 90 This is determined using a dedicated particle size analyzer. The instrument used in this example uses laser diffraction to measure the particle size of a small amount of slurry. Typically, D is measured in microns. 90 This means that 90% of the particles have a diameter smaller than the quoted value.

[0074] The slurry is coated onto the catalyst substrate using any wash-coat technique known in the art. In one embodiment, the catalyst substrate is immersed in the slurry one or more times or otherwise coated with the slurry. The coated substrate is then dried at a high temperature (e.g., 100-150°C) for a certain period (e.g., 10 minutes to 3 hours), and then calcined by heating at, for example, 400-700°C, typically for about 10 minutes to about 3 hours. After drying and calcining, the final wash-coat coating layer is considered to be solvent-free in nature. After calcining, the catalyst filling amount obtained by the wash-coat technique described above can be determined by calculating the difference between the coated weight and the uncoated weight of the substrate. As will be apparent to those skilled in the art, the catalyst filling amount can be modified by changing the rheology of the slurry. In addition, the coating / drying / calcining process for producing the wash-coat can be repeated as needed to build up the coating to a desired level of filling or thickness, i.e., the wash-coat may be applied two or more times.

[0075] In certain embodiments, the coated substrate is aged by subjecting the coated substrate to heat treatment. In one embodiment, aging is carried out in an environment of 10 vol% moisture at a temperature of about 850°C to about 1050°C for 50 to 75 hours with alternating hydrocarbon / air supply. Thus, in certain embodiments, an aged catalyst article is provided. In some embodiments, particularly effective materials include metal oxide-based supports (including, but not limited to, substantially 100% ceria supports) that maintain a high percentage of pore volume (e.g., about 95 to 100%) during aging (e.g., aging at about 850°C to about 1050°C, with alternating hydrocarbon / air supply, 10 vol% moisture, 50 to 75 hours).

[0076] Emissions treatment system: In another aspect, the claimed invention also provides an exhaust system for an internal combustion engine, the system comprising a catalytic article as described herein. The catalytic article of the invention can be used as the sole catalytic component of an exhaust system, and the catalytic article of the invention is used downstream of the engine and positioned to receive exhaust gases from the engine. The catalytic article of the invention can also be used as part of an integrated exhaust system which includes one or more additional components for processing exhaust gas emissions.

[0077] For example, an exhaust system, also known as an exhaust treatment system, may further include a closely coupled TWC catalyst, an underfloor catalyst, a catalytic soot filter (CSF) component, and / or a selective catalytic reduction (SCR) catalyst article. The aforementioned list of components is merely an example and should not be construed as limiting the scope of the present invention.

[0078] Catalyst components can be placed in a tightly coupled position. Tightly coupled catalysts are placed near the engine to allow them to reach reaction temperature as quickly as possible. Generally, tightly coupled catalysts are placed within 3 feet of the engine, more specifically within 1 foot, and even more specifically less than 6 inches from the engine. Tightly coupled catalysts are often mounted directly to the exhaust gas manifold. Due to their proximity to the engine, tightly coupled catalysts need to be stable at high temperatures.

[0079] In another embodiment, the claimed invention further provides a method for reducing hydrocarbon, carbon monoxide, and nitrogen oxide levels in a gaseous exhaust flow, the method comprising bringing a gaseous exhaust flow into contact with a catalyst article or exhaust system as described herein to reduce the levels of hydrocarbon, carbon monoxide, and nitrogen oxides in the exhaust gas.

[0080] In another embodiment, the claimed invention also provides the use of catalyst articles as described herein for purifying gaseous exhaust streams containing hydrocarbons, carbon monoxide, and nitrogen oxides.

[0081] The present invention is further described by the following embodiments. The characteristics of each embodiment can be combined with any of the other embodiments where appropriate and practical.

[0082] Embodiment 1: a) A first layer comprising at least one first platinum group metal supported on a first carrier, The first carrier comprises alumina and a first oxygen storage component. The first oxygen storage component is a first layer containing ceria-zirconia, b) A second layer comprising at least one second platinum group metal supported on a second carrier, The second carrier comprises alumina and a second oxygen storage component. The second oxygen storage component is a second layer containing ceria-zirconia, c) A catalyst article comprising a base material, The total amount of alumina calculated as Al2O3 from the first and second layers is 1.4 grams or more per cubic inch of the substrate. The total amount of ceria calculated as CeO2 from the first and second layers is 0.6 grams or more per cubic inch of the substrate. The weight ratio of ceria present in the first layer to ceria present in the second layer is greater than 1.7:1. A catalyst article in which the total amount of the first or second platinum group metal is in the range of 0.001 to 0.2 grams per cubic inch of the substrate.

[0083] Embodiment 2: The catalyst article according to Embodiment 1, wherein the first or second platinum group metal is selected from palladium, platinum, and rhodium.

[0084] Embodiment 3: The catalyst article according to Embodiment 1 or 2, wherein the first platinum group metal is palladium.

[0085] Embodiment 4: The catalyst article according to any one of embodiments 1 to 3, wherein the second platinum group metal is rhodium.

[0086] Embodiment 5: A catalyst article according to any one of Embodiments 1 to 4, wherein the alumina comprises a dopant selected from lantana, ceria, ceria-zirconia, zirconia, lantana-zirconia, barrier, barrier-lantana, barrier-lantana-neodymia, or a combination thereof.

[0087] Embodiment 6: A catalyst article according to any one of Embodiments 1 to 5, wherein the amount of ceria in the first oxygen storage component is about 20 to about 45% by weight, based on the total weight of the first oxygen storage component.

[0088] Embodiment 7: A catalyst article according to any one of Embodiments 1 to 6, wherein the amount of ceria in the second oxygen storage component is about 20 to about 45% by weight, based on the total weight of the second oxygen storage component.

[0089] Embodiment 8: A catalyst article according to any one of Embodiments 1 to 7, wherein the total amount of alumina from the first and second layers is 1.4 to 2.5 grams per cubic inch of the substrate, and the total amount of ceria from the first and second layers is 0.6 to 1.0 gram per cubic inch of the substrate.

[0090] Embodiment 9: A catalyst article according to any one of Embodiments 1 to 8, wherein the weight ratio of ceria present in the first layer to ceria present in the second layer is in the range of approximately 1.7:1 to approximately 3.5:1.

[0091] Embodiment 10: A catalyst article according to any one of Embodiments 1 to 9, wherein the second layer comprises a ceria-zirconia composite.

[0092] Embodiment 11: A catalyst article according to any one of embodiments 1 to 10, wherein the first layer comprises at least one alkaline earth metal oxide, comprising 1.0 to 20% by weight of barium oxide, strontium oxide, or any combination thereof, based on the total weight of the first layer.

[0093] Embodiment 12: A catalyst article according to any one of Embodiments 1 to 11, wherein the base material is a ceramic base material, a metal base material, a ceramic foam base material, a polymer foam base material, or a woven fiber base material.

[0094] Embodiment 13: A catalyst article according to any one of Embodiments 1 to 12, wherein the first layer further comprises barium and zirconium, and the second layer comprises a ceria-zirconia composite.

[0095] Embodiment 14: A catalyst article comprising: a) a first layer supported on a first support containing at least one first platinum group metal, wherein the first platinum group metal is palladium, the first support contains alumina, and the first oxygen storage component contains ceria-zirconia, with ceria making up 40% based on the total weight of the first oxygen storage component; b) a second layer supported on a second support containing at least one second platinum group metal, wherein the second platinum group metal is rhodium, and the second support contains alumina-ceria and a second oxygen storage component containing ceria-zirconia, with ceria making up 40% based on the total weight of the second oxygen storage component; and c) a substrate. The total amount of alumina calculated as Al2O3 from the first and second layers was 1.4 to 2.5 grams per cubic inch of the substrate. The total amount of ceria calculated as CeO2 from the first and second layers was 0.6 to 1.0 grams per cubic inch of the substrate. The weight ratio of ceria present in the first layer to ceria present in the second layer is in the range of 1.7:1 to 3.5:1. A catalyst article according to the present invention, claimed, wherein the amount of a first or second platinum group metal is in the range of 0.001 to 0.2 grams per cubic inch of the substrate.

[0096] Embodiment 15: The catalyst article comprises a) a first layer containing at least one first platinum group metal in an amount of 0.029 to 0.174 grams per cubic inch of a substrate supported on a first carrier, wherein the first platinum group metal is palladium, and the first carrier contains alumina and a first oxygen storage component containing ceria-zirconia, wherein the amount of ceria is 40% based on the total weight of the first oxygen storage component, and b) a) Substrate, comprising: a second layer comprising at least one second platinum group metal in an amount of 0.001 to 0.017 grams per cubic inch of the substrate supported on the 2 carrier, wherein the second platinum group metal is rhodium, and the second carrier comprises alumina-ceria and a second oxygen storage component comprising ceria-zirconia, wherein the amount of ceria is 40% based on the total weight of the second oxygen storage component; The total amount of alumina from the first and second layers is 1.4 to 2.5 grams per cubic inch of the substrate. The total amount of ceria from the first and second layers is 0.6 to 1 gram per cubic inch of the substrate. A catalyst article according to the present invention, as claimed, wherein the weight ratio of ceria present in the first layer to ceria present in the second layer is in the range of 1.7:1 to 3.5:1.

[0097] Embodiment 16: The catalyst article comprises a) a first layer containing at least one first platinum group metal in an amount of 0.029 to 0.174 grams per cubic inch of a substrate supported on a first carrier, wherein the first platinum group metal is palladium, and the first carrier contains alumina and a first oxygen storage component containing ceria-zirconia, wherein the amount of ceria is 40% based on the total weight of the first oxygen storage component, and b) a) Substrate, comprising: a second layer comprising at least one second platinum group metal in an amount of 0.001 to 0.017 grams per cubic inch of the substrate supported on the 2 carrier, wherein the second platinum group metal is rhodium, and the second carrier comprises alumina-ceria and a second oxygen storage component comprising ceria-zirconia, wherein the amount of ceria is 40% based on the total weight of the second oxygen storage component; The total amount of alumina calculated as Al2O3 from the first and second layers was 1.4 to 2.5 grams per cubic inch of the substrate. The total amount of ceria calculated as CeO2 from the first and second layers was 0.6 to 1 gram per cubic inch of the substrate. The weight ratio of ceria present in the first layer to ceria present in the second layer is in the range of 1.7:1 to 3.5:1. A claimed catalyst article according to the present invention, wherein the first layer comprises barium and zirconium, and the second layer comprises a ceria-zirconia composite.

[0098] The claimed aspects of the present invention are more fully illustrated by the following embodiments, which are provided to illustrate certain aspects of the invention and should not be construed as limiting them.

[0099] The examples provided herein below have the following characteristics: [Table 1]

[0100] Example 1: Preparation of a two-layer catalyst article (Catalyst D of the present invention) 97g / ft 3A Pd / Rh catalyst article (Pt / Pd / Rh = 0 / 81 / 16) having the PGM loading was prepared. Catalyst D of the present invention is a two-layer washcoat structure coated on an elliptical monolithic cordierite substrate having dimensions of 5.16 inches and 3.54 inches in diameter, 5.05 inches in length, 900 cpsi of cell density, and 2.0 mils of wall thickness.

[0101] Preparation of bottom coat: A slurry containing about 35.1 wt% of refractory alumina having 4.0 wt% of lanthanum oxide, 49.6 wt% of stabilized ceria-zirconia OSC having about 40 wt% of ceria, barium acetate providing 11.6 wt% of BaO, zirconium acetate providing 1.9 wt% of ZrO2, and 1.8 wt% of Pd (metallic) was coated onto the substrate. After calcining at 550°C in air for 1 hour, the washcoat loading of the bottom coat is about 2.59 g / in 3

[0102] Preparation of top coat: A slurry containing about 56.3 wt% of refractory alumina having 8 wt% of ceria, 33.1 wt% of stabilized ceria-zirconia OSC having about 40 wt% of ceria, 9.9 wt% of ceria-zirconia composite having about 50 wt% of ceria, and 0.61 wt% of Rh was coated onto the bottom coat. After calcining at 550°C in air for 1 hour, the washcoat loading of the top coat is about 1.51 g / in 3

[0103] Example 2: Comparative Catalyst Article A 97 g / ft 3 A Pd / Rh catalyst article (Pt / Pd / Rh = 0 / 81 / 16) having the PGM loading was prepared. Catalyst Article A is a two-layer washcoat structure coated on an elliptical monolithic cordierite substrate having dimensions of 5.16 inches and 3.54 inches in diameter, 5.05 inches in length, 900 cpsi of cell density, and 2.0 mils of wall thickness.

[0104] ​​Preparation of the bottom coat: A slurry containing approximately 65% ​​refractory alumina with 1.3% lanthanum oxide, 10.8% stabilized ceria-zirconia OSC with approximately 28.5% ceria, barium acetate yielding 5.4% BaO, strontium acetate yielding 5.4% SrO, zirconium acetate yielding 5.4% ZrO2, lanthanum nitrate yielding 5.4% La2O3, and 2.5% Pd was coated onto the substrate. After firing at 550°C in air for 1 hour, the wash coat filling amount of the bottom coat was approximately 1.85 g / in. 3 That was the case.

[0105] Top coat preparation: A slurry containing approximately 26.5 wt% refractory alumina with 4 wt% lanthanum oxide, 66.3 wt% stabilized ceria-zirconia OSC with approximately 28.5 wt% ceria, zirconium acetate yielding 6.6 wt% ZrO2, and 0.62 wt% Rh was coated onto the bottom coat. After firing at 550°C in air for 1 hour, the wash coat filling amount of the top coat was approximately 1.51 g / in. 3 That was the case.

[0106] Example 3: Comparative catalyst article B 97g / ft 3 A Pd / Rh catalyst article (Pt / Pd / Rh = 0 / 81 / 16) with a PGM filling amount was prepared. Catalyst B is a two-layer wash-coat structure coated on an elliptical monolithic cordierite substrate having dimensions of 5.16 inches and 3.54 inches in diameter, 5.05 inches in length, a cell density of 900 cpsi, and a wall thickness of 2.0 mils.

[0107] Preparation of the bottom coat: A slurry containing approximately 28.1% by weight of refractory alumina with 4% by weight of lanthanum oxide, 51.2% by weight of stabilized ceria-zirconia OSC with approximately 40% by weight of ceria, 9.7% by weight of ceria-zirconia composite with approximately 50% by weight of ceria, 1.5% by weight of zirconia-yttrium composite with approximately 40% by weight of yttrium, lanthanum nitrate yielding 0.5% by weight of La2O3, barium acetate and barium sulfate yielding 6.4% by weight of BaO, zirconium acetate yielding 0.3% by weight of ZrO2, colloidal alumina binder yielding 0.5% by weight of Al2O3, and 1.8% by weight of Pd was coated onto the substrate. After firing at 550°C in air for 1 hour, the wash coat filling amount of the bottom coat was approximately 2.16 g / in. 3 That was the case.

[0108] Top coat preparation: A slurry containing approximately 43.8 wt% refractory alumina with 1.7 wt% lanthanum oxide, 51.1 wt% stabilized ceria-zirconia OSC with approximately 40 wt% ceria, barium sulfate and barium hydroxide yielding 2.1 wt% BaO, colloidal alumina binder yielding 1.8 wt% Al2O3, 0.60 wt% Pd, and 0.68 wt% Rh was coated onto the bottom coat. After firing in air at 550°C for 1 hour, the wash coat filling amount of the top coat was approximately 1.38 g / in. 3 That was the case.

[0109] Example 4: Comparative catalyst article C 97g / ft 3 A Pd / Rh catalyst article (Pt / Pd / Rh = 0 / 81 / 16) with a PGM filling amount was prepared. Catalyst article C is a two-layer wash-coat structure coated on an elliptical monolithic cordierite substrate having dimensions of 5.16 inches and 3.54 inches in diameter, 5.05 inches in length, a cell density of 900 cpsi, and a wall thickness of 2.0 mils.

[0110] Preparation of the bottom coat: A slurry containing approximately 20.9 wt% refractory alumina with 4 wt% lanthanum oxide, 63.7 wt% stabilized ceria-zirconia OSC with approximately 40 wt% ceria, barium acetate yielding 11.6 wt% BaO, zirconium acetate yielding 1.9 wt% ZrO2, and 1.8 wt% Pd was coated onto the substrate. After firing at 550°C in air for 1 hour, the wash coat filling amount of the bottom coat was approximately 2.59 g / in. 3 That was the case.

[0111] Top coat preparation: A slurry containing approximately 33.1% refractory alumina with 8% ceria, 56.3% stabilized ceria-zirconia OSC with approximately 40% ceria, 9.9% ceria-zirconia composite with approximately 50% ceria, and 0.61% Rh was coated onto the bottom coat. After firing in air at 550°C for 1 hour, the wash coat filling amount of the top coat was approximately 1.51 g / in. 3 That was the case.

[0112] Example 5: Catalyst Article E Catalyst article E has a concentration of 3 g / ft 3 This is an Rh catalyst article (Pt / Pd / Rh=0 / 0 / 3) with a PGM filling amount. Catalyst E is a single-layer wash-coat structure coated on an elliptical monolithic cordierite substrate having dimensions of 5.16 inches and 3.54 inches in diameter, 5.05 inches in length, a cell density of 400 cpsi, and a wall thickness of 4 mils.

[0113] A slurry containing approximately 63.1% by weight of refractory Al2O3, 32.0% by weight of stabilized ceria-zirconia OSC, 1.5% by weight of barium acetate yielding BaO, 0.3% by weight of zirconium acetate yielding ZrO2, 1.5% by weight of strontium acetate yielding SrO, and 0.06% by weight of Rh was coated onto the substrate. After firing in air at 550°C for 1 hour, the wash coat filling amount was approximately 2.8 g / in. 3 That was the case.

[0114] Example 6: Testing of catalyst articles Catalyst items A, B, C, and D were aged for 150 hours at an effective catalyst temperature of 1022°C under engine settings using a 4-mode exothermic aging protocol. Catalyst item E was aged for 100 hours at an effective catalyst temperature of 910°C under engine settings using a 4-mode exothermic aging protocol. The engine outgassing supply composition was alternately switched between rich and lean to simulate typical vehicle operating conditions.

[0115] Exhaust performance was tested using a 2.0L turbocharged ULEV70 vehicle equipped with a proximal coupling (CC) + underfloor (UF) exhaust purification system configuration, operating under the FTP-75 test protocol. Catalytic converters A, B, C, and D were tested as CC catalysts, while catalyst E was used as a general UF catalyst.

[0116] result: The results are illustrated in Figure 1. Catalyst article D of the present invention, after high-temperature aging, exhibits the lowest tailpipe emissions for all three emission types (NMHC, NOx, and CO) among the four CC catalysts (A, B, C, and D). Compared to the comparative catalyst, NMHC + NOx emissions are lower. x A total reduction of up to approximately 68% was achieved, and a reduction of up to approximately 76% was achieved in CO2 emissions.

[0117] Furthermore, the oxygen storage capacity (OSC) of the aged catalyst article was measured at engine settings. The results are shown in Figure 2. Catalyst article D of the present invention exhibits the highest OSC, even though other catalysts prepared have similar (catalyst B) or more (catalyst C) OSC material.

[0118] The results clearly demonstrate the presence of three key characteristics that reduce the discharge of catalyst material, improve oxygen storage capacity, and thereby enhance thermal stability: namely, the total amount of alumina from the first and second layers, the total amount of ceria, and the ratio of ceria (distribution of ceria in the two layers).

[0119] The following can be observed: a) Catalyst article A uses the desired amount of alumina but does not function very efficiently. This may be because the total amount of ceria is less and the ratio of ceria in the first layer to the second layer is lower. b) Catalyst article B exhibits the desired total amount and ratio of ceria from the first and second layers, but it was found to be less efficient because the total amount of alumina was less than the required amount. c) Catalyst article C having the desired total amount of ceria but a smaller total amount of alumina, as well as a lower ratio of ceria from the first and second layers, does not function very efficiently.

[0120] Throughout this specification, references to “one embodiment,” “a particular embodiment,” “one or more embodiments,” or “an embodiment” mean that any particular feature, structure, material, or property described in relation to an embodiment is included in at least one embodiment of the claimed invention. Therefore, the appearance of phrases such as “in one or more embodiments,” “in a particular embodiment,” “in some embodiments,” “in one embodiment,” or “in an embodiment” in various places throughout this specification does not necessarily refer to the same embodiment of the claimed invention. Furthermore, particular features, structures, materials, or properties may be combined in any preferred manner in one or more embodiments. All the various embodiments, aspects, and options disclosed herein can be combined in all variations, regardless of whether such features or elements are explicitly combined in the description of a particular embodiment herein. The claimed invention is intended to be read holistically so that, unless the context otherwise explicitly indicates, any of its various aspects and embodiments is intended to be intended to be combined with any separable feature or element of the disclosed invention.

[0121] While the embodiments disclosed herein are described with reference to specific embodiments, it should be understood that these embodiments are merely illustrative of the principles and uses of the claimed invention. It will be apparent to those skilled in the art that various modifications and changes may be made to the claimed methods and apparatus of the claimed invention without departing from the spirit and scope of the claimed invention. Accordingly, the claimed invention is intended to include modifications and changes within the scope of the appended claims and their equivalents, and the above embodiments are presented for illustrative purposes only and are not limiting. All patents and publications cited herein are incorporated herein by reference for the specific teachings described herein, unless other statements relating to incorporation are specifically provided.

Claims

1. a) A first layer comprising at least one first platinum group metal supported on a first carrier, The first carrier comprises alumina and a first oxygen storage component. The first oxygen storage component comprises a first layer containing ceria-zirconia, b) A second layer comprising at least one second platinum group metal supported on a second carrier, The second carrier comprises alumina and a second oxygen storage component, The second oxygen storage component comprises a second layer containing ceria-zirconia, c) A base material, The catalyst article wherein the first layer is a bottom coat deposited on at least a portion of the substrate, and the second layer is a top coat deposited on at least a portion of the first layer, From the first and second layers, Al ２ O ３ The total amount of alumina calculated as follows is 1.4 grams or more per cubic inch of the base material, or 0.08543 grams or more per cubic centimeter. From the first and second layers, CeO ２ The total amount of ceria calculated as follows is 0.6 grams or more per cubic inch of the base material, or 0.03661 grams or more per cubic centimeter. The weight ratio of ceria present in the first layer to the ceria present in the second layer is greater than 1.7:1, that is, (weight of ceria present in the first layer) / (weight of ceria present in the second layer) > 1.

7. The total amount of the first or second platinum group metal is in the range of 0.001 to 0.2 grams per cubic inch of the substrate, i.e., 0.0006102 to 0.01220 grams per cubic centimeter, and The alumina in the first support is doped with lanthanum oxide, and the alumina in the second support is doped with ceria, and The second platinum group metal is rhodium, in the ternary conversion (TWC) catalyst article.

2. The ternary conversion (TWC) catalyst article according to claim 1, wherein the first platinum group metal is selected from palladium, platinum, and rhodium.

3. The ternary conversion (TWC) catalyst article according to claim 1 or 2, wherein the first platinum group metal is palladium.

4. The ternary conversion (TWC) catalyst article according to any one of claims 1 to 3, wherein the amount of ceria in the first oxygen storage component is 20 to 45% by weight, based on the total weight of the first oxygen storage component.

5. The ternary conversion (TWC) catalyst article according to any one of claims 1 to 4, wherein the amount of ceria in the second oxygen storage component is 20 to 45% by weight, based on the total weight of the second oxygen storage component.

6. A ternary conversion (TWC) catalyst article according to any one of claims 1 to 5, wherein the total amount of alumina from the first and second layers is 1.4 to 2.5 grams per cubic inch of the substrate, i.e., 0.08542 to 0.1526 grams per cubic centimeter, and the total amount of ceria from the first and second layers is 0.6 to 1.0 grams per cubic inch of the substrate, i.e., 0.03661 to 0.06102 grams per cubic centimeter.

7. A ternary conversion (TWC) catalyst article according to any one of claims 1 to 6, wherein the weight ratio of ceria present in the first layer to ceria present in the second layer is in the range of 1.7:1 to 3.5:

1.

8. The ternary conversion (TWC) catalyst article according to any one of claims 1 to 7, wherein the second layer comprises a ceria-zirconia composite.

9. A ternary conversion (TWC) catalyst article according to any one of claims 1 to 8, wherein the first layer comprises at least one alkaline earth metal oxide, comprising 1.0 to 20% by weight of barium oxide, strontium oxide, or any combination thereof, based on the total weight of the first layer.

10. The ternary conversion (TWC) catalyst article according to any one of claims 1 to 9, wherein the substrate is a ceramic substrate, a metal substrate, a ceramic foam substrate, a polymer foam substrate, or a woven fiber substrate.

11. The aforementioned ternary conversion (TWC) catalyst article is a) A first layer comprising at least one first platinum group metal in an amount of 0.029 to 0.174 grams per cubic inch of the substrate supported on the first carrier, i.e., 0.001770 to 0.01062 grams per cubic centimeter, The first platinum group metal is palladium, and the first carrier comprises alumina and the first oxygen storage component containing ceria-zirconia. The first layer has a ceria content of 40% based on the total weight of the first oxygen storage component, b) A second layer comprising at least one second platinum group metal in an amount of 0.001 to 0.017 grams per cubic inch of the substrate supported on the second carrier, i.e., 0.0006102 to 0.001037 grams per cubic centimeter, wherein the second platinum group metal is rhodium. The support comprises alumina-ceria and the second oxygen storage component containing ceria-zirconia, The amount of ceria is 40% based on the total weight of the second oxygen storage component, in the second layer, c) A base material, The total amount of alumina from the first and second layers is 1.4 to 2.5 grams per cubic inch of the substrate, or 0.08542 to 0.1526 grams per cubic centimeter. The total amount of ceria from the first and second layers is 0.6 to 1 gram per cubic inch of the substrate, or 0.03661 to 0.06102 grams per cubic centimeter. A ternary conversion (TWC) catalyst article according to any one of claims 1 to 10, wherein the weight ratio of ceria present in the first layer to ceria present in the second layer is in the range of 1.7:1 to 3.5:

1.

12. A ternary conversion (TWC) catalyst article according to any one of claims 1 to 11, wherein the first layer further comprises barium and zirconium, and the second layer comprises a ceria-zirconia composite.

13. A process for preparing a ternary conversion (TWC) catalyst article according to any one of claims 1 to 12, - a) prepare a first layer slurry comprising at least one first platinum group metal, b) alumina, and c) a first oxygen storage component comprising ceria-zirconia. - To deposit the first layer slurry onto the substrate to obtain the first layer, - Prepare a second layer slurry comprising a) at least one second platinum group metal, b) alumina, and c) a second oxygen storage component including ceria-zirconia. - The process includes depositing the second layer slurry on the first layer to obtain a second layer, and then firing it at a temperature in the range of 400 to 700°C. A process comprising the step of preparing the first layer slurry or the second layer slurry, comprising a technique selected from initial wet impregnation, initial wet co-impregnation, and post-addition.

14. The process according to claim 13, wherein the total amount of ceria from the first and second layers is 0.6 grams or more per cubic inch of the substrate, i.e., 0.03661 grams or more per cubic centimeter, and the weight ratio of ceria present in the first layer to ceria present in the second layer is in the range of 1.7:1 to 3.5:

1.

15. An exhaust system for an internal combustion engine, comprising a ternary converter (TWC) catalyst article as described in any one of claims 1 to 12.

16. A method for treating a gaseous exhaust flow containing hydrocarbons, carbon monoxide, and nitrogen oxides, comprising contacting the exhaust flow with a ternary conversion (TWC) catalyst article according to any one of claims 1 to 12 or an exhaust system according to claim 15.

17. A method for reducing hydrocarbon levels, carbon monoxide levels, and nitrogen oxide levels in a gaseous exhaust flow, comprising bringing the gaseous exhaust flow into contact with a ternary conversion (TWC) catalyst article according to any one of claims 1 to 12 or an exhaust system according to claim 15 to reduce hydrocarbon levels, carbon monoxide levels, and nitrogen oxide levels in the exhaust gas.

18. Use of a ternary conversion (TWC) catalyst article according to any one of claims 1 to 12 for purifying a gaseous exhaust stream containing hydrocarbons, carbon monoxide, and nitrogen oxides.

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