Zone-type three-way conversion catalysts containing platinum, palladium, and rhodium

Abstract

The present invention provides a catalytic article comprising a substrate, a bottom washcoat deposited on the substrate, and a top washcoat deposited on the bottom washcoat, the bottom washcoat comprising a zoned configuration, the zoned configuration comprising a first zone and a second zone, the first zone comprising palladium supported on a ceria-zirconia mixed oxide or alumina or both, the second zone comprising platinum supported on a ceria-alumina composite, and the top washcoat comprising rhodium supported on alumina or a ceria-alumina composite. The present invention also provides a process for preparing the catalytic article, and its use for purifying a gaseous exhaust stream.

Description

[Technical field]

[0001] The invention claimed herein relates to catalysts useful in treating exhaust gases to reduce contaminants contained therein. In particular, the invention claimed herein relates to catalyst articles comprising a zoned three-way conversion (TWC) catalyst comprising platinum, palladium, and rhodium. [Background technology]

[0002] Three-way conversion (TWC) catalysts are well known for their catalytic activity in reducing pollutants such as NO, CO, and HC using platinum group metals (PGMs). Conventional TWC catalysts use Pd and Rh as the active catalyst components. Considering the current PGM market prices, replacing some of the more expensive Pd with less expensive Pt in TWC catalysts would help catalytic converter manufacturers and automobile manufacturers to significantly reduce costs. Therefore, the present invention focuses on developing highly active zoned TWC catalysts that contain platinum, palladium, and rhodium as PGM components. It has been found that replacing a significant amount of Pd with Pt (e.g., 50%) in TWC catalysts is feasible for applications with relatively high engine-out temperatures. However, in applications with relatively low engine-out temperatures, HC slip may be an issue, especially during the cold start period of the drive cycle.

[0003] Therefore, it is desirable to design a Pt / Pd / Rh-based TWC catalyst with suitable structure to improve the emission control efficiency, especially the low-temperature HC performance.

[0004] Object of the invention The object of the present invention is to improve the HC cold start performance of three-way conversion (TWC) catalysts containing Pt, Pd, and Rh as the active platinum group metal (PGM) components. Summary of the Invention

[0005] The present invention provides a catalytic article comprising a substrate, a bottom washcoat deposited on the substrate, and a top washcoat deposited on the bottom washcoat, the bottom washcoat comprising a zoned configuration comprising a first zone and a second zone, the first zone comprising palladium supported on a ceria-zirconia mixed oxide or alumina or both, the second zone comprising platinum supported on a ceria-alumina composite, and the top washcoat comprising rhodium supported on alumina or a ceria-alumina composite.

[0006] The present invention also provides a process for preparing a catalyst article comprising: a) preparing a bottom washcoat comprising a first zone and a second zone, the first zone being obtained by preparing a first slurry comprising palladium supported on ceria-zirconia mixed oxide or alumina or both and coating the first slurry onto a first portion of a substrate, and the second zone being obtained by preparing a second slurry comprising platinum supported on a ceria-alumina composite and coating the second slurry onto a second portion of the substrate; b) preparing a top washcoat by depositing a third slurry comprising rhodium supported on alumina onto the bottom washcoat; and c) subjecting the substrate to calcination at a temperature in the range of 400-700° C., wherein the step of preparing the slurries comprises a technique selected from incipient wetness impregnation, incipient wetness co-impregnation, or post-addition. [Brief description of the drawings]

[0007] To provide an understanding of embodiments of the present invention, reference is made to the accompanying drawings, which are not necessarily drawn to scale, and in which reference numerals refer to components of exemplary embodiments of the present invention. The drawings are merely illustrative and should not be construed as limiting the present invention. The above and other features of the present invention, its nature and various advantages will become more apparent when considered in conjunction with the following detailed description in conjunction with the accompanying drawings. [Figure 1A] FIG. 2 shows a comparative two-layer non-zoned catalyst article. [Figure 1B] FIG. 2 shows a comparative two-layer non-zoned catalyst article. [Figure 1C] FIG. 2 illustrates a two-layer zoned catalyst article according to an exemplary embodiment of the present invention. [Figure 1D] FIG. 2 illustrates a two-layer zoned catalyst article according to an exemplary embodiment of the present invention. [Figure 1E] FIG. 2 illustrates a two-layer zoned catalyst article according to an exemplary embodiment of the present invention. [Figure 1F] FIG. 2 illustrates a two-layer zoned catalyst article according to an exemplary embodiment of the present invention. [Figure 1G] FIG. 2 illustrates a two-layer zoned catalyst article according to an exemplary embodiment of the present invention. [Figure 1H] FIG. 2 illustrates a two-layer zoned catalyst article according to an exemplary embodiment of the present invention. [Figure 1I] FIG. 2 illustrates a two-layer zoned catalyst article according to an exemplary embodiment of the present invention. [Figure 1J] FIG. 2 illustrates a two-layer zoned catalyst article according to an exemplary embodiment of the present invention. [Figure 2A] 1 is a perspective view of a honeycomb-type substrate support that may include a catalyst composition according to one embodiment of the presently claimed invention. [Figure 2B] 2B is an enlarged partial cross-sectional view of FIG. 2A taken along a plane parallel to an end face of the substrate support of FIG. 2A, showing an expanded view of a number of gas flow passages shown in FIG. 2A. [Diagram 3] FIG. 2B is an enlarged cross-sectional cutaway view of FIG. 2A, in which the honeycomb-shaped substrate of FIG. 2A represents a wall-flow filter substrate monolith. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] The invention claimed herein is described more fully below. The invention claimed herein may be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein; these embodiments are provided so that the invention claimed herein will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. No language in the specification should be construed as indicating any non-claimed element essential to the practice of the disclosed materials and methods.

[0009] All methods described herein can be carried out in any suitable order unless otherwise indicated herein or clearly contradicted by the context. The use of any and all examples or exemplary terms (e.g., "etc.") provided herein is intended merely to further describe the materials and methods, and does not impose limitations on the scope unless otherwise stated.

[0010] Definition: The use of the terms "a," "an," "the," and similar referents in the context of describing the materials and methods discussed herein (particularly in the context of the claims which follow) should be construed to encompass both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context.

[0011] The recitation of ranges of values ​​herein, unless otherwise stated herein, is merely intended to serve as a shorthand method of referring individually to each separate value within the range, and each separate value is incorporated herein as if it were individually recited herein.

[0012] In the context of the present invention, the term "first layer" is used interchangeably with "bottom layer," "bottom coat," or "bottom washcoat," while the term "second layer" is used interchangeably with "top layer," "top coat," or "top washcoat." 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.

[0013] In the context of the present invention, the term "first zone" is used interchangeably with "inlet zone" or "front zone", and the term "second zone" is used interchangeably with "outlet zone" or "rear zone". The terms "first zone" and "second zone" also describe the relative position of the catalytic article in the flow direction, respectively, when placed in an exhaust gas treatment system. The first zone is located upstream, while the second zone is located downstream. The first zone covers at least a portion of the substrate from the inlet of the substrate, while the second zone covers at least a portion of the substrate from the outlet of the substrate. The inlet of the substrate is a first end that can receive a flow of engine exhaust gas stream from the engine, while the outlet of the substrate is a second end from which the treated exhaust gas stream exits.

[0014] The term "three-way conversion catalyst" or TWC catalyst refers to a catalyst that simultaneously a) reduces nitrogen oxides to nitrogen and oxygen, b) oxidizes carbon monoxide to carbon dioxide, and c) oxidizes unburned hydrocarbons to carbon dioxide and water.

[0015] The term "NOx" refers to nitrogen oxide compounds such as NO and / or NO2.

[0016] As used herein, the term "washcoat" has its ordinary meaning in the art of a thin, adherent coating of catalytic or other material applied to a substrate material. Generally, washcoats are formed by preparing a slurry containing particles of a particular solids content (e.g., 15-60% by weight) in a liquid vehicle, which is then coated onto the substrate and dried to provide the washcoat layer.

[0017] The hydrothermal stability of a catalyst may be functionally defined as the retention of sufficient catalytic function after high temperature aging. Specifically, in this context, hydrothermal stability means that the catalyst must have a NOx and hydrocarbon light-off temperature of less than 350°C after aging with steam at temperatures ranging from 850°C to 1050°C for about 5 to 300 hours.

[0018] As used herein, the term "stream" refers broadly to any combination of flowing gases that may contain solid or liquid particulate matter.

[0019] As used herein, the terms "upstream" and "downstream" refer to the relative directions of engine exhaust gas flow from the engine toward the exhaust pipe, with the engine being at the upstream location and the exhaust pipe and any pollution control articles such as filters and catalysts being downstream from the engine.

[0020] In the context of the present invention, the amount of platinum group metals, such as platinum / palladium / rhodium, and / or support materials, such as ceria-zirconia mixed oxide, ceria-alumina composite, alumina, etc., is calculated as weight % based on the total weight of the washcoat present on the substrate. That is, the amount is calculated without considering the amount of the substrate, although the substrate is also part of the catalytic article. The washcoat includes a top washcoat, a bottom washcoat, and optionally any further coating layers. Preferably, the washcoat is a top washcoat and a bottom washcoat.

[0021] The present invention focuses on addressing the low temperature HC breakthrough problem associated with conventional Pt / Pd / Rh trimetallic TWC technology. Thus, a Pt / Pd / Rh-based TWC catalyst article is designed with a zoned washcoat structure. The inventive design allows for an inlet zone (first zone) to be Pd-rich for fast HC light-off during cold start, and utilizes a Pt-rich outlet zone (second zone) for HC high temperature performance after light-off. Vehicle and engine evaluation data demonstrated that the inventive catalyst article exhibits improved HC conversion compared to non-zoned designs.

[0022] Catalyst article: In a first aspect, the present invention provides a method for producing a composition comprising the steps of: a) a substrate; b) a bottom washcoat deposited on the substrate; and c) a top washcoat deposited on the bottom coat; and Including, the bottom washcoat comprises a zoned configuration; the zoned configuration includes a first zone and a second zone; the first zone comprises palladium supported on a ceria-zirconia mixed oxide or alumina or both; the second zone comprises platinum supported on a ceria-alumina composite; A catalyst article is provided in which the top washcoat comprises rhodium supported on alumina or a ceria-alumina composite.

[0023] Support material: "Support" in the context of a catalyst material or catalyst composition or catalyst washcoat refers to a material that receives metals (e.g., PGMs), stabilizers, promoters, binders, etc., by precipitation, association, dispersion, impregnation, or other suitable method.

[0024] Ceria-alumina composite: Ceria-alumina composites are composites in which CeO2 is distributed on the surface and / or in the bulk of the alumina as particles and / or nanoclusters. Each oxide may have its distinct chemical and solid-state physical state, but the oxides can interact through their interfaces. The surface CeO2 modification of the alumina can be in the form of separate moieties (particles or clusters) or in the form of a layer of ceria that partially or completely covers the surface of the alumina.

[0025] The amount of CeO2 (cerium oxide) in the ceria-alumina composite present in the top and / or bottom washcoat is preferably 1.0-50 wt% based on the total weight of the ceria-alumina composite. More preferably, the amount of CeO2 in the ceria-alumina composite present in the top and / or bottom washcoat is 5.0-50 wt% based on the total weight of the ceria-alumina composite. Even more preferably, the amount of CeO2 in the ceria-alumina composite present in the top and / or bottom washcoat is 5-30 wt% based on the total weight of the ceria-alumina composite. And even more preferably, the amount of CeO2 in the ceria-alumina composite present in the top and / or bottom washcoat is 8-20 wt% based on the total weight of the ceria-alumina composite.

[0026] The amount of Al2O3 (aluminum oxide) in the ceria-alumina composite present in the top and / or bottom washcoat is preferably 50-99 wt% based on the total weight of the ceria-alumina composite. More preferably, the amount of Al2O3 in the ceria-alumina composite present in the top and / or bottom washcoat is 50-95 wt% based on the total weight of the ceria-alumina composite. Even more preferably, the amount of Al2O3 in the ceria-alumina composite present in the top and / or bottom washcoat is 70-95 wt% based on the total weight of the ceria-alumina composite. And even more preferably, the amount of Al2O3 in the ceria-alumina composite present in the top and / or bottom washcoat is 80-92 wt% based on the total weight of the ceria-alumina composite.

[0027] Preferably, the average particle size of the ceria in the ceria-alumina composite is less than 200 nm. Preferably, the particle size is in the range of 5.0 nm to 50 nm. The particle size is determined by a transmission electron microscope.

[0028] The ceria-alumina composite present in the top and / or bottom washcoats may include a dopant selected from zirconia, lanthana, titania, hafnia, magnesia, calcia, strontian, baria, or any combination thereof. The total amount of dopant in the ceria-alumina composite is preferably in the range of 0.001 to 15 wt. % based on the total weight of the ceria-alumina composite.

[0029] Ceria-alumina composites can be made by methods known to those skilled in the art, such as co-precipitation or surface modification. In these methods, a suitable cerium-containing precursor is contacted with a suitable aluminum-containing precursor, and then the mixture thus obtained is converted into a ceria-alumina composite. Suitable cerium-containing precursors are, for example, water-soluble cerium salts and colloidal ceria suspensions. Ceria-alumina can also be prepared by atomic layer deposition, in which a ceria compound is selectively reacted with the alumina surface to form ceria on the alumina surface after calcination. This deposition / calcination step can be repeated until a layer of the desired thickness is reached. Suitable aluminum-containing precursors are, for example, aluminum oxides, such as gibbsite, boehmite gamma alumina, delta alumina, or theta alumina, or combinations thereof. The conversion of the mixture thus obtained into a ceria-alumina composite can then be achieved by a calcination step of the mixture.

[0030] Ceria-Zirconia Mixed Oxide (CZO): The term complex metal oxide refers to a mixed metal oxide containing oxygen anions and at least two different metal cations. In ceria-zirconia mixed oxide, the cerium cation and the zirconium cation are distributed within the oxide lattice structure. The terms "complex oxide" and "mixed oxide" can be used interchangeably. Because the metal cations are distributed within the oxide lattice structure, these structures are also commonly called solid solutions.

[0031] Preferably, the ceria (calculated as CeO2) of the ceria-zirconia mixed oxide present in the top and / or bottom washcoat is present in an amount of 10 to 75 wt. %, based on the total weight of the ceria-zirconia mixed oxide, and the zirconia (calculated as ZrO2) of the ceria-zirconia mixed oxide present in the top and / or bottom washcoat is present in an amount of 25 to 90 wt. %, based on the total weight of the ceria-zirconia mixed oxide.

[0032] More preferably, the ceria (calculated as CeO2) of the ceria-zirconia mixed oxide present in the top and / or bottom washcoat is present in an amount of 20 to 50 wt. %, based on the total weight of the ceria-zirconia mixed oxide, and the zirconia (calculated as ZrO2) of the ceria-zirconia mixed oxide present in the top and / or bottom washcoat is present in an amount of 50 to 80 wt. %, based on the total weight of the ceria-zirconia mixed oxide.

[0033] Even more preferably, the ceria (calculated as CeO2) of the ceria-zirconia mixed oxide present in the top and / or bottom washcoat is present in an amount of 30 to 50 wt. %, based on the total weight of the ceria-zirconia mixed oxide, and the zirconia (calculated as ZrO2) of the ceria-zirconia mixed oxide present in the top and / or bottom washcoat is present in an amount of 50 to 70 wt. %, based on the total weight of the ceria-zirconia mixed oxide.

[0034] In a preferred embodiment, the ceria-zirconia mixed oxide present in the top and / or bottom washcoat comprises a dopant selected from lanthana, titania, hafnia, magnesia, calcia, strontia, baria, yttrium, hafnium, praseodymium, neodymium, or any combination thereof. The dopant metal may be incorporated into the crystal structure of the complex metal oxide in cationic form, may be deposited on the surface of the complex metal oxide in oxide form, or may be present as a blend of a mixture of both the dopant and the complex metal oxide in microscale oxide form. The dopant is included in an amount of 1-20 wt.%, or more preferably 5-15 wt.%, based on the total weight of the complex metal oxide.

[0035] alumina: The alumina present in the top and / or bottom washcoat can be gamma alumina or activated alumina. It typically has an average surface area of ​​greater than 60 square meters per gram ("m2 / g"), often up to about 200 m2. 2The BET surface area of ​​the fresh material is preferably 1.0-1.5 g / g or more. Activated alumina is usually a mixture of gamma and delta phases of alumina, but may contain significant amounts of eta, kappa, and theta alumina phases. Activated alumina includes high bulk density gamma-alumina, low or medium bulk density large pore gamma-alumina, low bulk density large pore boehmite or gamma-alumina. The alumina present in the top and / or washcoat may be doped with a dopant selected from barium, lanthana, zirconia, neodymian, yttria, or titania, the amount of said dopant being preferably 1.0-30 wt.% based on the total weight of alumina and dopant. Examples of aluminas doped with a dopant include, but are not limited to, lanthana-alumina, titania-alumina, ceria-zirconia-alumina, zirconia-alumina, lanthana-zirconia-alumina, baria-alumina, baria-lanthana-alumina, baria-lanthana-neodymia-alumina, or any combination thereof.

[0036] Base material: The substrate of the catalyst article of the presently claimed invention may be composed of any material typically used to prepare automotive catalysts. In preferred embodiments, the substrate is a ceramic substrate, a metal substrate, a ceramic foam substrate, a polymer foam substrate, or a woven fiber substrate. In more preferred embodiments, the substrate is a ceramic or metal monolith honeycomb structure.

[0037] The substrate provides a plurality of walls to which a washcoat containing the catalyst composition described hereinabove is applied and adhered, thereby acting as a support for the catalyst composition.

[0038] Preferred metal substrates 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 of nickel, chromium, and / or aluminum, and the total amount of these metals may advantageously comprise at least 15% by weight of the alloy, for example 10-25% by weight chromium, 3-8% by weight aluminum, and up to 20% by weight nickel. The alloys may contain small or trace amounts of one or more metals such as manganese, copper, vanadium, titanium, etc. The surface of the metal substrate may be oxidized at high temperatures, for example 1000° C. or higher, to form an oxide layer on the surface of the substrate to improve the corrosion resistance of the alloy and promote adhesion of the washcoat layer to the metal surface.

[0039] Preferred 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.

[0040] Any suitable substrate may be used, such as a monolith flow-through substrate having a plurality of fine parallel gas flow passages extending from the inlet face to the outlet face of the substrate such that the flow passages are open to fluid flow. The flow passages, which are essentially straight passages from the inlet to the outlet, are defined by walls on which a catalytic material is coated as a washcoat such that gas flowing through the flow passages contacts the catalytic material. The flow passages in the monolith substrate are thin-walled channels of any suitable cross-sectional shape, such as trapezoidal, rectangular, square, sinusoidal, hexagonal, elliptical, circular, etc. Such structures have from about 60 to about 1200 or more gas inlet openings (i.e., "cells") per square inch of cross section (cpsi), more commonly about 300 to 900 cpsi. The wall thickness of the flow-through substrate may vary, but a typical range is 0.002 to 0.1 inches. A typical commercially available flow-through substrate is a cordierite substrate having a wall thickness of 400 cpsi and 6 mils, or 600 cpsi and 4 mils. However, it will be understood that the invention is not limited to a particular substrate type, material, or shape. In an alternative embodiment, the substrate may be a wall-flow substrate, with each flow passage blocked with a non-porous plug at one end of the substrate body, with the flow passages being blocked at alternating opposing end faces. This requires that the gas flow through the porous walls of the wall-flow substrate to reach the outlet. Such monolith substrates can contain up to about 700 cpsi or more, for example, about 100 to 400 cpsi, more typically about 200 to about 300 cpsi. The cross-sectional geometry of the cells can vary as described above. Wall-flow substrates typically have wall thicknesses of 0.002 to 0.1 inches. Representative commercially available wall-flow substrates are constructed from porous cordierite, examples of which have wall thicknesses of 200 cpsi and 10 mils or 300 cpsi and 8 mils, and wall porosities of 45 to 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 any particular substrate type, material, or shape.It should be noted that if the substrate is a wall-flow substrate, the catalyst composition, in addition to being disposed on the surface of the wall, can penetrate into the pore structure of the porous wall (i.e., partially or completely block 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.

[0041] 2A and 2B show an exemplary substrate 2 in the form of a flow-through substrate coated with a washcoat composition described herein. Referring to FIG. 2A, the exemplary substrate 2 has a cylindrical shape, with a cylindrical outer surface 4, an upstream end surface 6, and a corresponding downstream end surface 8 that is identical to end surface 6. The substrate 2 has a plurality of fine, parallel gas flow passages 10 formed therein. As can be seen in FIG. 2B, the flow passages 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 flow passages 10 are unobstructed to allow a fluid, e.g., gas flow, to flow longitudinally through the substrate 2 via the gas flow passages 10. As can be more easily seen in FIG. 2B, the walls 12 are sized and configured such that the gas flow passages 10 have a substantially regular polygonal shape. As shown, the washcoat composition can be applied in multiple separate layers, if desired. In the illustrated embodiment, the washcoat comprises a first separate washcoat layer 14 adhered to the wall 12 of the substrate member and a second separate washcoat layer 16 coated over the first washcoat layer 14. In one embodiment, the presently claimed invention may also be practiced with more than one washcoat layer (e.g., three or four) and is not limited to the two layer embodiment shown.

[0042] FIG. 3 shows an exemplary substrate 2 in the form of a wall-flow filter substrate coated with a washcoat composition described herein. As can be seen in FIG. 3, the exemplary substrate 2 has a plurality of passages 52. The passages are tubularly surrounded by the inner wall 53 of the filter substrate. The substrate has an inlet end 54 and an outlet end 56. Alternate passages are blocked at the inlet end with inlet plugs 58 and at the outlet end with outlet plugs 60 to form an opposing checkerboard pattern at the inlet 54 and outlet 56. Gas flow 62 enters through the unblocked channel inlet 64, is stopped by the outlet plugs 60, and diffuses through the channel wall 53 (which is porous) to the outlet side 66. The gas cannot return to the inlet side of the wall due to the inlet plugs 58. The porous wall-flow filters used in the present invention are catalyzed in that the walls of the element have one or more catalytic materials thereon or contain one or more catalytic materials therein. The catalytic material may be present only on the inlet side, only on the outlet side, on both the inlet and outlet sides of the element walls, or the walls themselves may consist entirely or in part of the catalytic material. The present invention includes the use of one or more layers of catalytic material on the inlet and / or outlet walls of the element.

[0043] Washcoat on substrate: Bottom Coat: The bottom washcoat is deposited on the substrate. Preferably, the bottom washcoat covers 90-100% of the surface of the substrate. More preferably, the bottom washcoat covers 95-100% of the surface of the substrate, and even more preferably, the bottom washcoat 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.

[0044] The bottom washcoat has a zoned configuration, which includes a first zone and a second zone.

[0045] Preferably, the first and second zones together cover 50-100% of the length of the substrate, more preferably, the first and second zones together cover 90-100% of the length of the substrate, and even more preferably, the first and second zones together cover the entire length of the substrate.

[0046] Preferably, the first zone covers 10-90% of the total length of the substrate from the inlet, and the second zone covers 90-10% of the total length of the substrate from the outlet, but the first and second zones together cover 20-100% of the substrate length. More preferably, the first zone covers 20-80% of the total length of the substrate from the inlet, and the second zone covers 80-20% of the total length of the substrate from the outlet, but the first and second zones together cover 40-100% of the substrate length. Even more preferably, the first zone covers 30-70% of the total length of the substrate from the inlet, and the second zone covers 70-30% of the total length of the substrate from the outlet, but the first and second zones together cover 60-100% of the substrate length. Even more preferably, the first zone covers 40-50% of the total length of the substrate from the inlet and the second zone covers 50-40% of the total length of the substrate from the outlet, but the first and second zones together cover 80-100% of the substrate length.

[0047] First Zone in the Bottom Coat: The first zone in the bottom washcoat comprises palladium supported on ceria-zirconia mixed oxide or alumina or both. Throughout this application, the term "supported" has its general meaning in the field of heterogeneous catalysis. In general, the term "supported" refers to a catalytically active species or its respective precursor attached to a support material. The support material may be inert or may participate in the catalytic reaction. Typical supported catalysts are prepared by impregnation or co-precipitation methods and optionally subsequent calcination.

[0048] The amount of ceria-zirconia mixed oxide in the first zone is in the range of 10-90 wt% based on the total weight of the washcoat. Preferably, the amount of ceria-zirconia mixed oxide in the first zone is in the range of 20-80 wt% based on the total weight of the washcoat. More preferably, the amount of ceria-zirconia mixed oxide in the first zone is in the range of 30-70 wt% based on the total weight of the washcoat.

[0049] The ceria-zirconia mixed oxide preferably comprises ceria, calculated as CeO2 in an amount of about 20-50 wt.% based on the total weight of the ceria-zirconia mixed oxide present in the first zone, and zirconia, calculated as ZrO2 in an amount of about 50-80 wt.% based on the total weight of the ceria-zirconia mixed oxide present in the first zone. More preferably, the ceria-zirconia mixed oxide comprises ceria, calculated as CeO2 in an amount of about 30-50 wt.% based on the total weight of the ceria-zirconia mixed oxide present in the first zone, and zirconia, calculated as ZrO2 in an amount of about 50-70 wt.% based on the total weight of the ceria-zirconia mixed oxide present in the first zone.

[0050] The amount of alumina in the first zone is preferably in the range of 5.0 to 90 wt % based on the total weight of the washcoat. More preferably, the amount of alumina in the first zone is in the range of 10 to 80 wt % based on the total weight of the washcoat. More preferably, the amount of alumina in the first zone is in the range of 10 to 70 wt % based on the total weight of the washcoat.

[0051] In the first zone, palladium is supported on a ceria-zirconia mixed oxide. The amount of palladium in the first zone is preferably 50-100 wt% based on the total weight of palladium in the washcoat. Preferably, the amount of palladium in the first zone is 75-100 wt% based on the total weight of palladium in the washcoat. More preferably, the amount of palladium in the first zone is 80-100 wt% based on the total weight of palladium in the washcoat.

[0052] Alternatively, palladium is supported on alumina. Furthermore, palladium can be supported on both support materials, i.e., ceria-zirconia mixed oxide and alumina. The amount of palladium distributed on the ceria-zirconia mixed oxide is 40-80% of the total palladium present in the first zone, and the amount of palladium distributed on the alumina is 20-60% of the total palladium present in the first zone. Preferably, palladium is evenly distributed on the ceria-zirconia mixed oxide and alumina.

[0053] Preferably, the first zone further comprises platinum supported on the ceria-alumina composite. The amount of platinum in the first zone is preferably 0.01-50 wt% based on the total weight of platinum in the washcoat. More preferably, the amount of platinum in the first zone is 1.0-30 wt% based on the total weight of platinum in the washcoat. More preferably, the amount of platinum in the first zone is 5.0-25 wt% based on the total weight of platinum in the washcoat.

[0054] Preferably, the amount of ceria-alumina composite in the first zone is in the range of 1.0 to 80 wt % based on the total weight of the washcoat. More preferably, the amount of ceria-alumina composite in the first zone is in the range of 10 to 70 wt % based on the total weight of the washcoat. More preferably, the amount of ceria-alumina composite in the first zone is in the range of 10 to 50 wt % based on the total weight of the washcoat.

[0055] Preferably, the amount of ceria in the ceria-alumina composite calculated as CeO2 is 1.0-50 wt% based on the total weight of the ceria-alumina composite. More preferably, the amount of ceria in the ceria-alumina composite calculated as CeO2 is 5.0-50 wt% based on the total weight of the ceria-alumina composite. More preferably, the amount of ceria in the ceria-alumina composite calculated as CeO2 is 5.0-30 wt% based on the total weight of the ceria-alumina composite. Even more preferably, the amount of ceria in the ceria-alumina composite calculated as CeO2 is 8.0-20 wt% based on the total weight of the ceria-alumina composite.

[0056] Second zone in the bottom coat: The second zone in the bottom washcoat comprises platinum supported on a ceria-alumina composite. Preferably, the amount of platinum supported on the ceria-alumina composite is 50-100 wt % based on the total weight of platinum in the washcoat. Preferably, the amount of platinum supported on the ceria-alumina composite is 75-100 wt % based on the total weight of platinum in the washcoat.

[0057] Preferably, the amount of ceria-alumina composite in the second zone is in the range of 1.0 to 80 wt % based on the total weight of the washcoat. More preferably, the amount of ceria-alumina composite in the second zone is in the range of 10 to 70 wt % based on the total weight of the washcoat. More preferably, the amount of ceria-alumina composite in the second zone is in the range of 10 to 50 wt % based on the total weight of the washcoat.

[0058] Preferably, the amount of ceria in the ceria-alumina composite calculated as CeO2 is 1.0-50 wt% based on the total weight of the ceria-alumina composite. More preferably, the amount of ceria in the ceria-alumina composite calculated as CeO2 is 5.0-50 wt% based on the total weight of the ceria-alumina composite. More preferably, the amount of ceria in the ceria-alumina composite calculated as CeO2 is 5.0-30 wt% based on the total weight of the ceria-alumina composite. Even more preferably, the amount of ceria in the ceria-alumina composite calculated as CeO2 is 8.0-20 wt% based on the total weight of the ceria-alumina composite.

[0059] The second zone in the bottom washcoat further comprises palladium supported on a ceria-zirconia mixed oxide. Preferably, the second zone comprises 0.01 to 50 wt. % palladium supported on a ceria-zirconia mixed oxide, based on the total weight of palladium in the washcoat. More preferably, the second zone comprises 1.0 to 30 wt. % palladium supported on a ceria-zirconia mixed oxide, based on the total weight of palladium in the washcoat. More preferably, the second zone comprises 5.0 to 25 wt. % palladium supported on a ceria-zirconia mixed oxide, based on the total weight of palladium in the washcoat.

[0060] Preferably, the amount of ceria-zirconia mixed oxide in the second zone is in the range of 10-90 wt.% based on the total weight of the washcoat. More preferably, the amount of ceria-zirconia mixed oxide in the second zone is in the range of 20-80 wt.% based on the total weight of the washcoat. More preferably, the amount of ceria-zirconia mixed oxide in the second zone is in the range of 30-70 wt.% based on the total weight of the washcoat.

[0061] Preferably, the ceria-zirconia mixed oxide comprises ceria, calculated as CeO2 in an amount of about 20-50 wt.% based on the total weight of the ceria-zirconia mixed oxide, and zirconia, calculated as ZrO2 in an amount of about 50-80 wt.% based on the total weight of the ceria-zirconia mixed oxide. More preferably, the ceria-zirconia mixed oxide comprises ceria, calculated as CeO2 in an amount of about 30-50 wt.% based on the total weight of the ceria-zirconia mixed oxide, and zirconia, calculated as ZrO2 in an amount of about 50-70 wt.% based on the total weight of the ceria-zirconia mixed oxide.

[0062] Preferably, the total amount of ceria-zirconia mixed oxide in the first zone is equal to the total amount of ceria-zirconia mixed oxide in the second zone. That is, the weight ratio of the ceria-zirconia mixed oxide in the first zone to the ceria-zirconia mixed oxide in the second zone is 1:1. More preferably, the total amount of ceria-zirconia mixed oxide in the first zone is greater than the total amount of ceria-zirconia mixed oxide in the second zone. More preferably, the total amount of ceria-zirconia in the first zone is at least 1.1-1.5 times greater than the total amount of ceria-zirconia in the second zone. That is, the weight ratio of the ceria-zirconia mixed oxide in the first zone to the ceria-zirconia mixed oxide in the second zone is 1.1:1.0-1.5:1. With increasing ceria-zirconia (CZO) loading and Pd-rich inlet zone, improved NMHC performance is observed. These findings demonstrated the feasibility of using a Pd-rich zoned washcoat structure and OSC boost in the inlet zone to achieve 50% replacement of Pd with Pt.

[0063] Top Wash Coat: The top washcoat is deposited on the bottom coat. Preferably, the top washcoat covers 10-100% of the surface of the bottom coat. Preferably, the top washcoat covers 50-100% of the surface of the substrate, more preferably, the top washcoat covers 90-100% of the surface of the substrate, and even more preferably, the top washcoat covers the entire accessible surface of the substrate.

[0064] The top washcoat comprises rhodium supported on alumina or ceria-alumina composite. The alumina is preferably selected from alumina, lanthana-alumina, titania-alumina, ceria-zirconia-alumina, zirconia-alumina, lanthana-zirconia-alumina, baria-alumina, baria-lanthana-alumina, baria-lanthana-neodymia-alumina, or any combination thereof. The alumina may be doped with a dopant selected from barium, lanthana, zirconia, neodymian, yttria, or titania, the amount of the dopant being 1.0 to 30 wt % based on the total weight of the alumina and the dopant.

[0065] The amount of alumina in the top washcoat is preferably 1.0 to 80 wt % based on the total weight of the washcoat, more preferably 5.0 to 70 wt % based on the total weight of the washcoat, and more preferably 5.0 to 50 wt % based on the total weight of the washcoat.

[0066] The amount of ceria-alumina composite in the top washcoat is preferably in the range of 1.0-80 wt% based on the total weight of the washcoat. Preferably, the amount of ceria-alumina composite in the top washcoat is in the range of 10-70 wt% based on the total weight of the washcoat. More preferably, the amount of ceria-alumina composite in the top washcoat is in the range of 10-50 wt% based on the total weight of the washcoat. Preferably, the amount of ceria calculated as CeO2 in the ceria-alumina composite is 1.0-50 wt% based on the total weight of the ceria-alumina composite. More preferably, the amount of ceria calculated as CeO2 in the ceria-alumina composite is 5.0-50 wt% based on the total weight of the ceria-alumina composite. More preferably, the amount of ceria calculated as CeO2 in the ceria-alumina composite is 5.0-30 wt% based on the total weight of the ceria-alumina composite. Even more preferably, the amount of ceria, calculated as CeO2, in the ceria-alumina composite is from 8.0 to 20 wt. %, based on the total weight of the ceria-alumina composite.

[0067] The top washcoat and / or the bottom washcoat further comprise one or more promoters. As used herein, the term "promoter" refers to a component that is intentionally added to the support material to increase the activity of the catalyst compared to a catalyst that does not have the intentionally added promoter. Exemplary promoters include barium oxide or strontium oxide.

[0068] In addition, the top washcoat and / or bottom washcoat may further contain a binder in the form of alumina, colloidal alumina, silica, zirconium acetate, colloidal zirconia, or zirconium hydroxide, an associative thickener, and / or a surfactant, including anionic, cationic, nonionic, or amphoteric surfactants. Other exemplary binders include boehmite, gamma-alumina, or delta / theta alumina, as well as silica sol. When present, the binder is typically used in an amount of about 1.0 to 5.0 wt.% of the total weight of the washcoat. Alumina used as a binder is considered separate from alumina used as a support material.

[0069] Preferably, the amount of palladium is in the range of 0.02 to 2 wt % based on the total weight of the washcoat. More preferably, the amount of palladium is in the range of 0.05 to 1.5 wt % based on the total weight of the washcoat. More preferably, the amount of palladium is in the range of 0.05 to 1.0 wt % based on the total weight of the washcoat. Preferably, the amount of platinum is in the range of 0.02 to 2 wt % based on the total weight of the washcoat. More preferably, the amount of platinum is in the range of 0.05 to 1.5 wt % based on the total weight of the washcoat. More preferably, the amount of platinum is in the range of 0.05 to 1.0 wt % based on the total weight of the washcoat.

[0070] Preferably, the amount of rhodium is in the range of 0.01 to 0.5 wt% based on the total weight of the washcoat. More preferably, the amount of rhodium is in the range of 0.05 to 0.5 wt% based on the total weight of the washcoat. More preferably, the amount of rhodium is in the range of 0.05 to 0.3 wt% based on the total weight of the washcoat.

[0071] The weight ratio of palladium to platinum in the catalytic article is 9:1 to 1:13. Preferably, the weight ratio of palladium to platinum in the catalytic article is 3:1 to 1:1. The weight ratio of rhodium to palladium is 1:100 to 1:3. The weight ratio of rhodium to platinum is 1:100 to 1:3.

[0072] Preparation of the catalytic article: In another aspect of the present invention, a process for preparing the catalytic article described herein above is also provided. The process includes preparing a bottom washcoat including a first zone and a second zone, and a top washcoat. The first zone is obtained by preparing a first slurry including palladium supported on a ceria-zirconia mixed oxide or alumina or both, and coating the first slurry on a first portion of the substrate. The second zone is obtained by preparing a second slurry including platinum supported on a ceria-alumina composite, and coating the second slurry on a second portion of the substrate. The top washcoat is prepared by depositing a third slurry including rhodium supported on alumina or a ceria-alumina composite on the bottom coat. In a next step, the substrate is subjected to calcination at a temperature in the range of 400-700° C. The preparation of the catalytic article includes impregnating a support material in particulate form with an active metal solution, such as a palladium, platinum and / or rhodium precursor solution. As used herein, "impregnated" or "impregnation" refers to the penetration of a catalytic material into the porous structure of a support material. Techniques used to carry out the impregnation or slurry preparation include the incipient wetness technique (A), the co-precipitation technique (B), and the co-impregnation technique (C).

[0073] The synthesis of heterogeneous materials, i.e. catalysts, generally uses the incipient wetness impregnation technique, also called capillary impregnation or dry impregnation. Typically, metal precursors are dissolved in an aqueous or organic solution, and then the metal-containing solution is added to a catalyst support that contains the same pore volume as the volume of the added solution. Capillary action draws the solution into the pores of the support. Solution added beyond the support pore volume changes the solution transport from a capillary action process to a much slower diffusion process. The catalyst is dried and calcined to remove the volatile components in the solution and deposit the metal on the surface of the catalyst support. The concentration profile of the impregnated material depends on the mass transfer conditions in the pores during impregnation and drying.

[0074] The support particles are typically dry enough to absorb substantially all of the solution to form a wet solid. Typically, an aqueous solution of a water-soluble compound or complex of the active metal is utilized, such as rhodium chloride, rhodium nitrate (e.g., Ru(N0)3 and its salts), rhodium acetate, or combinations thereof where rhodium is the active metal, and palladium nitrate, palladium tetraamine, palladium acetate, or combinations thereof where palladium is the active metal. After treating the support particles with the active metal solution, the particles are dried, such as by heat treating the particles at an elevated temperature (e.g., 100-150°C) for a period of time (e.g., 1-3 hours), and then calcined to convert the active metal to a more catalytically active form. An exemplary calcination process includes heat treating in air at a temperature of about 400-550°C for 10 minutes to 3 hours. The above process may be repeated as necessary to achieve the desired level of active metal impregnation.

[0075] Substrate Coating: The catalyst composition is typically prepared in the form of catalyst particles as described above. To coat a catalyst substrate, such as a honeycomb-type substrate, these catalyst particles are mixed with water to form a slurry. In addition to the catalyst particles, the slurry may optionally contain a binder in the form of alumina, silica, zirconium acetate, colloidal zirconia, or zirconium hydroxide, an associative thickener, and / or a surfactant, including anionic, cationic, nonionic, or amphoteric surfactants. Other exemplary binders include boehmite, gamma-alumina, or delta / theta alumina, as well as silica sol. When present, the binder is typically used in an amount of about 1-5% by weight of the total washcoat loading. Addition of acidic or basic species to the slurry is made to adjust the pH accordingly. For example, in some embodiments, the pH of the slurry is adjusted by the addition of ammonium hydroxide, aqueous nitric acid, or acetic acid. A typical pH range for the slurry is about 3-12. The slurry can be milled to reduce particle size and facilitate particle mixing. Milling may be accomplished in a ball mill, continuous mill, or other similar equipment, and the solids content of the slurry may be, for example, about 20-60% by weight, more specifically about 20-40% by weight. In one embodiment, the milled slurry has a D of about 10 to about 40 micrometers, preferably 10 to about 30 micrometers, and more preferably about 10 to about 15 micrometers. 90 Characterized by particle size. D 90 is determined using a dedicated particle size analyzer. The instrument used in this example uses laser diffraction to measure particle size in small volumes of slurry. D is typically measured in micrometers. 90 means that 90% of the particle population have a diameter less than that value.

[0076] The slurry is coated onto the catalytic substrate using any washcoat technique known in the art. For example, the catalytic substrate is dipped into or otherwise coated with the slurry one or more times. The coated substrate is then dried at an elevated temperature (e.g., 100-150° C.) for a period of time (e.g., 10 minutes to 3 hours) and then calcined by heating, for example, at 400-700° C., typically for about 10 minutes to about 3 hours. After drying and calcination, the final washcoat coating layer is considered to be essentially solvent-free.

[0077] After calcination, the catalyst loading obtained by the washcoat technique described above can be determined by calculating the difference between the coated and uncoated weights of the substrate. As will be apparent to those skilled in the art, the catalyst loading can be altered by varying the slurry rheology. In addition, the coating / drying / calcining process to produce a washcoat may be repeated as necessary to build up the coating to a desired loading level or thickness, meaning that more than one washcoat may be applied.

[0078] The coated substrate may be aged by subjecting it to a heat treatment. For example, aging may be performed at a temperature of about 850° C. to about 1050° C. in the presence of steam for 50 to 300 hours under gasoline engine exhaust conditions. Thus, in accordance with the present invention, an aged catalyst article is provided. Effective support materials such as ceria-alumina composites retain a high percentage of their pore volume (e.g., about 50 to 100%) upon aging (e.g., aging at about 850° C. to about 1050° C. in the presence of steam for about 5 to 300 hours).

[0079] Emissions Treatment System: In another aspect of the invention, there is also provided an exhaust gas treatment system for an internal combustion engine, the system including the catalytic article described herein above. In one example, the system includes a catalytic article according to the presently claimed invention and an additional platinum group metal-based three-way conversion (TWC) catalytic article. The catalytic article of the invention may be located in a close-coupled position. A close-coupled catalyst is located close to the engine to allow the reaction temperature to be reached as quickly as possible. Typically, a close-coupled catalyst is located within 3 feet of the engine, more specifically within 1 foot, and even more specifically less than 6 inches from the engine. A close-coupled catalyst is often mounted directly on the exhaust gas manifold. Due to its close proximity to the engine, the close-coupled catalyst needs to be stable at high temperatures. The catalytic article of the invention can also be used as part of an integrated exhaust system that includes one or more additional components for treating exhaust gas emissions. For example, an exhaust system, also known as an emission treatment system, may further include a close-coupled TWC catalyst, an underfloor TWC catalyst, a catalysed soot filter (CSF) component, and / or a selective catalytic reduction (SCR) catalyst article. The foregoing list of components is merely illustrative and should not be construed as limiting the scope of the invention.

[0080] In another aspect of the invention, there is provided a method of treating a gaseous exhaust stream containing hydrocarbons, carbon monoxide, and nitrogen oxides, comprising contacting the exhaust stream with a catalytic article according to the invention or an exhaust gas treatment system according to the invention. The invention also provides a method of reducing the levels of hydrocarbons, carbon monoxide, and nitrogen oxides in a gaseous exhaust stream, comprising contacting the gaseous exhaust stream with a catalytic article according to the invention or an exhaust gas treatment system according to the invention to reduce the levels of hydrocarbons, carbon monoxide, and nitrogen oxides in the exhaust gas.

[0081] In another aspect of the invention, there is provided the use of a catalytic article or exhaust gas treatment system according to the presently claimed invention for purifying a gaseous exhaust stream containing hydrocarbons, carbon monoxide, and nitrogen oxides.

[0082] The invention is further described by the following embodiments, the features of each embodiment may be combined with any of the other embodiments where appropriate and practical.

[0083] EMBODIMENT 1 The invention claimed herein includes a substrate, a bottom washcoat deposited on the substrate, and a top washcoat deposited on the bottom washcoat. the bottom washcoat comprises a zoned configuration; the zoned configuration comprises a first zone and a second zone, the first zone comprising palladium supported on a ceria-zirconia mixed oxide or alumina or both; the second zone comprises platinum supported on a ceria-alumina composite; A catalyst article is provided in which the top washcoat comprises rhodium supported on alumina or a ceria-alumina composite.

[0084] EMBODIMENT 2 A catalytic article according to the presently claimed invention, wherein the second zone further comprises palladium supported on a ceria-zirconia mixed oxide and the top washcoat comprises rhodium supported on a ceria-alumina composite.

[0085] EMBODIMENT 3 A catalytic article according to the presently claimed invention, wherein the first zone further comprises platinum supported on a ceria-alumina composite and the second zone further comprises palladium supported on a ceria-zirconia mixed oxide.

[0086] EMBODIMENT 4 A catalyst article according to the presently claimed invention, wherein a first zone comprises palladium supported on a ceria-zirconia mixed oxide or alumina or both, a second zone comprises platinum supported on a ceria-alumina composite, and a top washcoat comprises rhodium supported on alumina or a ceria-alumina composite and platinum supported on a ceria-alumina composite.

[0087] EMBODIMENT 5 A catalytic article according to the presently claimed invention, wherein a first zone comprises palladium supported on each of ceria-zirconia mixed oxide and alumina.

[0088] EMBODIMENT 6 A catalyst article according to the invention claimed herein, wherein the first zone covers 10-90% of the total length of the substrate from the inlet, the second zone covers 10-90% of the total length of the substrate from the outlet, and the top washcoat covers 10-100% of the total length of the bottom washcoat from the inlet.

[0089] EMBODIMENT 7 A catalyst article according to the presently claimed invention, wherein the first zone covers 30-50% of the total length of the substrate from the inlet and the second zone covers 50-70% of the total length of the substrate from the outlet.

[0090] EMBODIMENT 8 A catalytic article according to the presently claimed invention, wherein the amount of ceria-zirconia mixed oxide in the first zone is greater than the amount of ceria-zirconia mixed oxide in the second zone.

[0091] EMBODIMENT 9 Catalyst article according to the presently claimed invention, wherein the weight ratio of the ceria-zirconia mixed oxide in the first zone to the ceria-zirconia mixed oxide in the second zone is from 1.1:1.0 to 1.5:1.

[0092] EMBODIMENT 10 Catalyst article according to the present invention as claimed in the present application, wherein the alumina present in the first zone and / or the top washcoat is doped with a dopant selected from barium, lanthana, zirconia, neodymium, yttria, or titania, the amount of said dopant being 1.0-30 wt. % based on the total weight of the alumina and the dopant.

[0093] EMBODIMENT 11 A catalytic article according to the presently claimed invention, wherein the alumina present in the first zone and / or the top washcoat is selected from alumina, lanthana-alumina, titania-alumina, baria-alumina, baria-lanthana-alumina, baria-lanthana-neodymia-alumina, or any combination thereof.

[0094] EMBODIMENT 12 Catalyst articles according to the presently claimed invention, wherein the amount of ceria in the ceria-alumina composite present in the top and / or bottom washcoat is from 5.0 to 30 wt. %, based on the total weight of the ceria-alumina composite.

[0095] EMBODIMENT 13 1. A catalyst article according to the presently claimed invention, wherein a first zone comprises palladium supported on a ceria-zirconia mixed oxide or alumina or both in an amount of 50-100% by weight based on the total weight of palladium in the washcoat, and a second zone comprises platinum supported on a ceria-alumina composite in an amount of 50-100% by weight based on the total weight of platinum in the washcoat, the second zone further comprises palladium supported on a ceria-zirconia mixed oxide in an amount of 0-50% by weight based on the total weight of palladium in the washcoat, and the first zone further comprises platinum supported on a ceria-alumina composite in an amount of 0-50% by weight based on the total weight of platinum in the washcoat.

[0096] EMBODIMENT 14 Catalyst articles according to the presently claimed invention, wherein a first zone comprises palladium supported on a ceria-zirconia mixed oxide or alumina or both in an amount of 75-100 wt % based on the total weight of palladium in the washcoat, and a second zone comprises platinum supported on a ceria-alumina composite in an amount of 75-100 wt % based on the total weight of platinum in the washcoat.

[0097] EMBODIMENT 15 Catalyst articles according to the presently claimed invention, wherein the bottom washcoat comprises platinum supported on a ceria-alumina composite in an amount of 50-100 wt %, based on the total weight of platinum in the washcoat, and the top washcoat comprises platinum supported on a ceria-alumina composite in an amount of 0-50 wt %, based on the total weight of platinum in the washcoat.

[0098] EMBODIMENT 16 A catalytic article according to the presently claimed invention, wherein the amount of palladium is in the range of 0.02-2 wt.% based on the total weight of the washcoat, the amount of platinum is in the range of 0.02-2 wt.% based on the total weight of the washcoat, and the amount of rhodium is in the range of 0.01-0.5 wt.% based on the total weight of the washcoat.

[0099] EMBODIMENT 17 A catalyst article according to the present invention as claimed in the present application, wherein the weight ratio of palladium to platinum in the catalyst article is between 9:1 and 1:13.

[0100] EMBODIMENT 18 A catalyst article according to the present invention as claimed in the present application, wherein the weight ratio of palladium to platinum in the catalyst article is between 3:1 and 1:1.

[0101] EMBODIMENT 19 Catalyst articles according to the present invention as claimed in claim 1, wherein the ceria, calculated as CeO2 in the ceria-alumina composite present in the top and / or bottom washcoat, is 1.0-50 wt. % based on the total weight of the ceria-alumina composite, preferably the ceria, calculated as CeO2 in the ceria-alumina composite present in the top and / or bottom washcoat, is 5.0-50 wt. % based on the total weight of the ceria-alumina composite, more preferably the ceria, calculated as CeO2 in the ceria-alumina composite present in the top and / or bottom washcoat, is 5-30 wt. % based on the total weight of the ceria-alumina composite, and even more preferably the ceria, calculated as CeO2 in the ceria-alumina composite present in the top and / or bottom washcoat, is 8-20 wt. % based on the total weight of the ceria-alumina composite.

[0102] EMBODIMENT 20 Catalyst articles according to the presently claimed invention, wherein the ceria-zirconia mixed oxide comprises ceria, calculated as CeO2 in an amount of about 20 to 50 weight percent, based on the total weight of the ceria-zirconia mixed oxide, and zirconia, calculated as ZrO2 in an amount of about 40 to about 80 weight percent, based on the total weight of the ceria-zirconia mixed oxide.

[0103] EMBODIMENT 21 10. A catalytic article according to the presently claimed invention, wherein the ceria-zirconia mixed oxide comprises a dopant selected from lanthana, titania, hafnia, magnesia, calcia, strontia, baria, yttrium, hafnium, praseodymium, neodymium, or any combination thereof.

[0104] EMBODIMENT 22 A catalytic article according to the presently claimed invention, wherein the substrate is selected from a ceramic substrate, a metal substrate, a ceramic foam substrate, a polymeric foam substrate, or a woven fiber substrate.

[0105] EMBODIMENT 23 Catalyst articles according to the presently claimed invention, wherein the amount of ceria-zirconia mixed oxide is in the range of 10-90 wt % based on the total weight of the washcoat, the amount of alumina is in the range of 5.0-99 wt % based on the total weight of the washcoat, and the amount of ceria-alumina composite is in the range of 10-80 wt % based on the total weight of the washcoat.

[0106] Embodiment 24: 1. A catalyst article according to the present invention, comprising: a substrate; a bottom washcoat deposited on the substrate; and a top washcoat deposited on the bottom washcoat, the bottom washcoat comprising a zoned configuration, the zoned configuration comprising a first zone and a second zone, the first zone covering 30-50% of the substrate length from an inlet and the second zone covering 50-70% of the substrate length from an outlet, the first zone comprising palladium impregnated on alumina and a ceria-zirconia mixed oxide in an amount of 75-100% by weight based on the total weight of palladium in the washcoat, the second zone comprising platinum impregnated on a ceria-alumina composite and palladium impregnated on a ceria-zirconia mixed oxide, the top washcoat comprising rhodium supported on a ceria-alumina composite, the weight ratio of palladium to platinum in the catalyst article being between 3:1 and 1:1.

[0107] Embodiment 25: A catalyst article comprising a substrate, a bottom washcoat deposited on the substrate, and a top washcoat deposited on the bottom washcoat, the bottom washcoat comprising a zoned configuration, the zoned configuration comprising a first zone and a second zone, the first zone covering 30-50% of the substrate length from an inlet, the second zone covering 50-70% of the substrate length from an outlet, the first zone comprising alumina and stabilized cerium in an amount of 75-100% by weight based on the total weight of palladium in the washcoat. the first zone comprises palladium impregnated on a stabilized ceria-zirconia mixed oxide, the second zone comprises platinum impregnated on a ceria-alumina composite and palladium impregnated on a stabilized ceria-zirconia mixed oxide, the top washcoat comprises rhodium supported on a ceria-alumina composite, the weight ratio of palladium to platinum in the catalytic article is from 3:1 to 1:1, and the amount of ceria-zirconia mixed oxide in the first zone is greater than the amount of ceria-zirconia mixed oxide in the second zone.

[0108] Embodiment 26: 1. A catalyst article comprising: a substrate; a bottom washcoat deposited on the substrate; and a top washcoat deposited on the bottom washcoat, the bottom washcoat comprising a zoned configuration, the zoned configuration comprising a first zone and a second zone, the first zone covering 30-50% of the substrate length from an inlet and the second zone covering 50-70% of the substrate length from an outlet; 1. A catalyst article, wherein the first zone is comprised of palladium impregnated on alumina and a stabilized ceria-zirconia mixed oxide in an amount of 75-100 wt. % based on the total weight of palladium in the washcoat, the second zone is comprised of platinum impregnated on a ceria-alumina composite and palladium impregnated on a stabilized ceria-zirconia mixed oxide, and the top washcoat is comprised of rhodium supported on a ceria-alumina composite.

[0109] Embodiment 27: A catalyst article comprising a substrate, a bottom washcoat deposited on the substrate, and a top washcoat deposited on the bottom washcoat, the bottom washcoat comprising a zoned configuration, the zoned configuration comprising a first zone and a second zone, the first zone covering 30-50% of the substrate length from an inlet, the second zone covering 50-70% of the substrate length from an outlet, the first zone comprising alumina and stabilized ceria in an amount of 75-100% by weight based on the total weight of palladium in the washcoat. a catalyst article comprising palladium impregnated on a stabilized ceria-zirconia mixed oxide, said second zone comprising platinum impregnated on a ceria-alumina composite and palladium impregnated on a stabilized ceria-zirconia mixed oxide, said top washcoat comprising rhodium supported on a ceria-alumina composite, said catalyst article having a weight ratio of palladium to platinum of from 3:1 to 1:1, and said amount of ceria-zirconia mixed oxide in said first zone being greater than said amount of ceria-zirconia mixed oxide in said second zone.

[0110] Embodiment 28: A catalyst article comprising a substrate, a bottom washcoat deposited on the substrate, and a top washcoat deposited on the bottom washcoat, the bottom washcoat comprising a zoned configuration, the zoned configuration comprising a first zone and a second zone, the first zone covering 30-50% of the substrate length from an inlet, the second zone covering 50-70% of the substrate length from an outlet, the first zone comprising alumina and stabilized ceria-zirconia in an amount of 75-100% by weight based on the total weight of palladium in the washcoat. the first zone comprises platinum impregnated on a stabilized ceria-zirconia mixed oxide, the second zone comprises platinum impregnated on a ceria-alumina composite and palladium impregnated on a stabilized ceria-zirconia mixed oxide, the top washcoat comprises rhodium and palladium supported on a ceria-alumina composite, the weight ratio of palladium to platinum in the catalytic article is from 3:1 to 1:1, and the amount of ceria-zirconia mixed oxide in the first zone is greater than the amount of ceria-zirconia mixed oxide in the second zone.

[0111] Aspects of the invention claimed herein will be more fully described by the following examples, which are provided to illustrate certain aspects of the invention and should not be construed as limiting thereof.

[0112] All catalyst articles were coated on cylindrical monolith cordierite substrates with dimensions of 4.66 inches in diameter and 3.81 inches in length, a cell density of 800 cpsi, and a wall thickness of 2.5 mils. The example washcoat structures are plotted in Figure 1. The designs and PGM assignments of the non-zoned reference and zoned catalyst articles are summarized in Tables 1 and 2, respectively.

[0113] [Table 1] * CZO: ceria-zirconia mixed oxide

[0114] [Table 2] * CZO: ceria-zirconia mixed oxide. Length: percentage of washcoat coverage as a function of substrate length.

[0115] Comparative example 1: 120g / ft 3 Preparation of a non-zoned bilayer Pd / Rh reference catalyst article (FIG. 1A) with a PGM loading of (Pt / Pd / Rh=0 / 118 / 2). Bottom layer: This layer is 118g / ft 3 PGM loading (Pt / Pd / Rh=0 / 118 / 0) covers 100% of the substrate length. 59g / ft 3 of Pd in ​​the form of palladium nitrate (50 wt. % of total Pd) was impregnated onto alumina, yielding 59 g / ft 3 of Pd in ​​the form of palladium nitrate (50 wt.% of total Pd) was impregnated onto a ceria-zirconia mixed oxide containing about 40 wt.% ceria. A slurry containing about 34.4 wt.% alumina, 49.6 wt.% ceria-zirconia mixed oxide, barium acetate giving 11.5 wt.% BaO, zirconium acetate giving 1.9 wt.% ZrO2, and 2.62 wt.% Pd was coated onto the substrate. The washcoat loading of the bottom layer was about 2.61 g / in after calcination at 550 °C in air for 1 hour. 3 It was. Top layer: This layer is 2g / ft 3 PGM loading (Pt / Pd / Rh=0 / 0 / 2) of 2g / ft covers 100% of the substrate length. 3 of Rh in the form of rhodium nitrate (100 wt.% of total Rh) was impregnated onto the alumina. A slurry mixture containing about 84.9 wt.% alumina, 15.0 wt.% ceria-zirconia mixed oxide having about 50 wt.% ceria, and 0.12 wt.% Rh was coated onto the bottom layer. The washcoat loading of the top layer was about 1.00 g / in after calcination at 550° C. in air for 1 hour. 3 It was.

[0116] Comparative example 2: 120g / ft 3Preparation of a non-zoned bilayer Pt / Pd / Rh reference catalyst article (FIG. 1B) with a PGM loading of (Pt / Pd / Rh=59 / 59 / 2). Bottom layer: This layer is 118g / ft 3 PGM loading (Pt / Pd / Rh=59 / 59 / 0) covers 100% of the substrate length. 59g / ft 3 of Pt (100 wt. % of total Pt) in the form of a platinum-amine complex was impregnated onto the alumina. 3 of Pd in ​​the form of palladium nitrate (100 wt. % of total Pd) was impregnated onto a ceria-zirconia mixed oxide containing about 40 wt. % ceria. A slurry containing about 33.1 wt. % alumina, 54.5 wt. % ceria-zirconia mixed oxide, barium acetate giving 7.8 wt. % BaO, zirconium acetate giving 1.9 wt. % ZrO2, 1.33 wt. % Pt, and 1.33 wt. % Pd was coated onto the substrate. The washcoat loading of the bottom layer was about 2.57 g / in after calcination at 550 °C in air for 1 hour. 3 It was. Top layer: This layer is 2g / ft 3 PGM loading (Pt / Pd / Rh=0 / 0 / 2) of 2g / ft covers 100% of the substrate length. 3 of Rh in the form of rhodium nitrate (100 wt.% of total Rh) was impregnated onto a ceria-alumina composite with about 10 wt.% ceria. A slurry mixture containing about 84.9 wt.% ceria-alumina, 15.0 wt.% of a ceria-zirconia mixed oxide with about 50 wt.% ceria, and 0.12 wt.% Rh was coated onto the bottom layer. The washcoat loading of the top layer was about 1.00 g / in after calcination at 550 °C in air for 1 hour. 3 It was.

[0117] Example 3: 120 g / ft 3 Preparation of a zoned bilayer Pt / Pd / Rh catalyst article (FIG. 1C) with a PGM loading of (Pt / Pd / Rh=29.5 / 88.5 / 2). Bottom layer inlet zone: This zone is 118g / ft 3PGM loading (Pt / Pd / Rh=0 / 118 / 0) covering 50% of the substrate length from the inlet to the middle. 59g / ft 3 of Pd in ​​the form of palladium nitrate (33.3 wt. % of total Pd) was impregnated onto alumina, yielding 59 g / ft 3 of Pd in ​​the form of palladium nitrate (33.3 wt.% of total Pd) was impregnated onto a ceria-zirconia mixed oxide containing about 40 wt.% ceria. A slurry containing about 33.1 wt.% alumina, 54.5 wt.% ceria-zirconia mixed oxide, barium acetate giving 7.8 wt.% BaO, zirconium acetate giving 1.9 wt.% ZrO2, and 2.66 wt.% Pd was coated onto the substrate. The washcoat loading in the inlet zone of the bottom layer was about 2.57 g / in after calcination at 550° C. in air for 1 hour. 3 It was. Bottom layer exit zone: This zone is 118g / ft 3 PGM loading (Pt / Pd / Rh=59 / 59 / 0) covers 50% of the substrate length from the exit to the middle. 59g / ft 3 of Pt in the form of a platinum-amine complex (100 wt. % of total Pt) was impregnated onto a ceria-alumina composite containing about 10 wt. % ceria. 3 of Pd in ​​the form of palladium nitrate (33.3 wt.% of total Pd) was impregnated onto a ceria-zirconia mixed oxide containing about 40 wt.% ceria. A slurry containing about 33.1 wt.% ceria-alumina composite, 54.5 wt.% ceria-zirconia mixed oxide, barium acetate yielding 7.8 wt.% BaO, colloidal alumina binder yielding 1.9 wt.% Al2O3, 1.33 wt.% Pt, and 1.33 wt.% Pd was coated onto the substrate. The washcoat loading in the exit zone of the bottom layer was about 2.57 g / in after calcination at 550 °C in air for 1 hour. 3 It was. Top layer: Same as the top layer of Example 2.

[0118] Example 4: 120 g / ft 3 Preparation of a zoned bilayer Pt / Pd / Rh catalyst article (FIG. 1D) with a PGM loading of (Pt / Pd / Rh=59 / 59 / 2). Bottom layer entrance zone: This zone is 106.2 g / ft 3 PGM loading (Pt / Pd / Rh=0 / 106.2 / 0) covers 50% of the substrate length from the inlet to the middle. 53.1g / ft 3 of Pd in ​​the form of palladium nitrate (45 wt. % of total Pd) was impregnated onto alumina, yielding 53.1 g / ft 3 of Pd in ​​the form of palladium nitrate (45 wt.% of total Pd) was impregnated onto a ceria-zirconia mixed oxide containing about 40 wt.% ceria. A slurry containing about 33.2 wt.% alumina, 54.7 wt.% ceria-zirconia mixed oxide, barium acetate giving 7.8 wt.% BaO, zirconium acetate giving 2.0 wt.% ZrO2, and 2.40 wt.% Pd was coated onto the substrate. The washcoat loading in the inlet zone of the bottom layer was about 2.56 g / in after calcination at 550° C. in air for 1 hour. 3 It was. Bottom layer exit zone: This zone is 129.8 g / ft 3 PGM loading (Pt / Pd / Rh=118 / 11.8 / 0) covers 50% of the substrate length from the exit to the middle. 118g / ft 3 of Pt in the form of a platinum-amine complex (100 wt. % of total Pt) was impregnated onto a ceria-alumina composite containing about 10 wt. % ceria. 3 of Pd in ​​the form of palladium nitrate (10 wt.% of total Pd) was impregnated onto a ceria-zirconia mixed oxide containing about 40 wt.% ceria. A slurry containing about 33.1 wt.% ceria-alumina composite, 54.5 wt.% ceria-zirconia mixed oxide, barium acetate yielding 7.8 wt.% BaO, colloidal alumina binder yielding 1.9 wt.% Al2O3, 2.65 wt.% Pt, and 0.26 wt.% Pd was coated onto the substrate. The washcoat loading in the exit zone of the bottom layer was about 2.58 g / in after calcination at 550 °C in air for 1 hour. 3 It was. Top layer: same as the top layer of Example 2.

[0119] Example 5: 120 g / ft3 (Pt / Pd / Rh=59 / 59 / 2) in the inlet zone of the bottom layer. ** The ceria-zirconia loading (shown as 3 Vs. 1.4 g / in in Example 4 3 1.) Preparation of a zoned bilayer Pt / Pd / Rh catalyst article (FIG. 1E). Bottom layer inlet zone: This zone has a 106.2 g / ft 3 PGM loading (Pt / Pd / Rh=0 / 106.2 / 0) covers 50% of the substrate length from the inlet to the middle. 53.1g / ft 3 of Pd in ​​the form of palladium nitrate (45 wt. % of total Pd) was impregnated onto alumina, yielding 53.1 g / ft 3 of Pd in ​​the form of palladium nitrate (45 wt.% of total Pd) was impregnated onto a ceria-zirconia mixed oxide containing about 40 wt.% ceria. A slurry containing about 25.4 wt.% alumina, 62.5 wt.% ceria-zirconia mixed oxide, barium acetate giving 7.8 wt.% BaO, zirconium acetate giving 2.0 wt.% ZrO2, and 2.40 wt.% Pd was coated onto the substrate. The washcoat loading in the inlet zone of the bottom layer was about 2.56 g / in after calcination at 550° C. in air for 1 hour. 3 It was. Bottom layer exit zone: same as bottom layer exit zone of Example 4. Top layer: same as top layer of Example 2.

[0120] Example 6: 120 g / ft 3 (Pt / Pd / Rh=59 / 59 / 2) in the inlet zone of the bottom layer. ** (shown as 1.8 g / in in Example 6) was further increased in ceria-zirconia loading. 3 Vs. 1.4 g / in in Example 4 3 ), in the outlet zone of the bottom layer ( * The ceria-zirconia loading (shown as 3 Vs. 1.4 g / in in Example 4 3) Preparation of a zoned bilayer Pt / Pd / Rh catalytic article (Figure 1F). Bottom layer entrance zone: This zone is 106.2 g / ft 3 PGM loading (Pt / Pd / Rh=0 / 106.2 / 0) covers 50% of the substrate length from the inlet to the middle. 53.1g / ft 3 of Pd in ​​the form of palladium nitrate (45 wt. % of total Pd) was impregnated onto alumina, yielding 53.1 g / ft 3 of Pd in ​​the form of palladium nitrate (45 wt.% of total Pd) was impregnated onto a ceria-zirconia mixed oxide containing about 40 wt.% ceria. A slurry containing about 17.6 wt.% alumina, 70.3 wt.% ceria-zirconia mixed oxide, barium acetate giving 7.8 wt.% BaO, zirconium acetate giving 2.0 wt.% ZrO2, and 2.40 wt.% Pd was coated onto the substrate. The washcoat loading in the inlet zone of the bottom layer was about 2.56 g / in after calcination at 550° C. in air for 1 hour. 3 It was. Bottom layer exit zone: This zone is 129.8 g / ft 3 PGM loading (Pt / Pd / Rh=118 / 11.8 / 0) covers 50% of the substrate length from the exit to the middle. 118g / ft 3 of Pt in the form of a platinum-amine complex (100 wt. % of total Pt) was impregnated onto a ceria-alumina composite containing about 10 wt. % ceria. 3 of Pd in ​​the form of palladium nitrate (10 wt.% of total Pd) was impregnated onto a ceria-zirconia mixed oxide containing about 40 wt.% ceria. A slurry containing about 40.8 wt.% ceria-alumina composite, 46.6 wt.% ceria-zirconia mixed oxide, barium acetate yielding 7.8 wt.% BaO, colloidal alumina binder yielding 1.9 wt.% Al2O3, 2.65 wt.% Pt, and 0.26 wt.% Pd was coated onto the substrate. The washcoat loading in the exit zone of the bottom layer was about 2.58 g / in after calcination at 550 °C in air for 1 hour. 3 It was. Top layer: same as the top layer of Example 2.

[0121] Example 7: 120 g / ft 3 (Pt / Pd / Rh=59 / 59 / 2) in the outlet zone of the bottom layer. * The ceria-zirconia loading (shown as 3 Vs. 1.4 g / in in Example 4 3 1G). Preparation of a zoned bilayer Pt / Pd / Rh catalyst article. Inlet zone of bottom layer: same as inlet zone of bottom layer in Example 4. Bottom layer exit zone: This zone is 129.8 g / ft 3 PGM loading (Pt / Pd / Rh=118 / 11.8 / 0) covers 50% of the substrate length from the exit to the middle. 118g / ft 3 of Pt in the form of a platinum-amine complex (100 wt. % of total Pt) was impregnated onto a ceria-alumina composite containing about 30 wt. % ceria. 3 of Pd in ​​the form of palladium nitrate (10 wt.% of total Pd) was impregnated onto a ceria-zirconia mixed oxide containing about 40 wt.% ceria. A slurry containing about 23.3 wt.% ceria-alumina composite, 64.1 wt.% ceria-zirconia mixed oxide, barium acetate yielding 7.8 wt.% BaO, colloidal alumina binder yielding 1.9 wt.% Al2O3, 2.65 wt.% Pt, and 0.26 wt.% Pd was coated onto the substrate. The washcoat loading in the exit zone of the bottom layer was about 2.58 g / in after calcination at 550 °C in air for 1 hour. 3 It was. Top layer: same as the top layer of Example 2.

[0122] Example 8: 120 g / ft 3 Preparation of a zoned bilayer Pt / Pd / Rh catalyst article (FIG. 1H) with a PGM loading of 1000 nm (Pt / Pd / Rh=59 / 59 / 2) and 25 wt % Pt allocated to the top layer. Bottom layer entrance zone: This zone is 106.2 g / ft 3 PGM loading (Pt / Pd / Rh=0 / 106.2 / 0) covers 50% of the substrate length from the inlet to the middle. 53.1g / ft3 of Pd in ​​the form of palladium nitrate (45 wt. % of total Pd) was impregnated onto alumina, yielding 53.1 g / ft 3 of Pd in ​​the form of palladium nitrate (45 wt.% of total Pd) was impregnated onto a ceria-zirconia mixed oxide containing about 40 wt.% ceria. A slurry containing about 26.0 wt.% alumina, 60.6 wt.% ceria-zirconia mixed oxide, barium acetate giving 8.7 wt.% BaO, zirconium acetate giving 2.2 wt.% ZrO2, and 2.66 wt.% Pd was coated onto the substrate. The washcoat loading in the inlet zone of the bottom layer was about 2.31 g / in after calcination at 550° C. in air for 1 hour. 3 It was. Bottom layer exit zone: This zone is 100.3 g / ft 3 PGM loading (Pt / Pd / Rh=88.5 / 11.8 / 0) covers 50% of the substrate length from the exit to the middle. 88.5g / ft 3 of Pt in the form of a platinum-amine complex (75 wt. % of total Pt) was impregnated onto a ceria-alumina composite containing about 10 wt. % ceria. 3 of Pd in ​​the form of palladium nitrate (10 wt.% of total Pd) was impregnated onto a ceria-zirconia mixed oxide containing about 40 wt.% ceria. A slurry containing about 26.0 wt.% ceria-alumina composite, 60.7 wt.% ceria-zirconia mixed oxide, barium acetate yielding 8.7 wt.% BaO, colloidal alumina binder yielding 2.2 wt.% Al2O3, 2.22 wt.% Pt, and 0.30 wt.% Pd was coated onto the substrate. The washcoat loading in the exit zone of the bottom layer was about 2.31 g / in after calcination at 550 °C in air for 1 hour. 3 It was. Top layer: This layer is 16.75g / ft 3 PGM loading (Pt / Pd / Rh=14.75 / 0 / 2) covers 100% of the substrate length. 14.75g / ft 3 Pt in the form of a platinum-amine complex (25 wt. % of total Pt) and 2 g / ft 3of Rh in the form of rhodium nitrate (100 wt.% of total Rh) was sequentially impregnated onto a ceria-alumina composite containing about 10 wt.% ceria. A slurry mixture containing about 88.3 wt.% ceria-alumina, 11.1 wt.% binder, 0.63 wt.% Pt, and 0.085 wt.% Rh was coated onto the bottom layer. The washcoat loading of the top layer was about 1.36 g / in after calcination at 550 °C in air for 1 h. 3 It was.

[0123] Example 9: 120 g / ft 3 Preparation of a zoned bilayer Pt / Pd / Rh catalyst article (FIG. 1I) with a PGM loading of (Pt / Pd / Rh=59 / 59 / 2). Bottom layer entrance zone: This zone is 165.2 g / ft 3 PGM loading (Pt / Pd / Rh=59 / 106.2 / 0) covers 50% of the substrate length from the inlet to the middle. 59g / ft 3 of Pt (50 wt. % of total Pt) in the form of a platinum-amine complex was impregnated onto a ceria-alumina composite containing about 10 wt. % ceria. 3 of Pd in ​​the form of palladium nitrate (90 wt.% of total Pd) was impregnated onto a ceria-zirconia mixed oxide containing about 40 wt.% ceria. A slurry containing about 32.7 wt.% ceria-alumina composite, 53.9 wt.% ceria-zirconia mixed oxide, barium acetate giving 7.7 wt.% BaO, zirconium acetate giving 1.9 wt.% ZrO, 1.31 wt.% Pt, and 2.36 wt.% Pd was coated onto the substrate. The washcoat loading in the inlet zone of the bottom layer was about 2.60 g / in after calcination at 550° C. in air for 1 hour. 3 It was. Bottom layer exit zone: This zone is 70.8 g / ft 3 PGM loading (Pt / Pd / Rh=59 / 11.8 / 0) covers 50% of the substrate length from the exit to the middle. 59g / ft 3 of Pt (50 wt. % of total Pt) in the form of a platinum-amine complex was impregnated onto a ceria-alumina composite containing about 10 wt. % ceria. 3of Pd in ​​the form of palladium nitrate (10 wt.% of total Pd) was impregnated onto a ceria-zirconia mixed oxide containing about 40 wt.% ceria. A slurry containing about 33.5 wt.% ceria-alumina composite, 55.1 wt.% ceria-zirconia mixed oxide, barium acetate yielding 7.9 wt.% BaO, colloidal alumina binder yielding 2.0 wt.% Al2O3, 1.34 wt.% Pt, and 0.27 wt.% Pd was coated onto the substrate. The washcoat loading in the exit zone of the bottom layer was about 2.54 g / in after calcination at 550 °C in air for 1 hour. 3 It was. Top layer: Same as the top layer of Example 2.

[0124] Example 10: 120 g / ft 3 Preparation of a zoned bilayer Pt / Pd / Rh catalyst article (FIG. 1J) with a PGM loading of (Pt / Pd / Rh=59 / 59 / 2). Bottom layer entrance zone: This zone is 110.6 g / ft 3 PGM loading (Pt / Pd / Rh=0 / 110.6 / 0) covers 40% of the substrate length from the inlet to the middle. 50.3g / ft 3 of Pd in ​​the form of palladium nitrate (37.5 wt. % of total Pd) was impregnated onto alumina, yielding 50.3 g / ft 3 of Pd in ​​the form of palladium nitrate (37.5 wt.% of total Pd) was impregnated onto a ceria-zirconia mixed oxide containing about 40 wt.% ceria. A slurry containing about 33.2 wt.% alumina, 54.6 wt.% ceria-zirconia mixed oxide, barium acetate giving 7.8 wt.% BaO, zirconium acetate giving 2.0 wt.% ZrO2, and 2.50 wt.% Pd was coated onto the substrate. The washcoat loading in the inlet zone of the bottom layer was about 2.56 g / in after calcination at 550° C. in air for 1 hour. 3 It was. Bottom layer exit zone: This zone is 122.9 g / ft 3 PGM loading (Pt / Pd / Rh=98.3 / 24.6 / 0) covers 60% of the substrate length from the exit to the middle. 98.3g / ft 3of Pt in the form of a platinum-amine complex (100 wt. % of total Pt) was impregnated onto a ceria-alumina composite containing about 10 wt. % ceria. 3 of Pd in ​​the form of palladium nitrate (25 wt.% of total Pd) was impregnated onto a ceria-zirconia mixed oxide containing about 40 wt.% ceria. A slurry containing about 33.1 wt.% ceria-alumina composite, 54.5 wt.% ceria-zirconia mixed oxide, barium acetate yielding 7.8 wt.% BaO, colloidal alumina binder yielding 1.9 wt.% Al2O3, 2.21 wt.% Pt, and 0.55 wt.% Pd was coated onto the substrate. The washcoat loading in the exit zone of the bottom layer was about 2.57 g / in after calcination at 550 °C in air for 1 hour. 3 It was. Top layer: same as the top layer of Example 2.

[0125] Aging and Testing The full-sized monolith catalyst articles of Examples 1-10 were mounted in a steel converter can and aged in a close-coupled position in the exhaust pipeline of a gasoline engine operating under an exothermic aging cycle. The aging period was 83 hours with a maximum bed temperature of about 945°C. The aged catalytic converters were tested in a close-coupled position in a 4-cylinder ULEV-50 gasoline vehicle with a 2L engine displacement operating under the US FTP-75 driving cycle, according to the certified procedures and tolerances. 3g / ft 3 A conventional TWC catalyst with a PGM loading (Rh only) of 10000 was used as a general purpose underfloor catalytic converter during testing.

[0126] Table 3 summarizes the tailpipe emissions of NMHC, NOx, and CO from the FTP-75 test. Examples 1 and 2 are reference non-zoned bi-layer catalyst articles.

[0127] [Table 3]

[0128] Example 2 used a significant amount of Pt, which resulted in worse NMHC, NOx, and CO emissions. The NMHC emissions of Example 2 increased by about 53% compared to Example 1. Examples 3 and 4 are zoned bilayer catalyst articles with 25% and 50% of the Pd substituted with Pt relative to the Pd / Rh-based Example 1. The zoned catalyst articles have 66.7%-90% of the total Pd concentrated in the inlet zone of the bottom layer covering 50% of the substrate length. All the Pt and the remaining Pd are allocated to the outlet zone of the bottom layer covering another 50% of the substrate length, with the Pt deposited on a ceria-alumina composite with about 10% ceria. All the Rh is allocated to the top layer covering the entire substrate length. Example 3 performed slightly better in all three emissions compared to Example 1, demonstrating the feasibility of using a zoned washcoat structure with a Pd-rich inlet zone to substitute 25% of the Pd with Pt. At the same 50% Pt substitution, Example 4 performed significantly better than Example 2. For example, NMHC emissions were reduced from 22.6 mg / mile for Example 4 to 16.1 mg / mile for Example 2. The improved tailpipe emissions performance, especially for NMHCs, is attributed to the zoned washcoat structure that allows the inlet zone to be Pd-rich. The Pd-rich inlet zone promoted NMHC light-off during engine cold start, while the Pt-containing outlet zone performed well under hot transient conditions. Compared to Example 4, Example 5 increases the CZO loading in the bottom layer inlet zone from 1.4 to 1.6 g / in while keeping the CZO loading in the outlet zone unchanged. 3 increased to.

[0129] Example 6 uses an inlet zone CZO loading of 1.8 g / in 3 At the same time, the CZO loading in the exit zone was increased from 1.4 to 1.2 g / in 3The Pd-rich inlet zone was reduced to 1.5 g / in. By increasing the CZO loading along with enriching the inlet zone, Examples 5 and 6 further improved NMHC performance compared to Example 4. The performance of Examples 5 and 6 was comparable or slightly better than that of the Pd / Rh-based Example 1. These findings demonstrated the feasibility of using a Pd-rich zoned washcoat structure in the inlet zone and an OSC boost to achieve 50% replacement of Pd with Pt. Example 7 maintained the same CZO loading in the inlet zone as Example 4, but increased the CZO loading in the outlet zone from 1.4 to 1.65 g / in. 3 NMHC emissions increased from 14.6 mg / mile in Example 6 to 18.4 mg / mile in Example 7. Thus, boosting OSCs in the Pd-rich inlet zone is preferable from a performance standpoint to boosting OSCs in the Pt-rich outlet zone. These findings are in good agreement with the fact that Pd generally activates CZO better than Pt. It is worth mentioning that in many examples, the trimetallic catalyst article of the present invention showed slightly to moderately better NOx performance compared to the Pd / Rh-based Example 1. Example 8 allocated 25% of the Pt to the top layer with Rh, while Example 9 allocated 50% of the Pt to the inlet zone of the bottom layer. Examples 8 and 9 performed as well as or better than Example 4, confirming that a portion of the Pt can be incorporated in the inlet zone and the top layer without adversely affecting the catalytic activity. Example 10 has an inlet zone with 40% coverage and an outlet zone with 60% coverage. The performance of Example 10 is comparable to that of Example 4, which has 50% coverage in the inlet zone and 50% coverage in the outlet zone.

[0130] Although the embodiments disclosed herein have been described with reference to specific embodiments, it should be understood that these embodiments are merely illustrative of the principles and applications of the invention claimed herein. It will be apparent to those skilled in the art that various modifications and variations can be made to the method and apparatus of the invention claimed herein without departing from the spirit and scope of the invention. Therefore, the invention claimed herein is intended to cover modifications and variations that come within the scope of the appended claims and their equivalents, and the above-described embodiments are presented for purposes of illustration and not limitation.

Claims

1. 1. A catalytic article comprising: a) a substrate; b) a bottom washcoat deposited on the substrate; and c) a top washcoat deposited on the bottom washcoat; the bottom washcoat comprises a zoned configuration; the zoned configuration includes a first zone and a second zone; the first zone comprises palladium supported on ceria-zirconia mixed oxide or alumina or both; the second zone comprises platinum supported on a ceria-alumina composite; A catalytic article wherein the top washcoat comprises rhodium supported on alumina or a ceria-alumina composite.

2. the second zone further comprises palladium supported on a ceria-zirconia mixed oxide; 10. The catalyst article of claim 1, wherein the top washcoat comprises rhodium supported on a ceria-alumina composite.

3. the first zone further comprises platinum supported on a ceria-alumina composite; 3. The catalytic article of claim 1 or 2, wherein the second zone further comprises palladium supported on a ceria-zirconia mixed oxide.

4. the first zone comprises palladium supported on the ceria-zirconia mixed oxide or the alumina, or both; the second zone comprises platinum supported on the ceria-alumina composite; 3. The catalyst article of claim 1 or 2, wherein the top washcoat comprises rhodium supported on the alumina or the ceria-alumina composite and platinum supported on the ceria-alumina composite.

5. 3. The catalytic article of claim 1, wherein the first zone comprises palladium supported on each of the ceria-zirconia mixed oxide and the alumina.

6. 3. The catalyst article of claim 1, wherein the first zone covers 10 to 90% of the total length of the substrate from the inlet, the second zone covers 10 to 90% of the total length of the substrate from the outlet, and the top washcoat covers 10 to 100% of the total length of the bottom washcoat from the inlet.

7. 3. The catalytic article of claim 1, wherein the first zone covers 30 to 50% of the total length of the substrate from the inlet, and the second zone covers 50 to 70% of the total length of the substrate from the outlet.

8. 3. The catalytic article of claim 1, wherein the amount of the ceria-zirconia mixed oxide in the first zone is greater than the amount of the ceria-zirconia mixed oxide in the second zone.

9. 3. The catalytic article of claim 1, wherein the weight ratio of the ceria-zirconia mixed oxide in the first zone to the ceria-zirconia mixed oxide in the second zone is from 1.1:1.0 to 1.5:

1.

10. 3. The catalyst article of claim 1 or 2, wherein the alumina present in the top washcoat and / or the bottom washcoat is doped with a dopant selected from barium, lanthana, zirconia, neodymian, yttria, or titania, and the amount of the dopant is 1.0 to 30 wt % based on the total weight of the alumina and the dopant.

11. 3. The catalytic article of claim 1 or 2, wherein the alumina present in the top washcoat and / or the bottom washcoat is selected from alumina, lanthana-alumina, titania-alumina, baria-alumina, baria-lanthana-alumina, baria-lanthana-neodymia-alumina, or any combination thereof.

12. 3. The catalyst article of claim 1, wherein the amount of ceria in the ceria-alumina composite present in the top washcoat and / or the bottom washcoat is 5.0 to 30 wt %, based on the total weight of the ceria-alumina composite.

13. the first zone comprises palladium supported on the ceria-zirconia mixed oxide or the alumina, or both, in an amount of 50 to 100 wt % based on the total weight of palladium in the washcoat, preferably the top washcoat and the bottom washcoat, and the second zone comprises platinum supported on the ceria-alumina composite in an amount of 50 to 100 wt % based on the total weight of platinum in the washcoat; the second zone further comprises palladium supported on the ceria-zirconia mixed oxide at 0 to 50 wt. % based on the total weight of palladium in the washcoat; 3. The catalyst article of claim 1, wherein the first zone further comprises platinum supported on the ceria-alumina composite in an amount of 0 to 50 wt %, based on the total weight of platinum in the washcoat.

14. 3. The catalytic article of claim 1, wherein the first zone comprises palladium supported on the ceria-zirconia mixed oxide or the alumina, or both, in an amount of 75 to 100 wt %, based on the total weight of palladium in the washcoat, and the second zone comprises platinum supported on the ceria-alumina composite in an amount of 75 to 100 wt %, based on the total weight of platinum in the washcoat.

15. 3. The catalyst article of claim 1, wherein the bottom washcoat comprises platinum supported on the ceria-alumina composite in an amount of 50 to 100 wt %, based on the total weight of platinum in the bottom washcoat, and the top washcoat comprises platinum supported on the ceria-alumina composite in an amount of 0 to 50 wt %, based on the total weight of platinum in the washcoat.

16. 3. The catalytic article of claim 1, wherein the amount of palladium is in the range of 0.02 to 2 wt % based on the total weight of the washcoat, the amount of platinum is in the range of 0.02 to 2 wt % based on the total weight of the washcoat, and the amount of rhodium is in the range of 0.01 to 0.5 wt % based on the total weight of the washcoat.

17. 3. The catalytic article of claim 1, wherein the weight ratio of palladium to platinum in the catalytic article is from 9:1 to 1:

13.

18. 3. The catalytic article of claim 1, wherein the weight ratio of palladium to platinum in the catalytic article is from 3:1 to 1:

1.

19. CeO of the ceria-alumina composite present in the top washcoat and / or the bottom washcoat ２ is 1.0 to 50 wt % based on the total weight of the ceria-alumina composite, and preferably CeO in the ceria-alumina composite present in the top washcoat and / or the bottom washcoat. ２ is 5.0 to 50 wt % based on the total weight of the ceria-alumina composite, and more preferably, the CeO in the ceria-alumina composite present in the top washcoat and / or the bottom washcoat is 5.0 to 50 wt % based on the total weight of the ceria-alumina composite. ２ is 5.0 to 30 wt % based on the total weight of the ceria-alumina composite, and even more preferably, the CeO in the ceria-alumina composite present in the top washcoat and / or the bottom washcoat is 5.0 to 30 wt % based on the total weight of the ceria-alumina composite, ２ 3. The catalyst article of claim 1, wherein the ceria, calculated as: is 8.0 to 20 wt. % based on the total weight of the ceria-alumina composite.

20. The ceria-zirconia mixed oxide present in the top washcoat and / or the bottom washcoat comprises CeO in an amount of about 20 to 50 wt. % based on the total weight of the ceria-zirconia mixed oxide. ２ and ZrO in an amount of about 40 to about 80 wt. % based on the total weight of said ceria-zirconia mixed oxide. ２ 3. The catalytic article of claim 1 or 2, comprising zirconia calculated as:

21. 3. The catalytic article of claim 1 or 2, wherein the ceria-zirconia mixed oxide present in the top washcoat and / or the bottom washcoat comprises a dopant selected from lanthana, titania, hafnia, magnesia, calcia, strontia, baria, yttrium, hafnium, praseodymium, neodymium, or any combination thereof.

22. 3. The catalytic article of claim 1 or 2, wherein the substrate is selected from a ceramic substrate, a metal substrate, a ceramic foam substrate, a polymer foam substrate, or a woven fiber substrate.

23. 3. The catalyst article of claim 1, wherein the amount of the ceria-zirconia mixed oxide present in the top washcoat and / or the bottom washcoat is in the range of 10 to 90 wt %, based on the total weight of the washcoats, the amount of the alumina present in the top washcoat and / or the bottom washcoat is in the range of 5.0 to 90 wt %, based on the total weight of the washcoats, and the amount of the ceria-alumina composite present in the top washcoat and / or the bottom washcoat is in the range of 10 to 80 wt %, based on the total weight of the washcoats.

24. 3. A process for preparing the catalyst article of claim 1 or 2, comprising: a) preparing a bottom washcoat including a first zone and a second zone, wherein the first zone is obtained by preparing a first slurry containing palladium supported on the ceria-zirconia mixed oxide or the alumina, or both, and coating the first slurry onto a first portion of the substrate, and the second zone is obtained by preparing a second slurry containing platinum supported on the ceria-alumina composite, and coating the second slurry onto a second portion of the substrate; b) preparing a top washcoat by depositing a third slurry containing rhodium supported on the alumina or the ceria-alumina composite onto the bottom coat; c) subjecting said substrate to calcination at a temperature in the range of 400 to 700°C; The process wherein the step of preparing the slurry comprises a technique selected from incipient wetness impregnation, incipient wetness co-impregnation, and post-addition.

25. 10. An exhaust gas treatment system for an internal combustion engine comprising the catalytic article of claim 1.

26. 26. A method for treating a gaseous exhaust stream containing hydrocarbons, carbon monoxide, and nitrogen oxides, comprising contacting the exhaust stream with the catalytic article of claim 1 or 2 or the exhaust gas treatment system of claim 25.

27. 26. A method for reducing the levels of hydrocarbons, carbon monoxide, and nitrogen oxides in a gaseous exhaust gas stream, comprising contacting the gaseous exhaust gas stream with the catalytic article of claim 1 or 2 or the exhaust gas treatment system of claim 25 to reduce the levels of hydrocarbons, carbon monoxide, and nitrogen oxides in the exhaust gas.

28. 26. Use of the catalytic article of claim 1 or 2 or the exhaust gas treatment system of claim 25 to purify a gaseous exhaust stream comprising hydrocarbons, carbon monoxide, and nitrogen oxides.

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