Layered trimetallic catalyst article and method for manufacturing the same catalyst article

Abstract

The invention claimed in this application provides a trimetallic layered catalyst article comprising: a) an upper layer comprising platinum supported on at least one of an oxygen storage component, a zirconia component, and an alumina component, and rhodium supported on the oxygen storage component; b) a lower layer comprising a front zone and a rear zone, wherein the front zone comprises palladium supported on the oxygen storage component and the alumina component, and the rear zone comprises platinum supported on at least one of the alumina component, the ceria component, and the oxygen storage component; and c) a substrate, wherein the weight ratio of palladium to platinum is in the range of 1.0:0.4 to 1.0:2.0.

Description

Technical Field

[0001] Cross - reference to related applications This application claims the benefit of priority to U.S. Provisional Application No. 62 / 819,696, filed on March 18, 2019, and European Application No. 19169472.8, filed on April 16, 2019.

[0002] The invention claimed in this application relates to a layered catalyst article useful for treating exhaust gas to reduce pollutants contained therein. In particular, the invention claimed in this application relates to a layered trimetallic catalyst article and a method for preparing the catalyst article. More specifically, the invention relates to a segmented layered trimetallic catalyst article and a method for preparing the catalyst article.

Background Art

[0003] Three - way conversion (TWC) catalysts (hereinafter, interchangeably referred to as three - way conversion catalysts, three - way catalysts, TWC catalysts, and TWC) have been used for several years to treat exhaust gas streams from internal combustion engines. Generally, a catalytic converter containing a three - way conversion catalyst is used in the exhaust gas line of an internal combustion engine to treat or purify exhaust gas containing pollutants such as hydrocarbons, nitrogen oxides, and carbon monoxide. The three - way conversion catalyst is typically known to oxidize unburned hydrocarbons and carbon monoxide and reduce nitrogen oxides.

[0004] Typically, most commercially available TWC catalysts contain palladium as the main platinum - group metal component and are used with a lesser amount of rhodium. Since a large amount of palladium is used in the manufacture of catalytic converters that help reduce the amount of exhaust gas pollutants, there may be a shortage of palladium supply in the market in the next few years. Currently, palladium is about 20 - 25% more expensive than platinum. At the same time, due to the decreasing demand for platinum, the price of platinum is expected to decline. One of the reasons may be the decreasing production volume of diesel vehicles.

[0005] Therefore, in order to significantly reduce the cost of the catalyst, it is desirable to replace part of the palladium in the TWC catalyst with platinum. However, the proposed approach is complicated by the need to maintain or improve the desired effectiveness of the catalyst, which may not be possible by simply replacing part of the palladium with platinum.

[0006] Therefore, the focus of the invention claimed in this application is to provide a catalyst article in which at least 50% of the palladium is replaced with platinum without degrading the overall performance of the catalyst article, as explained by comparing the conversion levels of individual CO, HC, and NO x and to provide an overview of the tailpipe emissions of non-methane hydrocarbons (NMHC) and nitrous oxide (NO x ), which is one of the important requirements for vehicle certification by regulatory agencies in most jurisdictions. SUMMARY OF THE INVENTION

[0007] Therefore, the present invention provides a) an upper layer comprising platinum supported on at least one of an oxygen storage component, a zirconia component, and an alumina component, and rhodium supported on the oxygen storage component; b) a lower layer comprising a front zone and a rear zone, wherein the front zone comprises palladium supported on an oxygen storage component and an alumina component, and the rear zone comprises platinum supported on at least one of an alumina component, a ceria component, and an oxygen storage component; c) a substrate, and provides a three-metal layered catalyst article in which the weight ratio of palladium to platinum is in the range of 1.0:0.4 to 1.0:2.0.

[0008] In another aspect, the invention claimed in this application provides a process for preparing a layered catalyst article.

[0009] In yet another aspect, the invention claimed in the present application provides an exhaust system for an internal combustion engine, said system comprising the layered catalyst article of the present invention.

[0010] The invention claimed in the present application also provides a method of treating a gaseous exhaust stream, said method comprising contacting said exhaust stream with a layered catalyst article or an exhaust system according to the present invention. The invention claimed in the present application is a method of reducing the levels of hydrocarbons, carbon monoxide, and nitrogen oxides in a gaseous exhaust stream, said method comprising contacting the gaseous exhaust stream with a layered catalyst article or an exhaust system according to the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] 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 exemplary and should not be construed as limiting the present invention. The above and other features, their nature, and various advantages of the present invention claimed in the present application will become more apparent upon consideration of the following detailed description in conjunction with the accompanying drawings.

[0012]

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Embodiments for Carrying Out the Invention

[0013] Next, the present invention claimed in this application will be more fully described hereinafter. The present invention claimed in this application may be embodied in many different forms and should not be construed as limited to the embodiments described herein. Rather, these embodiments are provided so that this application will be thorough and complete, and will fully convey the scope of the present invention to those skilled in the art. No language in this specification should be construed as indicating any non-claimed element as essential to the practice of the disclosed materials and methods.

[0014] The use of the terms "a", "an", "the" and similar indicatives in the context of describing the materials and methods considered herein (particularly in the context of the following claims) is to be construed to cover both the singular and the plural unless otherwise indicated herein or clearly contradicted by the context.

[0015] The term "about" used throughout this specification is used to account for and clarify minor variations. For example, the term "about" refers to ±5% or less, such as ±2% or less, ±1% or less, ±0.5% or less, ±0.2% or less, ±0.1% or less, or ±0.05% or less. All numerical values are modified by the term "about" whether or not explicitly indicated. Of course, the values modified by the term "about" include the specific values. For example, "about 5.0" should include 5.0.

[0016] All of the methods described in this specification can be performed in any suitable order unless otherwise indicated herein or unless clearly inconsistent with the context. The use of any and all examples or exemplary language (e.g., "such as") provided herein is intended only to better explain the materials and methods and is not limiting of the scope unless otherwise claimed.

[0017] The present invention provides a segmented three-metal layered catalyst article comprising three platinum group metals (PGMs) that can substantially use a large amount of platinum instead of palladium.

[0018] In one embodiment, palladium and platinum are provided in separate layers to avoid the formation of an alloy that may limit the effectiveness of the catalyst under certain conditions. The formation of the alloy may result in the formation of a core-shell structure and / or excessive PGM stabilization and / or sintering. The best performance of the catalyst article is seen when palladium is provided in the lower layer and platinum and rhodium are provided in the upper (second) layer, i.e., the performance can be improved by physically separating platinum and palladium into different washcoat layers. In another embodiment, platinum and palladium are provided in the same layer, e.g., the lower layer, and platinum and palladium are provided in different zones, such as a front zone and a rear zone, to avoid direct contact.

[0019] The design of the segmented three-metal (Pt / Pd / Rh) TWC catalyst article of the present invention claimed in this application showed equivalent or better performance compared to the latest Pd / Rh TWC catalyst article with an equivalent total washcoat, PGM, and Rh loading.

[0020] The platinum group metal (PGM) refers to any component containing PGM (Ru, Rh, Os, Ir, Pd, Pt, and / or Au). For example, the PGM may be in the metallic form with a valence of zero, or the PGM may be in the oxide form. References to "PGM component" take into account the presence of PGM in any valence state. Terms such as "platinum (Pt) component", "rhodium (Rh) component", "palladium (Pd) component", "iridium (Ir) component", "ruthenium (Ru) component", etc. refer to the respective platinum group metal compounds, complexes, etc. that decompose during the calcination or use of the catalyst, or are otherwise converted to the catalytically active form, usually a metal or metal oxide.

[0021] As used herein, the terms "catalyst" or "catalyst composition" refer to a material that promotes a reaction.

[0022] The term "catalytic article" or "catalyst article" refers to a component in which a substrate is coated with a catalyst component used to promote a desired reaction. In one embodiment, the catalytic article is a layered catalytic article. The term "layered catalytic article" refers to a catalytic article in which a substrate is layered with a PGM composition. These compositions may be referred to as washcoats.

[0023] The term "NO x " refers to nitrogen oxide compounds such as NO and / or NO2.

[0024] Thus, in one embodiment, there is provided a three-metal layered catalyst article comprising: a) an upper layer comprising platinum supported on at least one of an oxygen storage component, a zirconia component, and an alumina component, and rhodium supported on the oxygen storage component; b) a lower layer comprising a front zone and a rear zone, wherein the front zone comprises palladium supported on an oxygen storage component and an alumina component, and the rear zone comprises platinum supported on at least one of an alumina component, a ceria component, and an oxygen storage component; and c) a substrate, wherein the weight ratio of palladium to platinum ranges from 1.0:0.4 to 1.0:2.0.

[0025] In one embodiment, the three-metal layered catalyst article comprises: a) an upper layer comprising platinum supported on at least one of an oxygen storage component, a zirconia component, and an alumina component, and rhodium supported on the oxygen storage component; b) a lower layer comprising a front zone and a rear zone, wherein the front zone comprises palladium supported on an oxygen storage component and an alumina component, and the rear zone comprises platinum supported on at least one of an alumina component, a ceria component, and an oxygen storage component, and palladium supported on an alumina component; and c) a substrate, wherein the weight ratio of palladium to platinum ranges from 1.0:0.4 to 1.0:2.0. The lower layer is coated on the substrate, and the upper layer is coated on the lower layer. The lower layer is divided such that the inlet zone (front zone) constitutes 30 to 70% of the length of the substrate, and the outlet zone (rear zone) constitutes 30 to 70% of the length of the substrate. In one embodiment, the lower coat is divided such that the inlet zone (front zone) constitutes 50% of the length of the substrate, and the outlet zone (rear zone) constitutes 50% of the length of the substrate.

[0026] In one embodiment, the three-metal layered catalyst article includes: a) an upper layer including platinum supported on at least one of an oxygen storage component, a zirconia component, and an alumina component, and rhodium supported on the oxygen storage component; b) a lower layer including a front zone and a rear zone, wherein the front zone includes palladium supported on the oxygen storage component and the alumina component, and the rear zone includes platinum supported on at least one of the alumina component, a ceria component, and the oxygen storage component; and c) a substrate, and the weight ratio of palladium to platinum is in the range of 1.0:0.7 to 1.0:1.3.

[0027] In one embodiment, the three-metal layered catalyst article includes: a) an upper layer including platinum supported on at least one of an oxygen storage component, a zirconia component, and an alumina component, and rhodium supported on the oxygen storage component; b) a lower layer including a front zone and a rear zone, wherein the front zone includes palladium supported on the oxygen storage component and the alumina component, and the rear zone includes platinum supported on at least one of the alumina component, a ceria component, and the oxygen storage component; and c) a substrate, and the weight ratio of palladium to platinum to rhodium is in the range of 1.0:0.7:0.1 to 1.0:1.3:0.3.

[0028] In one embodiment, the upper layer of the three-metal layered catalyst article is essentially palladium-free. As used herein, the term "essentially palladium-free" means that no palladium is externally added to the upper layer, but may optionally be present in a minor amount of less than 0.001%. In one embodiment, the three-metal layered catalyst article includes: a) platinum supported on at least one of an oxygen storage component, a zirconia component, and an alumina component, and rhodium supported on the oxygen storage component, an upper layer that is essentially palladium-free; b) a lower layer including a front zone and a rear zone, wherein the front zone includes palladium supported on an oxygen storage component and an alumina component, and the rear zone includes platinum supported on at least one of an alumina component, a ceria component, and an oxygen storage component, a lower layer; c) a substrate, and the weight ratio of palladium to platinum is in the range of 1.0:0.4 to 1.0:2.0. In one embodiment, the three-metal layered catalyst article includes: a) platinum supported on at least one of an oxygen storage component, a zirconia component, and an alumina component, and rhodium supported on the oxygen storage component, an upper layer that is essentially palladium-free; b) a lower layer including a front zone and a rear zone, wherein the front zone includes palladium supported on an oxygen storage component and an alumina component, and the rear zone includes platinum supported on at least one of an alumina component, a ceria component, and an oxygen storage component, a lower layer; c) a substrate, and the weight ratio of palladium to platinum is in the range of 1.0:0.7 to 1.0:1.3. In one embodiment, the three-metal layered catalyst article includes: a) platinum supported on at least one of an oxygen storage component, a zirconia component, and an alumina component, and rhodium supported on the oxygen storage component, an upper layer that is essentially palladium-free; b) a lower layer including a front zone and a rear zone, wherein the front zone includes palladium supported on an oxygen storage component and an alumina component, and the rear zone includes platinum supported on at least one of an alumina component, a ceria component, and an oxygen storage component, a lower layer; c) a substrate, and the weight ratio of palladium to platinum to rhodium is in the range of 1.0:0.7:0.1 to 1.0:1.3:0.3.

[0029] In one embodiment, the three-metal layered catalyst article includes an upper layer including platinum supported on an alumina component and rhodium supported on an oxygen storage component, and a lower layer including a front zone and a rear zone, wherein the front zone includes palladium supported on an oxygen storage component and an alumina component, the rear zone includes platinum supported on a ceria component and an alumina component, the lower layer and a substrate, and the weight ratio of palladium to platinum is in the range of 1.0:0.7 to 1.0:1.3.

[0030] In another embodiment, the three-metal layered catalyst article includes an upper layer including platinum supported on a zirconia component and rhodium supported on an oxygen storage component, and a lower layer including a front zone and a rear zone, wherein the front zone includes palladium supported on an oxygen storage component and an alumina component, the rear zone includes platinum supported on an oxygen storage component and an alumina component and palladium supported on an alumina component, the lower layer and a substrate, and the weight ratio of palladium to platinum is in the range of 1.0:0.7 to 1.0:1.3.

[0031] In one embodiment, the three-metal layered catalyst article includes an upper layer including platinum supported on a zirconia component and rhodium supported on an oxygen storage component, and a lower layer including a front zone and a rear zone, wherein the front zone includes palladium supported on an oxygen storage component and an alumina component, the rear zone includes platinum supported on an oxygen storage component and an alumina component and palladium supported on an alumina component, the lower layer and a substrate, and the weight ratio of palladium to platinum is in the range of 1.0:0.7 to 1.0:1.3, and the rear zone includes platinum supported on 30-60% of the total amount of platinum in the lower layer on an alumina component and platinum supported on 30-60% of the total amount of platinum in the lower layer on a ceria component.

[0032] In one embodiment, the weight ratio of the alumina component to the ceria component in the rear zone ranges from 1.0:1.0 to 2.0:1.0. In one embodiment, the three-metal layered catalyst article includes: a) an upper layer including platinum supported on at least one of an oxygen storage component, a zirconia component, and an alumina component, and rhodium supported on the oxygen storage component; b) a lower layer including a front zone and a rear zone, wherein the front zone includes palladium supported on an oxygen storage component and an alumina component, and the rear zone includes platinum supported on at least one of an alumina component, a ceria component, and an oxygen storage component, and palladium supported on an alumina component; c) a substrate, wherein the weight ratio of palladium to platinum ranges from 1.0:0.4 to 1.0:2.0, and the weight ratio of the alumina component to the ceria component in the rear zone ranges from 1.0:1.0 to 2.0:1.0.

[0033] In one embodiment, the weight ratio of the alumina component to the oxygen storage component in the rear zone and the front zone ranges from 3.0:1.0 to 0.5:1.0. In one embodiment, the three-metal layered catalyst article includes: a) an upper layer including platinum supported on at least one of an oxygen storage component, a zirconia component, and an alumina component, and rhodium supported on the oxygen storage component; b) a lower layer including a front zone and a rear zone, wherein the front zone includes palladium supported on an oxygen storage component and an alumina component, and the rear zone includes platinum supported on at least one of an alumina component, a ceria component, and an oxygen storage component, and palladium supported on an alumina component; c) a substrate, wherein the weight ratio of palladium to platinum ranges from 1.0:0.4 to 1.0:2.0, and the weight ratio of the alumina component to the oxygen storage component in the rear zone and the front zone ranges from 3.0:1.0 to 0.5:1.0.

[0034] In one embodiment, the weight ratio of the alumina component to the oxygen storage component in the rear zone and the front zone ranges from 2.0:1.0 to 0.6:1.0.

[0035] In one embodiment, the three-metal layered catalyst article comprises: a) platinum supported on at least one of an oxygen storage component, a zirconia component, and an alumina component, and rhodium supported on an oxygen storage component containing ceria in the range of 5.0 to 50 wt% based on the total weight of the oxygen storage component, an upper layer; b) a lower layer comprising a front zone and a rear zone, wherein the front zone contains palladium supported on an oxygen storage component and an alumina component, and the rear zone contains platinum supported on at least one of an alumina component, a ceria component, and an oxygen storage component, and palladium supported on an alumina component, a lower layer; c) a substrate, and the weight ratio of palladium to platinum is in the range of 1.0:0.4 to 1.0:2.0.

[0036] In one embodiment, rhodium is supported on an oxygen storage component containing ceria in the range of 5.0 to 15 wt% based on the total weight of the oxygen storage component.

[0037] In one embodiment, the three-metal layered catalyst article comprises: a) platinum supported on at least one of an oxygen storage component, a zirconia component, and an alumina component, and rhodium supported on an oxygen storage component containing ceria in the range of 5.0 to 50 wt% based on the total weight of the oxygen storage component, an upper layer; b) a lower layer comprising a front zone and a rear zone, wherein the front zone contains palladium supported on an oxygen storage component and an alumina component, and the rear zone contains platinum supported on at least one of an alumina component, a ceria component, and an oxygen storage component, and palladium supported on an alumina component, a lower layer; c) a substrate, and the weight ratio of palladium to platinum is in the range of 1.0:0.4 to 1.0:2.0, and the proportion of the amount of platinum in the lower layer and the upper layer is in the range of 50:50 to 80:20 based on the total amount of platinum present in the layered catalyst article.

[0038] In one embodiment, the three-metal layered catalyst article is 1.0 to 200 g / ft supported on at least one of an oxygen storage component, a zirconia component, and an alumina component 31.0 to 100 g / ft 3 supported on an oxygen storage component containing ceria in the range of 5.0 to 50% by weight based on the total weight of the platinum and the oxygen storage component 3 a top layer comprising rhodium of 1.0 to 300 g / ft 3 and, b) a bottom layer comprising a front zone and a rear zone, wherein the front zone comprises 1.0 to 300 g / ft 3 of palladium supported on an oxygen storage component and an alumina component 3 and the rear zone comprises 1.0 to 200 g / ft 3 of platinum supported on at least one of an alumina component, a ceria component, and an oxygen storage component and palladium supported on an alumina component 3 a bottom layer, and c) a substrate, wherein the weight ratio of palladium to platinum is in the range of 1.0:0.4 to 1.0:2.0

[0039] In one embodiment, the three-metal layered catalyst article comprises: a) a top layer comprising 10 to 80 g / ft 3 of platinum supported on at least one of an oxygen storage component, a zirconia component, and an alumina component and 1.0 to 20 g / ft 3 of rhodium supported on an oxygen storage component containing ceria in the range of 5.0 to 50% by weight based on the total weight of the oxygen storage component 3 b) a bottom layer comprising a front zone and a rear zone, wherein the front zone comprises 10 to 80 g / ft 3 of palladium supported on an oxygen storage component and an alumina component, and the rear zone comprises 10 to 80 g / ft 3 of platinum supported on an alumina component (and) a ceria component or an oxygen storage component and palladium supported on an alumina component 3 c) a substrate, and the weight ratio of palladium to platinum is in the range of 1.0:0.4 to 1.0:2.0 3 3

[0040] ​​In one exemplary embodiment, the three-metal layered catalyst article includes an upper layer including platinum supported on an alumina component and rhodium supported on an oxygen storage component, and a lower layer including a front zone and a rear zone, wherein the front zone includes palladium supported on an oxygen storage component and an alumina component, and the rear zone includes platinum supported on a ceria component and an alumina component, and the weight ratio of palladium to platinum ranges from 1.0:0.7 to 1.0:1.3.

[0041] In one exemplary embodiment, the three-metal layered catalyst article includes an upper layer including platinum supported on an alumina component and rhodium supported on an oxygen storage component, and a lower layer including a front zone and a rear zone, wherein the front zone includes palladium supported on an oxygen storage component and an alumina component, and the rear zone includes platinum supported on a ceria component and an alumina component, and the weight ratio of palladium to platinum ranges from 1.0:1.0.

[0042] In one exemplary embodiment, the three-metal layered catalyst article includes an upper layer including platinum supported on an alumina component and rhodium supported on an oxygen storage component, and a lower layer including a front zone and a rear zone, wherein the front zone includes palladium supported on an oxygen storage component and an alumina component, and the rear zone includes platinum supported on a ceria component and an alumina component, and the weight ratio of palladium to platinum to rhodium ranges from 1.0:0.7:0.1 to 1.0:1.3:0.3.

[0043] In one exemplary embodiment, the three-metal layered catalyst article includes an upper layer including platinum supported on an alumina component and rhodium supported on an oxygen storage component, and a lower layer including a front zone and a rear zone, wherein the front zone includes palladium supported on an oxygen storage component and an alumina component, and the rear zone includes platinum supported on a ceria component and an alumina component, and the weight ratio of palladium to platinum to rhodium ranges from 1.0:1.0:0.105.

[0044] In an exemplary embodiment, the three-metal layered catalyst article has 19 g / ft of platinum supported on an alumina component 3 and 4.0 g / ft of rhodium supported on an oxygen storage component 3 in an upper layer, and a lower layer including a front zone and a rear zone, wherein the front zone has 76 g / ft of palladium supported on an oxygen storage component and an alumina component 3 and the rear zone has 38 g / ft of platinum supported on a ceria component and an alumina component 3 in the lower layer.

[0045] In one exemplary embodiment, the three-metal layered catalyst article includes an upper layer including platinum supported on an alumina component and rhodium supported on an oxygen storage component, and a lower layer including a front zone and a rear zone, wherein the front zone includes palladium supported on an oxygen storage component and an alumina component, the rear zone includes platinum supported on a ceria component and an alumina component, the weight ratio of palladium to platinum to rhodium is in the range of 1.0:1.0:0.105, the weight ratio of the alumina component to the oxygen storage component is in the range of 2.0:1.0 to 0.6:1.0, and the weight ratio of the alumina component to the ceria component is in the range of 1.0:1.0 to 2.0:1.0.

[0046] In one embodiment, the three-metal layered catalyst article includes an upper layer filled with 4.0 g / ft of rhodium supported on an oxygen storage component and 19 g / ft of platinum supported on an alumina component 3 and a front zone of a lower layer filled with 76 g / ft of palladium supported on an alumina component and an oxygen storage component 3 and a rear zone of the lower layer filled with 38 g / ft of platinum supported on a ceria component and an alumina component. 3 3

[0047] ​​In one exemplary embodiment, the three-metal layered catalyst article includes an upper layer including platinum supported on a zirconia component and rhodium supported on an oxygen storage component, and a lower layer including a front zone and a rear zone, wherein the front zone includes palladium supported on an oxygen storage component and an alumina component, and the rear zone includes platinum supported on an oxygen storage component and an alumina component and palladium supported on an alumina component, and the weight ratio of palladium to platinum ranges from 1.0:0.7 to 1.0:1.3.

[0048] In one embodiment, there is provided the three-metal catalyst article described above herein, wherein platinum and palladium are present in the rear zone of the lower layer and platinum and / or palladium are thermally or chemically fixed to the support. Thermal fixation includes, for example, depositing the PGM on the support via an incipient wetness impregnation method and then heating and calcining the resulting PGM / support mixture. As an example, the mixture is calcined at 400 - 700 °C for 1 - 3 hours at a ramp rate of 1 - 25 °C / min. Chemical fixation includes depositing the PGM on the support and then using an additional reagent to fix and chemically convert the PGM. As an example, an aqueous Pd nitrate solution is impregnated into alumina. Instead of drying or calcining the impregnated powder, it is instead added to an aqueous solution of Ba hydroxide. As a result of the addition, acidic Pd nitrate reacts with basic Ba hydroxide to produce insoluble Pd hydroxide and Ba nitrate. Thus, Pd is chemically fixed as an insoluble component within and on the surface of the pores of the alumina support. Alternatively, the support can first be impregnated with an acidic component and then a second basic component. The chemical reaction between the two reagents deposited on the support, e.g., alumina, results in the formation of an insoluble or nearly insoluble compound that also deposits within and on the surface of the pores of the support.

[0049] In one exemplary embodiment, the three-metal layered catalyst article includes an upper layer comprising platinum supported on a zirconia component and rhodium supported on an oxygen storage component, and a lower layer including a front zone and a rear zone, wherein the front zone comprises palladium supported on an oxygen storage component and an alumina component, and the rear zone comprises platinum supported on an oxygen storage component and an alumina component and palladium supported on an alumina component, and platinum and / or palladium is thermally or chemically fixed, and the weight ratio of palladium to platinum to rhodium ranges from 1.0:0.7:0.1 to 1.0:1.3:0.3.

[0050] In one exemplary embodiment, the upper layer comprises platinum supported on a zirconia component and rhodium supported on an oxygen storage component, the lower layer includes a front zone and a rear zone, the front zone comprises palladium supported on an oxygen storage component and an alumina component, the rear zone comprises platinum supported on an oxygen storage component and an alumina component and palladium supported on an alumina component, and platinum and / or palladium is thermally or chemically fixed, and the weight ratio of palladium to platinum to rhodium ranges from 1.0:1.0:0.105.

[0051] In one embodiment, the three-metal layered catalyst article is filled with an upper layer containing 4.0 g / ft of rhodium supported on an oxygen storage component and 19 g / ft of platinum supported on lanthania-zirconia, a front zone of a lower layer filled with 60.8 g / ft of palladium supported on an alumina component and an oxygen storage component, and a rear zone of the lower layer filled with 38 g / ft of platinum supported on an oxygen storage component and 15.2 g / ft of palladium supported on an alumina component, and platinum and / or palladium is thermally or chemically fixed. 3 of rhodium and 19 g / ft 3 of platinum supported on lanthania-zirconia, a front zone of a lower layer filled with 60.8 g / ft 3 of palladium supported on an alumina component and an oxygen storage component, and a rear zone of the lower layer filled with 38 g / ft 3 of platinum supported on an oxygen storage component and 15.2 g / ft 3 of palladium supported on an alumina component, and platinum and / or palladium is thermally or chemically fixed.

[0052] In one embodiment, the oxygen storage component includes ceria-zirconia, ceria-zirconia-lanthana, ceria-zirconia-yttria, ceria-zirconia-lanthana-yttria, ceria-zirconia-neodymia, ceria-zirconia-praseodymia, ceria-zirconia-lanthana-neodymia, ceria-zirconia-lanthana-praseodymia, ceria-zirconia-lanthana-neodymia-praseodymia, or any combination thereof, and the amount of the oxygen storage component is 20 to 80 wt% based on the total weight of the lower layer or the upper layer.

[0053] In one embodiment, the alumina component includes alumina, lanthana-alumina, ceria-alumina, ceria-zirconia-alumina, zirconia-alumina, lanthana-zirconia-alumina, barrier-alumina, barrier-lanthana-alumina, barrier-lanthana-neodymia-alumina, or a combination thereof, and the amount of the alumina component is 10 to 90 wt% based on the total weight of the lower layer or the upper layer.

[0054] In one embodiment, the ceria component includes ceria or stabilized ceria having a cerium oxide content of at least 85 wt%. The ceria component further includes a dopant selected from zirconia, yttria, praseodymia, lanthana, neodymia, samaria, gadolinia, alumina, titania, barrier, strontia, and combinations thereof, and the amount of the dopant is 1.0 to 20 wt% based on the total weight of the ceria component.

[0055] In the context of the present invention, the term zirconia component is a zirconia-based support stabilized or promoted by lanthana or barrier or ceria. Examples include lanthana-zirconia, barium-zirconia, strontian-zirconia, and ceria-zirconia.

[0056] In one embodiment, the zirconia component has a zirconium oxide content of 70 wt% or more.

[0057] In one embodiment, the three-metal layered catalyst article comprises: an upper layer including platinum supported on at least one of an oxygen storage component, a zirconia component, and an alumina component, and rhodium supported on the oxygen storage component; a lower layer including a front zone and a rear zone, wherein the front zone includes palladium supported on the oxygen storage component and the alumina component, and at least one alkaline earth metal oxide including barium oxide, strontium oxide, lanthanum oxide, or any combination thereof in an amount of 0.5 to 20 wt% based on the total weight of the front zone, and the rear zone includes platinum supported on at least one of the alumina component, a ceria component, and the oxygen storage component, and palladium supported on the alumina component; and a substrate, and the weight ratio of palladium to platinum is in the range of 1.0:0.4 to 1.0:2.0.

[0058] In one exemplary embodiment, the three-metal layered catalyst article comprises an upper layer including platinum supported on an alumina component and rhodium supported on an oxygen storage component, and a lower layer including a front zone and a rear zone, wherein the front zone includes palladium supported on the oxygen storage component and the alumina component and barium oxide, and the rear zone includes platinum supported on the ceria component and the alumina component, and the weight ratio of palladium to platinum is in the range of 1.0:0.7 to 1.0:1.3.

[0059] In one exemplary embodiment, the three-metal layered catalyst article comprises an upper layer including platinum supported on an alumina component and rhodium supported on an oxygen storage component, and a lower layer including a front zone and a rear zone, wherein the front zone includes palladium supported on the oxygen storage component and the alumina component and barium oxide, and the rear zone includes platinum supported on the ceria component and the alumina component, and the weight ratio of palladium to platinum is 1.0:1.0.

[0060] In one exemplary embodiment, the three-metal layered catalyst article includes an upper layer comprising platinum supported on an alumina component and rhodium supported on an oxygen storage component, and a lower layer including a front zone and a rear zone, wherein the front zone includes palladium supported on an oxygen storage component and an alumina component and barium oxide, and the rear zone includes platinum supported on a ceria component and an alumina component, and the lower layer, and the weight ratio of palladium to platinum to rhodium ranges from 1.0:0.7:0.1 to 1.0:1.3:0.3.

[0061] In one exemplary embodiment, the three-metal layered catalyst article includes an upper layer comprising platinum supported on a zirconia component and rhodium supported on an oxygen storage component, and a lower layer including a front zone and a rear zone, wherein the front zone includes palladium supported on an oxygen storage component and an alumina component and barium oxide, and the rear zone includes platinum supported on an oxygen storage component and an alumina component and palladium supported on an alumina component, and the lower layer, and the weight ratio of palladium to platinum ranges from 1.0:0.7 to 1.0:1.3.

[0062] In one exemplary embodiment, the three-metal layered catalyst article includes an upper layer comprising platinum supported on a zirconia component and rhodium supported on an oxygen storage component, and a lower layer including a front zone and a rear zone, wherein the front zone includes palladium supported on an oxygen storage component and an alumina component and barium oxide, and the rear zone includes platinum supported on an oxygen storage component and an alumina component and palladium supported on an alumina component, and the lower layer, and the weight ratio of palladium to platinum to rhodium ranges from 1.0:0.7:0.1 to 1.0:1.3:0.3.

[0063] In one exemplary embodiment, the three-metal layered catalyst article includes an upper layer comprising platinum supported on an alumina component and rhodium supported on an oxygen storage component, and a lower layer including a front zone and a rear zone, wherein the front zone includes palladium supported on an oxygen storage component and an alumina component and barium oxide, and the rear zone includes platinum supported on a ceria component and an alumina component, and the lower layer, and the weight ratio of palladium to platinum to rhodium ranges from 1.0:0.7:0.1 to 1.0:1.3:0.3, the weight ratio of the alumina component to the oxygen storage component ranges from 2.0:1.0 to 0.6:1.0, and the weight ratio of the alumina component to the ceria component ranges from 1.0:1.0 to 2.0:1.0.

[0064] In one exemplary embodiment, the three-metal layered catalyst article includes an upper layer comprising platinum supported on a zirconia component and rhodium supported on an oxygen storage component, and a lower layer including a front zone and a rear zone, wherein the front zone includes palladium supported on an oxygen storage component and an alumina component and barium oxide, and the rear zone includes platinum supported on an oxygen storage component and an alumina component and palladium supported on an alumina component, and the lower layer, and the weight ratio of palladium to platinum to rhodium ranges from 1.0:0.7:0.1 to 1.0:1.3:0.3, and the weight ratio of the alumina component to the oxygen storage component ranges from 2.0:1.0 to 0.6:1.0.

[0065] As used herein, the term "substrate" typically refers to a monolithic material in the form of a washcoat containing a plurality of particles containing the catalyst composition, with the catalyst material disposed on the monolithic material.

[0066] Reference to a "monolithic substrate" or a "honeycomb substrate" means a single, homogeneous and continuous structure from inlet to outlet.

[0067] As used herein, the term "washcoat" has its ordinary meaning in the art of thin adherent coatings of catalyst or other materials applied to a substrate material, such as a honeycomb-shaped carrier member, that is porous enough to allow passage of the gas stream being processed. A washcoat is formed by preparing a slurry containing particles of a certain solids content (e.g., 15 - 60 wt%) in a liquid vehicle, then coating this onto the substrate and drying to provide a washcoat layer.

[0068] As used herein, as described in Heck, Ronald, and Farrauto, Robert, Catalytic Air Pollution Control, New York: Wiley - Interscience, 2002, pp. 18 - 19, a washcoat layer comprises a compositionally distinct layer of material disposed on the surface of a monolithic substrate or a lower washcoat layer. In one embodiment, the substrate contains one or more washcoat layers, and each washcoat layer can be different in some way (e.g., can differ in its physical properties such as particle size or crystallite phase) and / or can have a different chemical catalytic function.

[0069] A catalyst article may be "unused", which means that it is new and has not been exposed to any heat or thermal stress for an extended period. "Unused" can also mean that the catalyst has been recently prepared and has not been exposed to any exhaust gas or high temperature. Similarly, an "aged" catalyst article is not unused and has been exposed to exhaust gas and high temperature (i.e., above 500 °C) for an extended period (i.e., more than 3 hours).

[0070] According to one or more embodiments, the substrate of the catalyst article of the present invention claimed in this application can be constructed of any material typically used to prepare automotive catalysts, and typically comprises a ceramic or metal monolithic honeycomb structure. In one embodiment, the substrate is a ceramic substrate, a metal substrate, a ceramic foam substrate, a polymer foam substrate, or a textile fiber substrate.

[0071] The substrate typically provides a plurality of wall surfaces to which a washcoat containing the catalyst composition described above herein is applied and adhered, thereby acting as a carrier for the catalyst composition.

[0072] Exemplary metal substrates include heat-resistant metals and metal alloys such as titanium and stainless steel and other alloys in which iron is a substantial or main component. Such alloys may contain one or more of nickel, chromium, and / or aluminum, and the total amount of these metals is preferably at least 15% by weight of the alloy, for example, 10 - 25% by weight of chromium, 3 - 8% by weight of aluminum, and up to 20% by weight of nickel. The alloy may also contain one or more metals in small or trace amounts, such as manganese, copper, vanadium, and titanium. The surface of the metal substrate can be oxidized at a high temperature, for example, 1000 °C or higher, to form an oxide layer on the surface of the substrate, improving the corrosion resistance of the alloy and facilitating the adhesion of the washcoat layer to the metal surface.

[0073] Examples of ceramic materials used in the construction of the substrate include any suitable refractory material, such as cordierite, mullite, cordierite-alumina, silicon nitride, zircon mullite, spodumene, alumina-silica magnesia, zircon silicate, sillimanite, magnesium silicate, zircon, petalite, alumina, aluminosilicate, and the like.

[0074] Any suitable substrate can be used, such as a monolithic flow-through substrate having a plurality of fine and parallel gas flow paths extending from an inlet of the substrate to an outlet face so that the passage is open to the fluid flow. The passage, which is an essentially straight path from the inlet to the outlet, is defined by walls coated with a catalyst material as a washcoat such that the gas flowing through the passage contacts the catalyst material. The flow paths of the monolithic substrate can be thin-walled channels having any suitable cross-sectional shape, such as trapezoidal, rectangular, square, sinusoidal, hexagonal, elliptical, and circular. Such a structure contains from about 60 to about 1200 or more gas inlet openings (i.e., "cells") (cpsi) per square inch of cross-section, more typically from about 300 to 900 cpsi. The wall thickness of the flow-through substrate can vary, and a typical range is from 0.002 to 0.1 inches. A representative commercially available flow-through substrate is a cordierite substrate having 400 cpsi and a wall thickness of 6 mils, or 600 cpsi and a wall thickness of 4.0 mils. However, it will be understood that the present invention is not limited to a particular substrate type, material, or geometry. In an alternative embodiment, the substrate can be a wall-flow substrate in which each passage is blocked by a non-porous plug at one end of the substrate body and alternating passages are blocked at the opposite end face. This requires the gas flow to pass through the porous walls of the wall-flow substrate to reach the outlet. Such a monolithic substrate can contain up to about 700 or more cpsi, such as from about 100 to 400 cpsi, more typically from about 200 to about 300 cpsi. The cross-sectional shape of the cells can vary as described above. The wall-flow substrate typically has a wall thickness of from 0.002 to 0.1 inches. A representative commercially available wall-flow substrate is constructed from porous cordierite and examples thereof have 200 cpsi and a wall thickness of 10 mils, or 300 cpsi and a wall thickness of 8 mils, and a wall porosity of 45 - 65%. Other ceramic materials such as aluminum titanate, silicon carbide, and silicon nitride are also used as wall-flow filter substrates. However, it will be understood that the present invention is not limited to a particular substrate type, material, or shape.When the substrate is a wall-flow substrate, it should be noted that in addition to being disposed on the surface of the wall, the catalyst composition 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.

[0075] As used herein, the term "flow" broadly refers to any combination of flowing gases that may contain particulate matter of solids or liquids.

[0076] As used herein, the terms "upstream" and "downstream" refer to the relative directions corresponding to the flow of engine exhaust gas from the engine towards the tail pipe, with the engine in the upstream position and any pollution reduction articles such as the tail pipe and filters and catalysts being downstream of the engine.

[0077] Figures 5A and 5B show an exemplary substrate 2 in the form of a through-flow substrate coated with the washcoat composition described herein. Referring to Figure 5A, the exemplary substrate 2 has a cylindrical shape and has a cylindrical outer surface 4, an upstream end face 6, and a corresponding downstream end face 8 identical to the end face 6. The substrate 2 has a plurality of fine and parallel gas flow paths 10 formed therein. As seen in Figure 5B, the flow paths 10 are formed by walls 12, extend through the substrate 2 from the upstream end face 6 to the downstream end face 8, and the passages 10 are unobstructed, allowing fluid flow, for example, gas flow, to flow longitudinally through the substrate 2 via the gas flow paths 10. As can be more readily seen in Figure 6, the walls 12 are dimensioned and configured such that the gas flow paths 10 have a substantially regular polygonal shape. As shown, the washcoat composition can be applied in a plurality of distinct layers, if desired. In the embodiment shown, the washcoat consists of a separate first washcoat layer 14 adhered to the walls 12 of the substrate member and a second separate washcoat layer 16 coated over the first washcoat layer 14. In one embodiment, the invention claimed in this application is also practiced with two or more (e.g., three or four) washcoat layers and is not limited to the two-layer embodiment shown.

[0078] Figure 6 shows an exemplary substrate 2 in the form of a wall-flow filter substrate coated with the washcoat composition described herein. As seen in Figure 6, the exemplary substrate 2 has a plurality of passages 52. The s 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. The passages are alternately blocked by an inlet plug 58 at the inlet end and an outlet plug 60 at the outlet end to form a checkerboard pattern that is reversed at the inlet 54 and the outlet 56. The gas flow 62 enters through an unblocked channel inlet 64, is stopped by the outlet plug 60, and diffuses to the outlet side 66 through the (porous) channel wall 53. The gas cannot return to the inlet side of the wall due to the inlet plug 58. The porous wall filter used in the present invention has catalytic activity on the walls of the element that have or contain one or more catalytic materials thereon or therein. The catalytic material may be present only on the inlet side of the element wall, only on the outlet side, both on the inlet side and the outlet side, or the wall itself may be composed of all or part of the catalytic material. The present invention includes the use of one or more catalytic material layers on the inlet wall and / or the outlet wall of the element.

[0079] In another aspect, a process for preparing a layered catalytic article is also provided. In one embodiment, the process includes preparing a front zone lower layer slurry, depositing the slurry on a substrate to obtain a front zone of the lower layer, preparing a rear zone lower layer slurry, depositing the slurry on the substrate to obtain a rear zone of the lower layer, preparing an upper layer slurry, depositing the upper layer slurry on the lower layer to obtain the upper layer, and then firing at a temperature in the range of 400 - 700 °C. The step of preparing the slurry includes techniques selected from incipient wetness impregnation, incipient wetness co-impregnation, and post-addition.

[0080] The initial wet impregnation technique, also known as capillary impregnation or dry impregnation, is generally used in the synthesis of heterogeneous materials, i.e., catalysts. Typically, an active metal precursor is dissolved in an aqueous or organic solution, and then the metal-containing solution is added to the catalyst support, which contains the same pore volume as the volume of the added solution. Due to capillary action, the solution is drawn into the pores of the support. The solution added in excess of the pore volume of the support causes the solution transport to change from the capillary 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. After appropriate dilution, multiple active metal precursors may be co-impregnated onto the catalyst support. Alternatively, the active metal precursor is introduced into the slurry via post-addition under stirring during the slurry preparation process.

[0081] 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 an active metal such as rhodium chloride, rhodium nitrate, rhodium acetate, or a combination thereof (when rhodium is the active metal), and palladium nitrate, palladium tetraamine, palladium acetate, or a combination thereof (when palladium is the active metal) is used. After treating the support particles with the active metal solution, the particles are dried by heat treatment at a high temperature (e.g., 100 - 150 °C) for a certain period (e.g., 1 - 3 hours), and then calcined to convert the active metal into a more catalytically active form. An exemplary calcination process involves heat treatment in air at a temperature of about 400 - 550 °C for 10 minutes to 3 hours. If necessary, the above process can be repeated by means of impregnation to reach the desired filling level of the active metal.

[0082] The above-described catalyst composition is typically prepared in the form of catalyst particles as described above. These catalyst particles are mixed with water to form a slurry for the purpose of coating a catalyst substrate such as a honeycomb-type substrate. 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. The binder, when present, is typically used in an amount of about 1.0 to 5.0 wt% of the total washcoat loading. Acidic or basic species are added to the slurry to adjust the pH. For example, in some embodiments, the pH of the slurry is adjusted by the addition of ammonium hydroxide, an aqueous nitric acid solution, or acetic acid. A typical pH range for the slurry is from about 3.0 to 12.

[0083] The slurry may be milled to reduce the particle size and promote mixing of the particles. Milling is accomplished using a ball mill, a continuous mill, or other similar equipment, and the solids content of the slurry can be, for example, from about 20 to 60 wt%, more specifically from about 20 to 40 wt%. In one embodiment, the milled slurry is characterized by a D 90 particle size. D 90 is determined using a dedicated particle size analyzer. The equipment used in this example measures the particle size of a small amount of slurry using laser diffraction. D in microns 90 typically means that 90% of the number of particles have a diameter smaller than the quoted value.

[0084] Use any washcoat technology known in the art to coat the slurry onto the catalyst substrate. In one embodiment, the catalyst substrate is immersed in the slurry one or more times or otherwise coated with the slurry. Thereafter, the coated substrate is dried at a high temperature (e.g., 100 - 150 °C) for a certain period (e.g., 10 minutes - 3 hours), and then fired by heating at, for example, 400 - 700 °C, typically for about 10 minutes - about 3 hours. After drying and firing, the final washcoat coating layer is considered to be essentially solvent-free. After firing, the catalyst loading obtained by the above washcoat technology can be determined by calculating the difference between the coated weight and the uncoated weight of the substrate. As will be apparent to those skilled in the art, the catalyst loading can be adjusted by changing the rheology of the slurry. Further, the coating / drying / firing process for generating the washcoat can be repeated as needed to build up the coating to the desired loading level or thickness, i.e., apply more than one washcoat.

[0085] In certain embodiments, the coated substrate is aged by subjecting the coated substrate to a heat treatment. In one embodiment, the aging is performed at a temperature of about 850 °C - about 1050 °C in an environment of 10% by volume of water while alternately supplying hydrocarbon and air for 50 - 75 hours. Accordingly, in certain embodiments, an aged catalyst article is provided. In certain embodiments, particularly effective materials include metal oxide-based supports (including, but not limited to, substantially 100% ceria supports) that maintain a high percentage (e.g., about 95 - 100%) of their pore volume during aging (e.g., aging at about 850 °C - about 1050 °C with 10% by volume of water while alternately supplying hydrocarbon and air for 50 - 75 hours).

[0086] In another aspect, the invention claimed in the present application provides an exhaust system for an internal combustion engine. The exhaust system includes the catalyst article described above herein. In one embodiment, the exhaust system includes a platinum group metal-based three-way conversion (TWC) catalyst article and a layered catalyst article according to the present invention, the platinum group metal-based three-way conversion (TWC) catalyst article being located downstream from the internal combustion engine and the layered catalyst article being located downstream in fluid communication with the platinum group metal-based three-way conversion (TWC) catalyst article.

[0087] In another embodiment, the exhaust system includes a platinum group metal-based three-way conversion (TWC) catalyst article and a layered catalyst article according to the present invention, Layered catalyst article which is located downstream from the internal combustion engine, and the platinum group metal-based three-way conversion (TWC) catalyst article is Layered catalyst article located downstream in fluid communication therewith. The exhaust system is shown in FIG. 2. FIG. 2A shows the exhaust system, where the reference TWC CC1 catalyst article includes a lower layer containing Pd supported on an oxygen storage component and alumina, barium oxide, and an upper layer containing Rh supported on alumina and Pd supported on the oxygen storage component, with the substrate located downstream from the internal combustion engine, while the reference TWC CC2 catalyst article includes a lower layer containing Pd supported on an oxygen storage component and alumina, barium oxide, and an upper layer containing Rh supported on alumina and Rh supported on the oxygen storage component, with the substrate located downstream such that it is in fluid communication with the TWC CC1 catalyst article. The PGM loading (Pt / Pd / Rh) in TWC CC1 is 0 / 76 / 4 and in TWC CC2 is 0 / 14 / 4.

[0088] Figure 2B shows an exhaust system. The catalyst B of the present invention includes an upper layer containing Pt supported on an alumina component and Rh supported on an oxygen storage component, a front zone containing a Pd supported on an oxygen storage component and an alumina component and barium oxide, and a lower layer containing a rear zone containing Pt supported on a ceria component and an alumina component. The substrate is located downstream from the internal combustion engine, while the reference TWC CC2 catalyst article includes a lower layer containing Pd supported on an oxygen storage component and alumina and barium oxide, and an upper layer containing Rh supported on alumina and Rh supported on an oxygen storage component. The substrate is located downstream so as to be in fluid communication with the catalyst article of the present invention. The PGM loading ((Pt / Pd / Rh) in the catalyst article A of the present invention is 38 / 38 / 4, and in TWC CC2 it is / 14 / 4.

[0089] Figure 2C shows an exhaust system. The catalyst A of the present invention includes an upper layer containing Pt supported on a lanthana-zirconia component and Rh supported on an oxygen storage component, a front zone containing a Pd supported on an oxygen storage component and an alumina component and barium oxide, and a lower layer containing a rear zone containing Pt supported on an oxygen storage component, Pd supported on an alumina component, and barium oxide. The substrate is located downstream from the internal combustion engine, while the reference TWC CC2 catalyst article includes a lower layer containing Pd supported on an oxygen storage component and alumina and barium oxide, and an upper layer containing Rh supported on alumina and Rh supported on an oxygen storage component. The substrate is located downstream so as to be in fluid communication with the catalyst article of the present invention. The PGM loading ((Pt / Pd / Rh) in the catalyst article B of the present invention is 38 / 38 / 4, and in TWC CC2 it is 0 / 14 / 4.

[0090] In one aspect, the invention claimed in the present application also provides a method for treating a gaseous exhaust stream containing hydrocarbons, carbon monoxide, and nitrogen oxides. The method includes contacting the exhaust stream with a catalytic article or an exhaust system according to the invention claimed in the present application. Terms such as "exhaust stream", "engine exhaust stream", "exhaust gas stream" refer to any combination of flowing engine effluent gases that may also contain solid or liquid particulate matter. The stream contains gaseous components and may contain certain non-gaseous components such as droplets, solid particles, etc., for example, the exhaust of a lean burn engine. The exhaust stream of a lean burn engine typically contains combustion products, incomplete combustion products, nitrogen oxides, combustible and / or carbonaceous particulate matter (soot), and unreacted oxygen and / or nitrogen. Such terms similarly refer to the effluent downstream of one or more other catalyst system components as described herein. In one embodiment, a method for treating an exhaust stream containing carbon monoxide is provided.

[0091] In another aspect, the invention claimed in the present application also provides a method for reducing the levels of hydrocarbons, carbon monoxide, and nitrogen oxides in a gaseous exhaust stream. The method includes contacting the gaseous exhaust stream with a catalytic article or an exhaust system according to the invention claimed in the present application to reduce the levels of hydrocarbons, carbon monoxide, and nitrogen oxides in the exhaust gas.

[0092] In yet another aspect, the invention claimed in the present application also provides the use of the layered catalytic article of the invention claimed in the present application for purifying a gaseous exhaust stream containing hydrocarbons, carbon monoxide, and nitrogen oxides.

[0093] In some embodiments, the catalyst article converts at least about 60%, or at least about 70%, or at least about 75%, or at least about 80%, or at least about 90%, or at least about 95% of the amount of carbon monoxide, hydrocarbons, and nitrogen compounds present in the exhaust gas stream before contacting the catalyst article. In some embodiments, the catalyst article converts hydrocarbons to carbon dioxide and water. In some embodiments, the catalyst article converts at least about 60%, or at least about 70%, or at least about 75%, or at least about 80%, or at least about 90%, or at least about 95% of the amount of hydrocarbons present in the exhaust gas stream before contacting the catalyst article. In some embodiments, the catalyst article converts carbon monoxide to carbon dioxide. In some embodiments, the catalyst article converts nitrogen oxides to nitrogen.

[0094] In some embodiments, the catalyst article converts at least about 60%, or at least about 70%, or at least about 75%, or at least about 80%, or at least about 90%, or at least about 95% of the amount of nitrogen oxides present in the exhaust gas stream before contacting the catalyst article. In some embodiments, the catalyst article converts at least about 50%, or at least about 60%, or at least about 70%, or at least about 80%, or at least about 90%, or at least about 95% of the total amount of combined hydrocarbons, carbon dioxide, and nitrogen oxides present in the exhaust gas stream before contacting the catalyst article.

Examples

[0095] The aspects of the invention claimed in this application are more fully shown by the following examples, which are described to illustrate certain aspects of the invention and should not be construed as limiting it.

[0096] Example 1: Preparation of Reference CC1 Catalyst Article (RC-1, Bimetallic: Pd / Rh, Ratio: 1:0.052) A Pd / Rh-based TWC catalyst article was prepared and used as a closely coupled reference catalyst article. The total PGM loading (Pt / Pd / Rh) is 0 / 76 / 4. The bottom coat contains 68.4 g / ft 3 of Pd, or 90% of the total Pd in the catalyst article. The top coat contains 7.6 g / ft 3 of Pd and 4.0 g / ft 3 of Rh, or 10% of the total Pd and 100% of the total Rh in the catalyst article. The bottom coat has a washcoat loading of 2.34 g / inch 3 and the top coat has a washcoat loading of 1.355 g / inch 3 The reference catalyst article (RC-CC1) is shown in Figure 1A.

[0097] The bottom coat was prepared by impregnating 314 grams of alumina with a 60% Pd nitrate solution (43.3 grams, 28% Pd nitrate aqueous solution) and impregnating 785 grams of ceria-zirconia with a 40% Pd nitrate solution (28.9 grams, 28% Pd nitrate aqueous solution). The alumina portion was chemically fixed by adding the Pd / alumina mixture to an aqueous solution of 85.6 grams of barium acetate in water. 39 grams of barium sulfate was also added to the mixture. This component was then ground to a D 90 less than 16 μm. The pH was controlled to around 4.0 - 5.0 by adding nitric acid as needed. The ceria-zirconia portion was added to water and ground to a D 90 less than 16 μm. The pH was controlled to around 4 - 5 by adding nitric acid as needed. The two components were then blended and 128 grams of alumina binder was added.

[0098] The top coat has two components. The first component was prepared by impregnating 903 grams of alumina with a mixture of 20.7 grams of rhodium nitrate (9.9% Rh content) and 80.5 grams of neodymium nitrate (27.5% Nd2O3 content) in 560 grams of water. Following this step, it was calcined at 500 °C for 2 hours to fix the PGM to the support. The resulting powder was then mixed with water and ground to a D 90It was pulverized. If necessary, the pH was controlled to around 4.0 - 5.0 by adding nitric acid. The second component was prepared by impregnating 13.8 grams of palladium nitrate (28% Pd content) mixed with water into 260.4 grams of ceria - zirconia, and then calcining at 500 °C for 2 hours to fix the PGM on the support. Then, the obtained powder was mixed with water and pulverized to D less than 16 μm 90 It was pulverized. If necessary, the pH was controlled to around about 4 - 5 by adding nitric acid. The two slurries thus obtained were blended, and 156 grams of alumina binder was added. If necessary, the pH was controlled to around about 4 - 5 by adding nitric acid.

[0099] The catalyst article was prepared by first coating the lower coat slurry on a 600 / 3.5 ceramic substrate. Then, the obtained coated substrate was dried and calcined at 500 °C for 2 hours. Then, the upper coat slurry was applied. The obtained product was calcined again at 500 °C for 2 hours.

[0100] Example 2: Preparation of the catalyst article A of the present invention (IC - A, trimetallic, upper layer: Rh - OSC and Pt - Al, lower layer: Pd in the front zone and Pt in the rear zone, ratio: 1:1:0.105): The catalyst article was formulated using PGM (Pt:Pd:Rh) to obtain a 38 / 38 / 4 design. The total PGM loading was 80 g / ft 3 The lower coat was divided such that the inlet coat (front zone) constituted 50% of the length of the substrate and contained 76 g / ft 3 of Pd, or 100% of the total Pd in the catalyst article. The outlet zone (rear zone) of the lower coat constituted 50% of the length of the substrate and contained 38 g / ft 3 of Pt, or 50% of the total Pt in the catalyst article. The upper coat covered 100% of the length of the substrate and contained 19 g / ft 3 of Pt and 4.0 g / ft 3 of Rh, or 50% of the total Pt and 100% of the total Rh in the catalyst article. The lower coat was 2.124 g / inch 3has a washcoat loading of, and the top coat has a washcoat loading of 1.558 g / inch 3 The catalyst article A of the present invention is shown in FIG. 1B.

[0101] The bottom coat inlet contains two components. The first component was prepared by impregnating 961 grams of alumina with a mixture of 117.78 grams of a 28% aqueous Pd nitrate solution, 251 grams of Ba acetate (59.9% BaO content), and 643 grams of water. Following this step, it was calcined at 500 °C for 2 hours to fix the PGM to the support. The second component was prepared by impregnating 2690 grams of ceria-zirconia with a mixture of 176.7 grams of a 28% aqueous Pd nitrate solution and 1137.5 grams of water. Following this step, it was calcined at 500 °C for 2 hours to fix the PGM to the support. The alumina component was then mixed with water and 143.3 grams of barium sulfate. The mixture was then ground to a D 90 less than 16 μm. The pH was controlled to around about 4.0 - 5 by adding nitric acid as necessary. The ceria-zirconia portion was added to water and ground to a D 90 less than 16 μm. The pH was controlled to around about 4 - 5 by adding nitric acid as necessary. The two components were then blended and 475.5 grams of an alumina binder was added.

[0102] The lower coat outlet contains two components. The first component was prepared by impregnating 2509.4 grams of alumina with a mixture of 146.1 grams of a 14.3% aqueous Pt nitrate solution and 1914.9 grams of water. Following this step, it was calcined at 500 °C for 2 hours to fix the PGM to the support. The second component was prepared in two steps. First, a mixture of 73.1 grams of a 14.3% aqueous Pt nitrate solution, 320.5 grams of aluminum nitrate (14.8% Al2O3 content), and 40 grams of water was impregnated into 1239.2 grams of ceria. Following this step, it was calcined at 500 °C for 2 hours to fix the PGM to the support. Subsequently, the second step was carried out by impregnating the above Pt / Al mixture into the Pt / Al / CeO2 component to achieve the desired metal loading. That is, a further mixture of 73.1 grams of a 14.3% aqueous Pt nitrate solution, 320.5 grams of aluminum nitrate (14.8% Al2O3 content), and 40 grams of water was impregnated into the Pt / Al / ceria component. Following this step, it was calcined at 500 °C for 2 hours to fix the PGM to the support. Then, the alumina component was mixed with water and 144.4 grams of barium sulfate. Then, this mixture was ground to a D 90 less than 16 μm. The pH was controlled to around 4.0 - 5.0 by adding nitric acid as necessary. The ceria portion was added to water and ground to a D 90 less than 16 μm. The pH was controlled to around 4.0 - 5.0 by adding nitric acid as necessary. Then, the two components were blended and 479.2 grams of an alumina binder was added.

[0103] The upper coat has two components. The first component was prepared by impregnating 241.6 grams of alumina with a mixture of 44.5 grams of Pt nitrate (14.3% Pt content) in 158 grams of water. Following this step, it was calcined at 500 °C for 2 hours to fix the PGM to the support. Then, the resulting powder was mixed with water and ground to a D 90It was pulverized. If necessary, the pH was controlled to around 4.0 - 5.0 by adding nitric acid. The second component was prepared by impregnating 13.5 grams of rhodium nitrate (9.9% rhodium content) and 292 grams of water into 648.3 grams of ceria - zirconia, and then calcining at 500 °C for 2 hours to fix the PGM on the support. Then, the obtained powder was mixed with water and pulverized to a D of less than 16 μm 90 It was pulverized. If necessary, the pH was controlled to around 4.0 - 5.0 by adding nitric acid. The two slurries thus obtained were blended, and 102.1 grams of an alumina binder was added. If necessary, the pH was controlled to around 4.0 - 5.0 by adding nitric acid.

[0104] The catalyst article was prepared by first coating the lower coat inlet slurry on a 600 / 3.5 ceramic substrate. The inlet coat was dried, and subsequently the lower coat outlet slurry was applied. Then, the obtained coated substrate was dried and calcined at 500 °C for 2 hours. Then, the upper coat slurry was applied. The obtained product was calcined again at 500 °C for 2 hours.

[0105] Example 3: Preparation of Catalyst Article B of the Present Invention (IC - B, trimetallic, upper layer: Rh and Pt, lower layer: Pd in the front zone, and Pt and Pd in the rear zone, ratio: 1:1:0.105) The catalyst article was formulated using PGM (Pt:Pd:Rh) to obtain a 38 / 38 / 4 design. The total PGM loading was 80 g / ft 3 and the lower coat was divided such that the inlet coat constituted 50% of the length of the substrate and contained 60.8 g / ft 3 of Pd, or 80% of the total Pd in the catalyst article. The outlet zone of the lower coat constituted 50% of the length of the substrate and contained 38 g / ft 3 of Pt, or 50% of the total Pt in the catalyst article, and 15.2 g / ft 3 of Pd, or 20% of the total Pd in the catalyst article. The upper coat covered 100% of the length of the substrate and contained 19 g / ft 3 of Pt and 4.0 g / ft 3contains 50% of the total Pt and 100% of the total Rh in the catalyst article. The lower coat has a washcoat loading of 2.115 g / inch 3 and the upper coat has a washcoat loading of 1.563 g / inch 3 . The catalyst article B of the present invention is shown in FIG. 1C.

[0106] The lower coat inlet contains two components. The first component was prepared by impregnating 1736.7 grams of alumina with a mixture of 118.3 grams of a 28% aqueous Pd nitrate solution, 252.5 grams of Ba acetate (containing 59.9% BaO), and 1055 grams of water. Following this step, it was calcined at 500 °C for 2 hours to fix the PGM to the support. The second component was prepared by impregnating 1929.7 grams of ceria - zirconia with a mixture of 118.37 grams of a 28% aqueous Pd nitrate solution and 727 grams of water. Following this step, it was calcined at 500 °C for 2 hours to fix the PGM to the support. Then, the alumina component was mixed with water and 143.9 grams of barium sulfate. Then, this mixture was ground to a D 90 less than 13 μm. The pH was controlled to around 4.0 - 5.0 by adding nitric acid as necessary. The ceria - zirconia portion was added to water and ground to a D 90 less than 13 μm. The pH was controlled to around 4.0 - 5.0 by adding nitric acid as necessary. Then, the two components were blended and 477.6 grams of an alumina binder was added.

[0107] The lower coat outlet contains two components. The first component was prepared by impregnating 1468.8 grams of alumina with a mixture of 60.0 grams of a 28% aqueous Pd nitrate solution, 160.1 grams of Ba acetate (with a BaO content of 59.9%), and 942 grams of water. Following this step, it was calcined at 500 °C for 2 hours to fix the PGM to the support. The second component was prepared in two steps. A mixture of 295.6 grams of a 14.3% aqueous Pt nitrate solution and 623 grams of water was impregnated into 2356.7 grams of ceria-zirconia. Following this step, it was calcined at 500 °C for 2 hours to fix the PGM to the support. The alumina component was mixed with water and then ground to a D 90 less than 13 μm. If necessary, the pH was controlled to around 4.0 - 5.0 by adding nitric acid. The ceria-zirconia portion was added to water and ground to a D 90 less than 13 μm. If necessary, the pH was controlled to around 4.0 - 5.0 by adding nitric acid. Then, the two components were blended and 484.6 grams of an alumina binder was added.

[0108] The upper coat has two components. The first component was prepared by impregnating 352.5 grams of lanthana-zirconia with a mixture of 44.3 grams of Pt nitrate (with a Pt content of 14.3%) in 127 grams of water. Following this step, it was calcined at 500 °C for 2 hours to fix the PGM to the support. The second component was prepared by impregnating 411.2 grams of ceria-zirconia with 13.5 grams of Rh nitrate (with a Rh content of 9.9%) and 161 grams of water, and then calcining at 500 °C for 2 hours to fix the PGM to the support. The two calcined powders were mixed with water, 117.5 grams of alumina was added, and the mixture was ground to a D 90 less than 12 μm. If necessary, the pH was controlled to around 4.0 - 5.0 by adding nitric acid. Finally, 145.4 grams of an alumina binder was added to the slurry, and if necessary, the pH was controlled to around 4 - 5 by adding nitric acid.

[0109] The catalyst article was prepared by first coating a 600 / 3.5 ceramic substrate with a lower coat inlet slurry. The inlet coat was dried and subsequently a lower coat outlet slurry was applied. The resulting coated substrate was then dried and fired at 500 °C for 2 hours. Then, an upper coat slurry was applied. The resulting product was fired again at 500 °C for 2 hours.

[0110] Example 4: Preparation of Catalyst Article C (RC-C, trimetallic, upper layer: Rh - Al and Pt - OSC, lower layer: Pd in the front zone and Pt outside the range in the rear zone) The catalyst article was formulated using PGM (Pt:Pd:Rh) to obtain a 38 / 38 / 4 design. The total PGM loading was 80 g / ft 3 and the lower coat was sectioned such that the inlet coat constituted 50% of the length of the substrate and contained 76 g / ft 3 of Pd, or 100% of the total Pd in the catalyst article. The outlet zone of the lower coat constituted 50% of the length of the substrate and contained 38 g / ft 3 of Pt, or 50% of the total Pt in the catalyst article. The upper coat covered 100% of the length of the substrate and contained 19 g / ft 3 of Pt and 4.0 g / ft 3 of Rh, or 50% of the total Pt and 100% of the total Rh in the catalyst article. The lower coat had a washcoat loading of 2.124 g / inch 3 and the upper coat had a washcoat loading of 1.558 g / inch 3 Catalyst article C is shown in Figure 1D.

[0111] The lower coat inlet contains two components. The first component was prepared by impregnating 961 grams of alumina with a mixture of 117.78 grams of 28% aqueous Pd nitrate, 251 grams of Ba acetate (59.9% BaO content), and 643 grams of water. Following this step, it was calcined at 500 °C for 2 hours to fix the PGM to the support. The second component was prepared by impregnating 2690 grams of ceria-zirconia with a mixture of 176.7 grams of 28% aqueous Pd nitrate and 1137.5 grams of water. Following this step, it was calcined at 500 °C for 2 hours to fix the PGM to the support. The alumina component was then mixed with water and 143.3 grams of barium sulfate. The mixture was then milled to a D 90 less than 16 μm. The pH was controlled to around 4.0 - 5.0 by adding nitric acid if necessary. The ceria-zirconia portion was added to water and milled to a D 90 less than 16 μm. The pH was controlled to around 4 - 5 by adding nitric acid if necessary. The two components were then blended and 475.5 grams of an alumina binder was added.

[0112] The lower coat outlet contains two components. The first component was prepared by impregnating 1882 grams of alumina with a mixture of 109.6 grams of a 14.3% aqueous solution of platinum nitrate and 1436 grams of water. Following this step, it was calcined at 500 °C for 2 hours to fix the PGM to the support. The second component was prepared in two steps. A mixture of 54.8 grams of a 14.3% aqueous solution of platinum nitrate, 234.5 grams of aluminum nitrate (with an Al2O3 content of 15.2%), and 25 grams of water was impregnated into 929.4 grams of ceria. Following this step, it was calcined at 500 °C for 2 hours to fix the PGM to the support. Subsequently, the second step was carried out by impregnating the above Pt / Al mixture into the Pt / Al / CeO2 component to achieve the desired metal loading. That is, a further mixture of 54.8 grams of a 14.3% aqueous solution of platinum nitrate, 234.5 grams of aluminum nitrate (with an Al2O3 content of 15.2%), and 25 grams of water was impregnated into the Pt / Al / ceria component. Following this step, it was calcined at 500 °C for 2 hours to fix the PGM to the support. Then, the alumina component was mixed with water and 144.4 grams of barium sulfate. Then, this mixture was ground to a D 90 less than 16 μm. The ceria portion, with the pH controlled to around 4 - 5 by adding nitric acid as needed, was added to water and ground to a D 90 less than 16 μm. The pH was controlled to around 4.0 - 5.0 by adding nitric acid as needed. Then, the two components were blended and 359.4 grams of an alumina binder was added.

[0113] The upper coat has two components. The first component was prepared by impregnating 235.7 grams of ceria - zirconia with a mixture of 44.5 grams of platinum nitrate (with a Pt content of 14.3%) and 97.0 grams of an aqueous solution of lanthanum nitrate (with a La2O3 content of 26.8%). Following this step, it was calcined at 500 °C for 2 hours to fix the PGM to the support. Then, the resulting powder was mixed with water and ground to a D 90It was pulverized. The second component whose pH was controlled to around about 4 to 5 by adding nitric acid as necessary was prepared by impregnating 627.6 grams of alumina with 13.5 grams of nitric acid Rh (Rh content of 9.9%) and 498 grams of water, and then firing at 500 °C for 2 hours to fix the PGM to the support. Then, the obtained powder was mixed with water and pulverized to D less than 16 μm 90 It was pulverized. The pH was controlled to around 4.0 to 5.0 by adding nitric acid as necessary. The two slurries thus obtained were blended, and 102.1 grams of an alumina binder was added. The pH was controlled to around about 4 to 5 by adding nitric acid as necessary

[0114] The catalyst article was prepared by first coating the lower coat inlet slurry on a 600 / 3.5 ceramic substrate. The inlet coat was dried, and subsequently the lower coat outlet slurry was applied. Then, the obtained coated substrate was dried and fired at 500 °C for 2 hours. Then, the upper coat slurry was applied. The obtained product was fired again at 500 °C for 2 hours

[0115] Example 5: Preparation of catalyst article D (IC-D, trimetallic, upper layer: Rh, Pd and Pt, lower layer: Pd in the front zone and Pt in the rear zone). The catalyst article was formulated using PGM (Pt:Pd:Rh) to obtain a 38 / 38 / 4 design. The total PGM loading was 80 g / ft 3 and the lower coat was divided such that the inlet coat constituted 50% of the length of the substrate and contained 72.2 g / ft 3 of Pd, or 95% of the total Pd in the catalyst article. The outlet zone of the lower coat constituted 50% of the length of the substrate and contained 38 g / ft 3 of Pt, or 50% of the total Pt in the catalyst article. The upper coat covered 100% of the length of the substrate and contained 19 g / ft 3 of Pt, 1.9 g / ft 3 of Pd, and 4.0 g / ft 3 of Rh, or 50% of the total Pt, 5% of the total Pd, and 100% of the total Rh in the catalyst article. The lower coat was 2.122 g / inch3 has a washcoat loading of, and the top coat has a washcoat loading of 1.558 g / inch 3 The catalytic article D is shown in FIG. 1E.

[0116] The bottom coat inlet contains two components. The first component was prepared by impregnating 961.8 grams of alumina with a mixture of 112.0 grams of a 28% aqueous Pd nitrate solution, 251.6 grams of barium acetate (containing 59.9% BaO), and 647 grams of water. Following this step, it was calcined at 500 °C for 2 hours to fix the PGM to the support. The second component was prepared by impregnating 2693.1 grams of ceria-zirconia with a mixture of 168.0 grams of a 28% aqueous Pd nitrate solution and 1145 grams of water. Following this step, it was calcined at 500 °C for 2 hours to fix the PGM to the support. The alumina component was then mixed with water and 143.5 grams of barium sulfate. The mixture was then ground to a D 90 less than 16 μm. The ceria-zirconia portion, with the pH controlled to around 4 - 5 by adding nitric acid as needed, was added to water and ground to a D 90 less than 16 μm. The pH was controlled to around 4.0 - 5.0 by adding nitric acid as needed. The two components were then blended and 476.0 grams of an alumina binder was added.

[0117] The bottom coat outlet was prepared by impregnating 2954.8 grams of ceria-zirconia with a mixture of 297.3 grams of a 14.3% aqueous Pt nitrate solution and 844 grams of water. Following this step, it was calcined at 500 °C for 2 hours to fix the PGM to the support. The calcined powder was then mixed with water, 985 grams of alumina was added, and the mixture was then ground to a D 90 less than 13 μm. 487.0 grams of an alumina binder was added and the pH was controlled to around 4.0 - 5.0 by adding nitric acid as needed.

[0118] The upper coat has three components. The first component was prepared by impregnating 294.6 grams of lanthanum-zirconia with a mixture of 44.5 grams of Pt nitrate (14.3% Pt content) in 72 grams of water. Following this step, it was calcined at 500 °C for 2 hours to fix the PGM to the support. The second component was prepared by impregnating 471.4 grams of ceria-zirconia with 13.5 grams of Rh nitrate (9.9% Rh content) and 163 grams of water, and then calcining at 500 °C for 2 hours to fix the PGM to the support. The third component was prepared by impregnating 123.2 grams of alumina with 2.3 grams of Pd nitrate (28% Pd content) and 92 grams of water, and then calcining at 500 °C for 2 hours to fix the PGM to the support.

[0119] Next, the alumina powder was mixed with water and milled to a D of less than 18 μm. 90 The Pt- and Rh-containing powders were added and the mixture was milled to a D of less than 13 μm. 90 The pH was controlled to around 4.0 - 5.0 by adding nitric acid as necessary. Finally, 102 grams of an alumina binder were added to the slurry and the pH was controlled to around 4.0 - 5.0 by adding nitric acid as necessary.

[0120] The catalyst article was prepared by first coating a 600 / 3.5 ceramic substrate with a lower coat inlet slurry. The inlet coat was dried and subsequently a lower coat outlet slurry was applied. The resulting coated substrate was then dried and calcined at 500 °C for 2 hours. Then, the upper coat slurry was applied. The resulting product was calcined again at 500 °C for 2 hours.

[0121] Example 6: Preparation of Catalyst Articles E and F (RC-E: Trimetallic, upper layer: Rh-OSC, lower layer: Pd in the front zone, and Pt in the rear zone; RC-F: upper layer: Rh-Al / OSC, lower layer: Pd in the front zone, Pt in the rear zone, out of range) Catalyst articles E and F were formulated using PGM (Pt:Pd:Rh) to obtain a 38 / 38 / 4 design. The total PGM loading was 80 g / ft3 It is as follows. The lower coat is such that the inlet coat constitutes 50% of the length of the substrate and is 76 g / ft 3 of Pd, or 100% of the total Pd in the catalyst article. The outlet zone of the lower coat constitutes 50% of the length of the substrate and contains 76 g / ft 3 of Pt, or 100% of the total Pt in the catalyst article. The upper coat covers 100% of the length of the substrate and contains 4.0 g / ft 3 of Rh, or 100% of the total Rh in the catalyst article. The lower coat has a washcoat loading of 2.122 g / inch 3 and the upper coat has a washcoat loading of 1.558 g / inch 3 .

[0122] The same divided lower coat formulation is used for both catalyst articles. The lower coat inlet contains two components. The first component was prepared by impregnating 960.8 grams of alumina with a mixture of 117.8 grams of a 28% aqueous Pd nitrate solution, 251.3 grams of Ba acetate (containing 59.9% BaO), and 643 grams of water. Following this step, it was calcined at 500 °C for 2 hours to fix the PGM to the support. The second component was prepared by impregnating 2690.3 grams of ceria - zirconia with a mixture of 176.7 grams of a 28% aqueous Pd nitrate solution and 1137 grams of water. Following this step, it was calcined at 500 °C for 2 hours to fix the PGM to the support. Then, the alumina component was mixed with water and 143.3 grams of barium sulfate. Then, this mixture was ground to a D 90 less than 16 μm. 90 The ceria - zirconia portion was added to water and ground to a D

[0123] The lower coat outlet was prepared by impregnating 3380.5 grams of ceria-zirconia with a mixture of 583.05 grams of 14.3% platinum nitrate aqueous solution, 524.4 grams of aluminum nitrate (containing 14.8% Al2O3), and 476.6 grams of water. Following this step, it was calcined at 500 °C for 2 hours to fix the PGM to the support. Then, the calcined powder was mixed with water, 440.43 grams of alumina was added, and then the mixture was ground to a D 90 less than 13 μm. 487.0 grams of alumina binder was added, and the pH was controlled to around 4 - 5 by adding nitric acid as needed.

[0124] The upper coat of the catalyst article E was prepared by impregnating 836.3 grams of ceria-zirconia with a mixture of 13.7 grams of rhodium nitrate (containing 9.9% Rh) and 339 grams of water, and then calcining at 500 °C for 2 hours to fix the PGM to the support. Then, the calcined powder was mixed with water, 59.7 grams of alumina was added, and then the mixture was ground to a D 90 less than 13 μm. The pH was controlled to around 4.0 - 5.0 by adding nitric acid as needed. Finally, 103.5 grams of alumina binder was added.

[0125] The upper coat of the catalyst article F contained two components. The first component was prepared by impregnating 448 grams of alumina with a mixture of 6.8 grams of rhodium nitrate (containing 9.9% Rh) and 358 grams of water, and then calcining at 500 °C for 2 hours to fix the PGM to the support. The second component was prepared by impregnating 448 grams of ceria-zirconia with a mixture of 6.8 grams of rhodium nitrate (containing 9.9% Rh) and 182 grams of water, and then calcining at 500 °C for 2 hours to fix the PGM to the support. Then, the alumina powder was mixed with water and ground to a D 90 less than 18 μm. The pH was controlled to around 4.0 - 5.0 by adding nitric acid as needed. The ceria-zirconia powder was added, and the mixture was ground to a D 90 less than 13 μm. The pH was controlled to around 4.0 - 5.0 by adding nitric acid as needed.

[0126] Both catalyst articles E and F were prepared by first coating the lower coat inlet slurry onto a 600 / 3.5 ceramic substrate. The inlet coat was dried, followed by application of the lower coat outlet slurry. The resulting coated substrate was then dried and fired at 500 °C for 2 hours. The upper coat slurry was then applied. The resulting product was fired again at 500 °C for 2 hours.

[0127] Example 7: Preparation of reference CC2 catalyst article (bimetallic, RC-2) The reference CC2 catalyst article is a PGM TWC (Pt:Pd:Rh) of 0 / 14 / 4 design used at the second close-coupled position. The lower coat was prepared by mixing 718.5 grams of alumina with water and controlling the pH to about 4.0 - 5.0 by adding nitric acid, followed by grinding to a D 90 less than 16 μm. Then, 716.2 grams of ceria-zirconia was added to the slurry. Next, 27.7 grams of Pd (27.3% Pd content) was added to the slurry, mixed briefly, and then the slurry was ground again to a D 90 less than 14 μm. In the next step, 71.5 grams of barium sulfate and 239.2 grams of alumina binder were added, and the final slurry was mixed for 20 minutes.

[0128] The upper coat contained two components. The first component was prepared by impregnating 483 grams of alumina with 11.3 grams of rhodium nitrate (9.8% Rh content) in 367 grams of water. The powder was then added to water, and methyl ethyl amine (MEA) was added until the pH equaled 8. The slurry was then mixed for 20 minutes and the pH was lowered to 5.5 - 6 using nitric acid. The slurry was then ground to a D 90It was pulverized. The second component was prepared by impregnating 979.3 grams of ceria - zirconia with 11.3 grams of Rhodium nitrate (9.8% Rh content) mixed with 550 grams of water. Then, the powder was added to water, and methyl ethyl amine (MEA) was added until the pH became equal to 8. Then, the slurry was mixed for 20 minutes, 80.6 grams of zirconium nitrate (19.7% ZrO2 content) was added, and the pH was lowered to 5.5 - 6 using nitric acid as necessary. Then, the slurry was pulverized to less than 14 μm D 90 It was pulverized. Then, the two obtained slurries were blended, 245 grams of alumina binder was added, and the pH was controlled to around 4.0 - 5.0 by adding nitric acid as necessary.

[0129] The catalyst article was prepared by first coating a 600 / 3.5 ceramic substrate with a lower coat slurry. Then, the obtained coated substrate was dried and calcined at 500 °C for 2 hours. Then, the upper coat slurry was applied. The obtained product was calcined again at 500 °C for 2 hours.

[0130] Example 9: Aging and Testing of Catalyst Articles All catalyst articles were coated on a 4.16 × 2.717 - inch 600 / 3.5 cordierite substrate. The catalyst articles were aged in an engine for 50 hours at an inlet temperature of 950 °C while alternately supplying lean gas and rich gas. Subsequently, using the FTP - 75 test protocol, the catalyst articles were tested as a CC1 + CC2 system in a 2016 - model SULEV - 30 vehicle equipped with a 4 - cylinder gasoline engine. To ensure data reproducibility, each test was repeated at least 3 times. The same CC2 catalyst article was used in all cases, and only the CC1 catalyst article was changed so that the influence of the CC1 catalyst article on the system performance could be directly compared. The catalyst systems are shown in the following table.

Table 1

[0131] Figure 3 of the attached drawings shows the improved performance of the divided catalyst article A (IC-A) of the present invention in the exhaust gas regulation test. The effect of division is that the essential advantage of the design is confirmed without assigning a high concentration of Pd at the inlet of the catalyst article because it does not significantly affect the ignition of the catalyst. The catalyst article A of the present invention has demonstrated superior performance compared to the Pd / Rh reference catalyst article 1 in terms of the emissions of hydrocarbons and carbon monoxide in both the intermediate bed and the tail pipe. Specifically, when the catalyst article A of the present invention is used, the hydrocarbon emissions in the intermediate bed and the tail pipe are reduced by 20% and 20% respectively, and carbon monoxide is reduced by 21% and 25% respectively. In the case of the catalyst article of the present invention, the NO x emissions in the intermediate bed are 20% higher, but the NO x emission values in the tail pipe are the same for both the reference and the catalyst article A of the present invention.

[0132] Figure 3 also shows a comparison between the catalyst article A of the present invention and the catalyst articles E and F. As in the catalyst article A, the presence of platinum in both the upper and lower layers results in improved emission reduction results compared to a catalyst article containing platinum only in the lower outlet layer (rear zone). The catalyst article A of the present invention has hydrocarbon emissions in the intermediate bed that are 40 - 45% lower, CO emissions in the intermediate bed that are 20 - 27% lower, and NO x emissions in the intermediate bed that are 30 - 40% lower compared to the catalyst articles E and F. The difference in activity also carries over to the tail pipe, and the catalyst article A achieves a reduction in hydrocarbon emissions of approximately 38%, CO emissions of 16 - 38%, and NO x emissions of approximately 25% compared to catalyst articles (catalyst articles E and F) without Pt in the upper coat.

[0133] The difference in the performance of the catalyst articles also highlights the importance of the selection of the Pt support in the outlet zone of the lower coat. Generally, a ratio of alumina to ceria or ceria - zirconia or zirconia of 3.0 - 0.5, or more preferably about 2.0 - 0.6, is preferred and provides the highest activity when the combination of materials is selected to support Pt.

[0134] Catalyst article A also shows, in FIG. 3, the advantage of containing rhodium supported on alumina in the upper layer and platinum supported on OSC, as compared to a catalyst article containing rhodium supported on OSC and platinum supported on an alumina or zirconia-based support (e.g., lanthanum-zirconia or ceria-zirconia) with a Zr content of more than 70%, for the purpose of reducing emissions. Catalyst article A achieved a reduction of 18% hydrocarbons, 10% CO, and 25% NO in the intermediate bed, as compared to catalyst article C. x When the CC2 catalyst article is also described as a system, catalyst article A of the present invention showed 20% lower tailpipe hydrocarbons and 29% lower CO emissions while maintaining the same NO x performance.

[0135] FIG. 4 shows a comparison between catalyst article B of the present invention and a reference catalyst article. Catalyst article B showed improved performance, with a reduction of 6% hydrocarbons, 22% CO, and 26% NO in the intermediate bed, as compared to reference CC1. Further, catalyst article B of the present invention showed a reduction in the tailpipe of 2% hydrocarbons, 12% CO, and 7% NO, respectively, for hydrocarbons, CO, and NO. x x

[0136] Catalyst article B (IC-B) of the present invention was also compared with catalyst article D, which functions in the same manner as the reference system but does not achieve the conversion level of catalyst article B of the present invention. One reason for this discrepancy is the imbalance in the selection of PGM for the upper coat and the support. As an example, in the case of catalyst article C, Rh is assigned to alumina and Pt is assigned to OSC, which, combined with the relative amounts of the support materials, limits the effectiveness of the three-metal design of catalyst article C.

[0137] Overall, it has been found that the catalyst articles of the present invention enhance the reduction of pollutants such as CO, HC, and NO, as compared to existing catalyst articles containing rhodium and palladium. Further, the catalyst articles of the present invention are economical as compared to existing catalyst articles. ​​

[0138] Throughout this specification, references to "one embodiment", "a particular embodiment", "one or more embodiments", or "an embodiment" mean that a particular feature, structure, material, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention claimed in this application. Thus, the appearances of phrases such as "in one or more embodiments", "in a particular embodiment", "in some embodiments", "in one embodiment", or "in an embodiment" in various places throughout this specification are not necessarily referring to the same embodiment of the invention claimed in this application. Furthermore, the particular features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments. All of the various embodiments, aspects, and alternatives disclosed herein can be combined in all variations, regardless of whether such features or elements are explicitly combined in the description of a particular embodiment of this specification. The invention claimed in this application is intended to be read as a whole to mean that any separable features or elements of the disclosed invention can be combined in any of its various aspects and embodiments, unless the context clearly indicates otherwise.

[0139] The embodiments disclosed herein have been described with reference to particular embodiments, but it should be understood that these embodiments are merely illustrative of the principles and applications of the invention claimed in this application. It will be apparent to those skilled in the art that various modifications and changes can be made to the methods and apparatuses of the invention claimed in this application without departing from the spirit and scope of the invention claimed in this application. Accordingly, the invention claimed in this application is intended to include modifications and changes within the scope of the appended claims and their equivalents, and the above embodiments are presented for purposes of illustration and not limitation. All patents and publications cited herein are incorporated by reference herein for their specific teachings as described, unless other incorporated descriptions are specifically provided.

Claims

1. A three - metal layered catalyst article for the conversion of CO, HC, and NOx in the exhaust gas from an engine, comprising: a. An upper layer comprising platinum supported on at least one of a zirconia component and an alumina component, and rhodium supported on an oxygen storage component; b. A lower layer comprising a front zone and a rear zone, wherein the front zone comprises palladium supported on an oxygen storage component and an alumina component, and the rear zone comprises platinum supported on at least one of an alumina component and a ceria component; c. A substrate; The weight ratio of palladium to platinum is in the range of 1.0:0.4 to 1.0:2.0; The oxygen storage component comprises ceria - zirconia, ceria - zirconia - lanthana, ceria - zirconia - yttria, ceria - zirconia - lanthana - yttria, ceria - zirconia - neodymia, ceria - zirconia - praseodymia, ceria - zirconia - lanthana - neodymia, ceria - zirconia - lanthana - praseodymia, ceria - zirconia - lanthana - neodymia - praseodymia, or any combination thereof; The ceria component further comprises a dopant selected from zirconia, yttria, praseodymia, lanthana, neodymia, samaria, gadolinia, alumina, titania, barium, strontia, and combinations thereof; A three - metal layered catalyst article.

2. The layered catalyst article according to claim 1, wherein the weight ratio of palladium to platinum is in the range of 1.0:0.7 to 1.0:1.

3.

3. The layered catalyst article according to any one of claims 1 - 2, wherein the weight ratio of palladium to platinum to rhodium is in the range of 1.0:0.7:0.1 to 1.0:1.3:0.

3.

4. The layered catalyst article according to any one of claims 1 - 3, wherein the upper layer is essentially free of palladium.

5. The layered catalyst article according to any one of claims 1 to 4, wherein the rear zone contains platinum supported on 30 to 60% of the alumina component based on the total amount of platinum in the lower layer, and platinum supported on 30 to 60% of the ceria component based on the total amount of platinum in the lower layer.

6. The layered catalyst article according to any one of claims 1 to 5, wherein the weight ratio of the alumina component to the ceria component in the rear zone is in the range of 1.0:1.0 to 2.0:1.

0.

7. The layered catalyst article according to any one of claims 1 to 6, wherein rhodium is supported on the oxygen storage component containing ceria in the range of 5.0 to 50% by weight based on the total weight of the oxygen storage component.

8. The layered catalyst article according to any one of claims 1 to 7, wherein the ratio of the amount of platinum in the lower layer and the upper layer is in the range of 50:50 to 80:20 based on the total amount of platinum present in the layered catalyst article.

9. The layered catalyst article according to any one of claims 1 to 8, wherein the amount of the oxygen storage component is 20 to 80% by weight based on the total weight of the lower layer or the upper layer.

10. The layered catalyst article according to any one of claims 1 to 9, wherein the alumina component includes alumina, lanthana-alumina, ceria-alumina, ceria-zirconia-alumina, zirconia-alumina, lanthana-zirconia-alumina, barium-alumina, barium-lanthana-alumina, barium-lanthana-neodymia-alumina, or a combination thereof, and the amount of the alumina component is 10 to 90% by weight based on the total weight of the lower layer or the upper layer.

11. The layered catalyst article according to any one of claims 1 to 10, wherein rhodium is supported on the oxygen storage component containing ceria in the range of 5.0 to 15% by weight based on the total weight of the oxygen storage component.

12. The layered catalyst article according to any one of claims 1 to 11, wherein the amount of the dopant is 1.0 to 20% by weight based on the total weight of the ceria component.

13. The layered catalyst article according to any one of claims 1 to 12, wherein the zirconia component comprises lanthana-zirconia, barium-zirconia, or strontia-zirconia having a zirconia content of 70% by weight or more based on the total weight of the zirconia component.

14. The layered catalyst article according to any one of claims 1 to 13, wherein the substrate is a ceramic substrate, a metal substrate, a ceramic foam substrate, a polymer foam substrate, or a textile fiber substrate.

15. The layered catalyst article according to any one of claims 1 to 14, further comprising at least one alkaline earth metal oxide, wherein the front zone contains barium oxide, strontium oxide, or any combination thereof in an amount of 1.0 to 20% by weight based on the total weight of the front zone.

16. The layered catalyst article according to any one of claims 1 to 4, wherein the upper layer contains platinum supported on an alumina component and rhodium supported on an oxygen storage component, the lower layer contains a front zone and a rear zone, the front zone contains palladium supported on an oxygen storage component and an alumina component and barium oxide, the rear zone contains platinum supported on a ceria component and an alumina component, and the weight ratio of palladium to platinum is in the range of 1.0:0.7 to 1.0:1.

3.

17. A process for preparing a layered catalyst article according to any one of claims 1 to 16, the process comprising preparing a lower slurry for the front zone, depositing the slurry on a substrate to obtain a lower front zone, preparing a lower slurry for the rear zone, depositing the slurry on the substrate to obtain a lower rear zone, preparing an upper slurry, depositing the upper slurry on the lower layer to obtain an upper layer, and subsequently calcining at a temperature in the range of 400 to 700 °C, wherein the step of preparing the slurry comprises a technique selected from incipient wetness impregnation, incipient wetness co-impregnation, and post-addition.

18. An exhaust system for an internal combustion engine, the exhaust system comprising a layered catalyst article according to any one of claims 1 to 16.

19. The system comprises a platinum group metal-based three-way conversion catalyst article and a layered catalyst article according to any one of claims 1 to 16, the platinum group metal-based three-way conversion catalyst article being located downstream from the internal combustion engine, and the layered catalyst article being located downstream in fluid communication with the platinum group metal-based three-way conversion catalyst article. The exhaust system according to claim 18.

20. The system comprises a platinum group metal-based three-way conversion catalyst article and a layered catalyst article according to any one of claims 1 to 16, the layered catalyst article being located downstream from the internal combustion engine, and the platinum group metal-based three-way conversion catalyst article being located downstream in fluid communication with the layered catalyst article. The exhaust system according to claim 18.

21. A method for treating a gaseous exhaust stream containing hydrocarbons, carbon monoxide, and nitrogen oxides, the method comprising contacting the exhaust stream with a layered catalyst article according to any one of claims 1 to 16 or an exhaust system according to any one of claims 18 to 20.

22. A method for reducing the levels of hydrocarbons, carbon monoxide, and nitrogen oxides in a gaseous exhaust stream, the method comprising contacting the gaseous exhaust stream with the layered catalyst article according to any one of claims 1 to 16 or the exhaust system according to any one of claims 18 to 20 to reduce the levels of hydrocarbons, carbon monoxide, and nitrogen oxides in the gaseous exhaust stream. **Claim 23** Use of a layered catalyst article according to any one of claims 1 to 16 for purifying a gaseous exhaust stream containing hydrocarbons, carbon monoxide, and nitrogen oxides.

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