Three-way catalyst system for automobiles containing a tail pipe catalyst

Abstract

The claimed invention relates to an automotive catalyst system that can be used to selectively reduce carbon monoxide. The system includes a first close-coupled three-way conversion catalyst article in fluid communication with an engine exhaust, a catalyst article located downstream of and in fluid communication with the first close-coupled three-way conversion catalyst article, and a tailpipe catalyst article in fluid communication downstream of and arranged 1.0 to 10 feet apart from the catalyst article at a location selected from before or after a resonator, before or after a muffler, between the resonator and the muffler, inside the muffler, inside the resonator, and at the end of the tailpipe.

Description

Technical Field

[0001] Cross - Reference to Related Applications This application claims the benefit of priority to U.S. Provisional Patent Application No. 62 / 863,983, filed on June 20, 2019, and European Patent Application No. 19186977.5, filed on July 18, 2019.

[0002] The claimed invention relates to a catalyst system useful for treating exhaust gas and reducing pollutants contained therein. Specifically, the claimed invention relates to a catalyst system containing a tailpipe catalyst that can be used to selectively reduce carbon monoxide.

Background Art

[0003] Automotive catalysts, such as three - way conversion (TWC) catalysts, have been used for several years to treat exhaust gas streams from internal combustion engines. Three - way conversion catalysts are typically known to oxidize unburned hydrocarbons and carbon monoxide and reduce nitrogen oxides. Among various pollutants, the increasing levels of carbon monoxide observed in tailpipe exhaust gas emissions have, in recent years, been a concern as governments in various countries, such as the United States, have imposed strict restrictions regarding carbon monoxide emissions. That is, the allowable value of CO emissions from the tailpipe is steadily decreasing, which remains a problem for automobile manufacturers. Therefore, non - methane hydrocarbon (NMHC) and NO x values are often the main focus of catalysts, but the CO reduction function is now attracting increasing attention.

[0004] In the prior art, the use of three-way catalysts containing nickel or a combination of nickel and copper to reduce CO and other pollutants has been disclosed. However, the practicality of such catalysts is that both nickel and copper may react with a support such as alumina to form nickel-aluminate and copper-aluminate, which may affect the commercial success of such designs. The formation of each aluminate typically occurs during severe aging conditions and can cause catalyst deactivation. Furthermore, the presence of base metals may cause poisoning of platinum group metals (PGMs) and / or be the cause of low thermal stability. Additionally, since nickel, which reacts with carbon monoxide, may in some cases form toxic nickel tetracarbonyl, there are restrictions on the use of nickel in automotive catalysts in the European Union.

[0005] Therefore, there is a need for a catalyst system that can provide positive results across the entire emission spectrum while selectively targeting CO emissions. Accordingly, an object of the present invention is to provide an automotive catalyst system that uses an optimized additional catalyst, disposed remotely from the engine and used in conjunction with a close-coupled catalyst (CC)-1 and an underfloor catalyst / close-coupled catalyst-2 (CC-2), to minimize the effects of aging, maintain high PGM dispersion, and thereby reduce CO emissions. SUMMARY OF THE INVENTION

[0006] The claimed invention is a. A first close-coupled three-way conversion catalyst article in fluid communication with an engine exhaust port, the three-way conversion catalyst article comprising i) a first platinum group metal supported on a support, and ii) a first substrate, the first close-coupled three-way conversion catalyst article, b. A catalyst article located downstream of and in fluid communication with the first close-coupled three-way conversion catalyst article, the catalyst article comprising i) a second platinum group metal supported on a support, and ii) a second substrate, the catalyst article, c.i) A third platinum group metal and / or a non-platinum group metal supported on one of ceria-zirconia, ceria, ceria-alumina, lanthana-zirconia, alumina-zirconia, a mixture of alumina and ceria, and a mixture of alumina and ceria-zirconia, and ii) a tailpipe catalyst article including a third substrate, an automotive catalyst system comprising: The loading amount of the third platinum group metal is in the range of 1.0 to 20.0 g / ft 3 and the tailpipe catalyst article (c) is selected from a position in front of or behind the resonator, in front of or behind the muffler, between the resonator and the muffler, inside the muffler, inside the resonator, and at the end of the tailpipe and touch downstream in fluid communication with the media article (b) and arranged 1.0 to 10 feet apart, an automotive catalyst system is provided.

[0007] In another aspect, the claimed invention provides a method of treating a gaseous exhaust stream containing hydrocarbons, carbon monoxide, and nitrogen oxides, the method comprising contacting the exhaust stream with a catalyst system according to the claimed invention.

[0008] In still another aspect, the claimed invention provides a method of reducing the levels of hydrocarbons, carbon monoxide, and nitrogen oxides in a gaseous exhaust stream, the method comprising contacting the gaseous exhaust stream with a catalyst system according to the claimed invention.

[0009] In yet another aspect, the claimed invention also provides the use of a catalyst system according to the claimed invention for purifying a gaseous exhaust stream containing hydrocarbons, carbon monoxide, and nitrogen oxides.

Brief Description of the Drawings

[0010] 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 are indicative of components of exemplary embodiments of the present invention. The drawings are illustrative only and are not to be construed as limiting the present invention. The above and other features, their nature, and various advantages of the claimed invention will become more apparent when the following detailed description is considered in conjunction with the accompanying drawings.

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DETAILED DESCRIPTION OF THE INVENTION

[0011] From this point forward, the present invention claimed in the claims is further fully described below. The present invention claimed 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 disclosure will be thorough and complete, and will fully convey the scope of the 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.

[0012] The use of the terms "a", "an", "the", and similar indicators in the context of describing the materials and methods considered herein (particularly in the context of the following claims) should be construed to cover both the singular and the plural unless otherwise indicated herein or clearly contradicted by the context.

[0013] 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, whether or not explicitly indicated, are modified by the term "about". Of course, the values modified by the term "about" include the specific value. For example, "about 5.0" should include 5.0.

[0014] All methods described herein can be performed in any suitable order unless otherwise indicated herein or unless clearly contradicted by the context. The use of any examples or exemplary language provided herein (e.g., "such as") is intended only to better explain the materials and methods and is not limiting of the scope unless otherwise claimed.

[0015] The present invention addresses the problem of controlling high CO emissions from automobiles and provides an automotive catalyst system in which an additional catalyst article can be positioned behind a first close-coupled and underfloor (CC+UF) catalyst or a first close-coupled and a second first close-coupled (CC1+CC2) catalyst configuration. Thus, instead of modifying a close-coupled catalyst where multiple reactions compete around the active sites, the claimed invention places a PGM and / or non-PGM containing catalyst away from the vehicle's engine, thereby minimizing the effects of aging and maintaining a high PGM / non-PGM dispersion to provide an effective solution for controlling CO emissions. Such a catalyst in the context of the present invention is referred to as a tailpipe catalyst and is arranged downstream and away from a catalyst article (CC2 / UF) at a particular location, for example, in front of or behind a resonator, in front of or behind a muffler, between a resonator and a muffler, inside a muffler, inside a resonator, and at the end of a tailpipe.

[0016] The tailpipe catalyst article has been found to selectively convert CO, which is mainly a breakthrough during vehicle acceleration. In one embodiment, the tailpipe catalyst has a very low PGM loading (1-10 g / ft 3) It is prepared using. That is, the amount of PGM in the tailpipe catalyst is less than 10% of the total PGM present in the CC1 and CC2 (or UF) catalysts. In one embodiment, the catalyst system contains an additional catalyst article (tailpipe catalyst article), but may have the same total PGM loading as a conventional catalyst system containing CC1 and UF / CC2 in terms of PGM loading. The platinum group metals utilized in the tailpipe catalyst can be a minor fraction taken from the CC catalyst article. Redistribution or substitution of PGM (e.g., substituting Pt with Pd) is carried out so that the total PGM cost of the system is equivalent. The tailpipe catalyst has been demonstrated not to have an adverse effect on THC and NO emissions. The tailpipe (TP) catalyst functions as a water gas shift (WGS) catalyst and mainly converts CO and water into CO2 and hydrogen. Since the WGS catalyst does not rely on oxygen, it can operate behind the oxygen-consuming TWC+TWC system.

[0017] The main focus of the claimed invention is to address CO emissions during a typical driving cycle. This is particularly important when the engine is operating rich and the efficiency of the CC+UF system is not sufficient to reduce "hot emissions", for example, when the engine is operating under stoichiometric mode or rich mode, that is, when the air / fuel ratio is 1 or less, or when it is not sufficient to reduce the CO breakthrough during vehicle acceleration, especially during rapid vehicle acceleration. The placement of the tailpipe is related to the optimal operating temperature range of the WGS reaction occurring on the catalyst. Therefore, its placement can be anywhere between just behind the floor and the tip of the tailpipe and is influenced by the bed temperature. Additionally, the tailpipe catalyst can be placed in front of the muffler or also within the muffler assembly. The operating mode and chemical action determine the placement of the tailpipe catalyst.

[0018] In one embodiment, the automotive catalyst system is (a) A first close-coupled three-way conversion catalyst article in fluid communication with an engine exhaust port, the three-way conversion catalyst article comprising i) a first platinum group metal supported on a support, and ii) a first substrate, the first close-coupled three-way conversion catalyst article, (b) A catalyst article located downstream of and in fluid communication with the first close-coupled three-way conversion catalyst article, the catalyst article comprising i) a second platinum group metal supported on a support, and ii) a second substrate, the catalyst article, (c) A tailpipe catalyst article comprising i) a third platinum group metal and / or a non-platinum group metal supported on one of ceria-zirconia, ceria, ceria-alumina, lanthana-zirconia, alumina-zirconia, a mixture of alumina and ceria, and a mixture of alumina and ceria-zirconia, and ii) a third substrate, The loading of the third platinum group metal, if present, is in the range of 1.0 to 10.0 g / ft 3 and, The tailpipe catalyst article (c) is arranged downstream in fluid communication with the catalyst article (b) and is spaced 1.0 to 10 feet apart. and touch and is arranged downstream in fluid communication with the catalyst article (b) and is spaced 1.0 to 10 feet apart.

[0019] In one embodiment, the amount of the third platinum group metal is less than 10 wt% of the total amount of platinum group metals present in the catalyst system, i.e., the amount of the third platinum group metal is less than 10 wt% of the total amount of the first, second, and third platinum group metals. In one embodiment, the amount of the third platinum group metal is less than 5.0 wt% of the total amount of platinum group metals present in the catalyst system.

[0020] The terms "catalyst", "catalytic article", or "catalyst article" refer to a component in which a substrate is coated with a catalyst composition used to promote a desired reaction. In one embodiment, the catalyst article is a layered catalyst article. The term "layered catalyst article" refers to a catalyst article in which a substrate is layered with a PGM composition. These compositions may be referred to as washcoats.

[0021] The platinum group metals (PGM) refer to any component containing PGM (Ru, Rh, Os, Ir, Pd, and Pt). 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 components" 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 firing or use of the catalyst or are otherwise converted to the catalytically active form, usually a metal or metal oxide.

[0022] The term "NO x " refers to nitrogen oxide compounds such as NO and / or NO2.

[0023] The platinum group metals are supported or impregnated on a support material such as an alumina component, a ceria component, a zirconia component, and an oxygen storage component. As used herein, "impregnated" or "impregnation" refers to permeating a catalyst material into the porous structure of a support material.

[0024] The "support" in a catalyst material, catalyst composition, or catalyst washcoat refers to a material that receives metals (e.g., PGM), stabilizers, promoters, binders, etc. by precipitation, association, dispersion, impregnation, or other suitable methods. Exemplary supports include heat-resistant metal oxide supports as described hereinbelow.

[0025] The "refractory metal oxide support" includes, for example, bulk alumina, ceria, zirconia, titania, silica, magnesia, neodymia, and other materials known for such use, as well as physically mixed or chemically combined metal oxides containing atom-doped combinations and active compounds such as high surface area or activated alumina.

[0026] Exemplary combinations of metal oxides include alumina - zirconia, alumina - ceria - zirconia, lanthana - alumina, lanthana - zirconia - alumina, baria - alumina, baria - lanthana - alumina, barialanthana - neodymia alumina, and alumina - ceria. Exemplary aluminas include macroporous boehmite, gamma - alumina, and delta / theta alumina. Useful commercial aluminas used as starting materials in exemplary processes include high bulk density gamma - alumina, low or medium bulk density macroporous gamma - alumina, and activated aluminas such as low bulk density macroporous boehmite and gamma - alumina. Such materials are generally considered to provide durability to the resulting catalyst.

[0027] The term "high surface area refractory metal oxide support" specifically refers to support particles having pores larger than 20 Å and a broad pore distribution. High surface area heat - resistant metal oxide supports, for example, alumina support materials also referred to as "gamma alumina" or "activated alumina", typically exhibit a BET surface area of more than 60 square meters per gram ("m 2 / g"), often about 300 m 2 / g or more for fresh materials. Such activated alumina is usually a mixture of the gamma and delta phases of alumina, but may also contain significant amounts of the eta, kappa, and theta alumina phases.

[0028] As used herein, the term "oxygen storage component" (OSC) refers to an entity that has multiple valence states and can actively react with a reducing agent such as carbon monoxide (CO) and / or hydrogen under reducing conditions and then react with an oxidizing agent such as oxygen or nitrogen oxides under oxidizing conditions. Examples of oxygen storage components include pre-transition metal oxides, particularly ceria composites optionally doped with zirconia, lanthana, praseodymia, neodymia, niobia, europia, samaria, ytterbia, yttria, and mixtures thereof.

[0029] In one embodiment, 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, and the amount of the oxygen storage component is 20 to 80 wt% based on the total weight of the first layer or the second layer. In one exemplary embodiment, the oxygen storage component comprises ceria-zirconia.

[0030] In one embodiment, the alumina component comprises alumina, lanthana-alumina, ceria-alumina, ceria-zirconia-alumina, zirconia-alumina, lanthana-zirconia-alumina, baria-alumina, baria-lanthana-alumina, baria-lanthana-neodymia-alumina, or a combination thereof.

[0031] In one embodiment, the oxygen storage component comprises ceria in an amount of 5.0 to 50 wt% based on the total weight of the oxygen storage component. In one embodiment, the oxygen storage component of the first layer comprises ceria in an amount of 20.0 to 50.0 wt% based on the total weight of the oxygen storage component. In one embodiment, the oxygen storage component of the second layer comprises ceria in an amount of 5.0 to 15.0 wt% based on the total weight of the oxygen storage component.

[0032] In the context of the present invention, the term zirconia component refers to a zirconia-based support stabilized or promoted by lanthanum or barium or ceria. Examples include lanthanum-zirconia and barium-zirconia.

[0033] In one embodiment, the ceria component comprises ceria or stabilized ceria having a cerium oxide content of at least 85 wt%, and the ceria component optionally includes a dopant selected from zirconia, yttria, praseodymia, lanthanum, neodymia, samaria, gadolinia, alumina, titania, barium, strontia, and combinations thereof, and the amount of the dopant is 1.0 to 20.0 wt% based on the total weight of the ceria component.

[0034] In one embodiment, the first, second, or third platinum group metal is platinum, palladium, rhodium, or any combination thereof.

[0035] In one embodiment, the loading of the first platinum group metal is in the range of 50 to 300 g / ft 3 . In one embodiment, the loading of the second platinum group metal is 1.0 g / ft 3 and 50.0 g / ft 3 . In one embodiment, the loading of the third platinum group metal is 1.0 to 10.0 g / ft 3 . In one embodiment, the loading of the third platinum group metal is 1.0 to 5.0 g / ft 3 . In one embodiment, the loading of the third platinum group metal is 3 g / ft 3 . In one embodiment, the third platinum group metal is platinum. In one embodiment, the third platinum group metal is palladium. In one embodiment, the third platinum group metal is rhodium.

[0036] In one embodiment, the automotive catalyst system is a) a first close-coupled three-way conversion catalyst article in fluid communication with the engine exhaust port, the article having 50 to 300 g / ft supported on a support 3A first close-coupled three-way conversion catalyst article comprising a first platinum group metal and a first substrate, b) A catalyst article located downstream of and in fluid communication with the first close-coupled three-way conversion catalyst article, the article comprising 1 g / ft supported on a support 3 ~50 g / ft 3 of a second platinum group metal and a second substrate, c) i) A tailpipe catalyst article comprising 1.0 - 10 g / ft supported on one of ceria-zirconia, ceria, ceria-alumina, lanthana-zirconia, alumina-zirconia, a mixture of alumina and ceria, and a mixture of alumina and ceria-zirconia of a third platinum group metal and / or a non-platinum group metal, and ii) a third substrate, 3 wherein the tailpipe catalyst article (c) is arranged downstream in fluid communication with the catalyst article (b) and spaced 1.0 - 10 feet apart. The tailpipe catalyst article (c) is located at a position selected from in front of or behind the resonator, in front of or behind the muffler, between the resonator and the muffler, inside the muffler, inside the resonator, and at the end of the tailpipe and touch downstream in fluid communication with the catalyst article (b) and spaced 1.0 - 10 feet apart.

[0037] In one embodiment, an automotive catalyst system comprises a) A first close-coupled three-way conversion catalyst article in fluid communication with an engine exhaust port, the article comprising 50 - 300 g / ft supported on a support 3 of a first platinum group metal and a first substrate, b) A catalyst article located downstream of and in fluid communication with the first close-coupled three-way conversion catalyst article, the article comprising 1 g / ft supported on a support 3 ~50 g / ft 3 of a second platinum group metal and a second substrate, c) i) A tailpipe catalyst article comprising 1.0 - 10 g / ft supported on one of ceria-zirconia, ceria, ceria-alumina, lanthana-zirconia, alumina-zirconia, a mixture of alumina and ceria, and a mixture of alumina and ceria-zirconia of a third platinum group metal and / or a non-platinum group metal, and ii) a third substrate, 3a third platinum group metal and / or a non-platinum group metal, and ii) a tailpipe catalyst article comprising a third substrate, wherein the amount of the third platinum group metal is less than 5.0 wt% of the total amount of platinum group metals present in the catalyst system, The tailpipe catalyst article (c) is located at a position selected from in front of or behind the resonator, in front of or behind the muffler, between the resonator and the muffler, inside the muffler, inside the resonator, and at the end of the tailpipe and downstream and in fluid communication with the catalyst article (b) and arranged 1.0 to 10 feet apart.

[0038] In one embodiment, the ceria-zirconia contains 5.0 to 60 wt% cerium oxide, the ceria-alumina contains 1.0 to 40 wt% cerium oxide, the lanthana-zirconia contains 70 to 99 wt% zirconia, and the alumina-zirconia contains 1 to 40 wt% zirconia.

[0039] In one embodiment, the catalyst article (b) is an underfloor catalyst article or a second close-coupled catalyst article. In one exemplary embodiment, an automotive catalyst system of the claimed invention including an engine (22), a close-coupled catalyst article (CC1, 24), an underfloor catalyst article (26), and a tailpipe catalyst article (28) arranged downstream and spaced apart from the underfloor catalyst article (26) is shown in FIG. 1B. A reference catalyst system is shown in FIG. 1A including an engine (22), a close-coupled catalyst article (CC1, 24), and an underfloor catalyst article (26).

[0040] In one embodiment, the first close-coupled three-way conversion catalyst article (a) and / or the catalyst article (b) is a single-layer or two-layer catalyst article. In one embodiment, the first close-coupled three-way conversion catalyst article (a) and / or the catalyst article (b) is a single-layer catalyst article including a front zone and a rear zone.

[0041] In one embodiment, the first close-coupled three-way conversion catalyst article (a) and / or the catalyst article (b) is a two-layer catalyst article including a bottom layer and a top layer, and the bottom layer and / or the top layer include a front zone and a rear zone.

[0042] In one embodiment, the tailpipe catalyst article comprises a non-platinum group metal selected from nickel, copper, iron, manganese, zinc, titanium, vanadium, chromium, or combinations thereof, supported on a support selected from a ceria component, a zirconia component, and an oxygen storage component. The loading of the non-platinum group metal is in the range of 0.1 to 20 wt% or 10 to 500 g / ft 3 . The non-platinum group metal can be used alone in the tailpipe catalyst in place of the PGM or can be used in combination with the PGM. As an example, separating the non-platinum group metal(s), e.g., nickel and / or copper, away from the engine can reduce exposure to severe aging conditions and thereby reduce catalyst deactivation. In one embodiment, a combination of nickel (Ni) and copper (Cu) is used. In one embodiment, the amount of nickel used is 5.0 to 15 wt% and the amount of copper used is 0.2 to 1.0 wt%. In one preferred embodiment, the amount of nickel used is 10 wt% and the amount of copper used is 0.5 wt%. Further, using a support such as a ceria component, a zirconia component, and an oxygen storage component in addition to or instead of the alumina component can limit or completely prevent the formation of less active non-platinum group metal mixed oxides such as nickel-aluminate and copper-aluminate. Still further, separating the non-platinum group metals from each other can avoid the possibility of poising of the PGM.

[0043] 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 composition disposed on the monolithic material.

[0044] Reference to a "monolithic substrate" or "honeycomb substrate" means a single, homogeneous, and continuous structure from an inlet to an outlet.

[0045] As used herein, the term "washcoat" has its ordinary meaning in the art of thin adherent coatings of catalysts 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.

[0046] 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 monolith substrate or a lower washcoat layer. In one embodiment, the substrate contains one or more washcoat layers, and each washcoat layer is different in some way (e.g., can differ in its physical properties such as particle size or crystallite phase, etc.) and / or can have a different chemical catalytic function.

[0047] A catalytic article may be "unused", which means that the catalytic article 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" catalytic 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).

[0048] According to one or more embodiments, the substrate of the claimed catalyst article of the present invention can be constructed of any material typically used to prepare automotive catalysts, and typically includes 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 woven fiber substrate. In one embodiment, the density of the substrate is less than 400 cpsi.

[0049] The substrate typically provides a plurality of walls to which a washcoat containing the catalyst composition described hereinabove is applied and adhered, thereby acting as a carrier for the catalyst composition.

[0050] 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 may advantageously be at least 15 wt% of the alloy, for example, 10 - 25 wt% chromium, 3 - 8 wt% aluminum, and up to 20 wt% 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 may 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 substrate and facilitating the adhesion of the washcoat layer to the metal surface.

[0051] Examples of ceramic materials used to construct 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.

[0052] 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 to an outlet surface of the substrate so that the passage is open to 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 so 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 a wall thickness of 6 mils at 400 cpsi or 4 mils at 600 cpsi. However, it will be understood that the present invention is not limited to a particular substrate type, material, or shape. In an alternative embodiment, the substrate may be a wall-flow substrate 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 in order to reach the outlet. Such monolithic substrates 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. Wall-flow substrates typically have 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 with 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.

[0053] As used herein, the term "flow" broadly refers to any combination of flowing gases that may contain particulate matter of solids or liquids.

[0054] As used herein, the terms "upstream" and "downstream" refer to the relative directions according to the flow of the engine exhaust gas flow 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.

[0055] Figures 8A and 8B illustrate an exemplary substrate 2 in the form of a flow-through substrate coated with the washcoat composition described herein. Referring to FIG. 8A, 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 that is 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 FIG. 8B, the flow paths 10 are formed by walls 12 and extend through the substrate 2 from the upstream end face 6 to the downstream end face 8, and the passages 10 are not blocked so as to allow the flow of fluid, e.g., the flow of gas, to pass longitudinally through the substrate 2 via the gas flow paths 10 of the substrate. As more readily appreciated in FIG. 8B, 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 separate 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 claimed invention is also practiced with two or more (e.g., three or four) washcoat layers and is not limited to the two-layer embodiment shown.

[0056] Figure 9 illustrates an exemplary substrate 2 in the form of a wall flow filter substrate coated with the washcoat composition described herein. As can be seen in Figure 9, the exemplary substrate 2 has a plurality of flow channels 52. The channels 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 alternating channels are blocked at the inlet end by an inlet plug 58 and at the outlet end by an outlet plug 60 to form a checkerboard pattern that is reversed at the inlet 54 and outlet 56. The gas flow 62 enters through the unblocked channel inlet 64, is stopped by the outlet 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 flow filter used in the present invention has catalytic activity on the walls of the element that have or contain one or more catalyst materials on or in it. The catalyst 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 catalyst material. The present invention includes the use of one or more catalyst material layers on the inlet wall and / or the outlet wall of the element.

[0057] In one exemplary embodiment, the automotive catalyst system is a) a first close-coupled three-way conversion catalyst article in fluid communication with the engine exhaust port, the article comprising i) a bottom layer containing 50-100 g / ft 3 of palladium supported on an alumina component and an oxygen storage component, ii) a top layer containing 1.0-50 g / ft 3 of rhodium supported on an alumina component, and iii) a first substrate, b) a underfloor catalyst article located downstream of and in fluid communication with the first close-coupled three-way conversion catalyst article, the article comprising i) 1.0 g / ft 3 - 5.0 g / ft 3 of rhodium supported on an alumina component and an oxygen storage component, and ii) a second substrate, the underfloor catalyst article, c) i) 1.0 - 5.0 g / ft 3comprising a tailpipe catalyst article comprising platinum and ii) a third substrate, wherein the tailpipe catalyst article (c) is located at a position selected from in front of or behind the resonator, in front of or behind the muffler, between the resonator and the muffler, inside the muffler, inside the resonator, and the end of the tailpipe and touch downstream and in fluid communication with the media article (b) and arranged 1.0 to 10 feet apart.

[0058] In another exemplary embodiment, an automotive catalyst system a) a first close-coupled three-way conversion catalyst article in fluid communication with the engine exhaust port, the article comprising i) a bottom layer comprising 50 to 100 g / ft 3 of palladium supported on an alumina component and an oxygen storage component, ii) a top layer comprising 1.0 to 50 g / ft 3 of rhodium supported on an alumina component, and iii) a first substrate, b) an underfloor catalyst article located downstream of and in fluid communication with the first close-coupled three-way conversion catalyst article, the article comprising i) 1.0 g / ft 3 to 5.0 g / ft 3 of rhodium, and ii) a second substrate, an underfloor catalyst article, c) comprising a tailpipe catalyst article comprising i) 1.0 to 5.0 g / ft 3 of palladium supported on ceria-alumina, and ii) a third substrate, wherein the tailpipe catalyst article (c) is located at a position selected from in front of or behind the resonator, in front of or behind the muffler, between the resonator and the muffler, inside the muffler, inside the resonator, and the end of the tailpipe and touch downstream and in fluid communication with the media article (b) and arranged 1.0 to 10 feet apart.

[0059] In another exemplary embodiment, an automotive catalyst system a) a first close-coupled three-way conversion catalyst article in fluid communication with the engine exhaust port, the article comprising i) a bottom layer comprising 50 to 100 g / ft3 i) a bottom layer containing palladium, ii) a top layer containing rhodium supported on an alumina component at 1.0 to 50 g / ft 3 , and a first substrate, b) a underfloor catalyst article located downstream of and in fluid communication with the first close-coupled three-way conversion catalyst article, the article comprising i) 1.0 g / ft 3 to 5.0 g / ft 3 of rhodium supported on an alumina component and an oxygen storage component, and ii) a second substrate, c) a tailpipe catalyst article comprising i) 1.0 to 5.0 g / ft 3 of rhodium supported on ceria-alumina, and ii) a third substrate, wherein the tailpipe catalyst article (c) is arranged downstream and in fluid communication with the underfloor catalyst article (b) and is spaced 1.0 to 10 feet apart at a position selected from in front of or behind a resonator, in front of or behind a muffler, between a resonator and a muffler, inside a muffler, inside a resonator, and at the end of a tailpipe. and touch

[0060] In another exemplary embodiment, an automotive catalyst system comprises a) a first close-coupled three-way conversion catalyst article in fluid communication with an engine exhaust port, the article comprising i) a bottom layer containing 50 to 100 g / ft 3 of palladium supported on an alumina component and an oxygen storage component, ii) a top layer containing 1.0 to 50 g / ft 3 of rhodium supported on an alumina component, and iii) a first substrate, b) a underfloor catalyst article located downstream of and in fluid communication with the first close-coupled three-way conversion catalyst article, the article comprising i) 1.0 g / ft 3 to 5.0 g / ft 3 of rhodium supported on an alumina component and an oxygen storage component, and ii) a second substrate, c) a tailpipe catalyst article comprising i) 0.5 wt% CuO and 10 wt% NiO supported on ceria and lanthana-zirconia, and ii) a third substrate, The tailpipe catalyst article (c) is located at a position selected from in front of or behind the resonator, in front of or behind the muffler, between the resonator and the muffler, inside the muffler, inside the resonator, and the end of the tailpipe and touch downstream in fluid communication with the media article (b) and arranged 1.0 to 10 feet apart.

[0061] In one exemplary embodiment, an automotive catalyst system a) a first close-coupled three-way conversion catalyst article in fluid communication with the engine exhaust port, the article comprising i) a bottom layer containing 90 to 100 g / ft 3 of palladium supported on an alumina component and an oxygen storage component, ii) a top layer containing 1 to 10 g / ft 3 of rhodium supported on an alumina component, and iii) a first substrate, b) a underfloor catalyst article located downstream of and in fluid communication with the first close-coupled three-way conversion catalyst article, the article comprising i) 1.0 g / ft 3 to 5.0 g / ft 3 of rhodium, and ii) a second substrate, the underfloor catalyst article, c) a tailpipe catalyst article comprising i) 1.0 to 5.0 g / ft 3 of platinum supported on ceria-alumina, and ii) a third substrate, The tailpipe catalyst article (c) is located at a position selected from in front of or behind the resonator, in front of or behind the muffler, between the resonator and the muffler, inside the muffler, inside the resonator, and the end of the tailpipe and touch downstream in fluid communication with the media article (b) and arranged 1.0 to 10 feet apart.

[0062] In one exemplary embodiment, an automotive catalyst system a) a first close-coupled three-way conversion catalyst article in fluid communication with the engine exhaust port, the article comprising i) a bottom layer containing 90 to 100 g / ft 3 of palladium supported on an alumina component and an oxygen storage component, ii) a top layer containing 1.0 to 10 g / ft3 the top layer containing rhodium, and iii) a first substrate, b) a underfloor catalyst article located downstream of and in fluid communication with the first tightly coupled three-way conversion catalyst article, the article comprising i) 1.0 g / ft supported on an alumina component and an oxygen storage component 3 ~5.0 g / ft 3 of rhodium, and ii) a second substrate, the underfloor catalyst article, c) i) 1.0 - 5.0 g / ft supported on ceria-alumina 3 of palladium, and ii) a tailpipe catalyst article comprising a third substrate, the tailpipe catalyst article (c) is located in front of or behind the resonator, in front of or behind the muffler, between the resonator and the muffler, inside the muffler, inside the resonator, and at a position selected from the end of the tailpipe and touch downstream in fluid communication with the media article (b) and arranged 1.0 - 10 feet apart.

[0063] In another exemplary embodiment, the automotive catalyst system a) a first tightly coupled three-way conversion catalyst article in fluid communication with the engine exhaust port, the article comprising i) a bottom layer containing 90 - 100 g / ft of palladium supported on an alumina component and an oxygen storage component, ii) a top layer containing 1.0 - 10 g / ft of rhodium supported on an alumina component, and iii) a first substrate, 3 and iii) a first substrate, 3 of rhodium, and iii) a first substrate, b) a underfloor catalyst article located downstream of and in fluid communication with the first tightly coupled three-way conversion catalyst article, the article comprising i) 1.0 g / ft supported on an alumina component and an oxygen storage component 3 ~5.0 g / ft 3 of rhodium, and ii) a second substrate, the underfloor catalyst article, c) i) 0.5 wt% CuO and 10 wt% NiO supported on ceria and lanthana-zirconia, and ii) a tailpipe catalyst article comprising a third substrate, The tailpipe catalyst article (c) is at a location selected from in front of or behind the resonator, in front of or behind the muffler, between the resonator and the muffler, inside the muffler, inside the resonator, and at the end of the tailpipe and touch downstream in fluid communication with the media article (b) and arranged 1.0 to 10 feet apart.

[0064] A process for preparing a first close-coupled three-way conversion catalyst article is also provided. In one embodiment, the process includes preparing a slurry of a first layer, depositing the slurry of the first layer on a substrate to obtain a first layer, preparing a slurry of a second layer, and depositing the slurry of the second layer on the first layer to obtain a second layer followed by firing at a temperature in the range of 400 - 700 °C. The step of preparing the slurry of the first layer or the slurry of the second layer includes a technique selected from incipient wetness impregnation, incipient wetness co-impregnation, and post-addition. In one embodiment, the process includes a pre-step of thermally or chemically fixing platinum and / or palladium on a support.

[0065] Thermal fixation involves, for example, depositing the PGM on the support via an incipient wetness impregnation method followed by thermal firing of the resulting PGM / support mixture. As an example, the mixture is fired at 400 - 700 °C for 1.0 - 3.0 hours at a ramp rate of 1.0 - 25 °C / min.

[0066] Chemical fixation involves depositing PGM on a support and subsequently chemically converting the PGM using additional reagents. As an example, aqueous palladium nitrate is impregnated onto alumina. Instead of drying or calcining the impregnated powder, it is instead added to an aqueous solution of barium hydroxide. As a result of the addition, acidic palladium nitrate reacts with basic barium hydroxide to obtain water-insoluble palladium hydroxide and barium nitrate. Thus, Pd is chemically fixed as an insoluble component in the pores and on the surface of the alumina support. Alternatively, the support can first be impregnated with an acidic component and subsequently with a second basic component. The chemical reaction between the two reagents deposited on a support, e.g., alumina, leads to the formation of an insoluble or nearly insoluble compound that also deposits in the pores and on the surface of the support.

[0067] The incipient wetness impregnation technique, also referred to 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 a 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 addition of a solution in excess of the pore volume of the support causes the solution transport to change from a capillary action process to a much slower diffusion process. The catalyst is dried and calcined to remove the volatile components in the solution and deposit the metal on the surface of the catalyst support. The concentration profile of the impregnated material depends on the mass transfer conditions in the pores during impregnation and drying. After being appropriately diluted, 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.

[0068] 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 utilized. After treatment of the support particles with the active metal solution, the particles are dried by heat treatment, etc. at a high temperature (e.g., 100 - 150 °C) for a certain period of time (e.g., 1.0 - 3.0 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 3.0 hours. If necessary, the above process can be repeated by means of impregnation to reach the desired filling level of the active metal.

[0069] The above 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 diacetate, 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, and silica sol. When present, the binder is typically used in an amount of about 1.0 - 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, aqueous nitric acid, or acetic acid. The typical pH range of the slurry is about 3 - 12.

[0070] The slurry may be pulverized to reduce the particle size and promote the mixing of the particles. The pulverization is achieved with a ball mill, a continuous mill, or other similar equipment, and the solid content of the slurry can be, for example, about 20 to 60% by weight, more specifically, about 20 to 40% by weight. In one embodiment, the pulverized slurry has a D of about 3 to about 40 micrometers, preferably 10 to about 30 micrometers, more preferably about 10 to about 15 micrometers. 90 characterized by the particle size. The 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. Typically, the D in micrometers 90 means that 90% of the number of particles have a diameter smaller than the quoted value.

[0071] Any washcoat technology known in the art is used to coat the slurry onto the catalyst substrate. In one embodiment, the catalyst substrate is immersed one or more times in the slurry or otherwise coated with the slurry. Thereafter, the coated substrate is dried at a high temperature (e.g., 100 to 150 °C) for a certain period of time (e.g., 10 minutes to 3.0 hours), and then fired, for example, at 400 to 700 °C, typically for about 10 minutes to 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 necessary to build up the coating to the desired loading level or thickness, i.e., two or more washcoats may be applied.

[0072] In certain embodiments, the coated substrate is aged by subjecting the coated substrate to a heat treatment. In one embodiment, the aging is performed by alternately supplying hydrocarbon / air at a temperature of about 850 °C to about 1050 °C for 50 to 75 hours in an environment of 10% by volume of moisture. Accordingly, in certain embodiments, an aged catalyst article is provided. In one embodiment, a particularly effective material is a metal oxide-based support (including, but not limited to, a substantially 100% ceria support) that maintains a high percentage (e.g., about 95 - 100%) of pore volume during aging (e.g., aging at about 850 °C to about 1050 °C with alternate hydrocarbon / air supply, 10% by volume of moisture, 50 - 75 hours).

[0073] A process for preparing a underfloor catalyst article is also provided. In one embodiment, the process includes preparing a slurry using supports such as alumina and OSC, and adding PGM to the slurry to form a washcoat. In one embodiment, the slurry is milled after all components are added and coated as a layer on a cordierite substrate.

[0074] A process for preparing a tailpipe catalyst article is also provided. In one embodiment, the process includes preparing a slurry using one or more supports such as alumina and OSC, adding PGM to the slurry to form a washcoat, and depositing the washcoat on a substrate.

[0075] In one aspect, the claimed invention 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 catalyst system or an exhaust system according to the claimed invention. The terms "exhaust stream", "engine exhaust stream", "exhaust gas stream", etc. refer to any combination of flowing engine effluent gas 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.

[0076] In another aspect, the claimed invention 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 catalyst system or an exhaust system according to the claimed invention to reduce the levels of hydrocarbons, carbon monoxide, and nitrogen oxides in the exhaust gas. In one embodiment, a method for reducing the level of carbon monoxide in a gaseous exhaust stream is provided, which includes contacting the gaseous exhaust stream with a catalyst system or an exhaust system according to the claimed invention.

[0077] In yet another aspect, the claimed invention also provides the use of the catalyst system of the claimed invention for purifying a gaseous exhaust stream containing hydrocarbons, carbon monoxide, and nitrogen oxides.

[0078] In some embodiments, the catalyst system 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 nitrous oxide present in the exhaust gas stream prior to contacting the catalyst system. In some embodiments, the catalyst system converts hydrocarbons to carbon dioxide and water. In some embodiments, the catalyst system 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 prior to contacting the catalyst system. In some embodiments, the catalyst article converts carbon monoxide to carbon dioxide. In some embodiments, the catalyst system converts nitrogen oxides to nitrogen.

[0079] 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 prior to 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 prior to contacting the catalyst article.

[0080] In another aspect, there is provided the use of the claimed catalyst system of the present invention for purifying a gaseous exhaust stream containing hydrocarbons, carbon monoxide, and nitrogen oxides.

Examples

[0081] Aspects of the claimed invention are more fully shown by the following examples, which are set forth to illustrate certain aspects of the invention and should not be construed as limiting thereof.

[0082] Example 1 (Reference Catalyst System: CC1 + UF) A. Preparation of the CC1 Catalyst Article: A Pd / Rh-based CC1 TWC catalyst article was prepared and used as a close-coupled reference catalyst article. The total PGM loading (Pt / Pd / Rh) was 0 / 96 / 4. The bottom coat contains 96 g / ft 3 of Pd, or 100% of the total Pd in the catalyst article. The top coat contains 4 g / ft 3 of Rh, or 100% of the total Rh in the catalyst article. The bottom coat has a washcoat loading of 2.583 g / inch 3 and the top coat has a washcoat loading of 1.002 g / inch 3 .

[0083] The bottom coat was prepared by impregnating 321 grams of alumina with a 50% Pd nitrate solution (35.65 grams, 27% Pd nitrate aqueous solution) and impregnating 454 grams of ceria-zirconia with a 50% Pd nitrate solution (35.65 grams, 27% Pd nitrate aqueous solution).

[0084] The alumina portion was chemically fixed by adding the Pd / alumina mixture to an aqueous solution of 173 grams of barium acetate in water. 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 slurry components were then blended.

[0085] The top coat was prepared by impregnating 779 grams of alumina with a mixture of 20.7 grams of rhodium nitrate (10% Rh content) in 720 grams of water. The resulting powder was then mixed with 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.

[0086] The catalyst article was prepared by first coating a bottom coat slurry onto a ceramic substrate. The resulting coated substrate was then dried and fired at 500 °C for 2 hours. Subsequently, the top coat slurry was applied. The resulting product was fired again at 500 °C for 2 hours. The reference catalyst article (RC-CC1) is shown in Figure 1C.

[0087] B. Preparation of Reference UF Catalyst Article The reference UF catalyst article is a rhodium-based single-layer catalyst. The PGM loading was 0 / 0 / 3 g / ft of Pt / Pd / Rh, respectively. 3 The washcoat loading was 2.8 g / inch 3 A slurry was prepared using OSC (40% ceria) and alumina in a 1:2 ratio. 25.7 grams of barium acetate, 30 grams of strontium acetate, and 8 grams of zirconyl acetate were mixed with water and 1000 grams of the support. 6.3 grams of rhodium nitrate solution containing 9.8 wt% rhodium and 25 grams of barium acetate were added to the slurry to form a washcoat. No impregnation or pre-firing of the PGM was performed. After adding all the components, the slurry was milled. The milled (D less than 16 μm 90 ) slurry was coated as a layer on a cordierite substrate. The catalyst article (UF) is shown in Figure 1D.

[0088] Example 2 (Catalyst System A of the Invention: CC1 + UF + Pt-based Tailpipe Catalyst Article A) Preparation of Pt-based Tailpipe Catalyst Article Tailpipe catalyst article A was prepared by mixing 4.25 grams of 14.3% platinum nitrate solution with 606 grams of ceria, 71.4 grams of alumina, 176.61 grams of 19.8% alumina binder solution, and 696 grams of water. The pH of the resulting mixture was lowered to 4 - 5 with nitric acid if necessary. Subsequently, the mixture was D less than 16 μm 90It was pulverized until. The obtained slurry was wash-coated onto a ceramic substrate. This tail pipe catalyst article was used in combination with CC1 and UF prepared according to Example 1. The tail pipe catalyst article is shown in FIG. 1E. The PGM loading is 3 / 0 / 0 g / ft for Pt / Pd / Rh, respectively 3 is. The wash-coat loading is 2.0 g / inch 3 is.

[0089] Example 3 (invention system B: CC1 + UF + Pd-based tail pipe catalyst article B) Preparation of Pd-based tail pipe catalyst article Tail pipe catalyst article B was prepared by mixing 2.16 grams of 28.1% palladium nitrate solution with 339 grams of OSC (40% ceria content), 339 grams of lanthanum-stabilized alumina, 176.61 grams of 19.8% alumina binder solution, and 696 grams of water. The pH of the obtained mixture was lowered to 4 - 5 with nitric acid as necessary. Subsequently, the mixture was pulverized to D less than 16 μm 90 until. The obtained slurry was wash-coated onto a ceramic substrate. The PGM loading is 0 / 3 / 0 g / ft for Pt / Pd / Rh, respectively 3 is. The wash-coat loading is 2.0 g / inch 3 is.

[0090] Example 4 (invention system C: CC1 + UF + Pd-based tail pipe catalyst article C) Preparation of Rh-based tail pipe catalyst article C Tail pipe catalyst article C was prepared by mixing 6.12 grams of 9.9% palladium nitrate solution with 606 grams of OSC (10% ceria content), 71 grams of lanthanum-stabilized alumina, 176.61 grams of 19.8% alumina binder solution, and 696 grams of water. The pH of the obtained mixture was lowered to 4 - 5 with nitric acid as necessary. Subsequently, the mixture was pulverized to D less than 16 μm 90 until. The obtained slurry was wash-coated onto a ceramic substrate. The PGM loading is 0 / 0 / 3 g / ft for Pt / Pd / Rh, respectively3 It is. The washcoat filling amount is 2.0 g / inch 3 It is.

[0091] Example 5 (Invention Series D: CC1 + UF + Cu / Ni Series Tailpipe Catalyst Article D) Preparation of 0.5% CuO and 10% NiO Series Tailpipe Catalysts The PGM-free tailpipe catalyst was prepared by mixing 761.9 grams of ceria, 13.1 grams of copper nitrate (34.2% CuO), 127 grams of lanthana-zirconia, 127 grams of 19.5% alumina binder solution, 395.5 grams of nickel nitrate (25.17% NiO), and 1075 grams of water. The pH of the resulting mixture was lowered to 4 - 5 using nitric acid as needed. The mixture was ground to less than 16 μm D 90 and then the resulting slurry was coated onto a ceramic substrate. The PGM filling amounts are 0 / 0 / 0 g / ft for Pt / Pd / Rh respectively 3 It is. The washcoat filling amount is 4.0 g / inch 3 It is.

[0092] Example 6 (Aging and Testing) All catalyst articles were coated onto a 4.16 × 1.5 inch 600 / 3.5 cordierite substrate. The CC1 and UF catalyst articles were aged using a reactor that operates such that samples are exposed to an alternating lean / rich gas feed at an inlet temperature of 950°C for 12 hours. The tailpipe catalyst was aged using the same protocol but at an inlet temperature of 600°C. The latter temperature was experimentally measured as a result of the temperature drop within the vehicle exhaust system during engine bench aging. When the CC catalyst (in an existing 2016 SULEV-30 vehicle) was exposed to an aging inlet temperature of 950°C, it was found that the temperature in the tailpipe region of the emission system was 550 - 580°C. The temperature drop was measured to be 50°C per foot of manifold. Therefore, for the tailpipe catalyst, the reactor aging inlet temperature was set to 600°C (inlet).

[0093] Subsequently, the catalyst article was tested as a CC1 + UF + tailpipe catalyst system in a reactor that was operated to reproduce the emissions and temperature traces of a 2016 SULEV-30 vehicle equipped with a 4-cylinder gasoline engine. The tailpipe catalyst was removed for reference measurements. All tests were performed using the FTP-72 test protocol. To ensure data reproducibility, each test was repeated at least 3 times. The same CC1 and UF catalyst articles were used in all cases, and only the tailpipe catalyst article was changed so that the effect of the tailpipe catalyst article on the system performance could be directly compared.

[0094] Example 7: Test Results The generation of THC, CO, and NO emissions in the FTP-72 test for the CC + UF reference system is shown in FIGS. 2A and 2B.

[0095] There are mainly two types of emissions: namely, 1) cold start emissions (about 0 - 100 seconds of the FTP-72 test) before the catalyst light-off is completed, and 2) "hot emissions" after cold start (about 150 - 1200 seconds of the FTP-72 test), which also include emissions that occur while the vehicle is accelerating and the engine is operating rich.

Number

[0096] The operating temperature of the tailpipe catalyst was varied to demonstrate the importance of correct catalyst placement within the exhaust system, which is for a specific vehicle and application. For the presented examples, the vehicle exhaust temperature trace was varied to investigate the range of operation and subsequently two representative temperatures were selected. These are shown in Figure 4. The trace start temperature is above room temperature to enable the reactor warm-up to coincide with the vehicle exhaust warm-up during high-speed acceleration of approximately 200 seconds. There is no significant activity contribution to the total emission results at this start temperature.

[0097] Figure 5 shows the cumulative CO emission plot for the CC+UF system using both the tailpipe catalyst design and the blank substrate used as a reference. The conversion levels for THC, CO, and NO observed using the tailpipe catalyst article are summarized in Table 1. The CO emission improvement region is shown in Figure 6.

Table 1

[0098] The proposed design of the tailpipe catalyst article achieved as high as 40% conversion under the selected experimental conditions, thus demonstrating the effectiveness of the proposed approach for reducing breakthrough emissions. An important aspect of the system of the present invention is that it can effectively treat CO emissions generated during rich engine operation, such as when the vehicle is accelerating rapidly.

[0099] Under high-temperature emission trace conditions, Pt-based formulations (tailpipe catalyst articles) are particularly efficient as they enable reduction of up to approximately 39% of CO and up to approximately 9% of THC emissions. Cu / Ni-based metal oxide (BMO) formulations (tailpipe catalyst articles) are also efficient, achieving a CO conversion rate of up to 36% and a THC conversion rate of up to 3%. Pd and Rh-based catalyst articles achieve CO conversion rates of approximately 23% and approximately 28% respectively, and in both cases a THC conversion rate of approximately 3%. The NO value is highest for Rh. However, generally, NO emissions are very low (150 seconds) in the FTP-72 test for the selected systems. See Figure 6. Since activity is affected by exhaust temperature, the conversion level can be further significantly increased by adjusting the placement of the catalyst articles in the system. Thus, the optimal position can be evaluated. The optimal position is the one that provides a balance between a moderate aging temperature and the highest exhaust temperature corresponding to that position during normal operation.

[0100] The overall trend is also very similar for lower temperature traces. Pt-based tailpipe catalyst articles show relatively high performance. As shown in Figure 7, the Pt-catalyst article (Pt / Pd / Rh: 3 / 0 / 0, III) also shows the highest light-off compared to the Rh-catalyst article (Pt / Pd / Rh: 0 / 0 / 3, I) and the Pd catalyst article (Pt / Pd / Rh: 0 / 3 / 0, II), and thus also shows the highest emission reduction in the cold start part of the emission trace. This is particularly pronounced in the case of CO emissions where the Pt-based tailpipe catalyst article design achieves a light-off T 50 value that is approximately 50 °C lower than that of Pd and Rh-based tailpipe catalyst article designs.

[0101] 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 claimed invention. 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 claimed invention. 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 options disclosed herein can be combined in all variations, regardless of whether such features or elements are explicitly combined in the description of a particular embodiment herein. The claimed invention is intended to be read as a whole such that any separable features or elements of the disclosed invention can be combined in any of its various aspects and embodiments, as would be understood to be possible by one of ordinary skill in the art, unless the context clearly indicates otherwise.

[0102] 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 claimed invention. It will be apparent to those skilled in the art that various modifications and changes can be made to the claimed method and apparatus of the invention without departing from the spirit and scope of the claimed invention. Accordingly, the claimed invention is intended to include modifications and changes within the scope of the appended claims and their equivalents, and the above embodiments are presented for purposes of illustration and not limitation. All patents and publications cited herein are incorporated by reference herein for the particular teachings described therein, unless a specific incorporation of other descriptions is provided.

Claims

1. An automotive catalyst system, a) a first close-coupled three-way conversion catalyst article in fluid communication with an engine exhaust port, said three-way conversion catalyst article comprising i) a first platinum group metal supported on a first support, and ii) a first substrate, the first close-coupled three-way conversion catalyst article; b) a catalyst article located downstream of and in fluid communication with said first close-coupled three-way conversion catalyst article, said catalyst article comprising i) a second platinum group metal supported on a second support, and ii) a second substrate, the catalyst article; c) i) a third platinum group metal and / or a non-platinum group metal comprising a combination of nickel and copper supported on one of ceria-zirconia, ceria, ceria-alumina, lanthana-zirconia, alumina-zirconia, a mixture of alumina and ceria, and a mixture of alumina and ceria-zirconia, and ii) a tailpipe catalyst article comprising a third substrate, wherein the loading of said third platinum group metal, when present, is in the range of 1.0 to 10.0 g / ft ３ (35.315 to 353.15 g / m ３ ), said tailpipe catalyst article (c) being arranged downstream in fluid communication with said catalyst article (b) at a position selected from in front of or behind a resonator, in front of or behind a muffler, between said resonator and said muffler, inside said muffler, inside said resonator, and at the end of a tailpipe, and being spaced 1.0 to 10 feet (0.3048 to 3.048 m) apart, the automotive catalyst system.

2. The catalyst system according to claim 1, wherein the amount of the third platinum group metal is less than 10% by weight of the total amount of the platinum group metals present in said catalyst system.

3. The catalyst system according to claim 1, wherein the loading of said first platinum group metal is in the range of 50 to 300 g / ft ３ (1765.75 to 10594.5 g / m ３ ).

4. The filling amount of the second platinum group metal is 1.0 g / ft ３ to 50.0 g / ft ３ (35.315 to 1765.75 g / m ３ ) and the catalyst system according to claim 1.

5. The filling amount of the third platinum group metal is 1.0 to 5.0 g / ft ３ (35.315 to 176.575 g / m ３ ) and the catalyst system according to claim 1.

6. Each of the first, second, and third platinum group metals is platinum, palladium, rhodium, or any combination thereof, and the catalyst system according to any one of claims 1 to 5.

7. The third platinum group metal is platinum, and the catalyst system according to any one of claims 1 to 6.

8. The automotive catalyst system is a) a first close-coupled three-way conversion catalyst article in fluid communication with the engine exhaust port, the article comprising 50 to 300 g / ft supported on a first support ３ (1765.75 to 10594.5 g / m ３ ) of the first platinum group metal and a first substrate, a first close-coupled three-way conversion catalyst article b) a catalyst article located downstream of and in fluid communication with the first close-coupled three-way conversion catalyst article, the article comprising 1.0 g / ft supported on a second support ３ (35.315 g / m ３ ) to 50 g / ft ３ (1765.75 g / m ３ ) of the second platinum group metal and a second substrate, a catalyst article c) i) supported on one of ceria-zirconia, ceria, ceria-alumina, lanthana-zirconia, alumina-zirconia, a mixture of alumina and ceria, and a mixture of alumina and ceria-zirconia, 1.0 to 5.0 g / ft ３ (35.315 to 176.575 g / m ３iii) a third platinum group metal and / or non-platinum group metal, and ii) a tailpipe catalyst article comprising a third substrate, The catalyst system according to any one of claims 1 to 7, wherein the tailpipe catalyst article (c) is in fluid communication with the catalyst article (b) downstream at a position selected from in front of or behind the resonator, in front of or behind the muffler, between the resonator and the muffler, inside the muffler, inside the resonator, and at the end of the tailpipe, and is arranged 1.0 to 10 feet (0.3048 to 3.048 m) apart.

9. The catalyst system according to any one of claims 1 to 8, wherein the first or second support is selected from the group consisting of an alumina component, an oxygen storage component, a zirconia component, and a ceria component.

10. The catalyst system according to claim 9, wherein the alumina component is selected from alumina, lanthana-alumina, ceria-alumina, ceria-zirconia-alumina, zirconia-alumina, lanthana-zirconia-alumina, barium-alumina, barium-lanthana-alumina, barium-lanthana-neodymia-alumina, or combinations thereof.

11. The catalyst system according to claim 9, wherein the oxygen storage component is selected from ceria-zirconia, ceria-zirconia-lanthana, ceria-zirconia-ytria, ceria-zirconia-lanthana-ytria, ceria-zirconia-neodymia, ceria-zirconia-praseodymia, ceria-zirconia-lanthana-neodymia, ceria-zirconia-lanthana-praseodymia, ceria-zirconia-lanthana-neodymia-praseodymia, or any combination thereof.

12. The ceria component is selected from ceria or stabilized ceria having a cerium oxide content of at least 85% by weight, and the ceria component optionally contains a dopant selected from zirconia, yttria, praseodymia, lanthana, neodymia, samaria, gadolinia, alumina, titania, barium, strontia, and combinations thereof, and the amount of the dopant is 1.0 to 20.0% by weight based on the total weight of the ceria component. The catalyst system according to claim 9.

13. The catalyst system according to any one of claims 1 to 12, wherein the catalyst article (b) is an underfloor catalyst article or a second close-coupled catalyst article.

14. The catalyst system according to any one of claims 1 to 13, wherein the first close-coupled three-way conversion catalyst article (a) and / or the catalyst article (b) is a single-layer or two-layer catalyst article.

15. The catalyst system according to claim 14, wherein the first close-coupled three-way conversion catalyst article (a) and / or the catalyst article (b) is a two-layer catalyst article including a bottom layer and a top layer, and the bottom layer and / or the top layer includes a front zone and a rear zone.

16. The catalyst system according to claim 1, wherein each of the first, second, and third substrates is a ceramic substrate, a metal substrate, a coated ceramic foam substrate, a polymer foam substrate, or a woven fiber substrate.

17. The automotive catalyst system is a) a first close-coupled three-way conversion catalyst article in fluid communication with the engine exhaust port, the article comprising: i) a bottom layer supported on an alumina component and an oxygen storage component and containing 90 to 100 g / ft ３ (3178.35 to 3531.5 g / m ３ ) of palladium, ii) a top layer supported on an alumina component and containing 1.0 to 10 g / ft ３ (35.315 to 353.15) of rhodium, and iii) a first close-coupled three-way conversion catalyst article including a first substrate. b) A underfloor catalyst article located downstream of and in fluid communication with the first close-coupled three-way conversion catalyst article, the article comprising: i) 1.0 g / ft ３ (35.315 g / m ３ ) to 5.0 g / ft ３ (176.575 g / m ３ ) of rhodium supported on an alumina component and an oxygen storage component, and ii) a second substrate, the underfloor catalyst article c) i) 1.0 to 5.0 g / ft ３ (35.315 to 176.575 g / m ３ ) of platinum supported on ceria-alumina, and ii) a tailpipe catalyst article comprising a third substrate, The tailpipe catalyst article (c) is arranged downstream in fluid communication with the catalyst article (b) at a position selected from in front of or behind the resonator, in front of or behind the muffler, between the resonator and the muffler, inside the muffler, inside the resonator, and at the end of the tailpipe, and is spaced 1.0 to 10 feet (0.3048 to 3.048 m) apart. The catalyst system according to any one of claims 1 to 16.

18. The automotive catalyst system is a) A first close-coupled three-way conversion catalyst article in fluid communication with the engine exhaust port, the article comprising: i) A bottom layer containing 90 to 100 g / ft ３ (3178.35 to 3531.5 g / m ３ ) of palladium supported on an alumina component and an oxygen storage component, ii) A top layer containing 1.0 to 10 g / ft ３ (35.315 to 353.15 g / m ３ ) of rhodium supported on an alumina component, and iii) A two-layer article comprising a first substrate, the first close-coupled three-way conversion catalyst article b) A underfloor catalyst article located downstream of and in fluid communication with the first close-coupled three-way conversion catalyst article, the article comprising: i) 1.0 g / ft ３ to 5.0 g / ft ３ (35.315 to 176.575 g / m ３a rhodium of (), and ii) a floor catalyst article comprising a second substrate, c) i) 1.0 to 5.0 g / ft supported on ceria-alumina ３ (35.315 to 176.575 g / m ３ ) of palladium, and ii) a tailpipe catalyst article comprising a third substrate, the tailpipe catalyst article (c) is located upstream or downstream of the resonator, upstream or downstream of the muffler, between the resonator and the muffler, inside the muffler, inside the resonator, and at a position selected from the end of the tailpipe, in fluid communication with the catalyst article (b) downstream and arranged 1.0 to 10 feet (0.3048 to 3.048 m) apart. The catalyst system according to any one of claims 1 to 16.

19. The automotive catalyst system is a) a first close-coupled three-way conversion catalyst article in fluid communication with the engine exhaust port, the article comprising i) a bottom layer containing 90 to 100 g / ft supported on an alumina component and an oxygen storage component ３ (3178.35 to 3531.5 g / m ３ ) of palladium, ii) a top layer containing 1.0 to 10 g / ft supported on an alumina component ３ (35.315 to 353.15 g / m ３ ) of rhodium, and iii) a first close-coupled three-way conversion catalyst article comprising a first substrate, b) a floor catalyst article located downstream of and in fluid communication with the first close-coupled three-way conversion catalyst article, the article comprising i) 1.0 g / ft supported on an alumina component and an oxygen storage component ３ to 5.0 g / ft ３ (35.315 to 176.575 g / m ３ ) of rhodium, and ii) a floor catalyst article comprising a second substrate, c) i) 0.5 wt% CuO and 10 wt% NiO supported on ceria and lanthana-zirconia, and ii) a tailpipe catalyst article comprising a third substrate, The tail pipe catalyst article (c) is in fluid communication with the catalyst article (b) downstream and arranged 1.0 to 10 feet (0.3048 to 3.048 m) apart at a position selected from in front of or behind the resonator, in front of or behind the muffler, between the resonator and the muffler, inside the muffler, inside the resonator, and at the end of the tail pipe. The catalyst system according to any one of claims 1 to 16.

20. 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 catalyst system according to any one of claims 1 to 19.

21. A method for reducing the carbon monoxide level in a gaseous exhaust stream, the method comprising contacting the gaseous exhaust stream with the catalyst system according to any one of claims 1 to 19.

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