Exhaust gas purification catalyst article having a PGM enrichment zone

Abstract

This invention provides an improved exhaust gas purification catalyst article that more efficiently reduces pollutants such as NOx, HC, and CO. [Solution] The present invention relates to an exhaust gas purification catalyst article containing a platinum group metal enrichment zone, a method for producing such an exhaust gas purification catalyst article, and a method for using such an exhaust gas purification catalyst article. Significantly higher pollutant reduction is achieved by providing a PGM enrichment zone containing a high amount of PGM that can be deposited on the bottom layer and / or top layer of the inlet or outlet portion of the substrate.

Description

Background Art

[0001] This application claims the benefit of priority to U.S. Provisional Application No. 62 / 939,117, filed Nov. 22, 2019, the content of which is hereby incorporated by reference in its entirety.

[0002] The present disclosure relates to an exhaust purification catalyst article useful for treating exhaust gas to reduce pollutants contained therein. In particular, the present disclosure relates to an exhaust purification catalyst article having an enriched platinum group metal (PGM) zone, and a method of preparing such an exhaust purification catalyst article.

[0003] Three-way conversion (TWC) catalysts (hereinafter referred to as three-way conversion catalysts, three-way catalysts, TWC catalysts, and interchangeably with TWC) have been used for several years to treat exhaust gas flows 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 an exhaust gas flow containing pollutants such as hydrocarbons, nitrogen oxides, and carbon monoxide. The three-way conversion catalyst oxidizes unburned hydrocarbons and carbon monoxide and reduces nitrogen oxides. Most commercially available TWC catalysts contain palladium as the main platinum group metal (PGM) component, which is used with a small amount of rhodium.

[0004] A TWC catalyst can be formed by coating a PGM metal-containing slurry onto a substrate. The coating can be in the form of a layered structure including a bottom layer and a top layer. The platinum group metal can be uniformly coated onto the substrate at a PGM loading in the range of about 3 g / ft 3 ~ about 300 g / ft 3 . In another technique, the platinum group metal can be coated onto the substrate in a zone-like pattern.

[0005] However, existing TWC catalysts do not provide sufficient reduction of pollutants such as NO x , HC, and CO to meet increasingly stringent worldwide emission standards. Thus, NO xThere is still a need for improved TWC catalysts that can more efficiently reduce pollutants such as HC and CO.

[0006] In one aspect, this disclosure is NO x To achieve a higher reduction of pollutants such as HC and CO, the present invention provides exhaust gas purification catalyst articles having improved wash-coat architecture, PGM type, and PGM filling amount, as well as improved coating strategies and methods for producing such catalyst articles.

[0007] Therefore, high-filling amounts of PGM (e.g., up to 1000 g / ft) can be deposited on the bottom and / or top layers of the inlet or outlet portion of the substrate. 3 It was found that by providing a PGM enrichment zone containing (etc.), a significantly higher reduction in contaminants can be achieved compared to conventional TWC catalyst articles.

[0008] Accordingly, in one embodiment, the present disclosure includes a substrate having an inlet axial end and an outlet axial end, a bottom wash coat layer coated over about 60% to about 100% of the axial length of the substrate, and a top wash coat layer coated over about 60% to about 100% of the axial length of the substrate, thereby covering at least about 60% of the length of the bottom wash coat layer. The top wash coat layer and / or bottom wash coat layer comprises a first portion containing one or more platinum group metals and a second portion containing one or more platinum group metals, The first part begins from the inlet axial end of the substrate, The concentration of platinum group metals in the first part is approximately 2 to 100 times higher than the concentration of platinum group metals in the second part. The first section has a length of approximately 0.25 inches to approximately 2 inches. If the amount of platinum group metal filling in the first section is determined axially from the first end of the first section to the second end of the first section, then it is approximately 10 g / ft 3 ~About 1000g / ft 3The present invention provides an exhaust gas purification catalyst article.

[0009] To provide an understanding of specific embodiments of this disclosure, accompanying drawings are referenced, which are not necessarily drawn to scale, and reference numbers refer to components of exemplary embodiments of this disclosure. The drawings are provided as examples only and should not be construed as limiting the scope of this disclosure. [Brief explanation of the drawing]

[0010] [Figure 1] A schematic representation of the washcoat architecture of exhaust gas purification catalyst articles prepared according to Reference Examples 1-3 (Catalysts A, B, and C) and Invention Examples 4-9 (Catalysts D-I) is shown. [Figure 2] The Pd gradient in the PGM enrichment zone of the bottom wash coat layer of catalyst D prepared according to Invention Example 4 is shown. Inset: Schematic representation of the wash coat architecture of catalyst D. [Figure 3] The Pt gradient in the PGM enrichment zone of the top wash coat layer of catalyst G prepared according to Invention Example 7 is shown. Inset: Schematic representation of the wash coat architecture of catalyst G. [Figure 4] The results of comparative tests of cumulative non-methane hydrocarbons (NMHC), NOx, and CO tailpipe exhaust under an FTP-75 test cycle are shown, using exhaust purification catalyst articles prepared according to Reference Examples 1 and 2 (Catalysts A and B), and Invention Examples 4, 5, and 6 (Catalysts D, E, and F). [Figure 5] The results of comparative tests of cumulative NMHC, NOx, and CO tailpipe exhaust under an FTP-75 test cycle are shown, using exhaust purification catalyst articles prepared according to Reference Examples 1 and 3 (Catalysts A and C), and Invention Examples 7, 8, and 9 (Catalysts G, H, and I). [Figure 6A] An exemplary honeycomb-type substrate carrier, which may function as a substrate according to some embodiments of the present disclosure and may have top and bottom wash coat layers, as well as a PGM-enriched zone coated thereon, is shown in perspective view. [Figure 6B] This is a magnified view of Figure 6A, and a partial cross-sectional view taken along a plane parallel to the end face of the substrate carrier in Figure 6A, showing a magnified view of the multiple gas channels shown in Figure 6A. [Figure 7] The exemplary honeycomb substrate in Figure 6A represents a wall flow filter substrate monolith, and the cross-sectional view shows an enlarged section of this section relative to Figure 6A.

[0011] This disclosure may be embodied in many different forms and should not be construed as being limited to the embodiments described herein, but rather these embodiments are provided to adequately convey the scope of this disclosure to those skilled in the art, so as to be sufficient and complete. Nothing in this specification should be construed as indicating that elements not claimed are essential to the carrying out of the disclosed materials and methods.

[0012] This disclosure is not limited to the details of the configuration or process steps set forth below. Other embodiments of this disclosure are possible and can be implemented or performed in various ways. It should be understood that the exemplary embodiments described herein are merely illustrative of the principles and applications of this disclosure. It will be apparent to those skilled in the art that various modifications and changes can be made to the methods and apparatus of this disclosure without departing from the spirit and scope of this disclosure. Therefore, this disclosure is intended to include modifications and changes within the scope of the appended claims and their equivalents.

[0013] In the context describing the materials and methods discussed herein (particularly in the context of the following claims), the use of the terms “a,” “an,” “the,” and similar demonstrative pronouns should be interpreted as encompassing both singular and plural forms, unless otherwise indicated herein or unless the context clearly contradicts this interpretation.

[0014] The term “approximately” is used throughout this specification to describe and explain small variations. For example, “approximately” means ±5% or less, e.g., ±2% or less, ±1% or less, ±0.5% or less, ±0.2% or less, ±0.1% or less, or ±0.05% or less. All numbers, whether explicitly stated or not, are modified by the term “approximately.” Values ​​modified by the term “approximately” include a specific value. For example, “approximately 5.0” includes 5.0.

[0015] All methods described herein may be performed in any preferred order, unless otherwise indicated herein or unless clearly contradicted by the context. The use of any and all examples or illustrative language provided herein (e.g., "etc.") is intended solely to better describe the materials and methods and is not intended to limit their scope unless otherwise requested.

[0016] Platinum group metals (PGMs) refer to any component containing PGMs (e.g., Rh, Pd, and Pt). For example, a PGM may be in a metallic form with zero valence, or it may be in an oxide form. References to “PGM components” take into account the presence of PGMs in any valence electron state. Terms such as “platinum (Pt) component,” “rhodium (Rh) component,” and “palladium (Pd) component” refer to the respective platinum group metal compounds, complexes, etc., that decompose or are converted into catalytically active forms, usually metals or metal oxides, during the calcination or use of the catalyst.

[0017] As used herein, the terms “catalyst” or “catalytic composition” refer to a material that promotes or accelerates the rate of a reaction.

[0018] As used herein, the terms "catalytic article" or "catalyst article" or "catalyst" refer to an article in which a substrate is coated with a catalyst component used to promote or accelerate a desired reaction. In some embodiments, 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.

[0019] As used herein, the term "NO x " refers to nitrogen oxide compounds such as, for example, NO and / or NO2.

[0020] In one aspect, the present disclosure includes a substrate having an inlet axial end and an outlet axial end, a bottom washcoat layer coated on about 60% to about 100% of the axial length of the substrate from the inlet axial end to the outlet axial end, and a top washcoat layer coated on about 60% to about 100% of the axial length of the substrate from either the inlet axial end or the outlet axial end of the substrate, such that the top washcoat layer covers at least about 60% of the axial length of the bottom washcoat layer. The top washcoat layer and / or the bottom washcoat layer includes a first portion containing one or more platinum group metals and a second portion containing one or more platinum group metals. The first portion starts from the inlet axial end of the substrate. The concentration of the platinum group metal in the first portion is about 2 to about 100 times higher than the concentration of the platinum group metal in the second portion. The first portion has an axial length of about 0.25 inches to about 2 inches. When the loading of the platinum group metal in the first portion is determined axially from the first end of the first portion to the second end of the first portion, it is about 10 g / ft 3 ~ about 1000 g / ft 3 A catalytic exhaust purification article is provided.

[0021] In some embodiments, the bottom wash coat layer is coated over approximately 70% to approximately 100% of the axial length of the substrate, for example, approximately 80% to approximately 100% of the axial length of the substrate. In some embodiments, the bottom wash coat layer is coated over the total length of the substrate. In some embodiments, the top wash coat layer is coated over approximately 70% to approximately 100% of the axial length of the substrate, for example, approximately 80% to approximately 100% of the axial length of the substrate. In some embodiments, the top wash coat layer is coated over the total length of the substrate. In some embodiments, the top wash coat layer covers at least approximately 70% of the bottom wash coat layer, such as at least approximately 80%, at least approximately 90%, or at least approximately 100% of the length of the bottom wash coat layer. In some embodiments, the top wash coat layer covers the total length of the bottom wash coat layer.

[0022] In some embodiments, the first portion is a PGM-enriched zone formed by coating a portion of a top wash coat layer and / or bottom wash coat layer, which are already pre-filled with one or more platinum group metals, with an additional platinum group metal solution.

[0023] In some embodiments, the platinum group metal is selected from platinum, palladium, rhodium, and combinations thereof.

[0024] In some embodiments, platinum group metals are supported on a carrier selected from oxygen storage components, alumina components, ceria components, zirconia components, and combinations thereof.

[0025] In some embodiments, the first portion has a length ranging from about 0.5 inches to about 1 inch.

[0026] In some embodiments, as determined by an electron probe microanalysis (EPMA) line scan moving from the top surface of the first portion to the substrate, more than 50% of the platinum group metals in the first portion are located in the top third (1 / 3) of the first portion. As used herein, the “top surface” of the first portion corresponds to the surface of the wash coat layer containing the first portion furthest from the substrate below, and the distance from the substrate surface is measured in a direction perpendicular to the substrate surface.

[0027] In some embodiments, as determined by an electron probe microanalysis (EPMA) line scan moving from the top surface of the first portion to the substrate, approximately 50% to 95% of the platinum group metals in the first portion are located in the top third (1 / 3) of the first portion.

[0028] In some embodiments, the first part includes palladium.

[0029] In some embodiments, the first portion includes platinum.

[0030] In some embodiments, the first part includes rhodium.

[0031] In some embodiments, the exhaust gas purification catalyst article comprises a bottom wash coat layer containing palladium or platinum deposited on a carrier selected from an oxygen storage component, an alumina component, and a combination thereof, which is coated over about 60% to about 100% of the axial length of the substrate from the inlet axial end to the outlet axial end. Including the first part and the second part, The first portion begins at the inlet axial end of the substrate and comprises palladium or platinum optionally supported on a carrier selected from an oxygen storage component, an alumina component, and combinations thereof. The concentration of palladium or platinum in the first part is approximately 2 to 100 times higher than the concentration of palladium or platinum in the second part. The first part has an axial length of approximately 0.25 inches to approximately 2 inches. If the amount of platinum group metal filling in the first section is determined axially from the first end of the first section to the second end of the first section, then it is approximately 10 g / ft 3 ~About 1000g / ft 3 The bottom wash coat layer, A top wash coat layer comprising rhodium, platinum, or a combination thereof, impregnated on a carrier selected from an oxygen storage component, an alumina component, and a combination thereof, which is coated from either the inlet or outlet end of the substrate over about 60% to about 100% of the axial length of the substrate, and as a result covers at least about 60% of the axial length of the bottom wash coat layer.

[0032] In some embodiments, the exhaust gas purification catalyst article comprises a bottom wash coat layer containing palladium impregnated on a carrier selected from an oxygen storage component, an alumina component, and a combination thereof, the bottom wash coat layer being coated over approximately 60% to approximately 100% of the axial length of the substrate from the inlet axial end to the outlet axial end, A top wash coat layer comprising rhodium, platinum, palladium, or a combination thereof, impregnated on a carrier selected from oxygen storage components, alumina components, and combinations thereof, which is coated from either the inlet or outlet end of the substrate over approximately 60% to approximately 100% of the axial length of the substrate, thereby covering at least approximately 60% of the axial length of the bottom wash coat layer. A first part comprising palladium or platinum optionally supported on a carrier selected from an oxygen storage component, an alumina component, and combinations thereof, and a second part comprising palladium or platinum, The first part begins from the inlet axial end of the substrate, The concentration of palladium or platinum in the first part is approximately 2 to 100 times higher than the concentration of palladium or platinum in the second part. The first part has an axial length ranging from approximately 0.25 inches to approximately 2 inches. If the amount of platinum group metal filling in the first section is determined axially from the first end of the first section to the second end of the first section, it is approximately 10 to approximately 1000 g / ft. 3 It includes a top wash coat layer.

[0033] In some embodiments, the first portion comprises palladium, and the amount of palladium in the first portion is about 30 to about 100% by weight of the total palladium present in the catalyst article. For example, in some embodiments, the first portion comprises about 50 to about 100% by weight, about 70 to about 100% by weight, or about 90 to about 100% by weight of the total palladium present in the catalyst article.

[0034] In some embodiments, the first portion comprises platinum, and the amount of platinum in the first portion is about 30 to about 100% by weight of the total platinum present in the catalyst article. For example, in some embodiments, the first portion comprises about 50 to about 100% by weight, about 70 to about 100% by weight, or about 90 to about 100% by weight of the total platinum present in the catalyst article.

[0035] In some embodiments, the first part includes a palladium or platinum concentration gradient, where the palladium or platinum concentration decreases exponentially from the top surface to the bottom surface of the washcoat layer coated with the PGM-enriched washcoat zone. As used herein, the “top surface” of the washcoat layer corresponds to the surface of the washcoat layer furthest from the underlying substrate, while the “bottom surface” of the washcoat layer corresponds to the surface of the washcoat layer closest to the underlying substrate, with the distance from the substrate measured perpendicular to the substrate surface.

[0036] In some embodiments, the weight ratio of the total platinum group metals filling amount in the first portion to the total platinum group metals filling amount in the second portion is in the range of about 4.0 to about 50. For example, in some embodiments, the weight ratio of the total platinum group metals filling amount in the first portion to the total platinum group metals filling amount in the second portion is in the range of about 10 to about 50, about 20 to about 50, about 30 to about 50, or about 40 to about 50.

[0037] In some embodiments, the alumina component includes one or more components selected from alumina, lantana-alumina, ceria-alumina, ceria-zirconia-alumina, zirconia-alumina, lantana-zirconia-alumina, barrier-alumina, barrier-lantana-alumina, barrier-lantana-neodymia-alumina, and combinations thereof.

[0038] In some embodiments, the oxygen storage component includes one or more components selected from ceria-zirconia, ceria-zirconia-lantana, ceria-zirconia-yttria, ceria-zirconia-lantana-yttria, ceria-zirconia-neodymia, ceria-zirconia-praseodymia, ceria-zirconia-lantana-neodymia, ceria-zirconia-lantana-praseodymia, ceria-zirconia-lantana-neodymia-praseodymia, and combinations thereof.

[0039] In some embodiments, the zirconia component comprises one or more components selected from lantana-zirconia, barium-zirconia, and combinations thereof.

[0040] In some embodiments, the bottom wash coat layer comprises one or more alkaline earth metal oxides selected from barium oxide, strontium oxide, and combinations thereof. In some embodiments, the one or more alkaline earth metal oxides are present in an amount ranging from about 1.0% to about 20% by weight, based on the total weight of the bottom wash coat layer.

[0041] In some embodiments, the substrate is a ceramic substrate, a metal substrate, a ceramic foam substrate, a polymer foam substrate, or a woven fiber substrate. In some embodiments, the substrate is a monolithic or honeycomb substrate.

[0042] As used herein, references to "monolithic substrate" or "honeycomb substrate" mean a single structure that is homogeneous and continuous from inlet to outlet.

[0043] As used herein, the term “washcoat” has its usual meaning in the art of a thin, adhesive coating of a catalyst or other material applied to a substrate material, such as a honeycomb-type carrier member, which is sufficiently porous to allow the passage of a gas stream being treated. A washcoat may be formed by preparing a slurry containing particles of a specific solid content (e.g., about 15 to about 60% by weight) in a liquid vehicle, then coating this onto a substrate and drying it to provide a washcoat layer.

[0044] As used herein and as described in Heck, Ronald, and Farrauto, Robert, Catalytic Air Pollution Control, New York: Wiley-Interscience, 2002, pp. 18-19, a washcoat layer comprises compositionally distinct layers of material disposed on the surface of a monolithic substrate or an underlying washcoat layer. In some embodiments of this disclosure, the substrate may comprise one or more washcoat layers. In some embodiments, each washcoat layer may differ from other washcoat layers in some way. For example, washcoat layers may differ with respect to their physical properties (e.g., particle size or microcrystalline phase) and / or their chemical composition or catalytic function.

[0045] As used herein, a catalyst article may be “unused,” meaning it is new and has not been exposed to any heat or thermal stress for an extended period. The term “unused” may also mean that the catalyst has been recently prepared and has not been exposed to any exhaust gases or high temperatures. In contrast, as used herein, an “aged” catalyst article is not unused and has been exposed to exhaust gases and / or high temperatures (e.g., above 500°C) for an extended period (e.g., more than 3 hours).

[0046] In some embodiments, the substrate of the exhaust gas purification catalyst article of the present disclosure may consist of any suitable material used to prepare automotive catalysts. In some embodiments, the substrate is a ceramic substrate, a metal substrate, a ceramic foam substrate, a polymer foam substrate, or a woven fiber substrate. In some embodiments, the substrate includes a ceramic or metal monolithic honeycomb structure.

[0047] In some embodiments, the substrate provides a plurality of wall surfaces to which one or more washcoat layers containing the catalyst composition described herein are coated and adhered, thereby acting as a carrier for the catalyst composition.

[0048] Examples of metal substrates include heat-resistant metals and metal alloys, such as titanium and stainless steel, as well as other alloys in which iron is substantial or a major component. In some embodiments, such alloys may contain one or more of nickel, chromium, and / or aluminum, and the total amount of these metals may include at least 15 wt% of the alloy, for example, about 10–25 wt% of chromium, about 3–8 wt% of aluminum, and up to about 20 wt% of nickel. In some embodiments, the alloy may also contain small or trace amounts of one or more metals, such as manganese, copper, vanadium, and titanium. In some embodiments, the surface of the metal substrate may be oxidized at a high temperature, for example, about 1000°C or higher, to form an oxide layer on the substrate surface, improving the corrosion resistance of the alloy and facilitating the adhesion of the wash coat layer to the metal surface.

[0049] In some embodiments, the ceramic material used to constitute the substrate may include any suitable refractory material, such as cordierite, mullite, cordierite-alumina, silicon nitride, zircon mullite, spodumene, alumina-silica-magnesia, zircon silicate, sillimanite, magnesium silicate, zircon, petalite, alumina, and aluminosilicate.

[0050] In some embodiments, any suitable substrate may be used, such as a monolithic flow-through substrate having multiple fine, parallel gas channels extending from the inlet to the outlet surface of the substrate, so that the channels are open to the fluid flow. The channels, which are essentially straight paths from inlet to outlet, are defined by walls on which the catalyst material is coated as a wash coat, so that the gas flowing through the channels comes into contact with the catalyst material. The channels in the monolithic substrate are thin-walled channels, which can be of any suitable cross-sectional shape, such as trapezoidal, rectangular, square, sinusoidal, hexagonal, elliptical, and circular. Such structures contain about 60 to about 1200 or more gas inlet openings (i.e., "cells") (cpsi) per square inch of cross-section, more commonly about 300 to about 900 cpsi. The wall thickness of the flow-through substrate may vary, with a typical range being between about 0.002 and about 0.1 inches. In some embodiments, the substrate may be a flow-through substrate, such as a cordierite substrate having, for example, 400 cpsi and a wall thickness of 6 mil, or 600 cpsi and a wall thickness of 4.0 mil. However, it will be understood that this disclosure is not limited to any particular type, material, or shape of substrate. In other embodiments, the substrate may be a wall-flow substrate, where each passage is blocked by a non-porous plug at one end of the substrate body, and the 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. In some embodiments, the monolithic substrate may contain up to about 700 cpsi or more, such as about 100 to about 400 cpsi, or about 200 to about 300 cpsi. The cross-sectional shape of the cell may vary as described above. The wall-flow substrate has a wall thickness of 0.002 to 0.1 inches. In some embodiments, typical wall flow substrates are composed of porous cordierite, examples of which have a wall thickness of about 10 mils at about 200 cpsi or about 8 mils at about 300 cpsi, with wall porosity ranging from about 45 to about 65%. In other embodiments, other ceramic materials such as aluminum titanate, silicon carbide, and silicon nitride can also be used as wall flow filter substrates.However, it will be understood that this disclosure is not limited to any particular type, material, or shape of substrate. It should be noted that, when the substrate is a wall-flow substrate, the catalyst composition may, in addition to being placed on the surface of the wall, penetrate into the pore structure of the porous wall (i.e., partially or completely block the pore openings). In some embodiments, the substrate has a flow-through ceramic honeycomb structure, a wall-flow ceramic honeycomb structure, or a metal honeycomb structure.

[0051] As used herein, the term “flow” broadly refers to any combination of fluid gases that may contain solid or liquid particulate matter.

[0052] As used herein, the terms “upstream” and “downstream” refer to the relative directions corresponding to the flow of engine exhaust gases from the engine to the tailpipe, with the engine located upstream and the tailpipe and any contaminant mitigation items, such as filters and catalysts, located downstream of the engine.

[0053] Figures 6A and 6B illustrate an exemplary substrate 2 in the form of a flow-through substrate coated with the wash-coat composition described herein. Referring to Figure 6A, the exemplary substrate 2 has a cylindrical shape and has a cylindrical outer surface 4, an upstream end surface 6, and a corresponding downstream end surface 8 identical to end surface 6. The substrate 2 has a plurality of fine, parallel gas channels 10 formed inside. As seen in Figure 6B, the channels 10 are formed by walls 12 and extend through the substrate 2 from the upstream end surface 6 to the downstream end surface 8, and the passages 10 are unobstructed, allowing a fluid, such as a gas flow, to flow longitudinally through the substrate 2 via its gas channels 10. As more readily seen in Figure 7, the walls 12 are dimensioned and constructed such that the gas channels 10 have a substantially regular polygonal shape. As shown, the wash-coat composition can be applied in a plurality of distinct layers as needed. In the exemplary embodiments, the wash coat includes a separate first wash coat layer 14 bonded to the wall 12 of the substrate member, and a second separate wash coat layer 16 coated on top of the first wash coat layer 14. In at least one embodiment, the currently claimed disclosure is also carried out with two or more (e.g., three or four) wash coat layers and is not limited to the exemplary two-layer embodiment.

[0054] Figure 7 illustrates an exemplary substrate 2 in the form of a wall flow filter substrate coated with a washcoat composition as described herein. As seen in Figure 7, the exemplary substrate 2 has a plurality of passages 52. The passages are tubularly enclosed by the inner wall 53 of the filter substrate. The substrate has an inlet end 54 and an outlet end 56. The alternating passages are blocked by inlet plugs 58 at the inlet end and by outlet plugs 60 at the outlet end, forming a checkerboard pattern that is reversed at the inlet 54 and outlet 56. The gas flow 62 enters through the unblocked channel inlet 64, is stopped by the outlet plugs 60, and diffuses to the outlet side 66 through the (porous) channel wall 53. The gas cannot pass back to the inlet side of the wall due to the inlet plugs 58. The porous wall flow filter used is catalytic in that the wall of the element has one or more contact materials on it or contains them. The catalyst material may be present only on the inlet side of the element wall, only on the outlet side, on both the inlet and outlet sides, or the wall itself may be composed entirely or partially of the catalyst material. This disclosure includes the use of one or more catalyst material layers in the inlet and / or outlet walls of an element.

[0055] Another aspect of this disclosure provides a process for preparing exhaust gas purification catalyst articles according to this disclosure.

[0056] In some embodiments, the process for preparing an exhaust gas purification catalyst article includes: a) preparing a bottom wash coat layer coated over about 60% to about 100% of the axial length of a substrate from the inlet axial end to the outlet axial end, comprising: obtaining a slurry containing one or more platinum group metals to be impregnated onto one or more carriers; and coating the slurry over about 60% to about 100% of the axial length of the substrate; and b) coating a portion of the bottom wash coat layer, starting from the inlet axial end of the substrate, with a platinum group metal solution in a length of about 0.25 inches to about 2 inches. The next step is to dry and calcine at a temperature in the range of approximately 100°C to approximately 140°C to obtain a PGM-enriched zone, and to prepare a top wash coat layer which is coated from either the inlet axial end or the outlet axial end of the substrate to approximately 60% to approximately 100% of the axial length of the substrate, thereby covering at least approximately 60% of the length of the bottom wash coat layer, comprising: obtaining a slurry containing one or more platinum group metals to be impregnated onto one or more carriers, and coating the slurry onto at least approximately 60% of the axial length of the bottom wash coat layer.

[0057] In some embodiments, the process for preparing an exhaust gas purification catalyst article is to prepare a bottom wash coat layer coated over about 60% to about 100% of the axial length of the substrate from the inlet axial end to the outlet axial end of the substrate, comprising: obtaining a slurry containing one or more platinum group metals to be impregnated onto one or more carriers; and coating the slurry over about 60% to about 100% of the length of the substrate; and b) coating over about 60% to about 100% of the axial length of the substrate from either the inlet axial end or the outlet axial end of the substrate, as a result, The preparation of a top wash coat layer comprising: preparing a top wash coat layer that covers at least about 60% of the length of a bottom wash coat layer, comprising: obtaining a slurry containing one or more platinum group metals to be impregnated onto one or more carriers; and coating the slurry over at least about 60% of the length of the bottom wash coat layer; and a) coating a portion of the top wash coat layer, starting from the inlet axial end of the substrate, with a platinum group metal solution in a length of about 0.25 inches to about 2 inches, and subsequently drying and calcining at a temperature of about 100°C to about 140°C to obtain a PGM enriched zone.

[0058] In some embodiments, the exhaust gas purification catalyst article prepared by the above process may be any exhaust gas purification catalyst article according to this disclosure, such as those described herein.

[0059] In some embodiments, the process of preparing the slurry includes techniques selected from initial wet impregnation, initial wet co-impregnation, post-addition, and combinations thereof.

[0060] Initial wet impregnation techniques, also known as capillary impregnation or dry impregnation, are generally used in the synthesis of heterogeneous materials, such as catalysts. An active metal precursor is dissolved in an aqueous or organic solution, and then the metal-containing solution is added to a catalyst support containing the same pore volume as the volume of the added solution. The solution is drawn into the pores of the support by capillary action. If the added solution exceeds the pore volume of the support, the solution transport changes from a capillary process to a much slower diffusion process. The catalyst is dried and calcined to remove 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 within the pores during impregnation and drying. Multiple active metal precursors may be co-impregnated into the catalyst support after appropriate dilution. Alternatively, the active metal precursor can be introduced into the slurry during the slurry preparation process via post-addition under stirring.

[0061] The carrier particles are thoroughly dried to absorb substantially all of the solution and form a wet solid. If rhodium is the active metal, aqueous solutions of water-soluble compounds or complexes of the active metal are used, such as rhodium chloride, rhodium nitrate, rhodium acetate, or combinations thereof; and if palladium is the active metal, such as palladium nitrate, palladium tetraamine, palladium acetate, or combinations thereof. After treatment of the carrier particles with the active metal solution, the particles are dried by heat treatment at a high temperature (e.g., about 100°C to about 150°C) for a certain period (e.g., 1 to 3 hours), and then calcined to convert the active metal into a more catalytically active form. An example of the calcination process involves heat treatment in air at a temperature of about 400 to 550°C for 10 minutes to 3 hours. If necessary, the above process can be repeated by impregnation to reach the desired level of active metal filling.

[0062] In some embodiments, the catalyst composition described above is prepared in the form of catalyst particles as described above. These catalyst particles are mixed with water to form a slurry for coating a catalyst substrate, such as a honeycomb substrate. In some embodiments, 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 examples of binders include boehmite, gamma-alumina, or delta / theta-alumina, as well as silica sol. If present, the binder may be used in an amount ranging from about 1.0 to about 5.0% by weight of the total fill volume of the wash coat. Addition of acidic or basic species to the slurry may be carried out as appropriate to adjust the pH. For example, in some embodiments, the pH of the slurry may be adjusted by adding ammonium hydroxide, an aqueous solution of nitric acid, or acetic acid. An exemplary pH range for the slurry is about 3.0 to about 12.

[0063] In some embodiments, the slurry may be pulverized to reduce particle size and / or to promote particle mixing. Pulverization may be achieved with a ball mill, continuous mill, or other similar apparatus, and the solid content of the slurry may be about 20–60% by weight, for example, about 20–40% by weight. In some embodiments, the slurry after pulverization may have particles of about 3.0–40 microns, for example, about 10–30 microns, or about 10–15 microns. 90 It is characterized by particle size. D 90 This can be determined using a dedicated particle size analyzer. For example, laser diffraction can be used to measure the particle size in a small amount of slurry. D in microns 90 This means that approximately 90% of the particles have a diameter below the specified value.

[0064] The slurry can be coated onto the catalyst substrate using any suitable washcoat technique. In some embodiments, the catalyst substrate is immersed in the slurry one or more times, or otherwise coated with the slurry. The coated substrate is then dried at a high temperature (e.g., about 100°C to about 150°C) for a set period of time (e.g., about 10 minutes to about 3 hours), and then fired by heating (e.g., about 400°C to 700°C for about 10 minutes to about 3 hours). After drying and firing, the final washcoat coating layer is essentially solvent-free. After firing, the amount of catalyst packed in obtained by the washcoat technique described above can be determined by calculating the difference between the coated weight and the uncoated weight of the substrate. As will be apparent to those skilled in the art, the amount of catalyst packed in can be modified by changing the rheology of the slurry. Furthermore, the coating / drying / firing process for producing the washcoat can be repeated as needed to build up the coating to a desired level of packedness or thickness, i.e., two or more washcoats may be applied.

[0065] In some embodiments, the coated substrate is aged by heat treatment. In some embodiments, aging is carried out by alternating hydrocarbon / air supply at a temperature of about 850°C to about 1050°C for about 50 to about 75 hours in an environment of 10 vol% moisture. Thus, in some embodiments, an aged catalyst article is provided. In some embodiments, particularly effective materials include metal oxide-based supports (substantially 100% ceria supports are included, but are not limited thereto) that maintain a high percentage of pore volume (e.g., about 95 to 100%) during aging (e.g., about 850°C to about 1050°C, 10 vol% water with alternating hydrocarbon / air supply for about 50 to 75 hours).

[0066] In another embodiment, an exhaust system for an internal combustion engine is provided, the system including an exhaust catalytic converter article according to the Disclosure.

[0067] In another embodiment, a method is provided for treating a gaseous exhaust flow containing hydrocarbons, carbon monoxide, and nitrogen oxides, the method comprising contacting the exhaust flow with an exhaust purification catalyst article or exhaust system in accordance with the present invention.

[0068] In another embodiment, a method is provided for reducing hydrocarbon, carbon monoxide, and nitrogen oxide levels in a gaseous exhaust stream, which, in accordance with the disclosure, involves bringing the gaseous exhaust stream into contact with a catalyst article or exhaust system to reduce the levels of hydrocarbon, carbon monoxide, and nitrogen oxides in the exhaust gas stream.

[0069] In another embodiment, the use of an exhaust gas purification catalyst article or exhaust gas system according to the Disclosure is provided for purifying a gaseous exhaust gas stream containing hydrocarbons, carbon monoxide, and nitrogen oxides.

[0070] Exemplary embodiment:

[0071] Some embodiments of this disclosure, though not limited to these, include the following: Embodiment 1. Exhaust gas purification catalyst article, A base material having an inlet axial end and an outlet axial end, A bottom wash coat layer is applied to approximately 60% to 100% of the axial length of the substrate from the inlet axial end to the outlet axial end, A top wash coat layer is applied from either the inlet or outlet end of the substrate to approximately 60% to approximately 100% of the axial length of the substrate, thereby covering at least approximately 60% of the length of the bottom wash coat layer, and includes: The top wash coat layer and / or bottom wash coat layer comprises a first portion and a second portion, the first portion starting from the inlet axial end of the substrate and exhibiting a platinum group metal concentration approximately 2 to 100 times higher than the platinum group metal concentration in the second portion. The first section has a length of approximately 0.25 inches to approximately 2 inches. If the amount of platinum group metal filling is determined axially from the first end of the first part to the second end of the first part, it is approximately 10 g / ft 3 ~About 1000g / ft 3 This is an exhaust gas purification catalyst article. Embodiment 2. The exhaust gas purification catalyst article according to Embodiment 1, wherein the first portion is a PGM enriched zone formed by coating a portion of a top wash coat layer and / or bottom wash coat layer, which are already pre-filled with platinum group metals, with an additional platinum group metal solution. Embodiment 3. An exhaust gas purification catalyst article according to Embodiment 1 or 2, wherein the platinum group metal is selected from platinum, palladium, rhodium, and combinations thereof. Embodiment 4. An exhaust gas purification catalyst article according to any one of Embodiments 1 to 3, wherein a platinum group metal is supported on a carrier selected from an oxygen storage component, an alumina component, a ceria component, a zirconia component, and combinations thereof. Embodiment 5. An exhaust gas purification catalyst article according to any one of Embodiments 1 to 4, wherein the first portion has a length ranging from about 0.5 inches to about 1 inch. Embodiment 6. An exhaust gas purification catalyst article according to any one of Embodiments 1 to 5, wherein, as determined by an electron probe microanalysis (EPMA) line scan from the top surface of the first portion to the substrate, more than 50% of the platinum group metals in the first portion are present in the top third (1 / 3) of the first portion. Embodiment 7. An exhaust gas purification catalyst article according to any one of Embodiments 1 to 6, wherein, as determined by an electron probe microanalysis (EPMA) line scan from the top surface of the first portion to the substrate, 50% to 95% of the platinum group metals in the first portion are present in the top third (1 / 3) of the first portion. Embodiment 8. An exhaust gas purification catalyst article according to any one of Embodiments 1 to 7, wherein the first part comprises palladium. Embodiment 9. An exhaust gas purification catalyst article according to any one of Embodiments 1 to 7, wherein the first part comprises platinum. Embodiment 10. An exhaust gas purification catalyst article according to any one of Embodiments 1 to 7, wherein the first part comprises rhodium. Embodiment 11. The article is A bottom wash coat layer comprising palladium or platinum supported on a carrier selected from an oxygen storage component, an alumina component, and a combination thereof, coated over approximately 60% to approximately 100% of the axial length of the substrate from the inlet axial end to the outlet axial end, The material comprises a first part and a second part, the first part comprising palladium or platinum optionally supported on a carrier selected from an oxygen storage component, an alumina component, and combinations thereof, starting from the inlet axial end of the substrate, wherein the concentration of palladium or platinum in the first part is approximately 2 to 100 times higher than the concentration of palladium or platinum in the second part. The first section has a length of approximately 0.25 inches to approximately 2 inches. If the amount of platinum group metal filling is determined axially from the first end of the first part to the second end of the first part, it is approximately 10 g / ft 3 ~About 1000g / ft 3 The bottom wash coat layer, An exhaust gas purification catalyst article according to any one of Embodiments 1 to 10, comprising: a top wash coat layer comprising rhodium, platinum, or a combination thereof, supported on a carrier selected from an oxygen storage component, an alumina component, and a combination thereof, and coated from either the inlet axial end or the outlet axial end of the substrate to about 60% to about 100% of the axial length of the substrate, thereby covering at least about 60% of the axial length of the bottom wash coat layer. Embodiment 12. The article is A bottom wash coat layer comprising palladium supported on a carrier selected from oxygen storage components, alumina components, and combinations thereof, coated over approximately 60% to 100% of the axial length of the substrate from the inlet axial end to the outlet axial end, A top wash coat layer comprising rhodium, platinum, palladium, and platinum group metals selected from combinations thereof, supported on a carrier selected from oxygen storage components, alumina components, and combinations thereof, is coated from either the inlet or outlet end of the substrate to about 60% to about 100% of the axial length of the substrate, thereby covering at least about 60% of the axial length of the bottom wash coat layer. The material comprises a first part and a second part, the first part comprising palladium or platinum optionally supported on a carrier selected from an oxygen storage component, an alumina component, and combinations thereof, starting from the inlet axial end of the substrate, wherein the concentration of palladium or platinum in the first part is approximately 2 to 100 times higher than the concentration of palladium or platinum in the second part. The first section has a length of approximately 0.25 inches to approximately 2 inches. If the amount of platinum group metal filling is determined axially from the first end of the first part to the second end of the first part, it is approximately 10 g / ft 3 ~About 1000g / ft 3 An exhaust gas purification catalyst article according to any one of embodiments 1 to 10, comprising a top wash coat layer. Embodiment 13. An exhaust gas purification catalyst article according to any one of Embodiments 8, 11, or 12, wherein the first portion comprises about 30 to about 100% by weight, about 50 to about 100% by weight, about 70 to about 100% by weight, or about 90 to about 100% by weight of the total palladium present in the catalyst article. Embodiment 14. An exhaust gas purification catalyst article according to any one of Embodiments 9, 11, or 12, wherein the first portion comprises about 30 to about 100% by weight, about 50 to about 100% by weight, about 70 to about 100% by weight, or about 90 to about 100% by weight of the total platinum present in the catalyst article. Embodiment 15. An exhaust gas purification catalyst article according to Embodiment 11 or 12, wherein the first portion comprises a palladium or platinum concentration gradient, and the concentration of palladium or platinum decreases exponentially from the top surface of the wash coat layer containing the first portion toward the bottom surface of the wash coat layer containing the first portion.

[0072] Embodiment 16. An exhaust gas purification catalyst article according to any one of Embodiments 1 to 15, wherein the weight ratio of the platinum group metal of the first part to the platinum group metal of the second part is in the range of about 4.0 to about 50, about 10 to about 50, about 20 to about 50, about 30 to about 50, or about 40 to about 50. Embodiment 17. An exhaust gas purification catalyst article according to any one of Embodiments 4, 11, and 12, wherein the alumina component comprises one or more components selected from alumina, lantana-alumina, ceria-alumina, ceria-zirconia-alumina, zirconia-alumina, lantana-zirconia-alumina, barrier-alumina, barrier-lantana-alumina, barrier-lantana-neodymia-alumina, and combinations thereof. Embodiment 18. An exhaust gas purification catalyst article according to any one of Embodiments 4, 11, and 12, wherein the oxygen storage component comprises one or more components selected from ceria-zirconia, ceria-zirconia-lantana, ceria-zirconia-yttria, ceria-zirconia-lantana-yttria, ceria-zirconia-neodymia, ceria-zirconia-praseodymia, ceria-zirconia-lantana-neodymia, ceria-zirconia-lantana-praseodymia, ceria-zirconia-lantana-neodymia-praseodymia, and combinations thereof. Embodiment 19. The exhaust gas purification catalyst article according to Embodiment 4, wherein the zirconia component comprises one or more components selected from lantana-zirconia, barium-zirconia, and combinations thereof. Embodiment 20. An exhaust gas purification catalyst article according to any one of Embodiments 1 to 19, wherein the bottom wash coat layer comprises one or more alkaline earth metal oxides selected from barium oxide, strontium oxide, and combinations thereof. Embodiment 21. An exhaust gas purification catalyst article according to Embodiment 20, wherein one or more alkaline earth metal oxides are present in an amount ranging from about 1.0% to about 20% by weight, based on the total weight of the bottom wash coat layer. Embodiment 22. An exhaust gas purification catalyst article according to any one of Embodiments 1 to 21, wherein the base material is a ceramic base material, a metal base material, a ceramic foam base material, a polymer foam base material, or a woven fiber base material. Embodiment 23. An exhaust gas purification catalyst article according to any one of Embodiments 1 to 22, wherein the bottom wash coat layer is coated over approximately 70% to approximately 100% of the axial length of the substrate, approximately 80% to approximately 100% of the axial length of the substrate, or approximately 100% of the axial length of the substrate. Embodiment 24. An exhaust gas purification catalyst article according to any one of Embodiments 1 to 23, wherein the top wash coat layer is coated over approximately 70% to approximately 100% of the axial length of the substrate, approximately 80% to approximately 100% of the axial length of the substrate, or approximately 100% of the axial length of the substrate. Embodiment 25. An exhaust gas purification catalyst article according to any one of Embodiments 1 to 24, wherein the top wash coat layer covers at least about 70%, at least about 80%, at least about 90%, or at least about 100% of the length of the bottom wash coat layer. Embodiment 26. The method for preparing a bottom wash coat layer is to be coated over approximately 60% to approximately 100% of the axial length of a substrate, from the inlet axial end of the substrate to the outlet axial end of the substrate, and comprises obtaining a slurry containing one or more platinum group metals to be impregnated onto one or more carriers, and coating the slurry over approximately 60% to approximately 100% of the axial length of the substrate. b) A portion of the bottom wash coat layer, starting from the axial end of the substrate's inlet, is coated with a platinum group metal solution for a length of approximately 0.25 inches to approximately 2 inches, and then dried and calcined at a temperature in the range of approximately 100°C to approximately 140°C to obtain a PGM-enriched zone. c) A process for preparing an exhaust gas purification catalyst article according to any one of embodiments 1 to 11 or 13 to 25, comprising: preparing a top wash coat layer which is coated from either the inlet axial end or the outlet axial end of the substrate to about 60% to about 100% of the axial length of the substrate, and as a result covering at least about 60% of the length of the bottom wash coat layer, comprising: obtaining a slurry containing one or more platinum group metals to be impregnated on one or more carriers; and coating the slurry on at least about 60% of the axial length of the bottom wash coat layer. Embodiment 27. a) Preparing a bottom wash coat layer coated over approximately 60% to approximately 100% of the axial length of the substrate from the inlet axial end to the outlet axial end of the substrate, comprising: obtaining a slurry containing one or more platinum group metals to be impregnated onto one or more carriers; and coating the slurry over approximately 60% to approximately 100% of the axial length of the substrate. b) Preparing a top wash coat layer that coats approximately 60% to approximately 100% of the axial length of the substrate from either the inlet axial end or the outlet axial end of the substrate, thereby covering at least approximately 60% of the length of the bottom wash coat layer, comprising: obtaining a slurry containing one or more platinum group metals to be impregnated onto one or more carriers; and coating the slurry onto at least approximately 60% of the length of the bottom wash coat layer. c) A process for preparing an exhaust gas purification catalyst article according to any one of Embodiments 1 to 10 or 12 to 25, comprising: coating a portion of the top wash coat layer, starting from the inlet axial end of the substrate, with a platinum group metal solution for a length of about 0.25 inches to about 2 inches; and subsequently drying and calcining at a temperature in the range of about 100°C to about 140°C to obtain a PGM enriched zone. Embodiment 28. An exhaust system for an internal combustion engine, comprising an exhaust purification catalyst article described in any one of Embodiments 1 to 25. Embodiment 29. A method for treating a gaseous exhaust flow containing hydrocarbons, carbon monoxide, and nitrogen oxides, comprising contacting the exhaust flow with an exhaust purification catalyst article according to any one of Embodiments 1 to 25, or with an exhaust system according to Embodiment 28. Embodiment 30. A method for reducing the levels of hydrocarbons, carbon monoxide, and nitrogen oxides in a gaseous exhaust flow, comprising bringing the gaseous exhaust flow into contact with an exhaust purification catalyst article according to any one of Embodiments 1 to 25, or an exhaust system according to Embodiment 28, to reduce the levels of hydrocarbons, carbon monoxide, and nitrogen oxides in the exhaust gas. Embodiment 31. Use of an exhaust gas purification catalyst article according to any one of Embodiments 1 to 25 for purifying a gaseous exhaust flow containing hydrocarbons, carbon monoxide, and nitrogen oxides.

[0073] The exhaust gas purification catalyst articles and methods for producing them described above are further described by the following non-limiting embodiments, which are intended to be purely illustrative.

[0074] Example 1: Preparation of CC1 reference catalyst A Reference catalyst A has a concentration of 80 g / ft 3 This is a Pd / Rh catalyst article having a PGM filling amount of (Pt / Pd / Rh = 0 / 76 / 4). Catalyst A is a two-layer wash-coat architecture coated on a cylindrical monolithic cordierite substrate having dimensions of 4.66 inches in diameter and 3.58 inches in length, a cell density of 600 cpsi, and a wall thickness of 3.5 mils.

[0075] Preparation of the bottom coat: Palladium precursor solution, 38 g / ft 3 Pd (50% by weight of total Pd) is impregnated onto refractory alumina, and in the form of a palladium precursor solution, 38 g / ft 3Pd (50% by weight of total Pd) was impregnated onto a stabilized ceria-zirconia composite material containing approximately 40% by weight of ceria. A slurry containing approximately 35.2% by weight of refractory Al2O3, 49.6% by weight of stabilized ceria-zirconia composite material, barium acetate yielding 11.6% by weight of BaO, zirconium acetate yielding 1.9% by weight of ZrO2, and 1.7% by weight of Pd was coated onto the substrate. After firing in air at 550°C for 1 hour, the fill weight of the wash coat of the bottom coat was approximately 2.59 g / in. 3 That was the case.

[0076] Preparation of the topcoat: 4 g / ft of rhodium precursor solution. 3 Rh (100% by weight of total Rh) was impregnated onto refractory alumina. A slurry mixture containing approximately 84.8% by weight of refractory Al2O3, 15.0% by weight of ceria-zirconia composite material with approximately 50% by weight of ceria, and 0.23% by weight of Rh was coated onto the bottom coat. After firing in air at 550°C for 1 hour, the fill weight of the top coat wash coat was approximately 1.00 g / in. 3 The reference Pd / Rh catalyst article is shown as an example in Figure 1.

[0077] Example 2: Preparation of CC1 Reference Catalyst B Reference catalyst B is 80 g / ft 3 This is a Pt / Pd / Rh catalyst article having a PGM filling amount of (Pt / Pd / Rh = 38 / 38 / 4). Catalyst B is a two-layer wash-coat architecture coated on a cylindrical monolithic cordierite substrate having dimensions of 4.66 inches in diameter and 3.58 inches in length, a cell density of 600 cpsi, and a wall thickness of 3.5 mils.

[0078] Preparation of the bottom coat: In the form of a palladium precursor solution, 19 g / ft 3 Pd (50% by weight of total Pd) is impregnated onto refractory alumina, and in the form of a palladium precursor solution, 19 g / ft 3Pd (50% by weight of total Pd) was impregnated onto a stabilized ceria-zirconia composite material containing approximately 40% by weight of ceria. A slurry containing approximately 35.4% by weight of refractory Al2O3, 50.1% by weight of stabilized ceria-zirconia composite material, barium acetate yielding 11.7% by weight of BaO, zirconium acetate yielding 2.0% by weight of ZrO2, and 0.9% by weight of Pd was coated onto the substrate. After firing in air at 550°C for 1 hour, the fill weight of the wash coat of the bottom coat was approximately 2.56 g / in. 3 That was the case.

[0079] Preparation of topcoat: 4 g / ft in the form of rhodium precursor solution and Pt precursor solution. 3 Rh (100% of total Rh) and 38 g / ft 3 Pt (100% by weight of total Pt) was impregnated onto refractory alumina. A slurry mixture containing approximately 83.1% by weight of refractory Al2O3, 14.6% by weight of ceria-zirconia composite material with approximately 50% by weight of ceria, 0.2% by weight of Rh, and 2.1% by weight of Pt was coated onto the bottom coat. After firing in air at 550°C for 1 hour, the fill weight of the top coat wash coat was approximately 1.02 g / in. 3 Catalyst B is illustrated in Figure 1.

[0080] Example 3: Preparation of CC1 reference catalyst C Reference catalyst C is 80 g / ft 3 This is a Pt / Pd / Rh catalyst article having a PGM filling amount of (Pt / Pd / Rh = 38 / 38 / 4). Catalyst C is a two-layer wash-coat architecture coated on a cylindrical monolithic cordierite substrate having dimensions of 4.66 inches in diameter and 3.58 inches in length, a cell density of 600 cpsi, and a wall thickness of 3.5 mils.

[0081] Preparation of the bottom coat: In the form of a palladium precursor solution, 19 g / ft 3 Pd (50% by weight of total Pd) is impregnated onto refractory alumina, and in the form of a palladium precursor solution, 19 g / ft 3Pd (50% by weight of total Pd) was impregnated onto a stabilized ceria-zirconia composite material containing approximately 40% by weight of ceria. A slurry containing approximately 35.4% by weight of refractory Al2O3, 50.1% by weight of stabilized ceria-zirconia composite material, barium acetate yielding 11.7% by weight of BaO, zirconium acetate yielding 2.0% by weight of ZrO2, and 0.9% by weight of Pd was coated onto the substrate. After firing in air at 550°C for 1 hour, the fill weight of the wash coat of the bottom coat was approximately 2.56 g / in. 3 That was the case.

[0082] Preparation of topcoat: 4 g / ft in the form of rhodium precursor solution and Pt precursor solution. 3 Rh (100% of total Rh) and 38 g / ft 3 Pt (100% by weight of total Pt) was impregnated onto refractory alumina / ceria. A slurry mixture containing 14.6% by weight of ceria-zirconia composite material with approximately 83.1% by weight of refractory Al2O3 / CeO2, approximately 50% by weight of ceria, 0.2% by weight of Rh, and 2.1% by weight of Pt was coated onto the bottom coat. After firing in air at 550°C for 1 hour, the fill weight of the top coat wash coat was approximately 1.02 g / in. 3 Catalyst C is illustrated in Figure 1.

[0083] Example 4: Preparation of CC1 Inventive Catalyst D The inventive catalyst D is 80 g / ft 3 The catalyst article has a Pt / Pd / Rh filling amount of (Pt / Pd / Rh = 38 / 38 / 4). Catalyst D includes a washcoat architecture consisting of a bottom coat, an additional PGM enrichment zone on the catalyst inlet side, and a topcoat coated on a cylindrical monolithic cordierite substrate having dimensions of 4.66 inches in diameter and 3.58 inches in length, a cell density of 600 cpsi, and a wall thickness of 3.5 mils.

[0084] Preparation of the bottom coat: Palladium precursor solution, 7.6 g / ft 3Pd (20% by weight of total Pd) was impregnated onto refractory alumina, and in the form of a palladium precursor solution, 7.6 g / ft 3 Pd (20% by weight of total Pd) was impregnated onto a stabilized ceria-zirconia composite material containing approximately 40% by weight of ceria. A slurry containing approximately 35.6% by weight of refractory Al2O3, 50.3% by weight of stabilized ceria-zirconia composite material, barium acetate yielding 11.8% by weight of BaO, zirconium acetate yielding 2.0% by weight of ZrO2, and 0.3% by weight of Pd was coated onto the substrate. After firing in air at 550°C for 1 hour, the fill weight of the wash coat of the bottom coat was approximately 2.55 g / in. 3 That was the case.

[0085] Preparation of the enrichment zone on the catalyst inlet side:

[0086] 152g / ft 3 A Pd precursor solution containing Pd (60% of total Pd) was absorbed from the inlet end of a substrate already containing a bottom coat. After the absorption step, a blower was used to remove excess Pd from the substrate, thus forming a surface-enriched Pd layer with an enrichment zone length of approximately 0.75 inches. In the subsequent step, the substrate was dried at 120°C for 30 minutes and then calcined in air for 1 hour. The conditions were adjusted so that the resulting Pd-enriched layer contained approximately 80% of the total Pd in ​​the sample. The Pd-enriched zone exhibits a Pd gradient in which the Pd concentration decreases from the top of the bottom coat toward the substrate. The gradient was set so that at least 50% of the Pd in ​​the enrichment zone was located in the upper one-third (1 / 3) of the bottom coat.

[0087] Preparation of topcoat: 4 g / ft in the form of rhodium precursor solution and Pt precursor solution. 3 Rh (100% of total Rh) and 38 g / ft 3Pt (100% by weight of total Pt) was impregnated onto refractory alumina. A slurry mixture containing approximately 83% by weight of refractory Al2O3, 14.6% by weight of ceria-zirconia composite material with approximately 50% by weight of ceria, 0.2% by weight of Rh, and 2.1% by weight of Pt was coated onto the bottom coat. After firing in air at 550°C for 1 hour, the fill weight of the top coat wash coat was approximately 1.00 g / in. 3 Catalyst D is illustrated in Figure 1.

[0088] Example 5: Preparation of CC1 Inventive Catalyst E The inventive catalyst E has a concentration of 80 g / ft 3 The catalyst article is a Pt / Pd / Rh catalyst having a PGM filling amount of (Pt / Pd / Rh = 38 / 38 / 4). Catalyst E includes a washcoat architecture consisting of a bottom coat, an additional PGM enrichment zone on the catalyst inlet side, and a topcoat coated on a cylindrical monolithic cordierite substrate having dimensions of 4.66 inches in diameter and 3.58 inches in length, a cell density of 600 cpsi, and a wall thickness of 3.5 mils.

[0089] Preparation of the bottom coat: The bottom coat was identical to the bottom coat of catalyst D.

[0090] Preparation of the enrichment zone on the catalyst inlet side: The enrichment zone was identical to the enrichment zone of catalyst D.

[0091] Preparation of topcoat: 4 g / ft in the form of rhodium precursor solution and Pt precursor solution. 3 Rh (100% of total Rh) and 38 g / ft 3Pt (100% by weight of total Pt) was impregnated onto refractory alumina / zirconia. A slurry mixture containing approximately 83% by weight of refractory Al2O3 / ZrO2 with 20% by weight of ZrO2, 14.6% by weight of ceria-zirconia composite material with approximately 50% by weight of ceria, 0.2% by weight of Rh, and 2.1% by weight of Pt was coated onto the bottom coat. After firing in air at 550°C for 1 hour, the fill weight of the top coat wash coat was approximately 1.00 g / in. 3 Catalyst E is illustrated in Figure 1.

[0092] Example 6: Preparation of CC1 Inventive Catalyst F The inventive catalyst F is 80 g / ft 3 The catalyst article is a Pt / Pd / Rh catalyst having a PGM filling amount of (Pt / Pd / Rh = 38 / 38 / 4). Catalyst F includes a washcoat architecture consisting of a bottom coat, an additional PGM enrichment zone on the catalyst inlet side, and a topcoat coated on a cylindrical monolithic cordierite substrate having dimensions of 4.66 inches in diameter and 3.58 inches in length, a cell density of 600 cpsi, and a wall thickness of 3.5 mils.

[0093] Preparation of the bottom coat: The bottom coat was identical to the bottom coat of catalyst D.

[0094] Preparation of the enrichment zone at the catalyst inlet: The enrichment zone was identical to that of catalyst D, except for the addition of the alumina binder material to the Pd precursor solution. The solutions were thoroughly mixed and then applied to the substrate in a manner similar to the process described for catalyst D. The alumina / Pd precursor ratio was approximately 1:1 by weight.

[0095] Preparation of the topcoat: The topcoat was identical to topcoat catalyst E. Catalyst F is illustrated in Figure 1.

[0096] Example 7: Preparation of CC1 Inventive Catalyst G The inventive catalyst G is 80 g / ft 3The catalyst article is a Pt / Pd / Rh catalyst article having a PGM filling amount of (Pt / Pd / Rh = 38 / 38 / 4). Catalyst G includes a washcoat architecture consisting of a bottom coat, a top coat, and an additional PGM enrichment zone on the inlet side of the coated catalyst, after the top coat has been coated onto a cylindrical monolithic cordierite substrate having dimensions of 4.66 inches in diameter and 3.58 inches in length, a cell density of 600 cpsi, and a wall thickness of 3.5 mils.

[0097] Preparation of the bottom coat: In the form of a palladium precursor solution, 19 g / ft 3 Pd (50% by weight of total Pd) is impregnated onto refractory alumina, and in the form of a palladium precursor solution, 19 g / ft 3 Pd (50% by weight of total Pd) was impregnated onto a stabilized ceria-zirconia composite material containing approximately 40% by weight of ceria. A slurry containing approximately 35.4% by weight of refractory Al2O3, 50.1% by weight of stabilized ceria-zirconia composite material, barium acetate yielding 11.7% by weight of BaO, zirconium acetate yielding 2.0% by weight of ZrO2, and 0.9% by weight of Pd was coated onto the substrate. After firing in air at 550°C for 1 hour, the fill weight of the wash coat of the bottom coat was approximately 2.56 g / in. 3 That was the case.

[0098] Preparation of the topcoat: 4 g / ft of rhodium precursor solution. 3 Rh (100% by weight of total Rh) was impregnated onto refractory alumina / ceria. A slurry mixture containing 15.0% by weight of ceria-zirconia composite material with approximately 84.8% by weight of refractory Al2O3 / CeO2, approximately 50% by weight of ceria, and 0.2% by weight of Rh was coated onto the bottom coat. After firing in air at 550°C for 1 hour, the wash coat filling amount of the top coat was approximately 1.00 g / in. 3 That was the case.

[0099] Preparation of the enrichment zone on the catalyst inlet side: 253.3 g / ft 3A Pt precursor solution containing Pt (100% of total Pt) was absorbed from the inlet end of a substrate already containing the bottom and top coats. After the absorption step, a blower was used to remove excess Pt from the substrate, thus forming a surface-enriched Pt layer with an enrichment zone length of approximately 0.55 inches. In the subsequent step, the substrate was dried at 120°C for 30 minutes and then calcined in air for 1 hour. The Pt-enriched zone in the top coat exhibits a Pt gradient in which the Pt concentration decreases from the top of the top coat toward the substrate. The gradient was set so that at least 50% of the Pt in the enrichment zone is located in the top third (1 / 3) of the top coat. Catalyst G is illustrated in Figure 1.

[0100] Example 8: Preparation of CC1 Inventive Catalyst H The inventive catalyst H is 80 g / ft 3 The catalyst article is a Pt / Pd / Rh catalyst having a PGM filling amount of (Pt / Pd / Rh = 38 / 38 / 4). The catalyst H includes a wash-coat architecture consisting of a bottom coat, an additional PGM enrichment zone on the inlet side of the catalyst coated after the bottom coat, and a top coat coated on a cylindrical monolithic cordierite substrate having dimensions of 4.66 inches in diameter and 3.58 inches in length, a cell density of 600 cpsi, and a wall thickness of 3.5 mils.

[0101] Preparation of the bottom coat: In the form of a palladium precursor solution, 19 g / ft 3 Pd (50% by weight of total Pd) is impregnated onto refractory alumina, and in the form of a palladium precursor solution, 19 g / ft 3 Pd (50% by weight of total Pd) was impregnated onto a stabilized ceria-zirconia composite material containing approximately 40% by weight of ceria. A slurry containing approximately 35.4% by weight of refractory Al2O3, 50.1% by weight of stabilized ceria-zirconia composite material, barium acetate yielding 11.7% by weight of BaO, zirconium acetate yielding 2.0% by weight of ZrO2, and 0.9% by weight of Pd was coated onto the substrate. After firing in air at 550°C for 1 hour, the fill weight of the wash coat of the bottom coat was approximately 2.56 g / in.3 That was the case.

[0102] Preparation of the enrichment zone on the catalyst inlet side: 126.7 g / ft 3 A Pt precursor solution containing Pt (50% of total Pt) was absorbed from the inlet end of a substrate already containing a bottom coat. After the absorption step, a blower was used to remove excess Pt from the substrate, thus forming a surface-enriched Pt layer with an enrichment zone length of approximately 0.55 inches. In the subsequent step, the substrate was dried at 120°C for 30 minutes and then calcined in air for 1 hour. The Pt enrichment in the bottom coat exhibited a Pt gradient in which the Pt concentration decreased from the top of the bottom coat toward the substrate. The gradient appeared to indicate that at least 50% of the Pt in the enrichment zone was located in the top third (1 / 3) of the bottom coat.

[0103] Preparation of the topcoat: 4 g / ft of rhodium precursor solution. 3 Rh (100% by weight of total Rh), and Pt precursor solution, 19 g / ft 3 Pt (50% by weight of total Pt) was impregnated onto refractory alumina / ceria. A slurry mixture containing 14.8% by weight of ceria-zirconia composite material with approximately 83.9% by weight of refractory Al2O3 / CeO2, approximately 50% by weight of ceria, 0.2% by weight of Rh, and 1.1% by weight of Pt was coated onto the bottom coat. After firing in air at 550°C for 1 hour, the fill weight of the top coat wash coat was approximately 1.00 g / in. 3 Catalyst H is illustrated in Figure 1.

[0104] Example 9: Preparation of CC1 Inventive Catalyst I Inventive catalyst I has a concentration of 80 g / ft 3The catalyst article is a Pt / Pd / Rh catalyst having a PGM filling amount of (Pt / Pd / Rh = 38 / 38 / 4). Catalyst I includes a washcoat architecture consisting of a bottom coat, a top coat, and an additional PGM enrichment zone on the inlet side of the coated catalyst, after the top coat has been coated onto a cylindrical monolithic cordierite substrate having dimensions of 4.66 inches in diameter and 3.58 inches in length, a cell density of 600 cpsi, and a wall thickness of 3.5 mils.

[0105] Preparation of the bottom coat: In the form of a palladium precursor solution, 19 g / ft 3 Pd (50% by weight of total Pd) is impregnated onto refractory alumina, and in the form of a palladium precursor solution, 19 g / ft 3 Pd (50% by weight of total Pd) was impregnated onto a stabilized ceria-zirconia composite material containing approximately 40% by weight of ceria. A slurry containing approximately 35.4% by weight of refractory Al2O3, 50.1% by weight of stabilized ceria-zirconia composite material, barium acetate yielding 11.7% by weight of BaO, zirconium acetate yielding 2.0% by weight of ZrO2, and 0.9% by weight of Pd was coated onto the substrate. After firing in air at 550°C for 1 hour, the fill weight of the wash coat of the bottom coat was approximately 2.56 g / in. 3 That was the case.

[0106] Preparation of the topcoat: 4 g / ft of rhodium precursor solution. 3 Rh (100% by weight of total Rh), and Pt precursor solution, 19 g / ft 3 Pt (50% by weight of total Pt) was impregnated onto refractory alumina / ceria. A slurry mixture containing 14.8% by weight of ceria-zirconia composite material with approximately 83.9% by weight of refractory Al2O3 / CeO2, approximately 50% by weight of ceria, 0.2% by weight of Rh, and 1.1% by weight of Pt was coated onto the bottom coat. After firing in air at 550°C for 1 hour, the fill weight of the top coat wash coat was approximately 1.00 g / in. 3 That was the case.

[0107] Preparation of the enrichment zone on the catalyst inlet side: 126.7 g / ft 3 A Pt precursor solution containing Pt (50% of total Pt) was absorbed from the inlet end of a substrate already containing a bottom coat. After the absorption step, a blower was used to remove excess Pt from the substrate, thus forming a surface-enriched Pt layer with an enrichment zone length of approximately 0.55 inches. In the subsequent step, the substrate was dried at 120°C for 30 minutes and then calcined in air for 1 hour. The Pt-enriched zone in the top coat exhibited a Pt gradient, with the Pt concentration decreasing from the top of the top coat toward the substrate. The gradient appeared to indicate that at least 50% of the Pt in the enrichment zone was located in the top third (1 / 3) of the top coat. Catalyst I is illustrated in Figure 1.

[0108] Example 10: Preparation of UF reference catalyst J Reference catalyst J is 3 g / ft 3 The catalyst article has a PGM filling amount of (Pt / Pd / Rh=0 / 0 / 3). Catalyst J comprises a single-layer wash-coat architecture coated on a cylindrical monolithic cordierite substrate having dimensions of 4.66 inches in diameter and 4.4 inches in length, a cell density of 400 cpsi, and a wall thickness of 4 mils.

[0109] In the form of a rhodium precursor solution, 3 g / ft 3 Rh (100% by weight of total Rh) was mixed with water, refractory alumina, and a stabilized ceria-zirconia composite material containing approximately 40% by weight of ceria. A slurry containing approximately 63.1% by weight of refractory Al2O3, 32.0% by weight of stabilized ceria-zirconia composite material, barium acetate yielding 1.5% by weight of BaO, zirconium acetate yielding 0.3% by weight of ZrO2, strontium acetate yielding 1.5% by weight of SrO, and 0.1% by weight of Rh was coated onto a substrate. After firing in air at 550°C for 1 hour, the fill weight of the wash coat was approximately 2.8 g / in. 3 That was the case.

[0110] Example 11: Catalyst testing All catalysts prepared in Examples 1-10 were aged using an exothermic aging protocol with an engine set to operate so that a typical inlet temperature of approximately 940°C and a typical catalyst floor temperature of 1000°C were not exceeded. To simulate the typical operating conditions of a vehicle tested with the FTP-75 test protocol, the engine outgass supply composition was alternated between rich and lean. All CC1 catalysts were aged for 50 hours under the same conditions. Catalyst J was used as a general underfloor catalyst and aged using the same protocol, but due to its UF position, it resulted in a proportionally lower effective temperature at 100 hours.

[0111] Exhaust performance was tested using a 2.0L turbocharged ULEV70 vehicle equipped with a proximal coupling + underbody (CC+UF) exhaust purification system configuration, operated under the FTP-75 test protocol. Each system was tested at least four times to ensure high experimental reproducibility and data consistency.

[0112] The benefits of using the Pd-enriched zone according to this disclosure are demonstrated in Figure 4. Catalysts D-F of the present invention enhance NMHC+NOx by up to 18% compared to both Pd / Rh reference catalyst A and Pt / Pd / Rh reference catalyst B. x The reduction in exhaust emissions is demonstrated. Furthermore, catalysts D to F of the present invention also achieve a CO emission reduction of up to approximately 12% compared to reference catalysts A and B. The catalyst system achieves performance of SULEV 30 or higher under selected aging and test conditions.

[0113] Figure 5 illustrates the benefits of using the Pt-enriched zone described in this disclosure. Catalysts G-I yield up to 10% more NMHC+NOx compared to both Pd / Rh reference catalyst A and Pt / Pd / Rh reference catalyst C. x The reduction in exhaust emissions is demonstrated. Furthermore, catalysts G-I of the present invention also achieve a CO emission reduction of up to approximately 20% compared to reference catalysts A and C. The catalyst system achieves performance of SULEV 30 or higher under selected aging and test conditions.

[0114] Throughout this Spec., any reference to “one embodiment,” “a certain embodiment,” “one or more embodiments,” “embodiment,” or “some embodiments” means that a particular feature, structure, material, or property described in relation to an embodiment is included in at least one embodiment of this disclosure. Therefore, phrases such as “in one or more embodiments,” “in a particular embodiment,” “in some embodiments,” “in one embodiment,” or “in an embodiment” appearing in various places throughout this Spec. Not necessarily refer to the same embodiment of this disclosure. Furthermore, a particular feature, structure, material, or property can be combined in any preferred 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 feature or element is explicitly combined in the description of a particular embodiment herein. The claimed inventions in this application are intended to be read as a whole, so that, unless the context clearly indicates otherwise, any divisible feature or element of this disclosure is intended to be combinable in any of its various aspects and embodiments.

[0115] The embodiments disclosed herein have been described with reference to certain exemplary embodiments, but it should be understood that these embodiments are merely illustrative of the principles and applications of the disclosure. It will be apparent to those skilled in the art that various modifications and changes can be made to the methods and apparatus of the disclosure without departing from the spirit and scope of the disclosure. Accordingly, the disclosure is intended to include variations and changes within the scope of the appended claims and their equivalents, and the embodiments described above are presented for illustrative purposes only, not limiting purposes. All patents and publications cited herein are incorporated herein by reference with respect to the specific teachings described therein unless other incorporated statements are specifically provided.

Claims

1. Exhaust gas purification catalyst article, A base material having an inlet axial end and an outlet axial end, A bottom wash coat layer is coated over approximately 60% to approximately 100% of the axial length of the substrate from the inlet axial end to the outlet axial end, A top wash coat layer is applied to approximately 60% to approximately 100% of the axial length of the substrate from either the inlet end or the outlet end of the substrate, thereby covering at least approximately 60% of the length of the bottom wash coat layer, comprising: The top wash coat layer and / or the bottom wash coat layer comprises a first portion containing one or more platinum group metals and a second portion containing one or more platinum group metals, The first portion begins from the inlet axial end of the substrate, The concentration of the platinum group metal in the first portion is approximately 2 to 100 times higher than the concentration of the platinum group metal in the second portion. The first portion has a length of approximately 0.25 inches to approximately 2 inches. If the amount of platinum group metal filling in the first portion is determined axially from the first end of the first portion to the second end of the first portion, then approximately 10 g / ft ３ ~Approx. 1000g / ft ３ This is an exhaust gas purification catalyst article.

2. The exhaust gas purification catalyst article according to claim 1, wherein the first portion is a PGM enrichment zone formed by coating a portion of the top wash coat layer and / or the bottom wash coat layer, which are already pre-filled with platinum group metals, with an additional platinum group metal solution.

3. The exhaust gas purification catalyst article according to claim 1 or 2, wherein the one or more platinum group metals are selected from platinum, palladium, rhodium, and combinations thereof.

4. The exhaust gas purification catalyst article according to any one of claims 1 to 3, wherein the platinum group metal is supported on a carrier selected from an oxygen storage component, an alumina component, a ceria component, a zirconia component, and combinations thereof.

5. The exhaust gas purification catalyst article according to any one of claims 1 to 4, wherein the first portion has a length in the range of about 0.5 inches to about 1 inch.

6. The exhaust gas purification catalyst article according to any one of claims 1 to 5, wherein, as determined by an electron probe microanalysis (EPMA) line scan from the uppermost surface of the first portion to the substrate, 50% or more of the platinum group metals in the first portion are present in the uppermost one-third (1 / 3) of the first portion.

7. The exhaust gas purification catalyst article according to any one of claims 1 to 7, wherein, as determined by an electron probe microanalysis (EPMA) line scan from the top surface of the first portion to the substrate, 50% to 95% of the platinum group metal in the first portion is located in the top third (1 / 3) of the first portion.

8. The exhaust gas purification catalyst article according to any one of claims 1 to 7, wherein the first portion comprises palladium.

9. The exhaust gas purification catalyst article according to any one of claims 1 to 7, wherein the first portion comprises platinum.

10. The exhaust gas purification catalyst article according to any one of claims 1 to 7, wherein the first portion comprises rhodium.

11. The aforementioned article, A bottom wash coat layer comprising palladium or platinum deposited on a carrier selected from an oxygen storage component, an alumina component, and a combination thereof, coated over approximately 60% to approximately 100% of the axial length of the substrate from the inlet axial end to the outlet axial end, The bottom wash coat layer comprises a first portion and a second portion, the first portion comprising palladium or platinum optionally supported on a carrier selected from an oxygen storage component, an alumina component, and a combination thereof, starting from the axial end of the inlet of the substrate, wherein the concentration of palladium or platinum in the first portion is about 2 to about 100 times higher than the concentration of palladium or platinum in the second portion. The first portion has a length of approximately 0.25 inches to approximately 2 inches. If the amount of platinum group metal filling in the first portion is determined axially from the first end of the first portion to the second end of the first portion, then approximately 10 g / ft ３ ~Approx. 1000g / ft ３ The bottom wash coat layer, An exhaust gas purification catalyst article according to any one of claims 1 to 10, comprising: a top wash coat layer comprising one or more platinum group metals selected from rhodium, platinum, and combinations thereof, impregnated on a carrier selected from an oxygen storage component, an alumina component, and combinations thereof, and coated from either the inlet axial end or the outlet end of the substrate to about 60% to about 100% of the axial length of the substrate, thereby covering at least about 60% of the length of the bottom wash coat layer.

12. The aforementioned article, A bottom wash coat layer comprising palladium impregnated on a carrier selected from oxygen storage components, alumina components, and combinations thereof, and coated over approximately 60% to approximately 100% of the axial length of the substrate from the inlet axial end to the outlet axial end, A top wash coat layer comprising one or more platinum group metals selected from rhodium, platinum, palladium, and combinations thereof, impregnated on a carrier selected from oxygen storage components, alumina components, and combinations thereof, and coated from either the inlet axial end or the outlet axial end of the substrate to about 60% to about 100% of the axial length of the substrate, wherein the top wash coat layer covers at least about 60% of the length of the bottom wash coat layer. The top wash coat layer comprises a first portion and a second portion, the first portion comprising palladium or platinum optionally supported on a carrier selected from an oxygen storage component, an alumina component, and combinations thereof, starting from the inlet axial end of the substrate, wherein the concentration of palladium or platinum in the first portion is about 2 to about 100 times higher than the concentration of palladium or platinum in the second portion. The first portion has a length of approximately 0.25 inches to approximately 2 inches. If the amount of platinum group metal filling in the first portion is determined axially from the first end of the first portion to the second end of the first portion, then approximately 10 g / ft ３ ~Approx. 1000g / ft ３ The exhaust gas purification catalyst article according to claim 1, comprising a top wash coat layer.

13. The exhaust gas purification catalyst article according to claim 11 or 12, wherein the first portion comprises palladium, and the amount of palladium in the first portion is about 30% to about 100% by weight of the total palladium present in the catalyst article.

14. The exhaust gas purification catalyst article according to claim 11 or 12, wherein the first portion contains platinum, and the amount of platinum in the first portion is about 30% by weight to about 100% by weight of the total platinum present in the catalyst article.

15. The exhaust gas purification catalyst article according to claim 11 or 12, wherein the first portion includes a concentration gradient of palladium or platinum, and the concentration of palladium or platinum decreases exponentially from the top surface of the wash coat layer including the first portion toward the bottom surface of the wash coat layer including the first portion.

16. The exhaust gas purification catalyst article according to any one of claims 1 to 15, wherein the weight ratio of the platinum group metal in the first portion to the platinum group metal in the second portion is in the range of about 4.0 to about 50.

17. The alumina component comprises one or more components selected from alumina, lantana-alumina, ceria-alumina, ceria-zirconia-alumina, zirconia-alumina, lantana-zirconia-alumina, barrier-alumina, barrier-lantana-alumina, barrier-lantana-neodymia-alumina, and combinations thereof. The oxygen storage component comprises one or more components selected from ceria-zirconia, ceria-zirconia-lantana, ceria-zirconia-yttria, ceria-zirconia-lantana-yttria, ceria-zirconia-neodymia, ceria-zirconia-praseodymia, ceria-zirconia-lantana-neodymia, ceria-zirconia-lantana-praseodymia, ceria-zirconia-lantana-neodymia-praseodymia, and combinations thereof. The exhaust gas purification catalyst article according to any one of claims 4, 11, and 12, wherein the zirconia component comprises one or more components selected from lantana-zirconia, barium-zirconia, and combinations thereof.

18. The exhaust gas purification catalyst article according to any one of claims 1 to 17, wherein the bottom wash coat layer contains one or more alkaline earth metal oxides selected from barium oxide, strontium oxide, and combinations thereof, in an amount of about 1.0% to about 20% by weight, based on the total weight of the bottom wash coat layer.

19. The exhaust gas purification catalyst article according to any one of claims 1 to 18, wherein the substrate is a ceramic substrate, a metal substrate, a ceramic foam substrate, a polymer foam substrate, or a woven fiber substrate.

20. A process for preparing exhaust gas purification catalyst articles, The method for preparing a bottom wash coat layer coated over the total length of the substrate from the inlet axial end to the outlet axial end of the substrate comprises: obtaining a slurry containing one or more platinum group metals to be impregnated onto one or more carriers; and coating the total length of the substrate with the slurry. A portion of the bottom wash coat layer, starting from the axial end of the inlet of the substrate, is coated with a platinum group metal solution for a length of approximately 0.25 inches to approximately 2 inches, and then dried and fired at a temperature in the range of approximately 100°C to approximately 140°C to obtain a PGM-enriched zone. A process for preparing an exhaust gas purification catalyst article, comprising: preparing a top wash coat layer which is coated from either the inlet axial end or the outlet axial end of the substrate over about 60% to about 100% of the axial length of the substrate, thereby covering at least about 60% of the length of the bottom wash coat layer, the process comprising: obtaining a slurry containing one or more platinum group metals to be impregnated onto one or more carriers; and coating the slurry over at least about 60% of the length of the bottom wash coat layer.

21. A process for preparing exhaust gas purification catalyst articles, The method for preparing a bottom wash coat layer is to be coated over approximately 60% to approximately 100% of the axial length of the substrate, from the inlet axial end to the outlet axial end of the substrate, and comprises obtaining a slurry containing one or more platinum group metals to be impregnated onto one or more carriers, and coating the slurry over approximately 60% to approximately 100% of the axial length of the substrate. Preparing a top wash coat layer, which is coated from either the inlet axial end or the outlet axial end of the substrate over approximately 60% to approximately 100% of the axial length of the substrate, thereby covering at least approximately 60% of the length of the bottom wash coat layer, comprising: obtaining a slurry containing one or more platinum group metals to be impregnated onto one or more carriers; and coating the slurry over at least approximately 60% of the length of the bottom wash coat. A process for preparing an exhaust gas purification catalyst article, comprising: coating a portion of the top wash coat layer, starting from the inlet axial end of the substrate, with a platinum group metal solution for a length of about 0.25 inches to about 2 inches; and subsequently drying and calcining at a temperature in the range of about 100°C to about 140°C to obtain a PGM enriched zone.

22. An exhaust system for an internal combustion engine, comprising an exhaust catalytic converter article according to any one of claims 1 to 19.

23. A method for treating a gaseous exhaust flow containing hydrocarbons, carbon monoxide, and nitrogen oxides, comprising contacting the exhaust flow with an exhaust purification catalyst article according to any one of claims 1 to 19, or with an exhaust system according to claim 22.

24. A method for reducing the levels of hydrocarbons, carbon monoxide, and nitrogen oxides in a gaseous exhaust flow, comprising bringing the gaseous exhaust flow into contact with an exhaust purification catalyst article according to any one of claims 1 to 19 or an exhaust system according to claim 22, thereby reducing the levels of hydrocarbons, carbon monoxide, and nitrogen oxides in the exhaust gas.

25. Use of an exhaust gas purification catalyst article according to any one of claims 1 to 19 for purifying a gaseous exhaust flow containing hydrocarbons, carbon monoxide, and nitrogen oxides.

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