Manganese-containing catalytic articles, exhaust gas treatment systems, and methods

Abstract

Disclosed herein is a catalytic article comprising a first washcoat comprising a first refractory metal oxide support, platinum, palladium, and optionally a zeolite, and a second washcoat comprising a second refractory metal oxide support, platinum, and manganese. Also disclosed are exhaust gas treatment systems and methods of treating an exhaust gas stream comprising the exhaust gas treatment system.

Description

[Technical field]

[0001] (Priority Claim) This application claims the benefit of priority to European Patent Application No. 21217681.2, filed December 24, 2021, the contents of which are incorporated herein by reference in their entirety.

[0002] FIELD OF THEINVENTION Disclosed herein is a catalytic article comprising a first washcoat comprising a first refractory metal oxide support, platinum, palladium, and optionally a zeolite, and a second washcoat comprising a second refractory metal oxide support, platinum, and manganese. Also disclosed are exhaust gas treatment systems for treating an exhaust gas stream and methods including the same. [Background technology]

[0003] An internal combustion engine, such as a diesel engine, has an exhaust gas stream that includes pollutants such as, for example, particulate matter, oxides of nitrogen, unburned hydrocarbons, and / or carbon monoxide.

[0004] Exhaust gas treatment systems and catalyst articles are exemplary means for abating pollution from internal combustion engines. For example, some exhaust gas treatment systems include a diesel oxidation catalyst upstream of a selective catalytic reduction catalyst. Exemplary diesel oxidation catalysts are useful for abating pollutants such as, for example, unburned hydrocarbons and / or carbon monoxide. Exemplary selective catalytic reduction catalysts are useful for abating pollutants such as, for example, nitrogen oxides (NO x ), however, effective abatement of pollutants may be difficult to achieve in practice. For example, there may be trade-offs between the abatement of various pollutants, between the abatement of pollutants across different operating conditions of the combustion engine, and / or between the performance of various catalyst articles within the exhaust gas treatment system.

[0005] Thus, there is a need for improved catalyst articles, exhaust gas treatment systems, and methods for treating exhaust gas streams. For example, there is a need for catalyst articles, such as diesel oxidation catalysts, that provide enhanced pollution abatement. Additionally, there is a need for catalyst articles, such as diesel oxidation catalysts, that can enhance the performance of downstream catalyst articles in exhaust gas treatment systems. For example, there is a need for catalyst articles, such as diesel oxidation catalysts, that can enhance the performance of downstream selective catalytic reduction catalysts, that can enhance the ratio of NO2 to total NO in the exhaust stream. x There is a need for a diesel oxidation catalyst that can improve the ratio of 1:1, there is a need for a diesel oxidation catalyst that can heat a downstream soot filter to combust soot trapped therein, and there is a need for a diesel oxidation catalyst that can enhance the abatement of unburned hydrocarbons and carbon monoxide. Summary of the Invention

[0006] Some embodiments of the present disclosure relate to a catalyst article comprising a first washcoat comprising a first refractory metal oxide support, platinum, palladium, and optionally a zeolite, and a second washcoat comprising a second refractory metal oxide support, platinum, and manganese.

[0007] In some embodiments, a catalyst article includes a substrate having a length and including an inlet end and an outlet end, a first zone including a first washcoat deposited on at least a portion of the substrate, and a second zone at least partially downstream of the first zone including a second washcoat deposited on at least a portion of the substrate, the first zone having a water vapor permeability of at least 1 g / ft 3 ~220g / ft 3 wherein the first washcoat comprises a first refractory metal oxide support, platinum, palladium, and optionally a zeolite, and the second zone has a total platinum group metal loading in the range of 1 g / ft 3 ~200g / ft 3and the second washcoat comprises a second refractory metal oxide support, platinum in an amount ranging from 2 wt % to 10 wt % of the total weight of the second washcoat, manganese in an amount ranging from 0.5 wt % to 30 wt %, and a weight ratio of platinum to manganese in the range of 1:10 to 20:1.

[0008] In some embodiments, the first and second refractory metal oxide supports each independently comprise at least one metal oxide selected from alumina, silica, titania, ceria, zirconia, and combinations thereof.

[0009] In some embodiments, the second washcoat is essentially free of platinum group metals other than platinum.

[0010] In some embodiments, the second washcoat is essentially free of transition metals other than platinum, manganese, optionally titanium, and optionally zirconium.

[0011] In some embodiments, the first and / or second washcoat comprises platinum nanoparticles.

[0012] In some embodiments, the first refractory metal oxide support comprises palladium.

[0013] In some embodiments, the first washcoat comprises a total platinum group metal content of 0.5% to 10% by weight of the total weight of the first washcoat.

[0014] In some embodiments, the second washcoat comprises between 2% and 10% platinum by weight of the total weight of the second washcoat.

[0015] In some embodiments, the second washcoat comprises 0.5% to 10% manganese by weight of the total weight of the second washcoat.

[0016] In some embodiments, the first washcoat has a weight ratio of platinum to palladium of from 1:1 to 10:1.

[0017] In some embodiments, the weight ratio of platinum in the first washcoat to platinum in the second washcoat ranges from 15:1 to 1:5.

[0018] Also disclosed are exhaust gas treatment systems that include the catalytic articles disclosed herein.

[0019] In some embodiments, an exhaust gas treatment system includes a catalyst article disclosed herein, a catalyzed soot filter, and a selective catalytic reduction catalyst, wherein the catalyzed soot filter and the selective catalytic reduction catalyst are downstream of the catalyst article.

[0020] A method for treating a diesel engine exhaust gas stream is also disclosed.

[0021] In some embodiments, a method of treating a diesel engine exhaust gas stream comprises contacting the exhaust gas stream with a catalytic article disclosed herein.

[0022] In some embodiments, a method of treating a diesel engine exhaust gas stream comprises contacting the exhaust gas stream with an exhaust gas treatment system disclosed herein. [Brief description of the drawings]

[0023] [Figure 1] 1 illustrates an exemplary exhaust gas treatment system consistent with certain embodiments of the present disclosure. [Diagram 2] 1 illustrates an exemplary exhaust gas treatment system consistent with certain embodiments of the present disclosure. [Diagram 3] 2 shows NO2 make for several embodiments of the present disclosure. [Figure 4] 1 shows NO2 production for several embodiments of the present disclosure. [Diagram 5]13 shows light-off results for several embodiments of the present disclosure. [Figure 6] 1 illustrates hydrocarbon conversion for some embodiments of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] Definition: As used herein, "a" or "an" entity refers to one or more of that entity; for example, "a compound" refers to one or more compounds or at least one compound, unless otherwise specified. Thus, the terms "a" (or "an"), "one or more," and "at least one" are used interchangeably herein.

[0025] As used herein, the term "material" refers to elements, components, and / or substances that make up or can make something.

[0026] As used herein, the term "about" refers to a range of ±5% of the stated number. For example, "about 100" means a number in the range of 95 to 105, including, for example, 95, 100, and 105. Unless otherwise specified, all numbers are considered to be modified by "about."

[0027] As used herein, the term "platinum group metals," abbreviated as "PGM," refers to ruthenium, rhodium, palladium, osmium, iridium, platinum, and combinations thereof.

[0028] As used herein, a "catalyzed soot filter" includes a filter for trapping soot particles from the exhaust gas and a catalyst composition for oxidizing the trapped soot particles.

[0029] As used herein, the "loading" of a material, such as a washcoat or metal, on a substrate refers to the dry mass of the material coated on the substrate per unit volume of the substrate. For example, 1 g / in3 A washcoat loading of 1 g / ft 2 on a substrate means that the total dry mass of the washcoat is 1 gram per cubic inch of substrate. 3 A platinum group metal loading of 1 g / in means a total mass of platinum group metal of 1 gram per cubic foot of substrate. The loading of material may be local to a subvolume of the substrate. Such loading is reported as the dry mass of material coated on a subvolume of the substrate per unit volume of the subvolume of the substrate. For example, a substrate may have a first zone of X cubic inches volume on which a total dry washcoat mass of Ag is deposited, and a second zone of Y cubic inches volume on which a total dry washcoat mass of Bg is deposited. In this example, the first zone has a volume of (A / X) g / in 3 and the second zone has a washcoat loading of (B / Y) g / in 3 has a washcoat loading of .

[0030] As used herein, "HC T80" refers to the temperature required during a light-off test to convert 80% of the hydrocarbons present in a gas stream.

[0031] As used herein, "CO T50" refers to the temperature required during a light-off test to convert 50% of the carbon monoxide present in a gas stream.

[0032] As used herein, the term "diesel oxidation catalyst" refers to a catalyst containing a platinum group metal that is capable of oxidizing carbon monoxide and hydrocarbons when contacted with exhaust from a diesel engine.

[0033] As used herein, "NO x " refers to nitrogen oxides and mixtures thereof. Exemplary nitrogen oxides include, but are not limited to, NO, N2O, NO2, and N2O2.

[0034] As used herein, the term "selective catalytic reduction catalyst" refers to a catalyst that converts NO, optionally in the presence of a reducing agent such as NH3, into x This refers to a catalyst that can selectively reduce N2 and water.

[0035] As used herein, "particle size DX" (where X is a number ranging from 0 to 100) refers to a particle size below which approximately X% of the particles have a particle size smaller than. For example, "particle size D90" refers to a particle size below which approximately 90% of the particles have a particle size smaller than.

[0036] As used herein, the term "washcoat" refers to a coating applied to a substrate.

[0037] As used herein, when two entities are in fluid communication and a fluid, such as exhaust gas, flows from a first entity to a second entity, the second entity is "downstream" of the first entity, and there may or may not be one or more additional entities in fluid communication between the first entity and the second entity.

[0038] As used herein, a first entity is "upstream" of a second entity if the second entity is downstream of the first entity.

[0039] As used herein, zeolite framework types are classified by the Structure Commission of the International Zeolite Association according to the rules of the IUPAC Commission on Zeolite Nomenclature, which assigns zeolite framework types a three-letter code and are set out in the Atlas of Zeolite Framework Types, 5th edition, Elsevier, London, England (2001).

[0040] As used herein, a zone on a substrate may or may not at least partially overlap another zone on the substrate.

[0041] As used herein, a layer on a substrate may or may not at least partially overlap another layer on the substrate.

[0042] Catalyst article: In some embodiments, a catalyst article includes a substrate having a length and including an inlet end and an outlet end, a first zone including a first washcoat deposited on at least a portion of the substrate, and a second zone at least partially downstream of the first zone including a second washcoat deposited on at least a portion of the substrate, the first zone having a water vapor permeability of at least 1 g / ft 3 ~220g / ft 3 wherein the first washcoat comprises a first refractory metal oxide support, platinum, palladium, and optionally a zeolite, and the second zone has a total platinum group metal loading in the range of 1 g / ft 3 ~200g / ft 3 and the second washcoat comprises a second refractory metal oxide support, platinum in an amount ranging from 2 wt % to 10 wt % of the total weight of the second washcoat, manganese in an amount ranging from 0.5 wt % to 30 wt %, and a weight ratio of platinum to manganese in the range of 1:10 to 20:1.

[0043] In some embodiments, a catalyst article includes a substrate having a length and including an inlet end and an outlet end, a first zone including a first washcoat deposited on at least a portion of the substrate, and a second zone at least partially downstream of the first zone including a second washcoat deposited on at least a portion of the substrate, the first zone having a water vapor permeability of at least 1 g / ft 3 ~220g / ft 3 wherein the first washcoat comprises a first refractory metal oxide support, platinum, palladium, and a zeolite, and the second zone has a total platinum group metal loading in the range of 1 g / ft 3 ~200g / ft 3and the second washcoat comprises a second refractory metal oxide support, platinum in an amount ranging from 2 wt % to 10 wt % of the total weight of the second washcoat, manganese in an amount ranging from 0.5 wt % to 30 wt %, and a weight ratio of platinum to manganese in the range of 1:10 to 20:1.

[0044] In some embodiments, the second zone has a density of 1 g / ft 3 ~200g / ft 3 In some embodiments, the second zone has a total platinum group metal loading in the range of 10 g / ft 3 ~150g / ft 3 In some embodiments, the second zone has a total platinum group metal loading in the range of 10 g / ft 3 ~50g / ft 3 The total platinum group metal loading ranges from 0.1 to 0.5.

[0045] In some embodiments, the first zone has a tensile strength of 20 g / ft 3 ~200g / ft 3 In some embodiments, the first zone has a total platinum group metal loading in the range of 20 g / ft 3 ~50g / ft 3 In some embodiments, the first zone has a total platinum group metal loading in the range of 80 g / ft 3 ~150g / ft 3 The total platinum group metal loading ranges from 0.1 to 0.5.

[0046] In some embodiments, the first and second refractory metal oxide supports each independently comprise at least one metal oxide selected from alumina, silica, titania, ceria, zirconia, and combinations thereof.

[0047] In some embodiments, the first and second refractory metal oxide supports each independently have a melting point of less than 50 m. 2 / g~500m 2 In some embodiments, the first and second refractory metal oxide supports each independently have a BET surface area in the range of 50 m2 / g~250m 2 In some embodiments, the first and second refractory metal oxide supports each independently have a BET surface area in the range of 70 m 2 / g~150m 2 / g range of BET surface area.

[0048] In some embodiments, the second washcoat further comprises palladium.

[0049] In some embodiments, the second washcoat is essentially free of platinum group metals other than platinum and palladium. In some embodiments, the second washcoat is essentially free of platinum group metals other than platinum.

[0050] In some embodiments, the second washcoat is essentially free of transition metals other than platinum, manganese, optionally titanium, and optionally zirconium. In some embodiments, the second washcoat is essentially free of transition metals other than platinum and manganese. In some embodiments, the second washcoat is essentially free of transition metals other than platinum, manganese, and titanium. In some embodiments, the second washcoat is essentially free of transition metals other than platinum, manganese, titanium, and zirconium. In some embodiments, the second washcoat is essentially free of transition metals other than platinum, manganese, and zirconium.

[0051] In some embodiments, the first washcoat is essentially free of transition metals other than platinum and palladium.

[0052] In some embodiments, the zeolite is beta zeolite. In some embodiments, the first zone has a zeolite concentration of 0.1 g / in 3 ~1g / in 3 The beta zeolite loading ranges from 0.01 to 0.1.

[0053] In some embodiments, the first washcoat comprises at least one functional additive selected from magnesium oxide, calcium oxide, strontium oxide, barium oxide, gallium oxide, indium oxide, germanium oxide, antimony oxide, and combinations thereof.

[0054] In some embodiments, the first and / or second washcoat comprises platinum nanoparticles.

[0055] In some embodiments, the first refractory metal oxide support comprises palladium.

[0056] In some embodiments, the first washcoat comprises a total platinum group metal content of 0.5% to 20% by weight of the total weight of the first washcoat.

[0057] In some embodiments, the second washcoat comprises between 2% and 10% platinum by weight of the total weight of the second washcoat.

[0058] In some embodiments, the second washcoat comprises 0.5% to 10% manganese by weight of the total weight of the second washcoat.

[0059] In some embodiments, the first washcoat has a weight ratio of platinum to palladium from 1:1 to 10:1. In some embodiments, the first washcoat has a weight ratio of platinum to palladium from 1:1 to 5:1.

[0060] In some embodiments, the weight ratio of platinum in the first washcoat to platinum in the second washcoat ranges from 15:1 to 1:5.

[0061] In some embodiments, the first zone has a 1 g / in 3 ~5g / in 3 In some embodiments, the first zone has a washcoat loading in the range of 0.5 g / in 3 ~5g / in3 In some embodiments, the first zone has a higher washcoat loading than the second zone.

[0062] In some embodiments, the first washcoat has a platinum concentration in the range of 0.5% to 5% by weight of the total weight of the first washcoat. In some embodiments, the first washcoat has a palladium concentration in the range of 0.1% to 2% by weight of the total weight of the first washcoat. In some embodiments, the second washcoat has a platinum concentration in the range of 2% to 6% by weight of the total weight of the second washcoat. In some embodiments, the second washcoat has a palladium concentration in the range of 0% to 0.5% by weight of the total weight of the second washcoat.

[0063] In some embodiments, the catalyst article has a viscosity of 10 g / ft 3 ~150g / ft 3 In some embodiments, the catalyst article has a total platinum group metal loading in the range of 10 g / ft 3 ~50g / ft 3 In some embodiments, the catalyst article has a total platinum group metal loading in the range of 50 g / ft 3 ~150g / ft 3 The total platinum group metal loading ranges from 0.1 to 0.5.

[0064] Base material: In some embodiments, one or more washcoats are disposed on one or more substrates, for example to form a catalyst article. In some embodiments, the one or more substrates are three-dimensional, having a length, a diameter, and a volume. In some embodiments, the one or more substrates are cylindrical. In some embodiments, the one or more substrates are not cylindrical. In some embodiments, the one or more substrates have an axial length from an inlet end to an outlet end.

[0065] In some embodiments, one or more of the substrates are ceramic substrates. In some embodiments, the ceramic substrate is made of any suitable refractory material, such as cordierite, cordierite-alpha-alumina, aluminum titanate, silicon titanate, silicon carbide, silicon nitride, zircon-mullite, spodumene, alumina-silica-magnesia, zircon silicate, sillimanite, magnesium silicate, zircon, petalite, alpha-alumina, aluminosilicate, and the like.

[0066] In some embodiments, the substrate comprises one or more metals or metal alloys. In some embodiments, the metal substrate may comprise any metal substrate, such as those having openings or "punch-outs" in the channel walls. In some embodiments, the metal substrate may be used in a variety of shapes, such as pellets, compressed metal fibers, corrugated sheets, or monolithic foams. In some embodiments, the metal substrate comprises a heat-resistant base metal alloy, particularly one in which iron is a substantial or major component. Such alloys may contain one or more of nickel, chromium, and aluminum, the sum of which metals may comprise at least about 15% by weight (weight percent) of the alloy, e.g., about 10% to about 25% by weight chromium, about 1% to about 8% by weight aluminum, and about 0% to about 20% by weight nickel, in each case based on the weight of the substrate. In some embodiments, metal substrates include those with straight channels, those with blades protruding along the axial channels to disrupt the gas flow and open gas flow communication between the channels, and those with blades and also holes to enhance gas transport between channels to enable radial gas transport throughout the monolith.

[0067] In some embodiments, any suitable substrate may be used, such as a monolithic substrate of the type having fine, parallel gas flow passages extending from an inlet face to an outlet face of the substrate such that the passages are open to fluid flow therethrough (a "flow-through substrate"). In some embodiments, the substrate has a plurality of fine, substantially parallel gas flow passages extending along the longitudinal axis of the substrate, where, for example, each passage is blocked at one end of the substrate body, with alternating passages being blocked at opposing end faces (a "wall-flow filter").

[0068] In some embodiments, the substrate comprises a honeycomb substrate in the form of a wall-flow filter or a flow-through substrate. In some embodiments, the substrate is a wall-flow filter. In some embodiments, the substrate is a flow-through substrate.

[0069] In some embodiments, the substrate is a flow-through substrate (e.g., a monolithic substrate, including a flow-through honeycomb monolithic substrate). In some embodiments, the flow-through substrate has fine parallel gas flow passages extending from the inlet end to the outlet end of the substrate such that the flow passages are open to fluid flow. In some embodiments, the passages, which are paths from the inlet to the outlet, have walls on or within which a coating is disposed such that gas flowing through the passage contacts the coated material. In some embodiments, the flow passages of the flow-through substrate are thin-walled channels, which can be of any suitable cross-sectional shape and size, such as trapezoidal, rectangular, square, sinusoidal, hexagonal, elliptical, circular, etc. The flow-through substrate can be ceramic or metallic, as described above.

[0070] In some embodiments, the flow-through substrate is about 50 in 3 ~About 1200in 3 , a cell density (inlet opening) of about 200 to about 400 cpsi, and a wall thickness of about 50 micrometers to about 200 micrometers or about 400 micrometers.

[0071] In some embodiments, the substrate is a wall-flow filter having a plurality of fine passages extending along the longitudinal axis of the substrate. In some embodiments, each passage is blocked at one end of the substrate body, with alternating passages being blocked at the opposing end faces. In some embodiments, the monolithic wall-flow filter substrate may contain up to about 900 or more passages (or "cells") per square inch of cross section, although fewer passages may be used. For example, the substrate may have about 7-600, e.g., about 100-400 cells per square inch ("cpsi"). In some embodiments, the cells have a rectangular, square, circular, oval, triangular, hexagonal, or other polygonal cross section. In some embodiments, the wall-flow filter substrate is ceramic or metallic, as described above.

[0072] In some embodiments, the wall-flow filter article substrate is, for example, about 50 cm 3 , about 100in 3 , about 200in 3 , about 300in 3 , about 400in 3 , about 500in 3 , about 600in 3 , about 700in 3 , about 800in 3 , about 900in 3 , or about 1000 in 3 From about 1500in 3 , about 2000in 3 , about 2500in 3 , about 3000in 3 , about 3500in 3 , about 4000in 3 , about 4500in 3 , or about 5000in 3 In some embodiments, the wall-flow filter substrate has a wall thickness of from about 50 micrometers to about 2000 micrometers, such as from about 50 micrometers to about 450 micrometers or from about 150 micrometers to about 400 micrometers.

[0073] In some embodiments, the wall of the wall-flow filter is porous and has a wall porosity of at least about 40% or at least about 50% and an average pore size of at least about 10 micrometers before the deposition of the functional coating. For example, in some embodiments, the wall-flow filter article substrate has a porosity of ≧40%, ≧50%, ≧60%, ≧65%, or ≧70%. In some embodiments, the wall-flow filter article substrate has a wall porosity of about 50%, about 60%, about 65%, or about 70% to about 75% and an average pore size of about 10 micrometers or about 20 micrometers to about 30 micrometers or about 40 micrometers before the deposition of the catalytic coating. The terms "wall porosity" and "substrate porosity" mean the same thing and are used interchangeably herein. Porosity is the ratio of void volume (or pore volume) divided by the total volume of the substrate material. Pore size and pore size distribution can be determined, for example, by Hg porosimetry measurements.

[0074] Wash Coat: In some embodiments, the slurry is coated onto the substrate using washcoat techniques known in the art. Washcoats are, for example, as described in Heck, Ronald and Farrauto, Robert, Catalytic Air Pollution Control, New York: Wiley-Interscience, 2002, pp.18-19, as compositionally distinct layers of material disposed on the surface of a monolithic substrate or an underlying washcoat layer. In some embodiments, the substrate contains one or more washcoat layers, and each washcoat layer may have a different composition.

[0075] In some embodiments, the substrate is dipped into or otherwise coated, e.g., sprayed, with the slurry one or more times. In some embodiments, the coated substrate is dried at an elevated temperature (e.g., 100° C.-150° C.) in still air or under a stream or jet of air for about 2 minutes to about 3 hours, and then calcined, e.g., by heating at 400° C.-600° C. for about 10 minutes to about 3 hours. In some embodiments, after drying and calcining, the final washcoat coating layer is essentially solvent-free.

[0076] In some embodiments, after calcination, the washcoat loading can be determined by calculating the difference between the coated and uncoated weights of the substrate. As will be apparent to one skilled in the art, the washcoat loading can be altered by varying the rheology of the slurry, the solids content, or the number of coating runs. In some embodiments, the coating / drying / calcining process is repeated as necessary to build up a coating of the desired loading level or thickness.

[0077] In some embodiments, the composition is applied as a single layer or in multiple layers. In some embodiments, the layer obtained by repeatedly washcoating the same material to increase the loading level is a single layer. In some embodiments, the composition may be zone coated, meaning that a single substrate may be coated with different catalyst compositions in different regions along the axial gas effluent flow path.

[0078] In some embodiments, the composition is mixed with water to form a slurry for the purpose of coating a substrate. In some embodiments, the slurry further comprises an inorganic binder, an associative thickener, or a surfactant (e.g., one or more anionic, cationic, nonionic, or amphoteric surfactants). The order of addition may be varied, in some embodiments, all of the components are simply combined together to form the slurry, and in some embodiments, certain components are combined and then the remaining components are combined with it. In some embodiments, the pH of the slurry may be adjusted to an acidic pH, for example, from about 3 to about 5.

[0079] In some embodiments, the slurry is milled. In some embodiments, the milling is performed in a ball mill, continuous mill, or other similar equipment, and the solids content of the slurry can be, for example, about 20% to about 60% by weight, about 30% to about 40% by weight. In some embodiments, the milled slurry is characterized by a D90 particle size of about 10 micrometers to about 50 micrometers (e.g., about 10 micrometers to about 20 micrometers).

[0080] In some embodiments, the first and second washcoats are in a layered relationship. In some embodiments, the first and second washcoats are in a layered relationship, where the first washcoat is stacked on top of the second washcoat that is stacked directly on the substrate. In some embodiments, the first and second washcoats are in a layered relationship, where the second washcoat is stacked on top of the first washcoat that is stacked directly on the substrate.

[0081] In some embodiments, the first and second washcoats are in a zonal relationship. In some embodiments, the first washcoat is in an upstream zone and the second washcoat is in a downstream zone. In some embodiments, the first washcoat is coated on x% of the axial length of the substrate, where x is in the range of greater than 0% to less than 100% from the inlet face of the coated structure. In some embodiments, the second washcoat is coated on y% of the axial length of the substrate, where y is in the range of greater than 0% to less than 100% from the outlet face of the coated structure. In some embodiments, x% is 10% and y% is 90%. In some embodiments, x% is 20% and y% is 80%. In some embodiments, x% is 30% and y% is 70%. In some embodiments, x% is 40% and y% is 60%. In some embodiments, x% is 50% and y% is 50%. In some embodiments, x% is 60% and y% is 40%. In some embodiments, x% is 70% and y% is 30%. In some embodiments, x% is 80% and y% is 20%. In some embodiments, x% is 90% and y% is 10%.

[0082] In some embodiments, the first and second washcoats are in a zonal and layered relationship, with a portion of the first washcoat overlapping a portion of the second washcoat. In some embodiments, the first washcoat is directly or indirectly coated on x% of the axial length of the substrate, where x is in the range of greater than 0% to less than 100% from the inlet face of the coated structure. In some embodiments, the second washcoat is directly or indirectly coated on y% of the axial length of the substrate, where y is in the range of greater than 0% to less than 100% from the outlet face of the coated structure. In some embodiments, x%+y% is in the range of 100% to 180%. In some embodiments, x%+y% is in the range of 100% to 150%. In some embodiments, x%+y% is in the range of 100% to 120%. In some embodiments, x%+y% is in the range of 100% to 110%. In some embodiments, x%+y% is in the range of 100% to 105%. In some embodiments, a portion of the first washcoat and a portion of the second washcoat overlap such that x%+y% is greater than 100%. In some embodiments, the first washcoat overlaps with the second washcoat. In some embodiments, the second washcoat overlaps with the first washcoat.

[0083] In some embodiments, a second washcoat is at least partially stacked on top of the first washcoat, the second washcoat comprising Pt, Mn, Zr, and optionally Pd.

[0084] Zeolite: In some embodiments, the first washcoat includes zeolite. In some embodiments, the zeolite is ABW, ACO, AEI, AEL, AEN, AET, AFG, AFI, AFN, AFO, AFR, AFS, AFT, AFV, AFX, AFY, AHT, ANA, APC, APD, AST, ASV, ATN, ATO, ATS, ATT, ATV, AVL, AWO, AWW, BCT, BEA, BEC, BIK, BOF, BOG, BOZ, BPH, BRE, BSV, CAN, CAS, CDO, CFI, CGF, CGS, CHA, -CHI, -CLO, CON, CSV, CZP, DAC, DDR, DFO, DFT, DOH, DON, EAB, EDI, EEI, EMT, EON, EPI, ERI, ESV, ETR, EUO, * -EWT, EZT, FAR, FAU, FER, FRA, GIS, GIU, GME, GON, GOO, HEU, IFO, IFR, -IFU, IFW, IFY, IHW, IMF, IRN, IRR, -IRY, ISV, ITE, ITG, ITH, * -ITN, ITR, ITT, -ITV, ITW, IWR, IWS, IVW, IWW, JBW, JNT, JOZ, JRY, JSN, JSR, JST, JSW, KFI, LAU, LEV, LIO, -LIT, LOS, LOV, LTA, LTF, LTJ, LTL, LTN, MAR, MAZ, MEI, MEL, MEP, MER, MFI, MFS, MON, MOR, MOZ, * MRE, MSE, MSO, MTF, MTN, MTT, MTW, MVY, MWF, MWW, NAB, NAT, NES, NON, NPO, NPT, NSI, OBW, OFF, OKO, OSI, OSO, OWE, -PAR, PAU, PCR, PHI, PON, POS, PSI, PUN, RHO, -RON, RRO, RSN, RTE, RTH, RUT, RWR, RWY, SAF, SAO, SAS, SAT, SAV, SBE, SBN, SBS, SBT, SEW, SFE, SFF, SFG, SFH, SFN, SFO, SFS, * SFV, SFW, SGT, SIV, SOD, SOF, SOS, SSF, * -SSO, SSY, STF, STI, *The zeolite has a framework type selected from STO, STT, STW, -SVR, SW, SZR, TER, THO, TOL, TON, TSC, TUN, UEI, UFI, UOS, UOV, UOZ, USI, UTL, UWY, VET, VFI, VNI, VSV, WEI, -WEN, YUG, ZON, and combinations thereof. In some embodiments, the zeolite contains 10-membered rings and / or 12-membered rings. In some embodiments, the zeolite is selected from beta zeolite (BEA), ferrierite zeolite (FER), Zeolite Socony Mobil-5 zeolite (ZSM-5), and faujasite zeolite (FAU).

[0085] Exhaust Gas Treatment System: In some embodiments, an exhaust gas treatment system includes an engine and a catalytic article disclosed herein.

[0086] In some embodiments, an exhaust gas treatment system includes a catalyst article disclosed herein upstream of a catalyst composition comprising a zeolite ion-exchanged with copper and / or iron, where the catalyst article and the catalyst composition are on different substrates. In some embodiments, an exhaust gas treatment system includes a catalyst article disclosed herein upstream of a catalyst composition comprising a zeolite ion-exchanged with copper and / or iron, where the catalyst article and the catalyst composition are on the same substrate.

[0087] In some embodiments, an exhaust gas treatment system includes a catalytic article disclosed herein upstream of a selective catalytic reduction catalyst. In some embodiments, an exhaust gas treatment system includes a catalytic article disclosed herein upstream of a catalyzed soot filter.

[0088] FIG. 1 shows an exemplary exhaust gas treatment system (100) including an engine (101), a diesel oxidation catalyst (102), a reductant injector (105) for injecting a reductant such as urea or ammonia, a selective catalytic reduction catalyst (103), and optionally a catalyzed soot filter (104).

[0089] FIG. 2 shows an exemplary exhaust gas treatment system (200) including an engine (201), a diesel oxidation catalyst (202), a reductant injector (205) for injecting a reductant such as urea or ammonia, a catalyzed soot filter (203), and a selective catalytic reduction catalyst (204).

[0090] Methods for treating exhaust gases: In some embodiments, a method of treating an exhaust gas comprises contacting the exhaust gas with a catalytic article disclosed herein. In some embodiments, a method of treating an exhaust gas comprises contacting the exhaust gas with an exhaust gas treatment system disclosed herein.

[0091] Catalyzed soot filters: Catalyzed soot filters provide an exemplary means for trapping and oxidizing soot particles entrained in an engine exhaust stream. A non-limiting exemplary catalyzed soot filter includes a catalyst composition including a platinum group metal, the catalyst composition being deposited on a wall-flow substrate filter. Non-limiting exemplary catalyzed soot filters are disclosed in International Application No. PCT / US2004 / 024864, filed July 30, 2004, International Application No. PCT / US2006 / 043574, filed November 8, 2006, International Application No. PCT / US2007 / 086095, filed November 30, 2007, International Application No. PCT / US2016 / 024889, filed March 30, 2016, and International Application No. PCT / US2011 / 061681, filed November 21, 2011, the disclosures of each of which are incorporated herein by reference in their entirety.

[0092] Selective catalytic reduction catalyst: Selective catalytic reduction catalysts provide an exemplary means for selectively reducing nitrogen oxides entrained in engine exhaust streams. Non-limiting exemplary selective catalytic reduction catalysts include zeolites ion-exchanged with copper and / or iron. Non-limiting exemplary selective catalytic reduction catalysts are disclosed in International Application No. PCT / IB2011 / 051526, filed April 8, 2011, International Application No. PCT / US2013 / 065498, filed October 17, 2013, International Application No. PCT / EP2019 / 069878, filed July 24, 2019, International Application No. PCT / EP2019 / 079081, filed October 24, 2019, and International Application No. PCT / US2016 / 019842, filed February 26, 2016, the disclosures of each of which are incorporated herein by reference in their entirety.

[0093] Non-limiting exemplary embodiments: Without being limited thereto, some embodiments of the present disclosure include: 1. A method for producing a washcoat comprising: a substrate having a length and including an inlet end and an outlet end; a first zone including a first washcoat deposited on at least a portion of the substrate; and a second zone at least partially downstream of the first zone including a second washcoat deposited on at least a portion of the substrate, the first zone having a washcoat content of at least 1 g / ft 3 ~220g / ft 3 wherein the first washcoat comprises a first refractory metal oxide support, platinum, palladium, and optionally a zeolite, and the second zone has a total platinum group metal loading in the range of 1 g / ft 3 ~200g / ft 3 and the second washcoat comprises a second refractory metal oxide support, platinum in an amount ranging from 2 wt % to 10 wt % of the total weight of the second washcoat, manganese in an amount ranging from 0.5 wt % to 30 wt %, and a weight ratio of platinum to manganese in the range of 1:10 to 20:1. 2. The catalytic article of embodiment 1, wherein the first and second refractory metal oxide supports each independently comprise at least one metal oxide selected from alumina, silica, titania, ceria, zirconia, and combinations thereof. 3. The catalytic article of embodiment 1 or 2, wherein the second washcoat is essentially free of platinum group metals other than platinum. 4. The catalytic article of any one of embodiments 1-3, wherein the second washcoat is essentially free of transition metals other than platinum, manganese, optionally titanium, and optionally zirconium. 5. The catalytic article of any one of embodiments 1-4, wherein the first and / or second washcoat comprises platinum nanoparticles. 6. The catalytic article of any one of the preceding embodiments, wherein the first refractory metal oxide support further comprises palladium. 7. The catalytic article of any one of the preceding embodiments, wherein the first washcoat comprises a total platinum group metal content of 0.5% to 10% by weight of the total weight of the first washcoat. 8. The catalytic article of any one of the preceding embodiments, wherein the second washcoat comprises 2 wt.% to 10 wt.% platinum based on the total weight of the second washcoat. 9. The catalytic article of any one of the preceding embodiments, wherein the second washcoat comprises 0.5 wt.% to 30 wt.% manganese based on the total weight of the second washcoat. 10. The catalytic article of any one of the preceding embodiments, wherein the first washcoat has a weight ratio of platinum to palladium of 1:1 to 10:1. 11. The catalytic article of any one of the preceding embodiments, wherein the weight ratio of platinum in the first washcoat to platinum in the second washcoat ranges from 15:1 to 1:5. 12. An exhaust gas treatment system comprising the catalytic article according to any one of embodiments 1 to 11. 13. An exhaust gas treatment system comprising the catalyst article of any one of embodiments 1 to 11, a catalyzed soot filter, and a selective catalytic reduction catalyst, the catalyzed soot filter and the selective catalytic reduction catalyst being downstream of the catalyst article. 14. A method of treating a diesel engine exhaust gas stream comprising contacting said exhaust gas stream with a catalytic article according to any one of embodiments 1-11. EXAMPLES

[0094] The following examples are intended to be illustrative and are not meant to limit the scope of the disclosure in any way.

[0095] Example 1 was prepared by separately coating front and rear zone segments onto 1 inch diameter by 1.5 inch long cordierite honeycomb substrates and then sequentially combining the coated cores for subsequent aging and testing. First, a 5% silica containing 150 mm thick core was coated onto a 1 inch diameter by 1.5 inch long cordierite honeycomb substrate and then sequentially combining the coated cores for subsequent aging and testing. 2 / g and a BET surface area of ​​approximately 0.6 cm 3 The front zone segment was prepared by impregnating a commercial alumina support powder with a pore volume of 100000 / g with a Pd nitrate solution. After adding twice the weight percent of Pd with barium hydroxide, the impregnated powder was combined with a solution containing Pt nanoparticles dispersed in water. The resulting mixture was milled to a particle size suitable for coating, after which beta zeolite and boehmite alumina binder were added. The resulting slurry was then coated onto a cordierite substrate, which was dried and subsequently calcined at 590°C for 1 hour. The rear zone segment was first prepared by impregnating a commercial alumina support powder with a pore volume of 100000 / g with a Pd nitrate solution. After adding barium hydroxide at a weight percent of 2 times the weight of Pd with barium hydroxide, the impregnated powder was combined with a solution containing Pt nanoparticles dispersed in water. The resulting mixture was milled to a particle size suitable for coating, after which beta zeolite and boehmite alumina binder were added. The resulting slurry was then coated onto a cordierite substrate, which was dried and subsequently calcined at 590°C for 1 hour. The rear zone segment was first prepared by impregnating a 5% manganese dioxide containing approximately 150 m 2 / g and a BET surface area of ​​approximately 0.8 cm 3A commercially available alumina support powder with a pore volume of 10000 / g was prepared by combining a solution containing Pt nanoparticles dispersed in water. The resulting mixture was ground to a particle size suitable for coating, after which a boehmite alumina binder was added. The resulting slurry was then coated onto a cordierite substrate, which was dried and subsequently calcined at 590 °C for 1 h.

[0096] Front zone: 1.5g / in 3 Pt-Pd in ​​a 4:1 weight ratio supported on 5% SiO2-Al2O3, 0.45 g / in 3 of beta zeolite, and 0.10 g / in 3 2.08 g / in containing boehmite binder 3 The Pt loading was 30.3 g / ft based on the volume of the front zone core alone. 3 and Pd loading is 7.6g / ft 3 The rear zone was Pt supported on 5% MnO2-Al2O3 and 0.02 g / in 3 of boehmite binder at 0.3 g / in 3 The Pt loading was 32.1 g / ft based on the volume of the aft zone core alone. 3 The total Pt-Pd loading of the forward zone + aft zone assembly was 35g / ft based on the combined volume of the forward and aft zones. 3 It was.

[0097] In Example 2, the Pt support used in the rear zone was 1.5 g / in 3 The alloy was prepared similarly to Example 1, except that it contained 5% MnO2-Al2O3. The Pt loading was 32.1 g / ft2 based on the volume of the aft zone core alone. 3 It was.

[0098] In Example 3, the Pt support used in the rear zone was 2.5 g / in 3 The alloy was prepared similarly to Example 1, except that it contained 5% MnO2-Al2O3. The Pt loading was 32.1 g / ft2 based on the volume of the aft zone core alone.3 It was.

[0099] In Example 4, the Pt support used in the rear zone contained about 20% manganese dioxide and was about 200 m 2 / g and a BET surface area of ​​approximately 0.4 cm 3 / g, with a pore volume of 1.5 g / in 3 The alloy was prepared similarly to Example 1, except that it contained 100% zirconia support powder. The Pt loading was 32.1 g / ft based on the volume of the aft zone core alone. 3 It was.

[0100] Example 5 was prepared similarly to Example 4, except that the PGM in the rear zone contained a 9:1 weight ratio of Pt-Pd instead of Pt. Based on the volume of the rear zone core alone, the Pt loading was 28.8 g / ft 3 and the Pd loading is 3.2g / ft 3 It was.

[0101] Additional examples were made according to the procedures above and had the properties disclosed in Tables 1, 2, and 3. The 1% Y-containing supports used in Examples 6, 7, 8, 10, and 12 were prepared by impregnating the 5% SiO2-Al2O3 supports of Examples 1-5 with a Y nitric acid solution using methods commonly known in the art. The alumina supports of Examples 15, 17, and 18 were prepared by impregnating the 5% SiO2-Al2O3 supports of Examples 1-5 with a Y nitric acid solution using methods commonly known in the art. 2 / g and a BET surface area of ​​approximately 1.0 cm 3 / g pore volume.

[0102] [Table 1]

[0103] [Table 2]

[0104] Hydrothermal Aging: Prior to testing for catalytic activity, Examples 1-12 were aged in the presence of steam at elevated temperatures using conditions relevant for light duty diesel applications (i.e. cars, vans, etc.). Samples were exposed to flowing gas containing 10% water vapor (H2O) in air at 800°C for 16 hours. Examples 13-18 were aged in the presence of steam at elevated temperatures using conditions relevant for heavy duty diesel applications (i.e. trucks, buses, etc.). Samples were exposed to flowing gas containing 10% water vapor (H2O) in air at 650°C for 50 hours. All hydrothermal aging conditions are summarized in Table 3.

[0105] [Table 3]

[0106] Testing: After aging, Examples 1-12 were tested in a laboratory reactor using conditions relevant for light duty diesel applications (i.e. cars, vans, etc.). The reaction gas composition consisted of 1450 ppm CO, 30 ppm-C1 CH4, 120 ppm-C1 C3H6, 216 ppm-C1 decane, 84 ppm-C1 toluene, 120 ppm NO, 15% O2, 5% CO2, 10% H2O, and the balance N2. The temperature of the catalyst was increased from 80°C to 400°C at 20°C / min. The flow through the catalyst, expressed as space velocity, was 56,000 / h. The concentrations of CO, HC, and NOx (NO, NO2, and N2O) were measured at the reactor outlet as a function of temperature during the course of the test. The conversion of CO and HC was calculated by comparing the inlet and outlet concentrations. The ratio of NO2 to total NOx was calculated by dividing the amount of NO2 by the amount of NO in the inlet gas stream. The ppm-C1 values ​​are calculated based on the number of carbon atoms in a particular component, not the number of molecules. For example, methane only has one carbon, so the ppm-C1 is the same as the ppm value on a molecular basis. However, propylene has three carbon atoms per molecule (C3H6), so 120 ppm-C1 = 40 ppm propylene on a molecular basis.

[0107] After aging, Examples 14-19 were tested in a laboratory reactor using conditions relevant to heavy duty diesel applications (i.e. trucks, buses, etc.). The reaction gas composition consisted of 100 ppm CO, 33 ppm-C1 C3H6, 33 ppm-C1 decane, 33 ppm-C1 toluene, 600 ppm NO, 10% O2, 7% CO2, 5% H2O, and balance N2. The temperature of the catalyst was increased from 100°C to 500°C at 12°C / min. The flow through the catalyst, expressed as space velocity, was 60,000 / h. The concentrations of CO, HC, and NOx, NO, NO2, and N2O were measured at the outlet of the reactor as a function of temperature during the course of the test. The conversion of CO and HC was calculated by comparing the inlet and outlet concentrations. The ratio of NO2 to total NOx was calculated by dividing the amount of NO2 by the amount of NO in the inlet gas stream.

[0108] Exit NO2 / NO as a function of temperature for Examples 1-3 before and after hydrothermal aging at 800°C x The results are provided in Figure 3. Outlet NO2 / NO as a function of temperature for Examples 2, 4, and 5 after hydrothermal aging at 800°C. x The results are provided in Figure 4. The CO and HC light-off and NO2 / NOx results at 200°C for Examples 2, 4, and 5 after 800°C hydrothermal aging are provided in Figure 5. The hydrocarbon conversion results as a function of temperature for Examples 2, 4, and 5 after 800°C hydrothermal aging are provided in Figure 6. The NO2 / NOx results at 200°C for Examples 6-18 after 650°C or 800°C hydrothermal aging are provided in Table 4.

[0109] [Table 4]

[0110] Comparing Examples 1-3, which were tested using conditions relevant to light duty diesel applications, the inlet NO xThe NO oxidation performance, expressed as the ratio of evolved NO2 to concentration, was highest for Example 1 with a rear zone Pt concentration of 5.8%. This was true for both the fresh catalyst and the catalyst steam aged at 800°C. Furthermore, the change in performance from fresh to aged was the smallest for Example 1. Example 3 with a rear zone Pt concentration of 0.7% had the lowest fresh performance, while the performance after aging was essentially the same for Examples 2 and 3. Overall, a significant improvement in NO oxidation performance was realized when the Mn-alumina support was combined with a high concentration of Pt in the rear zone.

[0111] Comparing Examples 6-12, which were tested using conditions relevant to light duty diesel applications, the inlet NO x The NO oxidation performance, expressed as the ratio of evolved NO2 to concentration, was lowest for Example 12, which had a rear zone Pt concentration of only 1.7%. Comparing Examples 13-18, which were tested using conditions relevant to heavy duty diesel applications, the inlet NO x The NO oxidation performance, expressed as the ratio of NO2 evolved to concentration, was lowest for Examples 14 and 18, which had rear zone Pt concentrations below 1.6%. Overall, significant improvements in NO oxidation performance were realized when the Mn-alumina support was combined with a high concentration of Pt in the rear zone.

[0112] Comparing Examples 2, 4, and 5, which were tested using conditions relevant to light duty diesel applications, the carbon monoxide T50 light-off temperature was reduced by about 5° C. for Examples 4 and 5, which contained about 20% MnO2-ZrO2 in the rear zone, versus Example 2, which contained about 5% MnO2-Al2O3 in the rear zone. The HC T80 was reduced by about 10° C. Additionally, the inlet total NO x The ratio of NO2 generated to concentration was highest in Examples 4 and 5. Significant improvements in carbon monoxide, hydrocarbon, and NO oxidation performance were realized when Mn-zirconia supports were used in Examples 4 and 5 to support Pt or Pt-Pd, relative to Mn-alumina material supports as in Example 2.

[0113] Without being bound by theory, one of ordinary skill in the art would recognize that a washcoat having a high platinum loading (e.g., the second washcoat having an amount of platinum ranging from 5 wt. % to 10 wt. % of the total weight of the second washcoat) and / or a low washcoat loading (e.g., the second washcoat having an amount of platinum ranging from 0.5 g / in 3 It is believed that no one would have prepared a catalyst article with a washcoat loading below 0.5 g / in 2 (e.g., 0.5 wt. %). For example, higher platinum loadings (e.g., 5 wt. % or more) may be more expensive, and there is no basis to conclude that one skilled in the art would have been motivated to include greater amounts of platinum. Similarly, for example, lower washcoat loadings (e.g., 0.5 g / in 2 or more) may be more expensive, and there is no basis to conclude that one skilled in the art would have been motivated to include greater amounts of platinum. 3 (below) would provide less catalytic material and there is no basis to conclude that one skilled in the art would be motivated to include such low washcoat loadings with any reasonable expectation that such low washcoat loadings would render the catalytic article unsatisfactory for its intended purpose. Thus, Applicants' Examples surprisingly demonstrate that a combination of features (e.g., platinum and manganese amounts and washcoat loadings) provides improved catalytic performance.

[0114] Unless indicated to the contrary or clear from the context, a claim or specification condition containing "or" or "and / or" between at least one member of a group is deemed satisfied when one, more than one, or all of the members of a group are present in, used in, or otherwise relevant to a given product or process. The present disclosure includes embodiments in which exactly one group member is present in, used in, or otherwise relevant to a given product or process. The present disclosure includes embodiments in which more than one or all of the members of a group are present in, used in, or otherwise relevant to a given product or process.

[0115] Furthermore, the disclosure encompasses all variations, combinations, and permutations in which at least one limitation, element, clause, and descriptive term from at least one of the enumerated claims is introduced into another claim. For example, any claim that is dependent on another claim may be modified to include at least one limitation found in any other claim that is dependent on the same independent claim. When elements are presented as a list, such as in Markush group format, each subgroup of elements is also disclosed, and any element(s) can be removed from the group. In general, when the disclosure or aspects of the disclosure are referred to as including certain elements and / or features, it should be understood that the embodiments of the disclosure or aspects of the disclosure consist of or consist essentially of such elements and / or features. For the sake of brevity, these embodiments have not been specifically described in this language herein. When ranges are given, the endpoints are included. Furthermore, unless otherwise indicated or clear from the context and understanding of one of ordinary skill in the art, values ​​expressed as ranges can assume any particular value or subrange within the stated range in different embodiments of the disclosure, unless the context clearly indicates otherwise.

[0116] Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the specific embodiments of the disclosure described herein which equivalents are intended to be encompassed by the following claims.

Claims

1. 1. A catalytic article comprising: a substrate having a length and including an inlet end and an outlet end; a first zone including a first washcoat deposited on at least a portion of the substrate; a second zone at least partially downstream of the first zone, the second zone including a second washcoat deposited on at least a portion of the substrate; Including, The first zone has a viscosity of 1 g / ft ３ ~220g / ft ３ and having a total platinum group metal loading in the range of the first washcoat comprising a first refractory metal oxide support, platinum, palladium, and optionally a zeolite; The second zone has a viscosity of 1 g / ft ３ ~200g / ft ３ and having a total platinum group metal loading in the range of 1. A catalytic article, wherein the second washcoat comprises a second refractory metal oxide support, platinum in an amount ranging from 2 wt. % to 10 wt. % of the total weight of the second washcoat, manganese in an amount ranging from 0.5 wt. % to 30 wt. %, and a weight ratio of platinum to manganese ranging from 1:10 to 20:

1.

2. 10. The catalyst article of claim 1, wherein the first refractory metal oxide support and the second refractory metal oxide support each independently comprise at least one metal oxide selected from alumina, silica, titania, ceria, zirconia, and combinations thereof.

3. 3. The catalytic article of claim 1 or 2, wherein the second washcoat is essentially free of platinum group metals other than platinum and / or the second washcoat is essentially free of transition metals other than platinum, manganese, optionally titanium, and optionally zirconium.

4. 3. The catalytic article of claim 1 or 2, wherein the first and / or second washcoat comprises platinum nanoparticles.

5. 3. The catalytic article of claim 1 or 2, wherein the first refractory metal oxide support comprises palladium.

6. 3. The catalytic article of claim 1, wherein the first washcoat comprises a total platinum group metal content of 0.5 wt. % to 20 wt. % of the total weight of the first washcoat, and / or the second washcoat comprises 2 wt. % to 10 wt. % of platinum of the total weight of the second washcoat, and / or the second washcoat comprises 0.5 wt. % to 10 wt. % of manganese of the total weight of the second washcoat.

7. 3. The catalytic article of claim 1 or 2, wherein the first washcoat has a weight ratio of platinum to palladium of from 1:1 to 10:1, and / or the weight ratio of platinum in the first washcoat to platinum in the second washcoat is in the range of from 15:1 to 1:

5.

8. 3. An exhaust gas treatment system comprising the catalyst article of claim 1 or 2, and optionally a catalyzed soot filter and a selective catalytic reduction catalyst, the catalyzed soot filter and the selective catalytic reduction catalyst being downstream of the catalyst article.

9. A method for treating a diesel engine exhaust gas stream comprising contacting said exhaust gas stream with the catalytic article of claim 1 or 2.

10. The catalytic article of claim 1 or 2, wherein the second washcoat further comprises palladium.

11. 3. The catalytic article of claim 1 or 2, wherein the second washcoat comprises 0.5 wt. % to 25 wt. % manganese based on the total weight of the second washcoat.

12. 3. The catalytic article of claim 1 or 2, wherein the catalytic article comprises a zeolite, the zeolite comprising 10-membered rings and / or 12-membered rings, and optionally the zeolite is selected from beta zeolite (BEA), ferrierite zeolite (FER), Zeolite Socony Mobil-5 zeolite (ZSM-5), and faujasite zeolite (FAU).

13. 3. The catalytic article of claim 1 or 2, wherein the first washcoat comprises a total platinum group metal content of 0.5 wt. % to 10 wt. % or 0.5 wt. % to 5 wt. % of the total weight of the first washcoat.

14. 3. The catalytic article of claim 1 or 2, wherein the catalytic article includes a third zone where a portion of the first washcoat and a portion of the second washcoat overlap, and optionally, in the third zone, the portion of the first washcoat is between the substrate and the portion of the second washcoat.

15. the first washcoat is coated directly or indirectly on x% of the axial length of the substrate; the second washcoat is coated directly or indirectly on y% of the axial length of the substrate; x is in the range of greater than 0% to less than 100% from the inlet face of the coated structure; y ranges from greater than 0% to less than 100% from the exit face of the coated structure; 3. The catalytic article of claim 1, wherein x%+y% is in the range of 80% to 180%.

16. 3. The catalytic article of claim 1 or 2, wherein the second washcoat has platinum in an amount ranging from 5% to 10% by weight of the total weight of the second washcoat.

17. The second washcoat is 0.5 g / in ３ 3. The catalytic article of claim 1 or 2, wherein the catalytic article is present at a washcoat loading of:

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