Platinum Group Metal Capture Materials

Abstract

Disclosed herein is a platinum group metal capture material comprising an alkaline earth metal oxide. Disclosed herein are also catalytic articles, exhaust gas treatment systems, and methods of treating exhaust gases comprising the same. Some embodiments of the disclosure relate to a gas treatment system comprising a means for oxidizing carbon monoxide and oxidizing hydrocarbons, a means for capturing volatilized platinum group metals, and a means for selectively reducing nitrogen oxides.

Description

[Technical field]

[0001] (Priority Claim) This application claims the benefit of priority to International Application No. PCT / CN2021 / 122206, filed September 30, 2021, the disclosure of which is incorporated herein by reference in its entirety.

[0002] FIELD OF THEINVENTION Disclosed herein are platinum group metal capture materials comprising alkaline earth metal oxides, as well as catalytic articles, exhaust gas treatment systems, and methods of treating exhaust gases including the same. [Background technology]

[0003] Platinum group metals can volatilize when exposed to high temperatures. For example, platinum group metals in various catalytic and exhaust gas treatment systems can volatilize when exposed to exhaust gases. In some cases, the volatilized platinum group metals can be problematic, for example, they can poison downstream catalysts. For example, if NO 2 is present downstream of an oxidation catalyst that contains a platinum group metal, x In exhaust gas systems with reducing components, the exhaust gas volatilizes some of the platinum group metals in the oxidation catalyst and transports the volatilized platinum group metals downstream of the NO x It can be transported to a reducing component, where NO x This may impair the ability of the reducing component to function properly. Summary of the Invention [Problem to be solved by the invention]

[0004] Therefore, there is a need for platinum group metal capture materials that can capture volatilized platinum group metals generated during high temperature use cases for catalytic and exhaust gas treatment systems. [Means for solving the problem]

[0005] Some embodiments of the present disclosure relate to platinum group metal capture materials (such as Pt traps) that include alkaline earth metal oxides.

[0006] In some embodiments, the platinum group metal capture material comprises an alkaline earth metal oxide, the platinum group metal capture material is free of transition metals, optionally except for zirconium, and the platinum group metal capture material is free of alkaline earth metals.

[0007] In some embodiments, the alkaline earth metal oxide is selected from magnesium oxide, barium oxide, calcium oxide, strontium oxide, and combinations thereof.

[0008] In some embodiments, the platinum group metal capture material further comprises at least one metal oxide selected from alumina, zirconia, and combinations thereof.

[0009] In some embodiments, the platinum group metal capture material has about 30% to about 100% magnesium oxide by weight, based on the total weight of the platinum group metal capture material.

[0010] In some embodiments, the platinum group metal capture material consists essentially of magnesium oxide.

[0011] In some embodiments, the platinum group metal capture material consists essentially of aluminum magnesium oxide, zirconia magnesium oxide, aluminum calcium oxide, zirconia calcium oxide, or combinations thereof, hi some embodiments, the platinum group metal capture material consists essentially of aluminum magnesium oxide, zirconia magnesium oxide, aluminum calcium oxide, or zirconia calcium oxide.

[0012] Some embodiments of the present disclosure relate to catalytic articles that include platinum group metal capture materials.

[0013] In some embodiments, the catalyst article comprises a platinum group metal capture material disclosed herein downstream of a catalyst composition comprising a platinum group metal.

[0014] In some embodiments, the platinum group metal capture material has a metal content of at least about 0.1 g / in 3 The washcoat loading is

[0015] In some embodiments, the platinum group metal capture material and the catalyst composition are in a layered and / or zoned arrangement. In some embodiments, the platinum group metal capture material and the catalyst composition are in a layered arrangement. In some embodiments, the platinum group metal capture material and the catalyst composition are in a zoned arrangement.

[0016] Some embodiments of the present disclosure relate to exhaust gas treatment systems that include a platinum group metal capture material.

[0017] In some embodiments, an exhaust gas treatment system comprises an engine and a catalytic article disclosed herein.

[0018] In some embodiments, an exhaust gas treatment system includes a platinum group metal capture material disclosed herein downstream of a catalyst composition including a platinum group metal, and the platinum group metal capture material and the catalyst composition are on different substrates.

[0019] Some embodiments of the present disclosure relate to a method of treating an exhaust gas comprising contacting the exhaust gas with a catalyst composition comprising a platinum group metal, and thereafter contacting the exhaust gas with at least one entity selected from a platinum group metal capture material disclosed herein, a catalytic article disclosed herein, and an exhaust gas treatment system disclosed herein.

[0020] Some embodiments of the present disclosure relate to a gas processing system comprising a means for oxidizing carbon monoxide and oxidizing hydrocarbons, a means for capturing volatilized platinum group metals, and a means for selectively reducing nitrogen oxides, wherein the means for oxidizing carbon monoxide and oxidizing hydrocarbons comprises a platinum group metal, the means for capturing volatilized platinum group metals comprises magnesium oxide, the means for capturing volatilized platinum group metals is free of transition metals, optionally except for zirconium, the means for capturing volatilized platinum group metals is free of rare earth metals, the means for capturing volatilized platinum group metals is located downstream of the means for oxidizing carbon monoxide and oxidizing hydrocarbons, and the means for capturing volatilized platinum group metals is located upstream of the means for selectively reducing nitrogen oxides.

[0021] In some embodiments, the means for capturing volatilized platinum group metals comprises a platinum group metal capture material as disclosed herein. [Brief description of the drawings]

[0022] To provide an understanding of embodiments of the present disclosure, reference is made to the accompanying drawings, which are illustrative and should not be construed as limiting the present disclosure. [Figure 1] FIG. 1 shows an experimental setup for studying the migration of platinum group metals. [Diagram 2] FIG. 13 illustrates SCR out NOx conversion of certain exemplary embodiments after platinum transfer. [Diagram 3] FIG. 13 illustrates SCR out N2O generation of some example embodiments after platinum transfer. [Figure 4] FIG. 13 shows Pt concentration (ppm) of some exemplary embodiments by combustion assay after platinum transfer. [Diagram 5] FIG. 13 illustrates SCR out NOx conversion of certain exemplary embodiments after 50 hours of platinum transfer aging. [Figure 6]FIG. 2 illustrates the distribution of platinum species in some example embodiments by X-ray photoelectron spectroscopy (XPS). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] 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.

[0024] As used herein, the term "material" refers to the elements, components and / or substances from which something is composed or can be made.

[0025] As used herein, the term "about" refers to a range of ±5% of the specified 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 assumed to be modified by "about."

[0026] As used herein, the term "platinum group metals," abbreviated as "PGM," refers to ruthenium (Ru), rhodium (Rh), palladium (Pd), osmium (Os), iridium (Ir), platinum (Pt), and combinations thereof.

[0027] As used herein, the term "noble metal" refers to ruthenium (Ru), rhodium (Rh), palladium (Pd), osmium (Os), iridium (Ir), platinum (Pt), gold (Au), silver (Ag), copper (Cu), rhenium (Re), mercury (Hg), and combinations thereof.

[0028] As used herein, the term "rare earth metal" refers to scandium (Sc), yttrium (Y), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), and combinations thereof.

[0029] As used herein, the term "diesel oxidation catalyst," abbreviated as "DOC," refers to a catalyst containing a platinum group metal capable of oxidizing carbon monoxide and hydrocarbons.

[0030] As used herein, the term "NO x " refers to nitrogen oxides and mixtures thereof. Exemplary nitrogen oxides include, but are not limited to, NO, N2O, NO2, and N2O2.

[0031] As used herein, the term "NO x The reducing component is NO x It refers to a component of a composition and / or article that can reduce NO. x Reducing components include, but are not limited to, selective catalytic reduction (SCR) catalysts, and lean NOx using, but not limited to, Pt, Pd, Rh, operating with alternating lean and rich pulses. x Includes LNT including capture (LNT).

[0032] As used herein, the term "selective catalytic reduction catalyst" (abbreviated as SCR 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 CO to N2 and water.

[0033] As used herein, "particle size D 90 " refers to a particle size where about 90% of the particles have a smaller particle size.

[0034] As used herein, the term "washcoat" refers to a coating applied to a substrate.

[0035] 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 and second entities.

[0036] As used herein, a first entity is "upstream" of a second entity if the second entity is downstream of the first entity.

[0037] Platinum group metal capture materials: In some embodiments, the platinum group metal capture material comprises an alkaline earth metal oxide.

[0038] In some embodiments, the platinum group metal capture material comprises less than about 0.01 wt. % of a platinum group metal, based on the total weight of the platinum group metal capture material. In some embodiments, the platinum group metal capture material comprises less than about 0.01 wt. % of a precious metal, based on the total weight of the platinum group metal capture material. In some embodiments, the platinum group metal capture material comprises less than about 0.01 wt. % of a rare earth metal, based on the total weight of the platinum group metal capture material. In some embodiments, the platinum group metal capture material comprises less than about 0.01 wt. % of a transition metal, optionally excluding zirconium, based on the total weight of the platinum group metal capture material. In some embodiments, the platinum group metal capture material comprises less than about 0.01 wt. % of ceria, gold, palladium, silver, platinum, and copper, based on the total weight of the platinum group metal capture material.

[0039] In some embodiments, the platinum group metal capture material is free of platinum group metals. In some embodiments, the platinum group metal capture material is free of precious metals. In some embodiments, the platinum group metal capture material is free of rare earth metals. In some embodiments, the platinum group metal capture material is free of transition metals, optionally except for zirconium. In some embodiments, the platinum group metal capture material is free of transition metals. In some embodiments, the platinum group metal capture material is free of ceria, gold, palladium, silver, platinum, and copper.

[0040] In some embodiments, the platinum group metal capture material does not include any platinum group metals. In some embodiments, the platinum group metal capture material does not include any precious metals. In some embodiments, the platinum group metal capture material does not include any rare earth metals.

[0041] In some embodiments, the alkaline earth metal oxide is selected from magnesium oxide, barium oxide, calcium oxide, strontium oxide, and combinations thereof. In some embodiments, the alkaline earth metal oxide comprises magnesium oxide. In some embodiments, the alkaline earth metal oxide comprises barium oxide. In some embodiments, the alkaline earth metal oxide comprises calcium oxide. In some embodiments, the alkaline earth metal oxide comprises strontium oxide.

[0042] In some embodiments, the platinum group metal capture material further comprises at least one metal oxide selected from alumina, zirconia, and combinations thereof. In some embodiments, the platinum group metal capture material further comprises alumina. In some embodiments, the platinum group metal capture material further comprises zirconia.

[0043] In some embodiments, the platinum group metal capture material has about 30% to about 100% magnesium oxide by weight, based on the total weight of the platinum group metal capture material. In some embodiments, the platinum group metal capture material has about 40% to about 100% magnesium oxide by weight, based on the total weight of the platinum group metal capture material. In some embodiments, the platinum group metal capture material has about 50% to about 100% magnesium oxide by weight, based on the total weight of the platinum group metal capture material. In some embodiments, the platinum group metal capture material has about 60% to about 100% magnesium oxide by weight, based on the total weight of the platinum group metal capture material. In some embodiments, the platinum group metal capture material has about 70% to about 100% magnesium oxide by weight, based on the total weight of the platinum group metal capture material. In some embodiments, the platinum group metal capture material has about 80% to about 100% magnesium oxide by weight, based on the total weight of the platinum group metal capture material. In some embodiments, the platinum group metal capture material has about 90% to about 100% magnesium oxide by weight, based on the total weight of the platinum group metal capture material. In some embodiments, the platinum group metal capture material has about 60% to about 95% magnesium oxide by weight, based on the total weight of the platinum group metal capture material. In some embodiments, the platinum group metal capture material has about 70% to about 95% magnesium oxide by weight, based on the total weight of the platinum group metal capture material. In some embodiments, the platinum group metal capture material has about 80% to about 95% magnesium oxide by weight, based on the total weight of the platinum group metal capture material. In some embodiments, the platinum group metal capture material has about 70% to about 90% magnesium oxide by weight, based on the total weight of the platinum group metal capture material. In some embodiments, the platinum group metal capture material has about 30% magnesium oxide by weight, based on the total weight of the platinum group metal capture material. In some embodiments, the platinum group metal capture material has about 40% magnesium oxide by weight, based on the total weight of the platinum group metal capture material. In some embodiments, the platinum group metal capture material has about 50% magnesium oxide by weight, based on the total weight of the platinum group metal capture material. In some embodiments, the platinum group metal capture material has about 60% magnesium oxide by weight, based on the total weight of the platinum group metal capture material. In some embodiments, the platinum group metal capture material has about 70% magnesium oxide by weight, based on the total weight of the platinum group metal capture material.In some embodiments, the platinum group metal capture material has about 80% magnesium oxide by weight, based on the total weight of the platinum group metal capture material. In some embodiments, the platinum group metal capture material has about 90% magnesium oxide by weight, based on the total weight of the platinum group metal capture material. In some embodiments, the platinum group metal capture material has about 95% magnesium oxide by weight, based on the total weight of the platinum group metal capture material. In some embodiments, the platinum group metal capture material has about 100% magnesium oxide by weight, based on the total weight of the platinum group metal capture material.

[0044] In some embodiments, the platinum group metal capture material consists essentially of aluminum magnesium oxide, zirconia magnesium oxide, aluminum calcium oxide, zirconia calcium oxide, or combinations thereof. In some embodiments, the platinum group metal capture material consists essentially of aluminum magnesium oxide, zirconia magnesium oxide, aluminum calcium oxide, or zirconia calcium oxide. In some embodiments, the platinum group metal capture material consists essentially of aluminum magnesium oxide. In some embodiments, the platinum group metal capture material consists essentially of zirconia magnesium oxide. In some embodiments, the platinum group metal capture material consists essentially of aluminum calcium oxide. In some embodiments, the platinum group metal capture material consists essentially of zirconia calcium oxide. In some embodiments, the platinum group metal capture material consists essentially of aluminum magnesium oxide and zirconia magnesium oxide. In some embodiments, the platinum group metal capture material consists essentially of aluminum magnesium oxide and aluminum calcium oxide. In some embodiments, the platinum group metal capture material consists essentially of aluminum magnesium oxide and zirconia calcium oxide. In some embodiments, the platinum group metal capture material consists essentially of aluminum magnesium oxide and zirconia calcium oxide. In some embodiments, the platinum group metal capture material consists essentially of aluminum magnesium oxide and zirconia calcium oxide. In some embodiments, the platinum group metal capture material consists essentially of zirconia magnesium oxide and aluminum calcium oxide. In some embodiments, the platinum group metal capture material consists essentially of zirconia magnesium oxide and zirconia calcium oxide, hi some embodiments, the platinum group metal capture material consists essentially of aluminum calcium oxide and zirconia calcium oxide.

[0045] In some embodiments, the platinum group metal capture material consists essentially of magnesium oxide.

[0046] In some embodiments, the following are non-limiting exemplary components that do not substantially affect the basic and novel properties of the platinum group metal capture material: binders (e.g., about 0.1% to about 10% by weight of a basic alumina binder, about 0.1% to about 10% by weight of a silica binder, about 0.1% to about 10% by weight of a zirconia binder, and combinations thereof). In some embodiments, the binder comprises about 0.1% to about 10% by weight of a colloidal ceria binder. In some embodiments, the binder does not comprise about 0.1% to about 10% by weight of a colloidal ceria binder. In some embodiments, the colloidal ceria binder is distinct from and separate from the active ceria capture material in the mixed oxide form. In some embodiments, the colloidal ceria binder is distinct from and separate from the active ceria capture material in the bulk high surface area form. In some embodiments, the platinum group metal capture material consists of magnesium oxide.

[0047] Catalyst article: In some embodiments, the catalytic article comprises a platinum group metal capture material disclosed herein downstream of a catalytic composition comprising a platinum group metal. x Upstream of the reducing component is a platinum group metal capture material as disclosed herein.

[0048] In some embodiments, the platinum group metal capture material has a metal content of at least about 0.1 g / in 3 In some embodiments, the platinum group metal capture material has a washcoat loading of about 0.1 g / in 3 ~about 2g / in 3 In some embodiments, the platinum group metal capture material has a washcoat loading in the range of about 0.1 g / in 3 ~Approx. 1g / in 3 In some embodiments, the platinum group metal capture material has a washcoat loading in the range of about 1 g / in 3 ~about 2g / in3 The washcoat loading ranges from 0.1 to 1.0.

[0049] In some embodiments, the platinum group metal capture material and the catalyst composition are in a layered arrangement. In some embodiments, the platinum group metal capture material and the catalyst composition are in a zoned arrangement.

[0050] In some embodiments, the platinum group metal capture material and NO x The reducing components are in a layered arrangement. In some embodiments, the platinum group metal capture material and the NO x The reducing components are in a zoned arrangement. In some embodiments, NO x The reducing component comprises a zeolite ion-exchanged with copper and / or iron. x The reducing component comprises a zeolite ion-exchanged with copper and iron. x The reducing component comprises a zeolite ion-exchanged with copper or iron. x The reducing component comprises a copper-exchanged zeolite. x The reducing component comprises a zeolite ion-exchanged with iron.

[0051] Base material: In some embodiments, one or more catalyst compositions and / or platinum group metal capture materials are disposed on one or more substrates, e.g., 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.

[0052] 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-α-alumina, aluminum titanate, silicon titanate, silicon carbide, silicon nitride, zircon-mullite, spodumene, alumina-silica-magnesia, zircon silicate, sillimanite, magnesium silicate, zircon, petalite, α-alumina, aluminosilicates, and the like.

[0053] 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 with openings or "punches out" in the channel walls. In some embodiments, the metal substrate may be used in various 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, in each case relative to the weight of the substrate, for example, 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 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 also having holes to enhance gas transport between the channels, allowing radial gas transport throughout the monolith.

[0054] In some embodiments, any suitable substrate may be employed, such as a monolith substrate of the type having fine parallel gas flow passages extending therethrough from an inlet or 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, e.g., each passage is blocked at one end of the substrate body and alternating passages are blocked at the opposing end face (a "wall-flow filter").

[0055] 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.

[0056] In some embodiments, the substrate is a flow-through substrate (e.g., a monolith substrate, including a flow-through honeycomb monolith 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 flow passages leading from the inlet to the outlet have walls on which 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 may be of any suitable cross-sectional shape and size, such as trapezoidal, rectangular, square, sinusoidal, hexagonal, elliptical, circular, etc. The flow-through substrate may be ceramic or metallic, as described above.

[0057] In some embodiments, the flow-through substrate is about 50 in 3 ~About 1200in 3 volume of about 60 cell density to about 500 cpsi, or up to about 900 cpsi per parallel inch, for example, a cell density (inlet opening) of about 200 to about 400 cpsi, and a wall thickness of about 50 microns to about 200 microns or about 400 microns.

[0058] In some embodiments, the substrate is a wall-flow filter having a plurality of micropaths 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 face. In some embodiments, the monolith 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 to about 600, e.g., about 100 to about 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.

[0059] In some embodiments, the wall flow filter article substrate can be, 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 1000in 3 ~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 microns to about 2000 microns, such as from about 50 microns to about 450 microns or from about 150 microns to about 400 microns.

[0060] In some embodiments, the walls of the wall-flow filter are porous and have a wall porosity of at least about 40% or at least about 50% with an average pore size of at least about 10 microns prior to the placement 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 microns, or about 20 microns to about 30 microns, or about 40 microns prior to the placement 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.

[0061] In some embodiments, the composition is mixed with water to form a slurry for 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 can vary; in some embodiments, all components are simply combined 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 can be adjusted to an acidic pH, for example, from about 3 to about 5.

[0062] In some embodiments, the slurry is milled. In some embodiments, milling is accomplished in a ball mill, continuous mill, or other similar equipment, and the solids content of the slurry may be, for example, about 20% to about 60% by weight, about 30% to about 40% by weight. In some embodiments, the post-milling slurry has a D of about 10 microns to about 50 microns (e.g., about 10 microns to about 20 microns). 90 It is characterized by its particle size.

[0063] Wash Coat: In some embodiments, the slurry is coated onto a substrate surface using washcoat techniques known in the art. A washcoat is a compositionally distinct layer of material disposed on the surface of a monolith substrate or an underlying washcoat layer, as described, for example, in Heck, Ronald and Robert Farrauto, Catalytic Air Pollution Control, New York: Wiley-Interscience, 2002, pp. 18-19. In some embodiments, a substrate contains one or more washcoat layers, and each washcoat layer can have a different composition.

[0064] In some embodiments, the substrate is dipped into or otherwise coated with the slurry one or more times. In some embodiments, the coated substrate is dried at elevated temperature (e.g., about 100° C. to about 150° C.) in still air or under an air stream or air jet for about 2 minutes to about 3 hours, and then calcined, for example, by heating at about 400° C. to about 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.

[0065] In some embodiments, after baking, 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 modified by altering the slurry rheology or solids content. In some embodiments, the coating / drying / baking process is repeated as necessary to build the coating to a desired loading level or thickness.

[0066] In some embodiments, the composition is applied as a single layer or in multiple layers. In some embodiments, a layer resulting from repeated washcoating of the same material to build up the loading level is a single layer. In some embodiments, the composition can be zone coated, meaning that a single substrate can be coated with different catalyst compositions in different regions along the gas effluent flow path.

[0067] Exhaust Gas Treatment System: In some embodiments, an exhaust gas treatment system includes an engine and a platinum group metal capture material as disclosed herein.In some embodiments, an exhaust gas treatment system includes an engine and a catalytic article as disclosed herein.

[0068] In some embodiments, an exhaust gas treatment system includes a platinum group metal capture material disclosed herein downstream of a catalyst composition comprising a platinum group metal, and the platinum group metal capture material and the catalyst composition are present on different substrate surfaces. In some embodiments, an exhaust gas treatment system includes a platinum group metal capture material disclosed herein downstream of a catalyst composition comprising a platinum group metal, and the platinum group metal capture material and the catalyst composition are present on the same substrate surface.

[0069] In some embodiments, an exhaust gas treatment system comprises a platinum group metal capture material disclosed herein upstream of a catalyst composition comprising a zeolite ion-exchanged with copper and / or iron, and the platinum group metal capture material and the catalyst composition are present on different substrate surfaces. In some embodiments, an exhaust gas treatment system comprises a platinum group metal capture material disclosed herein upstream of a catalyst composition comprising a zeolite ion-exchanged with copper and / or iron, and the platinum group metal capture material and the catalyst composition are present on the same substrate surface.

[0070] In some embodiments, an exhaust gas treatment system comprises means for oxidizing carbon monoxide and oxidizing hydrocarbons, means for trapping volatilized platinum group metals, and means for selectively reducing nitrogen oxides, wherein the means for oxidizing carbon monoxide and oxidizing hydrocarbons comprises a platinum group metal, the means for trapping volatilized platinum group metal comprises magnesium oxide, the means for trapping volatilized platinum group metal is free of transition metals, optionally except for zirconium, the means for trapping volatilized platinum group metal is free of rare earth metals, the means for trapping volatilized platinum group metal is downstream of the means for oxidizing carbon monoxide and oxidizing hydrocarbons, and the means for trapping volatilized platinum group metal is upstream of the means for selectively reducing nitrogen oxides.

[0071] In some embodiments, the means for capturing volatilized platinum group metals comprises a platinum group metal capture material as disclosed herein.

[0072] In some embodiments, the means for oxidizing carbon monoxide and oxidizing hydrocarbons is a diesel oxidation catalyst. In some embodiments, the means for selectively reducing nitrogen oxides comprises a zeolite ion-exchanged with copper and / or iron. In some embodiments, the means for selectively reducing nitrogen oxides is a selective catalytic reduction catalyst.

[0073] Methods for treating exhaust gases: In some embodiments, a method of treating an exhaust gas includes contacting the exhaust gas with a catalyst composition comprising a platinum group metal, and then contacting the exhaust gas with at least one entity selected from a platinum group metal capture material disclosed herein, a catalytic article disclosed herein, and an exhaust gas treatment system disclosed herein.

[0074] Diesel oxidation catalyst: Diesel oxidation catalysts provide an exemplary means for oxidizing carbon monoxide and oxidizing hydrocarbons. Non-limiting exemplary diesel oxidation catalysts include one or more platinum group metals. Non-limiting exemplary diesel oxidation catalysts are disclosed in International Application No. PCT / US2010 / 021048, filed January 14, 2010; International Application No. PCT / US2010 / 030226, filed April 7, 2010; International Application No. PCT / US2013 / 057011, filed August 28, 2013; International Application No. PCT / US2014 / 070356, filed December 15, 2014, and International Application No. PCT / EP2018 / 053568, filed February 13, 2018, the disclosures of each of which are incorporated herein by reference in their entirety.

[0075] NO x Reducing ingredients: NO selective catalytic reduction catalyst x The reducing component provides an exemplary means for selectively reducing nitrogen oxides. Non-limiting exemplary selective catalytic reduction catalysts include zeolites ion-exchanged with copper and / or iron. Non-limiting exemplary NO x Reducing components 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.

[0076] Non-limiting exemplary embodiments: Without limitation, some embodiments of the present disclosure include the following. 1. A platinum group metal capture material comprising an alkaline earth metal oxide. 2. A platinum-group metal capture material according to embodiment 1, wherein the platinum-group metal capture material comprises less than about 0.01 weight percent platinum-group metal, based on the total weight of the platinum-group metal capture material. 3. The platinum-group metal capture material according to embodiment 1 or 2, wherein the platinum-group metal capture material comprises less than about 0.01 weight percent precious metal, based on the total weight of the platinum-group metal capture material. 4. The platinum-group metal capture material according to any one of embodiments 1-3, wherein the platinum-group metal capture material comprises less than about 0.01 weight percent rare earth metal, based on the total weight of the platinum-group metal capture material. 5. The platinum-group metal capture material according to any one of embodiments 1-4, wherein the platinum-group metal capture material comprises less than about 0.01 wt. % of a transition metal, optionally excluding zirconium, based on the total weight of the platinum-group metal capture material. 6. The platinum-group metal capture material according to any one of embodiments 1-5, wherein the platinum-group metal capture material comprises less than about 0.01 weight percent of ceria, gold, palladium, silver, platinum, and copper, based on the total weight of the platinum-group metal capture material. 7. A platinum group metal capture material according to any one of embodiments 1 to 6, wherein the platinum group metal capture material does not contain platinum group metals. 8. The platinum group metal capture material according to any one of embodiments 1-7, wherein the platinum group metal capture material does not contain any platinum group metals. 9. The platinum group metal capture material according to any one of embodiments 1 to 8, wherein the platinum group metal capture material is free of precious metals. 10. A platinum-group metal capture material according to any one of claims 1 to 9, wherein the platinum-group metal capture material does not contain any precious metals. 11. The platinum group metal capture material according to any one of embodiments 1 to 10, wherein the platinum group metal capture material does not include a rare earth metal. 12. The platinum group metal capture material according to any one of embodiments 1 to 11, wherein the platinum group metal capture material does not include any rare earth metals. 13. A platinum group metal capture material according to any one of embodiments 1 to 12, wherein the platinum group metal capture material is optionally free of transition metals, except for zirconium. 14. A platinum-group metal capture material according to any one of embodiments 1-13, wherein the platinum-group capture material does not contain any transition metals, except, optionally, zirconium. 15. A platinum group metal capture material according to any one of embodiments 1 to 14, wherein the platinum group metal capture material does not include a transition metal. 16. A platinum-group metal capture material according to any one of embodiments 1-15, wherein the platinum-group capture material does not include any transition metals. 17. A platinum-group metal capture material according to any one of embodiments 1 to 16, wherein the platinum-group metal capture material does not include ceria, gold, palladium, silver, platinum, or copper. 18. The platinum-group metal capture material according to any one of embodiments 1 to 17, wherein the platinum-group metal capture material does not include ceria. 19. The platinum group metal capture material according to any one of embodiments 1 to 17, wherein the platinum group metal capture material does not include gold. 20. The platinum-group metal capture material according to any one of embodiments 1 to 17, wherein the platinum-group metal capture material does not include palladium. 21. The platinum-group metal capture material according to any one of embodiments 1 to 17, wherein the platinum-group metal capture material does not contain silver. 22. The platinum-group metal capture material according to any one of embodiments 1 to 17, wherein the platinum-group metal capture material does not contain platinum. 23. The platinum-group metal capture material according to any one of embodiments 1-17, wherein the platinum-group metal capture material does not contain copper. 24. The platinum-group metal capture material according to any one of embodiments 1 to 23, wherein the alkaline earth metal oxide is selected from magnesium oxide, barium oxide, calcium oxide, strontium oxide, and combinations thereof. 25. The platinum-group metal capture material according to any one of embodiments 1 to 24, wherein the alkaline earth metal oxide comprises magnesium oxide. 26. The platinum group metal capture material according to any one of embodiments 1 to 24, wherein the alkaline earth metal oxide comprises barium oxide. 27. The platinum group metal capture material according to any one of embodiments 1 to 24, wherein the alkaline earth metal oxide comprises calcium oxide. 28. The platinum-group metal capture material according to any one of embodiments 1 to 24, wherein the alkaline earth metal oxide comprises strontium oxide. 29. The platinum-group metal capture material according to any one of embodiments 1 to 28, further comprising at least one metal oxide selected from alumina, zirconia, and combinations thereof. 30. The platinum-group metal capture material according to any one of embodiments 1 to 29, further comprising alumina. 31. The platinum-group metal capture material according to any one of embodiments 1 to 29, further comprising zirconia. 32. The platinum-group metal capture material according to any one of embodiments 1-31, wherein the platinum-group metal capture material has about 30% to about 100% magnesium oxide by weight, based on the total weight of the platinum-group metal capture material. 33. The platinum-group metal capture material according to any one of embodiments 1-31, wherein the platinum-group metal capture material has about 50% to about 100% magnesium oxide by weight, based on the total weight of the platinum-group metal capture material. 34. The platinum-group metal capture material according to any one of embodiments 1-31, wherein the platinum-group metal capture material has about 60% to about 100% magnesium oxide by weight, based on the total weight of the platinum-group metal capture material. 35. The platinum-group metal capture material according to any one of embodiments 1-31, wherein the platinum-group metal capture material has about 70% to about 100% magnesium oxide by weight, based on the total weight of the platinum-group metal capture material. 36. The platinum-group metal capture material according to any one of embodiments 1-31, wherein the platinum-group metal capture material has about 80% to about 100% magnesium oxide by weight, based on the total weight of the platinum-group metal capture material. 37. The platinum-group metal capture material according to any one of embodiments 1-31, wherein the platinum-group metal capture material has about 90% to about 100% magnesium oxide by weight, based on the total weight of the platinum-group metal capture material. 38. The platinum-group metal capture material according to any one of embodiments 1-31, wherein the platinum-group metal capture material has about 60% to about 95% magnesium oxide by weight, based on the total weight of the platinum-group metal capture material. 39. The platinum-group metal capture material according to any one of embodiments 1-31, wherein the platinum-group metal capture material has about 70% to about 95% by weight magnesium oxide, based on the total weight of the platinum-group metal capture material. 40. The platinum-group metal capture material according to any one of embodiments 1 to 1315, wherein the platinum-group metal capture material has about 80% to about 95% by weight magnesium oxide, based on the total weight of the platinum-group metal capture material. 41. The platinum-group metal capture material according to any one of embodiments 1-31, wherein the platinum-group metal capture material has about 70% to about 90% magnesium oxide by weight, based on the total weight of the platinum-group metal capture material. 42. The platinum-group metal capture material according to any one of embodiments 1-31, wherein the platinum-group metal capture material consists essentially of magnesium oxide. 43. The platinum group metal capture material according to any one of embodiments 1 to 31, wherein the platinum group metal capture material consists of magnesium oxide. 44. The platinum-group metal capture material according to any one of embodiments 1 to 31, wherein the platinum-group metal capture material consists essentially of aluminum magnesium oxide, zirconia magnesium oxide, aluminum calcium oxide, or zirconia calcium oxide. 45. The platinum-group metal capture material according to any one of embodiments 1-31, wherein the platinum-group metal capture material consists essentially of aluminum magnesium oxide. 46. ​​The platinum-group metal capture material according to any one of embodiments 1-31, wherein the platinum-group metal capture material consists essentially of zirconia magnesium oxide. 47. The platinum-group metal capture material according to any one of embodiments 1-31, wherein the platinum-group metal capture material consists essentially of aluminum calcium oxide. 48. The platinum-group metal capture material according to any one of embodiments 1-31, wherein the platinum-group metal capture material consists essentially of zirconia calcium oxide. 49. A catalytic article comprising a platinum group metal capture material according to any one of embodiments 1 to 48 downstream of a catalytic composition comprising a platinum group metal. 50. The platinum group metal capture material has a mass of at least about 0.1 g / in 3 50. A catalyst article according to embodiment 49, having a washcoat loading of 51. The platinum group metal capture material is about 0.1 g / in 3 ~about 2g / in 3 50. A catalyst article according to embodiment 49, having a washcoat loading in the range of 52. The platinum group metal capture material is about 0.1 g / in 3 ~Approx. 1g / in 350. A catalyst article according to embodiment 49, having a washcoat loading in the range of 53. The platinum group metal capture material is approximately 1 g / in 3 ~about 2g / in 3 50. A catalyst article according to embodiment 49, having a washcoat loading in the range of 54. The catalytic article according to any one of embodiments 43 to 53, wherein the platinum group metal capture material and the catalytic composition are in a layered arrangement. 55. The catalytic article according to any one of embodiments 43-53, wherein the platinum group metal capture material and the catalytic composition are in a zoned arrangement. 56. NO x A catalytic article comprising a platinum group metal capture material according to any one of embodiments 1 to 48 upstream of the reducing component. 57. The platinum group metal capture material has a mass of at least about 0.1 g / in 3 57. A catalyst article according to embodiment 56, having a washcoat loading of 58. The platinum group metal capture material is about 0.1 g / in 3 ~about 2g / in 3 57. A catalyst article according to embodiment 56, having a washcoat loading in the range of 59. The platinum group metal capture material is about 0.1 g / in 3 ~Approx. 1g / in 3 57. A catalyst article according to embodiment 56, having a washcoat loading in the range of 60. The platinum group metal capture material is approximately 1 g / in 3 ~about 2g / in 3 57. A catalyst article according to embodiment 56, having a washcoat loading in the range of 61. Platinum group metal capture materials and NO x 61. The catalytic article according to any one of embodiments 56 to 60, wherein the reducing component is in a layered arrangement. 62. Platinum group metal capture materials and NO x 61. The catalytic article according to any one of embodiments 56-60, wherein the reducing component is in a zoned arrangement. 63. NO x 63. The catalytic article according to any one of embodiments 56 to 62, wherein the reducing component comprises a zeolite ion-exchanged with copper and / or iron. 64. NO x 63. The catalytic article according to any one of embodiments 56 to 62, wherein the reducing component comprises a zeolite ion-exchanged with copper. 65. NO x 63. The catalytic article according to any one of embodiments 56 to 62, wherein the reducing component comprises a zeolite ion-exchanged with iron. 66. An exhaust gas treatment system comprising an engine and a platinum group metal capture material according to any one of embodiments 1-48. 67. An exhaust gas treatment system comprising an engine and a catalytic article according to any one of embodiments 49 to 63. 68. An exhaust gas treatment system comprising a platinum group metal capture material according to any one of embodiments 1-48 downstream of a catalyst composition comprising a platinum group metal, wherein the platinum group metal capture material and the catalyst composition are present on different substrate surfaces. 69. An exhaust gas treatment system comprising a platinum group metal capture material according to any one of embodiments 1-48 downstream of a catalyst composition comprising a platinum group metal, wherein the platinum group metal capture material and the catalyst composition are present on the same substrate surface. 70. A method for treating an exhaust gas, comprising contacting the exhaust gas with a catalyst composition comprising a platinum group metal, and subsequently contacting the exhaust gas with at least one entity selected from a platinum group metal capture material according to any one of embodiments 1-48, a catalyst article according to any one of embodiments 49-66, and an exhaust gas treatment system according to any one of embodiments 67-69. 71. An exhaust gas treatment system comprising: means for oxidizing carbon monoxide and oxidizing hydrocarbons; means for capturing volatilized platinum group metals; and means for selectively reducing nitrogen oxides, wherein the means for oxidizing carbon monoxide and oxidizing hydrocarbons comprises a platinum group metal; the means for capturing volatilized platinum group metals comprises magnesium oxide; the means for capturing volatilized platinum group metals is free of transition metals, optionally except for zirconium; the means for capturing volatilized platinum group metals is free of rare earth metals; the means for capturing volatilized platinum group metals is located downstream of the means for oxidizing carbon monoxide and oxidizing hydrocarbons; and the means for capturing volatilized platinum group metals is located upstream of the means for selectively reducing nitrogen oxides. 72. The exhaust gas treatment system according to embodiment 71, wherein the means for capturing volatilized platinum group metals comprises a platinum group metal capture material according to any one of embodiments 1-48. 73. The exhaust gas treatment system according to embodiment 71 or 72, wherein the means for oxidizing carbon monoxide and for oxidizing hydrocarbons is a diesel oxidation catalyst. 74. An exhaust gas treatment system according to any one of embodiments 71-73, wherein the means for selectively reducing nitrogen oxides comprises a zeolite ion-exchanged with copper and / or iron. 75. The exhaust gas treatment system according to any one of embodiments 71-74, wherein the means for selectively reducing nitrogen oxides is a selective catalytic reduction catalyst. EXAMPLES

[0077] The following examples are intended to be illustrative and are not meant to limit the scope of the disclosure in any way.

[0078] Control Example (No Platinum Group Metal Capture Material) Example 1 (Al2O3 capture material): The gamma-Al2O3 material and 4% HOAc were added to deionized (DI) water to form a slurry suspension with a solids content of about 45%. 90The slurry was milled until the particle size reached 12-15 micrometers. Additional HOAc was added to adjust the pH to 4-4.5. The slurry was then coated onto a 400 / 4 honeycomb substrate at 38% solids. After drying, the catalyst was calcined in air at 500 °C for 1 h. The Al2O3 washcoat loading was 1.2 g / in 3 It was.

[0079] Example 2 (Pd / Al2O3 capture material): The monolith sample from Example 1 was coated with an additional Pd / Al2O3 topcoat. The gamma-Al2O3 material from Example 1 was impregnated with a dilute Pd(NO3)2 solution. The Pd frit was added to DI water to form a slurry suspension with a solids content of about 40%. Final particle size D 90 The slurry was milled to a particle size of 12-15 micrometers and to this was added 5 wt% dispersed alumina binder. The slurry was then coated on the surface of Example 1 with a solid content of 36%. After drying, the catalyst was calcined in air at 500°C for 1 hour. The Pd loading was 2 g / ft 3 The amount of Al2O3 supported is 0.25 g / in 3 It was.

[0080] Example 3 (MgO capture material): Mg(OH)2 powder was added to DI water to form a slurry, to which up to 10 wt% ammonium polyacrylate dispersant was added. 90 The slurry was mixed under high shear until the particle size was <10-12 micrometers. About 5 wt.% basic alumina binder was added to the slurry, resulting in a pH of about 9.5. The slurry was then coated onto a 400 / 4 honeycomb substrate at 30% solids content. After drying, the catalyst was calcined in air at 550 °C for 1 hour. The MgO loading was 1.8 g / in 3 It was.

[0081] Example 4 (70% MgO-Al2O3 capture material): The 70% MgO-30% Al2O3 composite was added to DI water to form a slurry, to which up to 10 wt% ammonium polyacrylate dispersant was added. The slurry was milled until the D90 reached <10-12 micrometers. About 5 wt% basic alumina binder was added to the slurry, resulting in a pH of about 9.2. The slurry was then coated onto a 400 / 4 honeycomb substrate at 23% solids content. After drying, the catalyst was calcined in air at 550 °C for 1 hour. The MgO-Al2O3 loading was 1.1 g / in 3 It was.

[0082] Example 5: Pt transfer studies: To evaluate the efficiency of various Pt capture materials, a Pt migration aging system was established. As shown in Figure 1, a 1 x 1 x 4 inch DOC core sample drilled from a commercial full-sized DOC (10.5 x 10.5 x 4 inch) sample was placed in the first position to serve as the Pt migration source. The DOC was 45 g / ft2 with a Pt / Pd ratio of 1 / 2. 3 A forward zone (40% length) with PGM loading and 15 g / ft of Pt / Pd ratio of 5 / 1 3 It consisted of a rear zone (60% length) with PGM loading. The downstream SCR catalyst (1×1×1.5 in) was also taken from a commercial full size Fe / CHA catalyst. A Pt trap core (1×1×1.5 in) was placed at the DOC outlet without any gap in between. Pt migration aging was carried out in 10% steam air at T650°C at the DOC inlet for 15 hours. The space velocity over the DOC was 35,000 / hr. The temperature at the SCR inlet was about 540-560°C. Figure 1 illustrates the experimental setup for the Pt migration study.

[0083] Example 6: SCR Catalyst Testing Procedure: After each Pt migration aging test, the SCR cores were evaluated using a steady-state protocol at 350° C., 400° C., and 450° C. The feed composition consisted of 500 ppm NH3, 500 ppm NO, 7% H2O, 10% O2 in N2 at equilibrium. The space velocity was 80,000 / hr.

[0084] X-ray photoelectron spectroscopy (XPS): A monochromated Al Kα source (1486 eV) was used to excite core level electrons. Samples are attached to conductive carbon double-sided tape. Charge is neutralized using an Ar flood gun. Binding energies are calibrated using adventitious carbon at 284.8 eV. Elemental quantification is obtained using survey spectra and speciation is obtained from high-resolution fine-scan fields. Speciation is used to partition elemental quantification so that accurate quantification of each species with respect to the corresponding element is obtained. Peaks are fitted using Gauss-Lorentzian functions and their areas are extracted and corrected by instrument-specific relative sensitivity factors (RSFs) to calculate semi-quantitative surface composition.

[0085] The distribution of Pt species detected by XPS was determined for the 1% Pt / Al2O3, 1% Pt / ZrO2, and 1% Pt / MgO samples. These samples were prepared as follows.

[0086] XPS sample 1 (1% Pt / Al2O3) was prepared by incipient wetness impregnation of an alumina support with a Pt ammine complex solution, followed by drying at 110 °C for 4 h and calcination in air at 500 °C for 1 h.

[0087] XPS sample 2 (1% Pt / ZrO2) was prepared by incipient wetness impregnation of a zirconia support with a Pt ammine complex solution, followed by drying at 110 °C for 4 h and calcination in air at 500 °C for 1 h.

[0088] XPS sample 3 (1% Pt / MgO) was prepared by incipient wetness impregnation of an MgO support with a Pt ammine complex solution, followed by drying at 110° C. for 4 h and calcination in air at 500° C. for 1 h.

[0089] Figure 2 shows the NO flux of SCR catalysts after Pt transfer aging with various platinum group metal capture materials. xConversion activity is compared. The control example is an SCR catalyst aged without the presence of any of Examples 1-4. Examples 1-4 all demonstrate excellent efficiency in protecting the downstream SCR catalyst from Pt volatilization from the front DOC, i.e., little deactivation was observed between 350-450°C.

[0090] 3 compares N2O emissions from Pt transfer aged SCR catalysts containing various platinum group metal capture materials. The control examples are SCR catalysts aged without the presence of any of Examples 1-4 and show high levels of N2O emissions. Examples 1-4 show significantly lower N2O levels, either similar to or slightly lower than the levels of fresh SCR catalysts.

[0091] After completing the SCR test, both the platinum group metal capture material and the downstream SCR core were crushed and the Pt concentration was measured by combustion assay. Figure 4 compares the Pt concentration on the aged core surface. Examples 3 and 4 captured significantly more Pt than Examples 1 and 2, and very little Pt was found on the downstream SCR core surface of Examples 3 and 4. Therefore, Examples 3 and 4 appear to be more efficient at retaining volatile Pt species than Examples 1 and 2, which may be due to the strong affinity of Pt to the MgO surface. Indeed, when Example 3 was subjected to 50 hours of extended aging, the amount of Pt found on the downstream SCR catalyst surface remained at the combustion assay detection limit (0.1 ppm), while 8.65 ppm of Pt was found for Example 3. When Example 1 was subjected to 50 hours of extended aging, only 3.61 ppm of Pt was found, while 2.78 ppm of Pt was found on the SCR surface, suggesting that Example 1, which has a combination of Pd and Al2O3 as the PGM capture material, does not retain volatilized Pt as effectively as Example 3, which has only MgO as the PGM capture trap material.

[0092] Figure 5 shows the NO2 emission of the SCR catalyst after 50 hours of Pt transfer aging. xComparing the conversion activities, when Example 1 was used after DOC to capture the volatilized Pt, severe SCR deactivation at >350°C was observed, whereas when Example 3 was used, the SCR activity remained unchanged.

[0093] FIG. 6 shows the distribution of Pt species detected by XPS on the surface of several exemplary platinum group metal capture materials after 800° C. / 12 h hydrothermal (HT) aging. On typical alumina or silica support surfaces, platinum oxide completely decomposes to platinum metal at >600° C., resulting in severe particle sintering at elevated temperatures. Thus, platinum was found to exist only in the Pt(0) oxidation state on the Al2O3 surface. In contrast, platinum was found in both Pt(0) and Pt(2+) oxidation states on the ZrO2 surface, and platinum was found in both Pt(0) and Pt(4+) oxidation states on the MgO surface. The presence of Pt(2+) and Pt(4+) is an indication of strong metal-support interactions between platinum and the support, which may stabilize platinum oxide from becoming volatile and decomposing to platinum metal.

[0094] Without wishing to be bound by theory, it is believed that the strength of the interaction between Pt and the platinum group metal capture material increases with increasing oxidation state of the captured Pt species. For example, MgO is believed to have a stronger interaction strength than ZrO2, which is believed to have a stronger interaction strength than Al2O3, and thus platinum capture rates increase in the order MgO>ZrO2>Al2O3. Without wishing to be bound by theory, it is believed that the ability of some platinum group metal capture materials to bind to platinum group metals in higher oxidation states is an exemplary reason for the surprisingly high performance of the platinum group metal capture materials disclosed herein, such as MgO.

[0095] A claim or description including "or" or "and / or" between at least one member of a group is deemed to be satisfied when one, more than one, or all of the members of the group are present in, employed in, or otherwise relevant to a given product or process, unless otherwise stated or apparent from the context. The present disclosure includes embodiments in which exactly one member of a group is present in, employed 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, employed in, or otherwise relevant to a given product or process.

[0096] 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 amended to include at least one limitation found in any other claim that is dependent on the same base 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 an embodiment of the disclosure or aspects of the disclosure consists of or consists essentially of such elements and / or features. For the sake of brevity, such embodiments have not been specifically described in this language herein. When ranges are given, endpoints are included. Moreover, unless otherwise indicated or apparent from the context and the understanding of one of ordinary skill in the art, values ​​expressed as ranges can assume in different embodiments of the disclosure any specific value or subrange within the stated range unless the context clearly dictates otherwise.

[0097] 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 platinum group metal capture material comprising alkaline earth metal oxides, the platinum group metal capture material comprising less than 0.01 weight percent ceria, gold, palladium, silver, platinum, and copper, based on the total weight of the platinum group metal capture material.

2. 2. The platinum group metal capture material of claim 1, wherein the alkaline earth metal oxide is selected from magnesium oxide, barium oxide, calcium oxide, strontium oxide, and combinations thereof.

3. 3. The platinum group metal capture material of claim 1 or 2, further comprising at least one metal oxide selected from alumina, zirconia, and combinations thereof.

4. 3. The platinum group metal capture material of claim 2, wherein the platinum group metal capture material has from about 30% to about 90% by weight of magnesium oxide, based on the total weight of the platinum group metal capture material.

5. 3. The platinum group metal capture material of claim 1, wherein the platinum group metal capture material consists essentially of magnesium oxide.

6. 3. The platinum group metal capture material according to claim 1, wherein the platinum group metal capture material consists essentially of aluminum magnesium oxide, zirconia magnesium oxide, aluminum calcium oxide, or zirconia calcium oxide.

7. A catalytic article comprising the platinum group metal capture material of claim 1 downstream of a catalyst composition comprising a platinum group metal.

8. the platinum group metal capture material is at least 0.2 g / in ３ 8. The catalyst article of claim 7 having a washcoat loading of

9. The catalytic article of claim 7 , wherein the platinum group metal capture material and the catalytic composition are in a layered and / or zoned arrangement.

10. An exhaust gas treatment system comprising an engine and the catalytic article of claim 7.

11. 10. An exhaust gas treatment system comprising the platinum group metal capture material of claim 1 downstream of a catalyst composition comprising a platinum group metal, wherein the platinum group metal capture material and the catalyst composition are on different substrate surfaces.

12. 1. A method for treating exhaust gases, comprising: contacting the exhaust gas with a catalyst composition comprising a platinum group metal; subsequently contacting the exhaust gas with at least one entity selected from the platinum group metal capture material of claim 1, the catalytic article of claim 7, and the exhaust gas treatment system of claim 10 or 11; A method comprising:

13. means for oxidizing carbon monoxide and for oxidizing hydrocarbons; means for capturing volatilized platinum group metal; and means for selectively reducing nitrogen oxides, comprising: said means for oxidizing carbon monoxide and for oxidizing hydrocarbons comprises a platinum group metal; said means for capturing volatilized platinum group metals comprises magnesium oxide; said means for capturing volatilized platinum group metals is optionally free of transition metals, except for zirconium; said means for capturing volatilized platinum group metals does not contain rare earth metals; said means for capturing volatilized platinum group metals is located downstream of said means for oxidizing carbon monoxide and hydrocarbons; said means for capturing volatilized platinum group metals is located upstream of said means for selectively reducing nitrogen oxides; Exhaust gas treatment system.

14. 14. The exhaust gas treatment system of claim 13, wherein said means for trapping volatilized platinum group metals comprises the platinum group metal trap material of claim 1 or 2.

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