Three-way conversion catalyst, preparation method thereof, emission treatment method and system using the catalyst

Abstract

A catalyst article includes a substrate, an oxygen storage component, a refractory metal oxide support, a platinum group metal (PGM) component, and a PGM modifier. The refractory metal oxide support includes a ceria-alumina composite. The ceria-alumina composite includes a first ceria component mixed with alumina. The PGM modifier includes a second ceria component adjacent to the PGM component.

Description

240023WO01 / ECM-24-1158WOTHREE-WAY CONVERSION CATALYST, PREPARATION METHOD THEREOF, EMISSION TREATMENT METHOD AND SYSTEM USING THE CATALYSTTECHNICAL FIELD

[0001] The present disclosure is directed to the field of exhaust treatment of internal combustion engines. More particularly, the present disclosure pertains to a three-way conversion (TWC) catalyst, a method for preparing the TWC catalyst, and an emission system and emission treatment method using the TWC catalyst.BACKGROUND

[0002] Three-way conversion (TWC) catalysts have been utilized in the emission treatment for an exhaust stream from internal combustion engines. Generally, the exhaust stream contains pollutants such as hydrocarbons (HCs), oxides of nitrogen (NOX), and carbon monoxide (CO). The TWC catalysts are used in the exhaust gas line of an internal combustion engine to oxidize unbum hydrocarbons and carbon monoxide and reduce nitrogen oxides. TWC catalysts generally contain a costly platinum group metal (PGM) component as the active catalytic component. The PGM component in TWC catalysts is usually supported on a refectory metal oxide support.

[0003] US EPA has recently released Tier 4 regulations for light-duty vehicles, which target achieving tailpipe non-methane hydrocarbons (NMHC) and nitrates NOX(NMHC+NOX) emissions less than 15 mg / mile by 2032. This regulatory move demands a 50% reduction of NMHC+NOXemissions with respect to the current, already quite tight Tier 3 regulations for super ultra-low emissions vehicles (SULEV, NMHC+NOX< 30 mg / mile).

[0004] Driven by market demands and regulation requirements, it is necessary to further promote efficiencies of TWC catalysts. For example, the activity of the PGM component in TWC catalysts needs to be improved so that a less amount of the PGM component in TWC catalysts can achieve a higher emission control activity.SUMMARY

[0005] The present disclosure generally provides a catalyst article for treating an exhaust stream, a method for preparing such catalyst article, and an emission treatment system utilizing such catalyst article.

[0006] One aspect of the present disclosure provides a catalyst article. The catalyst article includes a substrate, an oxygen storage component, a refractory metal oxide support, a 11626869359.1240023WO01 / ECM-24-1158WOplatinum group metal (PGM) component, and a PGM modifier. The refractory metal oxide support includes a ceria-alumina composite. The ceria-alumina composite includes a first ceria component mixed with alumina. The PGM modifier includes a second ceria component adjacent to the PGM component.

[0007] In some embodiments, the PGM component includes one or more of palladium, rhodium, platinum, or a combination of thereof.

[0008] In some embodiments, the first ceria component is ceria of nanoscale crystallites randomly mixed with alumina in the refractory metal oxide support.

[0009] In some embodiments, a content of the first ceria component in the refractory metal oxide support ranges from 5% to 40% by weight with respect to a total weight of the refractory metal oxide support.

[0010] In some embodiments, a content of the second ceria component is 1-20 wt. % with respect to a total weight of the refractory metal oxide support.

[0011] In some embodiments, the content of the second ceria component is 5-15 wt. % with respect to a total weight of the refractory metal oxide support.

[0012] In some embodiments, the catalyst article further comprises an additive deposited on the refractory metal oxide support.

[0013] In some embodiments, the additive is an oxide or a salt of Y, La, Pr, Nd, Sm, Gd, or a combination thereof.

[0014] In some embodiments, the catalyst has a signal layered structure, a multi-layered structure, or a zoned structure.

[0015] In some embodiments, the substrate includes a wall flow filter or a flow through monolith substrate.

[0016] Another aspect of the present disclosure provides a method for preparing a catalyst article. The method includes providing a substrate and coating a catalytic material onto the substrate. The catalytic material includes an oxygen storage component, a refractory metal oxide support, a PGM component, and a PGM modifier. The refractory metal oxide support comprises a ceria-alumina composite comprising a first ceria component mixed with alumina. The PGM modifier comprise a second ceria component adjacent to the PGM component.

[0017] In some embodiments, the PGM component includes one or more of palladium, rhodium, platinum, or a combination of thereof.

[0018] In some embodiments, the first ceria component is ceria of nanoscale crystallites randomly mixed with alumina in the refractory metal oxide support.21626869359.1240023WO01 / ECM-24-1158WO

[0019] In some embodiments, a content of the first ceria component in the refractory metal oxide support ranges from 5% to 40% by weight with respect to a total weight of the refractory metal oxide support.

[0020] In some embodiments, the method further includes depositing the PGM modifier and the PGM component on the refractory metal oxide support through a co-impregnation method or a sequential impregnation method.

[0021] In some embodiments, depositing the PGM modifier includes depositing the PGM modifier using a soluble cerium salt precursor or a colloidal solution of ceria nanoparticles.

[0022] In some embodiments, a content of the second ceria component is 1-20 wt. % with respect to a total weight of the refractory metal oxide support.

[0023] In some embodiments, the content of the second ceria component is 5-15 wt. % with respect to a total weight of the refractory metal oxide support.

[0024] In some embodiments, the method further includes depositing an additive on the refractory metal oxide support through a wet impregnation method.

[0025] In some embodiments, the additive is an oxide or a salt of Y, La, Pr, Nd, Sm, Gd, or a combination thereof.

[0026] Another aspect of the present disclosure provides an emission treatment system for treatment of an exhaust stream of an internal combustion engine, the emission treatment system comprising an exhaust conduit in fluid communication with the internal combustion engine via an exhaust manifold, and a catalyst article disposed in the exhaust conduit and being configured to treat the exhaust stream, the catalyst article comprising a substrate, an oxygen storage component, a refractory metal oxide support, a PGM component, and a PGM modifier. The refractory metal oxide support comprises a ceria-alumina composite comprising a first ceria component mixed with alumina. The PGM modifier comprise a second ceria component adjacent to the PGM component.BRIEF DESCRIPTION OF DRAWINGS

[0027] The features of the present disclosure and various advantages thereof will become apparent in consideration of the following detailed description of the embodiments in conjunction with the accompany drawings. Below is a brief description of the accompanying drawings.

[0028] FIG. 1 schematically shows a three-way conversion catalyst composite in accordance with some embodiments of the present disclosure.31626869359.1240023WO01 / ECM-24-1158WO

[0029] FIG. 2 schematically shows a catalyst article in accordance with some embodiments of the present disclosure.

[0030] FIG. 3 schematically shows an enlarged partial cross-sectional view of the catalyst article in FIG. 2.

[0031] FIG. 4 schematically shows a perspective view of a wall flow filter substrate in accordance with some embodiments of the present disclosure.

[0032] FIG. 5 schematically shows an enlarged cutaway view of a section of the wall flow filter substrate in FIG. 4.

[0033] FIGs. 6A-6J schematically show examples of catalyst articles in accordance with some embodiments of the present disclosure.

[0034] FIGs. 7A-7D schematically show examples of emission treatment systems in accordance with some embodiments of the present disclosure.

[0035] FIG. 8 is a flowchart showing a method for preparing a catalyst article in accordance with an embodiment.

[0036] FIG. 9 is a graphical representation of TWC activity evaluation results of catalyst composite examples in accordance with some embodiments of the present disclosure.

[0037] FIGs. 10A-10C is a graphical representation of X-ray Diffraction (XRD) profiles of catalyst composite examples in accordance with some embodiments of the present disclosure.

[0038] FIG. 11 shows Scanning Transmission Electron Microscopy (STEM) mapping of a catalyst composite example in accordance with some embodiments of the present disclosure.

[0039] FIG. 12 shows Scanning Transmission Electron Microscopy (STEM) mapping of another catalyst composite example in accordance with some embodiments of the present disclosure.DETAILED DESCRIPTION OF EMBODIMENTS

[0040] The embodiments described below are for illustrative purpose regarding the principles and applications of the present disclosure but are not intended to limit the present disclosure to the details of any particular embodiments. Based on the description of the present disclosure, those skilled in the art should be able to obtain various modifications and variations of the method and apparatus of the present disclosure without departing from the spirit and scope of the present disclosure. Therefore, these modifications and variations are within the scope of the appended claims and their equivalents.

[0041] Unless defined otherwise, all technical and scientific terms used herein have the same meanings as commonly understood by one of ordinary skill in the art. Reference throughout 41626869359.1240023WO01 / ECM-24-1158WOthis specification to “one embodiment,” “some embodiments,” “one or more embodiments” or “an embodiment” means that one or more particular features, structures, elements, materials, or characteristics described in connection with the referenced embodiment(s) is included in one or more embodiments of the present disclosure. Articles “a,” “an,” and “the” are used herein to refer to one or to more than one (i.e., to at least one) of the grammatical object of the article and include plural references unless the context clearly dictates otherwise. As used in this document, the term “comprising” and “including” do not intend to indicate exclusive inclusion. The term “about” used throughout this specification is used to describe and account for small fluctuations. The phrase “at least one” include one or more than one of the objects associated with such phrase. The phrase “A or B” means “A,” “B,” or “A and B.” The phrase “at least one of... or...” refers to all possible combinations of the grammatical objects of this phrase. For example, “at least A, B, or C” refers to A alone, B alone, C alone, A and B together, A and C together, B and C together, or A, B, and C all together.

[0042] The term “catalyst” refers to a material that promotes a chemical reaction. A catalyst composite includes active species that have catalytic activity and a “support” that carries or supports such active species. Active species can refer to precious metals, stabilizers, promoters, or modifiers. The term “support” refers to any high surface area material, usually a metal oxide material, or a mixed metal oxide material or composite upon which a catalytic precious metal is applied. In some embodiments, the support includes a refractory metal oxide support. The support can receive the active species via a suitable method, e.g., impregnation, precipitation, association, dispersion, deposition, etc.

[0043] The term “catalyst article” refers to a component that is used to promote a desired reaction. In some embodiments of the present disclosure, the catalyst article includes a “substrate” having at least one washcoat disposed thereon, where the washcoat is made by at least a catalytic material. As used herein, the term “washcoat” has its usual meaning in the art of a thin adherent coating of a catalytic composite and other materials such as binders applied onto a substrate.

[0044] As used herein, the term “stream” broadly refers to any flowing gas or aerosol mixture that may contain solid or liquid particulate matter. The term “exhaust stream” means a stream of gaseous constituents, such as the exhaust of a combustion engine, which may contain entrained non-gaseous components such as liquid droplets, solid particulates, and the like. The exhaust stream of a combustion engine typically further includes combustion products (CO2and H2O), products of incomplete combustion (carbon monoxide (CO) and 51626869359.1240023WO01 / ECM-24-1158WOhydrocarbons (HC)), oxides of nitrogen (NOX), combustible and / or carbonaceous particulate matter (soot), and un-reacted oxygen and nitrogen. In some embodiments, the temperature of the exhaust stream is from ambient temperature to about 700 °C. For example, the exhaust stream has a temperature of about 10 °C to about 650 °C, about 100 °C to about 600 °C, or about 200 °C to 500 °C, or about 300 °C to 400 °C. In some embodiments, the water percentage in the exhaust stream is about 10 % to about 25 %.

[0045] The term “in fluid communication” is used to refer to articles positioned on the same exhaust line, i.e., a common exhaust stream passes through articles that are in fluid communication with each other. Articles in fluid communication may be adjacent to each other in the exhaust line. Alternatively, articles in fluid communication may be separated by one or more articles.

[0046] The terms “upstream” and “downstream” refer to relative directions according to the flow of an engine exhaust stream from an engine towards a tailpipe, with the engine in an upstream location and the tailpipe and any pollution abatement articles such as filters and catalysts being downstream from the engine.

[0047] “Platinum group metal” or “PGM” refers to platinum group metals or oxides thereof, including platinum (Pt), palladium (Pd), ruthenium (Ru), rhodium (Rh), osmium (Os), iridium (Ir), and combinations thereof. In some embodiments, the PGM component is Pd, Rh, Pt, or combinations thereof. In some embodiments, the PGM component is a combination of Pd and Rh. The PGM component comprises oxides, metallic particles, or alloys of PGM elements. The PGM component is supported on the support material. For example, the PGM component is supported on a refractory metal oxide support.

[0048] “Refractory metal oxide support” refers to a metal-containing oxide support exhibiting chemical and physical stability at high temperatures, such as the temperatures associated with gasoline and diesel engine exhaust. Exemplary refractory metal oxides include alumina, silica, zirconia, titania, ceria, and physical mixtures or chemical combinations thereof, including atomically-doped combinations. In some embodiments, the refractory metal oxide material includes, in addition to the aforementioned oxides, a metal oxide(s) of alkali, semimetal, and / or transition metal, e.g., La, Y, Mg, Ba, Sr, Zr, Ti, Si, Ce, Mn, Nd, Pr, Sm, Nb, W, Mo, Fe, or combinations thereof. In some embodiments, the amount of such metal oxide(s) in the refractory metal oxide material can range from about 0.5% to about 70% by weight based on the total weight of the refractory metal oxide material.Exemplary combinations of metal oxides include alumina-zirconia, ceria-zirconia, alumina-61626869359.1240023WO01 / ECM-24-1158WOceria-zirconia, lanthana-alumina, lanthana-zirconia, lanthana-zirconia-alumina, baria-alumina, baria-lanthana-alumina, baria-lanthana-neodymia alumina, and ceria-alumina.

[0049] In some embodiments, the refractory metal oxide support includes a ceria-alumina. In some embodiments, the content of ceria in the ceria-alumina can range from about 5 wt. % to about 40 wt. %, from about 10 wt. % to about 30 wt. %, from about 15 wt. % to about 25 wt. %, with respect to a total weight of the ceria-alumina.

[0050] In describing a quantity or a loading of a washcoat or catalytic metal components or other components of the composition, it is convenient to use units of weight of component per unit volume of catalyst substrate. Therefore, the units, grams per cubic inch (“g / in3”) and grams per cubic foot (“g / ft3”) are used herein to mean the weight of a component per volume of the substrate, including the volume of void spaces of the substrate. Other units of weight per volume such as grams per liter (“g / L”) are also sometimes used.

[0051] It is noted that these weights per unit volume of substrate are typically calculated by weighing the catalyst substrate before and after treatment with the corresponding catalyst washcoat composition, and since the treatment process involves drying and calcining the catalyst substrate at high temperature, these weights represent an essentially solvent-free catalyst coating as essentially all of the evaporable of the washcoat has been removed.

[0052] FIG. 1 schematically shows a three-way conversion catalyst composite in accordance with some embodiments of the present disclosure. The catalyst composite includes a refractory metal oxide support 110, a PGM component 120 deposited onto the surface of the refractory metal oxide support 110, and a PGM modifier 130 deposited onto the surface of the refractory metal oxide support 110. In some embodiments, the PGM component 120 is one of a plurality of PGM components 120. In some embodiments, the PGM modifier 130 is one of a plurality of PGM modifiers 130.

[0053] In some embodiments, the refractory metal oxide support 110 includes a crystalline structure. In some embodiments, the refractory metal oxide support 110 includes an amorphous structure. In some embodiments, the refractory metal oxide support 110 is a mixture of crystalline and amorphous structures.

[0054] In some embodiments, the refractory metal oxide support 110 is composed by a first ceria component and alumina. In some embodiments, the refractory metal oxide support 110 contains certain weight percentage of ceria. For example, the refractory metal oxide support 110 includes 5 wt. % to about 40 wt. % ceria with respect to the total weight of the refractory metal oxide support. For example, a content of a first ceria component is from about 5 wt. %71626869359.1240023WO01 / ECM-24-1158WOto about 40 wt. %, from about 10 wt. % to about 30 wt. %, from about 15 wt. % to about 25 wt. %, with respect to a total weight of the refractory metal oxide support 110.

[0055] In some embodiments, the first ceria component in the refractory metal oxide support 110 is ceria of nanoscale crystallite randomly mixed with alumina in the refractory metal oxide support 110. In some embodiments, the average size of ceria crystallites is equal to or less than about 10 nm measured by the X-ray diffraction (XRD) method. The mixture of the first ceria component and the alumina may be a commercially available CeCh-AhCh mixture. For example, the CeCh-AhCh mixture may have 20 wt. % CeCh and 80 wt. % y-AhCh and an average CeCh crystallite size of 5 nm approximately.

[0056] The PGM component 120 may be measured by weight with respect to the weight of the refractory metal oxide support 110. In some embodiments, the loading of PGM component 120 is greater than 0.1 wt. % but up to about 3 wt. %, calculated on a metal basis. For example, the loading of PGM component 120 is about 0.1 wt. % to about 3 wt. %, about 0.2 wt. % to about 2.5 wt. %, about 0.3 wt. % to about 2 wt. %, about 0.4 wt. % to about 1.5 wt. %. In some embodiments, the loading of PGM component 120 is about 0.5 wt. %. In some embodiments, the loading of PGM component 120 is about 2 wt. %. The PGM component 120 may be presented as either PGM metal nanoparticles or PGM oxide nanoparticles supported on the surface of the refractory metal oxide support 110.

[0057] In some embodiments, the PGM component 120 includes one or more of palladium, rhodium, platinum, or a combination of thereof. For example, a precursor of palladium includes a solution of palladium nitrate, a precursor of rhodium includes a solution of rhodium nitrate, and a precursor of platinum includes a solution of platinum nitrate or a solution of platinum tetraethanolamine hydroxide.

[0058] The PGM modifier 130 includes a second ceria component deposited onto the refractory metal oxide support 110 and adjacent to the PGM component 120.

[0059] In some embodiments, a content of the second ceria component is 1-20 wt. % with respect to a total weight of the refractory metal oxide support. For example, the content of the second ceria component is 5-15 wt. % with respect to a total weight of the refractory metal oxide support. If the content of the second ceria component is too low, it cannot provide sufficient CeCh sites adjacent to the PGM component. On the other hand, if the content of the second ceria component is too high, it can substantially reduce the porosity of the refractory metal oxide support, which may cause a diffusion issue during a catalytic reaction.81626869359.1240023WO01 / ECM-24-1158WO

[0060] Interestingly, it was found in this invention that the second ceria component of the PGM modifier 130 can significantly improve the efficiency of the PGM component on the refractory metal oxide support 110 containing the first ceria component. The approach introduces two domains of ceria (i.e., the first ceria component and the second ceria component) on alumina and promote intimate interactions between the PGM component 120 and ceria. Comparing two three-way conversion catalyst composites having the same loading amount of the PGM component 120, one having the design of two domains of ceria is demonstrated to have improved performance over the other having no such design. Such design of two domains of ceria enables the development of a new three-way conversion catalyst composite that has a reduced PGM loading (e.g., up to 25%-50% reduced PGM loading) without decreasing the performance of the catalyst composite, thereby lowering the manufacture cost of the three-way conversion catalyst composite.

[0061] In some embodiments, the method further includes depositing the PGM modifier and the PGM component on the refractory metal oxide support through a co-impregnation method or a sequential impregnation method. In some embodiments, the PGM modifier and the PGM component may be implemented on to the refractory metal oxide support concurrently. In some embodiments, the PGM modifier may be implemented on to the refractory metal oxide support after the PGM component is implemented on to the refractory metal oxide support. In some other embodiments, the PGM modifier may be implemented on to the refractory metal oxide support before the he PGM component is implemented on to the refractory metal oxide support.

[0062] In some embodiments, depositing the PGM modifier includes depositing the PGM modifier using a soluble cerium salt precursor or a colloidal solution of ceria nanoparticles. In some embodiments, a precursor of the second ceria component includes one or more of a solution of cerium nitrate and a colloidal CeCh solution.

[0063] In some embodiments, the method further includes depositing an additive on the refractory metal oxide support through a wet impregnation method. The additive is configured to further improve the activity of the PGM component.

[0064] In some embodiments, the additive is an oxide or a salt of Y, La, Pr, Nd, Sm, Gd, or a combination thereof. For example, the additive may be deposited as PreOn using a soluble precursor of Pr such as Pr nitrate.

[0065] In some embodiments, the amount of the additive may be in a range of 0.5% to 3% by weight relative to the refractory metal oxide support.91626869359.1240023WO01 / ECM-24-1158WO

[0066] In some embodiments, the additive, the PGM modifier, and the PGM component may be co-impregnated on the refractory metal oxide support. In some embodiments, the additive, the PGM modifier, and the PGM component may be impregnated on the refractory metal oxide support in a sequential manner. The impregnation may be performed through an incipient wetness technique.

[0067] FIG. 2 schematically shows a catalyst article in accordance with some embodiments of the present disclosure. FIG. 3 schematically shows an enlarged partial cross-sectional view of the catalyst article in FIG. 2.

[0068] FIG. 2 illustrates a catalyst article including a substrate 200. The substrate 200 has a plurality of porous walls 201 forming a plurality of fine, parallel gas flow passages 202. The substrate 200 has an upstream end face 203 and a corresponding downstream end face 204 identical to upstream end face 203. The substrate is a flow-through substrate has a cylindrical shape and has a cylindrical outer surface. The gas flow passages 202 extend through substrate 200 from the upstream end face 203 to the downstream end face 204. The gas flow passages 202 are unobstructed so as to permit the flow of a fluid, e.g., a gas stream, longitudinally through substrate 200 via gas flow passages 202 thereof.

[0069] As shown in FIG. 3, the plurality of porous walls 301 of the sub state 300 are so dimensioned and configured that gas flow passages 302 have a substantially regular polygonal shape. As shown, at least one coating layers can be applied to the porous walls 301. In some embodiments, the substrate 300 may be coated by one coating layer 302. In some embodiments, the substrate 200 may be coated by two or more coating layers, including e.g., a first coating layer 302 and a second coating layer 303.

[0070] In some embodiments, the substrate 300 may be constructed of any material typically used for preparing automotive catalysts and typically comprises a ceramic or a metal monolithic honeycomb structure. In one embodiment, the substrate 300 is a ceramic substrate, metal substrate, ceramic foam substrate, polymer foam substrate, or a woven fiber substrate. The substrate 300 typically provides a plurality of wall surfaces upon which washcoats comprising the catalyst compositions described herein above are applied and adhered, thereby acting as a carrier for the catalyst compositions.

[0071] Ceramic materials used to construct the substrate 300 may include any suitable refractory material, e.g., cordierite, mullite, cordierite-alumina, aluminum titanate, silicon carbide, silicon nitride, zircon mullite, spodumene, alumina-silica magnesia, zircon silicate, sillimanite, magnesium silicates, zircon, petalite, alumina, aluminosilicates and the like.101626869359.1240023WO01 / ECM-24-1158WO

[0072] Exemplary metallic materials used to construct the substrate 300 may include heat resistant metals and metal alloys such as titanium and stainless steel as well as other alloys in which iron is a substantial or major component. Such alloys may contain one or more nickel, chromium, and / or aluminum, and the total amount of these metals may advantageously comprise at least 15 wt. % of the alloy, e.g., 10-25 wt. % of chromium, 3-8 % of aluminum, and up to 20 wt. % of nickel. The alloys may also contain small or trace amounts of one or more metals such as manganese, copper, vanadium, titanium, and the like. The surface of the metal substrate may be oxidized at high temperature, e.g., 1000 °C and higher, to form an oxide layer on the surface of the substrate, improving the corrosion resistance of the alloy and facilitating adhesion of the washcoat layer to the metal surface.

[0073] Any suitable substrate may be employed, such as a monolithic flow-through substrate having a plurality of fine, parallel gas flow passages extending from an inlet to an outlet face of the substrate such that passages are open to fluid flow. The passages, which are essentially straight paths from the inlet to the outlet, are defined by walls on which the catalytic material is coated as a washcoat so that the gases flowing through the passages contact the catalytic material. The flow passages of the monolithic substrate are thin-walled channels which are of any suitable cross-sectional shape, such as trapezoidal, rectangular, square, sinusoidal, hexagonal, oval, circular, and the like. Such structures contain from about 60 to about 1200 or more gas inlet openings (i.e., “cells”) per square inch of cross section (cpsi), more usually from about 300 to 900 cpsi. The wall thickness of flow-through substrates can vary, with a typical range being between 0.002 and 0.1 inches. A representative commercially available flow-through substrate is a cordierite substrate having 400 cpsi and a wall thickness of 6 mil, or 600 cpsi and a wall thickness of 4 mil. However, it will be understood that the invention is not limited to a particular substrate type, material, or geometry.

[0074] In alternative embodiments, the substrate may be a wall-flow substrate, wherein each passage is blocked at one end of the substrate body with a non-porous plug, with alternate passages blocked at opposite end-faces. This requires that gas flow through the porous walls of the wall-flow substrate to reach the exit. Such monolithic substrates may contain up to about 700 or more cpsi, such as about 100 to 400 cpsi and more typically about 200 to about 300 cpsi. The cross-sectional shape of the cells can vary as described above. Wall-flow substrates typically have a wall thickness between 0.002 and 0.1 inches. A representative commercially available wall-flow substrate is constructed from a porous cordierite, an example of which has 200 cpsi and 10 mil wall thickness or 300 cpsi with 8 mil wall thickness, and wall porosity between 45-65%. Other ceramic materials such as aluminum 111626869359.1240023WO01 / ECM-24-1158WOtitanate, silicon carbide and silicon nitride are also used as wall-flow filter substrates.However, it will be understood that the invention is not limited to a particular substrate type, material, or geometry. Note that where the substrate is a wall-flow substrate, the catalyst composition can permeate into the pore structure of the porous walls (i.e., partially or fully occluding the pore openings) in addition to being disposed on the surface of the walls. In one embodiment, the substrate has a flow through ceramic honeycomb structure, a wall-flow ceramic honeycomb structure, or a metal honeycomb structure.

[0075] FIG. 4 schematically shows a perspective view of a wall flow filter substrate 40 in accordance with some embodiments of the present disclosure. FIG. 5 schematically shows an enlarged cutaway view of a section of the wall flow filter substrate 40 in FIG. 4.

[0076] As shown in FIGs. 4 and 5, the wall flow filter substrate 40 has a plurality of passages 52 tubularly enclosed by the porous walls 53 of the wall flow filter substrate 40. The wall flow filter substrate 40 has an inlet end 54 and an outlet end 56. Alternate passages are plugged at the inlet end 54 with inlet plugs 58 and at the outlet end 56 with outlet plugs 60 to form opposing checkerboard patterns at the inlet end 54 and the outlet end 56, respectively. A gas stream 62 enters through the unplugged channel inlet 64, is stopped by outlet plug 60 and diffuses through porous walls 53 to the outlet side. The gas cannot pass back to the inlet side of walls because of inlet plugs 58. The porous walls are with one or more catalytic materials including the catalyst composite consistent with the embodiments of the present disclosure. The catalytic materials may be present on the inlet side, the outlet side alone, both the inlet and outlet sides of the catalyst article. In some embodiments, the wall itself may include all, or in part, of the catalytic materials.

[0077] FIGs. 6A-6J schematically show examples of catalyst articles in accordance with some embodiments of the present disclosure, where “CeC>2(A)” refers to the first ceria component, “CeC>2(B)” refers the second ceria component, and “ / ” connecting two components (e.g., component A / component B, or [component A] / [component B]) indicates that component A is supported on component B. The term “OSC” refers to an oxygen storage component, which exhibits an oxygen storage capability and often is an entity that has multivalent oxidation states and can actively react with oxidants such as oxygen (O2) or nitrogen oxides (NO or NO2) under oxidative conditions, or reacts with reductants such as carbon monoxide (CO), hydrocarbons (HC), or hydrogen (H2) under reduction conditions. Certain exemplary OSCs are include ceria composites optionally doped with early transition metal oxides, particularly zirconia, yttria, lanthana, praseodymia, neodymia, europia, samaria, ytterbia, gadolinia, or a mixture thereof.121626869359.1240023WO01 / ECM-24-1158WO

[0078] In some embodiments, the catalyst article includes a single layer on the substate (e.g., shown in FIGs. 6A-6E). In some embodiments, the catalyst article includes more than one layers. Separate composites or slurries may be used to coat the more than one layers onto the substrate. For example, the catalyst article can include at least two layers (e.g., shown in FIGs. 6F-6J).

[0079] In some embodiments, the catalyst article exhibits zoned configuration in at least one layer on the substate. The at least one layer is in an axially zoned configuration. For example, a substate coated with a single layer may have a zoned configuration, or a substate coated with multiple layers may have a zoned configuration in one, some, or all of the multiple layers. In some embodiments, the zoned configuration of the at least one layer may split the at least one layer into multiple zones, including a first zone, a second zone, and so forth.

[0080] For example, for a layer including two zones, a first zone and a second zone, the first zone may be a front zone, and the second zone may be a rear zone. The first zone and the second zone may be disposed side by side along a length of the substrate. The first zone may extend from an inlet end of the substrate through the range of about 5 % to about 95%, about 10% to about 80%, about 17% to about 75% or about 20% to about 60% of the length of the substrate. The second zone may extend from an outlet end of the substrate through the range of about 5 % to about 95%, about 10% to about 80%, about 17% to about 75% or about 20% to about 60% of the length of the substrate. In some embodiments, the first zone and the second zone may layover each other. In some embodiments, the first zone and the second zone may not layover each other. In some embodiments, the first zone and the second zone may be separated by a gap.

[0081] FIGs. 7A-7D schematically show examples of emission treatment systems in accordance with some embodiments of the present disclosure. The emission treatment system is configured to treat an exhaust stream of an internal combustion engine. The emission treatment system includes an exhaust conduit in fluid communication with the internal combustion engine via an exhaust manifold, and a catalyst article disposed in the exhaust conduit and being configured to treat the exhaust stream. The catalyst article can be a three-way conversion catalyst article. The catalyst article includes a substrate, an oxygen storage component, a refractory metal oxide support, a PGM component, and a PGM modifier. The refractory metal oxide support comprises a ceria-alumina composite comprising a first ceria component mixed with alumina. The PGM modifier comprise a second ceria component adjacent to the PGM component.131626869359.1240023WO01 / ECM-24-1158WO

[0082] In some embodiments, the emission treatment system may include at least one three-way conversion (TWC) catalyst article. For example, the emission treatment system includes a three-way conversion catalyst article. In another example, the emission treatment system includes two three-way conversion catalyst articles, e.g., a first three-way conversion catalyst article (TWC-1) and a second three-way conversion catalyst article (TWC-2).

[0083] In some embodiments, the emission treatment system further includes a four-way conversion (FWC) catalyst article. The FWC catalyst article removes gaseous pollutants (CO, NOX, HC) as well as particulate matter (PM, such as soot particles) form the exhaust gas flow.

[0084] For example, the emission treatment system includes a three-way conversion catalyst article and a four-way conversion catalyst article arranged downstream of the three-way conversion catalyst article.

[0085] In another example, the emission treatment system includes two three-way conversion catalyst articles (e.g., TWC-1 and TWC-2 downstream of TWC-1) and a four-way conversion catalyst article. The four-way conversion catalyst article may be arranged downstream of the two three-way conversion catalyst articles or may be arranged downstream of TWC-1 and up stream of TW C -2.

[0086] FIG. 8 is a flowchart showing a method for preparing a catalyst article in accordance with an embodiment. The method includes providing, at 810, a substrate, and coating, at 820, a catalyst material onto the substate, the catalyst material comprising an oxygen storage component, a refractory metal oxide support, a PGM component, and a PGM modifier. The refractory metal oxide support comprises a ceria-alumina composite comprising a first ceria component mixed with alumina. The PGM modifier comprise a second ceria component adjacent to the PGM component.

[0087] Surprisingly, the second ceria component of the PGM modifier can significantly improve the efficiency of the PGM component on the refractory metal oxide support containing the first ceria component. The approach introduces two domains of ceria (i.e., the first ceria component and the second ceria component) on alumina and promote intimate interactions between the PGM component and ceria. Comparing two three-way conversion catalyst articles having the same loading amount of the PGM component, one having the design of two domains of ceria is demonstrated to have improved performance over the other having no such design. Such design of two domains of ceria enables the development of a new three-way conversion catalyst article that has a reduced PGM loading (e.g., up to 25%-141626869359.1240023WO01 / ECM-24-1158WO50% reduced PGM loading) without decreasing the performance of the catalyst article, thereby lowering the manufacture cost of the three-way conversion catalyst article.

[0088] In some embodiments, the PGM component includes one or more of palladium, rhodium, platinum, or a combination of thereof. For example, a precursor of palladium includes a solution of palladium nitrate, a precursor of rhodium includes a solution of rhodium nitrate, and a precursor of platinum includes a solution of platinum nitrate or platinum tetraethanolamine hydroxide.

[0089] In some embodiments, the first ceria component is ceria of nanoscale crystallites randomly mixed with alumina in the refractory metal oxide support. In some embodiments, the average size of ceria crystallites is equal to or less than about 10 nm measured by the X-ray diffraction (XRD) method. The mixture of the first ceria component and the alumina may be a commercially available CeCh-AhCh mixture. For example, the CeCh-AhCh mixture may have 20 wt. % CeCh and 80 wt. % y-AhCh and an average CeCh crystallite size of 5 nm approximately.

[0090] In some embodiments, the refractory metal oxide support includes 5 wt. % to about 40 wt. % ceria with respect to the total weight of the refractory metal oxide support. For example, a content of a first ceria component is from about 5 wt. % to about 40 wt. %, from about 10 wt. % to about 30 wt. %, from about 15 wt. % to about 25 wt. %, with respect to a total weight of the refractory metal oxide support.

[0091] In some embodiments, a content of the second ceria component is 1-20 wt. % with respect to a total weight of the refractory metal oxide support. For example, the content of the second ceria component is 10 wt. % with respect to a total weight of the refractory metal oxide support.

[0092] In some embodiments, the method further includes depositing the PGM modifier and the PGM component on the refractory metal oxide support through a co-impregnation method or a sequential impregnation method. In some embodiments, the PGM modifier and the PGM component may be implemented on to the refractory metal oxide support concurrently. In some embodiments, the PGM modifier may be implemented on to the refractory metal oxide support after the he PGM component is implemented on to the refractory metal oxide support. In some other embodiments, the PGM modifier may be implemented on to the refractory metal oxide support before the he PGM component is implemented on to the refractory metal oxide support.151626869359.1240023WO01 / ECM-24-1158WO

[0093] In some embodiments, depositing the PGM modifier includes depositing the PGM modifier using a soluble cerium salt precursor or a colloidal solution of ceria nanoparticles. In some embodiments, a precursor of the second ceria component includes one or more of a solution of cerium nitrate and a colloidal CeCh solution.

[0094] In some embodiments, the method further includes depositing an additive on the refractory metal oxide support through a wet impregnation method. The additive is configured to further improve the activity of the PGM component.

[0095] In some embodiments, the additive is an oxide or a salt of Y, La, Pr, Nd, Sm, Gd, or a combination thereof. For example, the additive may be deposited as PreOn using a soluble precursor of Pr such as Pr nitrate.

[0096] In some embodiments, the amount of the additive may be in a range of 0.5% to 3% by weight relative to the refractory metal oxide support.

[0097] In some embodiments, the additive, the PGM modifier, and the PGM component may be co-impregnated on the refractory metal oxide support. In some embodiments, the additive, the PGM modifier, and PGM component may be impregnated on the refractory metal oxide support in a sequential manner. The impregnation may be performed through an incipient wetness technique.EXAMPLES

[0098] Aspects of the current disclosure are more fully illustrated by the following examples, which are set forth to illustrate certain aspects of the present disclosure and are not to be construed as limiting.

[0099] Example 1: Reference monolith sample Al (with 90 g / ft3Pd and 10 g / ft3Rh)

[0100] Reference monolith sample Al is a coated monolith catalyst article having two coating layers, a bottom layer and a top layer. The bottom layer contains Pd, and the top layer contains Rh. A preparation process of each coating layer includes PGM impregnation, slurry preparation, coating catalyst slurry on monolith substrate, drying and calcination.

[0101] Bottom layer

[0102] Pd was impregnated onto two different supports. 50% Pd, as Pd nitrate solution, was impregnated on a 4% La2C>3-doped y-AhCh support using an incipient wetness technique, and the other 50% Pd was impregnated on an OSC material (40% CeCh, 50% ZrCh, 5% La2Os and 5% Y2O3) using the same technique. The AI2O3 / OSC weight ratio was 0.64. A slurry161626869359.1240023WO01 / ECM-24-1158WOwas made by suspending the two types of Pd-containing powders in deionized water that also contained a dispersed colloidal Ce / Zr oxide (CeCh / ZrCh weight ratio = 1:1) binder (about 10 wt. % of washcoat) and a barium acetate additive (about 9 wt. % of washcoat). The resulting slurry was milled in a continuous mill to reach D90 < 12-14 pm (90% particles having a diameter less than 12-14 pm). The slurry pH was adjusted to 3.5-4.5 using a nitric acid solution. The final slurry, contained about 40% solid, was washcoated on a cordierite monolith (4.16” diameter x 4.41” length with a cell density of 750 cell / in2and a 2-mil wall thickness). The coated sample was dried by ramping temperature to 550 °C in 1.5 hours and then calcined at 550 °C for 1 hour. After calcination, the loading of the bottom layer was 2.30 g / in3, including 90 g / ft3Pd.

[0103] Top layer

[0104] A solution of Rh nitrate was impregnated on a 4% La2O3-doped Y-AI2O3 support using the incipient wetness technique. A slurry was made by suspending the Rh-containing powder and an OSC material (40% CeCh, 50% ZrCh, 5% La2Os and 5% Y2O3) in deionized water. The AI2O3 / OSC weight ratio was 1.86. The slurry was milled to D90 < 12-14 pm and adjusted to pH = 3.5-4.5 using a nitric acid solution. The final slurry, containing about 25% solid, was washcoated on the top of the bottom layer. The coated sample was dried by ramping temperature to 550 °C in 1.5 hours and then calcined at 550 °C for 1 hour. After calcination, the loading of the top layer was 1.03 g / in3, including 10 g / ft3Rh.

[0105] The fully coated catalyst article (bottom and top layers) contained 3.33 g / in3catalyst loading in total, including 90 g / ft3Pd and 10 g / ft3Rh, i.e., Pd / Rh = 90 / 10.

[0106] Example 2: Reference monolith sample A2 (with 45 g / ft3Pd and 10 g / ft3Rh)

[0107] Reference monolith sample A2 is a coated monolith catalyst article having two coating layers, a top layer and a bottom layer. The bottom layer contains Pd, and the top layer contains Rh. A preparation process of each coating layer includes PGM impregnation, slurry preparation, coating catalyst slurry on monolith substrate, drying and calcination.

[0108] Bottom layer

[0109] Pd was impregnated onto two different supports. 50% Pd, as Pd nitrate solution, was impregnated on a 4% La2O3-doped Y-AI2O3 support using the incipient wetness technique, and the other 50% Pd was impregnated on an OSC material (40% CeO2, 50% ZrO2, 5% La2O3 and 5% Y2O3) using the same technique. The AI2O3 / OSC weight ratio was 0.64. A slurry was made by suspending the two types of Pd-containing powders in deionized water171626869359.1240023WO01 / ECM-24-1158WOthat also contained a dispersed colloidal Ce / Zr oxide (CeCh / ZrCh weight ratio = 1:1) binder (10 wt. % of the total washcoat) and a barium acetate additive (9% of the total washcoat). The resulting slurry was milled in a continuous mill to reach D90 < 12-14 pm (90% particles having a diameter less than 12-14 pm). The slurry pH was adjusted to 3.5-4.5 using a nitric acid solution. The final slurry, contained about 40% solid, was washcoated on a cordierite monolith (4.16” diameter x 4.41” length with a cell density of 750 cell / in2and a 2-mil wall thickness). The coated sample was dried by ramping temperature to 550 °C in 1.5 hours and then calcined at 550 °C for 1 hour. After calcination, the loading of the bottom layer was 2.28 g / in3, including 45 g / ft3Pd.

[0110] Top layer[OlH] A solution of Rh nitrate was impregnated on a 4% La2O3-doped Y-AI2O3 support using the incipient wetness technique. A slurry was made by suspending the Rh-containing powder and an OSC material (40% CeCh, 50% ZrCh, 5% La2Os and 5% Y2O3) in deionized water. The AI2O3 / OSC weight ratio was 1.86. The slurry was milled to D90 < 12-14 pm and adjusted to pH = 3.5-4.5 using a nitric acid solution. The final slurry, containing about 25% solid, was washcoated on the top of the bottom layer. The coated sample was dried by ramping temperature to 550 °C in 1.5 hours and then calcined at 550 °C for 1 hour. After calcination, the loading of the top layer was 1.03 g / in3, including 10 g / ft3Rh.

[0112] The fully coated catalyst article (bottom and top layers) contained 3.31 g / in3catalyst loading in total, including 45 g / ft3Pd and 10 g / ft3Rh, i.e., i.e., Pd: Rh = 45:10.

[0113] Example 3: Inventive monolith sample Bl (with 45 g / ft3Pd and 10 g / ft3Rh)

[0114] Inventive monolith sample Bl is a coated monolith catalyst article, which contained two coating layers with the bottom layer containing Pd and the top layer containing Rh. A preparation process of each coating layer includes PGM impregnation, powder calcination (for Pd-containing powder), slurry preparation, coating catalyst slurry on monolith substrate, drying and calcination.

[0115] Bottom layer

[0116] A mixed solution of Pd nitrate, Ce nitrate, and Pr nitrate was co-impregnated on a CeCh-AhCh support using the incipient wetness technique, where the CeCh-AhCh support was a bulk mixture of 20 wt. % CeCh and 80 wt. % Y-AI2O3 and the average crystallite size of CeCh was 5 nm. The loadings of the co-impregnated PreOu and CeCh were 1% and 9% by weight relative to the support, respectively. The amount of Pd impregnated on the CeCh-181626869359.1240023WO01 / ECM-24-1158WOAI2O3 support was 50% of the total Pd in the catalyst. The other 50% Pd was impregnated on an OSC material (40% CeCh, 50% ZrCh, 5% La2Ch and 5% Y2O3) using the same technique. The AhCh-CeCh / OSC weight ratio was 0.64. These two types of Pd-containing powders were calcined at 550 °C for 2 hours. A slurry was made by suspending the calcined Pd-containing powders in deionized water that also contained a dispersed colloidal Ce / Zr oxide (CeCh / ZrCh weight ratio = 1:1) binder (10 wt. % of the total washcoat) and a barium acetate additive (9 wt. % of the total washcoat). The resulting slurry was milled in a continuous mill to reach D90 < 12-14 pm (90% particles having a diameter less than 12-14 pm). The slurry pH was adjusted to 3.5-4.5 using a nitric acid solution. The final slurry, contained about 40% solid, was washcoated on a cordierite monolith (4.16” diameter x 4.41” length with a cell density of 750 cell / in2and a 2-mil wall thickness). The coated sample was dried by ramping temperature to 550 °C in 1.5 hours and then calcined at 550 °C for 1 hour. After calcination, the loading of the bottom layer was 2.34 g / in3, including 45 g / ft3Pd.

[0117] Top layer

[0118] A solution of Rh nitrate was impregnated on a 4% La2O3-doped Y-AI2O3 support using the incipient wetness technique. A slurry was made by suspending the Rh-containing powder and an OSC material (40% CeO2, 50% ZrO2, 5% La2O3 and 5% Y2O3) in deionized water. The AI2O3 / OSC weight ratio was 1.86. The slurry was milled to D90 < 12-14 pm and adjusted to pH = 3.5-4.5 using a nitric acid solution. The final slurry, containing about 25% solid, was washcoated on the top of the bottom layer. The coated sample was dried by ramping temperature to 550 °C in 1.5 hours and then calcined at 550 °C for 1 hour. After calcination, the loading of the top layer was 1.03 g / in3, including 10 g / ft3Rh.

[0119] The fully coated catalyst article (bottom layer + top layer) contained 3.37 g / in3catalyst loading in total, including 45 g / ft3Pd and 10 g / ft3Rh, i.e., Pd: Rh = 45:10.

[0120] Example 4: Inventive monolith sample B2 (with 67.5 g / ft3Pd and 10 g / ft3Rh)

[0121] Inventive monolith sample B2 is a coated monolith catalyst article having two coating layers, a bottom layer and a top layer. The bottom layer contains Pd, and the top layer contains Rh. A preparation process of each coating layer includes PGM impregnation, powder calcination (for Pd-containing powder), slurry preparation, coating catalyst slurry on monolith substrate, drying and calcination.

[0122] Bottom layer191626869359.1240023WO01 / ECM-24-1158WO

[0123] A mixed solution of Pd nitrate, Ce nitrate and Pr nitrate was co-impregnated on a CeCh-AhCh support using the incipient wetness technique, where the CeCh-AhCh support was a bulk mixture of 20 wt. % CeCh and 80 wt. % y-AhCh and the average crystallite size of CeCh was 5 nm. The loading of the co-impregnated PreOn and CeCh were 1% and 9% by weight relative to the support, respectively. The amount of Pd impregnated on the CeCh-AI2O3 support was 50% of the total Pd in the catalyst. The other 50% Pd was impregnated on an OSC material (40% CeCh, 50% ZrCh, 5% La2Ch and 5% Y2O3) using the same technique. The AhCh-CeCh / OSC weight ratio was 0.64. These two types of Pd-containing powders were calcined at 550 °C for 2 hours. A slurry was made by suspending the calcined Pd-support powders in deionized water that also contained a dispersed colloidal Ce / Zr oxide (CeCh / ZrCh weight ratio = 1:1) binder (10 wt. % of the total washcoat) and a barium acetate additive (9 wt. % of the total washcoat). The resulting slurry was milled in a continuous mill to reach D90 < 12-14 pm (90% particles having a diameter less than 12-14 pm). The slurry pH was adjusted to 3.5-4.5 using a nitric acid solution. The final slurry, contained about 40% solid, was washcoated on a cordierite monolith (4.16” diameter x 4.41” length with a cell density of 750 cell / in2and a 2-mil wall thickness). The coated sample was dried by ramping temperature to 550 °C in 1.5 hours and then calcined at 550 °C for 1 hour. After calcination, the loading of the coated bottom layer catalyst was 2.36 g / in3, including 67.5 g / ft3Pd.

[0124] Top layer

[0125] A solution of Rh nitrate was impregnated on a 4% La2O3-doped Y-AI2O3 support using the incipient wetness technique. A slurry was made by suspending the Rh-containing powder and an OSC material (40% CeO2, 50% ZrO2, 5% La2O3 and 5% Y2O3) in deionized water. The AI2O3 / OSC weight ratio was 1.86. The slurry was milled to D90 < 12-14 pm and adjusted to pH = 3.5-4.5 using a nitric acid solution. The final slurry, containing about 25% solid, was washcoated on the top of the Pd-containing catalyst layer. The coated sample was dried by ramping temperature to 550 °C in 1.5 hours and then calcined at 550 °C for 1 hour. After calcination, the loading of the top layer was 1.03 g / in3, including 10 g / ft3Rh.

[0126] The fully coated catalyst article (bottom layer + top layer) contained 3.39 g / in3catalyst loading in total, including 67.5 g / ft3Pd and 10 g / ft3Rh, i.e., Pd: Rh = 67.5 / 10.

[0127] Example 5: Inventive monolith sample B3 (with 67.5 g / ft3Pd and 7.5 g / ft3Rh)

[0128] Inventive monolith sample B3 is a coated monolith catalyst article, which contained two coating layers a bottom layer and a top layer. The bottom layer contains Pd, and the top201626869359.1240023WO01 / ECM-24-1158WOlayer contains Rh. A preparation process of each coating layer includes PGM impregnation, powder calcination, slurry preparation, coating catalyst slurry on monolith substrate, drying and calcination.

[0129] Bottom layer

[0130] A mixed solution of Pd nitrate, Ce nitrate and Pr nitrate was co-impregnated on a CeCh-AhCh support using the incipient wetness technique, where the CeCh-AhCh support was a bulk mixture of 20 wt. % CeCh and 80 wt. % y-AhCh and the average crystallite size of CeCh was 5 nm. The loading of the co-impregnated PreOn and CeCh were 1% and 9% by weight relative to the support, respectively. The amount of Pd impregnated on the CeCh-AI2O3 support was 50% of the total Pd in the catalyst. The other 50% Pd was impregnated on an OSC material (40% CeCh, 50% ZrCh, 5% La2Ch and 5% Y2O3) using the same technique. The AhCh-CeCh / OSC weight ratio was 0.64. These two types of Pd-containing powders were calcined at 550 °C for 2 hours. A slurry was made by suspending the calcined Pd-containing powders in deionized water that also contained a dispersed colloidal Ce / Zr oxide (CeCh / ZrCh weight ratio = 1:1) binder (10 wt. % of the total washcoat) and a barium acetate additive (9 wt. % of the total washcoat). The resulting slurry was milled in a continuous mill to reach D90 < 12-14 pm (90% particles having a diameter less than 12-14 pm). The slurry pH was adjusted to 3.5-4.5 using a nitric acid solution. The final slurry, contained about 40% solid, was washcoated on a cordierite monolith (4.16” diameter x 4.41” length with a cell density of 750 cell / in2 and a 2-mil wall thickness). The coated sample was dried by ramping temperature to 550 °C in 1.5 hours and then calcined at 550 °C for 1 hour. After calcination, the weight of the coated bottom layer catalyst was 2.36 g / in3, including 67.5 g / ft3Pd.

[0131] Top Layer

[0132] A mixed solution of Rh nitrate and a colloidal ceria dispersion was impregnated on a CeCh-AhCh support using the incipient wetness technique, where the CeCh-AhCh support was a bulk mixture of 20 wt. % CeCh and 80 wt. % Y-AI2O3 and the average crystallite size of CeCh was 5 nm. The loading of the colloidal ceria (as CeCh) was 5% by weight relative to the support. The Rh-containing powder was then calcined at 550 °C in air for 2 hours. A slurry was made by suspending the calcined Rh-containing powder and an OSC material (40% CeO2, 50% ZrO2, 5% La2O3 and 5% Y2O3) in deionized water. The CeO2-A12O3 / OSC weight ratio was 1.86. The slurry was milled to D90 < 12-14 pm and adjusted to pH = 3.5-4.5 using a nitric acid solution. The final slurry, containing about 25% solid, was washcoated on the top of the Pd-containing catalyst layer. The coated sample was dried by ramping temperature to211626869359.1240023WO01 / ECM-24-1158WO550 °C in 1.5 hours and then calcined at 550 °C for 1 hour. After calcination, the loading of the top layer was 1.06 g / in3, including 7.5 g / ft3Rh.

[0133] The fully coated catalyst article (bottom layer + top layer) contained 3.42 g / in3catalyst loading in total, including 67.5 g / ft3Pd and 7.5 g / ft3Rh, i.e., Pd: Rh = 67.5:7.5.

[0134] Example 6: Testing results of monolith samples

[0135] The monolith samples of Examples 1-5 were mounted in steel converter cans and aged in an exhaust pipeline of a gasoline engine which was operated under exothermic 4-mode aging cycles. The aging duration was 50 hours at a maximum bed temperature of about 990°C. The aged catalytic converters were tested in a close-coupled position on a Daimler 4-cylinder gasoline engine with an engine displacement of 2.0 L. The test drive cycle was FTP-75, following the certified procedures and tolerances.

[0136] Table 1 summarizes the FTP-75 tailpipe emission data of THC (total hydrocarbons), NOX, and CO acquired on the test engine bench. With 25% less Pd, Example 4 displayed comparable tailpipe emissions to Example 1 on FTP-75. Compared to Example 1, Example 5 with 25% less Pd and Rh exhibited equivalent tailpipe emissions on FTP-75. At the same PGM loading, Example 3 gave substantially lower THC, NOX, and CO at tailpipe in reference to Example 2.Table 1PGM PGM Ratio Total HC, NOX, CO, Example Loading,(Pd / Rh) mg / mile mg / mile mg / mile g / ft3Example 1 100 90 / 10 108 108 407 Example 2 55 45 / 10 130 129 565 Example 3 55 45 / 10 122 106 498 Example 4 77.5 67.5 / 10 109 98 399 Example 5 72.5 67.5 / 7.5 107 106 390

[0137] Example 7: Catalyst composite Cl (2% Pd on alumina (IPt / AhO.;))

[0138] A solution of Pd nitrite was impregnated on a y-AEOs support using the incipient technique. The Pd impregnated powder was calcined at 550 °C for 2 hours. The calcined powder was suspended in deionized water to form a slurry containing about 30% solid. A221626869359.1240023WO01 / ECM-24-1158WOboehmite alumina binder (5 wt. % relative to the catalyst) was added to the slurry and milled for 10 minutes at 400 rpm. The slurry was dried at 100 °C to obtain a dried powder. The dried powder was then calcined at 550 °C in air for 2 hours, crashed and sieved to 250 - 500 pm fraction to obtain the catalyst composite 1. This catalyst composite 1 is designated as 2Pt / Al2O3.

[0139] Example 8: Catalyst composite C2 (2% Pd, 9% CeCh and 1% PreOu on alumina (2Pt-9Ce1Pr / Al2O3))

[0140] A mixed solution of Pd nitrite, Ce nitrate and Pr nitrate was impregnated on a y-AhCh support using the incipient technique. The impregnated powder was calcined at 550 °C for 2 hours. The calcined powder was suspended in deionized water to form a slurry containing about 30% solid. A boehmite alumina binder (5 wt. % relative to the catalyst) was added to the slurry and milled for 10 minutes at 400 rpm. The slurry was dried at 100 °C to obtain dried powder. The dried powder was then calcined at 550 °C in air for 2 hours, crashed and sieved to 250 - 500 pm fraction to obtain the catalyst composite 2. This catalyst composite 2 is designated as 2Pt-9Ce1Pr / Al2O3.

[0141] Example 9: Catalyst composite C3 (2% Pd on CeOi-AhCh (IPt / CeOi-AhCh))

[0142] A solution of Pd nitrite was impregnated on a CeCh-AhCh support using the incipient wetness technique, where the CeCh-AhCh support was a bulk mixture of 20 wt. % CeO2and 80 wt. % y-AhCh and the average crystallite size of CeO2was 5 nm. The Pd impregnated powder was calcined at 550 °C for 2 hours. The calcined powder was suspended in deionized water to form a slurry containing about 30% solid. A boehmite alumina binder (5 wt. % relative to the catalyst) was added to the slurry and milled for 10 minutes at 400 rpm. The slurry was dried at 100 °C to obtain dried powder. The dried powder was then calcined at 550 °C in air for 2 hours, crashed and sieved to 250 - 500 pm fraction to obtain the catalyst composite 3. This catalyst composite 3 is designated as 2Pt / CeO2-Al2O3.

[0143] Example 10: Catalyst composite C4 (2% Pd, 9% CeCh and 1% PreOu on CeCh-AI2O3 (2Pt-9CelPr / CeO2-A12O3))

[0144] A mixed solution of Pd nitrite, Ce nitrate and Pr nitrate was impregnated on a CeO2-Al2O3support using the incipient wetness technique, where the CeO2-Al2O3support was a bulk mixture of 20 wt. % CeO2and 80 wt. % γ-Al2O3and the average crystallite size of CeO2231626869359.1240023WO01 / ECM-24-1158WOwas 5 nm. The Pd impregnated powder was calcined at 550 °C for 2 hours. The calcined powder was suspended in deionized water to form a slurry containing about 30% solid. A boehmite alumina binder (5 wt. % relative to the catalyst) was added to the slurry and milled for 10 minutes at 400 rpm. The slurry was dried at 100 °C to obtain dried powder. The dried powder was then calcined at 550 °C in air for 2 hours, crashed and sieved to 250 - 500 pm fraction to obtain the catalyst composite 4. This catalyst composite 4 is designated as 2Pt-9Ce1Pr / CeO2-Al2O3.

[0145] Example 11: Evaluation of catalyst composites

[0146] Procedures for evaluating the catalyst composites

[0147] Before evaluation, all catalyst composites were aged at 1050 °C for 5 hours with 10% H2O under an alternating lean / rich feed (10 minutes 4% air / 10 minutes 4% H2 / N2). The aged catalyst composites were evaluated in a powder reactor using a light-off protocol with a λ=1 oscillating feed (λ=0.95 / 1.05 cycled at 0.5 Hz) from 175 to 450 °C at a monolith equivalent GHSV of 70,000 h’1. For light-off tests, the lean feed (λ=1.05) consisted of 0.7% CO, 0.22% H2, 3000 ppm HC (Cl) (propene: propane =2:1), 1500 ppm NO, 14% CO2, 10% H2O and -1.8% O2. The rich feed (λ=0.95) included 2.33% CO, 0.77% H2, 3000 ppm HC (Cl), 1500 ppm NO, 14% CO2, 10% H2O and -0.7% O2. The exact lambda values are finetuned by adjusting the O2 level based on an upstream λ-sensor. Two consecutive light-off runs were performed. The first light-off run (Run 1) is used as catalyst de-greening (or stabilization), and the second light-off (Run 2) data are used for activity comparison. The concentrations of carbon monoxide (CO), nitric oxide (NO) and hydrocarbons (HC) were continuously measured before and after catalysts. The conversion of a component (CO, NO or HC) is calculated as the percent of disappearance, i.e., Conversion = (Inlet concentration -Outlet concentration) / Inlet concentration x 100%. Catalytic activity of the catalyst composites was also characterized by catalyst light-off temperature, which is defined as the temperature required to achieve 50% conversion in a conversion - temperature plot. Light-off temperature is denoted as T50. Light-off temperatures for CO, NO and HC are expressed as CO T50, NO T50 and HC T50, respectively. The lower the T50 value, the higher the catalyst activity.

[0148] Evaluation Results of the catalyst composites241626869359.1240023WO01 / ECM-24-1158WO

[0149] FIG. 9 shows the T50 values for CO, NO and HC from Run 2. The overall catalytic activities follow the ranking: 2Pt-9Ce1Pt / CeO2-Al2O3> 2Pt / CeO2-Al2O3> 2Pt-9Ce1Pr / Al2O3> 2Pt / Al2O3.

[0150] Example 12: XRD and TEM Analysis of the catalyst composites

[0151] Three catalyst composite characterization samples were prepared and characterized for X-ray Diffraction (XRD) analysis and Scanning Transmission Electron Microscopy (STEM) coupled with Energy-Dispersive Spectroscopy (EDS) (STEM / EDS) analysis.

[0152] Preparation of Characterization Samples

[0153] Characterization Sample D1 (2Pd / CeO2-Al2O3)

[0154] A solution of Pd nitrate was impregnated on the CeCE-AhCE support (20 wt. % CeO2). The impregnated sample was calcined at 550 °C for 2 hours.

[0155] Characterization Sample D2 (2Pd-10Ce / CeO2-Al2O3)

[0156] A mixed solution of Pd nitrate and Ce nitrate was impregnated on the CeCE-AhCE support (20 wt. % CeO2). The impregnated sample was calcined at 550 °C for 2 hours.

[0157] Characterization Sample D3 (2Pd-10Ce(coll) / CeO2-Al2O3)

[0158] A mixed solution of Pd nitrate and colloidal CeO2was impregnated on the CeO2-Al2O3support (20 wt. % CeO2). The impregnated sample was calcined at 550 °C for 2 hours.

[0159] XRD analysis results

[0160] The XRD profiles of Characterization Samples 1-3 are shown in in FIGS. 10 A- 10C as XRD patterns A-C, respectively. The average crystallite size of CeCE was obtained for each characterization sample by using the Scherrer equation. The average crystallite sizes are 5.4 nm, 5.1 nm, and 4.9 nm for Characterization Sample DI, Characterization Sample D2, and Characterization Sample D3, respectively.

[0161] STEM / EDS results

[0162] The STEM / EDS images are shown in FIGs. 11 and 12 for Characterization Sample DI and Characterization Sample D2, respectively. FIG. 11A shows a HAADF (High-angle annular dark-field) image of Characterization Sample D1 at 1,000,000X magnification. FIG.1 IB shows the EDS mapping for Ce for the outlined area in FIG 11 A. FIG. 11C is EDS mapping for Al. FIG. 1 ID is EDS mapping for Pd. FIG. 12A shows a HAADF image of Characterization Sample D2 at 1,000,000X magnification. FIG. 12B shows the EDS mapping for Ce for the outlined area in FIG 12A. FIG. 12C is EDS mapping for Al. FIG. 12D is EDS mapping for Pd.251626869359.1240023WO01 / ECM-24-1158WO

[0163] The CeCh crystals in Characterization Sample DI, as shown in FIG. 11B, appears to be more discrete with a uniform size distribution. In comparison, the CeCh crystals in Characterization Sample D2, as shown in FIG. 12B, are more connected, which may be caused by the additional surface CeCh species impregnated on the CeCh-AhCh support. The Pd particles in Characterization Sample DI are less uniform in size with many larger Pd particles (Fig. 11D). On the other hand, the Pd particles in Characterization Sample D2 (FIG.12D) are dominated with smaller particles.

[0164] Various of the above-disclosed and other features and functions, or alternatives thereof, may be combined into many other different systems or applications. Various presently unforeseen or unanticipated alternatives, modifications, variations, or improvements therein may be subsequently made by those skilled in the art, each of which is also intended to be encompassed by the disclosed embodiments.261626869359.1

Claims

240023WO01 / ECM-24-1158WOCLAIMSWhat is claimed is:

1. A catalyst article comprising a substrate, an oxygen storage component, a refractory metal oxide support, a platinum group metal (PGM) component, and a PGM modifier,wherein the refractory metal oxide support comprises a ceria-alumina composite comprising a first ceria component mixed with alumina; andwherein the PGM modifier comprise a second ceria component adjacent to the PGM component.

2. The catalyst article of claim 1, wherein the PGM component includes one or more of palladium, rhodium, platinum, or a combination of thereof.

3. The catalyst article of claim 1, wherein the first ceria component is ceria of nanoscale crystallites randomly mixed with alumina in the refractory metal oxide support.

4. The catalyst article of claim 1, wherein a content of the first ceria component in the refractory metal oxide support ranges from 5% to 40% by weight with respect to a total weight of the refractory metal oxide support.

5. The catalyst article of claim 1, wherein a content of the second ceria component is 1-20 wt. % with respect to a total weight of the refractory metal oxide support.

6. The catalyst article of claim 5, wherein the content of the second ceria component is 5-15 wt. % with respect to a total weight of the refractory metal oxide support.

7. The catalyst article of claim 1, further comprising an additive deposited on the refractory metal oxide support.

8. The catalyst article of claim 7, wherein the additive is an oxide or a salt of Y, La, Pr, Nd, Sm, Gd, or a combination thereof.

9. The catalyst article of claim 1, wherein the catalyst has a signal layered structure, a multi-layered structure, or a zoned structure.271626869359.1240023WO01 / ECM-24-1158WO10. The catalyst article of claim 1, wherein the substrate includes a wall flow filter or a flow through monolith substrate.

11. A method for preparing a catalyst article comprising:providing a substrate; andcoating a catalyst material onto the substate, the catalyst material comprising an oxygen storage component, a refractory metal oxide support, a PGM component, and a PGM modifier,wherein the refractory metal oxide support comprises a ceria-alumina composite comprising a first ceria component mixed with alumina; andwherein the PGM modifier comprise a second ceria component adjacent to the PGM component.

12. The method of claim 11, wherein the PGM component includes one or more of palladium, rhodium, platinum, or a combination of thereof.

13. The method of claim 11, wherein the first ceria component is ceria of nanoscale crystallites randomly mixed with alumina in the refractory metal oxide support.

14. The method of claim 11, wherein a content of the first ceria component in the refractory metal oxide support ranges from 5% to 40% by weight with respect to a total weight of the refractory metal oxide support.

15. The method of claim 11, further comprising:depositing the PGM modifier and the PGM component on the refractory metal oxide support through a co-impregnation method or a sequential impregnation method.

16. The method of claim 15, wherein depositing the PGM modifier includes depositing the PGM modifier using a soluble cerium salt precursor or a colloidal solution of ceria nanoparticles.

17. The method of claim 11, wherein a content of the second ceria component is 1-20 wt. % with respect to a total weight of the refractory metal oxide support.281626869359.1240023WO01 / ECM-24-1158WO18. The method of claim 17, wherein the content of the second ceria component is 5-15 wt. % with respect to the total weight of the refractory metal oxide support.

19. The method of claim 11, further comprising:depositing an additive on the refractory metal oxide support through a wet impregnation method.

20. The method of claim 19, wherein the additive is an oxide or a salt of Y, La, Pr, Nd, Sm, Gd, or a combination thereof.

21. An emission treatment system for treatment of an exhaust stream of an internal combustion engine, the emission treatment system comprising an exhaust conduit in fluid communication with the internal combustion engine via an exhaust manifold, and a catalyst article according to any of claims 1 to 10 or a catalyst article obtainable or obtained from the method according to any of claims 11 to 20 disposed in the exhaust conduit and being configured to treat the exhaust stream.291626869359.1

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