Catalyzed Particulate Filter

Abstract

A particulate filter, an exhaust treatment system for a gasoline engine including a particulate filter, and a method for treating exhaust from a gasoline engine, the particulate filter comprising: a substrate including a plurality of porous walls extending longitudinally to form a plurality of parallel flow passages extending from an inlet end to an outlet end, a volume of the flow passages being inlet flow passages that are open at the inlet end and closed at the outlet end, and a volume of the flow passages being outlet flow passages that are closed at the inlet end and open at the outlet end; and an in-wall ternary conversion (TWC) coating within the inlet and outlet flow passages, the coating comprising a platinum group metal component, an alumina-based refractory metal oxide, and an oxygen storage component. and optionally an on-wall layer of inorganic particles in the inlet and / or outlet flow passages, the inorganic particles comprising one or more non-PGM components selected from alumina, zirconia, ceria, silica, titania, magnesium oxide, manganese oxide, zinc oxide, rare earth metal oxides other than ceria, or any composite oxides thereof.

Description

[Technical Field]

[0001] The present invention relates to a catalyzed particulate filter for treating exhaust from a gasoline engine, the filter comprising an in-wall TWC coating and, optionally, an on-wall layer of inorganic particles. The present invention also relates to an exhaust treatment system for a gasoline engine comprising the catalyzed particulate filter, and to a method for treating exhaust from a gasoline engine. [Background technology]

[0002] Engine exhaust consists essentially of gaseous pollutants such as unburned hydrocarbons (HC), carbon monoxide (CO) and nitrogen oxides (NOx), as well as particles. For gasoline engines, three-way catalysts (hereinafter referred to interchangeably as TWC catalysts or TWC) for gaseous pollutants and filters for particles are well-known aftertreatment measures to ensure that exhaust gases meet regulations.

[0003] As is known in the art, particulates produced by gasoline engines, such as gasoline direct injection engines, tend to be finer and in smaller quantities than particulates produced by diesel lean-burn engines. This is due to the different combustion conditions of gasoline engines compared to diesel engines. Particulate filters (also known as gasoline particulate filters) for treating exhaust from gasoline engines have been developed over decades to effectively treat exhaust, and among them, catalyzed gasoline particulate filters that combine catalytic activity and filtering function have attracted great interest.

[0004] WO 2018 / 024547 A1 describes a catalyzed particulate filter that includes a three-way conversion (TWC) catalyst material that permeates the walls of the particulate filter. Coating the TWC catalyst material on or within the filter can create backpressure effects. To avoid excessive backpressure while still providing full three-way conversion functionality, a specific coating scheme was proposed in the patent application. The catalyzed particulate filter is required to have a porosity of the coated pores that is smaller than the porosity of the uncoated pores of the particulate filter.

[0005] WO 2017 / 109514 A1 describes a catalytic wall-flow monolith for use in an emissions treatment system, the monolith comprising a porous substrate and a TWC catalyst, the TWC catalyst being distributed substantially throughout the porous substrate, the TWC catalyst comprising: (i) alumina; (ii) one or more platinum group metals; and (iii) an oxygen storage component (OSC), the OSC comprising one or more mixed oxides including ceria or cerium, wherein the OSC to alumina weight ratio is between 65:35 and 85:15.

[0006] WO 2021 / 096841 A1 describes a particulate filter for treating exhaust gases from an internal combustion engine, comprising a functional material layer coated on an inlet side, an outlet side, or both sides of the particulate filter, the functional material layer comprising a first inorganic material comprising one or more of alumina, zirconia, ceria, silica, titania, and rare earth metal oxides other than ceria, and a second inorganic material comprising one or more of alumina, zirconia, ceria, silica, titania, magnesium oxide, zinc oxide, manganese oxide, silicate zeolite, and aluminosilicate zeolite. The particulate filter may further comprise a catalyst layer of a three-way conversion (TWC) catalyst composite containing palladium and rhodium.

[0007] Gaseous and particulate emissions from gasoline engines are subject to strict regulations, such as the "Limits and Measurement Methods for Emissions from Light-Duty Vehicles (CHINA 6)" (GB18352.6-2016, also known as China 6). China 6b targets a 50% reduction in THC and CO emissions and a 42% reduction in NOx emissions from China 5 levels. China 6b also incorporates particulate matter (PM) regulations and adopts on-board diagnostic (OBD) requirements. Furthermore, China 6b requires vehicles to be tested under the World Harmonized Light-Duty Vehicle Test Cycle (WLTC), which includes numerous rapid acceleration and long-term high-speed requirements. Given the global trend toward increasingly stringent emissions limits, automobile manufacturers (OEMs) are demanding that catalyzed gasoline particulate filters have high catalytic activity at low backpressure, while also demonstrating desirable fresh filtration effects.

[0008] There is a need to provide a catalyzed particulate filter for treating exhaust from a gasoline engine that can exhibit improved catalytic activity and desirable fresh filtration efficiency at low back pressures. Summary of the Invention

[0009] It is an object of the present invention to provide a catalyzed particulate filter for treating exhaust from a gasoline engine that performs well with respect to at least one, and preferably all, of catalytic activity, back pressure, and fresh filtration efficiency.

[0010] Surprisingly, it has been found that the objects of the present invention are achieved by a particulate filter comprising an in-wall TWC coating and, optionally, an on-wall layer of inorganic particles.

[0011] Accordingly, in a first aspect, the present invention provides a particulate filter comprising: - a substrate including a plurality of porous walls extending longitudinally to form a plurality of parallel flow paths extending from an inlet end to an outlet end, wherein a quantity of the flow paths are inlet flow paths that are open at the inlet end and closed at the outlet end, and a quantity of the flow paths are outlet flow paths that are closed at the inlet end and open at the outlet end; - an in-wall ternary conversion (TWC) coating in the inlet and outlet flow passages, the in-wall TWC coating comprising a platinum group metal component, an alumina-based refractory metal oxide, and an oxygen storage component (OSC), the in-wall TWC coating having a weight ratio of the alumina-based refractory metal oxide to the oxygen storage component in the range of 1:20 to 1:3, the in-wall TWC coating being free of any individual zirconium and barium species; optionally, an on-wall layer of inorganic particles in the inlet and / or outlet flow paths, the inorganic particles comprising one or more non-PGM components selected from alumina, zirconia, ceria, silica, titania, magnesium oxide, manganese oxide, zinc oxide, rare earth metal oxides other than ceria, or any composite oxides thereof.

[0012] In some embodiments according to the first aspect, the particulate filter does not include an on-wall layer of inorganic particles. In some other embodiments according to the first aspect, the particulate filter includes an on-wall layer of inorganic particles.

[0013] In a second aspect, the present invention provides a method for manufacturing a particulate filter as described herein, comprising: (1) providing a slurry comprising mixing a platinum group metal component or precursor thereof, an alumina-based refractory metal oxide, and an oxygen storage component in a solvent, wherein no platinum group metal is pre-immobilized on the alumina-based refractory metal oxide and the oxygen storage component prior to mixing; and applying the slurry to inlet and outlet channels of a substrate to form an in-wall TWC coating; (2) optionally applying inorganic particles onto the surfaces of the porous walls in the inlet and / or outlet channels of the substrate carrying the in-wall TWC coating.

[0014] In a third aspect, the present invention provides an exhaust treatment system comprising a particulate filter according to the first aspect, preferably obtainable from or obtained by a method according to the second aspect, and arranged downstream of a petrol engine.

[0015] In a fourth aspect, the present invention provides a method of treating exhaust from a gasoline engine, the method comprising contacting the exhaust with a particulate filter according to the first aspect, preferably obtainable from or obtained by a method according to the second aspect, or an exhaust treatment system according to the third aspect.

[0016] It has been found that particulate filters according to the present invention can provide improved catalytic performance and backpressure characteristics, as well as desirable fresh filtration efficiency, compared to their prior art counterparts. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a schematic view of an exemplary wall-flow substrate having an inlet end and an outlet end. [Figure 2] FIG. 1 is a schematic longitudinal cross-sectional view of an exemplary wall-flow substrate having a plurality of porous walls extending longitudinally from the inlet end to the outlet end of the substrate. [Figure 3] 1 is a schematic longitudinal cross-sectional view of an exemplary in-wall TWC coating configuration of a gasoline particulate filter according to the present invention. [Figure 4] 2 is a schematic longitudinal cross-sectional view of an exemplary in-wall TWC coating and on-wall layer of a gasoline particulate filter according to the present invention; DETAILED DESCRIPTION OF THE INVENTION

[0018] The present invention will be described in detail herein below. It should be understood that the present invention can be embodied in many different ways and should not be construed as limited to the embodiments set forth herein.

[0019] The singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. Terms such as "comprise," "comprising," and the like are used interchangeably with "contain," "containing," and the like, and are to be interpreted in an open, non-restrictive manner; that is, for example, additional components or elements may be present. The expression "consist of" or cognates may be encompassed by "comprise" or cognates.

[0020] As used herein, reference to "free" is intended to mean that the species referred to in the context is not intentionally added or used. However, it will be understood by those skilled in the art that trace amounts of the species may be present as impurities from ingredients intentionally used.

[0021] As used herein, the term "in-wall" in the context of a TWC coating is intended to mean a TWC coating having TWC components intentionally deposited within the pores of the porous walls of a substrate, although small amounts, e.g., less than 50 wt. %, preferably less than 30 wt. %, and more preferably less than 10 wt. %, of the TWC components may be found on the surfaces of the porous walls within the coated channels. The meaning of the term "in-wall" is known in the art, as described, for example, in WO 2017 / 109514(A).

[0022] As used herein, the term "on-wall" in the context of a layer of inorganic particles is intended to mean that the inorganic particles are supported on the surface of the porous walls of the substrate, but that a small amount, e.g., less than 50% by weight, preferably less than 30% by weight, more preferably less than 10% by weight, of the inorganic particles may penetrate into the pores of the porous in-wall.

[0023] As used herein, the term "layer" in the context of, for example, a layer of inorganic particles is intended to mean a thin, gas-permeable coating of inorganic particles on the surface of a porous wall of a substrate. The layer may be in the form of particles packed on the wall of the substrate, with gaps between them that allow gas to pass through.

[0024] "D 10 "," "D 50 " and "D 90 The terms " and " have their usual meanings, referring to the points in the cumulative particle size distribution where the cumulative volume from the small particle size side reaches 10%, 50%, and 90%, respectively. The particle size distribution is measured by using a laser diffraction particle size distribution analyzer.

[0025] As used herein, terms for platinum group metal components, such as "palladium component," "platinum component," and "rhodium component," are intended to describe the presence of the respective platinum group metal in any possible valence state, which may be, for example, the metal or metal oxide as a catalytically active form.

[0026] As used herein, g / ft 3 or g / in 3 Any reference to loading in units of is intended to mean the weight of a particular component, coat, or layer per unit volume of the substrate on which it is carried.

[0027] According to a first aspect of the present invention, there is provided a particulate filter comprising: - a substrate including a plurality of porous walls extending longitudinally to form a plurality of parallel flow paths extending from an inlet end to an outlet end, wherein a quantity of the flow paths are inlet flow paths that are open at the inlet end and closed at the outlet end, and a quantity of the flow paths are outlet flow paths that are closed at the inlet end and open at the outlet end; - an in-wall ternary conversion (TWC) coating in the inlet and outlet flow passages, the in-wall TWC coating comprising a platinum group metal component, an alumina-based refractory metal oxide, and an oxygen storage component (OSC), the in-wall TWC coating having a weight ratio of the alumina-based refractory metal oxide to the oxygen storage component in the range of 1:20 to 1:3, the in-wall TWC coating being free of any individual zirconium and barium species; - optionally an on-wall layer of inorganic particles in the inlet and / or outlet channels, the inorganic particles comprising one or more non-PGM components selected from alumina, zirconia, ceria, silica, titania, magnesium oxide, manganese oxide, zinc oxide, rare earth metal oxides other than ceria, or any composite oxides thereof; A particulate filter is provided, comprising:

[0028] Substrate, as used herein, refers to a structure suitable for withstanding the conditions encountered in the exhaust stream from a combustion engine, which itself can function as a particulate filter, and onto which can be applied one or more functional coatings, for example, a catalytically active coating such as a TWC coating, an optional on-wall layer of inorganic particles as described herein, and any further coatings.

[0029] The substrate includes a plurality of longitudinally extending porous walls to form a plurality of parallel flow passages extending from an inlet end to an outlet end, with a volume of the flow passages being inlet flow passages that are open at the inlet end and closed at the outlet end, and a volume of the flow passages different from the inlet flow passages being outlet flow passages that are closed at the inlet end and open at the outlet end. The substrate configuration requires that engine exhaust flow through the porous walls in the inlet flow passages and into the outlet flow passages to reach the outlet end of the substrate, and is also referred to as a "wall-flow" substrate.

[0030] Generally, the substrate may have a honeycomb structure with alternating channels plugged at opposite ends.

[0031] The porous walls of the substrate are generally made from a ceramic or metallic material.

[0032] Suitable ceramic materials used to construct the substrate may include any suitable refractory material, such as cordierite, mullite, cordierite-alumina, silicon carbide, silicon nitride, zirconia, mullite, spodumene, alumina-silica-magnesia, zirconium silicate, magnesium silicate, sillimanite, petalite, alumina, aluminum titanate, and aluminosilicates. Typically, the porous walls of the substrate are made from cordierite or silicon carbide.

[0033] Suitable metallic materials for constructing the substrate 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 of nickel, chromium, and / or aluminum, and the total amount of these metals may advantageously comprise at least 15% by weight of the alloy, e.g., 10-25% by weight chromium, 3-8% by weight aluminum, and up to 20% by weight nickel. The alloy may also contain small or trace amounts of one or more metals, such as manganese, copper, vanadium, or titanium. The surface of the metal substrate may be oxidized, e.g., at high temperatures above 1000°C, to form an oxide layer on the surface of the substrate to improve the corrosion resistance of the alloy and promote adhesion of any coating layers to the metal surface.

[0034] The channels are plugged at their closed ends with a plug of sealant material. Any suitable sealant material may be used without any restriction.

[0035] The channels in the substrate can be of any suitable cross-sectional shape and size, such as circular, elliptical, sinusoidal, triangular, rectangular, square, hexagonal, trapezoidal, or other polygonal. The substrate may have up to 700 channels (i.e., cells) per square inch of cross section. For example, the substrate may have 100 to 500 cells per square inch ("cpsi"), typically 200 to 400 cpsi. The walls of the substrate may have a variety of thicknesses, with typical ranges being 2 mils to 0.1 inches. Preferably, the substrate has a number of inlet channels equal to the number of outlet channels, and the channels are uniformly distributed throughout the substrate.

[0036] Generally, the porous walls of the substrate may have an average pore size in the range of 10 to 30 microns (μm), for example, 13 to 25 μm or 15 to 21 μm.

[0037] 1 and 2 show a typical wall-flow substrate containing multiple inlet and outlet channels.

[0038] 1 shows a schematic view of a wall-flow substrate having an inlet end (01) where an exhaust stream (13) enters the substrate and an outlet end (02) where a treated exhaust stream (14) exits. Alternate flow channels are plugged to form a checkerboard pattern at the inlet end (01) as shown and an opposite checkerboard pattern at the outlet end (02), not shown.

[0039] Figure 2 shows a schematic longitudinal cross-section of a wall-flow substrate including a first plurality of flow channels (11) that are open at an inlet end (01) and closed at an outlet end (02), and a second plurality of flow channels (12) that are open at the outlet end (02) and closed at the inlet end (01). The flow channels are preferably parallel to one another to provide a consistent wall thickness between the flow channels. The exhaust stream (13) entering the first plurality of flow channels (11) from the inlet end must diffuse through the porous wall (10) into the second plurality of flow channels to exit the substrate as a process stream (14).

[0040] The in-wall TWC coating is present in both the inlet and outlet flow passages, which may also be referred to as an in-wall TWC coating in the inlet flow passage and an in-wall TWC coating in the outlet flow passage.

[0041] In some embodiments, the in-wall TWC coating in the inlet flow passage extends from the inlet end of the flow passage along 50% to 100% of the axial length of the inlet flow passage, and the in-wall TWC coating in the outlet flow passage extends from the outlet end of the flow passage along 50% to 100% of the axial length of the outlet flow passage.

[0042] Preferably, the in-wall TWC coating in the inlet flow passage and the in-wall TWC coating in the outlet flow passage each extend along 50% to 75%, more preferably 50% to 60%, and most preferably 50% to 55% of the axial length of the respective flow passage.

[0043] It will be appreciated that the in-wall TWC coating in the inlet flow channel and the in-wall TWC coating in the outlet flow channel may overlap each other in length. Figure 3 shows a schematic longitudinal cross-section of such an in-wall TWC coating configuration on a substrate as shown in Figures 1 and 2, where the in-wall TWC coating in the inlet flow channel (15) and the in-wall TWC coating in the outlet flow channel (16) extend with a length of overlap.

[0044] In some particular embodiments, the in-wall TWC coating in the inlet flow channel and the in-wall TWC coating in the outlet flow channel extend over their respective lengths with an overlap length of 10 mm or less.

[0045] Preferably, there is no layer of TWC components on the surface of the wall of the substrate, except optionally in the overlap region of the in-wall TWC coating in the inlet and outlet channels.

[0046] For the purposes of the present invention, the in-wall TWC coating in the inlet flow passage and the in-wall TWC coating in the outlet flow passage preferably have the same composition. More preferably, the in-wall TWC coating in the inlet flow passage and the in-wall TWC coating in the outlet flow passage are included in the particulate filter at the same or substantially the same loading. In this specification, the term "substantially the same loading" is intended to mean that the difference between the loading of the in-wall TWC coating in the inlet flow passage and the loading of the in-wall TWC coating in the outlet flow passage, calculated based on the lower of the two loadings, is less than 20%, in particular less than 10%, preferably less than 5%, more preferably 1%.

[0047] The platinum group metal (PGM) component contained in the in-wall TWC coating is not particularly limited. Typically, the PGM component may be platinum (Pt), palladium (Pd), rhodium (Rh), ruthenium (Ru), osmium (Os), iridium (Ir), or any combination thereof, with Pt, Pd, Rh, or any combination thereof being particularly useful.

[0048] In some embodiments, the in-wall TWC coating includes a combination of Rh, Pt, and optionally Pd as PGM components. In particular, the in-wall TWC coating includes a combination of Rh and Pt as PGM components.

[0049] In-wall TWC coatings range from 1.0 to 50.0 g / ft, calculated as each PGM element. 3 (i.e., approximately 0.04 to 1.8 g / L), or 5.0 to 20.0 g / ft 3 (i.e., about 0.18-0.71 g / L) total loading of PGM components.

[0050] Preferably, the Rh component is present in the in-wall TWC coating in an amount of 5% to 70%, preferably 10% to 60%, more preferably 20% to 50% based on the total loading of the PGM components.

[0051] As used herein, the term "alumina-based refractory metal oxide" refers to an oxide material comprising optionally doped alumina, and includes pure alumina and doped aluminas.

[0052] Suitable examples of alumina-based refractory metal oxides include, but are not limited to, high surface area aluminas, such as gamma alumina or mixtures of gamma and delta phases of alumina which may also contain significant amounts of eta, kappa, and theta alumina phases, doped aluminas, such as lanthana-doped alumina, baria-doped alumina, ceria-doped alumina, zirconia-doped alumina, ceria-zirconia-doped alumina, lanthana-zirconia-doped alumina, baria-lanthana-doped alumina, baria-lanthana-neodymia-doped alumina, and any combination thereof.

[0053] In some embodiments, the alumina-based refractory metal oxide in the in-wall TWC coating is selected from alumina, lanthana-doped alumina, lanthana-zirconia-doped alumina, ceria-doped alumina, zirconia-doped alumina, ceria-zirconia-doped alumina, or any combination thereof, more preferably alumina, lanthana-doped alumina, or a combination thereof.

[0054] As is well known, an oxygen storage composition (OSC) refers to an entity that has multiple valence states and can actively react with an oxidizing agent, such as oxygen or nitrogen oxides, under oxidizing conditions, or with a reducing agent, such as carbon monoxide (CO) or hydrogen, under reducing conditions. Typically, an OSC can be a reducible rare earth oxide, such as ceria, or a composite oxide of ceria with one or more of lanthana, praseodymia, neodymia, europia, samaria, ytterbia, yttria, zirconia, and hafnia, preferably a composite oxide of ceria with one or more of lanthana, praseodymia, neodymia, yttria, and zirconia. Preferably, the oxygen storage composition is selected from ceria-zirconia composite oxides and rare earth-stabilized ceria-zirconia composite oxides. It will be understood that the term "complex oxide" in the context of an OSC does not encompass a physical mixture of ceria with one or more other oxides.

[0055] In the in-wall TWC coating, the weight ratio of the alumina-based refractory metal oxide to the oxygen storage component is in the range of 1:20 to 1:3, preferably 1:15 to 1:4, more preferably 1:10 to 1:5, and most preferably 1:10 to 1:7, such as 1:9 and 1:8, or any ratio therebetween. Surprisingly, the inventors have found that a ratio of the alumina-based refractory metal oxide to the oxygen storage component in the in-wall TWC coating within the above range contributes to the excellent catalytic performance of the particulate filter of the present invention. Ratios less than 1:20 or greater than 1:3 result in a decreased catalytic performance of the particulate filter.

[0056] The present inventors have also surprisingly found that the absence of any individual zirconium and barium species in the in-wall TWC coating can contribute to the superior catalytic performance of the particulate filter of the present invention. As used herein, the individual zirconium and barium species refer to zirconium and barium species that exist as separate components, as can be determined by scanning electron microscope-energy dispersive spectroscopy (SEM-EDS) analysis. In other words, the in-wall TWC coating does not contain any zirconium or barium species other than those optionally contained in the alumina-based refractory metal oxide or oxygen storage component.

[0057] The zirconium species may be any zirconium compound, such as zirconium oxide, zirconium salts, or combinations thereof. The barium species may be any barium compound, such as barium oxide, barium salts, or combinations thereof.

[0058] In some exemplary embodiments, the in-wall TWC coating comprises a platinum group metal component, an alumina-based refractory metal oxide, and an oxygen storage component (OSC), wherein: the alumina-based noble metal oxide is selected from alumina, lanthana-doped alumina, lanthana-zirconia-doped alumina, ceria-doped alumina, zirconia-doped alumina, ceria-zirconia-doped alumina, or any combination thereof; the oxide storage component is selected from ceria or composite oxides of ceria and one or more of lanthana, praseodymia, neodymia, europia, samaria, ytterbia, yttria, zirconia, and hafnia; the weight ratio of the alumina-based refractory metal oxide to the oxygen storage component is in the range of 1:15 to 1:4; The in-wall TWC coating does not contain any individual zirconium or barium species.

[0059] In the above exemplary embodiment, the weight ratio of the alumina-based refractory metal oxide to the oxygen storage component is preferably in the range of 1:10 to 1:5, and more preferably in the range of 1:10 to 1:7. Additionally or alternatively, the alumina-based refractory metal oxide is preferably selected from alumina, lanthana-doped alumina, or a combination thereof, and the oxygen storage component is preferably selected from composite oxides of ceria and one or more of lanthana, praseodymia, neodymia, yttria, and zirconia.

[0060] In the above exemplary embodiment, the weight ratio of the alumina-based refractory metal oxide to the oxygen storage component is more preferably in the range of 1:10 to 1:5, the alumina-based refractory metal oxide is selected from alumina, lanthana-doped alumina, or a combination thereof, and the oxygen storage component is more preferably selected from composite oxides of ceria and one or more of lanthana, praseodymia, neodymia, yttria, and zirconia.

[0061] In the above exemplary embodiment, the weight ratio of the alumina-based refractory metal oxide to the oxygen storage component is most preferably in the range of 1:10 to 1:7, the alumina-based refractory metal oxide is selected from alumina, lanthana-doped alumina, or a combination thereof, and the oxygen storage component is selected from composite oxides of ceria and one or more of lanthana, praseodymia, neodymia, yttria, and zirconia.

[0062] The particulate filter of the present invention has a particle size of 0.1 to 5.0 g / in 3 (i.e., approximately 6.1 to 305.1 g / L), or 0.5 to 3.0 g / in 3 (i.e., approximately 30.5 to 183.1 g / L), or 0.8 to 2 g / in 3 (i.e., about 49-122 g / L) of in-wall TWC coating.

[0063] In-wall TWC coatings can be applied to a substrate by any known process, such as a conventional washcoating process, which involves coating a slurry of TWC components into the channels of the substrate. Washcoating slurries are typically prepared by pre-immobilizing the PGM components on support particles, such as alumina-based refractory metal oxides, by impregnation and / or heat treatment, followed by incorporation into a solvent. It was believed that pre-immobilization could prevent some of the deactivation of the PGM components that can be observed when the PGM components come into contact with alumina-based refractory metal oxides. However, the present inventors have surprisingly found that particulate filters including in-wall TWC coatings applied by washcoating a slurry prepared without pre-immobilizing the PGM components on a support (i.e., a one-pot process as described below) can provide significantly reduced exhaust emissions compared to particulate filters including in-wall TWC coatings applied by washcoating a slurry prepared with pre-immobilized PGM components.

[0064] The particulate filter according to the present invention may further comprise an on-wall layer of inorganic particles in the inlet and / or outlet flow paths, the inorganic particles comprising one or more non-PGM components selected from alumina, zirconia, ceria, silica, titania, magnesium oxide, manganese oxide, zinc oxide, rare earth metal oxides other than ceria, or any composite oxides thereof.

[0065] It will be appreciated that the on-wall layer of inorganic particles may be carried on the inlet channels only, the outlet channels only, or both the inlet and outlet channels. In particular, the on-wall layer of inorganic particles may be carried on the inlet channels only, or both the inlet and outlet channels, more preferably the inlet channels only.

[0066] In some embodiments, the inorganic particles comprise one or more non-PGM components selected from alumina, zirconia, ceria, silica, titania, rare earth metal oxides other than ceria, or any composite oxide thereof. More preferably, the inorganic particles comprise alumina.

[0067] The inorganic particles may optionally include PGM components, which, if present, may be supported on the non-PGM components as described above, or may be present separately from the non-PGM components.

[0068] As used herein, the on-wall layer of inorganic particles is preferably a layer that exhibits little or no TWC activity, preferably none at all, but may exhibit certain catalytic activity when one or more PGM components are included in the inorganic particles.

[0069] In some embodiments, the inorganic particles are free of PGM components, preferably consisting of particles of one or more of alumina, zirconia, ceria, silica, titania, magnesium oxide, manganese oxide, zinc oxide, rare earth metal oxides other than ceria, or composite oxides of any of these. More preferably, the inorganic particles consist of particles of one or more of alumina, zirconia, ceria, silica, titania, rare earth metal oxides other than ceria, or composite oxides of these, with alumina being most preferred.

[0070] Inorganic particles are D 90 Additionally or alternatively, the inorganic particles may have a particle size distribution in the range of 3 to 10 microns (μm), preferably 3 to 7 μm, represented by D 50 Additionally or alternatively, the inorganic particles may have a particle size distribution in the range of 1.8 to 6 microns (μm), preferably 1.8 to 4 μm, represented by D 10 The particle size distribution may be represented by:

[0071] In some embodiments, the inorganic particles have a D in the range of 0.5 to 1.5 μm. 10, D in the range of 1.8 to 6 μm 50 , and D in the range of 3 to 10 μm 90 Preferably, the inorganic particles have a particle size distribution characterized by D in the range of 0.8 to 1.2 μm. 10 , D in the range of 1.8 to 4 μm 50 , and D in the range of 3 to 7 μm 90 The particle size distribution is characterized by:

[0072] Particulate filter: 0.005 to 0.83 g / in 3 (i.e., about 0.3 to 50 g / L), or 0.01 to 0.33 g / in 3 (i.e., about 0.6 to 20 g / L), or 0.02 to 0.17 g / in 3 (i.e., about 1.2 to 10 g / L), or 0.025 to 0.13 g / in 3 (i.e., about 1.5-8 g / L) may include an on-wall layer of inorganic particles.

[0073] The on-wall layer of inorganic particles may be applied onto the surface of the porous walls of the substrate by any known process, such as dry coating as described below.

[0074] The on-wall layer of inorganic particles may be in the form of a particle bed and may extend along the porous walls of the flow channels in which the inorganic particles are carried. It will be understood that the particle bed may extend along the entire length of the porous walls of the flow channels or along only a portion of the length of the porous walls of the flow channels. Figure 4 shows schematically a longitudinal cross-section of a particulate filter comprising an on-wall layer of inorganic particles on a substrate already carrying an in-wall TWC coating as shown in Figure 3, where the on-wall layer of inorganic particles (17) in the inlet flow channel (11) extends the entire length of the porous walls of the flow channels.

[0075] The particulate filter may be housed within a shell having an inlet and an outlet for the exhaust flow, which may be operatively associated with and in fluid communication with other portions of the engine's exhaust system.

[0076] In a second aspect, the present invention provides a method of manufacturing a particulate filter according to the first aspect of the invention, the method comprising the steps of: (1) providing a slurry comprising mixing a platinum group metal component or precursor thereof, an alumina-based refractory metal oxide, and an oxygen storage component in a solvent, wherein no platinum group metal is pre-immobilized on the alumina-based refractory metal oxide and the oxygen storage component prior to mixing; and applying the slurry to inlet and outlet channels of a substrate to form an in-wall TWC coating; (2) optionally applying inorganic particles onto the surfaces of the porous walls in the inlet and / or outlet channels of the substrate bearing the in-wall TWC coating.

[0077] As used herein, the terms "pre-set" and "pre-set" within the context of platinum group metals (PGMs) are intended to refer to PGMs that have been deposited on a support, such as an alumina-based refractory metal oxide or an oxygen storage component, for example, by impregnation (e.g., incipient wetness impregnation) and / or heat treatment.

[0078] Generally, in step (1), the slurry can be provided by mixing a platinum-group metal component or its precursor, an alumina-based refractory metal oxide, and an oxygen storage component in a suitable solvent such as water, to which additives such as promoters, binders, stabilizers, viscosity modifiers, pH adjusters, surfactants, or any combination thereof can be added. Prior to mixing the platinum-group metal component or its precursor, the alumina-based refractory metal oxide, and the oxygen storage component, no platinum-group metal is pre-immobilized on the alumina-based refractory metal oxide and the oxygen storage component. Such a process for providing a slurry can also be referred to as a one-pot process.

[0079] In some specific embodiments of the method for manufacturing a particulate filter, the slurry may be provided by mixing the Pt component or its precursor with the oxygen storage component in a solvent, adding the alumina-based refractory metal oxide, and then adding the Rh component or its precursor. Alternatively, the slurry may be provided by mixing the Rh component or its precursor with the alumina-based refractory metal oxide in a solvent, adding the oxygen storage component, and then adding the Pt component or its precursor. In these embodiments, there are no particular restrictions on the timing of mixing the additives, if used.

[0080] Suitable precursors of platinum group components are, for example, soluble salts and / or complexes of platinum group metals, such as ammine complex salts, hydroxyl salts, nitrate salts, carboxylate salts and ammonium salts, as well as oxides and colloids of platinum group metals.

[0081] The components for providing the slurry may be used in conventional forms, such as powders, sols, or solutions or suspensions in a solvent, which may be the same as the slurry, particularly water. The slurry to be applied to the substrate may have a conventional solids content, such as 15 to 60% by weight.

[0082] It will be understood that if an additive is used in the slurry, the additive is not a zirconium- or barium-containing material. By avoiding the use of such zirconium- or barium-containing materials in the slurry, an in-wall TWC coating can be provided that is free of any individual zirconium and barium species, as described in the first aspect of the present invention.

[0083] If necessary, the slurry may be crushed / milled before being applied to the substrate to provide a particle size suitable for in-wall coating. For example, the slurry may be crushed / milled to a particle size of less than 10 microns (μm), e.g., 7 μm or less, preferably 5 μm or less. 90 Preferably, the slurry has a D of greater than 0.4 microns (μm), for example, 1 μm or greater, preferably 2 μm or greater. 90Crushing / grinding can be accomplished in any conventional equipment, such as a ball mill, a continuous Eiger mill, or the like.

[0084] The slurry generally has a pH of at least 2 and less than 9. If necessary, inorganic or organic acids and / or bases may be used as pH adjusters.

[0085] The slurry may be applied to the substrate by dipping the substrate into the slurry or by coating the substrate so that the desired coating loading is deposited on the substrate walls. If necessary, conventional means, such as air blowing or vacuum application, may be employed to remove excess slurry from the substrate, particularly any slurry remaining on the wall surfaces. The coated substrate may then be dried at a temperature in the range of 100-300°C and / or calcined at a temperature in the range of 350-650°C for a period of time, such as 1-3 hours. Drying and calcination are typically performed in air. The coating, drying, and calcination processes may be repeated as necessary to achieve the final desired gravimetric weight of the TWC coating on the substrate. The loading of the TWC coating can be determined by calculating the difference in weight between the substrate before coating and the coated substrate upon calcination.

[0086] It will be appreciated that any features of the in-wall TWC coating as generally or preferably described above for the particulate filter in the first aspect are now applicable to the method according to the second aspect.

[0087] The on-wall layer of inorganic particles may be applied to the surface of the porous walls of the substrate by any known process, such as a dry coating process. Dry coating processes are well known and are generally carried out by blowing inorganic particles or a suitable precursor thereof in particulate form into the channels of the substrate from the open end using a carrier gas flow, and optionally firing the coated substrate. With this process, no liquid carrier is used. The inorganic particles are typically distributed on the surface of the porous walls of the channels in the form of a particle bed.

[0088] In some embodiments, inorganic particles or suitable precursors thereof may be injected into the inlet channel from the open end of the channel toward the closed end. The particle bed formed in the inlet channel may be disposed on the porous wall of the inlet channel or against a plug blocking the channel. As noted above, the particulate bed, i.e., the on-wall layer of inorganic particles, is gas permeable, which can contribute to the capture of exhaust particulate matter (PM) and allow exhaust gaseous pollutants to pass therethrough.

[0089] Any features of the on-wall layer of inorganic particles described above as generally or preferred for the particulate filter in the first aspect are now applicable to the method according to the second aspect.

[0090] A particulate filter according to the first aspect or a particulate filter prepared by the method according to the second aspect is particularly suitable for treating exhaust from gasoline engines.

[0091] Thus, in a third aspect, the present invention provides an exhaust treatment system comprising a particulate filter according to the first aspect, preferably a particulate filter obtainable from or obtained by the method according to the second aspect, arranged downstream of a petrol engine.

[0092] In a fourth aspect, the present invention provides a method of treating exhaust from a gasoline engine, comprising contacting the exhaust with a particulate filter according to the first aspect, preferably obtainable from or obtained by a method according to the second aspect, or an exhaust treatment system according to the third aspect.

[0093] Embodiment Various embodiments are listed below, and it will be understood that the embodiments listed below can be combined with all aspects and other embodiments in accordance with the scope of the present invention.

[0094] 1. A particulate filter comprising: - a substrate including a plurality of porous walls extending longitudinally to form a plurality of parallel flow paths extending from an inlet end to an outlet end, wherein a quantity of the flow paths are inlet flow paths that are open at the inlet end and closed at the outlet end, and a quantity of the flow paths are outlet flow paths that are closed at the inlet end and open at the outlet end; - an in-wall TWC coating in the inlet and outlet flow passages comprising a platinum group metal component, an alumina-based refractory metal oxide, and an oxygen storage component, wherein the in-wall TWC coating has a weight ratio of the alumina-based refractory metal oxide to the oxygen storage component in the range of 1:20 to 1:3, and the in-wall TWC coating does not contain any individual zirconium or barium species; - optionally an on-wall layer of inorganic particles in the inlet and / or outlet flow paths, the inorganic particles comprising one or more non-PGM components selected from alumina, zirconia, ceria, silica, titania, magnesium oxide, manganese oxide, zinc oxide, rare earth metal oxides other than ceria, or any composite oxides thereof.

[0095] 2. A particulate filter as described in embodiment 1, comprising an on-wall layer of inorganic particles.

[0096] 3. The particulate filter according to embodiment 1 or 2, wherein the weight ratio of the alumina-based refractory metal oxide to the oxygen storage component is in the range of 1:15 to 1:4, more preferably 1:10 to 1:5, and most preferably 1:10 to 1:7.

[0097] 4. A particulate filter according to any one of embodiments 1 to 3, wherein the in-wall TWC coating in the inlet flow passage and the in-wall TWC coating in the outlet flow passage have the same composition.

[0098] 5. The particulate filter according to any one of embodiments 1 to 4, wherein the platinum group metal component is a Pt component, a Pd component, a Rh component, or any combination thereof.

[0099] 6. A particulate filter according to any one of embodiments 1 to 5, wherein the platinum group metal component is a combination of a Rh component, a Pt component, and optionally a Pd component.

[0100] 7. The particulate filter according to any one of embodiments 1 to 6, wherein the inorganic particles comprise one or more non-PGM components selected from alumina, zirconia, ceria, silica, titania, rare earth metal oxides other than ceria, or any composite oxides thereof.

[0101] 8. The particulate filter of embodiment 7, wherein the inorganic particles comprise alumina.

[0102] 9. The particulate filter of any one of embodiments 1 to 8, wherein the on-wall layer of inorganic particles is free of PGM components.

[0103] 10. Inorganic particles are in the range of 0.5 to 1.5 μm D 10 , D in the range of 1.8 to 6 μm 50 , and D in the range of 3 to 10 μm 90 , preferably in the range of 0.8 to 1.2 μm 10 , D in the range of 1.8 to 4 μm 50 , and D in the range of 3 to 7 μm 90 10. The particulate filter according to any one of embodiments 1 to 9, comprising:

[0104] 11. A method for manufacturing a particulate filter according to any one of embodiments 1 to 10, comprising: (1) providing a slurry comprising mixing a platinum group metal component or precursor thereof, an alumina-based refractory metal oxide, and an oxygen storage component in a solvent, wherein no platinum group metal is pre-immobilized on the alumina-based refractory metal oxide and the oxygen storage component prior to mixing; and applying the slurry to inlet and outlet channels of a substrate to form an in-wall TWC coating; (2) optionally applying inorganic particles onto the surfaces of the porous walls in the inlet and / or outlet channels of the substrate bearing the in-wall TWC coating.

[0105] 12. The method of embodiment 11, wherein the slurry in step (1) comprises an additive such as an accelerator, a binder, a stabilizer, a viscosity modifier, a pH adjuster, a surfactant, or any combination thereof.

[0106] 13. The method of embodiment 11 or 12, wherein the precursor of the platinum group metal component is selected from soluble salts, complexes, oxides, and colloids of platinum group metals.

[0107] 14. The method of any one of embodiments 11 to 13, wherein the slurry is provided by mixing the Pt component or a precursor thereof and the oxygen storage component in a solvent, to which an alumina-based refractory metal oxide and then the Rh component or a precursor thereof are added.

[0108] 15. The method of any one of embodiments 11 to 13, wherein the slurry is provided by mixing the Rh component or a precursor thereof with an alumina-based refractory metal oxide in a solvent, to which the oxygen storage component and then the Pt component or a precursor thereof are added.

[0109] 16. The method of any one of embodiments 11-15, wherein the inorganic particles are applied by a dry coating process.

[0110] 17. The method of any one of embodiments 11-16, wherein the inorganic particles are applied by using inorganic particles or precursors thereof.

[0111] 18. An exhaust treatment system comprising a particulate filter according to any one of embodiments 1 to 10, or obtainable or obtained by the method according to any one of embodiments 11 to 17, and arranged downstream of a gasoline engine.

[0112] 19. A method for treating exhaust from a gasoline engine, comprising contacting the exhaust with a particulate filter according to any one of embodiments 1 to 10, or a particulate filter obtainable from or obtained by the method according to any one of embodiments 11 to 17, or an exhaust treatment system according to embodiment 18. [Example]

[0113] Aspects of the present invention will be more fully described by the following examples, which are set forth to illustrate particular aspects of the invention and should not be construed as limiting thereof.

[0114] I. Preparation of Catalyzed Gasoline Particulate Filters Example 1 (E1, containing Ba / Zr, pre-fixed, alumina / OSC ratio is 0.37) Particulate filters with in-wall TWC coatings were prepared by applying the TWC washcoat slurry to both the inlet and outlet channels of a blank filter substrate (Corning® DuraTrap® GC). The blank filter substrate measured 118.4 mm (D) x 127 mm (L), with a volume of 1.4 L (approximately 85.4 in). 3 ) volume, a cell density of 300 cells per square inch (cpsi), and a wall thickness of 8 mils.

[0115] 23.93 g of a 16.39 wt % aqueous solution of hexahydroxyplatinic acid diethanolamine salt was mixed with 277 g of DI water and impregnated onto 693 g of La / Y-doped ceria-zirconia composite oxide (OSC, 40% ceria, 5% lanthana, 5% yttria, and the remainder zirconia) in a planetary mixer (P-mixer) to form a wet Pt / OSC powder while achieving incipient wetness. The wet Pt / OSC powder was mixed with 752 g of deionized water, 55 g of barium nitrate, and 39 g of a 21.6 wt % aqueous zirconium nitrate solution to form a Pt / OSC slurry. The pH of this slurry was adjusted to 3.5 with nitric acid, and the resulting slurry had a particle size D of 4.5 μm. 90 It was crushed to become.

[0116] 20.29 g of a 9.67 wt % rhodium nitrate aqueous solution was mixed with 179 g of DI water and impregnated into 256 g of gamma alumina powder in a planetary mixer (P-mixer) to achieve incipient wetness to form a wet Rh / alumina powder. The wet Rh / alumina powder was mixed with 160 g of deionized water, 23 g of barium nitrate, and 26 g of a 21.6 wt % zirconium nitrate aqueous solution to form a Rh / alumina slurry. The pH of this slurry was adjusted to 3.5 with nitric acid, and the slurry was mixed to a particle size D of 4.5 μm. 90 It was crushed to become.

[0117] The Pt / OSC and Rh / alumina slurries were combined into a final slurry and then coated onto the filter substrate at 50% of the target washcoat loading along 52% of the axial length of the filter from the inlet end, and at the remaining 50% of the target washcoat loading along up to approximately 52% of the axial length of the filter from the outlet end of the filter substrate. The coated substrate was then dried at 150°C for 1 hour and then calcined at 550°C for 1 hour.

[0118] 1.48g / in 3 Washcoat loading of 15.0 g / ft 3 and a Pt / Rh ratio of 10 / 5.

[0119] Example 2 (E2, containing Ba / Zr, pre-fixed, alumina / OSC ratio is 0.30) A particulate filter with an in-wall TWC coating was prepared from the same filter substrate as the blank filter of Example 1 by applying the TWC washcoat slurry to both the inlet and outlet channels of the blank filter.

[0120] 23.93 g of a 16.39 wt % aqueous solution of hexahydroxyplatinic acid diethanolamine salt was mixed with 292 g of DI water and impregnated onto 730 g of La / Y-doped ceria-zirconia composite oxide (OSC, 40% ceria, 5% lanthana, 5% yttria, and the remainder zirconia) in a planetary mixer (P-mixer) to form a wet Pt / OSC powder while achieving incipient wetness. The wet Pt / OSC powder was mixed with 792 g of deionized water, 55 g of barium nitrate, and 39 g of a 21.6 wt % aqueous zirconium nitrate solution to form a Pt / OSC slurry. The pH of this slurry was adjusted to 3.5 with nitric acid, and the resulting slurry was mixed to a particle size D of 4.5 μm. 90 It was crushed to become.

[0121] 20.29 g of a 9.67 wt % rhodium nitrate aqueous solution was mixed with 153 g of DI water and impregnated into 219 g of gamma alumina powder in a planetary mixer (P-mixer) to achieve incipient wetness to form a wet Rh / alumina powder. The wet Rh / alumina powder was mixed with 120 g of deionized water, 23 g of barium nitrate, and 26 g of a 21.6 wt % zirconium nitrate aqueous solution to form a Rh / alumina slurry. The pH of this slurry was adjusted to 3.5 with nitric acid, and the slurry was mixed to a particle size D of 4.5 μm. 90 It was crushed to become.

[0122] The Pt / OSC and Rh / alumina slurries were combined into a final slurry and then coated onto the filter substrate at 50% of the target washcoat loading along 52% of the axial length of the filter from the inlet end, and at the remaining 50% of the target washcoat loading along up to approximately 52% of the axial length of the filter from the outlet end of the filter substrate. The coated substrate was then dried at 150°C for 1 hour and then calcined at 550°C for 1 hour.

[0123] 1.48g / in 3 Washcoat loading of 15.0 g / ft 3 and a Pt / Rh ratio of 10 / 5.

[0124] Example 3 (E3, containing Ba / Zr, pre-fixed, alumina / OSC ratio is 0.20) A particulate filter with an in-wall TWC coating was prepared from the same filter substrate as the blank filter of Example 1 by applying the TWC washcoat slurry to both the inlet and outlet channels of the blank filter.

[0125] 23.93 g of a 16.39 wt % aqueous solution of hexahydroxyplatinic acid diethanolamine salt was mixed with 316 g of DI water and impregnated onto 791 g of La / Y-doped ceria-zirconia composite oxide (OSC, 40% ceria, 5% lanthana, 5% yttria, and the remainder zirconia) in a planetary mixer (P-mixer) to form a wet Pt / OSC powder while achieving incipient wetness. The wet Pt / OSC powder was mixed with 858 g of deionized water, 55 g of barium nitrate, and 39 g of a 21.6 wt % aqueous zirconium nitrate solution to form a Pt / OSC slurry. The pH of this slurry was adjusted to 3.5 with nitric acid, and the resulting slurry had a particle size D of 4.5 μm. 90 It was crushed to become.

[0126] 20.29 g of a 9.67 wt % rhodium nitrate aqueous solution was mixed with 111 g of DI water and impregnated into 158 g of gamma alumina powder in a planetary mixer (P-mixer) to achieve incipient wetness to form a wet Rh / alumina powder. The wet Rh / alumina powder was mixed with 99 g of deionized water, 23 g of barium nitrate, and 26 g of a 21.6 wt % zirconium nitrate aqueous solution to form a Rh / alumina slurry. The pH of this slurry was adjusted to 3.5 with nitric acid, and the slurry was mixed to a particle size D of 4.5 μm. 90 It was crushed to become.

[0127] The Pt / OSC and Rh / alumina slurries were combined into a final slurry and then coated onto the filter substrate at 50% of the target washcoat loading along 52% of the axial length of the filter from the inlet end, and at the remaining 50% of the target washcoat loading along up to approximately 52% of the axial length of the filter from the outlet end of the filter substrate. The coated substrate was then dried at 150°C for 1 hour and then calcined at 550°C for 1 hour.

[0128] 1.48g / in 3 Washcoat loading of 15.0 g / ft 3 and a Pt / Rh ratio of 10 / 5.

[0129] Example 4 (E4, containing Ba / Zr, pre-fixed, alumina / OSC ratio is 0.12) A particulate filter with an in-wall TWC coating was prepared from the same filter substrate as the blank filter of Example 1 by applying the TWC washcoat slurry to both the inlet and outlet channels of the blank filter.

[0130] 23.93 g of a 16.39 wt % aqueous solution of hexahydroxyplatinic acid diethanolamine salt was mixed with 338 g of DI water and impregnated onto 846 g of La / Y-doped ceria-zirconia composite oxide (OSC, 40% ceria, 5% lanthana, 5% yttria, and the remainder zirconia) in a planetary mixer (P-mixer) to form a wet Pt / OSC powder while achieving incipient wetness. The wet Pt / OSC powder was mixed with 912 g of deionized water, 55 g of barium nitrate, and 39 g of a 21.6 wt % aqueous zirconium nitrate solution to form a Pt / OSC slurry. The pH of this slurry was adjusted to 3.5 with nitric acid, and the resulting slurry was mixed to a particle size D of 4.5 μm. 90 It was crushed to become.

[0131] 20.29 g of a 9.67 wt % rhodium nitrate aqueous solution was mixed with 72 g of DI water and impregnated into 103 g of gamma alumina powder in a planetary mixer (P-mixer) to achieve incipient wetness to form a wet Rh / alumina powder. The wet Rh / alumina powder was mixed with 68 g of deionized water, 23 g of barium nitrate, and 26 g of a 21.6 wt % zirconium nitrate aqueous solution to form a Rh / alumina slurry. The pH of this slurry was adjusted to 3.5 with nitric acid, and the slurry was mixed to form a 4.5 μm particle size D 90 It was crushed to become.

[0132] The Pt / OSC and Rh / alumina slurries were combined into a final slurry and then coated onto the filter substrate at 50% of the target washcoat loading along 52% of the axial length of the filter from the inlet end, and at the remaining 50% of the target washcoat loading along up to approximately 52% of the axial length of the filter from the outlet end of the filter substrate. The coated substrate was then dried at 150°C for 1 hour and then calcined at 550°C for 1 hour.

[0133] 1.48g / in 3 Washcoat loading of 15.0 g / ft 3 and a Pt / Rh ratio of 10 / 5.

[0134] Example 5 (E5, containing Ba / Zr, pre-fixed, alumina / OSC ratio is 0.12) A particulate filter with an in-wall TWC coating was prepared from the same filter substrate as the blank filter of Example 1 by applying the TWC washcoat slurry to both the inlet and outlet channels of the blank filter.

[0135] 11.99 g of a 16.39 wt % aqueous solution of hexahydroxyplatinic acid diethanolamine salt was mixed with 338 g of DI water and impregnated onto 846 g of La / Y-doped ceria-zirconia composite oxide (OSC, 40% ceria, 5% lanthana, 5% yttria, and the remainder zirconia) in a planetary mixer (P-mixer) to form a wet Pt / OSC powder while achieving incipient wetness. The wet Pt / OSC powder was mixed with 912 g of deionized water, 55 g of barium nitrate, and 39 g of a 21.6 wt % aqueous zirconium nitrate solution to form a Pt / OSC slurry. The pH of this slurry was adjusted to 3.5 with nitric acid, and the resulting slurry had a particle size D of 4.5 μm. 90 It was crushed to become.

[0136] 20.33 g of a 9.67 wt % rhodium nitrate aqueous solution was mixed with 72 g of DI water and impregnated into 103 g of gamma alumina powder in a planetary mixer (P-mixer) to achieve incipient wetness to form a wet Rh / alumina powder. The wet Rh / alumina powder was mixed with 68 g of deionized water, 23 g of barium nitrate, and 26 g of a 21.6 wt % zirconium nitrate aqueous solution to form a Rh / alumina slurry. The pH of this slurry was adjusted to 3.5 with nitric acid, and the slurry was mixed to a particle size D of 4.5 μm. 90 It was crushed to become.

[0137] The Pt / OSC and Rh / alumina slurries were combined into a final slurry and then coated onto the filter substrate at 50% of the target washcoat loading along 52% of the axial length of the filter from the inlet end, and at the remaining 50% of the target washcoat loading along up to approximately 52% of the axial length of the filter from the outlet end of the filter substrate. The coated substrate was then dried at 150°C for 1 hour and then calcined at 550°C for 1 hour.

[0138] 1.48g / in 3 Washcoat loading of 10.0 g / ft 3 The in-wall TWC coating was obtained with a total PGM loading of 10 ...

[0139] Example 6 (E6, containing Ba / Zr, pre-fixed, alumina / OSC ratio is 0.05) A particulate filter with an in-wall TWC coating was prepared from the same filter substrate as the blank filter of Example 1 by applying the TWC washcoat slurry to both the inlet and outlet channels of the blank filter.

[0140] 11.99 g of a 16.39 wt % aqueous solution of hexahydroxyplatinic acid diethanolamine salt was mixed with 357 g of DI water and impregnated onto 892 g of La / Y-doped ceria-zirconia composite oxide (OSC, 40% ceria, 5% lanthana, 5% yttria, and the remainder zirconia) in a planetary mixer (P-mixer) to form a wet Pt / OSC powder while achieving incipient wetness. The wet Pt / OSC powder was mixed with 875 g of deionized water, 55 g of barium nitrate, and 39 g of a 21.6 wt % aqueous zirconium nitrate solution to form a Pt / OSC slurry. The pH of this slurry was adjusted to 3.5 with nitric acid, and the resulting slurry was mixed to a particle size D of 4.5 μm. 90 It was crushed to become.

[0141] 20.33 g of a 9.67 wt% aqueous rhodium nitrate solution was mixed with 32 g of DI water and impregnated into 45 g of gamma alumina powder in a planetary mixer (P-mixer) to achieve incipient wetness to form a wet Rh / alumina powder. The wet Rh / alumina powder was mixed with 22 g of deionized water, 23 g of barium nitrate, and 26 g of a 21.6 wt% aqueous zirconium nitrate solution to form a Rh / alumina slurry. The pH of this slurry was adjusted to 3.5 with nitric acid, and the slurry was mixed to form a 4.5 μm particle size D 90 It was crushed to become.

[0142] The Pt / OSC and Rh / alumina slurries were combined into a final slurry and then coated onto the filter substrate at 50% of the target washcoat loading along 52% of the axial length of the filter from the inlet end, and at the remaining 50% of the target washcoat loading along up to approximately 52% of the axial length of the filter from the outlet end of the filter substrate. The coated substrate was then dried at 150°C for 1 hour and then calcined at 550°C for 1 hour.

[0143] 1.48g / in 3 Washcoat loading of 10.0 g / ft 3 The in-wall TWC coating was obtained with a total PGM loading of 10 ...

[0144] Example 7 (E7, Ba / Zr-containing, pre-mounted, no alumina) A particulate filter with an in-wall TWC coating was prepared from the same filter substrate as the blank filter of Example 1 by applying the TWC washcoat slurry to both the inlet and outlet channels of the blank filter.

[0145] 11.99 g of a 16.39 wt % aqueous solution of hexahydroxyplatinic acid diethanolamine salt was mixed with 338 g of DI water and impregnated onto 846 g of La / Y-doped ceria-zirconia composite oxide (OSC, 40% ceria, 5% lanthana, 5% yttria, and the remainder zirconia) in a planetary mixer (P-mixer) to form a wet Pt / OSC powder while achieving incipient wetness. The wet Pt / OSC powder was mixed with 912 g of deionized water, 55 g of barium nitrate, and 39 g of a 21.6 wt % aqueous zirconium nitrate solution to form a Pt / OSC slurry. The pH of this slurry was adjusted to 3.5 with nitric acid, and the resulting slurry had a particle size D of 4.5 μm. 90 It was crushed to become.

[0146] 20.29 g of a 9.67 wt% rhodium nitrate solution was mixed with 41 g of deionized water and impregnated onto 103 g of La / Y-doped ceria-zirconia composite oxide (OSC, 40% ceria, 5% lanthana, 5% yttria, and the remainder zirconia) in a planetary mixer (P-mixer) to form a wet Rh / OSC powder while achieving incipient wetness. The wet Rh / OSC powder was mixed with 68 g of deionized water, 23 g of barium nitrate, and 26 g of a 21.6 wt% zirconium nitrate solution to form an Rh / OSC slurry. The pH of this slurry was adjusted to 3.5 with nitric acid, and the resulting slurry was mixed to a particle size D of 4.5 μm. 90 It was crushed to become.

[0147] The Pt / OSC and Rh / OSC slurries were combined into a final slurry and then coated onto the filter substrate at 50% of the target washcoat loading along 52% of the axial length of the filter from the inlet end, and at the remaining 50% of the target washcoat loading along up to approximately 52% of the axial length of the filter from the outlet end of the filter substrate. The coated substrate was then dried at 150°C for 1 hour and then calcined at 550°C for 1 hour.

[0148] 1.48g / in 3 Washcoat loading of 10.0 g / ft 3The in-wall TWC coating was obtained with a total PGM loading of 10 ...

[0149] Example 8 (E8, containing Zr, not containing Ba, pre-fixed, alumina / OSC ratio is 0.12) A particulate filter with an in-wall TWC coating was prepared from the same filter substrate as the blank filter of Example 1 by applying the TWC washcoat slurry to both the inlet and outlet channels of the blank filter.

[0150] 11.99 g of a 16.39 wt % aqueous solution of hexahydroxyplatinic acid diethanolamine salt was mixed with 338 g of DI water and impregnated onto 846 g of La / Y-doped ceria-zirconia composite oxide (OSC, 40% ceria, 5% lanthana, 5% yttria, and the remainder zirconia) in a planetary mixer (P-mixer) to form a wet Pt / OSC powder while achieving incipient wetness. The wet Pt / OSC powder was mixed with 912 g of deionized water and 39 g of a 21.6 wt % aqueous zirconium nitrate solution to form a Pt / OSC slurry. The pH of this slurry was adjusted to 3.5 with nitric acid, and the resulting slurry was mixed to a particle size D of 4.5 μm. 90 It was crushed to become.

[0151] 20.33 g of a 9.67 wt % rhodium nitrate aqueous solution was mixed with 72 g of DI water and impregnated into 103 g of gamma alumina powder in a planetary mixer (P-mixer) to achieve incipient wetness to form a wet Rh / alumina powder. The wet Rh / alumina powder was mixed with 68 g of deionized water and 26 g of a 21.6 wt % zirconium nitrate aqueous solution to form a Rh / alumina slurry. The pH of this slurry was adjusted to 3.5 with nitric acid, and the slurry was mixed to form a 4.5 μm particle size D 90 It was crushed to become.

[0152] The Pt / OSC and Rh / alumina slurries were combined into a final slurry and then coated onto the filter substrate at 50% of the target washcoat loading along 52% of the axial length of the filter from the inlet end, and at the remaining 50% of the target washcoat loading along up to approximately 52% of the axial length of the filter from the outlet end of the filter substrate. The coated substrate was then dried at 150°C for 1 hour and then calcined at 550°C for 1 hour.

[0153] 1.48g / in 3 Washcoat loading of 10.0 g / ft 3 The in-wall TWC coating was obtained with a total PGM loading of 10 ...

[0154] Example 9 (E9, containing neither Ba nor Zr, pre-fixed, alumina / OSC ratio of 0.12) A particulate filter with an in-wall TWC coating was prepared from the same filter substrate as the blank filter of Example 1 by applying the TWC washcoat slurry to both the inlet and outlet channels of the blank filter.

[0155] 11.99 g of a 16.39 wt % aqueous solution of hexahydroxyplatinic acid diethanolamine salt was mixed with 338 g of DI water and impregnated onto 846 g of La / Y-doped ceria-zirconia composite oxide (OSC, 40% ceria, 5% lanthana, 5% yttria, and the remainder zirconia) in a planetary mixer (P-mixer) to form a wet Pt / OSC powder while achieving incipient wetness. The wet Pt / OSC powder was mixed with 912 g of deionized water to form a Pt / OSC slurry. The pH of this slurry was adjusted to 3.5 with nitric acid, and the resulting slurry was mixed to a particle size D of 4.5 μm. 90 It was crushed to become.

[0156] 20.33 g of a 9.67 wt% aqueous rhodium nitrate solution was mixed with 72 g of DI water and impregnated into 103 g of gamma alumina powder in a planetary mixer (P-mixer) to achieve incipient wetness to form a wet Rh / alumina powder. The wet Rh / alumina powder was mixed with 68 g of deionized water to form a Rh / alumina slurry. The pH of this slurry was adjusted to 3.5 with nitric acid, and a 4.5 μm particle size D 90 It was crushed to become.

[0157] The Pt / OSC and Rh / alumina slurries were combined into a final slurry and then coated onto the filter substrate at 50% of the target washcoat loading along 52% of the axial length of the filter from the inlet end, and at the remaining 50% of the target washcoat loading along up to approximately 52% of the axial length of the filter from the outlet end of the filter substrate. The coated substrate was then dried at 150°C for 1 hour and then calcined at 550°C for 1 hour.

[0158] 1.48g / in 3 Washcoat loading of 10.0 g / ft 3 The in-wall TWC coating was obtained with a total PGM loading of 10 ...

[0159] Example 10 (E10, containing Ba / Zr, pre-fixed, alumina / OSC ratio is 0.12) A particulate filter with an in-wall TWC coating was prepared from the same filter substrate as the blank filter of Example 1 by applying the TWC washcoat slurry to both the inlet and outlet channels of the blank filter.

[0160] 26.80 g of a 16.39 wt % aqueous solution of hexahydroxyplatinic acid diethanolamine salt was mixed with 338 g of DI water and impregnated onto 846 g of La / Y-doped ceria-zirconia composite oxide (OSC, 40% ceria, 5% lanthana, 5% yttria, and the remainder zirconia) in a planetary mixer (P-mixer) to form a wet Pt / OSC powder while achieving incipient wetness. The wet Pt / OSC powder was mixed with 912 g of deionized water, 55 g of barium nitrate, and 39 g of a 21.6 wt % aqueous zirconium nitrate solution to form a Pt / OSC slurry. The pH of this slurry was adjusted to 3.5 with nitric acid, and the resulting slurry was mixed to a particle size D of 4.5 μm. 90 It was crushed to become.

[0161] 15.10 g of a 9.67 wt % rhodium nitrate aqueous solution was mixed with 72 g of DI water and impregnated into 103 g of gamma alumina powder in a planetary mixer (P-mixer) to achieve incipient wetness to form a wet Rh / alumina powder. The wet Rh / alumina powder was mixed with 68 g of deionized water, 23 g of barium nitrate, and 26 g of a 21.6 wt % zirconium nitrate aqueous solution to form a Rh / alumina slurry. The pH of this slurry was adjusted to 3.5 with nitric acid, and the slurry was mixed to a particle size D of 4.5 μm. 90 It was crushed to become.

[0162] The Pt / OSC and Rh / alumina slurries were combined into a final slurry and then coated onto the filter substrate at 50% of the target washcoat loading along 52% of the axial length of the filter from the inlet end, and at the remaining 50% of the target washcoat loading along up to approximately 52% of the axial length of the filter from the outlet end of the filter substrate. The coated substrate was then dried at 150°C for 1 hour and then calcined at 550°C for 1 hour.

[0163] 1.98g / in 3 Washcoat loading of 20.0 g / ft 3 The in-wall TWC coating was obtained with a total PGM loading of 10 ...

[0164] Example 11 (E11, containing Ba / Zr, one-pot, alumina / OSC ratio is 0.12) A particulate filter with an in-wall TWC coating was prepared from the same filter substrate as the blank filter of Example 1 by applying the TWC washcoat slurry to both the inlet and outlet channels of the blank filter.

[0165] 26.80 g of a 16.39 wt% aqueous solution of hexahydroxyplatinic acid diethanolamine salt was mixed with 1360 g of deionized water, and then 846 g of La / Y-doped ceria-zirconia composite oxide (OSC, 40% ceria, 5% lanthana, 5% yttria, and the remainder zirconia), 78 g of barium nitrate, 65 g of a 21.6 wt% aqueous solution of zirconium nitrate, 103 g of gamma-alumina powder, and 15.10 g of a 9.67 wt% aqueous solution of rhodium nitrate were added to form a slurry. The pH of this slurry was adjusted to 3.5 with nitric acid, and the resulting slurry had a particle size D of 4.5 μm. 90 It was crushed to become.

[0166] The slurry was then coated onto the filter substrate from the inlet end along 52% of the axial length of the filter at 50% of the target washcoat loading, and from the outlet end along up to approximately 52% of the axial length of the filter at the remaining 50% of the target washcoat loading. The coated substrate was then dried at 150°C for 1 hour and then calcined at 550°C for 1 hour.

[0167] 1.98g / in 3 Washcoat loading of 20.0 g / ft 3 The in-wall TWC coating was obtained with a total PGM loading of 10 ...

[0168] Example 12 (E12, containing Ba / Zr, pre-fixed, alumina / OSC ratio is 0.37) Particulate filters with in-wall TWC coatings were prepared by applying the TWC washcoat slurry to both the inlet and outlet channels of a blank filter substrate. The blank filter substrate had dimensions of 118.4 mm (D) x 127 mm (L), a volume of 1.4 L (approximately 85.4 in 3 ) volume, a cell density of 300 cells per square inch (cpsi), and a wall thickness of 8 mils.

[0169] 47.60 g of a 16.39 wt % aqueous solution of hexahydroxyplatinic acid diethanolamine salt was mixed with 277 g of DI water and impregnated onto 693 g of La / Y-doped ceria-zirconia composite oxide (OSC, 40% ceria, 5% lanthana, 5% yttria, and the remainder zirconia) in a planetary mixer (P-mixer) to achieve incipient wetness and form a wet Pt / OSC powder. The wet Pt / OSC powder was mixed with 752 g of deionized water, 55 g of barium nitrate, and 39 g of a 21.6 wt % aqueous zirconium nitrate solution to form a Pt / OSC slurry. The pH of this slurry was adjusted to 3.5 with nitric acid, and the resulting slurry had a particle size D of 4.5 μm. 90 It was crushed to become.

[0170] 40.30 g of a 9.67 wt% aqueous rhodium nitrate solution was mixed with 180 g of DI water and impregnated into 256 g of gamma alumina powder in a planetary mixer (P-mixer) to achieve incipient wetness to form a wet Rh / alumina powder. The wet Rh / alumina powder was mixed with 160 g of deionized water, 23 g of barium nitrate, and 26 g of a 21.6 wt% aqueous zirconium nitrate solution to form a Rh / alumina slurry. The pH of this slurry was adjusted to 3.5 with nitric acid, and the slurry was mixed to a particle size D of 4.5 μm. 90 It was crushed to become.

[0171] The Pt / OSC and Rh / alumina slurries were combined into a final slurry and then coated onto the filter substrate at 50% of the target washcoat loading along 52% of the axial length of the filter from the inlet end, and at the remaining 50% of the target washcoat loading along up to approximately 52% of the axial length of the filter from the outlet end of the filter substrate. The coated substrate was then dried at 150°C for 1 hour and then calcined at 550°C for 1 hour.

[0172] 1.48g / in 3 Washcoat loading of 30.0 g / ft 3 The in-wall TWC coating was obtained with a total PGM loading of 10 ...

[0173] Example 13 (E13, containing neither Ba nor Zr, one-pot, alumina / OSC ratio of 0.12) A particulate filter with an in-wall TWC coating was prepared from the same filter substrate as the blank filter of Example 1 by applying the TWC washcoat slurry to both the inlet and outlet channels of the blank filter.

[0174] 47.60 g of a 16.39 wt % aqueous solution of hexahydroxyplatinic acid diethanolamine salt was mixed with 1534 g of deionized water, and then 896 g of La / Y-doped ceria-zirconia composite oxide (OSC, 40% ceria, 5% lanthana, 5% yttria, and the remainder zirconia), 111 g of gamma alumina powder, and 40.30 g of a 9.67 wt % aqueous solution of rhodium nitrate were added to form a slurry. The pH of this slurry was adjusted to 3.5 with nitric acid, and the resulting slurry had a particle size D of 4.5 μm. 90 It was crushed to become.

[0175] The slurry was then coated onto the filter substrate from the inlet end along 52% of the axial length of the filter at 50% of the target washcoat loading, and from the outlet end along up to approximately 52% of the axial length of the filter at the remaining 50% of the target washcoat loading. The coated substrate was then dried at 150°C for 1 hour and then calcined at 550°C for 1 hour.

[0176] 1.48g / in 3 Washcoat loading of 30.0 g / ft 3 The in-wall TWC coating was obtained with a total PGM loading of 10 ...

[0177] Example 14 (E14, same as E12 with on-wall layer applied on the particulate filter) A particulate filter was fabricated with an in-wall TWC coating and an on-wall layer of alumina particles.

[0178] Alumina powder was mixed with a carrier gas and passed through the inlet passage of a particulate filter having an in-wall TWC coating obtained by the same process as described in Example 12 for 600 m at room temperature. 3 The alumina used had a flow rate of 150 m / s as measured by a Micromeritics ASAP2420 analyzer with a BET model under nitrogen adsorption at 77 K. 2 / g and a D of 1.03 μm as measured by a Sympatec HELOS laser diffraction particle size analyzer. 10 , 2.33 μm D 50 , and D of 4.31 μm 90 After coating, the filter with the on-wall layer of alumina particles in the inlet channels was fired at a temperature of 550°C for 1 hour. The loading of alumina particles was 3 g / L (0.05 g / in 3 ) was.

[0179] Example 15 (E15, same as E12 with on-wall layer applied on the particulate filter) Alumina particle loading of 5 g / L (0.082 g / in 3 A particulate filter having an in-wall TWC coating and an on-wall layer of alumina particles was prepared by the same process as described in Example 14, except that the in-wall TWC coating was 0.1% TWC.

[0180] Example 16 (E16, same as E13 with on-wall layer applied on the particulate filter) Alumina powder was injected into the inlet channels of a particulate filter having an in-wall TWC coating obtained by the same process as described in Example 13, with a loading of 5 g / L (0.082 g / in 3 A particulate filter having an in-wall TWC coating and an on-wall layer of alumina particles was prepared by the same process as described in Example 14, except that the in-wall TWC coating was 0.1% TWC.

[0181] Example 17 (E17, same as E13 with on-wall layer applied on the particulate filter) Alumina powder was injected into the inlet channels of a particulate filter having an in-wall TWC coating obtained by the same process as described in Example 13, with a loading of alumina particles of 7 g / L (0.115 g / in 3 A particulate filter having an in-wall TWC coating and an on-wall layer of alumina particles was prepared by the same process as described in Example 14, except that the in-wall TWC coating was 0.1% TWC.

[0182] II. Performance Evaluation II.1 Catalyst performance (oxygen storage capacity and catalytic activity) The particulate filters were examined for oxygen storage capacity and gas emissions. To evaluate the aged filters, fresh filters were exothermically aged in a GM 8.1L V8 engine at an inlet temperature of 875°C for 100 hours before testing. The steady-state oxygen storage capacity (SOSC) values ​​of each sample were measured in a closed-coupled position on a turbocharged Audi 2.0L engine at an inlet temperature of 580°C and a flow rate of 50 kg / h. Gas emissions measurements of each sample were performed in a closed-coupled position on a Daimler 2.0L engine under WLTC protocols, measuring THC, CO, and NOx emissions downstream of each sample. Lower emissions indicate higher catalytic activity of the filter. The SOSC and gas emissions results are shown in Tables 1-4.

[0183] [Table 1]

[0184] A comparison of E1 and E2-E4 shows that the catalyzed particulate filters with in-wall TWC coatings having alumina / OSC ratios of 0.12, 0.20, and 0.30 exhibit significantly higher SOSC values ​​and lower gas emissions (THC, CO, and NOx) than the catalyzed particulate filter with an in-wall TWC coating having an alumina / OSC ratio of 0.37.

[0185] Also, a comparison of E5 or E6 with E7 shows that the catalyzed particulate filters with in-wall TWC coatings having alumina / OSC ratios of 0.12 and 0.05 exhibit significantly higher SOSC values ​​and lower gas emissions (THC, CO, and NOx) than the catalyzed particulate filters with in-wall TWC coatings having an alumina / OSC ratio of 0, which is unexpected since the catalyzed particulate filters with in-wall TWC coatings having alumina / OSC ratios of 0.12 and 0.05 exhibit higher SOSC values ​​than their counterparts containing only oxygen storage components.

[0186] [Table 2]

[0187] Comparisons of E5 and E8 and E8 and E9 show that the absence of individual barium oxide or zirconium oxide in the in-wall TWC coating of a catalyzed particulate filter can result in improved oxygen storage capacity and catalytic activity. Furthermore, the absence of both individual barium oxide and zirconium oxide in the in-wall TWC coating can result in the highest SOSC values ​​and highest catalytic activity.

[0188] [Table 3]

[0189] Catalyzed particulate filter E10 was obtained from a slurry prepared via a conventional process involving pre-immobilization of PGMs on a support, and catalyzed particulate filter E11 was obtained from a slurry prepared via a one-pot process. Surprisingly, catalyzed particulate filter E11 exhibits a higher SOSC value and higher catalytic activity than catalyzed particulate filter E10.

[0190] [Table 4]

[0191] [Table 5]

[0192] A comparison between E12 and E13 shows that the catalyzed particulate filter with a low alumina / OSC ratio prepared using a slurry from a one-pot process in the absence of the individual barium and zirconium species exhibits significantly improved oxygen storage capacity and catalytic activity in both the fresh and aged states compared to the catalyzed particulate filter with a conventional alumina / OSC ratio prepared using a slurry from a conventional pre-loading process in the presence of the individual barium and zirconium species.

[0193] [Table 6]

[0194] As can be seen from the comparison between E14 and E16, the catalyzed particulate filter E16, which has an in-wall TWC coating with a low alumina / OSC ratio and is prepared using a slurry from a one-pot process in the absence of individual barium and zirconium species, exhibits significantly higher SOSC values ​​and lower gas emissions in both the fresh and aged states compared to the catalyzed particulate filter E14, which has a conventional alumina / OSC ratio and is prepared using a slurry from a conventional pre-loading process in the presence of individual barium and zirconium species. It is known that the loading of the on-wall layer of inorganic particles has little effect on the catalytic performance of a catalyzed particulate filter. Therefore, the catalyzed particulate filters E14 and E16 were measured to compare the catalytic performance of filters with the same backpressure.

[0195] II.2 Filtration performance (back pressure and fresh filtration efficiency) Particulate filter, 600m 3 The back pressure (BP) measured by a SuperFlow SF-1020 flow bench under a cold air flow of 1000 psi / h was investigated. The back pressure of a blank filter was also measured as a reference, which is 50 mbar.

[0196] 600m according to the standard procedure defined in "BS EN ISO 29463-5:2018-Part 5:Test method for filter elements" 3 The filtration efficiency of particulate filters in a fresh state (0 km, or unused state) was measured using di(2-ethylhexyl) sebacate aerosol as particles on a fixed air filter performance test bench with a cold airflow of 1000 / h. The particle number (PN) of particles in the range of 0.10-0.15 μm was recorded by a PN counter both upstream and downstream of the tested filter. The fresh filtration efficiency (FFE) was calculated according to the following formula:

[0197]

number

[0198] The test results for BP and FFE are summarized in Table 6 below.

[0199] [Table 7]

[0200] As can be seen from the comparison between E12 and E13, the catalyzed particulate filter E13 of the present invention provides a lower fresh filtration efficiency than the conventional catalyzed particulate filter E12. Surprisingly, the fresh filtration efficiency of E13 was significantly improved after an on-wall layer of alumina particles was applied to it (i.e., E16 and E17). The fresh filtration efficiency increased by 29% from E13 to E16, or 35% from E13 to E17. The improvement in fresh filtration efficiency when applying an on-wall layer of alumina particles on a catalyzed particulate filter with an in-wall TWC coating of the present invention is significantly higher than the improvement in fresh filtration efficiency when applying an on-wall layer of alumina particles on a catalyzed particulate filter with a conventional in-wall TWC coating.

[0201] It was also surprisingly found that the catalyzed particulate filters according to the present invention exhibited lower back pressure compared to conventional filters, as can be seen from the comparison of E12 with E13 and E15 with E16.

[0202] Although the invention herein has been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present invention. It will be apparent to those skilled in the art that various modifications and variations can be made to the method and apparatus of the present invention without departing from the spirit and scope of the invention. Therefore, it is intended that the present invention cover modifications and variations that come within the scope of the appended claims and their equivalents.

Claims

1. 1. A particulate filter comprising: a substrate including a plurality of longitudinally extending porous walls forming a plurality of parallel flow paths extending from an inlet end to an outlet end, a quantity of the flow paths being inlet flow paths that are open at the inlet end and closed at the outlet end, and a quantity of the flow paths being outlet flow paths that are closed at the inlet end and open at the outlet end; an in-wall TWC coating in the inlet and outlet flow passages comprising a platinum group metal component, an alumina-based refractory metal oxide, and an oxygen storage component, the in-wall TWC coating having a weight ratio of the alumina-based refractory metal oxide to the oxygen storage component in the range of 1:20 to 1:3, the in-wall TWC coating being free of any individual zirconium and barium species; - optionally an on-wall layer of inorganic particles in said inlet and / or outlet channels, said inorganic particles comprising one or more non-PGM components selected from alumina, zirconia, ceria, silica, titania, magnesium oxide, manganese oxide, zinc oxide, rare earth metal oxides other than ceria, or any composite oxides thereof; a particulate filter,

2. 10. The particulate filter of claim 1, comprising an on-wall layer of said inorganic particles.

3. 3. The particulate filter of claim 1 or 2, wherein the weight ratio of the alumina-based refractory metal oxide to the oxygen storage component is in the range of 1:15 to 1:4, more preferably 1:10 to 1:5, and most preferably 1:10 to 1:

7.

4. A particulate filter according to any one of claims 1 to 3, wherein the in-wall TWC coating in the inlet passage and the in-wall TWC coating in the outlet passage have the same composition.

5. The particulate filter according to any one of claims 1 to 4, wherein the platinum group metal component is a Pt component, a Pd component, a Rh component, or any combination thereof.

6. A particulate filter according to any one of claims 1 to 5, wherein the platinum group metal component is a combination of a Rh component, a Pt component, and optionally a Pd component.

7. The particulate filter according to any one of claims 1 to 6, wherein the inorganic particles contain one or more non-PGM components selected from alumina, zirconia, ceria, silica, titania, rare earth metal oxides other than ceria, or any composite oxides thereof.

8. 8. The particulate filter of claim 7, wherein the inorganic particles comprise alumina.

9. A particulate filter according to any one of the preceding claims, wherein the on-wall layer of inorganic particles is free of PGM components.

10. The inorganic particles have a D in the range of 0.5 to 1.5 μm. １０ , D in the range of 1.8 to 6 μm ５０ , and D in the range of 3 to 10 μm ９０ , preferably in the range of 0.8 to 1.2 μm １０ , D in the range of 1.8 to 4 μm ５０ , and D in the range of 3 to 7 μm ９０ A particulate filter according to any one of claims 1 to 9, having

11. A method for manufacturing a particulate filter according to any one of claims 1 to 10, comprising the steps of: (1) providing a slurry comprising mixing a platinum group metal component or precursor thereof, an alumina-based refractory metal oxide, and an oxygen storage component in a solvent, wherein no platinum group metal is pre-immobilized on the alumina-based refractory metal oxide and the oxygen storage component prior to said mixing; and applying the slurry to inlet and outlet flow channels of a substrate to form an in-wall TWC coating; (2) optionally applying inorganic particles onto the surfaces of the porous walls in the inlet and / or outlet channels of the substrate bearing the in-wall TWC coating; A method comprising:

12. 12. The method of claim 11, wherein the slurry in step (1) comprises additives such as accelerators, binders, stabilizers, viscosity modifiers, pH adjusters, surfactants, or any combination thereof.

13. 13. The method of claim 11 or 12, wherein the precursor of the platinum group metal component is selected from soluble salts, complexes, oxides, and colloids of the platinum group metal.

14. The method according to any one of claims 11 to 13, wherein the slurry is prepared by mixing a Pt component or a precursor thereof and an oxygen storage component in a solvent, to which an alumina-based refractory metal oxide and then a Rh component or a precursor thereof are added.

15. 14. The method according to claim 11, wherein the slurry is prepared by mixing an Rh component or a precursor thereof with an alumina-based refractory metal oxide in a solvent, to which an oxygen storage component and then a Pt component or a precursor thereof are added.

16. The method according to any one of claims 11 to 15, wherein the inorganic particles are applied by a dry coating process.

17. The method according to any one of claims 11 to 16, wherein the inorganic particles are applied by using the inorganic particles or precursors thereof.

18. An exhaust treatment system comprising a particulate filter according to any one of claims 1 to 10 or obtainable from or obtained by the method according to any one of claims 11 to 17, the exhaust treatment system being arranged downstream of a gasoline engine.

19. 19. A method of treating exhaust from a gasoline engine, the method comprising contacting the exhaust with a particulate filter according to any one of claims 1 to 10, or a particulate filter obtainable from or obtained by a method according to any one of claims 11 to 17, or an exhaust treatment system according to claim 18.

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