Catalyzed Particulate Filter

Abstract

The present invention relates to a 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 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 alumina-based refractory metal oxide to oxygen storage component in the range of 1:20 to 1:3, the in-wall TWC coating being free of any individual zirconium or barium species. The present invention also relates to an exhaust gas treatment system for a gasoline engine including the catalyzed particulate filter, and a method for treating exhaust gas from a gasoline engine.

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. The present invention also relates to an exhaust treatment system for a gasoline engine, the exhaust treatment system comprising the catalyzed particulate filter, and 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 2020 / 200394(A1) describes a particulate filter comprising a wall-flow filter of length L and two catalytically active coatings Y and Z, which extend parallel between a first end and a second end of the wall-flow filter, each having a surface O E and O A The particulate filter includes flow channels E and A separated by a porous wall forming a surface O, where flow channel E is closed at a second end and flow channel A is closed at a first end, and coatings Y and Z have the same oxygen storage component and the same precious metal support material. E and a coating Z is disposed within the upper flow channel E and extends from the first end of the wall-flow filter for 55-90% of the length L, the coating Z being disposed on the surface O. Aand coatings Y and Z are disposed within flow path A above the wall-flow filter and extend from the second end of the wall-flow filter for 55 to 90% of the length L, and are characterized in that coatings Y and Z contain aluminum oxide in an amount of 20 to 70% by weight based on the total weight of coating Y or Z and rhodium, palladium, or palladium and rhodium, and one or more oxygen storage components in an amount of 30 to 80% by weight based on the total weight of coating Y or Z.

[0007] WO 2020 / 200398 A1 describes a particulate filter for removing particles, carbon monoxide, hydrocarbons, and nitrogen oxides from the exhaust gases of a combustion engine operated with a stoichiometric air / fuel mixture, comprising a wall-flow filter of length L and two different coatings Y and Z, the wall-flow filter including flow passages E and A extending in parallel between a first end and a second end of the wall-flow filter and separated by a porous wall forming a surface OE or OA, flow passage E being closed at the second end and flow passage A being closed at the first end, the two coatings Y and Z being located on the porous wall and extending from the first end of the wall-flow filter over the entire length L, and both comprising activated alumina, at least one oxygen storage material, and at least one platinum group metal.

[0008] As gas and particulate emissions from gasoline engines are subject to stricter legal restrictions, such as Euro 6 and China 6 regulations, vehicle manufacturers, i.e., original equipment manufacturers (OEMs), are requiring catalyzed gasoline particulate filters to have high catalytic activity even under low backpressure.

[0009] It would be desirable to provide an improved catalyzed gasoline particulate filter that has higher catalytic activity and exhibits lower backpressure. Summary of the Invention

[0010] It is an object of the present invention to provide a catalyzed particulate filter for treating exhaust from a gasoline engine having improved catalytic performance.It is a further object of the present invention to provide a particulate filter for treating exhaust from a gasoline engine having improved catalytic performance and exhibiting lower back pressure.

[0011] Surprisingly, it has been found that the objects of the present invention are achieved by a particulate filter comprising an in-wall TWC coating containing a platinum group metal component, an alumina-based refractory metal oxide and an oxygen storage component (OSC) at a low alumina / OSC ratio, and free of individual zirconium and barium species.

[0012] Accordingly, in a first aspect, the present invention provides a particulate filter comprising: a substrate including a plurality of longitudinally extending porous walls forming a plurality of parallel flow channels extending from an inlet end to an outlet end, a volume of the flow channels being inlet flow channels that are open at the inlet end and closed at the outlet end, and a volume of the flow channels being outlet flow channels that are closed at the inlet end and open at the outlet end; and an in-wall ternary conversion (TWC) coating in 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 (OSC); the in-wall TWC coating has a weight ratio of alumina-based refractory metal oxide to oxygen storage component in the range of 1:20 to 1:3; The in-wall TWC coating provides a particulate filter that is free of any individual zirconium and barium species.

[0013] In a second aspect, the present invention provides a method for manufacturing a particulate filter as described herein, comprising: - 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 the mixing; applying the slurry to the inlet and outlet channels of the substrate; forming an 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 compared to their prior art counterparts. Furthermore, improved backpressure characteristics have been observed for gasoline particulate filters. [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. 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] 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 the catalytically active form.

[0023] 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.

[0024] According to a first aspect of the present invention, there is provided a particulate filter comprising: a substrate including a plurality of longitudinally extending porous walls forming a plurality of parallel flow channels extending from an inlet end to an outlet end, a volume of the flow channels being inlet flow channels that are open at the inlet end and closed at the outlet end, and a volume of the flow channels being outlet flow channels that are closed at the inlet end and open at the outlet end; and an in-wall ternary conversion (TWC) coating in 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 (OSC); the in-wall TWC coating has a weight ratio of alumina-based refractory metal oxide to oxygen storage component in the range of 1:20 to 1:3; The in-wall TWC coating provides a particulate filter that is free of any individual zirconium and barium species.

[0025] 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 on which one or more functional coatings can be applied, for example, a catalytically active coating such as a TWC coating as described herein, and any further coatings.

[0026] 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.

[0027] Generally, the substrate may have a honeycomb structure with alternating channels plugged at opposite ends.

[0028] The porous walls of the substrate are generally made from a ceramic or metallic material.

[0029] 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.

[0030] 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.

[0031] The channels are plugged at their closed ends with a plug of sealant material. Any suitable sealant material may be used without any restriction.

[0032] 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.

[0033] 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.

[0034] 1 and 2 show a typical wall-flow substrate containing multiple inlet and outlet channels.

[0035] 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.

[0036] 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).

[0037] 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.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] 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%.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] 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 selected from alumina, lanthana-doped alumina, or a combination thereof.

[0051] 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.

[0052] 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. If the ratio is less than 1:20 or more than 1:3, the catalytic performance of the particulate filter is reduced.

[0053] 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, 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.

[0054] 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.

[0055] In some exemplary embodiments, a particulate filter according to the present invention comprises: a substrate including a plurality of longitudinally extending porous walls forming a plurality of parallel flow channels extending from an inlet end to an outlet end, a volume of the flow channels being inlet flow channels that are open at the inlet end and closed at the outlet end, and a volume of the flow channels being outlet flow channels that are closed at the inlet end and open at the outlet end; and an in-wall ternary conversion (TWC) coating in 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 (OSC); 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; and 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 in-wall TWC coating has a weight ratio of alumina-based refractory metal oxide to oxygen storage component in the range of 1:15 to 1:4; The in-wall TWC coating does not contain any individual zirconium and barium species.

[0056] 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.

[0057] In some other exemplary embodiments, a particulate filter according to the present invention comprises: a substrate including a plurality of longitudinally extending porous walls forming a plurality of parallel flow channels extending from an inlet end to an outlet end, a volume of the flow channels being inlet flow channels that are open at the inlet end and closed at the outlet end, and a volume of the flow channels being outlet flow channels that are closed at the inlet end and open at the outlet end; and an in-wall ternary conversion (TWC) coating in 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 (OSC); 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; the in-wall TWC coating has a weight ratio of alumina-based refractory metal oxide to oxygen storage component in the range of 1:15 to 1:4; The in-wall TWC coating does not contain any individual zirconium or barium species.

[0058] Preferably, the particulate filter according to the invention comprises: a substrate including a plurality of longitudinally extending porous walls forming a plurality of parallel flow channels extending from an inlet end to an outlet end, a volume of the flow channels being inlet flow channels that are open at the inlet end and closed at the outlet end, and a volume of the flow channels being outlet flow channels that are closed at the inlet end and open at the outlet end; and an in-wall ternary conversion (TWC) coating in 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 (OSC); 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; the in-wall TWC coating has a weight ratio of alumina-based refractory metal oxide to oxygen storage component in the range of 1:10 to 1:5; The in-wall TWC coating does not contain any individual zirconium or barium species.

[0059] More preferably, the particulate filter according to the invention comprises: a substrate including a plurality of longitudinally extending porous walls forming a plurality of parallel flow channels extending from an inlet end to an outlet end, a volume of the flow channels being inlet flow channels that are open at the inlet end and closed at the outlet end, and a volume of the flow channels being outlet flow channels that are closed at the inlet end and open at the outlet end; and an in-wall ternary conversion (TWC) coating in 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 (OSC); 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; the in-wall TWC coating has a weight ratio of alumina-based refractory metal oxide to oxygen storage component in the range of 1:10 to 1:7; The in-wall TWC coating does not contain any individual zirconium or barium species.

[0060] 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.

[0061] 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.

[0062] In-wall TWC coatings can be applied to substrates 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 onto support particles, such as alumina-based refractory metal oxides, by impregnation and / or heat treatment, followed by incorporation into a solvent. Pre-immobilization was believed to 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.

[0063] However, it has surprisingly been found by the inventors that particulate filters including in-wall TWC coatings applied by washcoating a slurry prepared without pre-fixing the PGM components to a support can provide significantly reduced exhaust emissions compared to particulate filters including in-wall TWC coatings applied by washcoating a slurry prepared with pre-fixing the PGM components.

[0064] Accordingly, 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: - 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 the mixing; applying the slurry to the inlet and outlet channels of the substrate; forming an in-wall TWC coating.

[0065] 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.

[0066] Generally, 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.

[0067] 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.

[0068] 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.

[0069] 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.

[0070] 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.

[0071] 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.

[0072] 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.

[0073] 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.

[0074] 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.

[0075] 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.

[0076] 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.

[0077] 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.

[0078] 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.

[0079] Embodiment 1. A particulate filter comprising: a substrate including a plurality of longitudinally extending porous walls forming a plurality of parallel flow channels extending from an inlet end to an outlet end, a volume of the flow channels being inlet flow channels that are open at the inlet end and closed at the outlet end, and a volume of the flow channels being outlet flow channels that are closed at the inlet end and open at the outlet end; and an in-wall TWC coating in 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; the in-wall TWC coating has a weight ratio of alumina-based refractory metal oxide to oxygen storage component in the range of 1:20 to 1:3; The in-wall TWC coating does not contain any individual zirconium or barium species, particulate filter.

[0080] Embodiment 2. The particulate filter of embodiment 1, 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.

[0081] Embodiment 3. The particulate filter of embodiment 1 or 2, wherein the alumina-based refractory 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, more preferably selected from alumina, lanthana-doped alumina, or a combination thereof.

[0082] Embodiment 4. The particulate filter according to any one of embodiments 1 to 3, wherein the oxygen storage component is selected from ceria or composite oxides of ceria with one or more of lanthana, praseodymia, neodymia, europia, samaria, ytterbia, yttria, zirconia, and hafnia, preferably composite oxides of ceria with one or more of lanthana, praseodymia, neodymia, yttria, and zirconia.

[0083] Embodiment 5. A particulate filter as described in any one of embodiments 1 to 4, wherein 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.

[0084] Embodiment 6. A particulate filter as described in embodiment 5, wherein the in-wall TWC coating in the inlet flow passage and the in-wall TWC coating in the outlet flow passage 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.

[0085] Embodiment 7. A particulate filter according to any one of embodiments 1 to 6, 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.

[0086] Embodiment 8 The particulate filter according to any one of embodiments 1 to 7, wherein the platinum group metal component is a Pt component, a Pd component, a Rh component, or any combination thereof.

[0087] Embodiment 9. A particulate filter according to any one of embodiments 1 to 8, wherein the platinum group metal component is a combination of a Rh component, a Pt component, and optionally a Pd component.

[0088] Embodiment 10: A method for manufacturing a particulate filter according to any one of embodiments 1 to 9, comprising the steps of: - 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 the mixing; applying the slurry to the inlet and outlet channels of the substrate; forming an in-wall TWC coating.

[0089] Embodiment 11. The method of embodiment 10, wherein the slurry comprises an additive such as an accelerator, a binder, a stabilizer, a viscosity modifier, a pH adjuster, a surfactant, or any combination thereof.

[0090] Embodiment 12. The method of embodiment 10 or 11, wherein the precursor of the platinum group metal component is selected from soluble salts, complexes, oxides, and colloids of platinum group metals.

[0091] Embodiment 13. The method of any one of embodiments 10-12, comprising drying and firing the slurry after application.

[0092] Embodiment 14. The method of any one of embodiments 10-13, wherein the solvent is water.

[0093] Embodiment 15. The method of any one of embodiments 10-14, 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.

[0094] Embodiment 16. The method of any one of embodiments 10-14, wherein the slurry is provided by mixing the Rh component or a precursor thereof with the alumina-based refractory metal oxide in a solvent, to which the oxygen storage component is added, followed by the Pt component or a precursor thereof.

[0095] Embodiment 17. An exhaust treatment system comprising a particulate filter according to any one of embodiments 1 to 9, preferably obtainable by or obtained by the method according to any one of embodiments 10 to 16, and arranged downstream of a gasoline engine.

[0096] Embodiment 18. 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 9, preferably obtainable from or obtained by the method according to any one of embodiments 10 to 16, or with an exhaust treatment system according to embodiment 17. [Example]

[0097] 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.

[0098] 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.

[0099] 23.93 g of a 16.39 wt % aqueous solution of hexahydroxyplatinic acid diethanolamine salt was mixed with 277 g of deionized 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.

[0100] 20.29 g of a 9.67 wt % rhodium nitrate aqueous solution was mixed with 179 g of deionized 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 form a 4.5 μm particle size D 90 It was crushed to become.

[0101] 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.

[0102] 1.48g / in 3 Washcoat loading of 15.0 g / ft 3 and a Pt / Rh ratio of 10 / 5.

[0103] 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.

[0104] 23.93 g of a 16.39 wt % aqueous solution of hexahydroxyplatinic acid diethanolamine salt was mixed with 292 g of deionized 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 achieve incipient wetness and form a wet Pt / OSC powder. 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 had a particle size D of 4.5 μm. 90 It was crushed to become.

[0105] 20.29 g of a 9.67 wt % rhodium nitrate aqueous solution was mixed with 153 g of deionized 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 form a 4.5 μm particle size D 90 It was crushed to become.

[0106] 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.

[0107] 1.48g / in 3 Washcoat loading of 15.0 g / ft 3 and a Pt / Rh ratio of 10 / 5.

[0108] 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.

[0109] 23.93 g of a 16.39 wt % aqueous solution of hexahydroxyplatinic acid diethanolamine salt was mixed with 316 g of deionized 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 achieve incipient wetness and form a wet Pt / OSC powder. 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.

[0110] 20.29 g of a 9.67 wt % rhodium nitrate aqueous solution was mixed with 111 g of deionized 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 form a 4.5 μm particle size D 90 It was crushed to become.

[0111] 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.

[0112] 1.48g / in 3 Washcoat loading of 15.0 g / ft 3 and a Pt / Rh ratio of 10 / 5.

[0113] 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.

[0114] 23.93 g of a 16.39 wt % aqueous solution of hexahydroxyplatinic acid diethanolamine salt was mixed with 338 g of deionized 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.

[0115] 20.29 g of a 9.67 wt % rhodium nitrate aqueous solution was mixed with 72 g of deionized 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.

[0116] 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.

[0117] 1.48g / in 3 Washcoat loading of 15.0 g / ft 3 and a Pt / Rh ratio of 10 / 5.

[0118] 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.

[0119] 11.99 g of a 16.39 wt % aqueous solution of hexahydroxyplatinic acid diethanolamine salt was mixed with 338 g of deionized 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.

[0120] 20.33 g of a 9.67 wt % rhodium nitrate aqueous solution was mixed with 72 g of deionized 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.

[0121] 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.

[0122] 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 ...

[0123] 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.

[0124] 11.99 g of a 16.39 wt % aqueous solution of hexahydroxyplatinic acid diethanolamine salt was mixed with 357 g of deionized 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 had a particle size D of 4.5 μm. 90 It was crushed to become.

[0125] 20.33 g of a 9.67 wt% aqueous rhodium nitrate solution was mixed with 32 g of deionized 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.

[0126] 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.

[0127] 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 ...

[0128] 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.

[0129] 11.99 g of a 16.39 wt % aqueous solution of hexahydroxyplatinic acid diethanolamine salt was mixed with 338 g of deionized 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.

[0130] 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.

[0131] 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.

[0132] 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 ...

[0133] 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.

[0134] 11.99 g of a 16.39 wt % aqueous solution of hexahydroxyplatinic acid diethanolamine salt was mixed with 338 g of deionized 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 achieve incipient wetness and form a wet Pt / OSC powder. 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 had a particle size D of 4.5 μm. 90 It was crushed to become.

[0135] 20.33 g of a 9.67 wt % rhodium nitrate aqueous solution was mixed with 72 g of deionized water and impregnated into 103 g of gamma alumina powder in a planetary mixer (P-mixer) to form a wet Rh / alumina powder while achieving incipient wetness. 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 a particle size D of 4.5 μm. 90 It was crushed to become.

[0136] 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.

[0137] 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 ...

[0138] 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.

[0139] 11.99 g of a 16.39 wt % aqueous solution of hexahydroxyplatinic acid diethanolamine salt was mixed with 338 g of deionized 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 achieve incipient wetness and form a wet Pt / OSC powder. 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 a particle size D of 4.5 μm was obtained. 90 It was crushed to become.

[0140] 20.33 g of a 9.67 wt % rhodium nitrate aqueous solution was mixed with 72 g of deionized 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 particle size D of 4.5 μm was obtained. 90 It was crushed to become.

[0141] 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.

[0142] 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 ...

[0143] 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.

[0144] 26.80 g of a 16.39 wt % aqueous solution of hexahydroxyplatinic acid diethanolamine salt was mixed with 338 g of deionized 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.

[0145] 15.10 g of a 9.67 wt % rhodium nitrate aqueous solution was mixed with 72 g of deionized 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.

[0146] 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.

[0147] 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 ...

[0148] 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.

[0149] 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.

[0150] 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.

[0151] 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 ...

[0152] 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 measured 118.4 mm (D), 127 mm (L), and had 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.

[0153] 47.60 g of a 16.39 wt % aqueous solution of hexahydroxyplatinic acid diethanolamine salt was mixed with 277 g of deionized 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.

[0154] 40.30 g of a 9.67 wt % rhodium nitrate aqueous solution was mixed with 180 g of deionized 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.

[0155] 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.

[0156] 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 ...

[0157] Example 13 (E13, containing neither Ba nor Zr, pre-mounted, 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.

[0158] 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.

[0159] 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.

[0160] 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 ...

[0161] II. Performance Evaluation II.1 Oxygen storage capacity and catalytic activity Particulate filters E1 through E13 were examined for oxygen storage capacity and gas emissions. Prior to evaluation, samples were exothermally aged for 100 hours on a GM 8.1L V8 engine at an inlet temperature of 875°C. The same samples as E12 and E13 were also tested fresh without aging. The steady-state oxygen storage capacity (SOSC) values ​​of each sample were measured on a 2.0L turbocharged Audi engine in a closed-coupled position at an inlet temperature of 580°C and a flow rate of 50 kg / h. Gas emissions measurements of each sample were performed on a 2.0L Daimler engine in a closed-coupled position under WLTC protocols, measuring THC, CO, and NOx emissions downstream of each sample. Lower emissions indicate higher catalytic activity of the filter. The SOSC values ​​and gas emissions results are shown in Tables 1 through 4.

[0162] [Table 1]

[0163] 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.

[0164] 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 the oxygen storage component.

[0165] [Table 2]

[0166] 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.

[0167] [Table 3]

[0168] 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.

[0169] [Table 4]

[0170] [Table 5]

[0171] 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.

[0172] II.2 Backpressure increase caused by in-wall TWC coating Particulate filters E12 and E13, 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 substrate before coating was also measured under the same conditions. The increase in back pressure (ΔP) due to the in-wall TWC coating was calculated according to the following formula: ΔP = BP (coated) - BP (blank)

[0173] The results are shown in Table 5.

[0174] [Table 6]

[0175] The catalyzed particulate filter according to the present invention (E13) exhibits a much lower ΔP due to the in-wall TWC coating than the conventional catalyzed particulate filter (E12).

[0176] 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 to form a plurality of parallel flow channels extending from an inlet end to an outlet end, a volume of the flow channels being inlet flow channels that are open at the inlet end and closed at the outlet end, and a volume of the flow channels being outlet flow channels 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, the TWC coating comprising a platinum group metal component, an alumina-based refractory metal oxide, and an oxygen storage component; 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; A particulate filter, wherein said in-wall TWC coating does not contain any individual zirconium and barium species.

2. 2. The particulate filter of claim 1, wherein the weight ratio of said alumina-based refractory metal oxide to said 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.

3. 3. The particulate filter of claim 1 or 2, wherein the alumina-based refractory 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, more preferably selected from alumina, lanthana-doped alumina, or a combination thereof.

4. 4. A particulate filter according to any one of claims 1 to 3, wherein the oxygen storage component is selected from ceria or composite oxides of ceria with one or more of lanthana, praseodymia, neodymia, europia, samaria, ytterbia, yttria, zirconia and hafnia, preferably composite oxides of ceria with one or more of lanthana, praseodymia, neodymia, yttria and zirconia.

5. 5. A particulate filter according to claim 1, wherein 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.

6. 6. A particulate filter according to any one of claims 1 to 5, wherein the in-wall TWC coating in the inlet flow passage and the in-wall TWC coating in the outlet flow passage extend along 50% to 75%, more preferably 50% to 60%, most preferably 50% to 55% of the axial length of their respective flow passages.

7. A particulate filter according to any one of claims 1 to 6, wherein the in-wall TWC coating in the inlet passage and the in-wall TWC coating in the outlet passage have the same composition.

8. The particulate filter according to any one of claims 1 to 7, wherein the platinum group metal component is a Pt component, a Pd component, a Rh component, or any combination thereof.

9. A particulate filter according to any one of claims 1 to 8, wherein the platinum group metal component is a combination of a Rh component, a Pt component, and optionally a Pd component.

10. A method for manufacturing a particulate filter according to any one of claims 1 to 9, comprising the steps of: 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; - applying said slurry to the inlet and outlet channels of a substrate; forming an in-wall TWC coating.

11. The method of claim 10, wherein the slurry comprises additives such as accelerators, binders, stabilizers, viscosity modifiers, pH adjusters, surfactants, or any combination thereof.

12. 12. The method of claim 10 or 11, wherein the precursor of the platinum group metal component is selected from soluble salts, complexes, oxides, and colloids of the platinum group metal.

13. A method according to any one of claims 10 to 12, comprising drying and firing the slurry after application.

14. The method according to any one of claims 10 to 13, wherein the solvent is water.

15. The method according to any one of claims 10 to 14, 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.

16. 15. The method according to any one of claims 10 to 14, wherein the slurry is provided 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.

17. An exhaust treatment system comprising a particulate filter according to any one of claims 1 to 9, preferably obtainable from or obtained by the method according to any one of claims 10 to 16, and arranged downstream of a petrol engine.

18. 18. A method of treating exhaust from a gasoline engine, comprising contacting the exhaust with a particulate filter according to any one of claims 1 to 9, preferably obtainable from or obtained by a method according to any one of claims 10 to 16, or with an exhaust treatment system according to claim 17.

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