Catalytic particulate filter

Abstract

A particulate filter includes a substrate including a plurality of longitudinally extending porous walls to form a plurality of parallel channels extending from an inlet end to an outlet end, where a number of channels are inlet channels open at the inlet end and closed at the outlet end, and a number of channels are outlet channels closed at the inlet end and open at the outlet end; an in-wall TWC coating in the inlet channel and the outlet channel, the in-wall TWC coating comprising a platinum group metal component, an alumina-based refractory metal oxide, and an oxygen storage component wherein the weight ratio of the alumina-based refractory metal oxide to the oxygen storage component of the in-wall TWC coating is in the range of 1: 20 to 1: 3, and wherein the in-wall TWC coating does not contain any separate zirconium and barium species; and optionally, a layer of inorganic particles on the wall in the inlet channel and / or the outlet channel, the layer of inorganic particles on the wall comprising inorganic particles having a small BET pore volume of not greater than 0.5 cm3 / g. A gasoline engine emission treatment system including the particulate filter and a method for treating exhaust gas from a gasoline engine are also disclosed.

Description

Technical Field

[0001] The present invention relates to a catalytic particulate filter for treating exhaust gas from a gasoline engine, the catalytic particulate filter comprising an inner wall TWC coating and an optional outer wall inorganic particle layer. The present invention also relates to a gasoline engine emission treatment system comprising a catalytic particulate filter and a method for treating exhaust gas from a gasoline engine. Background Art

[0002] Engine exhaust gas is basically composed of gaseous pollutants (such as unburned hydrocarbons (HC), carbon monoxide (CO) and nitrogen oxides (NOx)) and particles. For gasoline engines, a three-way conversion catalyst (hereinafter interchangeably referred to as a TWC catalyst or TWC) for gaseous pollutants and a filter for particles are well-known post-treatment means to ensure that exhaust emissions comply with regulations.

[0003] As is known in the art, particles generated by gasoline engines (such as direct injection engines) tend to be finer and less numerous than particles generated by diesel lean-burn engines. This is because the combustion conditions of gasoline engines are different from those of diesel engines. Particle filters (also called gasoline particulate filters) for treating exhaust gas from gasoline engines have been developed for decades to effectively treat exhaust gas, and among these particulate filters, catalytic gasoline particulate filters having a combined catalytic activity and filtering function have attracted high interest.

[0004] WO 2018 / 024547A1 describes a catalytic particle filter comprising a three-way conversion (TWC) catalytic material that penetrates the particle filter wall. Coating the TWC catalytic material on or in the filter may result in back pressure effects. A special coating scheme is proposed in this patent application to avoid excessive increase in back pressure while providing full three-way conversion functionality. The coated porosity of the catalytic particle filter is required to be less than the uncoated porosity of the particle filter.

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

[0006] WO2021 / 096841A1 describes a particle filter for treating exhaust gas from an internal combustion engine, comprising a functional material layer coated on the inlet side, outlet side or both sides of the particle filter, wherein the functional material layer comprises: a first inorganic material, the first inorganic material comprising one or more of aluminum oxide, zirconium oxide, ceria, silicon dioxide, titanium dioxide, rare earth metal oxides other than ceria; and a second inorganic material, the second inorganic material comprising one or more of aluminum oxide, zirconium oxide, ceria, silicon dioxide, titanium dioxide, magnesium oxide, zinc oxide, manganese oxide, silicate zeolite, and aluminosilicate zeolite. The particle filter may further include a catalytic layer of a ternary conversion (TWC) catalyst composite containing palladium and rhodium.

[0007] Gaseous and particulate emissions from gasoline engines are subject to strict regulations, such as "Limits and measurement methods for emissions from light-duty vehicles (CHINA 6)" (GB18352.6-2016, also known as China Stage 6). The target of China Stage 6b is a 50% reduction in THC and CO emissions from China 5 levels, and a 42% reduction in NOx. In addition, China Stage 6b incorporates limits for particulate matter (PM) and adopts on-board diagnostic (OBD) requirements. In addition, according to China Stage 6b, vehicles should be tested under the World Harmonized Light-duty Vehicle Test Cycle (WLTC), which includes many sharp accelerations and extended high-speed requirements. In view of the global trend towards increasingly stringent emission limits, vehicle manufacturers, i.e. original equipment manufacturers (OEMs), require catalyzed gasoline particulate filters to have high catalytic activity at low back pressure, especially while exhibiting a desired fresh filtration efficiency.

[0008] There is a need to provide a catalyzed particulate filter for treating exhaust gas from a gasoline engine which may exhibit improved catalytic activity at low back pressures and preferably also exhibits improved fresh filter efficiency. Summary of the invention

[0009] An object of the present invention is to provide a catalyzed particulate filter for treating exhaust gas from a gasoline engine, which performs well in at least one, preferably all, of catalytic activity, back pressure and fresh filter efficiency.

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

[0011] Therefore, in a first aspect, the present invention provides a particle filter comprising

[0012] - a substrate comprising a plurality of longitudinally extending porous walls to form a plurality of parallel channels extending from an inlet end to an outlet end, wherein a number of the channels are inlet channels open at the inlet end and closed at the outlet end, and a number of the channels are outlet channels closed at the inlet end and open at the outlet end;

[0013] - an in-wall ternary conversion (TWC) coating in the inlet channel and the outlet channel, the in-wall ternary conversion coating comprising a platinum group metal component, an alumina-based refractory metal oxide and an oxygen storage component (OSC), wherein the weight ratio of the alumina-based refractory metal oxide to the oxygen storage component of the in-wall TWC coating is in the range of 1:20 to 1:3, and wherein the in-wall TWC coating does not contain any separate zirconium species and barium species; and

[0014] - Optionally, an inorganic particle layer on the wall of the inlet channel and / or the outlet channel, the inorganic particle layer on the wall comprising an inorganic particle having a particle size of not more than 0.5 cm 3 Inorganic particles with small BET pore volume of 1.1447 W / g.

[0015] In some embodiments according to the first aspect, the particle filter does not include a layer of inorganic particles on the wall. In some other embodiments according to the first aspect, the particle filter includes a layer of inorganic particles on the wall.

[0016] In a second aspect, the present invention provides a method for producing a particle filter as described herein, the method comprising the steps of:

[0017] (1) providing a slurry, comprising mixing a platinum group metal component or a precursor thereof, an alumina-based refractory metal oxide, and an oxygen storage component in a solvent, wherein the platinum group metal is not pre-fixed on the alumina-based refractory metal oxide and the oxygen storage component prior to the mixing; and applying the slurry to the inlet channel and the outlet channel of the substrate to form an in-wall TWC coating; and

[0018] (2) optionally, applying inorganic particles or their precursors on the surface of the porous walls in the inlet channel and / or outlet channel of the substrate bearing the in-wall TWC coating, and optionally drying and / or calcining to deposit an on-wall inorganic particle layer, the on-wall inorganic particle layer comprising an inorganic particle having a thickness of not greater than 0.5 cm 3 Inorganic particles with small BET pore volume of 1.1447 W / g.

[0019] In a third aspect, the invention provides an exhaust gas treatment system comprising a particle filter as described in the first aspect, preferably a particle filter obtainable from or obtainable by the method as described in the second aspect, the particle filter being located downstream of a gasoline engine.

[0020] In a fourth aspect, the present invention provides a method for treating exhaust gas from a gasoline engine, the method comprising contacting the exhaust gas with a particulate filter as described in the first aspect, preferably a particulate filter obtainable from or obtained by the method as described in the second aspect, or an exhaust gas treatment system as described in the third aspect.

[0021] It has been found that particulate filters according to the present invention can provide improved catalytic performance and backpressure characteristics as well as improved fresh filter efficiency compared to prior art counterparts. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 An exterior view of an exemplary wall flow substrate having an inlet end and an outlet end is schematically depicted.

[0023] Figure 2 A longitudinal cross-sectional view of an exemplary wall-flow substrate having a plurality of porous walls extending longitudinally from an inlet end to an outlet end of the substrate is schematically depicted.

[0024] Figure 3 A longitudinal cross-sectional view of an exemplary in-wall TWC coating configuration of a gasoline particulate filter according to the present invention is schematically depicted.

[0025] Figure 4 A longitudinal cross-sectional view of an exemplary in-wall TWC coating and an upper wall layer of a gasoline particulate filter according to the present invention is schematically depicted. DETAILED DESCRIPTION

[0026] The present invention is described in detail below. It should be understood that the present invention can be embodied in many different ways and should not be construed as being limited to the embodiments set forth herein.

[0027] The singular forms "a", "an", and "the" include plural referents unless the context clearly dictates otherwise. The terms "comprising", "including", and the like are used interchangeably with "containing", and are to be interpreted in a non-limiting, open-ended manner. That is, for example, additional components or elements may be present. The expression "consisting of" or cognates may be encompassed by "comprising" or cognates.

[0028] In this context, reference to "free of" is intended to mean that the substances mentioned in its context are not intentionally added or used. However, it will be understood by those skilled in the art that trace amounts of substances may be present as impurities derived from those components intentionally used.

[0029] In this document, the term "intra-wall" in the context of a TWC coating is intended to mean a TWC coating in which the TWC component is intentionally loaded into the pores of the porous wall of the substrate, but a small amount, e.g., less than 50 wt%, preferably less than 30 wt%, more preferably less than 10 wt%, of the TWC component may be present on the surface of the porous wall in the coating channel. The meaning of the term "intra-wall" is known in the art, e.g., as described in WO2017 / 109514A.

[0030] In this document, the term "on the wall" in the context of the inorganic particle layer is intended to mean that the inorganic particles are intended to be loaded onto the surface of the porous wall of the substrate, but a small amount, e.g., less than 50 wt. %, preferably less than 30 wt. %, more preferably less than 10 wt. %, of the inorganic particles may penetrate into the pores within the porous wall.

[0031] In this article, the term "layer" in the context of an inorganic particle layer is intended to mean a thin, gas-permeable coating of inorganic particles on the porous wall surface of a substrate. The layer may be in the form of packed particles on the walls of the substrate with gaps therebetween to allow gas to permeate through.

[0032] The term "D 10 ”, “D 50 ” and “D 90 " have their usual meanings, namely, refer to the points at which the cumulative volume from the small particle diameter side reaches 10%, 50% and 90% in the cumulative particle size distribution. The particle size distribution is measured using a laser diffraction particle size distribution analyzer.

[0033] In this document, terms of platinum group metal components, such as "palladium component", "platinum component" and "rhodium component" are intended to describe the presence of the corresponding platinum group metal in any possible valence state, which may be, for example, the metal or metal oxide as a catalytically active form.

[0034] In this article, any reference to "g / ft 3” or g" / in 3 Any reference to loading in units of "is intended to mean the weight of a particular component, coating or layer per unit volume of the substrate that carries the particular component, coating or layer.

[0035] According to a first aspect of the present invention, there is provided a particle filter, the particle filter comprising:

[0036] - a substrate comprising a plurality of longitudinally extending porous walls to form a plurality of parallel channels extending from an inlet end to an outlet end, wherein a number of the channels are inlet channels open at the inlet end and closed at the outlet end, and a number of the channels are outlet channels closed at the inlet end and open at the outlet end;

[0037] - an in-wall ternary conversion (TWC) coating in the inlet channel and the outlet channel, the in-wall ternary conversion coating comprising a platinum group metal component, an alumina-based refractory metal oxide and an oxygen storage component (OSC), wherein the weight ratio of the alumina-based refractory metal oxide to the oxygen storage component of the in-wall TWC coating is in the range of 1:20 to 1:3, and wherein the in-wall TWC coating does not contain any separate zirconium species and barium species; and

[0038] - Optionally, an inorganic particle layer on the wall of the inlet channel and / or the outlet channel, the inorganic particle layer on the wall comprising an inorganic particle having a particle size of not more than 0.5 cm 3 Inorganic particles with small BET pore volume of 1.1447 W / g.

[0039] As used herein, a substrate refers to a structure suitable for withstanding the conditions encountered in the exhaust gas flow of an internal combustion engine and which can function alone as a particulate filter, on which structure one or more functional coatings, such as a catalytically active coating (such as a TWC coating), an optional wall inorganic particle layer as described herein, and any other coatings can be carried.

[0040] The substrate includes a plurality of longitudinally extending porous walls to form a plurality of parallel channels extending from an inlet end to an outlet end, wherein a number of the channels are inlet channels that are open at the inlet end and closed at the outlet end, and a number of the channels other than the inlet channels are outlet channels that are closed at the inlet end and open at the outlet end. The configuration of the substrate requires that the engine exhaust gas in the inlet channel flows through the porous walls into the outlet channel to the outlet end of the substrate, which is also referred to as a "wall flow" substrate.

[0041] Generally speaking, the substrate may have a honeycomb structure with alternating channels plugged with plugs at opposite ends.

[0042] The porous wall of the substrate is generally made of ceramic material or metal material.

[0043] Suitable ceramic materials that can be used to construct the substrate can include any suitable refractory material, such as cordierite, mullite, cordierite-alumina, silicon carbide, silicon nitride, zirconium oxide, mullite, spodumene, alumina-silicon dioxide-magnesia, zirconium silicate, magnesium silicate, sillimanite, petalite, alumina, aluminum titanate and aluminosilicate. Typically, the porous wall of the substrate is made of cordierite or silicon carbide.

[0044] Suitable metal materials that can be used to construct substrates can include heat-resistant metals and metal alloys, such as titanium and stainless steel and other alloys with iron as the basic or main component. Such alloys can contain one or more of nickel, chromium and / or aluminum, and the total amount of these metals can advantageously include at least 15% by weight of the alloy, such as 10% by weight to 25% by weight of chromium, 3% by weight to 8% by weight of aluminum and up to 20% by weight of nickel. The alloy may also contain a small amount or trace of one or more metals, such as manganese, copper, vanadium, titanium, etc. The surface of the metal substrate can be oxidized at high temperatures (e.g., 1000° C. or higher) to form an oxide layer on the surface of the substrate, thereby improving the corrosion resistance of the alloy and promoting the adhesion of any coating to the metal surface.

[0045] The channel is closed at the closed end with a plug of sealing material. Any suitable sealing material may be used without any particular limitation.

[0046] The channels of the substrate can have any suitable cross-sectional shape and size, such as circular, elliptical, sinusoidal, triangular, rectangular, square, hexagonal, trapezoidal or other polygonal shapes. The substrate can have up to 700 channels (i.e., holes) / square inch of cross section. For example, the substrate can have 100 holes / square inch to 500 holes / square inch ("cpsi"), typically with 200cpsi to 400cpsi. The walls of the substrate can have different thicknesses, with a typical range of 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 evenly distributed throughout the substrate.

[0047] Typically, the porous walls of the substrate may have an average pore size in the range of 10 to 30 micrometers (μm), for example 13 to 25 μm or 15 to 21 μm.

[0048] Figure 1 and Figure 2 A typical wall-flow substrate comprising a plurality of inlet channels and outlet channels is illustrated.

[0049] Figure 1 Schematically depicts an external view of a wall-flow substrate having an inlet end (01) from which an exhaust gas stream (13) enters the substrate and an outlet end (02) from which a treated exhaust gas stream (14) exits. Alternating channels are plugged with plungers to form a checkerboard pattern at the inlet end (01) shown and an opposing checkerboard pattern at the outlet end (02) not shown.

[0050] Figure 2A longitudinal cross-sectional view of a wall-flow substrate is schematically depicted, the wall-flow substrate comprising a first plurality of channels (11) opening at an inlet end (01) and closed at an outlet end (02) and a second plurality of channels (12) opening at the outlet end (02) and closed at the inlet end (01). The channels are preferably parallel to each other to form a constant wall thickness between the channels. The exhaust gas flow (13) entering the first plurality of channels (11) from the inlet end must diffuse through the porous wall (10) into the second plurality of channels to exit the substrate as a treated flow (14).

[0051] The in-wall TWC coating exists in both the inlet channel and the outlet channel, which may also be referred to as the in-wall TWC coating in the inlet channel and the in-wall TWC coating in the outlet channel.

[0052] In some embodiments, the in-wall TWC coating in the inlet channel extends from the inlet end of the channel along 50% to 100% of the axial length of the inlet channel; and the in-wall TWC coating in the outlet channel extends from the outlet end of the channel along 50% to 100% of the axial length of the outlet channel.

[0053] Preferably, the in-wall TWC coating in the inlet channel and the in-wall TWC coating in the outlet channel each extend along 50% to 75%, more preferably 50% to 60%, most preferably 50% to 55% of the axial length of the respective channel.

[0054] It should be understood that the inner wall TWC coating in the inlet channel and the inner wall TWC coating in the outlet channel may overlap each other in length. Figure 3 Schematically depicts the Figure 1 and Figure 2 A longitudinal cross-section of such an in-wall TWC coating configuration on a substrate is shown, wherein the in-wall TWC coating (15) in the inlet channel and the in-wall TWC coating (16) in the outlet channel extend with a certain overlapping length.

[0055] In some specific embodiments, the inner wall TWC coating in the inlet channel and the inner wall TWC coating in the outlet channel extend over respective lengths, with the overlap length not exceeding 10 mm.

[0056] Preferably, there are no layers of TWC components on the surface of the substrate wall, except for those optionally present in the overlapping regions of the TWC coating within the walls in the inlet and outlet channels.

[0057] For the purposes of the present invention, the wall-inside TWC coating in the inlet channel and the wall-inside TWC coating in the outlet channel preferably have the same composition. More preferably, the wall-inside TWC coating in the inlet channel and the wall-inside TWC coating in the outlet channel are contained in the particle filter at the same or substantially the same loading. In this context, the term "substantially the same loading" is intended to mean that the difference between the loading of the wall-inside TWC coating in the inlet channel and the loading of the wall-inside TWC coating in the outlet channel is less than 20%, in particular less than 10%, preferably less than 5%, more preferably 1%, as calculated based on the lower of the two loadings.

[0058] There is no particular limitation on the platinum group metal (PGM) component contained in the in-wall TWC coating. Generally, the PGM component may be a platinum (Pt) component, a palladium (Pd) component, a rhodium (Rh) component, a ruthenium (Ru) component, an osmium (Os) component, an iridium (Ir) component, or any combination thereof, wherein the Pt component, the Pd component, the Rh component, or any combination thereof is particularly useful.

[0059] In some embodiments, the in-wall TWC coating comprises a combination of a Rh component, a Pt component, and an optional Pd component as a PGM component. In particular, the in-wall TWC coating comprises a combination of a Rh component and a Pt component as a PGM component.

[0060] In-wall TWC coatings can contain a total loading of 1.0 g / ft 3 Up to 50.0g / ft 3 (i.e. about 0.04 g / L to 1.8 g / L) or 5.0 g / ft 3 Up to 20.0g / ft 3 (i.e., about 0.18 g / L to 0.71 g / L) of PGM components, calculated as the corresponding PGM elements.

[0061] Preferably, the Rh component is present in the intra-wall TWC coating in an amount of 5% to 70%, preferably 10% to 60%, more preferably 20% to 50%, relative to the total loading of the PGM component.

[0062] As used herein, the term "alumina-based refractory metal oxide" refers to an oxide material comprising optionally doped alumina, and encompasses alumina itself and doped alumina.

[0063] Suitable examples of alumina-based refractory metal oxides include, but are not limited to, high surface area aluminas such as gamma alumina or a mixture of gamma and delta aluminas which may also contain significant amounts of η, κ, and θ alumina phases; and doped aluminas such as lanthanum oxide doped aluminas, barium oxide doped aluminas, ceria doped aluminas, zirconia doped aluminas, ceria-zirconia doped aluminas, lanthanum oxide-zirconia doped aluminas, barium oxide-lanthanum oxide doped aluminas, barium oxide-lanthanum oxide-neodymium oxide doped aluminas, and any combination thereof.

[0064] In some embodiments, the alumina-based refractory metal oxide in the in-wall TWC coating is selected from alumina, lanthanum oxide-doped alumina, lanthanum oxide-doped alumina, ceria-doped alumina, zirconia-doped alumina, ceria-doped alumina, or any combination thereof, more preferably alumina, lanthanum oxide-doped alumina, or a combination thereof.

[0065] As is well known, an oxygen storage component (OSC) refers to an entity that has multiple valence states and can react actively with an oxidant (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, the OSC can be a reducible rare earth metal oxide such as ceria, or a composite oxide of ceria with one or more of lanthanum oxide, praseodymium oxide, neodymium oxide, europium oxide, samarium oxide, ytterbium oxide, yttrium oxide, zirconium oxide and hafnium oxide, preferably a composite oxide of ceria with one or more of lanthanum oxide, praseodymium oxide, neodymium oxide, yttrium oxide and zirconium oxide. Preferably, the oxygen storage component is selected from ceria, ceria-zirconia composite oxides and rare earth stabilized ceria-zirconia composite oxides. It should be understood that the term "composite oxide" in the context of OSC does not cover physical mixtures of ceria with one or more other oxides.

[0066] In the 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, most preferably 1:10 to 1:7, for example 1:9 and 1:8 or any ratio therebetween. The inventors have surprisingly found that the ratio of the alumina-based refractory metal oxide to the oxygen storage component in the wall TWC coating in the above range contributes to the excellent catalytic performance of the particle filter according to the present invention. If the ratio is lower than 1:20 or higher than 1:3, the catalytic performance of the particle filter will deteriorate.

[0067] The inventors have also surprisingly found that the absence of any separate zirconium species and barium species in the in-wall TWC coating can contribute to the excellent catalytic performance of the particulate filter according to the present invention. In this context, separate zirconium species and barium species refer to zirconium species and barium species that are present as separate components, as can be determined by scanning electron microscope-energy dispersive spectrometer (SEM-EDS) analysis. In other words, the in-wall TWC coating does not contain any zirconium species and barium species, except for those optionally contained in the alumina-based refractory metal oxide or the oxygen storage component.

[0068] The zirconium material may be any zirconium compound, such as zirconium oxide, a zirconium salt, or a combination thereof. The barium material may be any barium compound, such as barium oxide, a barium salt, or a combination thereof.

[0069] 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

[0070] The alumina-based refractory metal oxide is selected from alumina, lanthanum oxide-doped alumina, lanthanum oxide-doped alumina, ceria-doped alumina, zirconia-doped alumina, ceria-doped zirconia alumina or any combination thereof, and the oxygen storage component is selected from ceria or a composite oxide of ceria with one or more of lanthanum oxide, praseodymium oxide, neodymium oxide, europium oxide, samarium oxide, ytterbium oxide, yttrium oxide, zirconium oxide and hafnium oxide,

[0071] 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, and

[0072] The in-wall TWC coating does not contain any separate zirconium and barium species.

[0073] In the above exemplary embodiments, it is preferred that the weight ratio of the alumina-based refractory metal oxide to the oxygen storage component is in the range of 1:10 to 1:5, more preferably 1:10 to 1:7. Additionally or alternatively, it is preferred that the alumina-based refractory metal oxide is selected from alumina, alumina doped with lanthanum oxide, or a combination thereof, and the oxygen storage component is selected from a composite oxide of ceria and one or more of lanthanum oxide, praseodymium oxide, neodymium oxide, yttrium oxide, and zirconium oxide.

[0074] In the above exemplary embodiments, it is more preferred that the weight ratio of the alumina-based refractory metal oxide to the oxygen storage component is in the range of 1:10 to 1:5, the alumina-based refractory metal oxide is selected from alumina, alumina doped with lanthanum oxide, or a combination thereof, and the oxygen storage component is selected from a composite oxide of cerium dioxide and one or more of lanthanum oxide, praseodymium oxide, neodymium oxide, yttrium oxide and zirconium oxide.

[0075] In the above exemplary embodiments, it is most preferred that the weight ratio of the alumina-based refractory metal oxide to the oxygen storage component is in the range of 1:10 to 1:7, the alumina-based refractory metal oxide is selected from alumina, alumina doped with lanthanum oxide, or a combination thereof, and the oxygen storage component is selected from a composite oxide of cerium dioxide and one or more of lanthanum oxide, praseodymium oxide, neodymium oxide, yttrium oxide, and zirconium oxide.

[0076] The particle filter according to the present invention may include a particle loading of 0.1 g / in 3 Up to 5.0g / in 3 (i.e. about 6.1 g / L to 305.1 g / L), or 0.5 g / in 3 Up to 3.0g / in 3 (i.e. about 30.5 g / L to 183.1 g / L), or 0.8 g / in 3 Up to 2g / in 3 (ie, about 49 g / L to 122 g / L) of TWC coating within the wall.

[0077] The in-wall TWC coating can be applied to the substrate by any known process, such as by a conventional washcoating process, which includes applying a slurry of the TWC component to the channels of the substrate. The PGM component is usually pre-fixed to the carrier particles such as a refractory metal oxide based on alumina by impregnation and / or heat treatment, and then formulated into a solvent for preparation. It is believed that pre-fixation can prevent certain deactivation of the PGM component, which can be observed when in contact with the refractory metal oxide based on alumina. However, the inventors surprisingly found that a particle filter comprising an in-wall TWC coating (applied by a washcoating slurry, which is prepared by pre-fixing the PGM component on the carrier) can provide significantly reduced exhaust emissions compared to a particle filter comprising an in-wall TWC coating (applied by a washcoating slurry, which is prepared by pre-fixing the PGM component on the carrier (i.e., a one-pot process as described below)).

[0078] The particle filter according to the present invention may further comprise an inorganic particle layer on the wall of the inlet channel and / or the outlet channel, wherein the inorganic particle layer on the wall comprises an inorganic particle having a particle size of not more than 0.5 cm 3 Inorganic particles with small BET pore volume of 1.1447 W / g.

[0079] It should be understood that the inorganic particle layer on the wall can be loaded in the inlet channel alone, loaded in the outlet channel alone, or loaded in both the inlet channel and the outlet channel. In particular, the inorganic particle layer on the wall can be loaded in the inlet channel alone or loaded in both the inlet channel and the outlet channel, more preferably loaded in the inlet channel alone.

[0080] Inorganic particles, especially those having a diameter not larger than 0.5 cm 3 Inorganic particles with a small BET pore volume of 100 g / g (also referred to herein as "inorganic particles with a small pore volume") may contain one or more non-PGM components. The non-PGM component may be, for example, alumina, hydrated alumina, boehmite, zirconia, ceria, rare earth metal oxides other than ceria, silica, titania, magnesia, manganese oxide, zinc oxide, zinc carbonate, calcium oxide, calcium carbonate, silicate zeolite, aluminosilicate zeolite, or any composite oxide thereof.

[0081] In some embodiments, the inorganic particles, in particular the inorganic particles with a small BET pore volume, comprise one or more non-PGM components selected from alumina, hydrated alumina, boehmite, zirconia, ceria, silica, titania, rare earth metal oxides other than ceria, or any composite oxide thereof. More preferably, the inorganic particles, in particular the inorganic particles with a small BET pore volume, comprise alumina, hydrated alumina, boehmite, or a combination thereof.

[0082] The inorganic particles may optionally include a PGM component. The PGM component, if present, may be supported on a non-PGM component as described above, or may be present separately from the non-PGM component.

[0083] Herein, the wall inorganic particle layer is preferably a layer showing little or no, preferably no TWC activity, but it may show some catalytic activity if one or more PGM components are included in the inorganic particles.

[0084] In some embodiments, the inorganic particles do not contain PGM components. Preferably, the inorganic particle layer on the wall can be mainly or substantially composed of inorganic particles with a small pore volume. More preferably, the inorganic particles with a small pore volume are composed of particles of alumina, hydrated alumina, boehmite or a combination thereof, most preferably boehmite particles.

[0085] As used herein, any reference to "consisting mainly of" in the context of an inorganic particle layer is intended to mean that the inorganic particle layer contains a major amount, i.e., greater than 50% by volume, of inorganic particles having a specified pore volume, which may be, for example, 75% by volume or more, 85% by volume or more, 90% by volume or more, or even 95% by volume or more.

[0086] In this document, any reference to "consisting essentially of" in the context of an inorganic particle layer is intended to mean that the inorganic particle layer contains an unintentionally added amount of inorganic particles other than inorganic particles having a specified small pore volume. In this document, the term "unintentionally added amount" is intended to mean no more than 1 volume %, no more than 0.5 volume %, no more than 0.1 volume %, or no more than 0.05 volume.

[0087] The present inventors have found that a pore volume having a small pore volume, i.e., a BET pore volume not greater than 0.5 cm 3 / g (as determined by nitrogen adsorption) of inorganic particles can have a favorable effect on the fresh filtration efficiency of the particle filter. For example, special mention may be made of small BET pore volumes of not more than 0.3 cm 3 / g or not more than 0.2cm 3 / g (as determined by nitrogen adsorption) of inorganic particles.

[0088] Inorganic particles, particularly those with a small pore volume, may have a pore volume of no greater than 100 m / s as determined by nitrogen adsorption. 2 / g, not more than 80m 2 / g or not more than 50m 2 / g of BET surface area.

[0089] In some embodiments, the inorganic particle layer on the wall comprises a small BET pore volume of no greater than 0.5 cm 3 / g and the BET surface area is not more than 100m 2 / g of inorganic particles.

[0090] In some other embodiments, the inorganic particle layer on the wall comprises a small BET pore volume of no greater than 0.3 cm 3 / g and the BET surface area is not more than 80m 2 / g of inorganic particles.

[0091] In some other embodiments, the inorganic particle layer on the wall comprises a small BET pore volume of no greater than 0.2 cm 3 / g and the BET surface area is not greater than 50m 2 / g of inorganic particles.

[0092] Inorganic particles, particularly those with a small pore volume, may have a D of no greater than 10 micrometers (μm), no greater than 6 μm, or no greater than 4 μm. 90 Inorganic particles, particularly those with a small pore volume, may have a D of no greater than 6 micrometers (μm), no greater than 4 μm, or no greater than 2 μm. 50 Inorganic particles, especially those with a small pore volume, may have a D of no greater than 3 μm or no greater than 1 μm. 10 .

[0093] In some embodiments, the inorganic particles, particularly those with a small pore volume, have a characteristic D 10 No more than 3μm, D 50 No more than 4μm and D 90 The particle size distribution is not greater than 6 μm. Preferably, the inorganic particles, especially the inorganic particles with a small pore volume, have a characteristic that D 10 No more than 1μm, D 50 No more than 2μm and D 90 Particle size distribution exceeding 4 μm.

[0094] The particle filter may include a loading of 0.005 g / in 3 Up to 0.83g / in 3 (i.e. about 0.3 g / L to 50 g / L), or 0.01 g / in 3 Up to 0.33g / in 3 (i.e. about 0.6 g / L to 20 g / L), or 0.02 g / in 3 Up to 0.17g / in 3 (i.e. about 1.2 g / L to 10 g / L), or 0.025 g / in 3 Up to 0.13g / in 3 (ie, about 1.5 g / L to 8 g / L) of inorganic particle layer on the wall.

[0095] The layer of inorganic particles on the wall may be applied to the surface of the porous wall of the substrate by any known process, such as dry coating as described below.

[0096] The inorganic particle layer on the wall may be in the form of a particle bed and extend along the porous wall of the channel loaded with inorganic particles. It should be understood that the particle bed may extend along the entire length of the porous wall of the channel, or only along a portion of the length of the porous wall of the channel. Figure 4 A longitudinal cross-sectional view of a particle filter is schematically depicted, the particle filter comprising a particle filter having been loaded with Figure 3 The layer of inorganic particles on the wall on the substrate of the in-wall TWC coating is shown, wherein the layer of inorganic particles on the wall (17) in the inlet channel (11) extends over the entire length of the porous wall of the channel.

[0097] The particulate filter may be housed within a housing having an inlet and an outlet for exhaust flow, which housing may be operatively associated with and in fluid communication with the rest of the engine's exhaust system.

[0098] In a second aspect, the present invention provides a method for producing a particle filter according to the first aspect of the present invention, the method comprising the steps of:

[0099] (1) providing a slurry comprising mixing a platinum group metal component or a precursor thereof, an alumina-based refractory metal oxide, and an oxygen storage component in a solvent, wherein the platinum group metal is not pre-fixed on the alumina-based refractory metal oxide and the oxygen storage component prior to mixing; and applying the slurry to the inlet channel and the outlet channel of the substrate to form an in-wall TWC coating; and

[0100] (2) optionally, applying inorganic particles or their precursors to the surface of the porous walls in the inlet channels and / or outlet channels of the substrate bearing the in-wall TWC coating, and optionally drying and / or

[0101] or calcined to deposit an inorganic particle layer on the wall, the inorganic particle layer on the wall comprising a particle size not greater than 0.5 cm 3 Inorganic particles with small BET pore volume of 1.1447 W / g.

[0102] As used herein, the terms "pre-fixed" and "pre-fixing" in the context of platinum group metals (PGMs) are intended to refer to PGMs that have been attached to 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.

[0103] Typically, in step (1), a slurry may be provided by mixing a platinum group metal component or a precursor thereof, 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 modifiers, surfactants, or any combination thereof may be added. Prior to mixing the platinum group metal component or a precursor thereof, the alumina-based refractory metal oxide, and the oxygen storage component, the platinum group metal is not pre-fixed on the alumina-based refractory metal oxide and the oxygen storage component. This method for providing a slurry may also be referred to as a one-pot process.

[0104] In some specific embodiments of the method for producing a particulate filter, a slurry may be provided 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 is added, and then an Rh component or a precursor thereof is added. Alternatively, a slurry may be 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 is added, and then a Pt component or a precursor thereof is added. In those embodiments, there is no particular limitation on the timing of mixing the additives (if used).

[0105] Suitable precursors of the platinum group metal component are, for example, soluble salts and / or complexes of platinum group metals, such as ammine complex salts, hydroxyl salts, nitrates, carboxylates and ammonium salts, oxides and colloids of platinum group metals.

[0106] The components used to provide the slurry can be used in conventional forms, such as powders, sols or solutions or suspensions in solvents. The solvent can be the same solvent as the solvent of the slurry, in particular water. The slurry applied to the substrate can have a conventional solids content, such as 15% to 60% by weight.

[0107] It should be understood that if an additive is used in the slurry, the additive will not be any zirconium-containing material or barium-containing material. By avoiding the use of such zirconium-containing materials or barium-containing materials in the slurry, an in-wall TWC coating without any separate zirconium and barium materials as described in the first aspect of the present invention can be provided.

[0108] If necessary, the slurry may be crushed / milled before application to the substrate to provide a suitable particle size for the wall coating. For example, the slurry may have a D of less than 10 micrometers (μm), such as 7 μm or less, preferably 5 μm or less. 90 Preferably, the slurry has a D greater than 0.4 micrometers (μm), for example 1 μm or greater, preferably 2 μm or greater. 90 The comminution / grinding can be accomplished in any conventional equipment, such as a ball mill, a continuous Eiger mill, and the like.

[0109] The slurry generally has a pH of 2 to less than 9. If necessary, an inorganic or organic acid and / or base may be used as a pH adjuster.

[0110] The slurry can be applied to the substrate by immersing the substrate in the slurry, or by coating it on the substrate in other ways, so that the desired loading amount of the coating will be deposited on the substrate wall. If necessary, conventional means such as blowing, applying vacuum, etc., can be used to remove excess slurry from the substrate (especially the slurry remaining on the wall surface). Thereafter, the coated substrate can be dried at a temperature in the range of 100°C to 300°C and / or calcined at a temperature in the range of 350°C to 650°C for a period of time, for example, 1 hour to 3 hours. Drying and calcining are usually carried out in air. If necessary, the coating process, drying process and calcining process can be repeated to achieve the final desired weight amount of the TWC coating on the substrate. The loading amount of the TWC coating can be determined by calculating the weight difference between the substrate before coating and the substrate coated after calcination.

[0111] It will be appreciated that any features generally or preferably described above for the in-wall TWC coating of the particle filter of the first aspect are applicable herein to the method according to the second aspect.

[0112] The inorganic particle layer on the wall can be applied to the surface of the porous wall of the substrate by any known process (such as dry coating process). The dry coating process is well known, and generally the inorganic particles in the form of particles or their suitable precursors are blown into the channel of the substrate from the open end by a carrier gas flow, and the substrate of the coating is optionally dried and / or calcined to carry out. By this process, liquid carrier will not be used. The inorganic particles are usually distributed on the surface of the porous wall of the channel in the form of a particle bed.

[0113] In some embodiments, inorganic particles or their suitable precursors can be blown into the inlet channel from the open end of the channel toward the closed end of the channel. The particle bed formed in the inlet channel can be located on the porous wall of the inlet channel, and is also opposite to the plunger blocking the channel. As described above, the particle bed (i.e., the inorganic particle layer) is breathable, which helps to capture particulate matter (PM) in the exhaust gas and allows gaseous pollutants in the exhaust gas to penetrate through.

[0114] Any features of the layer of inorganic particles on the wall of the particle filter described generally or preferably above for the first aspect are applicable here to the method according to the second aspect.

[0115] In some embodiments, greater than 50% by volume of the inorganic particles applied, such as 75% by volume or more, 85% by volume or more, 90% by volume or more, or even 95% by volume or more, are particles having a diameter not greater than 0.5 cm as specified herein. 3 Inorganic particles with a small BET pore volume of no more than 0.5 cm 3 / g of inorganic particles with a small BET pore volume.

[0116] The particle filter according to the first aspect or produced by the method according to the second aspect is particularly suitable for treating exhaust gases from gasoline engines.

[0117] Thus, in a third aspect, the invention provides an exhaust gas treatment system comprising a particle filter as described in the first aspect, preferably a particle filter obtainable or obtainable by the method as described in the second aspect, the particle filter being located downstream of a gasoline engine.

[0118] In a fourth aspect, the present invention provides a method for treating exhaust gas from a gasoline engine, the method comprising contacting the exhaust gas with a particulate filter as described in the first aspect, a particulate filter obtainable from or obtained by the method as described in the second aspect, or an exhaust gas treatment system as described in the third aspect.

[0119] Implementation

[0120] Various embodiments are listed below. It should be understood that the embodiments listed below can be combined with all aspects of the scope of the present invention and other embodiments.

[0121] 1. A particle filter, comprising:

[0122] - a substrate comprising a plurality of longitudinally extending porous walls to form a plurality of parallel channels extending from an inlet end to an outlet end, wherein a number of the channels are inlet channels open at the inlet end and closed at the outlet end, and a number of the channels are outlet channels closed at the inlet end and open at the outlet end;

[0123] - an in-wall TWC coating in the inlet channel and the outlet channel, the in-wall TWC coating comprising a platinum group metal component, an alumina-based refractory metal oxide and an oxygen storage component, wherein a weight ratio of the alumina-based refractory metal oxide to the oxygen storage component of the in-wall TWC coating is in the range of 1:20 to 1:3, and wherein the in-wall TWC coating does not contain any separate zirconium species and barium species;

[0124] as well as

[0125] - Optionally, the inorganic particle layer on the wall of the inlet channel and / or the outlet channel comprises an inorganic particle layer having a particle size of no greater than 0.5 cm 3 Inorganic particles with small BET pore volume of 1.1447 W / g.

[0126] 2. The particle filter according to embodiment 1, comprising an inorganic particle layer on the wall.

[0127] 3. A 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, most preferably 1:10 to 1:7.

[0128] 4. The particulate filter according to any one of the preceding embodiments, wherein the in-wall TWC coating in the inlet channel and the in-wall TWC coating in the outlet channel have the same composition.

[0129] 5. The particulate filter according to any one of the preceding embodiments, wherein the platinum group metal component is a Pt component, a Pd component, a Rh component, or any combination thereof.

[0130] 6. The particulate filter according to any one of the preceding embodiments, wherein the platinum group metal component is a combination of an Rh component, a Pt component and optionally a Pd component.

[0131] 7. A particulate filter according to any one of the preceding embodiments, wherein the inorganic particles, in particular the inorganic particles having a small BET pore volume, comprise one or more non-PGM components selected from alumina, hydrated alumina, boehmite, zirconium oxide, ceria, rare earth metal oxides other than ceria, silicon dioxide, titanium dioxide, magnesium oxide, manganese oxide, zinc oxide, zinc carbonate, calcium oxide, calcium carbonate, silicate zeolite, aluminosilicate zeolite or any composite oxide thereof.

[0132] 8. A particulate filter according to embodiment 7, wherein the inorganic particles, especially the inorganic particles having a small BET pore volume, contain one or more non-PGM components, and the one or more non-PGM components are selected from alumina, hydrated alumina, boehmite, zirconia, ceria, silica, titania, rare earth metal oxides other than ceria, or any composite oxides thereof.

[0133] 9. The particulate filter according to embodiment 8, wherein the inorganic particles, in particular the inorganic particles having a small BET pore volume, comprise alumina, hydrated alumina, boehmite, or a combination thereof.

[0134] 10. The particulate filter according to any one of the preceding embodiments, wherein the wall inorganic particle layer does not contain a PGM component.

[0135] 11. The particle filter according to any one of the preceding embodiments, wherein the small BET pore volume is not greater than 0.3 cm 3 / g or not more than 0.2cm 3 / g.

[0136] 12. The particle filter according to any one of the preceding embodiments, wherein the inorganic particles having a small BET pore volume have a pore size of not more than 100 m 2 / g, or not more than 80m 2 / g, or not more than 50m 2 / g of BET surface area.

[0137] 13. A method for producing a particle filter according to any one of the preceding embodiments, the method comprising the following steps:

[0138] (1) providing a slurry, comprising mixing a platinum group metal component or a precursor thereof, an alumina-based refractory metal oxide, and an oxygen storage component in a solvent, wherein the platinum group metal is not pre-fixed on the alumina-based refractory metal oxide and the oxygen storage component prior to the mixing; and applying the slurry to the inlet channel and the outlet channel of the substrate to form an in-wall TWC coating; and

[0139] (2) Optionally, applying inorganic particles or their precursors on the surface of the porous wall in the inlet channel and / or the outlet channel of the substrate bearing the in-wall TWC coating, and optionally drying and / or calcining to deposit an on-wall inorganic particle layer, the on-wall inorganic particle layer comprising a particle size of not more than 0.5 cm 3 Inorganic particles with small BET pore volume of 1.1447 W / g.

[0140] 14. The method according to embodiment 13, wherein the slurry in step (1) contains additives such as accelerators, binders, stabilizers, viscosity regulators, pH regulators, surfactants or any combination thereof.

[0141] 15. The method according to embodiment 13 or 14, wherein the precursor of the platinum group metal component is selected from the group consisting of soluble salts, complexes, oxides and colloids of the platinum group metal.

[0142] 16. A method according to any one of embodiments 13 to 15, wherein the slurry is provided 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 is added, and then the Rh component or a precursor thereof is added.

[0143] 17. A method according to any one of embodiments 13 to 15, wherein the slurry is provided by mixing the Rh component or a precursor thereof with an alumina-based refractory metal oxide in a solvent, an oxygen storage component is added to the solvent, and then the Pt component or a precursor thereof is added.

[0144] 18. The method according to any one of embodiments 13 to 17, wherein the inorganic particles are applied by a dry coating process.

[0145] 19. An exhaust gas treatment system comprising a particle filter according to any one of embodiments 1 to 12 or a particle filter obtainable from or obtainable from a method according to any one of embodiments 13 to 18, the particle filter being located downstream of a gasoline engine.

[0146] 20. A method for treating exhaust gas from a gasoline engine, the method comprising contacting the exhaust gas with a particulate filter according to any one of embodiments 1 to 12, or a particulate filter obtainable from or obtained from a method according to any one of embodiments 13 to 18, or an exhaust gas treatment system according to embodiment 19.

[0147] Example

[0148] Various aspects of the present invention are more fully illustrated by the following examples, which are set forth for the purpose of illustrating certain aspects of the present invention and should not be construed as limiting the present invention.

[0149] I. Preparation of Catalytic Gasoline Particulate Filter

[0150] Example 1 (E1, containing Ba / Zr, pre-fixed, alumina / OSC ratio of 0.37)

[0151] By applying the TWC washcoat slurry to a blank filter substrate ( The blank filter substrate has a size of 118.4 mm (D) × 127 mm (L) and a volume of 1.4 L (about 85.4 in). 3 ), a hole density of 300 holes per square inch (cpsi) and a wall thickness of 8 mils.

[0152] 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 in a planetary mixer (P-mixer) onto 693 g of La / Y-doped ceria-zirconia composite oxide (OSC, 40% ceria, 5% lanthanum oxide, 5% yttrium oxide, and the balance zirconium oxide) to form a wet Pt / OSC powder while achieving initial 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 solution of zirconium nitrate to form a Pt / OSC slurry. The slurry was adjusted to pH 3.5 with nitric acid and ground to a particle size D 90 is 4.5μm.

[0153] 20.29 g of a 9.67 wt % aqueous rhodium nitrate solution was mixed with 179 g of deionized water and impregnated onto 256 g of gamma alumina powder in a planetary mixer (P-mixer) to form a wet Rh / alumina powder while achieving initial wetness. 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 slurry was adjusted to pH 3.5 with nitric acid and ground to a particle size D 90 is 4.5μm.

[0154] The Pt / OSC slurry and the Rh / alumina slurry were combined into a final slurry and then coated from the inlet end of the filter substrate along 52% of the axial length of the filter using 50% of the target washcoat loading, and from the outlet end of the filter substrate using the remaining 50% of the target washcoat loading along up to about 52% of the axial length of the filter. The coated substrate was then dried at 150° C. for 1 h and then calcined at 550° C. for 1 h.

[0155] The obtained inner wall TWC coating has a thermal conductivity of 1.48 g / in 3 Washcoat loading and 15.0 g / ft 3 The total PGM loading was 100%, with a Pt / Rh ratio of 10 / 5.

[0156] Example 2 (E2, containing Ba / Zr, pre-fixed, alumina / OSC ratio of 0.30)

[0157] A particulate filter with an in-wall TWC coating was prepared from a blank filter substrate identical to the filter substrate of Example 1 by applying the TWC washcoat slurry into both the inlet and outlet channels of the blank filter.

[0158] 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% lanthanum oxide, 5% yttrium oxide and the balance zirconium oxide) in a planetary mixer (P-mixer) to form a wet Pt / OSC powder while achieving initial 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 solution of zirconium nitrate to form a Pt / OSC slurry. The slurry was adjusted to pH 3.5 with nitric acid and ground to a particle size D 90 is 4.5μm.

[0159] 20.29 g of a 9.67 wt % aqueous rhodium nitrate solution was mixed with 153 g of deionized water and impregnated onto 219 g of gamma alumina powder in a planetary mixer (P-mixer) to form a wet Rh / alumina powder while achieving initial wetness. 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 % aqueous zirconium nitrate solution to form a Rh / alumina slurry. The slurry was adjusted to pH 3.5 with nitric acid and ground to a particle size D 90 is 4.5μm.

[0160] The Pt / OSC slurry and the Rh / alumina slurry were combined into a final slurry and then coated from the inlet end of the filter substrate along 52% of the axial length of the filter using 50% of the target washcoat loading, and from the outlet end of the filter substrate using the remaining 50% of the target washcoat loading along up to about 52% of the axial length of the filter. The coated substrate was then dried at 150° C. for 1 h and then calcined at 550° C. for 1 h.

[0161] The obtained inner wall TWC coating has a thermal conductivity of 1.48 g / in 3 Washcoat loading and 15.0 g / ft3 The total PGM loading was 100%, with a Pt / Rh ratio of 10 / 5.

[0162] Example 3 (E3, containing Ba / Zr, pre-fixed, alumina / OSC ratio of 0.20)

[0163] A particulate filter with an in-wall TWC coating was prepared from a blank filter substrate identical to the filter substrate of Example 1 by applying the TWC washcoat slurry into both the inlet and outlet channels of the blank filter.

[0164] 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 in a planetary mixer (P-mixer) onto 791 g of La / Y-doped ceria-zirconia composite oxide (OSC, 40% ceria, 5% lanthanum oxide, 5% yttrium oxide, and the balance zirconium oxide) to form a wet Pt / OSC powder while achieving initial 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 solution of zirconium nitrate to form a Pt / OSC slurry. The slurry was adjusted to pH 3.5 with nitric acid and ground to a particle size D 90 is 4.5μm.

[0165] 20.29 g of a 9.67 wt % aqueous rhodium nitrate solution was mixed with 111 g of deionized water and impregnated onto 158 g of gamma alumina powder in a planetary mixer (P-mixer) to form a wet Rh / alumina powder while achieving initial wetness. 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 % aqueous zirconium nitrate solution to form a Rh / alumina slurry. The slurry was adjusted to pH 3.5 with nitric acid and ground to a particle size D 90 is 4.5μm.

[0166] The Pt / OSC slurry and the Rh / alumina slurry were combined into a final slurry and then coated from the inlet end of the filter substrate along 52% of the axial length of the filter using 50% of the target washcoat loading, and from the outlet end of the filter substrate using the remaining 50% of the target washcoat loading along up to about 52% of the axial length of the filter. The coated substrate was then dried at 150° C. for 1 h and then calcined at 550° C. for 1 h.

[0167] The obtained inner wall TWC coating has a thermal conductivity of 1.48 g / in 3 Washcoat loading and 15.0 g / ft 3 The total PGM loading was 100%, with a Pt / Rh ratio of 10 / 5.

[0168] Example 4 (E4, containing Ba / Zr, pre-fixed, alumina / OSC ratio of 0.12)

[0169] A particulate filter with an in-wall TWC coating was prepared from a blank filter substrate identical to the filter substrate of Example 1 by applying the TWC washcoat slurry into both the inlet and outlet channels of the blank filter.

[0170] 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 in a planetary mixer (P-mixer) onto 846 g of La / Y-doped ceria-zirconia composite oxide (OSC, 40% ceria, 5% lanthanum oxide, 5% yttrium oxide and the balance zirconium oxide) to form a wet Pt / OSC powder while achieving initial 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 solution of zirconium nitrate to form a Pt / OSC slurry. The slurry was adjusted to pH 3.5 with nitric acid and ground to a particle size D 90 is 4.5μm.

[0171] 20.29 g of a 9.67 wt % aqueous rhodium nitrate solution was mixed with 72 g of deionized water and impregnated onto 103 g of gamma alumina powder in a planetary mixer (P-mixer) to form a wet Rh / alumina powder while achieving initial wetness. 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 % aqueous zirconium nitrate solution to form a Rh / alumina slurry. The slurry was adjusted to pH 3.5 with nitric acid and ground to a particle size D 90 is 4.5μm.

[0172] The Pt / OSC slurry and the Rh / alumina slurry were combined into a final slurry and then coated from the inlet end of the filter substrate along 52% of the axial length of the filter using 50% of the target washcoat loading, and from the outlet end of the filter substrate using the remaining 50% of the target washcoat loading along up to about 52% of the axial length of the filter. The coated substrate was then dried at 150° C. for 1 h and then calcined at 550° C. for 1 h.

[0173] The obtained inner wall TWC coating has a thermal conductivity of 1.48 g / in 3 Washcoat loading and 15.0 g / ft 3 The total PGM loading was 100%, with a Pt / Rh ratio of 10 / 5.

[0174] Example 5 (E5, containing Ba / Zr, pre-fixed, alumina / OSC ratio of 0.12)

[0175] A particulate filter with an in-wall TWC coating was prepared from a blank filter substrate identical to the filter substrate of Example 1 by applying the TWC washcoat slurry into both the inlet and outlet channels of the blank filter.

[0176] 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 in a planetary mixer (P-mixer) onto 846 g of La / Y-doped ceria-zirconia composite oxide (OSC, 40% ceria, 5% lanthanum oxide, 5% yttrium oxide and the balance zirconium oxide) to form a wet Pt / OSC powder while achieving initial 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 solution of zirconium nitrate to form a Pt / OSC slurry. The slurry was adjusted to pH 3.5 with nitric acid and ground to a particle size D 90 is 4.5μm.

[0177] 20.33 g of a 9.67 wt % aqueous rhodium nitrate solution was mixed with 72 g of deionized water and impregnated onto 103 g of gamma alumina powder in a planetary mixer (P-mixer) to form a wet Rh / alumina powder while achieving initial wetness. 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 % aqueous zirconium nitrate solution to form a Rh / alumina slurry. The slurry was adjusted to pH 3.5 with nitric acid and ground to a particle size D 90 is 4.5μm.

[0178] The Pt / OSC slurry and the Rh / alumina slurry were combined into a final slurry and then coated from the inlet end of the filter substrate along 52% of the axial length of the filter using 50% of the target washcoat loading, and from the outlet end of the filter substrate using the remaining 50% of the target washcoat loading along up to about 52% of the axial length of the filter. The coated substrate was then dried at 150° C. for 1 h and then calcined at 550° C. for 1 h.

[0179] The obtained inner wall TWC coating has a thermal conductivity of 1.48 g / in 3 Washcoat loading and 10.0 g / ft 3 The total PGM loading was 500 wt % with a Pt / Rh ratio of 5 / 5.

[0180] Example 6 (E6, containing Ba / Zr, pre-fixed, alumina / OSC ratio of 0.05)

[0181] A particulate filter with an in-wall TWC coating was prepared from a blank filter substrate identical to the filter substrate of Example 1 by applying the TWC washcoat slurry into both the inlet and outlet channels of the blank filter.

[0182] 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 in a planetary mixer (P-mixer) onto 892 g of La / Y-doped ceria-zirconia composite oxide (OSC, 40% ceria, 5% lanthanum oxide, 5% yttrium oxide and the balance zirconium oxide) to form a wet Pt / OSC powder while achieving initial 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 solution of zirconium nitrate to form a Pt / OSC slurry. The slurry was adjusted to pH 3.5 with nitric acid and ground to a particle size D 90 is 4.5μm.

[0183] 20.33 g of a 9.67 wt % aqueous rhodium nitrate solution was mixed with 32 g of deionized water and impregnated onto 45 g of gamma alumina powder in a planetary mixer (P-mixer) to form a wet Rh / alumina powder while achieving initial wetness. 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 slurry was adjusted to pH 3.5 with nitric acid and ground to a particle size D 90 is 4.5μm.

[0184] The Pt / OSC slurry and the Rh / alumina slurry were combined into a final slurry and then coated from the inlet end of the filter substrate along 52% of the axial length of the filter using 50% of the target washcoat loading, and from the outlet end of the filter substrate using the remaining 50% of the target washcoat loading along up to about 52% of the axial length of the filter. The coated substrate was then dried at 150° C. for 1 h and then calcined at 550° C. for 1 h.

[0185] The obtained inner wall TWC coating has a thermal conductivity of 1.48 g / in 3 Washcoat loading and 10.0 g / ft 3 The total PGM loading was 500 wt % with a Pt / Rh ratio of 5 / 5.

[0186] Example 7 (E7, containing Ba / Zr, pre-fixed, without aluminum oxide)

[0187] A particulate filter with an in-wall TWC coating was prepared from a blank filter substrate identical to the filter substrate of Example 1 by applying the TWC washcoat slurry into both the inlet and outlet channels of the blank filter.

[0188] 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 in a planetary mixer (P-mixer) onto 846 g of La / Y-doped ceria-zirconia composite oxide (OSC, 40% ceria, 5% lanthanum oxide, 5% yttrium oxide and the balance zirconium oxide) to form a wet Pt / OSC powder while achieving initial 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 solution of zirconium nitrate to form a Pt / OSC slurry. The slurry was adjusted to pH 3.5 with nitric acid and ground to a particle size D 90 is 4.5μm.

[0189] 20.29 g of a 9.67 wt % aqueous rhodium nitrate solution was mixed with 41 g of deionized water and impregnated in a planetary mixer (P-mixer) onto 103 g of La / Y-doped ceria-zirconia composite oxide (OSC, 40% ceria, 5% lanthanum oxide, 5% yttrium oxide and the balance zirconium oxide) to form a wet Rh / OSC powder while achieving initial 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 % aqueous zirconium nitrate solution to form a Rh / OSC slurry. The slurry was adjusted to pH 3.5 with nitric acid and ground to a particle size D 90 is 4.5μm.

[0190] The Pt / OSC slurry and the Rh / OSC slurry were combined into a final slurry and then coated from the inlet end of the filter substrate along 52% of the axial length of the filter using 50% of the target washcoat loading, and from the outlet end of the filter substrate using the remaining 50% of the target washcoat loading along up to about 52% of the axial length of the filter. The coated substrate was then dried at 150°C for 1 h and then calcined at 550°C for 1 h.

[0191] The obtained inner wall TWC coating has a thermal conductivity of 1.48 g / in 3 Washcoat loading and 10.0 g / ft 3 The total PGM loading was 500 wt % with a Pt / Rh ratio of 5 / 5.

[0192] Example 8 (E8, containing Zr, without Ba, pre-fixed, alumina / OSC ratio 0.12)

[0193] A particulate filter with an in-wall TWC coating was prepared from a blank filter substrate identical to the filter substrate of Example 1 by applying the TWC washcoat slurry into both the inlet and outlet channels of the blank filter.

[0194] 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% lanthanum oxide, 5% yttrium oxide and the balance zirconium oxide) in a planetary mixer (P-mixer) to form a wet Pt / OSC powder while achieving initial wetness. The wet Pt / OSC powder was mixed with 912 g of deionized water, 39 g of a 21.6 wt% aqueous solution of zirconium nitrate to form a Pt / OSC slurry. The slurry was adjusted to pH 3.5 with nitric acid and ground to a particle size D 90 is 4.5μm.

[0195] 20.33 g of a 9.67 wt % aqueous rhodium nitrate solution was mixed with 72 g of deionized water and impregnated onto 103 g of gamma alumina powder in a planetary mixer (P-mixer) to form a wet Rh / alumina powder while achieving initial wetness. The wet Rh / alumina powder was mixed with 68 g of deionized water, 26 g of a 21.6 wt % aqueous zirconium nitrate solution to form a Rh / alumina slurry. The slurry was adjusted to pH 3.5 with nitric acid and ground to a particle size D 90 is 4.5μm.

[0196] The Pt / OSC slurry and the Rh / alumina slurry were combined into a final slurry and then coated from the inlet end of the filter substrate along 52% of the axial length of the filter using 50% of the target washcoat loading, and from the outlet end of the filter substrate using the remaining 50% of the target washcoat loading along up to about 52% of the axial length of the filter. The coated substrate was then dried at 150° C. for 1 h and then calcined at 550° C. for 1 h.

[0197] The obtained inner wall TWC coating has a thermal conductivity of 1.48 g / in 3 Washcoat loading and 10.0 g / ft 3 The total PGM loading was 500 wt % with a Pt / Rh ratio of 5 / 5.

[0198] Example 9 (E9, without Ba and Zr, pre-fixed, alumina / OSC ratio of 0.12)

[0199] A particulate filter with an in-wall TWC coating was prepared from a blank filter substrate identical to the filter substrate of Example 1 by applying the TWC washcoat slurry into both the inlet and outlet channels of the blank filter.

[0200] 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 in a planetary mixer (P-mixer) onto 846 g of La / Y-doped ceria-zirconia composite oxide (OSC, 40% ceria, 5% lanthanum oxide, 5% yttrium oxide, and the balance zirconium oxide) to form a wet Pt / OSC powder while achieving initial wetness. The wet Pt / OSC powder was mixed with 912 g of deionized water to form a Pt / OSC slurry. The slurry was adjusted to pH 3.5 with nitric acid and ground to a particle size D 90 is 4.5μm.

[0201] 20.33 g of a 9.67 wt % aqueous rhodium nitrate solution was mixed with 72 g of deionized water and impregnated onto 103 g of gamma alumina powder in a planetary mixer (P-mixer) to form a wet Rh / alumina powder while achieving initial wetness. The wet Rh / alumina powder was mixed with 68 g of deionized water to form a Rh / alumina slurry. The slurry was adjusted to pH 3.5 with nitric acid and ground to a particle size D 90 is 4.5μm.

[0202] The Pt / OSC slurry and the Rh / alumina slurry were combined into a final slurry and then coated from the inlet end of the filter substrate along 52% of the axial length of the filter using 50% of the target washcoat loading, and from the outlet end of the filter substrate using the remaining 50% of the target washcoat loading along up to about 52% of the axial length of the filter. The coated substrate was then dried at 150° C. for 1 h and then calcined at 550° C. for 1 h.

[0203] The obtained inner wall TWC coating has a thermal conductivity of 1.48 g / in 3 Washcoat loading and 10.0 g / ft 3 The total PGM loading was 500 wt % with a Pt / Rh ratio of 5 / 5.

[0204] Example 10 (E10, containing Ba / Zr, pre-fixed, alumina / OSC ratio of 0.12)

[0205] A particulate filter with an in-wall TWC coating was prepared from a blank filter substrate identical to the filter substrate of Example 1 by applying the TWC washcoat slurry into both the inlet and outlet channels of the blank filter.

[0206] 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 in a planetary mixer (P-mixer) onto 846 g of La / Y-doped ceria-zirconia composite oxide (OSC, 40% ceria, 5% lanthanum oxide, 5% yttrium oxide and the balance zirconium oxide) to form a wet Pt / OSC powder while achieving initial 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 solution of zirconium nitrate to form a Pt / OSC slurry. The slurry was adjusted to pH 3.5 with nitric acid and ground to a particle size D 90 is 4.5μm.

[0207] 15.10 g of a 9.67 wt % aqueous rhodium nitrate solution was mixed with 72 g of deionized water and impregnated onto 103 g of gamma alumina powder in a planetary mixer (P-mixer) to form a wet Rh / alumina powder while achieving initial wetness. 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 % aqueous zirconium nitrate solution to form a Rh / alumina slurry. The slurry was adjusted to pH 3.5 with nitric acid and ground to a particle size D 90 is 4.5μm.

[0208] The Pt / OSC slurry and the Rh / alumina slurry were combined into a final slurry and then coated from the inlet end of the filter substrate along 52% of the axial length of the filter using 50% of the target washcoat loading, and from the outlet end of the filter substrate using the remaining 50% of the target washcoat loading along up to about 52% of the axial length of the filter. The coated substrate was then dried at 150° C. for 1 h and then calcined at 550° C. for 1 h.

[0209] The obtained inner wall TWC coating has a thermal conductivity of 1.98 g / in 3 Washcoat loading and 20.0 g / ft 3 The total PGM loading was 15:5, with a Pt / Rh ratio of 15:5.

[0210] Example 11 (E11, containing Ba / Zr, one-pot process, alumina / OSC ratio of 0.12)

[0211] A particulate filter with an in-wall TWC coating was prepared from a blank filter substrate identical to the filter substrate of Example 1 by applying the TWC washcoat slurry into both the inlet and outlet channels of the blank filter.

[0212] 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% lanthanum oxide, 5% yttrium oxide and the balance of zirconium oxide), 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 slurry was adjusted to pH 3.5 with nitric acid and ground to a particle size D 90 is 4.5μm.

[0213] The slurry was then coated from the inlet end of the filter substrate along 52% of the axial length of the filter using 50% of the target washcoat loading, and the remaining 50% of the target washcoat loading was coated from the outlet end of the filter substrate along up to about 52% of the axial length of the filter. The coated substrate was then dried at 150°C for 1 hour and then calcined at 550°C for 1 hour.

[0214] The obtained inner wall TWC coating has a thermal conductivity of 1.98 g / in 3 Washcoat loading and 20.0 g / ft 3 The total PGM loading was 15:5, with a Pt / Rh ratio of 15:5.

[0215] Example 12 (E12, containing Ba / Zr, pre-fixed, alumina / OSC ratio of 0.37)

[0216] A particulate filter with an in-wall TWC coating was prepared by applying a TWC washcoat slurry to both the inlet and outlet channels of a blank filter substrate. The dimensions of the blank filter substrate were 118.4 mm (D) x 127 mm (L) and the volume was 1.4 L (approximately 85.4 in 3 ), a hole density of 300 holes per square inch (cpsi) and a wall thickness of 8 mils.

[0217] 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 in a planetary mixer (P-mixer) onto 693 g of La / Y-doped ceria-zirconia composite oxide (OSC, 40% ceria, 5% lanthanum oxide, 5% yttrium oxide and the balance zirconium oxide) to form a wet Pt / OSC powder while achieving initial 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 solution of zirconium nitrate to form a Pt / OSC slurry. The slurry was adjusted to pH 3.5 with nitric acid and ground to a particle size D 90 is 4.5μm.

[0218] 40.30 g of a 9.67 wt % aqueous rhodium nitrate solution was mixed with 180 g of deionized water and impregnated onto 256 g of gamma alumina powder in a planetary mixer (P-mixer) to form a wet Rh / alumina powder while achieving initial wetness. 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 slurry was adjusted to pH 3.5 with nitric acid and ground to a particle size D 90 is 4.5μm.

[0219] The Pt / OSC slurry and the Rh / alumina slurry were combined into a final slurry and then coated from the inlet end of the filter substrate along 52% of the axial length of the filter using 50% of the target washcoat loading, and from the outlet end of the filter substrate using the remaining 50% of the target washcoat loading along up to about 52% of the axial length of the filter. The coated substrate was then dried at 150° C. for 1 h and then calcined at 550° C. for 1 h.

[0220] The obtained inner wall TWC coating has a thermal conductivity of 1.48 g / in 3 Washcoat loading and 30.0 g / ft 3 The total PGM loading was 20:1 with a Pt / Rh ratio of 20:10.

[0221] Example 13 (E13, without Ba and Zr, one-pot process, alumina / OSC ratio of 0.12)

[0222] A particulate filter with an in-wall TWC coating was prepared from a blank filter substrate identical to the filter substrate of Example 1 by applying the TWC washcoat slurry into both the inlet and outlet channels of the blank filter.

[0223] 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% lanthanum oxide, 5% yttrium oxide and the balance of zirconium oxide) 111 g of γ-alumina powder and 40.30 g of a 9.67 wt% aqueous solution of rhodium nitrate were added to form a slurry. The slurry was adjusted to pH 3.5 with nitric acid and ground to a particle size D 90 is 4.5μm.

[0224] The slurry was then coated from the inlet end of the filter substrate along 52% of the axial length of the filter using 50% of the target washcoat loading, and the remaining 50% of the target washcoat loading was coated from the outlet end of the filter substrate along up to about 52% of the axial length of the filter. The coated substrate was then dried at 150°C for 1 hour and then calcined at 550°C for 1 hour.

[0225] The obtained inner wall TWC coating has a thermal conductivity of 1.48 g / in 3 Washcoat loading and 30.0 g / ft 3 The total PGM loading was 20:1 with a Pt / Rh ratio of 20:10.

[0226] Example 14 (E14, applying a wall top layer on the same particle filter as E12)

[0227] A particulate filter having a TWC coating inside the wall and a high BET pore volume inorganic particle layer on the wall was prepared.

[0228] Alumina powder was mixed with carrier gas and heated at 600 m / s at room temperature. 3 / h was blown into the inlet channel of the particle filter having the inner wall TWC coating obtained by the same method as described in Example 12. The alumina used had a 150 m 2 / g surface area and 0.68cm 3 The pore volume of 1.04 μm / g was measured by a Micromeritics ASAP2420 analyzer with a BET model at 77 K under nitrogen adsorption and had a D 10 , D of 2.33 μm 50 and D of 4.31 μm 90 The particle size distribution of the particles was measured by a Sympatec HELOS laser diffraction particle size analyzer. After coating, the filter with the wall alumina particle layer in the inlet channel was calcined at a temperature of 550°C for 1 hour. The loading of the alumina layer was 2 g / L (0.033 g / in 3 ).

[0229] Example 15 (E15, application of a wall top layer on the same particle filter as E13)

[0230] A particulate filter having an inner wall TWC coating and an on-wall high BET pore volume inorganic particle layer was prepared by the same method as described in Example 14, except that alumina powder was blown into the inlet channel of the particulate filter having an inner wall TWC coating obtained by the same method as described in Example 13, and the loading amount of alumina particles was 5 g / L (0.082 g / in 3 ).

[0231] Example 16 (E16, applying a wall top layer on the same particle filter as E13)

[0232] A particle filter having a TWC coating inside the wall and a layer of small BET pore volume inorganic particles on the wall was prepared.

[0233] The boehmite powder was mixed with carrier gas and heated at 600 m / s at room temperature. 3 / h was blown into the inlet channel of a particle filter having an inner wall TWC coating obtained by the same method as described in Example 13. The boehmite used had a 30 m 2 / g surface area and 0.08cm 3 / g pore volume as measured by a Micromeritics ASAP 2420 analyzer with BET model at 77K under nitrogen adsorption and having a D 10 , D of 0.92μm 50 and D of 1.70 μm 90 The particle size distribution of the aluminum oxide layer was 2 g / L (about 0.033 g / in 3 ).

[0234] II. Performance Evaluation

[0235] II.1 Catalytic performance (oxygen storage capacity and catalytic activity)

[0236] The oxygen storage capacity and gas emissions of the particulate filter were studied. In order to evaluate the aged filter, the fresh filter was exothermally aged for 100 hours or 200 hours at an inlet temperature of 875°C on a GM 8.1L V8 engine before testing. The fixed oxygen storage capacity (SOSC) value of each sample was measured in a closed position on an Audi 2.0L turbocharged engine, with an inlet temperature of 580°C and a flow rate of 50kg / h. Under the WLTC scheme, the gas emissions of each sample were measured in a closed position on a Daimler 2.0L engine, and THC, CO and NOx emissions were measured downstream of each sample. Lower emission values ​​indicate that the catalytic activity of the filter is higher. The results of SOSC values ​​and gas emissions are shown in Tables 1 to 4.

[0237] Table 1

[0238]

[0239] From the comparison between E1 and E2 to E4, it can be seen that the catalyzed particulate filters with inner-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) compared to the catalyzed particulate filter with an inner-wall TWC coating having an alumina / OSC ratio of 0.37.

[0240] It can also be seen from the comparison between E5 or E6 and E7 that the catalyzed particulate filters with inner-wall TWC coatings with 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 filter with an inner-wall TWC coating with alumina / OSC ratios of 0, which is unexpected because the catalyzed particulate filters with inner-wall TWC coatings with alumina / OSC ratios of 0.12 and 0.05 even exhibit higher SOSC values ​​than their counterparts containing a single oxygen storage component.

[0241] Table 2

[0242]

[0243] From the comparison between E5 and E8 and the comparison between E8 and E9, it can be seen that the absence of either barium oxide or zirconium oxide alone in the TWC coating inside the wall of the catalytic particulate filter can lead to improvements in oxygen storage capacity and catalytic activity. In addition, it can be seen that the absence of both barium oxide and zirconium oxide alone in the TWC coating inside the wall can lead to the highest SOSC value and the highest catalytic activity.

[0244] Table 3

[0245]

[0246] Catalyzed particulate filter E10 was obtained from a slurry prepared via a conventional method including pre-fixing PGM onto a support, whereas catalyzed particulate filter E11 was obtained from a slurry prepared via a one-pot method. Surprisingly, catalyzed particulate filter E11 showed higher SOSC values ​​and higher catalytic activity than catalyzed particulate filter E10.

[0247] Table 4

[0248]

[0249] Table 4 (continued)

[0250]

[0251] As can be seen from the comparison between E12 and E13, in both the fresh and aged states, the catalyzed particulate filter with a reduced alumina / OSC ratio made from a slurry from a one-pot process in the absence of separate barium and zirconium species shows significantly improved oxygen storage capacity and catalytic activity compared to the catalyzed particulate filter with a conventional alumina / OSC ratio made from a slurry from a pre-fixation process in the presence of separate barium and zirconium species.

[0252] Table 5

[0253]

[0254] It can be seen that the catalytic particulate filter (E16) having the inner-wall TWC coating of the present invention and the upper wall layer comprising inorganic particles having a small BET pore volume exhibits much higher SOSC values ​​and much lower gas emissions when fresh, after aging for 100 hours, and after aging for 200 hours, compared with the catalytic particulate filter (E14) having a conventional inner-wall TWC coating and an upper wall layer comprising inorganic particles having a high BET pore volume.

[0255] It was also found that the oxygen storage capacity of the catalytic particulate filter decayed from the state aged 100 hours to the state aged 200 hours. Surprisingly, the decay of the oxygen storage capacity of the catalytic particulate filter E16 was much less than the decay of the oxygen storage capacity of the catalytic particulate filter E14, which indicates that the particulate filter according to the present invention has greater robustness during aging.

[0256] II.2 Filtration performance (back pressure and fresh filtration efficiency)

[0257] The back pressure (BP) of the particle filter was also studied, such as by using a SuperFlow SF-1020 Flowbench at 600 m 3 The back pressure of a blank filter was also measured as a reference and was 50 mbar.

[0258] According to the standard procedure defined in "BS EN ISO 29463-5:2018 – Part 5: Test method for filter elements", the test results were tested in a 600m 3 The filtration efficiency of the particle filter in the fresh state (0 km or out-of-box state) is measured on a fixed air filter performance test bench with a cold air flow of 1000 rpm / h, using aerosol di(2-ethylhexyl) sebacate as the particle. The particle number (PN) of particles ranging between 0.10 μm and 0.15 μm is recorded by a PN counter both upstream and downstream of the filter being tested. The fresh filtration efficiency (FFE) is calculated according to the following formula:

[0259]

[0260] The BP and FFE test results are summarized in Table 6 below.

[0261] Table 6

[0262]

[0263] It can be seen that the catalytic particle filter E13 according to the present invention without the inorganic particle layer exhibits a lower back pressure than the conventional filter E12. After applying the inorganic particle layer, at the same back pressure, the catalytic particle filter E16 according to the present invention exhibits a significantly higher fresh filtration efficiency (FFE) than the comparative catalytic particle filter E14, and exhibits a higher fresh filtration efficiency (FFE) at a lower back pressure than the comparative catalytic particle filter E15.

[0264] Although the present invention has been described herein with reference to specific embodiments, it should 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 may be made to the methods and apparatus of the present invention without departing from the spirit and scope of the present invention. Therefore, the present invention is intended to include modifications and variations within the scope of the appended claims and their equivalents.

Claims

1. A particle filter, comprising: - a substrate comprising a plurality of longitudinally extending porous walls to form a plurality of parallel channels extending from an inlet end to an outlet end, wherein a number of the channels are inlet channels open at the inlet end and closed at the outlet end, and a number of the channels are outlet channels closed at the inlet end and open at the outlet end; - an in-wall TWC coating in the inlet channel and the outlet channel, the in-wall TWC coating comprising a platinum group metal component, an alumina-based refractory metal oxide and an oxygen storage component, wherein a weight ratio of the alumina-based refractory metal oxide to the oxygen storage component of the in-wall TWC coating is in the range of 1:20 to 1:3, and wherein the in-wall TWC coating does not contain any separate zirconium species and barium species; as well as - Optionally, the inorganic particle layer on the wall of the inlet channel and / or the outlet channel comprises an inorganic particle layer having a particle size of no greater than 0.5 cm 3 Inorganic particles with small BET pore volume of 1.1447 W / g. 2 . The particle filter according to claim 1 , comprising an inorganic particle layer on the wall.

3. The particulate filter according to 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, most preferably 1:10 to 1:

7. 4 . The particle filter according to claim 1 , wherein the inner-wall TWC coating in the inlet channel and the inner-wall TWC coating in the outlet channel have the same composition. 5 . The particulate filter according to claim 1 , wherein the platinum group metal component is a Pt component, a Pd component, a Rh component, or any combination thereof.

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

7. A particulate filter according to any one of the preceding claims, wherein the inorganic particles, in particular the inorganic particles having a small BET pore volume, comprise one or more non-PGM components selected from alumina, hydrated alumina, boehmite, zirconium oxide, ceria, rare earth metal oxides other than ceria, silicon dioxide, titanium dioxide, magnesium oxide, manganese oxide, zinc oxide, zinc carbonate, calcium oxide, calcium carbonate, silicate zeolite, aluminosilicate zeolite or any composite oxide thereof.

8. The particulate filter according to claim 7, wherein the inorganic particles, in particular the inorganic particles having a small BET pore volume, comprise one or more non-PGM components selected from alumina, hydrated alumina, boehmite, zirconia, ceria, silica, titania, rare earth metal oxides other than ceria, or any composite oxides thereof. 9 . The particle filter according to claim 8 , wherein the inorganic particles, in particular the inorganic particles having a small BET pore volume, comprise alumina, hydrated alumina, boehmite, or a combination thereof.

10. The particle filter according to any one of the preceding claims, wherein the wall inorganic particle layer does not contain a PGM component.

11. A particle filter according to any one of the preceding claims, wherein the small BET pore volume is no greater than 0.3 cm 3 / g or not more than 0.2cm 3 / g.

12. The particle filter according to any one of the preceding claims, wherein the inorganic particles having a small BET pore volume have a pore size of not more than 100 m 2 / g, or not more than 80m 2 / g, or not more than 50m 2 / g of BET surface area.

13. A method for producing a particle filter according to any one of the preceding claims, the method comprising the steps of: (1) providing a slurry comprising mixing a platinum group metal component or a precursor thereof, an alumina-based refractory metal oxide, and an oxygen storage component in a solvent, wherein the platinum group metal is not pre-fixed on the alumina-based refractory metal oxide and the oxygen storage component prior to the mixing; and applying the slurry to the inlet channel and the outlet channel of the substrate, To form a TWC coating inside the wall; as well as (2) Optionally, applying inorganic particles or their precursors on the surface of the porous wall in the inlet channel and / or the outlet channel of the substrate bearing the in-wall TWC coating, and optionally drying and / or calcining to deposit an on-wall inorganic particle layer, the on-wall inorganic particle layer comprising a particle size of not more than 0.5 cm 3 Inorganic particles with small BET pore volume of 1.1447 W / g.

14. The method according to claim 13, wherein the slurry in step (1) comprises additives such as accelerators, binders, stabilizers, viscosity regulators, pH regulators, surfactants or any combination thereof.

15. The method of claim 13 or 14, wherein the precursor of the platinum group metal component is selected from the group consisting of soluble salts, complexes, oxides and colloids of the platinum group metal.

16. The method according to any one of claims 13 to 15, wherein the slurry is provided 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 is added, and then a Rh component or a precursor thereof is added.

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

18. A method according to any one of claims 13 to 17, wherein the inorganic particles are applied by a dry coating process.

19. An exhaust gas treatment system comprising a particle filter according to any one of claims 1 to 12 or obtainable or obtainable from a method according to any one of claims 13 to 18, the particle filter being located downstream of a gasoline engine.

20. A method for treating exhaust gases from a gasoline engine, the method comprising contacting the exhaust gases with a particle filter according to any one of claims 1 to 12, or a particle filter obtainable or obtainable from a method according to any one of claims 13 to 18, or an exhaust gas treatment system according to claim 19.

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