Gasoline particulate filter

Abstract

The present invention relates to a particulate filter, the particulate filter being a substrate including a plurality of porous walls extending longitudinally so as to form a plurality of parallel flow paths extending from an inlet end to an outlet end, wherein a certain amount of the flow paths are inlet flow paths that are open at the inlet end and closed at the outlet end, and a certain amount of the flow paths are outlet flow paths that are closed at the inlet end and open at the outlet end, a layer of inorganic particles loaded on the surface of the porous walls in the inlet flow path and / or the outlet flow path, the layer of inorganic particles including acicular crystal inorganic particles. The present invention also relates to a method for manufacturing a particulate filter including applying an inorganic particle or a precursor thereof to the surface of the porous walls in the inlet flow path and / or the outlet flow path, at least a part of the inorganic particle or the precursor thereof being acicular crystal particles.

Description

【Technical Field】 【0001】 The present invention relates to a particulate filter for treating an exhaust stream from a gasoline engine, including an inorganic powder particle coating. The present invention also relates to a gasoline engine exhaust treatment system including the particulate filter and a method for treating an exhaust stream from a gasoline engine. 【Background Art】 【0002】 Engine exhaust substantially consists of gaseous pollutants such as unburned hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NOx), and particulate matter (PM). For gasoline engines, a three-way conversion catalyst for gaseous pollutants (hereinafter, interchangeably referred to as a TWC catalyst or TWC) and a filter for particulate matter (PM) are well-known post-exhaust treatment means to ensure that the exhaust gas meets emission regulations. 【0003】 In contrast to the particulate matter generated by a diesel lean burn engine, the particulate matter generated by a gasoline engine such as a gasoline direct injection engine is finer and tends to be in a smaller amount. This is because the combustion conditions of a gasoline engine are different from those of a diesel engine. Also, the hydrocarbon component is different in the exhaust of a gasoline engine compared to a diesel engine. In order to effectively treat the engine exhaust from a gasoline engine, particulate filters dedicated to gasoline engines have been developed over several decades. 【0004】 For example, International Publication No. 2018 / 024547 (A1) describes a catalytic particulate filter comprising a TWC catalyst material that penetrates the walls of the particulate filter. Coating the TWC catalyst material on or within the filter may result in an impact on the back pressure. In order to provide a complete three-way conversion function while avoiding an excessive increase in back pressure, specific coating schemes have been proposed in patent applications. The catalytic particulate filter is required to have a coated porosity smaller than the uncoated porosity of the particulate filter. 【0005】 International Publication No. 2018 / 115900 (A1) describes a particulate filter for use in an exhaust treatment system of a gasoline engine. This filter has an inlet side and an outlet side, and at least the inlet side is loaded with synthetic ash containing one or more of aluminum oxide, zinc oxide, zinc carbonate, calcium oxide, calcium carbonate, cerium zirconium (mixed) oxide, zirconium oxide, cerium oxide, and hydrated alumina. It is described that the particle distribution can help prevent a significant amount of synthetic ash from entering the pores of the porous substrate. 【0006】 It is known that the filtration performance of a gasoline particulate filter is improved over the life of the filter, mainly as a result of the accumulation of ash and soot on the walls of the inlet side of the filter. Also, it has been confirmed that the number of particles in the emissions generated during the cold start phase of the test cycle represents the majority of the total particles emitted during the test. Therefore, the particle filtration performance at the initial filtration stage, also called the fresh filtration efficiency, is a major concern in developing a gasoline particulate filter. 【0007】 Since particulate emissions from gasoline engines are subject to more stringent regulations such as Euro 6 and China 6, vehicle manufacturers, i.e., original equipment manufacturers (OEMs) of competing brand products, require that gasoline particulate filters have high fresh filtration efficiency with a desirable low back pressure. 【0008】 There is a need to provide an improved particulate filter for treating the exhaust stream from a gasoline engine that can provide a higher fresh filtration efficiency at a relatively low back pressure. SUMMARY OF THE INVENTION 【0009】 It is an object of the present invention to provide a particulate filter for treating the exhaust stream from a gasoline engine that provides a higher fresh filtration efficiency without suffering an unacceptable increase in back pressure. 【0010】 Surprisingly, it has been found that the object of the present invention is achieved by a particulate filter comprising a layer of inorganic particles comprising particles having a needle-like morphology within the inlet and / or outlet flow paths of the filter. 【0011】 Thus, in a first aspect, the present invention is a particulate filter comprising: - a substrate comprising a plurality of porous walls extending longitudinally to form a plurality of parallel flow paths extending from an inlet end to an outlet end, wherein a portion of the flow paths are inlet flow paths that are open at the inlet end and closed at the outlet end, and a portion of the flow paths are outlet flow paths that are closed at the inlet end and open at the outlet end; - a layer of inorganic particles loaded on the surface of the porous walls within the inlet and / or outlet flow paths; The layer of inorganic particles comprises inorganic particles in the form of needle-like crystals, providing a particulate filter. 【0012】 In a second aspect, the present invention is a method for manufacturing a particulate filter, comprising: - providing a substrate comprising a plurality of porous walls extending longitudinally to form a plurality of parallel flow paths extending from an inlet end to an outlet end, wherein a portion of the flow paths are inlet flow paths that are open at the inlet end and closed at the outlet end, and a portion of the flow paths are outlet flow paths that are closed at the inlet end and open at the outlet end; - applying an inorganic particle or a precursor thereof onto the surface of the porous walls within the inlet and / or outlet flow paths, wherein at least a portion of the inorganic particle or the precursor thereof is a particle in the form of a needle-like crystal. - Optionally, drying and / or firing, and A method is provided that includes 【0013】 In a third aspect, the present invention provides an exhaust gas treatment system that is disposed downstream of a gasoline engine and includes the particulate filter according to the first aspect or can be obtained from the method according to the second aspect, or the obtained particulate filter. 【0014】 In a fourth aspect, the present invention provides a method for treating an exhaust gas flow from a gasoline engine, the method including contacting the exhaust gas flow with the particulate filter according to the first aspect, or a particulate filter that can be obtained from the method according to the second aspect, or the obtained particulate filter, or the exhaust gas treatment system according to the third aspect. 【0015】 A particulate filter for treating exhaust gas from a gasoline engine, also referred to herein as a gasoline particulate filter, can provide improved fresh filtration efficiency compared to prior art counterparts, while no significant increase in back pressure was observed. 【Brief Description of the Drawings】 【0016】 【Figure 1】 An external view of a wall flow substrate having an inlet end and an outlet end is shown. 【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 shown. 【Figure 3A】 SEM images of Material A used in Comparative Examples 1, 2, and 3 are shown at magnifications of 5K and 10K, respectively. 【Figure 3B】 SEM images of Material A used in Comparative Examples 1, 2, and 3 are shown at magnifications of 5K and 10K, respectively. 【Figure 4A】 SEM images of Material B used in Examples 1, 3, and 4 of the present invention are shown at magnifications of 5K and 10K, respectively. 【Figure 4B】SEM images of Material B used in Examples 1, 3, and 4 of the present invention at magnifications of 5K and 10K, respectively, are shown. 【Figure 5A】 SEM images of Material C used in Example 2 of the present invention at magnifications of 5K and 10K, respectively, are shown. 【Figure 5B】 SEM images of Material C used in Example 2 of the present invention at magnifications of 5K and 10K, respectively, are shown. 【DETAILED DESCRIPTION OF THE INVENTION】 【0017】 The present invention will be described in detail below in this specification. It should be understood that the present invention can be implemented in many different ways and should not be construed as limited to the embodiments described herein. 【0018】 The singular forms "a", "an", and "the" include plural referents unless the context clearly dictates otherwise. Terms such as "comprise", "comprising", etc. are used interchangeably with "contain", "containing", etc. and should be construed in a non-limiting open-ended manner. That is, for example, additional components or elements may be present. The expression "consists of" or cognates may be subsumed under "comprises" or cognates. 【0019】 As used herein, the term "layer" in the context of, for example, a layer of inorganic particles is intended to mean a thin gas-permeable coating of material loaded onto a blank of a substrate or a pre-coated wall. The layer may be in the form of particles packed on the wall of the substrate and have gaps that allow gas to permeate therebetween. 【0020】 "D 10 ", "D 50 ", and "D 90The term "」 refers to the points at which the cumulative volume from the small particle size side reaches 10%, 50%, and 90% respectively in the cumulative particle size distribution, and has its ordinary meanings. The particle size distribution is measured by using a laser diffraction particle size distribution measuring device. 【0021】 The terms for platinum group metal (PGM) components such as "palladium component", "platinum component", and "rhodium component" are intended to describe the presence of each platinum group metal in any possible valence state, which may be, for example, a metal or metal oxide in a catalytically active form, or may be, for example, a metal compound, complex, etc. that decomposes during the calcination or use of the catalyst or is otherwise converted into a catalytically active form. 【0022】 The term "carrier" refers to a material in the form of particles for receiving and supporting one or more platinum group metal (PGM) compositions, as well as optionally one or more other compositions such as stabilizers, promoters, and binders. 【0023】 The term "acicular" is intended to refer to a crystal form similar to a spindle or needle-shaped crystal having a major axis length (i.e., crystal length) and a minor axis length (i.e., crystal thickness) such that the crystal length is much longer than the crystal thickness, generally at least 3 times longer. For example, the ratio of crystal length to crystal thickness may be in the range of 3 to 60, 5 to 40, or 8 to 30. 【0024】 The term "particles of acicular crystals" refers to particles that are an aggregate or agglomerate of acicular crystals and may include a single acicular crystal. 【0025】 In this specification, "g / ft 3 " or "g / in 3 " refers to the weight of a specific component, coat, or layer per unit volume of the substrate or substrate portion on which they are loaded. 【0026】 According to a first aspect of the present invention, a particulate filter, A substrate including a plurality of parallel flow channels extending from an inlet end to an outlet end, wherein a certain amount of the flow channels are inlet flow channels that are open at the inlet end and closed at the outlet end, and a certain amount of the flow channels are outlet flow channels that are closed at the inlet end and open at the outlet end, the substrate including a plurality of porous walls extending longitudinally to form the plurality of parallel flow channels. And a layer of inorganic particles loaded on the surface of the porous walls within the inlet flow channel and / or the outlet flow channel. A particulate filter is provided, wherein the layer of inorganic particles includes acicular crystalline inorganic particles. 【0027】 As used herein, the substrate refers to a structure suitable for withstanding the conditions encountered in the exhaust flow from a combustion engine, which can itself function as a particulate filter and can optionally be loaded with functional materials, such as a filtration improvement layer like the layer of inorganic particles described herein, and any other layers. 【0028】 The substrate includes a plurality of porous walls extending longitudinally to form a plurality of parallel flow channels extending from an inlet end to an outlet end, wherein a certain amount of the flow channels are inlet flow channels that are open at the inlet end and closed at the outlet end, and a certain amount of the flow channels different from the inlet flow channels are outlet flow channels that are closed at the inlet end and open at the outlet end. The configuration of the substrate, also referred to as a wall-flow substrate, requires the engine exhaust in the inlet flow channel to flow through the porous walls into the outlet flow channel of the substrate and reach the outlet end. 【0029】 Generally, the substrate may exhibit a honeycomb structure in which the alternating flow channels are blocked by plugs at both ends. 【0030】 The porous walls of the substrate are generally made of a ceramic material or a metal material. 【0031】 Suitable ceramic materials used to construct the substrate may include any suitable refractory material, such as cordierite, mullite, cordierite-alumina, silicon carbide, silicon nitride, zirconia, mullite, spodumene, alumina-silica-magnesia, zirconium silicate, magnesium silicate, sillimanite, petalite, alumina, aluminum titanate, and aluminosilicate. Typically, the porous walls of the substrate are made of cordierite or silicon carbide. 【0032】 Suitable metallic materials for constructing the substrate may include heat-resistant metals and metal alloys such as titanium and stainless steel, and other alloys in which iron is a substantial or major component. Such alloys may contain one or more of nickel, chromium, and / or aluminum, and the total amount of these metals may advantageously be at least 15% by weight of the alloy, for example, 10 - 25% by weight of chromium, 3 - 8% by weight of aluminum, and up to 20% by weight of nickel. The alloy may contain small or trace amounts of one or more metals such as manganese, copper, vanadium, titanium, etc. The surface of the metal substrate may be oxidized at a high temperature of, for example, 1000 °C or higher to form an oxide layer on the surface of the substrate to improve the corrosion resistance of the alloy and to promote the adhesion of any coating layer to the metal surface. 【0033】 The closed-end flow path is plugged with a plug of sealant material. Any suitable sealant material may be used without limitation. 【0034】 The flow paths of the substrate can be of any suitable cross-sectional shape and size, such as circular, elliptical, triangular, rectangular, square, hexagonal, trapezoidal, or other polygonal. The substrate may have up to 700 flow paths (i.e., cells) per square inch of cross-section. For example, the substrate may have 100 - 500 cells per square inch (cpsi), typically 200 - 400 cpsi. The walls of the substrate may have various thicknesses, and a typical range is 2 mils to 0.1 inch. Preferably, the substrate has an equal number of inlet flow paths as the number of outlet flow paths, and the flow paths are uniformly distributed throughout the substrate. 【0035】 Figures 1 and 2 show a typical wall-flow substrate including a plurality of inlet and outlet flow channels. 【0036】 Figure 1 shows an external view of a wall-flow substrate having an inlet end (01) where the exhaust gas flow (13) enters the substrate and an outlet end (02) where the treated exhaust gas exits. The alternating flow channels are plugged with plugs to form a checkerboard pattern at the inlet end (01) as shown and an opposite checkerboard pattern at the outlet end (02) not shown. 【0037】 Figure 2 schematically shows a longitudinal cross-sectional view of a wall-flow substrate including a first plurality of flow channels (11) that are open at the inlet end (01) and closed at the outlet end (02), and a second plurality of flow channels (12) that are open at the outlet end (02) and closed at the inlet end (01). The flow channels are preferably parallel to each other to provide a constant wall thickness between the flow channels. The exhaust gas flow entering the first plurality of flow channels from the inlet end cannot exit the substrate without diffusing through the porous wall (10) into the second plurality of flow channels. 【0038】 The particulate filter according to the present invention may comprise a layer of inorganic particles loaded on the surface of the porous wall in the inlet flow channel and / or the outlet flow channel. In other words, the layer of inorganic particles may be loaded on the porous wall in only the inlet flow channel, only the outlet flow channel, or both the inlet flow channel and the outlet flow channel. In particular, the layer of inorganic particles may be loaded on the porous wall in only the inlet flow channel, or both the inlet flow channel and the outlet flow channel, more preferably only the inlet flow channel. 【0039】 The layer of inorganic particles is intended to be loaded on the surface of the porous wall within the inlet and / or outlet flow channels, which is also referred to as an "on-wall" coat, but it will be understood that a small amount of the inorganic particles may penetrate into the pores within the porous wall. 【0040】 According to the present invention, the inorganic particles may be particles of a non-PGM inorganic material. The non-PGM inorganic material may be, for example, alumina, hydrated alumina, boehmite, zirconia, ceria, silica, titania, magnesium oxide, zinc oxide, zinc carbonate, calcium oxide, calcium carbonate, silicate zeolite, aluminosilicate zeolite, or a combination or composite thereof. 【0041】 Therefore, the acicular inorganic particles may be particles of acicular crystals of a non-PGM inorganic material selected from alumina, hydrated alumina, boehmite, zirconia, ceria, silica, titania, magnesium oxide, zinc oxide, zinc carbonate, calcium oxide, calcium carbonate, silicate zeolite, aluminosilicate zeolite, or a combination or composite thereof. 【0042】 Preferably, the inorganic particles, particularly the acicular inorganic particles, are particles of a non-PGM inorganic material selected from alumina, hydrated alumina, boehmite, silica, zinc oxide, zirconia, or a combination or composite thereof, more preferably alumina, boehmite, or a combination thereof. 【0043】 The layer of inorganic particles may optionally contain a PGM component such as a palladium component and / or a platinum component. When present, the PGM component may be supported on the particles of the non-PGM inorganic material as described above, or may exist separately from the particles of the acicular non-PGM inorganic material. 【0044】 In the present specification, the layer of inorganic particles loaded on the porous wall in the inlet and / or outlet flow path of the substrate particularly refers to a layer that exhibits little or no TWC activity, preferably no TWC activity. However, when one or more PGM components are contained in the inorganic particles, it may exhibit a specific catalytic activity. 【0045】 In some embodiments, the layer of inorganic particles does not contain a PGM component. Preferably, the layer of inorganic particles can consist mainly or substantially of inorganic particles having acicular crystals of a non-PGM inorganic material selected from alumina, hydrated alumina, boehmite, zirconia, ceria, silica, titania, magnesium oxide, zinc oxide, zinc carbonate, calcium oxide, calcium carbonate, silicate zeolite, aluminosilicate zeolite, or a combination or composite thereof, among which alumina, hydrated alumina, boehmite, silica, zinc oxide, zirconia, or a combination or composite thereof is more preferred, and alumina and boehmite are most preferred. 【0046】 As used herein, any reference to "consisting mainly of" within the context of the layer of inorganic particles is intended to mean that the layer of inorganic particles contains a major amount, i.e., more than 50% by volume, of the specified acicular crystal inorganic particles, 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. 【0047】 As used herein, any reference to "consisting essentially of" within the context of the layer of inorganic particles is intended to mean that the layer of inorganic particles contains an unintentional added amount of inorganic particles other than the specified acicular crystal inorganic particles. As used herein, the term "unintentional added amount" is intended to refer to 1% by volume or less, 0.5% by volume or less, 0.1% by volume or less, or 0.05% by volume or less. 【0048】 The inventors have found that the acicular crystal form of the inorganic particles has an advantageous effect on the fresh filtration efficiency and / or back pressure of the particulate filter. 【0049】 The acicular crystals can have a crystal length of 20 micrometers (μm) or less, 10 μm or less, or 8 μm or less as measured by a scanning electron microscope (SEM). In addition, the acicular crystals can have a crystal thickness of 1000 nanometers (nm) or less, 500 nm or less, or 300 nm or less as measured by a scanning electron microscope (SEM). 【0050】 In some embodiments, the acicular crystals may have a crystal length of 20 μm or less and a crystal thickness of 1000 nm or less, preferably a crystal length of 10 μm or less and a crystal thickness of 500 nm or less, more preferably a crystal length of 8 μm or less and a crystal thickness of 300 nm or less. 【0051】 The inorganic particles useful in the present invention, particularly the acicular crystal inorganic particles, may have a D of 50 microns (μm) or less, 30 μm or less, or 20 μm or less. 90 The inorganic particles useful in the present invention, particularly the acicular crystal inorganic particles, may have a D in the range of 3 to 20 μm, 3 to 15 μm, or 5 to 10 μm. 50 The inorganic particles useful in the present invention, particularly the acicular crystal inorganic particles, may have a D of 8 μm or less, 5 μm or less, or 2 μm or less. 10 and may have. 【0052】 The particulate filter according to the present invention may include a layer of inorganic particles at a loading of 0.005 to 0.83 g / in 3 (i.e., about 0.3 to 50 g / L), 0.01 to 0.33 g / in 3 (i.e., about 0.6 to 20 g / L), or 0.015 to 0.1 g / in 3 (i.e., about 0.9 to 6 g / L). 【0053】 The layer of inorganic particles may be applied onto the surface of the porous wall of the substrate by any known process such as a dry coating process and a washcoat process. 【0054】 The dry coating process is well-known and generally involves blowing inorganic particles or a suitable precursor thereof in particle form into the flow path of the substrate from the open end by a carrier gas stream, optionally drying the coated substrate, and optionally firing it. By this process, no liquid carrier is used. The inorganic particles are typically distributed on the surface of the porous wall of the flow path in the form of a particle bed. 【0055】 It will be understood that the inorganic particles or suitable precursors thereof to be applied maintain their crystalline form after firing the coated substrate. In other words, firing, when carried out, does not result in a change in the crystalline form of the inorganic particles. 【0056】 In some embodiments, the inorganic particles or suitable precursors thereof may be blown into the inlet flow path from the open end towards the closed end. The particle bed formed in the inlet flow path may be disposed on the porous wall of the inlet flow path or may be disposed relative to a plug that blocks the flow path. The particulate bed, i.e., the layer of inorganic particles, is gas permeable, which contributes to the capture of particulate matter (PM) in the exhaust flow and allows gaseous contaminants in the exhaust flow to permeate therethrough. 【0057】 The layer of inorganic particles in the form of a particle bed may extend along the porous wall of the flow path into which the inorganic particles are loaded. It will be understood that the particle bed may extend along the entire length of the porous wall of the flow path or only along a part of the length of the porous wall of the flow path. 【0058】 The washcoating process is also well known and generally involves coating a slurry containing inorganic particles or suitable precursors thereof and any auxiliaries in a liquid solvent (e.g., water) into the flow path of the substrate from the open end, drying the coated substrate, and optionally firing. The layer of inorganic particles applied by washcoating may be in the form of a porous coating and may extend along the porous wall of the flow path into which the inorganic particles are loaded. Also, the porous coating may extend along the entire length of the porous wall of the flow path or only along a part of the length of the porous wall of the flow path. 【0059】 The particulate filter according to the present invention may further include a TWC coat on at least a part of the inlet flow path and / or the outlet flow path of the substrate. In particular, the TWC coat is present on both the inlet flow path and the outlet flow path of the substrate. 【0060】 The TWC coat is typically in the form of a washcoat containing a TWC composition, also referred to as an "in-wall" coat. 【0061】 The TWC coat is intended to be loaded into the pores of the porous walls of the flow channels, but it will be understood that a significant amount of the TWC composition may also be found on the surface of the porous walls within the coated flow channels. 【0062】 There are no particular restrictions on the TWC composition useful for the TWC coat contained in the particulate filter. Typically, the TWC composition contains a platinum group metal component as a catalytically active species, such as a rhodium component, and one or both of a platinum component and a palladium component, which are supported on carrier particles. Materials useful as carriers may be refractory metal oxides, oxygen storage components, and any combination thereof. 【0063】 Examples of refractory metal oxides include, but are not limited to, alumina, lanthana-doped alumina, barium-doped alumina, ceria-doped alumina, zirconia-doped alumina, ceria-zirconia-doped alumina, lanthana-zirconia-doped alumina, barium-lanthana-doped alumina, barium-ceria-doped alumina, barium-zirconia-doped alumina, barium-lanthana-neodymia-doped alumina, lanthana-ceria-doped alumina, and any combination thereof. 【0064】 Examples of oxygen storage components (OSC) may include, but are not limited to, reducible rare earth metal oxides such as ceria. The oxygen storage component may also include one or more of lanthana, praseodymia, neodymia, europia, samaria, ytterbia, yttria, zirconia, and hafnia to form a composite oxide with ceria. In particular, the oxygen storage component is selected from ceria-zirconia composite oxides and stabilized ceria-zirconia composite oxides. 【0065】 The particulate filter according to the present invention is 0.1 to 5.0 g / in3 (i.e., about 6.1 to 305.1 g / L), or 0.5 to 3.0 g / in 3 (i.e., about 30.5 to 183.1 g / L), or 0.8 to 2 g / in 3 (i.e., about 49 to 122 g / L) loading amount may include a TWC coat. 【0066】 The TWC coat may include PGM components with a total loading amount of 1.0 to 50.0 g / ft 3 (i.e., about 0.04 to 1.8 g / L), or 5.0 to 20.0 g / ft 3 (i.e., about 0.18 to 0.71 g / L) calculated as each PGM element. 【0067】 The TWC coat may be applied onto the substrate by any known process, typically by a washcoating process. The washcoating process is generally carried out by coating a slurry containing TWC catalyst particles of supported PGM components and optionally promoters in a solvent (such as water), drying the coated substrate, and firing. 【0068】 The TWC coat, if present, is applied onto the substrate before loading the layer of inorganic particles as described above. The TWC coat, if present, may also be referred to as an undercoat, i.e., it may be under the layer of inorganic particles. 【0069】 In some exemplary embodiments, the particulate filter according to the present invention comprises - a substrate including a plurality of parallel flow channels extending from an inlet end to an outlet end, wherein a certain amount of the flow channels are inlet flow channels that are open at the inlet end and closed at the outlet end, and a certain amount of the flow channels are outlet flow channels that are closed at the inlet end and open at the outlet end, and including a plurality of porous walls extending longitudinally to form the plurality of parallel flow channels, - a layer of inorganic particles loaded on at least the surface of the porous walls within the inlet flow channels, - optionally, including a TWC coat, preferably a washcoat containing a TWC composition, A particulate filter is provided in which the layer of inorganic particles comprises acicular inorganic particles. 【0070】 In a further exemplary embodiment, the particulate filter according to the present invention comprises - a substrate comprising a plurality of parallel flow channels extending from an inlet end to an outlet end, a certain amount of the flow channels being inlet flow channels that are open at the inlet end and closed at the outlet end, and a certain amount of the flow channels being outlet flow channels that are closed at the inlet end and open at the outlet end, the plurality of parallel flow channels being formed by a plurality of porous walls extending longitudinally, - a layer of inorganic particles loaded on at least the surface of the porous walls within the inlet flow channels, - optionally, a washcoat comprising a TWC composition, wherein the layer of inorganic particles comprises acicular inorganic particles in an amount of 75% by volume or more, 85% by volume or more, 90% by volume or more, or even 95% by volume or more, based on the total volume of all the inorganic particles in the layer of inorganic particles. 【0071】 In some other exemplary embodiments, the particulate filter according to the present invention comprises - a substrate comprising a plurality of parallel flow channels extending from an inlet end to an outlet end, a certain amount of the flow channels being inlet flow channels that are open at the inlet end and closed at the outlet end, and a certain amount of the flow channels being outlet flow channels that are closed at the inlet end and open at the outlet end, the plurality of parallel flow channels being formed by a plurality of porous walls extending longitudinally, - a layer of inorganic particles loaded on at least the surface of the porous walls within the inlet flow channels, - optionally, a washcoat comprising a TWC composition, wherein the layer of inorganic particles consists mainly or substantially of acicular inorganic particles of a non-PGM inorganic material. 【0072】 In some further exemplary embodiments, the particulate filter according to the present invention comprises - A plurality of parallel flow paths extending from an inlet end to an outlet end, wherein a certain amount of the flow paths are inlet flow paths that are open at the inlet end and closed at the outlet end, and a certain amount of the flow paths are outlet flow paths that are closed at the inlet end and open at the outlet end, and a substrate including a plurality of porous walls extending longitudinally to form the plurality of parallel flow paths; - A layer of inorganic particles loaded on at least the surface of the porous wall within the inlet flow path; - Optionally, a washcoat including a TWC composition; The layer of inorganic particles consists mainly or substantially of acicular crystal inorganic particles of a non-PGM inorganic material selected from alumina, hydrated alumina, boehmite, silica, zinc oxide, zirconia, or a combination or composite thereof. 【0073】 In some specific embodiments, the particulate filter according to the present invention - A plurality of parallel flow paths extending from an inlet end to an outlet end, wherein a certain amount of the flow paths are inlet flow paths that are open at the inlet end and closed at the outlet end, and a certain amount of the flow paths are outlet flow paths that are closed at the inlet end and open at the outlet end, and a substrate including a plurality of porous walls extending longitudinally to form the plurality of parallel flow paths; - A layer of inorganic particles loaded on at least the surface of the porous wall within the inlet flow path; - Optionally, a washcoat including a TWC composition; The layer of inorganic particles consists mainly or substantially of acicular crystal inorganic particles of a non-PGM inorganic material selected from alumina, hydrated alumina, boehmite, silica, zinc oxide, zirconia, or a combination or composite thereof, and the acicular crystals have a crystal length of 20 μm or less and a crystal thickness of 1000 nm or less. 【0074】 In some preferred specific embodiments, the particulate filter according to the present invention - A plurality of parallel flow paths extending from an inlet end to an outlet end, wherein a certain amount of the flow paths are inlet flow paths that are open at the inlet end and closed at the outlet end, and a certain amount of the flow paths are outlet flow paths that are closed at the inlet end and open at the outlet end, and a substrate including a plurality of porous walls extending longitudinally to form the plurality of parallel flow paths; At least a layer of inorganic particles loaded on the surface of the porous wall in the inlet flow path, - Optionally, including a washcoat containing a TWC composition, The layer of inorganic particles consists mainly or substantially of acicular inorganic particles of a non-PGM inorganic material selected from alumina, hydrated alumina, boehmite, silica, or a combination or composite thereof, and the acicular crystals have a crystal length of 10 μm or less and a crystal thickness of 500 nm or less, more preferably a crystal length of 8 μm or less and a crystal thickness of 300 nm or less. 【0075】 In each of the above exemplary and specific embodiments, the inorganic particles preferably consist substantially of acicular inorganic particles having at least one, preferably all, of the following particle size characteristics. - D of 30 μm or less 90 、 - D of 3 to 15 μm 50 、and - D of 5 μm or less 10 。 【0076】 More preferably, the inorganic particles consist substantially of acicular inorganic particles having at least one, preferably all, of the following particle size characteristics. - D of 20 μm or less 90 、 - D of 5 to 10 μm 50 、and - D of 2 μm or less 10 。 【0077】 In the exemplary and specific embodiments as described above, the layer of inorganic particles preferably does not contain a PGM component. 【0078】 In the exemplary and specific embodiments as described above, the particulate filter preferably includes a washcoat containing a TWC composition. 【0079】 The particulate filter may be housed within a shell having an inlet and an outlet for the exhaust flow, which is operably associated with and may be in fluid communication with other parts of the engine exhaust system. 【0080】 According to a second aspect of the present invention, a method for manufacturing a particulate filter, comprising: - providing a substrate comprising a plurality of porous walls extending longitudinally to form a plurality of parallel flow channels extending from an inlet end to an outlet end, wherein a certain amount of the flow channels are inlet flow channels that are open at the inlet end and closed at the outlet end, and a certain amount of the flow channels are outlet flow channels that are closed at the inlet end and open at the outlet end; - applying inorganic particles or a precursor thereof onto the surface of the porous walls within the inlet flow channel and / or the outlet flow channel, wherein at least a portion of the inorganic particles or the precursor thereof are particles of acicular crystals; - optionally, drying and / or firing; is provided. 【0081】 The inorganic particles or a precursor thereof may be applied onto the surface of the porous walls by a dry coating process or a wash coating as described above in the first aspect, preferably by a dry coating process. 【0082】 In some embodiments, the method for manufacturing a particulate filter further comprises applying a TWC coat to at least a portion of the porous walls of the inlet and / or outlet flow channels of the substrate before applying the inorganic particles onto the surface of the porous walls. The TWC coat may be applied by the wash coating process described above. 【0083】 Any general descriptions and selections described above for the layer of inorganic particles and the TWC coat in the first aspect are applicable herein by reference. 【0084】 In some embodiments, more 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 the acicular crystal inorganic particles specified herein. In particular, the inorganic particles applied consist essentially of acicular crystal inorganic particles. 【0085】 According to a third aspect, there is provided an exhaust gas treatment system including the particulate filter described in the first aspect or a particulate filter that can be obtained or has been obtained from the method described in the second aspect, which is disposed downstream of a gasoline engine. 【0086】 According to a fourth aspect, there is provided a method for treating an exhaust gas flow from a gasoline engine, the method including contacting the exhaust gas flow with the particulate filter described in the first aspect, or a particulate filter that can be obtained or has been obtained from the method described in the second aspect, or the exhaust gas treatment system described in the third aspect. 【0087】 Embodiments Various embodiments are listed below. It will be understood that the embodiments listed below can be combined with all aspects and other embodiments in accordance with the scope of the present invention. 【0088】 Embodiment 1. A particulate filter, - a substrate including a plurality of parallel flow paths extending from an inlet end to an outlet end, a certain amount of the flow paths being inlet flow paths that are open at the inlet end and closed at the outlet end, and a certain amount of the flow paths being outlet flow paths that are closed at the inlet end and open at the outlet end, the plurality of parallel flow paths being formed by a plurality of porous walls extending longitudinally, and a layer of inorganic particles loaded on the surface of the porous walls in the inlet flow path and / or the outlet flow path, preferably at least in the inlet flow path, wherein the layer of inorganic particles includes acicular crystalline inorganic particles, the particulate filter. 【0089】 Embodiment 2. The particulate filter according to Embodiment 1, wherein the layer of inorganic particles includes acicular crystalline inorganic particles in an amount of 50% by volume or more, 75% by volume or more, 85% by volume or more, 90% by volume or more, or even 95% by volume or more. 【0090】 Embodiment 3. The particulate filter according to Embodiment 2, wherein the layer of inorganic particles consists essentially of acicular crystalline inorganic particles. 【0091】 Embodiment 4. The particulate filter according to any one of Embodiments 1 to 3, wherein the layer of inorganic particles does not exhibit ternary conversion catalytic activity. 【0092】 Embodiment 5. The particulate filter according to any one of Embodiments 1 to 4, wherein the layer of inorganic particles does not contain a PGM component. 【0093】 Embodiment 6. The particulate filter according to any one of Embodiments 1 to 5, wherein the inorganic particles, particularly the acicular crystal inorganic particles, are particles of a non-PGM inorganic material selected from particularly alumina, hydrated alumina, boehmite, zirconia, ceria, silica, titania, magnesium oxide, zinc oxide, zinc carbonate, calcium oxide, calcium carbonate, silicate zeolite, aluminosilicate zeolite, or a combination or composite thereof. 【0094】 Embodiment 7. The particulate filter according to Embodiment 6, wherein the non-PGM inorganic material is selected from alumina, hydrated alumina, boehmite, silica, zinc oxide, zirconia, or a combination or composite thereof. 【0095】 Embodiment 8. The particulate filter according to any one of Embodiments 1 to 7, wherein the acicular crystals have a crystal length of 20 μm or less, 10 μm or less, or 8 μm or less as measured by a scanning electron microscope (SEM). 【0096】 Embodiment 9. The particulate filter according to any one of Embodiments 1 to 8, wherein the acicular crystals have a crystal thickness of 1000 nm or less, 500 nm or less, or 300 nm or less as measured by a scanning electron microscope (SEM). 【0097】 Embodiment 10. The inorganic particles, particularly the acicular crystal inorganic particles, have a D 90 of 50 microns (μm) or less, 30 μm or less, or 20 μm or less, and the particulate filter according to any one of Embodiments 1 to 9. 【0098】 Embodiment 11. The particulate filter according to any one of Embodiments 1 to 10, further comprising a three-way conversion catalyst (TWC) coating, preferably a washcoat containing a TWC composition. 【0099】 Embodiment 12. The particulate filter according to Embodiment 11, wherein the three-way conversion catalyst coating is in at least a part of the inlet flow path and / or the outlet flow path of the substrate. 【0100】 Embodiment 13. The particulate filter according to any one of Embodiments 1 to 12, comprising a layer of inorganic particles in a loading amount of 0.3 to 50 g / L, 0.6 to 20 g / L, or 0.9 to 6 g / L. 【0101】 Embodiment 14. The particulate filter according to any one of Embodiments 1 to 14, which is a gasoline particulate filter. 【0102】 Embodiment 15. A method for manufacturing the particulate filter according to any one of Embodiments 1 to 14, comprising: - providing a substrate including a plurality of porous walls extending longitudinally to form a plurality of parallel flow paths, wherein a certain amount of the flow paths are inlet flow paths that are open at the inlet end and closed at the outlet end, and a certain amount of the flow paths are outlet flow paths that are closed at the inlet end and open at the outlet end; - applying inorganic particles or a precursor thereof on the surface of the porous walls in the inlet flow path and / or the outlet flow path, wherein at least a part of the inorganic particles or the precursor thereof are needle-shaped crystal particles; - optionally, drying and / or firing. The method comprising the above steps. 【0103】 Embodiment 16. The method according to Embodiment 15, wherein the inorganic particles are applied by a dry coating process or a washcoating process, preferably by a dry coating process. 【0104】 Exhaust treatment system that can be obtained from the particulate filter according to any one of Embodiments 1 to 14, or the method according to any one of Embodiments 13 to 16, or includes the obtained particulate filter and is disposed downstream of a gasoline engine. 【0105】 Embodiment 18. A method for treating an exhaust gas flow from a gasoline engine, the method comprising contacting the exhaust gas flow with the particulate filter according to any one of Embodiments 1 to 14, or the particulate filter that can be obtained from the method according to Embodiment 15 or 16, or the exhaust treatment system according to Embodiment 17. 【Examples】 【0106】 Aspects of the present invention are more fully illustrated by the following examples, which are described to illustrate specific aspects of the present invention and should not be construed as limiting them. 【0107】 I. Preparation of Particulate Filter Materials and Characterization The materials used for the preparation of the inorganic particle layer of the particulate filter in the examples are summarized in Table 1 below. The particle size was measured by a Sympatec HELOS laser diffraction particle size analyzer. The surface area and pore volume were measured by a Micromeritics ASAP 2420 surface area and porosity analyzer equipped with a BET model under 77K nitrogen adsorption. The morphology and crystal size were determined by a Zeiss Supra 55 scanning electron microscope (SEM). 【0108】 【Table 1】 * : Aluminum oxyhydroxide, which is converted to alumina by firing ** : It was determined by SEM that the morphology was maintained after firing of Materials A, B, and C at 550 °C. 【0109】 Reference Example 1 (R1) The gasoline particulate filter cordierite substrate S1 was used as a reference filter (blank filter), which had a size of 118.4 mm (D) × 127 mm (L), a volume of 1.4 L (about 85.4 in 3 ), a cell density (cpsi) of 300 cells per square inch, a wall thickness of 8 mils, and a porosity of 65% determined by mercury intrusion measurement. 【0110】 Reference Example 2 (R2) A particulate filter having a TWC coat was prepared from the same filter substrate as the blank filter of Reference Example 1 (substrate S1) by applying a TWC wash coat to both the inlet and outlet flow channels of the blank filter. 【0111】 24.21 g of a 9.68 wt% rhodium nitrate aqueous solution was impregnated onto 255 g of a high surface area gamma alumina powder in a planetary mixer (P-mixer) to form a wet powder while achieving initial wetting. 14.37 g of a 16.31 wt% diethanolamine hexahydroxyplatinate aqueous solution was impregnated onto 712 g of a ceria / zirconia (40% ceria) composite powder in a planetary mixer (P-mixer) to form a wet powder while achieving initial wetting. An aqueous slurry was formed by mixing the above two wet powders with 1124 g of deionized water, to which 78 g of barium nitrate and 68 g of a 21.3 wt% zirconium nitrate aqueous solution were added. The pH of the slurry was adjusted to 3.6 with nitric acid. The slurry was ground to a particle size D 90 to 4.5 μm, then coated into the inlet flow channel of the blank filter at a wash coat loading of 50%, and coated into the outlet flow channel of the blank filter at the remaining 50% wash coat loading. The coated substrate was then dried at a temperature of 150 °C for 1 hour and then calcined at a temperature of 550 °C for 1 hour. 【0112】 Approximately 1.23 g / in 3 (75 g / L) of wash coat loading and approximately 10.0 g / ft 3An in-wall TWC coat was obtained using a total PGM loading of (0.35 g / L) and a Pt / Rh ratio of 5 / 5. 【0113】 Reference Example 3 (R3) As a blank filter, a cordierite substrate S2 having a size of 143.8 mm (D) × 152.4 mm (L), a volume of 2.48 L (about 151.3 in 3 ), a cell density (cpsi) of 300 cells per square inch, a wall thickness of 8 mils, and a porosity of 65% determined by mercury intrusion measurement was used, and the same process as described in Reference Example 2 was applied to prepare a particulate filter having a TWC coat. 【0114】 Comparative Example 1 (C1) A particulate filter having a TWC coat and a layer of inorganic particles having an irregular shape was prepared. 【0115】 First, a particulate filter having a TWC coat was prepared by applying the same process as in Reference Example 2 to the same blank filter as described in Reference Example 1. Next, Material A, alumina powder was mixed with a carrier gas and blown into the inlet flow path of the filter at a flow rate of 600 m 3 / h at room temperature. After coating, the filter having a layer of inorganic particles in the inlet flow path was fired at a temperature of 550 °C for 1 hour. The loading amount of the layer of inorganic particles was 5 g / L (0.082 g / in 3 ). 【0116】 Comparative Example 2 (C2) A particulate filter having a TWC coat and a layer of inorganic particles having an irregular shape was prepared. 【0117】 First, a particulate filter having a TWC coat was prepared by applying the same process as in Reference Example 2 to the same blank filter as described in Reference Example 3. Next, Material A, alumina powder was mixed with a carrier gas and blown into the inlet flow path of the filter at a flow rate of 600 m 3It was blown into the inlet channel of the filter at a flow rate of / h. After coating, the filter having a layer of inorganic particles in the inlet channel was fired at a temperature of 550 °C for 1 hour. The loading amount of the layer of inorganic particles was 1 g / L (0.016 g / in 3 ) 【0118】 Comparative Example 3 (C3) A particulate filter having a TWC coat and a layer of inorganic particles having an irregular shape was prepared. 【0119】 The particulate filter was prepared in the same manner as in Comparative Example 2, except that the loading amount of the layer of inorganic particles was 2 g / L (0.033 g / in 3 ) 【0120】 Example 1 (E1) of the present invention A particulate filter having a TWC coat and a layer of inorganic particles having a needle-like morphology was prepared. 【0121】 First, a particulate filter having a TWC coat was prepared by applying the same process as in Reference Example 2 to the same blank filter as described in Reference Example 1. Next, Material B, boehmite powder was mixed with a carrier gas and blown into the inlet channel of the filter at a flow rate of 600 m 3 / h at room temperature. After coating, the filter having a layer of inorganic particles in the inlet channel was fired at a temperature of 550 °C for 1 hour. The loading amount of the layer of inorganic particles was 3 g / L (0.049 g / in 3 ) 【0122】 Example 2 (E2) of the present invention A particulate filter having a TWC coat and a layer of inorganic particles having a needle-like morphology was prepared. 【0123】 First, a particulate filter having a TWC coat was prepared by applying the same process as in Reference Example 2 to the same blank filter as described in Reference Example 1. Next, Material C, alumina powder was mixed with a carrier gas and blown into the inlet channel of the filter at a flow rate of 600 m 3It was blown into the inlet channel of the filter at a flow rate of / h. After coating, the filter having a layer of inorganic particles in the inlet channel was calcined at a temperature of 550 °C for 1 hour. The loading amount of the layer of inorganic particles was 3 g / L (0.049 g / in 3 ) 【0124】 Example 3 (E3) of the present invention A particulate filter having a TWC coat and a layer of inorganic particles having a needle-like form was prepared. 【0125】 First, a particulate filter having a TWC coat was prepared by applying the same process as in Reference Example 2 to the same blank filter as described in Reference Example 3. Next, Material B and boehmite powder were mixed with a carrier gas and blown into the inlet channel of the filter at a flow rate of 600 m 3 / h. After coating, the filter having a layer of inorganic particles in the inlet channel was calcined at a temperature of 550 °C for 1 hour. The loading amount of the layer of inorganic particles was 1 g / L (0.016 g / in 3 ) 【0126】 Example 4 (E4) of the present invention A particulate filter having a TWC coat and a layer of inorganic particles having a needle-like or fibrous form was prepared. 【0127】 The particulate filter was prepared in the same manner as in Example 3 of the present invention, except that the loading amount of the layer of inorganic particles was 2 g / L (0.033 g / in 3 ) 【0128】 II. Filtration performance II.1 Back pressure The particulate filters of all examples were investigated for back pressure (BP) by measurement using a SuperFlow SF-1020 flow bench under a cold air flow of 600 m 3 / h. 【0129】 II.2 Fresh filtration efficiency In accordance with the standard procedures defined in "BS EN ISO 29463-5:2018 - Part 5: Test method for filter elements", on a fixed air filter performance test bench with a cold air flow of 600 m 3 / h, using di(2-ethylhexyl) sebacate aerosol as particles, the filtration efficiency of the particulate filter from the above examples in the fresh state (0 km, or unused state) was measured. The particle number (PN) of particles in the range of 0.10 - 0.15 μm was recorded by a PN counter for both the upstream and downstream of the filter being tested. The fresh filtration efficiency (FFE) was calculated according to the following formula 【0130】 【Equation】 【0131】 The test results of each particulate filter from the above examples are summarized in Table 2 below. 【0132】 【Table 2】 【0133】 From the comparison of Reference Example 1 (R1) and Reference Example 2 (R2), it can be seen that the particulate filter with a TWC coat has a higher back pressure (BP) and a lower fresh filtration efficiency (FFE) than the blank filter, which may be due to the penetration of the TWC component into the porous walls of the substrate of the particulate filter. The fresh filtration efficiency (FFE) can be improved by applying a layer of alumina particles as shown in Comparative Example 1 (C1), along with an acceptable increase in back pressure. 【0134】 Surprisingly, the fresh filtration efficiency (FFE) can be improved to a greater extent by applying a layer of particles having a needle-like morphology as shown in Example 1 (E1) of the present invention, which exhibits a fresh filtration efficiency of 96% with an acceptable increase in backpressure. In particular, the particulate filter of Example 1 (E1) of the present invention exhibits a much higher fresh filtration efficiency at a lower backpressure than that of Comparative Example 1 (C1). Also, the particulate filter of Example 2 (E2) of the present invention exhibits a higher fresh filtration efficiency (FFE) at a much lower backpressure than that of Comparative Example 2 (C2). 【0135】 The surprising improvement provided by using inorganic particles having a needle-like morphology can also be observed from the comparison between Examples 3 and 4 of the present invention and Comparative Examples 2 and 3. In particular, the particulate filter of Example 3 (E3) of the present invention exhibits a significantly higher fresh filtration efficiency than that of Comparative Example 2 (C2) at the same backpressure. Also, the particulate filter of Example 4 (E4) of the present invention exhibits a significantly higher fresh filtration efficiency than that of Comparative Example 3 (C3) at the same backpressure. 【0136】 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 can be made to the method 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

[Claim 1] It is a particulate filter, - A substrate comprising a plurality of porous walls extending longitudinally to form a plurality of parallel channels, wherein a portion of the channels is an inlet channel that is open at the inlet end and closed at the outlet end, and a portion of the channels is an outlet channel that is closed at the inlet end and open at the outlet end, The inlet channel and / or outlet channel, preferably a layer of inorganic particles loaded on the surface of the porous wall in at least the inlet channel, A particulate filter in which the layer of inorganic particles contains needle-shaped crystalline inorganic particles. [Claim 2] The particulate filter according to claim 1, wherein the inorganic particle layer contains 50 volume% or more, 75 volume% or more, 85 volume% or more, 90 volume% or more, and even 95 volume% or more of the needle-shaped crystalline inorganic particles. [Claim 3] The particulate filter according to claim 2, wherein the layer of inorganic particles is substantially composed of the needle-shaped crystalline inorganic particles. [Claim 4] The particulate filter according to any one of claims 1 to 3, wherein the layer of inorganic particles does not exhibit ternary conversion catalytic activity. [Claim 5] The particulate filter according to any one of claims 1 to 3, wherein the layer of inorganic particles does not contain PGM components. [Claim 6] The particulate filter according to any one of claims 1 to 3, wherein the inorganic particles, in particular the needle-shaped crystalline inorganic particles, are particles of a non-PGM inorganic material selected from alumina, hydrated alumina, boehmite, zirconia, ceria, silica, titania, magnesium oxide, zinc oxide, zinc carbonate, calcium oxide, calcium carbonate, silicate zeolite, aluminosilicate zeolite, or combinations or composites thereof. [Claim 7] The particulate filter according to claim 6, wherein the non-PGM inorganic material is selected from alumina, hydrated alumina, boehmite, silica, zinc oxide, zirconia, or a combination or composite thereof. [Claim 8] The particulate filter according to any one of claims 1 to 3, wherein the needle-shaped crystals have a crystal length of 20 μm or less, 10 μm or less, or 8 μm or less as measured by a scanning electron microscope (SEM). [Claim 9] The particulate filter according to any one of claims 1 to 3, wherein the needle-shaped crystals have a crystal thickness of 1000 nm or less, 500 nm or less, or 300 nm or less as measured by a scanning electron microscope (SEM). [Claim 10] The inorganic particles, particularly the needle-shaped crystalline inorganic particles, have a diameter of 50 μm or less, 30 μm or less, or 20 μm or less. ９０ A particulate filter according to any one of claims 1 to 3, having the following characteristics. [Claim 11] A particulate filter according to any one of claims 1 to 3, further comprising a ternary conversion catalyst (TWC) coating, preferably a wash coat containing a TWC composition. [Claim 12] The particulate filter according to claim 11, wherein the ternary conversion catalyst coating is located in at least a portion of the inlet channel and / or outlet channel of the substrate. [Claim 13] The particulate filter according to any one of claims 1 to 3, wherein the layer of inorganic particles is contained in a loading amount of 0.3 to 50 g / L, 0.6 to 20 g / L, or 0.9 to 6 g / L. [Claim 14] A particulate filter according to any one of claims 1 to 3, which is a gasoline particulate filter. [Claim 15] A method for manufacturing a particulate filter according to claim 1, - To provide a substrate that includes a plurality of porous walls extending longitudinally to form a plurality of parallel channels, wherein a certain portion of the channels are inlet channels that are open at the inlet end and closed at the outlet end, and a certain portion of the channels are outlet channels that are closed at the inlet end and open at the outlet end. - Applying the inorganic particles or their precursors to the surface of the porous walls in the inlet and / or outlet channels, wherein at least a portion of the inorganic particles or their precursors are needle-shaped crystalline particles, -Optionally, drying and / or firing, Methods that include... [Claim 16] The method according to claim 15, wherein the inorganic particles are applied by a dry coating process or a wash coating process, preferably by a dry coating process. [Claim 17] An exhaust treatment system comprising a particulate filter according to any one of claims 1 to 3, or a particulate filter obtained from the method according to any one of claims 15 to 16, and positioned downstream of a gasoline engine. [Claim 18] A method for processing exhaust gas from a gasoline engine, the method comprising obtaining the exhaust gas from a particulate filter according to any one of claims 1 to 3, or the method according to claim 15 or 16, or bringing the exhaust gas into contact with a particulate filter obtained therefrom. [Claim 19] A method for processing exhaust gas from a gasoline engine, comprising bringing the exhaust gas into contact with the exhaust treatment system described in Claim 17.

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