Gasoline particulate filter

Abstract

The present invention relates to a particulate filter, comprising 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; and a layer of inorganic particles loaded on the surface of the porous walls in the inlet flow paths and / or the outlet flow paths, wherein the inorganic particles contain boehmite particles or consist of boehmite particles. The present invention also relates to a method for manufacturing a particulate filter, which includes applying inorganic particles containing boehmite particles or consisting of boehmite particles to the inlet flow paths and / or the outlet flow paths of the substrate.

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), as well as 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 particulates generated by a diesel lean burn engine, the particulates generated by a gasoline engine such as a gasoline direct injection engine are finer and tend 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. 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. WO 2018 / 024547 (A1) describes a catalytic particulate filter that includes a TWC catalyst material that penetrates the walls of the particulate filter. Coating the TWC catalyst material on or within the filter can result in an impact on the back pressure. In order to avoid an excessive increase in the back pressure while providing a complete three-way conversion function, specific coating schemes have been proposed in patent applications. The catalytic particulate filter is required to have a coated porosity that is smaller than the uncoated porosity of the particulate filter.

[0005] International Publication No. WO 2018 / 115900 (A1) describes a particulate filter for use in an exhaust treatment system of a gasoline engine. The filter has an inlet side and an outlet side, and at least the inlet side is loaded with a 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 may help prevent a significant amount of the 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 in 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 exhaust gas flow from a gasoline engine that can provide a very high fresh filtration efficiency, e.g., 90% or more, at a relatively low back pressure. SUMMARY OF THE INVENTION

[0009] An object of the present invention is to provide a particulate filter for treating exhaust gas flow 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 powder particles in the inlet and / or outlet flow paths of the filter.

[0011] Accordingly, in a first aspect, the present invention provides 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 said flow paths are inlet flow paths that are open at said inlet end and closed at said outlet end, and a portion of said flow paths are outlet flow paths that are closed at said inlet end and open at said outlet end; - a layer of inorganic particles loaded on the surface of the porous walls in the inlet and / or outlet flow paths, wherein the inorganic particles comprise boehmite particles or consist of boehmite particles, to provide a particulate filter.

[0012] In a second aspect, the present invention provides 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 said flow paths are inlet flow paths that are open at said inlet end and closed at said outlet end, and a portion of said flow paths are outlet flow paths that are closed at said inlet end and open at said outlet end; Providing a method that includes applying inorganic particles containing boehmite particles or consisting of boehmite particles on the surface of a porous wall within an inlet flow path and / or an outlet flow path.

[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 includes 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 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, has been found to 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

Figure 2

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Figure 3B

Figure 3C

Figure 3D

Mode for Carrying Out 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 being 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 interpreted in a non-limiting open manner. That is, for example, additional components or elements may exist. The expression "consists of" or cognates may be included in "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 "..." has its ordinary meaning, which 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. 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 the 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 the 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) components, as well as optionally one or more other components such as stabilizers, promoters, and binders.

[0023] In this specification, references to loadings in units of g / ft 3 or g / in 3 are intended to mean the weight of a particular component, coating, or layer per unit volume of the substrate or substrate portion on which they are loaded.

[0024] According to a first aspect of the present invention, there is provided a particulate filter comprising: - a substrate including a plurality of porous walls extending longitudinally to form a plurality of parallel flow paths extending from an inlet end to an outlet end, wherein a 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 flow path and / or the outlet flow path; wherein the inorganic particles comprise boehmite particles or consist of boehmite particles.

[0025] As used herein, the substrate refers to a structure suitable for withstanding the conditions encountered in the exhaust stream 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 layer.

[0026] The substrate includes a plurality of porous walls that extend longitudinally to form a plurality of parallel flow paths extending from an inlet end to an outlet end, with 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 different from the inlet flow paths being outlet flow paths 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 paths to flow through the porous walls into the outlet flow paths and reach the outlet end of the substrate.

[0027] Generally, the substrate may exhibit a honeycomb structure in which the opposite ends of the alternating flow paths are plugged with plugs.

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

[0029] Suitable ceramic materials used to construct the substrate may include any suitable refractory material, such as cordierite, mullite, cordierite-alumina, silicon carbide, silicon nitride, zirconia, mullite, spodumene, alumina-silica-magnesia, zirconium silicate, magnesium silicate, sillimanite, petalite, alumina, aluminum titanate, and aluminosilicate. Typically, the porous walls of the substrate are made of cordierite or silicon carbide.

[0030] Suitable metal 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. To form an oxide layer on the surface of the substrate to improve the corrosion resistance of the alloy and promote the adhesion of any coating layer to the metal surface, the surface of the metal substrate may be oxidized at a high temperature of, for example, 1000 °C or higher.

[0031] The closed-end flow path is plugged with a plug of sealant material. Any suitable sealant material may be used without limitation.

[0032] 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 shapes. 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 (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 inches. 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.

[0033] Figures 1 and 2 show a typical wall flow substrate including a plurality of inlet and outlet flow paths.

[0034] Figure 1 shows an external view of a wall flow substrate having an inlet end (01) where the exhaust flow (13) enters the substrate and an outlet end (02) where the treated exhaust exits. The alternating flow paths 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.

[0035] 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 certain 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.

[0036] 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 only in the inlet flow channel, only in the outlet flow channel, or in both the inlet and outlet flow channels. In particular, the layer of inorganic particles may be loaded on the porous wall only in the inlet flow channel, or in both the inlet and outlet flow channels, more preferably only in the inlet flow channel.

[0037] 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, although it will be understood that a small amount of the inorganic particles may penetrate into the pores within the porous wall.

[0038] According to the present invention, the inorganic particles include boehmite particles. For example, the inorganic particles may include boehmite particles and optionally additional inorganic particles. The additional inorganic particles may be non - PGM components, such as alumina, zirconia, ceria, silica, titania, magnesium oxide, zinc oxide, zinc carbonate, calcium oxide, calcium carbonate, silicate zeolite, aluminosilicate zeolite, or combinations or composites thereof.

[0039] The additional inorganic particles may also contain PGM components such as palladium components and / or platinum components. 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 at all. However, when one or more PGM components are contained in the inorganic particles, they may exhibit specific catalytic activity. The PGM components, if present, may be supported on the particles of the non-PGM components as described above, or may exist separately from the particles of the non-PGM components. In some embodiments, the inorganic particles do not contain PGM components.

[0040] For the purposes of the present invention, the boehmite particles account for a major amount of the inorganic particles, i.e., more than 50% by weight, which may be, for example, 75% by volume or more, 85% by volume or more, 90% by volume or more, or 95% by volume or more based on the total volume of the inorganic particles.

[0041] Preferably, the inorganic particles may consist essentially of boehmite particles. That is, the inorganic particles contain an unintentionally added amount of inorganic particles other than the boehmite particles. In the present specification, the term "unintentionally 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.

[0042] Boehmite particles having a BET surface area of 150 m 2 / g or less, preferably 100 m 2 / g or less, or 80 m 2 / g or less, as determined by nitrogen adsorption, are particularly useful in the present invention.

[0043] Additionally or alternatively, the boehmite particles useful in the present invention may have a BET pore volume of 0.6 cm 3 / g or less, 0.4 cm 3 / g or less, or 0.3 cm 3 / g or less, as determined by nitrogen adsorption.

[0044] The boehmite particles useful in the present invention have a D of 50 microns (μm) or less, 30 μm or less, or 20 μm or less.90 can have. Boehmite particles useful in the present invention have a D of 20 μm or less, 15 μm or less, or 10 μm or less 50 can have. Boehmite particles useful in the present invention have a D of 8 μm or less, 5 μm or less, or 2 μm or less 10 can have.

[0045] There is no limitation on the source of the boehmite particles for the purposes of the present invention, and they may be commercially available or synthesized by any known method.

[0046] The particulate filter according to the present invention has an inorganic particle layer 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), 0.015 to 0.1 g / in 3 (i.e., about 0.9 to 6 g / L).

[0047] The inorganic particle layer 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.

[0048] 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, and optionally drying and optionally firing the coated substrate. In particular, in the dry coating process for the purposes of the present invention, drying and firing may not be necessary after blowing in the inorganic particles. By this process, no liquid carrier is used. The inorganic particles typically distribute on the surface of the porous wall of the flow path in the form of a particle bed.

[0049] In some embodiments, the boehmite particles and optionally additional inorganic particles (or suitable precursors thereof) may be blown into the inlet channel from the open end towards the closed end. The particle bed formed in the inlet channel may be disposed on the porous wall of the inlet channel or may be disposed relative to a plug that blocks the channel. 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 stream and allows gaseous pollutants in the exhaust stream to permeate therethrough.

[0050] The layer of inorganic particles in the form of a particle bed may extend along the porous wall of the channel in 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 channel or only along a part of the length of the porous wall of the channel.

[0051] 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) from the open end into the channels of the substrate, 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 channel in which the inorganic particles are loaded. Also, the porous coating may extend along the entire length of the porous wall of the channel or only along a part of the length of the porous wall of the channel.

[0052] The particulate filter according to the present invention may further comprise a TWC coat on at least a part of the inlet channel and / or the outlet channel of the substrate. In particular, the TWC coat is present on both the inlet channel and the outlet channel of the substrate.

[0053] The TWC coat is typically in the form of a washcoat containing a TWC composition, also referred to as an "in-wall" coat.

[0054] The TWC coat is intended to be loaded into the pores of the porous wall of the flow path, but it will be understood that a significant amount of the TWC composition may also be found on the surface of the porous wall within the coated flow path.

[0055] 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, such as a rhodium component, as a catalytically active species, 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.

[0056] 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.

[0057] 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.

[0058] The particulate filter according to the present invention is 0.1 to 5.0 g / in 3 (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 / in3 (i.e., about 49 to 122 g / L) and may include a TWC coat at a loading amount.

[0059] The TWC coat may include a PGM component at 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).

[0060] The TWC coat may be applied onto a 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 a supported PGM component and optionally an auxiliary agent in a solvent (e.g., water), drying the coated substrate, and firing.

[0061] 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 is under the layer of inorganic particles.

[0062] In some exemplary embodiments, the particulate filter according to the present invention comprises - a substrate including 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; - a layer of inorganic particles loaded on at least the surface of the porous walls within the inlet flow channels; - optionally, a washcoat including a TWC coat, preferably a TWC composition; and provides a particulate filter in which the inorganic particles include or consist of boehmite particles.

[0063] In a further exemplary embodiment, the particulate filter according to the present invention comprises - a substrate including 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 portion of the flow channels are inlet flow channels that are open at the inlet end and closed at the outlet end, and a portion of the flow channels are outlet flow channels that are closed at the inlet end and open at the outlet end; - a layer of inorganic particles loaded on at least the surface of the porous walls within the inlet flow channels; - optionally, a washcoat including a TWC composition; wherein the inorganic particles include boehmite particles in an amount of 75 wt% or more, 85 wt% or more, 90 wt% or more, or even 95 wt% or more based on the total weight of the inorganic particles.

[0064] In some other exemplary embodiments, the particulate filter according to the present invention comprises - a substrate including 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 portion of the flow channels are inlet flow channels that are open at the inlet end and closed at the outlet end, and a portion of the flow channels are outlet flow channels that are closed at the inlet end and open at the outlet end; - a layer of inorganic particles loaded on at least the surface of the porous walls within the inlet flow channels; - optionally, a washcoat including a TWC composition; wherein the inorganic particles consist essentially of boehmite particles.

[0065] In some specific embodiments, the particulate filter according to the present invention comprises - a substrate including 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 portion of the flow channels are inlet flow channels that are open at the inlet end and closed at the outlet end, and a portion of the flow channels are outlet flow channels that are closed at the inlet end and open at the outlet end; - a layer of inorganic particles loaded on at least the surface of the porous walls within the inlet flow channels; - Optionally, it includes a washcoat containing a TWC composition, The inorganic particles consist essentially of boehmite particles having a BET surface area of 100 m 2 / g or less or 80 m 2 / g or less as determined by nitrogen adsorption.

[0066] In some other specific embodiments, the particulate filter according to the present invention - 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, - A layer of inorganic particles loaded on at least the surface of the porous walls within the inlet flow channels, - Optionally, it includes a washcoat containing a TWC composition, The inorganic particles consist essentially of boehmite particles having a BET pore volume of 0.4 cm 3 / g or less or 0.3 cm 3 / g or less as determined by nitrogen adsorption.

[0067] In some preferred specific embodiments, the particulate filter according to the present invention - 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, - A layer of inorganic particles loaded on at least the surface of the porous walls within the inlet flow channels, - Optionally, it includes a washcoat containing a TWC composition, The inorganic particles consist essentially of boehmite particles having a BET surface area of 100 m 2 / g or less and a BET pore volume of 0.4 cm 3 / g or less as determined by nitrogen adsorption.

[0068] In some more preferred specific embodiments, the particulate filter according to the present invention is - a substrate including a plurality of porous walls extending longitudinally to form a plurality of parallel flow paths extending from an inlet end to an outlet end, wherein a 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 at least the surface of the porous walls within the inlet flow paths; - optionally, a washcoat including a TWC composition; wherein the inorganic particles consist essentially of boehmite particles having a BET surface area of 80 m 2 / g or less and a BET pore volume of 0.3 cm 3 / g or less as determined by nitrogen adsorption.

[0069] In each of the above exemplary and specific embodiments, the inorganic particles have the following particle size characteristics: - D of 30 μm or less 90 , - D of 15 μm or less 50 , - D of 5 μm or less 10 and preferably consists essentially of boehmite particles having at least one, preferably all, of the above.

[0070] The inorganic particles have the following particle size characteristics: - D of 20 μm or less 90 , - D of 10 μm or less 50 , - D of 5 μm or less 10 and more preferably consists essentially of boehmite particles having at least one, preferably all, of the above.

[0071] In the above exemplary and specific embodiments, the layer of inorganic particles preferably does not contain a PGM component.

[0072] In the above exemplary and specific embodiments, the particulate filter preferably includes a washcoat containing the TWC composition.

[0073] The particulate filter may be housed within a shell having an inlet and an outlet for the exhaust stream, which is operably associated with and may be in fluid communication with other parts of the engine exhaust system.

[0074] According to a second aspect of the present invention, there is provided a method for manufacturing a particulate filter, - providing a substrate including a plurality of porous walls extending longitudinally to form a plurality of parallel flow paths extending from an inlet end to an outlet end, wherein a 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 inorganic particles containing or consisting of boehmite particles on the surface of the porous walls within the inlet flow path and / or the outlet flow path.

[0075] The inorganic particles may be applied on the surface of the porous walls by a dry coating process or a washcoat coating process as described above in the first aspect, preferably a dry coating process.

[0076] In some embodiments, the inorganic particles are applied without firing after blowing in the inorganic particles by a dry coating process that includes blowing the inorganic particles or a precursor thereof into the flow path of the substrate from an open end by a carrier gas stream. In some other embodiments, the inorganic particles are applied without drying and firing after blowing in the inorganic particles by a dry coating process that includes blowing the inorganic particles or a suitable precursor thereof into the flow path of the substrate from an open end by a carrier gas stream. In this way, since the applied boehmite particles do not aluminaize, a particulate filter as described above in the first aspect of the present invention can be obtained. More specifically, the boehmite particles and optionally additional inorganic particles (or suitable precursors thereof) may be blown into the flow path from the open end of the flow path toward the closed end.

[0077] In some embodiments, the method for manufacturing a particulate filter further includes applying a TWC coat to at least a part of the porous wall of the inlet and / or outlet flow path of the substrate before applying the inorganic particles on the surface of the porous wall. The TWC coat may be applied by the wash coating process described above.

[0078] Any general descriptions and selections described above for the inorganic particles and the TWC coat in the first aspect are applicable herein by reference.

[0079] According to a third aspect, an exhaust gas treatment system is provided that includes 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, and is disposed downstream of a gasoline engine.

[0080] According to a fourth aspect, a method for treating an exhaust gas stream from a gasoline engine is provided, the method including contacting the exhaust gas stream with the particulate filter described in the first aspect, 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.

[0081] Embodiment 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.

[0082] Embodiment 1. A particulate filter, comprising: - 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 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. A particulate filter, wherein the inorganic particles contain boehmite particles or consist of boehmite particles.

[0083] Embodiment 2. The particulate filter according to Embodiment 1, wherein the inorganic particles contain boehmite 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 based on the total weight of the inorganic particles.

[0084] Embodiment 3. The particulate filter according to Embodiment 2, wherein the inorganic particles consist essentially of boehmite particles.

[0085] Embodiment 4. The particulate filter according to any one of Embodiments 1 to 4, wherein the layer of inorganic particles does not exhibit ternary conversion catalytic activity.

[0086] Embodiment 5. The particulate filter according to any one of Embodiments 1 to 5, wherein the layer of inorganic particles does not contain a PGM component.

[0087] Embodiment 6. The boehmite particles have a nitrogen adsorption determined to be 150 m 2 / g or less, 100 m 2 / g or less, or 80 m 2The particulate filter according to any one of Embodiments 1 to 5, having a BET surface area of 1 m² / g or less.

[0088] Embodiment 7. The boehmite particles have a BET pore volume of 0.6 cm³ / g or less, 0.4 cm³ / g or less, or 0.3 cm³ / g or less, determined by nitrogen adsorption, of the particulate filter according to any one of Embodiments 1 to 6. 3 / g or less, 0.4 cm³ 3 / g or less, or 0.3 cm³ 3 / g or less, of the particulate filter according to any one of Embodiments 1 to 6.

[0089] Embodiment 8. The inorganic particles have at least one, preferably all, of the following particle size characteristics: -50 μm or less, 30 μm or less, or 20 μm or less of D 90 , -20 μm or less, 15 μm or less, or 10 μm or less of D 50 , -8 μm or less, 5 μm or less, or 2 μm or less of D 10 of the particulate filter according to any one of Embodiments 1 to 7.

[0090] Embodiment 9. The particulate filter according to any one of Embodiments 1 to 6, further comprising a three-way conversion catalyst (TWC) coat, preferably a wash coat containing a TWC composition.

[0091] Embodiment 10. The particulate filter according to Embodiment 9, wherein the three-way conversion catalyst coat is in at least a part of the inlet flow path and / or the outlet flow path of the substrate.

[0092] Embodiment 11. The particulate filter according to any one of Embodiments 1 to 10, 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.

[0093] Embodiment 12. The particulate filter according to any one of Embodiments 1 to 9, which is a gasoline particulate filter.

[0094] Embodiment 13. A method for manufacturing a particulate filter, comprising - A plurality of parallel flow paths extending from an inlet end to an outlet end, wherein a certain amount of said flow paths are inlet flow paths that are open at said inlet end and closed at said outlet end, and a certain amount of flow paths are outlet flow paths that are closed at said inlet end and open at said outlet end, providing a substrate including a plurality of porous walls extending longitudinally to form a plurality of parallel flow paths. - Applying inorganic particles including or consisting of boehmite particles on the surface of the porous wall in the inlet flow path and / or the outlet flow path.

[0095] Embodiment 14. The method according to embodiment 13, wherein the inorganic particles are applied by a dry coating process or a wash coating process, preferably by a dry coating process.

[0096] Embodiment 15. The method according to embodiment 13, wherein the inorganic particles are applied by a dry coating process including blowing inorganic particles or their precursors into the flow paths of the substrate from an open end by a carrier gas flow, without drying and / or firing after blowing.

[0097] Embodiment 16. The method according to embodiment 15, wherein the inorganic particles consist of boehmite particles and optionally additional inorganic particles or their suitable precursors.

[0098] Embodiment 17. The method according to any one of embodiments 13 to 16, wherein the inorganic particles contain boehmite 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.

[0099] Embodiment 18. The method according to embodiment 16, wherein the inorganic particles consist essentially of boehmite particles.

[0100] Embodiment 19. The method according to any one of embodiments 13 to 18, wherein the boehmite particles have a BET surface area of 150 m 2 / g or less, 100 m 2 / g or less, or 80 m 2 / g or less, determined by nitrogen adsorption.

[0101] Embodiment 20. The boehmite particles have a BET pore volume of 0.6 cm 3 / g or less, 0.4 cm 3 / g or less, or 0.3 cm 3 / g or less, and the method according to any one of Embodiments 13 to 19.

[0102] Embodiment 21. The inorganic particles have the following particle size characteristics: - D of 50 μm or less, 30 μm or less, or 20 μm or less 90 , - D of 20 μm or less, 15 μm or less, or 10 μm or less 50 , - D of 8 μm or less, 5 μm or less, or 2 μm or less 10 and has at least one, preferably all, of the above, and the method according to any one of Embodiments 13 to 20.

[0103] Embodiment 22. The layer of inorganic particles is applied at a loading of 0.3 to 50 g / L, 0.6 to 20 g / L, or 0.9 to 6 g / L, and the method according to any one of Embodiments 13 to 21.

[0104] Embodiment 23. An exhaust gas treatment system that can be obtained from the particulate filter according to any one of Embodiments 1 to 12, or the method according to any one of Embodiments 13 to 22, or includes the obtained particulate filter and is disposed downstream of a gasoline engine.

[0105] Embodiment 24. A method for treating an exhaust gas flow from a gasoline engine, the method including bringing the exhaust gas flow into contact with the particulate filter according to any one of Embodiments 1 to 12, the particulate filter that can be obtained from the method according to any one of Embodiments 13 to 22, or the exhaust gas treatment system according to Embodiment 23.

Examples

[0106] Aspects of the present invention are more fully described 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 filters Materials and characterization The materials used as inorganic particles for preparing particulate filters 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 the BET model under 77K nitrogen adsorption. X-ray diffraction (XRD) scans were measured by a Bruker D8 Advance, and the XRD patterns are shown in FIGS. 3A to 3D.

[0108] [Table 1]

[0109] Reference Example 1 (R1) A gasoline particulate filter cordierite substrate S1 was used as a reference filter (blank filter), which has 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 paths of the blank filter.

[0111] A 9.68 wt% rhodium nitrate aqueous solution of 24.21 g was impregnated onto 255 g of high surface area gamma alumina powder in a planetary mixer (P-mixer) to form a wet powder while achieving initial wetting. A 16.31 wt% diethanolamine hexahydroxyplatinate aqueous solution of 14.37 g was impregnated onto 712 g of 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, and 78 g of barium nitrate and 68 g of a 21.3 wt% zirconium nitrate aqueous solution were added thereto. 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 path of the blank filter at a washcoat loading of 50%, and coated into the outlet flow path of the blank filter at the remaining 50% washcoat loading. Then, the coated substrate was dried at a temperature of 150 °C for 1 hour and then calcined at a temperature of 550 °C for 1 hour.

[0112] About 1.23 g / in 3 (75 g / L) washcoat loading and about 10.0 g / ft 3 (0.35 g / L) total PGM loading and a 5 / 5 Pt / Rh ratio gave an in-wall TWC coat.

[0113] The TWC coating prepared from the same process is referred to herein as TWC-1.

[0114] Reference Example 3 (R3) The gasoline particulate filter cordierite substrate S2 was used as a reference filter (blank filter), which had a size of 132.1 mm (D) × 127 mm (L), a volume of 1.74 L (about 106.1 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.

[0115] Reference Example 4 (R4) A particulate filter with a TWC coat was fabricated from the same filter substrate as the blank filter of Reference Example 3 (substrate S2) by applying a TWC wash coat to both the inlet and outlet flow channels of the blank filter.

[0116] 20.08 g of a 9.79 wt% rhodium nitrate aqueous solution was impregnated onto 257 g of a high surface area gamma alumina powder in a planetary mixer (P-mixer) to form a wet powder while achieving incipient wetness. 12.05 g of a 16.31 wt% diethanolamine hexahydroxyplatinate aqueous solution was impregnated onto 698 g of a ceria / zirconia (40% ceria) composite powder in a planetary mixer (P-mixer) to form a wet powder while achieving incipient wetness. An aqueous slurry was formed by mixing the above two wet powders with 894 g of deionized water, and 78 g of barium nitrate and 67 g of a 21.0 wt% zirconium nitrate aqueous solution were added thereto. The pH of the slurry was adjusted to 3.6 with nitric acid. The slurry was milled to a particle size D 90 of 4.5 μm, and 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 wash coat loading of 50%. Then, the coated substrate was dried at a temperature of 150 °C for 1 hour and then calcined at a temperature of 550 °C for 1 hour.

[0117] About 1.47 g / in 3 (90 g / L) of wash coat loading and about 10.0 g / ft 3 (0.35 g / L) of total PGM loading and a Pt / Rh ratio of 5 / 5 to obtain an in-wall TWC coat.

[0118] The TWC coating fabricated from the same process is referred to herein as TWC-2.

[0119] Comparative Example 1 (C1) A particulate filter having a layer of TWC coat and alumina particles was fabricated.

[0120] First, for a blank filter similar to that of Reference Example 1 (substrate S1), a particulate filter having a TWC coat (TWC-1) was fabricated by applying the same process as in Reference Example 2. Next, the powder of alumina A 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 powder of alumina A was 4 g / L (0.066 g / in 3 ).

[0121] Comparative Example 2 (C2) A particulate filter having a TWC coat and a layer of alumina particles was fabricated.

[0122] First, for a cordierite substrate S3 as a blank filter, a particulate filter having a TWC coat (TWC-1) was fabricated by applying the same process as in Reference Example 2. This filter has 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. Next, the powder of alumina A 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 powder of alumina A was 2 g / L (0.033 g / in 3 ).

[0123] Comparative Example 3 (C3) A particulate filter having a TWC coat and a layer of alumina particles was fabricated.

[0124] First, for a blank filter similar to that of Reference Example 3 (substrate S2), a particulate filter having a TWC coat (TWC-2) was fabricated by applying the same process as in Reference Example 4. Next, the powder of alumina A was mixed with a carrier gas and blown into the inlet flow path of the filter at a flow rate of 600 m3 It 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 alumina A powder was 3 g / L (0.05 g / in 3 ).

[0125] Comparative Example 4 (C4) A particulate filter having a TWC coat and a layer of alumina particles was produced.

[0126] The production of the particulate filter was the same as that of Comparative Example 3, except that the loading amount of the alumina A powder was 4 g / L (0.066 g / in 3 ).

[0127] Comparative Example 5 (C5) A particulate filter having a TWC coat and a layer of alumina particles was produced.

[0128] The production of the particulate filter was the same as that of Comparative Example 3, except that the loading amount of the alumina A powder was 7 g / L (0.115 g / in 3 ).

[0129] Example 1 (E1) of the present invention A particulate filter having a TWC coat and a layer of boehmite B particles was produced.

[0130] First, a particulate filter (TWC-1) having a TWC coat was produced by applying the same process as in Reference Example 2 to a blank filter similar to Reference Example 1 (substrate S1). Next, the powder of boehmite B 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. The loading amount of the boehmite B powder was 3.6 g / L (0.06 g / in 3 ).

[0131] Example 2 (E2) of the present invention A particulate filter having a TWC coat and a layer of boehmite C particles was produced.

[0132] First, for a blank filter similar to Comparative Example 2 (substrate S3), a particulate filter (TWC-1) having a TWC coat was produced by applying the same process as in Reference Example 2. Next, the powder of boehmite C 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. The loading amount of the boehmite C powder was 1.12 g / L (0.018 g / in 3 ).

[0133] Example 3 (E3) of the present invention A particulate filter having a TWC coat and a layer of boehmite D particles was produced.

[0134] First, for a blank filter similar to Reference Example 3 (substrate S2), a particulate filter (TWC-2) having a TWC coat was produced by applying the same process as in Reference Example 4. Next, the powder of boehmite D 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. The loading amount of the boehmite D powder was 2.4 g / L (0.04 g / in 3 ).

[0135] Example 4 (E4) of the present invention A particulate filter having a TWC coat and a layer of boehmite D particles was produced.

[0136] The production of the particulate filter was the same as that of Example 3 of the present invention, except that the loading amount of the boehmite D powder was 3.6 g / L (0.06 g / in 3 ).

[0137] II. Filtration performance II.1 Back pressure The back pressure (BP) of the particulate filters of all examples was investigated by measuring them with a SuperFlow SF-1020 flow bench under a cold air flow of 600 m 3 / h.

[0138] II.2 Fresh filtration efficiency In accordance with the standard procedure 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, di(2-ethylhexyl) sebacate aerosol was used as particles to measure the filtration efficiency of the particulate filter from the above examples in the fresh state (0 km, or unused state). 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

[0139]

Equation

[0140] The test results of each particulate filter from the above examples are summarized in Table 2 below.

[0141]

Table 2

[0142] From the comparison of Reference Example 1 (R1) with Reference Example 2 (R2), and Reference Example 3 (R3) with Reference Example 4 (R4), it can be seen that the particulate filter having 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. Furthermore, the fresh filtration efficiency (FFE) can be improved by applying a layer of alumina A particles as shown in Comparative Example 1 (C1), with an acceptable increase in back pressure. Surprisingly, the fresh filtration efficiency (FFE) can be more significantly improved by applying a layer of boehmite B particles as shown in Example 1 (E1) of the present invention, with an acceptable increase in back pressure. The fresh filtration efficiency of the particulate filter of Example 1 (E1) of the present invention can reach 96%, which is much higher than that of Comparative Example 1 (C1) which is 88%, while the back pressures of the two particulate filters are very comparable at 63 - 64 mbar.

[0143] Also, the particulate filter of Example 2 (E2) of the present invention shows a significantly higher fresh filtration efficiency (FFE) than Comparative Example 2 (C2) at the same back pressure.

[0144] The surprising improvement provided by using boehmite as the inorganic particle can also be observed from the comparison between Examples 3 and 4 of the present invention and Comparative Examples 3 - 5. Notably, the particulate filter of Example 3 (E3) of the present invention shows a back pressure comparable to that of Comparative Example 3 (C3), but a significantly higher fresh filtration efficiency than Comparative Example 3 (C3). Furthermore, the particulate filter of Example 3 (E3) of the present invention shows a similar fresh filtration efficiency at a significantly lower back pressure than Comparative Example 5 (C5). The particulate filter of Example 4 (E4) of the present invention can show a fresh filtration efficiency of 98% higher than that of Comparative Example 5 (C5), while the particulate filter of Example 4 (E4) of the present invention shows an even lower back pressure than Comparative Example 5 (C5).

[0145] The particulate filter comprising a layer of boehmite particles has been demonstrated to be superior to a comparative filter made from alumina particles with respect to the balance between backpressure and fresh filtration efficiency. Since firing is generally known to result in a lower backpressure compared to the corresponding articles made without firing, it can be expected that the particulate filter comprising a layer of boehmite particles will function better after firing.

[0146] Although the invention herein has been described with reference to specific embodiments, it should be understood that these embodiments are merely illustrative of the principles and applications of the 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 invention without departing from the spirit and scope of the invention. Accordingly, the invention is intended to embrace modifications and variations that fall within the scope of the appended claims and their equivalents.

Claims

1. A particulate filter, comprising: - A plurality of parallel flow paths extending from an inlet end to an outlet end, wherein a certain amount of said flow paths are inlet flow paths that are open at said inlet end and closed at said outlet end, and a certain amount of said flow paths are outlet flow paths that are closed at said inlet end and open at said outlet end, a substrate including a plurality of porous walls extending longitudinally to form said plurality of parallel flow paths; - A layer of inorganic particles loaded on the surface of the porous walls within said inlet flow path and / or outlet flow path, preferably at least within said inlet flow path; Said particulate filter, wherein said inorganic particles comprise boehmite particles or consist of boehmite particles.

2. The particulate filter according to claim 1, wherein said inorganic particles contain said boehmite 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 based on the total weight of said inorganic particles.

3. The particulate filter according to claim 2, wherein said inorganic particles consist essentially of said boehmite particles.

4. The particulate filter according to any one of claims 1 to 3, wherein the layer of said inorganic particles does not exhibit three-way conversion catalytic activity.

5. The particulate filter according to any one of claims 1 to 4, wherein the layer of said inorganic particles does not contain a PGM component.

6. The boehmite particles have a BET surface area of 150 m ２ / g or less, 100 m ２ / g or less, or 80 m ２ / g or less, and the particulate filter according to any one of claims 1 to 5.

7. The boehmite particles have a BET pore volume of 0.6 cm ３ / g or less, 0.4 cm ３ / g or less, or 0.3 cm ３ / g or less, and the particulate filter according to any one of claims 1 to 6.

8. Said inorganic particles have the following particle size characteristics: -50 µm or less, 30 µm or less, or 20 µm or less of D ９０ , D of -20 μm or less, 15 μm or less, or 10 μm or less ５０ , D of 8 μm or less, 5 μm or less, or 2 μm or less １０ The particulate filter according to any one of claims 1 to 7, having at least one, preferably all, of the above.

9. The particulate filter according to any one of claims 1 to 8, further comprising a three-way conversion catalyst (TWC) coat, preferably a wash coat containing a TWC composition.

10. The particulate filter according to claim 9, wherein said three-way conversion catalyst coat is at least partially in said inlet flow path and / or outlet flow path of said substrate.

11. The particulate filter according to any one of claims 1 to 10, wherein said layer of inorganic particles is included in a loading amount of 0.3 to 50 g / L, 0.6 to 20 g / L, or 0.9 to 6 g / L.

12. The particulate filter according to any one of claims 1 to 9, which is a gasoline particulate filter.

13. A method for manufacturing a particulate filter, comprising: - 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, providing a substrate including a plurality of porous walls extending longitudinally to form the plurality of parallel flow paths. - Applying inorganic particles including or consisting of boehmite particles on the surface of the porous walls in the inlet flow path and / or the outlet flow path.

14. The method according to claim 13, wherein the inorganic particles are applied by a dry coating process or a wash coating process, preferably by a dry coating process.

15. The method according to claim 13, wherein the inorganic particles are applied by a dry coating process including blowing the inorganic particles or their precursors into the flow paths of the substrate from the open end by a carrier gas flow, without drying and / or firing after blowing.

16. The method according to claim 15, wherein the inorganic particles consist of the boehmite particles and optionally additional inorganic particles or their suitable precursors.

17. The method according to any one of claims 13 to 16, wherein the inorganic particles contain the boehmite 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.

18. The method according to claim 16, wherein the inorganic particles consist essentially of the boehmite particles.

19. The boehmite particles have a BET surface area of 150 m ２ / g or less, 100 m ２ / g or less, or 80 m ２ / g or less, according to any one of claims 13 to 18.

20. The boehmite particles have a BET pore volume of 0.6 cm ３ / g or less, 0.4 cm ３ / g or less, or 0.3 cm ３ / g or less, according to the method according to any one of claims 13 to 19.

21. The inorganic particles have the following particle size characteristics: -50 µm or less, 30 µm or less, or 20 µm or less of D ９０ , D of -20 μm or less, 15 μm or less, or 10 μm or less ５０ , -8 μm or less, 5 μm or less, or D of 2 μm or less １０ The method according to any one of claims 13 to 20, having at least one, preferably all, of the above.

22. The method according to any one of claims 13 to 21, wherein the layer of the inorganic particles is applied at a loading amount of 0.3 to 50 g / L, 0.6 to 20 g / L, or 0.9 to 6 g / L.

23. An exhaust gas treatment system including the particulate filter according to any one of claims 1 to 12, or obtainable from the method according to any one of claims 13 to 22, or including the obtained particulate filter, and disposed downstream of a gasoline engine.

24. A method for treating an exhaust gas flow from a gasoline engine, the method comprising contacting the exhaust gas flow with a particulate filter according to any one of claims 1 to 12, obtainable from a method according to any one of claims 13 to 22, or an obtained particulate filter, or an exhaust gas treatment system according to claim 23.

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