Gasoline particulate filter

Abstract

The present invention relates to a particulate filter, the particulate filter being a substrate comprising 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 substrate, 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, the layer of inorganic particles containing inorganic particles having a small BET pore volume of 0.5 cm 3 / g or less. The present invention also relates to a method for manufacturing a particulate filter, which includes applying inorganic particles or a precursor thereof to the surface of the porous walls in the inlet flow path and / or the outlet flow path to deposit a layer of inorganic particles containing inorganic particles having a small BET pore volume.

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 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 catalyzed 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 the back pressure, specific coating schemes have been proposed in patent applications. The catalyzed particulate filter is required to have a coated porosity that is 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 gasoline particulate filters.

[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 higher fresh filtration efficiency 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 particles having a small pore volume in the inlet flow path and / or the outlet flow path of the filter.

[0011] Accordingly, in a first aspect, the present invention provides a particulate filter, - a substrate comprising 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, wherein the layer of inorganic particles comprises inorganic particles having a small BET pore volume of 0.5 cm 3 / g or less, to provide a particulate filter.

[0012] In a second aspect, the present invention provides a method for manufacturing a particulate filter, - providing a substrate comprising 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, - 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, - Optionally, drying and / or firing, and 0.5 cm 3 A method of depositing a layer of inorganic particles comprising inorganic particles having a small BET pore volume of 0.5 cm3 / g or less.

[0013] In a third aspect, the present invention provides an exhaust gas treatment system disposed downstream of a gasoline engine, which can be obtained from the particulate filter according to the first aspect or 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 comprising contacting the exhaust gas flow with the particulate filter according to the first aspect, or the 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, has been found to provide improved fresh filtration efficiency compared to prior art counterparts, while no significant increase in backpressure was observed.

Brief Description of the Drawings

[0016]

Figure 1

Figure 2

Modes 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 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-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 or pre-coated wall of a substrate. 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 90 " have their ordinary meanings, referring 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] Terms for platinum group metal (PGM) components such as "palladium component", "platinum component", and "rhodium component" are intended to account for 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, for example, a metal compound, complex, etc. that decomposes or is otherwise converted to a catalytically active form during the calcination or use of the catalyst.

[0022] The term "substrate" 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] As used herein, references to loading amounts in units of "g / ft 3 " or "g / in 3 " are intended to mean the weight of a particular component, coat, or layer per unit volume of the substrate or substrate portion onto which they are loaded.

[0024] According to a first aspect of the present invention, there is provided a particulate filter comprising: - 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; - a layer of inorganic particles loaded on the surface of the porous walls within the inlet flow channels and / or the outlet flow channels; wherein the layer of inorganic particles comprises inorganic particles having a small BET pore volume of 0.5 cm 3 / g or less.

[0025] 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, such as the layer of inorganic particles described herein, and any other layer.

[0026] The substrate comprises 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 within the inlet flow channels to flow through the porous walls into the outlet flow channels of the substrate and reach the outlet end.

[0027] Generally, the substrate may exhibit a honeycomb structure in which the alternating flow channels are blocked by plugs at both ends.

[0028] The porous wall of the substrate is 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 wall of the substrate is 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. 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 alloy to improve the corrosion resistance of the alloy and promote the adhesion of any coating layer to the metal surface.

[0031] The closed-end flow channels are blocked by plugs of a sealant material. Any suitable sealant material may be used without limitation.

[0032] The flow channels of the substrate can have 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 channels (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, with a typical range being 2 mils to 0.1 inches. Preferably, the substrate has an equal number of inlet flow channels as the number of outlet flow channels, and the flow channels 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 channels.

[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 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).

[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 constant wall thickness between the flow channels. The exhaust 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 include 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 the inlet flow channel only, the outlet flow channel only, 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 the inlet flow channel only, or both the inlet flow channel and the outlet flow channel, more preferably in the inlet flow channel only.

[0037] The layer of inorganic particles is intended to be loaded on the surface of the porous wall in the inlet and / or outlet flow path, which is also called an "on-wall" coat, and it will be understood that a small number of inorganic particles may penetrate into the pores within the porous wall.

[0038] According to the present invention, inorganic particles, particularly inorganic particles having a small BET pore volume of 0.5 cm 3 / g or less (also referred to herein as "inorganic particles having a small pore volume") 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.

[0039] Thus, the inorganic particles having a small pore volume herein may be 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 a combination or composite thereof.

[0040] Preferably, the inorganic particles, particularly the inorganic particles having a small pore volume, 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, silica, or a combination or composite thereof.

[0041] 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 having a small pore volume as described above, or may be present separately from the particles of the non-PGM inorganic material having a small pore volume.

[0042] In this specification, a layer of inorganic particles loaded on a porous wall in the inlet and / or outlet flow path of a substrate refers to a layer that exhibits little or no TWC activity, preferably no TWC activity. However, when one or more PGM components are included in the inorganic particles, it may exhibit a specific catalytic activity.

[0043] In some embodiments, the layer of inorganic particles does not contain a PGM component. Preferably, the layer of inorganic particles may consist mainly or substantially of inorganic particles having a small pore volume.

[0044] In this specification, 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 inorganic particles having the specified small pore volume, which may be, for example, 75% by volume or more, 85% by volume or more, 90% by volume or more, or even 95% by volume or more.

[0045] In this specification, 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 inorganic particles having the specified small pore volume. In this specification, 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.

[0046] The inventors have found that inorganic particles having a small pore volume determined by nitrogen adsorption, i.e., a BET pore volume of 0.5 cm 3 / g or less, can have a beneficial effect on the fresh filtration efficiency of particulate filters. For example, inorganic particles having a small BET pore volume of 0.3 cm 3 / g or less or 0.2 cm 3 / g or less determined by nitrogen adsorption may be particularly mentioned.

[0047] Inorganic particles, particularly inorganic particles having a small pore volume, have a specific surface area of at least 60 m2 It may have a BET surface area of / g, which is particularly useful in the present invention. For example, inorganic particles, especially inorganic particles with a small pore volume, may have a BET surface area of at least 80 m 2 / g or at least 90 m 2 / g.

[0048] In some embodiments, the layer of inorganic particles comprises inorganic particles having a small BET pore volume of 0.5 cm 3 / g or less and a BET surface area of at least 60 m 2 / g.

[0049] In some other embodiments, the layer of inorganic particles comprises inorganic particles having a small BET pore volume of 0.3 cm 3 / g or less and a BET surface area of at least 80 m 2 / g.

[0050] In some further embodiments, the layer of inorganic particles comprises inorganic particles having a small BET pore volume of 0.2 cm 3 / g or less and a BET surface area of at least 90 m 2 / g.

[0051] Inorganic particles useful in the present invention, especially inorganic particles with a small pore volume, may have a D of 50 microns (μm) or less, 30 μm or less, or 20 μm or less. 90 Inorganic particles useful in the present invention, especially inorganic particles with a small pore volume, may have a D of 20 μm or less, 15 μm or less, or 10 μm or less. 50 Inorganic particles useful in the present invention, especially inorganic particles with a small pore volume, may have a D of 8 μm or less or 3 μm or less. 10

[0052] The particulate filter according to the present invention has a weight of 0.005 - 0.83 g / in 3 (i.e., about 0.3 - 50 g / L), 0.01 - 0.33 g / in 3 (i.e., about 0.6 - 20 g / L), or 0.015 - 0.1 g / in 3It may include a layer of inorganic particles with a loading amount of (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. Generally, it is carried out by blowing inorganic particles or their suitable precursors in particle form into the flow path of the substrate from the open end by a carrier gas flow, 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] In some embodiments, the inorganic particles or their suitable precursors may be blown into the inlet flow path from the open end towards the closed end of the flow path. 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 with respect to a plug that blocks the flow path. The fine particle 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 the gaseous pollutants in the exhaust flow to permeate through it.

[0056] The layer of inorganic particles in the form of a particle bed may extend along the porous wall of the flow path where 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.

[0057] 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 an open end into the flow channels of a substrate, drying the coated substrate, and optionally firing it. The layer of inorganic particles applied by washcoating may be in the form of a porous coating and may extend along the porous walls of the flow channels into which the inorganic particles are loaded. Also, the porous coating may extend along the entire length of the porous walls of the flow channels or only along a part of the length of the porous walls of the flow channels.

[0058] The particulate filter according to the present invention may further include a TWC coat on at least a part of the inlet flow channel and / or the outlet flow channel of the substrate. In particular, the TWC coat is present in both the inlet flow channel and the outlet flow channel of the substrate.

[0059] The TWC coat is typically in the form of a washcoat containing a TWC composition, also called an "in-wall" coat.

[0060] Although the TWC coat is intended to be loaded into the pores of the porous walls of the flow channels, 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.

[0061] There is no particular limitation on the TWC composition useful for the TWC coat included in the particulate filter. Typically, the TWC composition includes 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.

[0062] 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.

[0063] Examples of oxygen storage components (OSCs) 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.

[0064] The particulate filter according to the present invention may include a TWC coating at a loading of 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 / in 3 (i.e., about 49 to 122 g / L).

[0065] The TWC coating may include a PGM component at a total loading 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.

[0066] The TWC coat may be applied on 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 the supported PGM component and optionally an auxiliary agent in a solvent (e.g., water), drying the coated substrate, and firing it.

[0067] The TWC coat, if present, is applied on 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.

[0068] 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, The layer of inorganic particles includes inorganic particles having a small BET pore volume of 0.5 cm 3 / g or less.

[0069] In a further exemplary embodiment, 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 washcoat containing a TWC composition, The layer of inorganic particles is 0.5 cm 3 contains inorganic particles having a small BET pore volume of 0.5 cm 3 / g or less 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.

[0070] In some other exemplary embodiments, the particulate filter according to the present invention is - 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 wall within the inlet flow channels; - optionally, a washcoat including a TWC composition. The layer of inorganic particles is 3 mainly or substantially composed of inorganic particles of a non-PGM inorganic material having a small BET pore volume of 0.5 cm 3 / g or less.

[0071] In some further exemplary embodiments, the particulate filter according to the present invention is - 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 wall within the inlet flow channels; - optionally, a washcoat including a TWC composition. The layer of inorganic particles is 3 composed mainly or substantially of inorganic particles having a small BET pore volume of 0.5 cm 3 / g or less and a BET surface area of at least 60 m 2 / g. 2 / g.

[0072] In some 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 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 at least the surface of the porous walls within the inlet flow path. - Optionally, including a washcoat containing a TWC composition. The layer of inorganic particles has a small BET pore volume of 0.5 cm 3 / g or less and a BET surface area of at least 60 m 2 / g, and consists mainly or substantially of inorganic particles of a non-PGM inorganic material, where the non-PGM inorganic material is selected from alumina, hydrated alumina, boehmite, silica, zinc oxide, zirconia, or combinations or composites thereof.

[0073] In some preferred specific embodiments, the particulate filter according to the present invention - 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 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 at least the surface of the porous walls within the inlet flow path. - Optionally, including a washcoat containing a TWC composition. The layer of inorganic particles has a small BET pore volume of 0.3 cm 3 / g or less and a BET surface area of at least 80 m 2 / g, and consists mainly or substantially of inorganic particles of a non-PGM inorganic material, where the non-PGM inorganic material is selected from alumina, hydrated alumina, boehmite, silica, zinc oxide, zirconia, or combinations or composites thereof.

[0074] In some other 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 is an inlet flow path that is open at the inlet end and closed at the outlet end, and a certain amount of the flow paths is an outlet flow path that is closed at the inlet end and open at the outlet end, 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 has a small BET pore volume of 0.2 cm 3 / g or less and a BET surface area of at least 90 m 2 / g, and is mainly or substantially composed of inorganic particles of a non-PGM inorganic material, and the non-PGM inorganic material is selected from alumina, hydrated alumina, boehmite, silica, zinc oxide, zirconia, or a combination or composite thereof.

[0075] In each of the above exemplary and specific embodiments, the inorganic particles preferably consist essentially of inorganic particles having at least one, preferably all, of the following particle size characteristics. - D of 30 μm or less 90 , - D of 15 μm or less 50 , and - D of 8 μm or less 10 .

[0076] More preferably, the inorganic particles consist essentially of inorganic particles having at least one, preferably all, of the following particle size characteristics. - D of 20 μm or less 90 , - D of 10 μm or less 50 , and - D of 3 μm or less 10 .

[0077] In the above exemplary and specific embodiments, the layer of inorganic particles preferably does not contain a PGM component.

[0078] In an exemplary and specific embodiment as described above, the particulate filter preferably comprises a washcoat comprising a TWC composition.

[0079] 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.

[0080] According to a second aspect of the present invention, a method for manufacturing a particulate filter, - 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 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; - applying inorganic particles or a precursor thereof onto the surface of the porous walls within the inlet flow channels and / or the outlet flow channels; - optionally, drying and / or firing; 0.5 cm 3 A method is provided for depositing a layer of inorganic particles comprising inorganic particles having a small BET pore volume of / g or less.

[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 washcoat 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 washcoat 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 inorganic particles having a small BET pore volume of 0.5 cm 3 / g or less as specified herein. In particular, the inorganic particles applied consist essentially of inorganic particles having a small BET pore volume of 0.5 cm 3 / g or less.

[0085] According to a third aspect, there is provided an exhaust gas treatment system including a particulate filter according to the first aspect or a particulate filter obtainable or obtained from the method according to the second aspect, 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 a particulate filter according to the first aspect, or a particulate filter obtainable or obtained from the method according to the second aspect, or the exhaust gas treatment system according to the third aspect.

[0087] Embodiments Various embodiments are listed below. It will be understood that the embodiments listed below may 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 porous walls extending longitudinally 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 path and / or the outlet flow path, preferably at least in the inlet flow path, wherein the layer of inorganic particles has a BET pore volume of 0.5 cm 3A particulate filter comprising inorganic particles having a small BET pore volume of / g or less.

[0089] Embodiment 2. The particulate filter according to Embodiment 1, wherein the layer of inorganic particles contains inorganic particles having a small BET pore volume 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 inorganic particles having a small BET pore volume.

[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 inorganic particles, particularly the inorganic particles having a small BET pore volume, are particles of a non-PGM inorganic material selected particularly 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. The particulate filter according to any one of Embodiments 1 to 5.

[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 small BET pore volume is 0.3 cm 3 / g or less, or 0.2 cm 3 / g or less.

[0096] Embodiment 9. The inorganic particles having a small BET pore volume have a BET surface area of at least 60 m 2 / g, at least 80 m 2 / g, or at least 90 m 2 / g, and the particulate filter according to any one of Embodiments 1 to 8.

[0097] Embodiment 10. The inorganic particles, particularly the inorganic particles having a small BET pore volume, have a D 90 of 50 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) coat, preferably a wash coat containing a TWC composition.

[0099] Embodiment 12. The particulate filter according to Embodiment 11, 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.

[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 15. 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 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; - Applying inorganic particles or precursors thereof on the surface of the porous wall within the inlet flow path and / or the outlet flow path, - Optionally, drying and / or firing, A method of depositing a layer of inorganic particles containing inorganic particles having a small BET pore volume.

[0103] Embodiment 16. The method according to embodiment 15, wherein the inorganic particles are applied by a dry coating process or a wash coating process, preferably by a dry coating process.

[0104] Embodiment 17. An exhaust gas treatment system including a particulate filter according to any one of embodiments 1 to 14, or obtainable from or including a particulate filter obtained from the method according to any one of embodiments 15 to 16, and disposed downstream of a gasoline engine.

[0105] Embodiment 18. A method of treating an exhaust gas flow from a gasoline engine, the method including contacting the exhaust gas flow with a particulate filter according to any one of embodiments 1 to 14, or obtainable from or including a particulate filter obtained from the method according to any one of embodiments 15 to 16, or the exhaust gas 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 preparing 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 the BET model under nitrogen adsorption at 77K.

[0108]

Table 1

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

[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] 20.08 g of a 9.79 wt% rhodium nitrate aqueous solution was impregnated onto 257 g of high surface area gamma alumina powder in a planetary mixer (P - mixer) to form a wet powder while achieving initial wetting. 12.05 g of a 16.31 wt% diethanolamine hexahydroxyplatinate aqueous solution was impregnated onto 698 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 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 to 4.5 μm, and then coated into the inlet flow path of a 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 1.47 g / in 3 (90 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 were used to obtain 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 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.

[0115] Reference Example 4 (R4) A particulate filter having a TWC coat was prepared from the same filter substrate as the blank filter of Reference Example 2 (substrate S2) by applying a TWC wash coat to both the inlet and outlet flow channels of the blank filter.

[0116] 24.21 g of a 9.68 wt% rhodium nitrate aqueous solution was impregnated into 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, 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 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 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.

[0117] About 1.23 g / in 3 (75 g / L) wash coat loading and about 10.0 g / ft 3 (0.35 g / L) total PGM loading and a 5 / 5 Pt / Rh ratio were used to obtain an in-wall TWC coat.

[0118] The TWC coating prepared 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 prepared.

[0120] First, for a blank filter similar to Reference Example 1 (substrate S1), a particulate filter having a TWC coat (TWC-1) was prepared 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 1 g / L (0.016 g / in 3 ).

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

[0122] The particulate filter was prepared in the same manner as in Comparative Example 1, except that the loading amount of the powder of alumina A was 3 g / L (0.05 g / in 3 ).

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

[0124] The particulate filter was prepared in the same manner as in Comparative Example 1, except that the loading amount of the powder of alumina A was 5 g / L (0.082 g / in 3 ).

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

[0126] The particulate filter was prepared in the same manner as in Comparative Example 1, except that the loading amount of the powder of alumina A was 7 g / L (0.115 g / in 3 ).

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

[0128] First, for a blank filter similar to that of Reference Example 3 (substrate S2), a particulate filter having a TWC coat (TWC-2) was prepared 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 m 3 / h at room temperature. After coating, the filter having a layer of inorganic particles in the inlet flow path was calcined at a temperature of 550°C for 1 hour. The loading amount of the powder of alumina A was 4 g / L (0.05 g / in 3 ).

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

[0130] First, for a blank filter similar to that of Reference Example 1 (substrate S1), a particulate filter having a TWC coat (TWC-1) was prepared by applying the same process as in Reference Example 2. Next, the powder of alumina B 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 calcined at a temperature of 550°C for 1 hour. The loading amount of the powder of alumina B was 1 g / L (0.016 g / in 3 ).

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

[0132] The preparation of the particulate filter was the same as that of Example 1 of the present invention, except that the loading amount of the inorganic particles was 2 g / L (0.033 g / in 3 ).

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

[0134] The preparation of the particulate filter was the same as that of Example 1 of the present invention, except that the loading amount of the inorganic particles was 3 g / L (0.05 g / in 3 )

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

[0136] The preparation of the particulate filter was the same as that of Example 1 of the present invention, except that the loading amount of the inorganic particles was 4 g / L (0.05 g / in 3 )

[0137] Example 5 (E5) of the present invention A particulate filter having a TWC coat and a layer of alumina particles was prepared.

[0138] First, a particulate filter having a TWC coat (TWC-1) was prepared 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 alumina 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. After coating, the filter having a layer of inorganic particles in the inlet flow path was calcined at a temperature of 550°C for 1 hour. The loading amount of the powder of alumina C was 1 g / L (0.016 g / in 3 )

[0139] Example 6 (E6) of the present invention A particulate filter having a TWC coat and a layer of alumina particles was prepared.

[0140] The preparation of the particulate filter was the same as that of Example 5 of the present invention, except that the loading amount of the powder of alumina C was 2 g / L (0.033 g / in 3 )

[0141] Example 7 (E7) of the present invention A particulate filter having a TWC coat and a layer of alumina particles was prepared.

[0142] The preparation of the particulate filter was the same as in Example 5 of the present invention, except that the loading amount of alumina C powder was 3 g / L (0.05 g / in 3 )

[0143] Example 8 (E8) of the present invention A particulate filter having a TWC coat and a layer of alumina particles was prepared.

[0144] The preparation of the particulate filter was the same as in Example 5 of the present invention, except that the loading amount of alumina C powder was 5 g / L (0.082 g / in 3 )

[0145] Example 9 (E9) of the present invention A particulate filter having a TWC coat and a layer of alumina particles was prepared.

[0146] First, a particulate filter having a TWC coat (TWC-2) was prepared by applying the same process as in Reference Example 4 to a blank filter similar to Reference Example 3 (substrate S2). Next, the powder of alumina B 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 alumina B powder was 3 g / L (0.05 g / in 3 )

[0147] Example 10 (E10) of the present invention A particulate filter having a TWC coat and a layer of inorganic particles was prepared.

[0148] The preparation of the particulate filter was the same as in Example 9 of the present invention, except that the powder of alumina C was used instead of the powder of alumina B.

[0149] II. Filtration performance II.1 Back pressure The particulate filters of all examples were at 600 m3 The back pressure (BP) was investigated by measurement using a SuperFlow SF-1020 flow bench under a cold air flow of / h.

[0150] II.2 Fresh filtration efficiency 1) According to 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 filters from Reference Examples 1 and 2, Comparative Examples 1 to 4, and Examples 1 to 8 of the present invention 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

[0151]

Equation

[0152]

Equation

[0153] The test results of each particulate filter from the above examples are summarized in Table 2 below.

[0154]

Table 2

[0155] From the comparison between Reference Example 1 (R1) and Reference Example 2 (R2) and between Reference Example 3 (R3) and Reference Example 4 (R4), it can be seen that the particulate filter having the TWC coat has a lower fresh filtration efficiency (FFE) with a higher back pressure (BP) than the blank filter, which may be because the TWC component penetrates into the porous wall of the substrate of the particulate filter.

[0156] The fresh filtration efficiency (FFE) can be improved by applying a layer of alumina particles as shown in Comparative Examples 1 to 4 (C1 to C4) as the back pressure increases. Surprisingly, the fresh filtration efficiency can be improved to a greater extent by applying a layer of alumina particles having a small pore volume as shown in Examples 1 to 8 (E1 to E8) of the present invention. In particular, the particulate filters of the examples of the present invention using alumina particles having a small pore volume have a significantly higher fresh filtration efficiency than the particulate filters of Comparative Examples 1 to 4 using alumina particles having a large pore volume.

[0157] The surprising improvement provided by the layer of inorganic particles having a small pore volume can also be observed from the comparison between Examples 9 and 10 (E9 and E10) of the present invention and Comparative Example 5 (C5). Notably, the particulate filters of Examples 9 and 10 of the present invention show a significantly higher fresh filtration efficiency than Comparative Example 5, and the back pressure is the same or slightly lower.

[0158] Although the present invention in this specification 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 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

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, The layer of inorganic particles is 0.5 cm ３ A particulate filter containing inorganic particles with a small BET pore volume of less than / g.

2. The particulate filter according to claim 1, wherein the layer of inorganic particles comprises inorganic particles having a small BET pore volume of 50 volume% or more, 75 volume% or more, 85 volume% or more, 90 volume% or more, and even 95 volume% or more.

3. The particulate filter according to claim 2, wherein the layer of inorganic particles consists substantially of inorganic particles having a small BET pore volume.

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.

5. The particulate filter according to any one of claims 1 to 3, wherein the layer of inorganic particles does not contain PGM components.

6. The particulate filter according to any one of claims 1 to 3, wherein the inorganic particles, in particular the inorganic particles having a small BET pore volume, 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.

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.

8. The aforementioned small BET pore volume is 0.3 cm ３ Less than or equal to 0.2 cm / g ３ A particulate filter according to any one of claims 1 to 3, wherein the amount is less than or equal to / g.

9. The inorganic particles having a small BET pore volume are at least 60 m ２ / g, at least 80m ２ / g, or at least 90m ２ A particulate filter according to any one of claims 1 to 3, having a BET surface area of ​​1 / g.

10. The inorganic particles, particularly those having a small BET pore volume, have a D 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.

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.

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.

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.

14. A particulate filter according to any one of claims 1 to 3, which is a gasoline particulate filter.

15. A method for manufacturing a particulate filter according to any one of claims 1 to 3, - 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, -Optionally, including drying and / or firing, A method for depositing a layer of inorganic particles containing inorganic particles having a small BET pore volume.

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.

17. An exhaust treatment system comprising a particulate filter according to any one of claims 1 to 14, or a particulate filter that can be obtained from or obtained by the method of claim 15 or 16, and which is located downstream of a gasoline engine.

18. A method for processing exhaust gas from a gasoline engine, comprising bringing the exhaust gas into contact with a particulate filter according to any one of claims 1 to 14, or the method according to claim 15 or 16, or with an exhaust treatment system according to claim 17.

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