Gasoline Particulate Filter

Abstract

The present invention is 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, a quantity of the flow paths being inlet flow paths that are open at the inlet end and closed at the outlet end, and a quantity of the flow paths being 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 surfaces of the porous walls in the inlet and / or outlet flow paths, preferably at least in the inlet flow paths, the inorganic particles having a D in the range of 5.0 to 14.0 microns. 90 and a layer of inorganic particles having the formula:

Description

[Technical field]

[0001] The present invention relates to a particulate filter for treating an exhaust stream from a gasoline engine comprising 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 technology]

[0002] Engine exhaust consists essentially of gaseous pollutants such as unburned hydrocarbons (HC), carbon monoxide (CO) and nitrogen oxides (NOx), as well as particulate matter (PM). For gasoline engines, three-way conversion catalysts (hereinafter interchangeably referred to as TWC catalysts or TWC) for gaseous pollutants and filters for particulate matter (PM) are well-known exhaust aftertreatment measures to ensure that exhaust gases meet emission regulations.

[0003] In contrast to the particulates produced by diesel lean-burn engines, particulates produced by gasoline engines, such as gasoline direct injection engines, tend to be finer and in smaller quantities. This is due to the different combustion conditions of gasoline engines compared to diesel engines. Also, the hydrocarbon components are different in gasoline engine emissions compared to diesel engines. Particulate filters specifically for gasoline engines have been developed over the decades to effectively treat engine exhaust from gasoline engines.

[0004] For example, WO 2018 / 024547 A1 describes a catalyzed particulate filter comprising a TWC catalytic material that permeates the walls of the particulate filter. Coating the TWC catalytic material on or within the filter may result in backpressure effects. To avoid excessive increases in backpressure while still providing full three-way conversion functionality, a specific coating scheme was proposed in the patent application. The catalyzed particulate filter is required to have a coated porosity that is smaller than the uncoated porosity of the particulate filter.

[0005] GB 2560663(B) describes a particulate filter for use in the exhaust treatment system of a gasoline engine, the filter having an inlet side and an outlet side, at least the inlet side containing particulate matter of less than D 90 and is loaded with synthetic ash including 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 stated 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 gasoline particulate filters improves over the life of the filter, mainly as a result of the accumulation of ash and soot on the inlet walls of the filter. It has also been determined that the particle count of emissions generated during the cold start phase of the test cycle represents a major portion of the total particles emitted during the test. Therefore, particle filtration performance during the initial filtration phase, also called fresh filtration efficiency, is a major concern for developing gasoline particulate filters.

[0007] As particulate emissions from gasoline engines are subject to stricter regulations, such as Euro 6 and China 6, vehicle manufacturers, i.e., original equipment manufacturers (OEMs), are requiring gasoline particulate filters to have high fresh filtration efficiency along with desirably low backpressure.

[0008] There is a need to provide an improved particulate filter for treating exhaust gases from a gasoline engine that can provide higher fresh filtration efficiency under low back pressure. Summary of the Invention

[0009] It is an object of the present invention to provide a particulate filter for treating the exhaust stream from a gasoline engine which provides higher fresh filtration efficiency without suffering from unacceptable backpressure rise.

[0010] Surprisingly, it has been found that the objects of the invention are achieved by a particulate filter comprising a layer of inorganic powder particles in the inlet flow path, the inlet flow path and / or the outlet flow path of the filter.

[0011] Thus, 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, a quantity of the flow paths being inlet flow paths that are open at the inlet end and closed at the outlet end, and a quantity of the flow paths being outlet flow paths that are closed at the inlet end and open at the outlet end; a layer of inorganic particles loaded on the surface of the porous walls in the inlet and / or outlet channels, Inorganic particles are in the range of D 5.0 ​​to 14.0 microns 90 The present invention provides a particulate filter having a

[0012] In a second aspect, the present invention provides a method for producing a particulate filter, comprising the steps of: - 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, a quantity of the flow paths being inlet flow paths that are open at the inlet end and closed at the outlet end, and a quantity of the flow paths being outlet flow paths that are closed at the inlet end and open at the outlet end; - applying inorganic particles onto the surface of the porous walls in the inlet and / or outlet channels, the inorganic particles having a D in the range of 5.0 to 14.0 microns; 90 and applying inorganic particles having a formula:

[0013] In a third aspect, the present invention provides an exhaust gas treatment system comprising a particulate filter according to the first aspect or obtainable or obtained from the method according to the second aspect, positioned downstream of a petrol engine.

[0014] In a fourth aspect, the present invention provides a method of treating an exhaust stream from a gasoline engine comprising contacting the exhaust stream with a particulate filter according to the first aspect or an exhaust treatment system according to the third aspect.

[0015] It has been found that a particulate filter for treating exhaust gases from a gasoline engine, also referred to herein as a gasoline particulate filter, can provide improved fresh filtration efficiency compared to its prior art counterparts, while no significant backpressure increase has been observed. [Brief description of the drawings]

[0016] [Figure 1] FIG. 1 shows an external view of a wall flow substrate having an inlet end and an outlet end. [Diagram 2] FIG. 1 illustrates a longitudinal cross-section of an exemplary wall-flow substrate having multiple porous walls extending longitudinally from the inlet end to the outlet end of the substrate. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] The present invention will be described in detail herein below. It should be understood that the present invention can be embodied in many different ways and should not be construed as being limited to the embodiments set forth herein.

[0018] The singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. Terms such as "comprise," "comprising," and the like are used interchangeably with "contain," "containing," and the like, and are to be interpreted in an open, non-restrictive manner; that is, for example, additional components or elements may be present. The expression "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 or pre-coated wall of a substrate. The layer may be in the form of particles packed onto the wall of the substrate, with gaps between them that allow gas to pass through.

[0020] "D 90 The terms " have their ordinary meaning, referring to the point in the cumulative particle size distribution where the cumulative volume from the small particle size end reaches 90%. 90 is a value determined by measuring the 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 describe the presence of the respective platinum group metal in any possible valence state, which may be, for example, the metal or metal oxide as a catalytically active form, or may be a metal compound, complex, etc. that decomposes or is otherwise converted to a catalytically active form, for example, upon calcination or use of the catalyst.

[0022] The term "support" refers to a material in particulate form for receiving and carrying one or more PGM components, and optionally one or more other components, such as stabilizers, promoters, and binders.

[0023] In this specification, g / ft 3 or g / in 3 References to loadings in units 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 paths extending from an inlet end to an outlet end, a quantity of the flow paths being inlet flow paths that are open at the inlet end and closed at the outlet end, and a quantity of the flow paths being outlet flow paths that are closed at the inlet end and open at the outlet end; a layer of inorganic particles loaded on the surface of the porous walls in the inlet and / or outlet channels, Inorganic particles are in the range of D 5.0 ​​to 14.0 microns 90 A particulate filter is provided having the following structure:

[0025] Substrate, as used herein, 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 which can also be loaded with functional materials, e.g., a filtration improving layer, such as a layer of inorganic particles as described herein, and optionally any other layers.

[0026] The substrate comprises a plurality of porous walls extending longitudinally to form a plurality of parallel flow passages extending from an inlet end to an outlet end, with a volume of the flow passages being inlet flow passages that open at the inlet end and close at the outlet end, and a volume of the flow passages different from the inlet flow passages being outlet flow passages that close at the inlet end and open at the outlet end. The substrate configuration, also referred to as a wall-flow substrate, requires that engine exhaust in the inlet flow passages flow through the porous walls of the substrate and into the outlet flow passages to reach the outlet end.

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

[0028] The porous wall of the substrate is generally made of ceramic or metal materials. 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.

[0029] Suitable metallic materials for constructing the substrate may include heat-resistant metals and metal alloys such as titanium and stainless steel, as well as other alloys in which iron is a substantial or major component. Such alloys may contain one or more of nickel, chromium, and / or aluminum, the total amount of these metals advantageously comprising at least 15% by weight of the alloy, for example 10-25% by weight chromium, 3-8% by weight aluminum, and up to 20% by weight 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 high temperatures, for example 1000° C. or higher, to form an oxide layer on the surface of the substrate to improve the corrosion resistance of the alloy and promote adhesion of the washcoat layer to the metal surface.

[0030] The closed end flow passage is filled with a plug of sealant material. Any suitable sealant material may be used without limitation.

[0031] The channels of the substrate can be of any suitable cross-sectional shape and size, such as circular, elliptical, triangular, rectangular, square, hexagonal, trapezoidal, or other polygonal. The substrate may have up to 700 channels (i.e., cells) per square inch of cross section. For example, the substrate may have 100 to 500 cells per square inch ("cpsi"), typically 200 to 400 cpsi. The walls of the substrate may have a variety of thicknesses, with typical ranges being 2 mils to 0.1 inches. Preferably, the substrate has a number of inlet channels equal to the number of outlet channels, and the channels are uniformly distributed throughout the substrate.

[0032] 1 and 2 show a typical wall-flow substrate that contains multiple inlet and outlet channels.

[0033] 1 shows an external view of a wall-flow substrate having an inlet end (01) where the exhaust stream (13) enters the substrate and an outlet end (02) where treated exhaust exits. Alternate flow paths are plugged to form a checkerboard pattern at the inlet end (01) as shown, and an opposite checkerboard pattern at the outlet end (02), not shown.

[0034] 2 shows a schematic longitudinal cross-section of a wall-flow substrate including a first plurality of flow channels (11) open at an inlet end (01) and closed at an outlet face (02), and a second plurality of flow channels (12) 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. 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.

[0035] The particulate filter according to the present invention may comprise a layer of inorganic particles loaded on the surface of the porous walls in the inlet and / or outlet flow paths. In other words, the layer of inorganic particles may be loaded on the porous walls only in the inlet flow paths, only in the inlet flow paths, or both inlet and outlet flow paths. In particular, the layer of inorganic particles may be loaded on the porous walls only in the inlet flow paths, or both inlet and outlet flow paths, more preferably only in the inlet flow paths.

[0036] The layer of inorganic particles is intended to be loaded onto the surface of the porous walls in the inlet and / or outlet flow paths, 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 in the porous walls.

[0037] Typically, the inorganic particles comprise one or more 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. Preferably, the inorganic particles comprise alumina, zinc oxide, zirconia, or combinations or composites thereof. More preferably, the inorganic particles comprise alumina.

[0038] The inorganic particles may optionally comprise a PGM component, such as a palladium component and / or a platinum component, which, when present, may be supported on a non-PGM component as described above or may be present separate from the non-PGM components.

[0039] As used herein, the layer of inorganic particles loaded on the porous walls in the inlet and / or outlet channels of the substrate refers specifically to a layer that exhibits little or no, preferably no, TWC activity, although it may exhibit certain catalytic activity when one or more PGM components are included in the inorganic particles.

[0040] In some embodiments, the inorganic particles are free of PGM components and preferably comprise alumina, zirconia, ceria, silica, titania, magnesium oxide, zinc oxide, zinc carbonate, calcium oxide, calcium carbonate, silicate zeolite, aluminosilicate zeolite, or combinations or composites thereof, of which alumina, zinc oxide, zirconia, or combinations or composites thereof are more preferred, and alumina is most preferred.

[0041] The present inventors have 90It has been found that the particle size distribution of the inorganic particles represented by the following formula (1) is an important factor affecting the fresh filtration efficiency of the particulate filter according to the present invention.

[0042] Therefore, the inorganic particles loaded on the porous walls in the inlet and / or outlet channels of the substrate have a D in the range of 5.5-9.5 μm. 90 It is preferred that the compound has the formula:

[0043] More preferably, the inorganic particles loaded on the porous walls in the inlet and / or outlet channels of the substrate have a D in the range of 5.8 to 9.0 μm. 90 has.

[0044] Particulate filters are 0.005 to 0.83 g / in 3 (i.e., about 0.3 to 50 g / L), or 0.01 to 0.33 g / in 3 (i.e., about 0.6 to 20 g / L), or 0.02 to 0.17 g / in 3 (i.e., about 1.2 to 10 g / L), or 0.025 to 0.1 g / in 3 (i.e., about 1.5-6 g / L) of inorganic particles.

[0045] The layer of inorganic particles may be applied onto the surface of the porous walls of the substrate by any known process, such as dry coating and washcoat processes.

[0046] Dry coating processes are well known and are generally carried out by blowing inorganic particles or suitable precursors thereof in particulate form into the channels of the substrate through an open end by a carrier gas stream and then firing the coated substrate. With this process, no liquid carrier is used. The inorganic particles are typically distributed on the surface of the porous walls of the channels in the form of a particle bed.

[0047] In some embodiments, inorganic particles or suitable precursors thereof may be injected into the inlet channel from the open end of the channel toward the closed end. The particle bed formed in the inlet channel may be disposed on the porous walls of the inlet channel or against a plug blocking the channel. As discussed above, the particulate bed, i.e., the layer of inorganic particles, is gas permeable, which may contribute to the capture of particulate matter (PM) in the exhaust stream and allow gaseous pollutants in the exhaust stream to pass therethrough.

[0048] The layer of inorganic particles in the form of a particle bed may extend along the porous walls of the flow 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 walls of the flow channel or along only a portion of the length of the porous walls of the flow channel.

[0049] Washcoating processes are also well known and are generally carried out by coating a slurry containing inorganic particles or suitable precursors thereof and any auxiliary agents in a liquid solvent (e.g., water) into the channels of the substrate from an open end, and drying and firing the coated substrate. 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 channels in which the inorganic particles are loaded. Also, the porous coating may extend along the entire length of the porous walls of the channels or only along a portion of the length of the porous walls of the channels.

[0050] Particulate filters according to the present invention may further comprise a TWC coating in at least a portion of the inlet and / or outlet flow paths of the substrate. In particular, the TWC coating is present in both the inlet and outlet flow paths of the substrate.

[0051] The TWC coat is typically in the form of a washcoat, also called an "in-wall" coat, that includes the TWC composition.

[0052] It will be understood that although the TWC coat is intended to be loaded into the pores of the porous walls of the flow passages, a significant amount of the TWC composition may also be found on the surfaces of the porous walls within the coated flow passages.

[0053] There is no particular limit to the TWC composition useful for the TWC coating contained in the particulate filter.Typically, the TWC composition includes a platinum group metal component as a catalytically active species, such as a rhodium component, and one or both of a platinum component and a palladium component, which are supported on a support particle.Materials useful as a support may be refractory metal oxides, oxygen storage components, and any combination thereof.

[0054] Examples of refractory metal oxides may include, but are not limited to, alumina, lanthana-doped alumina, baria-doped alumina, ceria-doped alumina, zirconia-doped alumina, ceria-zirconia-doped alumina, lanthana-zirconia-doped alumina, baria-lanthana-doped alumina, baria-ceria-doped alumina, baria-zirconia-doped alumina, baria-lanthana-neodymia-doped alumina, lanthana-ceria-doped alumina, and any combination thereof.

[0055] Examples of oxygen storage components (OSCs) 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.

[0056] The particulate filter of the present invention has a particle size 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 49-122 g / L) of TWC coat.

[0057] TWC coating has a range of 1.0 to 50.0 g / ft2 calculated for each PGM element.3 (i.e., about 0.04 to 1.8 g / L), or 5.0 to 20.0 g / ft 3 (i.e., about 0.18-0.71 g / L) total loading of PGM components.

[0058] The TWC coat may be applied onto the substrate by any known process, typically by a washcoat process, which is generally carried out by coating a slurry containing TWC catalyst particles of the supported PGM components in a solvent (e.g. water) and optionally coagents, and drying and calcining the coated substrate.

[0059] The TWC coat, if present, is applied onto the substrate prior to loading with the layer of inorganic particles as described above.

[0060] In some exemplary embodiments, a particulate filter according to the present invention comprises: - 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, a quantity of the flow paths being inlet flow paths that are open at the inlet end and closed at the outlet end, and a quantity of the flow paths being 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 at least in the inlet channel; - optionally provided with a TWC coat, preferably a washcoat comprising a TWC composition; Inorganic particles are in the range of D 5.0 ​​to 14.0 microns. 90 and includes alumina, zirconia, ceria, silica, titania, magnesium oxide, zinc oxide, zinc carbonate, calcium oxide, calcium carbonate, silicate zeolite, aluminosilicate zeolite, or a combination or composite thereof.

[0061] In a further exemplary embodiment, the particulate filter according to the present invention comprises: - 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, a quantity of the flow paths being inlet flow paths that are open at the inlet end and closed at the outlet end, and a quantity of the flow paths being 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 at least in the inlet channel; - optionally comprising a washcoat comprising a TWC composition; Inorganic particles are in the range of 5.5 to 9.5 microns D 90 and includes alumina, zinc oxide, zirconia, or a combination or composite thereof.

[0062] In some other exemplary embodiments, a particulate filter according to the present invention comprises: - 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, a quantity of the flow paths being inlet flow paths that are open at the inlet end and closed at the outlet end, and a quantity of the flow paths being 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 at least in the inlet channel; - optionally comprising a washcoat comprising a TWC composition; Inorganic particles are in the range of 5.8 to 9.0 microns D 90 and includes alumina, zinc oxide, zirconia, or a combination or composite thereof.

[0063] In the exemplary embodiment described above, the layer of inorganic particles is preferably free of PGM components.

[0064] The particulate filter may be housed within a shell having an inlet and an outlet for the exhaust flow, which may be operatively associated with and in fluid communication with other portions of the engine's exhaust system.

[0065] According to a second aspect of the present invention, there is provided a method for producing a particulate filter, comprising the steps of: - 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, a quantity of the flow paths being inlet flow paths that are open at the inlet end and closed at the outlet end, and a quantity of the flow paths being outlet flow paths that are closed at the inlet end and open at the outlet end; - applying inorganic particles onto the surface of the porous walls in the inlet and / or outlet channels, the inorganic particles having a diameter of 5.0 to 14.0 microns (μm), preferably 5.5 to 9.5 μm, more preferably 5.8 to 9.0 μm. 90 and applying inorganic particles having a molecular weight of about 1.0 to about 1.0.

[0066] The inorganic particles may be applied onto the surface of the porous wall by a dry coating process or washcoat as described above in the first embodiment, preferably by a dry coating process.

[0067] In some embodiments, the method of making a particulate filter further comprises applying a TWC coating to at least some of the porous walls of the inlet and / or outlet flow paths of the substrate prior to applying the inorganic particles onto the surfaces of the porous walls. The TWC coating may be applied by the washcoat process described above.

[0068] Any general descriptions and selections made above regarding the inorganic particles and the TWC coat in the first embodiment are applicable herein by reference.

[0069] According to a third aspect, there is provided an exhaust gas treatment system comprising a particulate filter according to the first aspect or obtainable or obtained from the method according to the second aspect, positioned downstream of a petrol engine.

[0070] According to a fourth aspect, there is provided a method of treating an exhaust stream from a gasoline engine comprising contacting the exhaust stream with a particulate filter according to the first aspect or an exhaust treatment system according to the third aspect.

[0071] 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.

[0072] Embodiment 1. 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, a quantity of the flow paths being inlet flow paths that are open at the inlet end and closed at the outlet end, and a quantity of the flow paths being outlet flow paths that are closed at the inlet end and open at the outlet end; a layer of inorganic particles loaded on the surface of the porous walls in the inlet and / or outlet channels, preferably at least in the inlet channels, Inorganic particles are in the range of D 5.0 ​​to 14.0 microns 90 A particulate filter comprising:

[0073] Embodiment 2. The particulate filter of embodiment 1, wherein the inorganic particles comprise one or more 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.

[0074] Embodiment 3. The particulate filter of embodiment 2, wherein the inorganic particles comprise alumina, zinc oxide, zirconia, or a combination or composite thereof.

[0075] Embodiment 4. A particulate filter as described in embodiment 3, wherein the inorganic particles comprise alumina.

[0076] Embodiment 5. A particulate filter according to any one of embodiments 1 to 4, wherein the layer of inorganic particles does not exhibit three-way conversion catalytic activity.

[0077] Embodiment 6. A particulate filter according to any one of embodiments 1 to 5, wherein the layer of inorganic particles is free of PGM components.

[0078] Embodiment 7. The inorganic particles have a D in the range of 5.5 to 9.5 microns. 90 The particulate filter according to any one of embodiments 1 to 6, comprising:

[0079] Embodiment 8. The inorganic particles have a D in the range of 5.8 to 9.0 microns. 90 8. The particulate filter of embodiment 7, comprising:

[0080] Embodiment 9. The particulate filter of any one of embodiments 1-8, further comprising a three-way catalyst (TWC) coat, preferably a washcoat comprising a TWC composition.

[0081] Embodiment 10. A particulate filter as defined in embodiment 9, wherein a three-way conversion catalyst coating is on at least a portion of the inlet and / or outlet flow paths of the substrate.

[0082] Embodiment 11. The layer of inorganic particles is formed at a density of 0.005 to 0.83 g / in 3 (i.e., about 0.3 to 50 g / L), or 0.01 to 0.33 g / in 3 (i.e., about 0.6 to 20 g / L), or 0.02 to 0.17 g / in 3 (i.e., about 1.2 to 10 g / L), or 0.025 to 0.1 g / in 3 (i.e., about 1.5-6 g / L).

[0083] Embodiment 12. A particulate filter according to any one of embodiments 1 to 11, which is a gasoline particulate filter.

[0084] Embodiment 13. A method for producing a particulate filter according to any one of embodiments 1 to 12, comprising the steps of: - 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, a quantity of the flow paths being inlet flow paths that are open at the inlet end and closed at the outlet end, and a quantity of the flow paths being outlet flow paths that are closed at the inlet end and open at the outlet end; - applying inorganic particles onto the surface of the porous walls in the inlet and / or outlet channels, the inorganic particles having a diameter of 5.0 to 14.0 microns, preferably 5.5 to 9.5 μm, more preferably 5.8 to 9.0 μm. 90 and applying inorganic particles having a formula:

[0085] Embodiment 14. The method of embodiment 13, wherein the inorganic particles are applied by a dry coating process or a washcoat process, preferably by a dry coating process.

[0086] Embodiment 15. The method of claim 14, wherein the inorganic particles are applied by using inorganic particles or precursors thereof.

[0087] Embodiment 16. An exhaust gas treatment system comprising a particulate filter according to any one of embodiments 1 to 12 or a particulate filter obtainable or obtained by the method according to any one of embodiments 13 to 15, located downstream of a gasoline engine.

[0088] Embodiment 17. A method for treating an exhaust stream from a gasoline engine comprising contacting the exhaust stream with a particulate filter as described in any one of embodiments 1 to 12 or an exhaust treatment system as described in embodiment 16. EXAMPLES

[0089] Aspects of the present invention will be more fully described by the following examples, which are provided to illustrate certain aspects of the invention and should not be construed as limiting thereof.

[0090] I. Preparation of Particulate Filter Reference example 1 A gasoline particulate filter cordierite substrate obtained from Corning was used as the reference filter (blank filter), which had a size of 143.8 mm (D) × 123.2 mm (L) and a volume of 2.0 L (approximately 122.1 in 3 ), a cell density of 300 cells per square inch (cpsi), a wall thickness of 8 mils, a porosity of 65%, and an average pore size of 20 μm in diameter as determined by mercury intrusion measurements.

[0091] Comparative Example 1 A TWC-coated particulate filter was prepared from the same filter substrate as the blank filter of Example 1 by applying a TWC washcoat to both the inlet and outlet channels of the blank filter.

[0092] 30.22 g of 9.68 wt% rhodium nitrate aqueous solution 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 incipient wetness. 14.27 g of 20.5 wt% palladium nitrate aqueous solution was impregnated onto 711 g of 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 1280 g of deionized water, to which 78 g of barium hydroxide octahydrate and 66 g of 21.5 wt% zirconium nitrate aqueous solution were added. The pH of the slurry was adjusted to 3.6 with nitric acid. The slurry was mixed to obtain a particle size D of 4.5 μm. 90 The substrate was ground to a powder and then coated into the inlet and outlet channels of a blank filter at 50% washcoat loading and into the outlet channel of a blank filter at the remaining 50% washcoat 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.

[0093] Approximately 0.99g / in 3(60g / L) washcoat loading and approximately 10.0g / ft 3 An in-wall TWC coat was obtained using a total PGM loading of (about 0.35 g / L) and a Pd / Rh ratio of 5 / 5.

[0094] Comparative Example 2 A particulate filter was prepared having a TWC coating and a layer of inorganic particles.

[0095] First, a particulate filter with a TWC coating was prepared by repeating the same process as described in Comparative Example 1. Then, high surface area gamma alumina powder was mixed with a carrier gas and heated at 600 m at room temperature. 3 The alumina powder was blown into the inlet channel of the filter at a flow rate of 100000 / h. The alumina powder had a particle size D of 4.8 μm as measured by a Sympatec HELOS laser diffraction particle size analyzer. 90 The specific surface area after calcination at 1100°C for 4 hours in air (BET model, 77K nitrogen adsorption measurement) is 61m 2 After coating, the filter with the layer of inorganic particles in the inlet channels was baked at a temperature of 450° C. for 30 minutes. The loading of alumina particles in the layer of inorganic particles was 3 g / L (0.05 g / in 3 ) was.

[0096] Comparative Example 3 Alumina powder with a particle size of 15.2 μm D 90 A particulate filter having a TWC coat and a layer of inorganic particles was prepared by repeating the same process as described in Comparative Example 2, except that the TWC coat and the inorganic particles were dry-milled.

[0097] Example 1 of the present invention Alumina powder with a particle size of 5.8 μm D 90 A particulate filter having a TWC coat and a layer of inorganic particles was prepared by repeating the same process as described in Comparative Example 2, except that the TWC coat and the inorganic particles were dry-milled.

[0098] Example 2 of the present invention Alumina powder with a particle size of 9.0 μm D90 A particulate filter having a TWC coat and a layer of inorganic particles was prepared by repeating the same process as described in Comparative Example 2, except that the TWC coat and the inorganic particles were dry-milled.

[0099] II.Filtration performance II.1 Back pressure The particulate filter from the above example was 3 The back pressure measured by a SuperFlow SF-1020 flow bench under a cold air flow of 10000 / h was investigated.

[0100] II.2 Filtration efficiency According to the standard procedure defined in "BS EN ISO 29463-5:2018-Part 5:Test method for filter elements", 3 The filtration efficiency of the particulate filters from the above examples in a fresh state (0 km, or unused state) was measured using di(2-ethyl-hexyl) sebacate aerosol as particles on a stationary air filter performance test bench with a cold air flow of 10000 / h. The particle number (PN) of particles in the range of 0.10-0.15 μm was recorded by a PN counter both upstream and downstream of the tested filter. The fresh filtration efficiency (FFE) was calculated according to the following formula:

[0101]

number

[0102] The test results for each particulate filter from the above examples are summarized in the table below.

[0103] [Table 1]

[0104] A comparison between Comparative Example 1 and Reference Example 1 shows that the particulate filter with the TWC coating has a lower fresh filtration efficiency (FFE) than the blank filter, but maintains a comparable low backpressure, which is due to the TWC component penetrating the porous walls of the particulate filter substrate.

[0105] Fresh filtration efficiency may be improved, with a tolerable increase in backpressure, by applying a layer of inorganic particles onto the porous walls of the inlet flow passages of the particulate filter substrate, as shown in Comparative Examples 2 and 3.

[0106] Surprisingly, the fresh filtration efficiency was improved by the D of inorganic particles applied onto the porous walls of the substrate of the particulate filter. 90 It has been found that this can be further improved by controlling the D 90 The particulate filter of Comparative Example 2 having a layer of small (4.8 μm) inorganic particles and 90 The fresh filtration efficiency was maintained without significant increase, although it was clearly higher than that of the particulate filter of Comparative Example 3 having a layer of large (15.2 μm) inorganic particles.

[0107] Although the invention herein has been described with reference to particular 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 present invention without departing from the spirit and scope of the invention. Thus, it is intended that the present invention cover modifications and variations that come within the scope of the appended claims and their equivalents.

Claims

1. 1. A particulate filter comprising: a substrate comprising a plurality of porous walls extending longitudinally to define a plurality of parallel flow paths extending from an inlet end to an outlet end, a quantity of the flow paths being inlet flow paths that open at the inlet end and close at the outlet end, and a quantity of the flow paths being outlet flow paths that close at the inlet end and open at the outlet end; a layer of inorganic particles loaded on the surface of the porous walls in the inlet and / or outlet channels, preferably at least in the inlet channels; The inorganic particles have a D in the range of 5.0 to 14.0 microns. ９０ A particulate filter comprising:

2. 2. The particulate filter of claim 1, wherein the inorganic particles comprise one or more 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.

3. 3. The particulate filter of claim 2, wherein the inorganic particles comprise alumina, zinc oxide, zirconia, or a combination or composite thereof.

4. 4. The particulate filter of claim 3, wherein said inorganic particles comprise alumina.

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

6. A particulate filter according to any one of claims 1 to 5, wherein the layer of inorganic particles is free of PGM components.

7. The inorganic particles have a D in the range of 5.5 to 9.5 microns. ９０ The particulate filter according to any one of claims 1 to 6, comprising:

8. The inorganic particles have a D in the range of 5.8 to 9.0 microns. ９０ 8. The particulate filter of claim 7, having

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

10. 10. The particulate filter of claim 9, wherein the three-way catalyst coating is on at least a portion of the inlet and / or outlet flow passages of the substrate.

11. The layer of inorganic particles is formed at a density of 0.005 to 0.83 g / in ３ (i.e., about 0.3 to 50 g / L), or 0.01 to 0.33 g / in ３ (i.e., about 0.6 to 20 g / L), or 0.02 to 0.17 g / in ３ (i.e., about 1.2 to 10 g / L), or 0.025 to 0.1 g / in ３ 11. The particulate filter of any one of claims 1 to 10, comprising a loading of about 1.5 to 6 g / L.

12. A particulate filter according to any preceding claim which is a gasoline particulate filter.

13. A method for producing a particulate filter according to any one of claims 1 to 12, comprising the steps of: 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, a quantity of the flow paths being inlet flow paths that are open at the inlet end and closed at the outlet end, and a quantity of the flow paths being outlet flow paths that are closed at the inlet end and open at the outlet end; applying inorganic particles onto the surface of the porous walls in the inlet and / or outlet channels, said inorganic particles having a D in the range of 5.0 to 14.0 microns, preferably 5.5 to 9.5 μm, more preferably 5.8 to 9.0 μm; ９０ and applying inorganic particles having a molecular weight of about 1.0 to about 1.

0.

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

15. The method of claim 14 , wherein the inorganic particles are applied using the inorganic particles or precursors thereof.

16. 16. An exhaust gas treatment system comprising a particulate filter according to any one of claims 1 to 12 or a particulate filter obtainable or obtained from the method according to any one of claims 13 to 15 positioned downstream of a petrol engine.

17. A method of treating an exhaust stream from a gasoline engine comprising contacting the exhaust stream with a particulate filter according to any one of claims 1 to 12 or an exhaust treatment system according to claim 16.

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