Gasoline particle filter

Abstract

The present invention relates to a particulate filter comprising: a substrate comprising a plurality of longitudinally extending porous walls to form a plurality of parallel channels extending from an inlet end to an outlet end wherein a number of channels are inlet channels open at the inlet end and closed at the outlet end, a certain number of channels are outlet channels which are closed at the inlet ends and open at the outlet ends; and a layer of inorganic particles supported on the surface of the porous wall in the inlet channel and / or the outlet channel, where the layer of inorganic particles comprises inorganic particles having a small BET pore volume of not more than 0.5 cm3 / g. The invention also relates to a method for producing a particulate filter comprising applying inorganic particles or precursors thereof on the surface of the porous walls in the inlet channel and / or the outlet channel to deposit an inorganic particle layer comprising inorganic particles having a small BET pore volume.

Description

Technical Field

[0001] The present invention relates to a particulate filter for treating an exhaust gas flow from a gasoline engine, the particulate filter comprising a coating of inorganic powder particles. The present invention also relates to a gasoline engine emission treatment system comprising a particulate filter and a method for treating an exhaust gas flow from a gasoline engine. Background Art

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

[0003] In contrast to the particles generated by diesel lean-burn engines, the particles generated by gasoline engines (such as direct injection engines) tend to be finer and fewer in number. This is because the combustion conditions of gasoline engines are different from those of diesel engines. In addition, the hydrocarbon composition in gasoline engine emissions is different compared to diesel engines. Particulate filters specifically for gasoline engines have been developed for decades in order to effectively treat the engine exhaust from gasoline engines.

[0004] For example, WO 2018 / 024547A1 describes a catalytic particle filter including a TWC catalytic material that penetrates the particle filter wall. Coating the TWC catalytic material on or in the filter may result in back pressure effects. In this patent application, a special coating scheme is proposed to avoid excessive increase in back pressure while providing full three-way conversion function. It is required that the coated porosity of the catalytic particle filter is less than the uncoated porosity of the particle filter.

[0005] WO2018 / 115900A1 describes a particle filter for use in an emission treatment system for a gasoline engine, the particle filter having an inlet side and an outlet side, wherein at least the inlet side is loaded with synthetic ash, the synthetic ash comprising one or more of aluminum oxide, zinc oxide, zinc carbonate, calcium oxide, calcium carbonate, cerium zirconium (mixed) oxide, zirconium oxide, cerium oxide, and hydrated aluminum oxide. 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 well known that the filtration performance of a gasoline particulate filter will improve with increasing filter life, primarily due to the accumulation of ash and soot on the walls of the filter inlet side. In addition, it has been identified that the number of emission particles generated during the cold start phase of the test cycle represents a major portion of the total particles emitted during the test. Therefore, the particle filtration performance during the initial filtration phase, also known as fresh filtration efficiency, is a major focus in the development of gasoline particulate filters.

[0007] As particulate emissions from gasoline engines are regulated by stricter regulations, such as Euro 6 and National 6, vehicle manufacturers, ie, original equipment manufacturers (OEMs), require gasoline particulate filters to have high fresh filtration efficiency and desirably low back pressure.

[0008] It would be desirable to provide an improved particulate filter for treating an exhaust gas flow from a gasoline engine that can provide higher fresh filter efficiency at relatively low back pressures. Summary of the invention

[0009] It is an object of the present invention to provide a particle filter for treating an exhaust gas flow from a gasoline engine which particle filter provides a higher fresh filter efficiency without suffering from an unacceptable increase in back pressure.

[0010] It has surprisingly been found that the objects of the invention are achieved by a particle filter comprising an inorganic particle layer which contains particles with a small pore volume in the inlet channel and / or outlet channel of the filter.

[0011] Thus, in a first aspect, the present invention provides a particle filter comprising - a substrate comprising a plurality of longitudinally extending porous walls to form a plurality of parallel channels extending from an inlet end to an outlet end, wherein a certain number of said channels are inlet channels open at the inlet end and closed at the outlet end, and a certain number of said channels are outlet channels closed at said inlet end and open at said outlet end; and

[0012] - a layer of inorganic particles supported on the surface of the porous wall in the inlet channel and / or the outlet channel,

[0013] The inorganic particle layer comprises particles not larger than 0.5 cm 3 In a second aspect, the present invention provides a method for producing a particle filter, the method comprising:

[0014] - providing a substrate comprising a plurality of longitudinally extending porous walls to form a plurality of parallel channels extending from an inlet end to an outlet end, wherein a certain number of the channels are inlet channels that are open at the inlet end and closed at the outlet end, and a certain number of the channels are outlet channels that are closed at the inlet end and open at the outlet end,

[0015] - applying inorganic particles or precursors thereof to the surface of the porous walls in the inlet channel and / or the outlet channel, and

[0016] - optionally, drying and / or calcining,

[0017] The deposit contains no more than 0.5cm 3 The inorganic particle layer comprises inorganic particles with a small BET pore volume of / g.

[0018] In a third aspect, the present invention provides an exhaust gas treatment system comprising a particle filter as described in the first aspect or a particle filter obtainable or obtained by the method as described in the second aspect, the particle filter being located downstream of a gasoline engine.

[0019] In a fourth aspect, the present invention provides a method for treating an exhaust flow from a gasoline engine, the method comprising contacting the exhaust flow with a particulate filter as described in the first aspect, a particulate filter obtainable or obtained by the method as described in the second aspect, or an exhaust treatment system as described in the third aspect.

[0020] 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 corresponding filters of the prior art, while no significant backpressure increase is observed. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 An external view of a wall flow substrate having an inlet end and an outlet end is illustrated.

[0022] Figure 2 A longitudinal cross-sectional view of an exemplary wall flow substrate having a plurality of porous walls extending longitudinally from an inlet end to an outlet end of the substrate is illustrated. DETAILED DESCRIPTION

[0023] The present invention is described in detail below. It should be understood that the present invention can be embodied in many different ways and should not be construed as being limited to the embodiments set forth herein.

[0024] The singular forms "a", "an", and "the" include plural referents unless the context clearly dictates otherwise. The terms "comprising", "including", and the like are used interchangeably with "containing", and are to be interpreted in a non-limiting, open-ended manner. That is, for example, additional components or elements may be present. The expression "consisting of" or cognates may be encompassed by "comprising" or cognates.

[0025] In this document, the term "layer", for example in the context of an inorganic particle layer, is intended to mean a thin coating of a gas permeable material carried on a blank or pre-coated wall of a substrate. The layer may be in the form of packed particles on the walls of the substrate with gaps therebetween to allow gas to permeate through.

[0026] The term "D 10 ”, “D 50 ” and “D 90 " have their usual meanings, namely, refer to the points at which the cumulative volume from the small particle diameter side reaches 10%, 50% and 90% in the cumulative particle size distribution. The particle size distribution is measured using a laser diffraction particle size distribution analyzer.

[0027] Terms such as "palladium component," "platinum component," and "rhodium component" are intended to describe the various platinum group metals present in any possible valence state, which may be, for example, the metal or metal oxide in a catalytically active form, or may be, for example, a metal compound, complex, etc., which decomposes or is otherwise converted to a catalytically active form upon calcination or use of the catalyst.

[0028] The term "support" refers to a material in particulate form used to receive and support one or more platinum group metal (PGM) components, and optionally one or more other components, such as stabilizers, promoters and binders.

[0029] In this article, any reference to "g / ft 3 ” or “g / in 3 References to loadings in units of "are intended to mean the weight of a particular component, coating or layer per unit volume of the substrate or substrate portion on which it is supported.

[0030] According to a first aspect of the present invention, there is provided a particle filter, the particle filter comprising:

[0031] - a substrate comprising a plurality of longitudinally extending porous walls to form a plurality of parallel channels extending from an inlet end to an outlet end, wherein a certain number of the channels are inlet channels open at the inlet end and closed at the outlet end, and a certain number of the channels are outlet channels closed at the inlet end and open at the outlet end; and

[0032] - a layer of inorganic particles supported on the surface of the porous wall in the inlet channel and / or the outlet channel,

[0033] The inorganic particle layer comprises particles not larger than 0.5 cm 3 Inorganic particles with small BET pore volume of 1.1447 W / g.

[0034] As used herein, substrate refers to a structure suitable for withstanding the conditions encountered in the exhaust flow of an internal combustion engine, which can itself serve as a particulate filter, and can also carry functional materials, such as a filtration improvement layer, such as the inorganic particle layer described herein, and optionally any other layers.

[0035] The substrate includes a plurality of longitudinally extending porous walls to form a plurality of parallel channels extending from an inlet end to an outlet end, wherein a certain number of the channels are inlet channels that are open at the inlet end and closed at the outlet end, and a certain number of the channels other than the inlet channels are outlet channels that are closed at the inlet end and open at the outlet end. The configuration of the substrate is also referred to as a wall-flow substrate, requiring that the engine exhaust gas in the inlet channel flows through the porous walls into the outlet channel to reach the outlet end of the substrate.

[0036] Generally speaking, the substrate may exhibit a honeycomb structure having alternating channels plugged with plugs at opposite ends.

[0037] The porous wall of the substrate is generally made of ceramic material or metal material.

[0038] Suitable ceramic materials that can be used to construct the substrate can include any suitable refractory material, such as cordierite, mullite, cordierite-alumina, silicon carbide, silicon nitride, zirconium oxide, mullite, spodumene, alumina-silica-magnesia, zirconium silicate, magnesium silicate, sillimanite, petalite, alumina, aluminum titanate and aluminosilicates. Typically, the porous wall of the substrate is made of cordierite or silicon carbide.

[0039] Suitable metal materials that can be used to construct substrates can include heat-resistant metals and metal alloys, such as titanium and stainless steel and other alloys with iron as the basic or main component. Such alloys can contain one or more of nickel, chromium and / or aluminum, and the total amount of these metals can advantageously account for at least 15% by weight of the alloy, such as 10% to 25% by weight of chromium, 3% to 8% by weight of aluminum and up to 20% by weight of nickel. The alloy may also contain a small amount or trace of one or more metals, such as manganese, copper, vanadium, titanium, etc. The surface of the metal substrate can be oxidized at high temperatures (e.g., 1000° C. or higher) to form an oxide layer on the surface of the substrate, thereby improving the corrosion resistance of the alloy and promoting the adhesion of any coating to the metal surface.

[0040] The passage at the closed end is plugged with a plunger made of a sealing material. Any suitable sealing material may be used without limitation.

[0041] The channels of the substrate can have any suitable cross-sectional shape and size, such as circular, oval, triangular, rectangular, square, hexagonal, trapezoidal or other polygons. The substrate can have up to 700 channels (i.e., holes) per square inch of cross section. For example, the substrate can have 100 holes / square inch to 500 holes / square inch ("cpsi"), typically with 200cpsi to 400cpsi. The walls of the substrate can have different thicknesses, with a typical range of 2 mils to 0.1 inches. Preferably, the substrate has a number of inlet channels equal to the number of outlet channels, and the channels are evenly distributed throughout the substrate.

[0042] Figure 1 and Figure 2 A typical wall-flow substrate comprising a plurality of inlet channels and outlet channels is illustrated.

[0043] Figure 1 Depicted is an external view of a wall flow substrate having an inlet end (01) from which an exhaust gas stream (13) enters the substrate and an outlet end (02) from which the treated exhaust gas exits. Alternating channels are plugged with plungers to form a checkerboard pattern at the inlet end (01) shown and an opposing checkerboard pattern at the outlet end (02) not shown.

[0044] Figure 2 A longitudinal cross-sectional view of a wall-flow substrate is schematically depicted, the wall-flow substrate comprising a first plurality of channels (11) opening at an inlet end (01) and closed at an outlet end (02) and a second plurality of channels (12) opening at the outlet end (02) and closed at the inlet end (01). The channels are preferably parallel to each other to form a constant wall thickness between the channels. An exhaust gas flow entering the first plurality of channels from the inlet end cannot leave the substrate without diffusing through the porous wall (10) into the second plurality of channels.

[0045] The particle filter according to the present invention may include an inorganic particle layer on the surface of the porous wall in the inlet channel and / or the outlet channel. In other words, the inorganic particle layer can be loaded on the porous wall in the inlet channel alone, loaded on the porous wall in the outlet channel alone, or loaded on the porous wall in both the inlet channel and the outlet channel. In particular, the inorganic particle layer can be loaded on the porous wall in the inlet channel alone, or loaded on the porous wall in both the inlet channel and the outlet channel, more preferably loaded on the porous wall in the inlet channel alone.

[0046] It is understood that the inorganic particle layer is intended to be loaded onto the surface of the porous walls in the inlet and / or outlet channels, also referred to as an "on-wall" coating, while small amounts of inorganic particles may penetrate into the pores within the porous walls.

[0047] According to the present invention, inorganic particles, in particular particles having a diameter not greater than 0.5 cm 3 Inorganic particles with a small BET pore volume of 100 g / g (also referred to herein as "inorganic particles with a small pore volume") may be particles of a non-PGM inorganic material. The non-PGM inorganic material may be, for example, alumina, hydrated alumina, boehmite, zirconia, cerium dioxide, silicon dioxide, titanium dioxide, magnesium oxide, zinc oxide, zinc carbonate, calcium oxide, calcium carbonate, silicate zeolite, aluminosilicate zeolite, or a combination or composite thereof.

[0048] Therefore, the inorganic particles with small pore volume can be particulate non-PGM inorganic materials 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 their combinations or composites.

[0049] Preferably, the inorganic particles, especially inorganic particles with a small pore volume, are non-PGM inorganic materials selected from alumina, hydrated alumina, boehmite, silica, zinc oxide, zirconium oxide or a combination or composite thereof, more preferably selected from particles of alumina, silica or a combination or composite thereof.

[0050] The inorganic particle layer may optionally contain a PGM component, such as a palladium component and / or a platinum component. The PGM component (if present) may be supported on particles of a non-PGM inorganic material having a small pore volume as described above, or may be separated from particles of a non-PGM inorganic material having a small pore volume.

[0051] Herein, the inorganic particle layer supported on the porous walls in the inlet and / or outlet channels of the substrate refers particularly to a layer exhibiting little or no, preferably no TWC activity, but may exhibit certain catalytic activity if one or more PGM components are included in the inorganic particles.

[0052] In some embodiments, the inorganic particle layer does not include a PGM component.Preferably, the inorganic particle layer may be mainly or substantially composed of inorganic particles having a small pore volume.

[0053] As used herein, any reference to "consisting mainly of" in the context of an inorganic particle layer is intended to mean that the inorganic particle layer contains a major amount, i.e., greater than 50% by volume, of inorganic particles having a specified pore volume, which may be, for example, 75% by volume or more, 85% by volume or more, 90% by volume or more, or even 95% by volume or more.

[0054] In this document, any reference to "consisting essentially of" in the context of an inorganic particle layer is intended to mean that the inorganic particle layer contains an unintentionally added amount of inorganic particles other than inorganic particles having a specified small pore volume. In this document, the term "unintentionally added amount" is intended to mean no more than 1 volume %, no more than 0.5 volume %, no more than 0.1 volume %, or no more than 0.05 volume.

[0055] The present inventors have found that a pore volume having a small pore volume, i.e., a BET pore volume not greater than 0.5 cm 3 / g (as determined by nitrogen adsorption) can have a favorable effect on the fresh filtration efficiency of the particle filter. For example, special mention may be made of small BET pore volumes of not more than 0.3 cm 3 / g or not more than 0.2cm 3 / g (as determined by nitrogen adsorption) of inorganic particles.

[0056] Inorganic particles, particularly those with a small pore volume, may have a pore volume of at least 60 m / s as determined by nitrogen adsorption. 2 / g BET surface area, which is particularly useful for the present invention. For example, inorganic particles, especially inorganic particles with a small pore volume, can have a BET surface area of ​​at least 80 m 2 / g or at least 90m 2 / g of BET surface area.

[0057] In some embodiments, the inorganic particle layer comprises a small BET pore volume no greater than 0.5 cm 3 / g and a BET surface area of ​​at least 60 m 2 / g of inorganic particles.

[0058] In some other embodiments, the inorganic particle layer comprises a small BET pore volume of no greater than 0.3 cm 3 / g and a BET surface area of ​​at least 80 m 2 / g of inorganic particles.

[0059] In some further embodiments, the inorganic particle layer comprises a small BET pore volume no greater than 0.2 cm 3 / g and a BET surface area of ​​at least 90 m 2 / g of inorganic particles.

[0060] The inorganic particles useful in the present invention, particularly those with a small pore volume, may have a D of no greater than 50 micrometers (μm), no greater than 30 μm, or no greater than 20 μm. 90 The inorganic particles useful in the present invention, especially the inorganic particles with a small pore volume, may have a D of not more than 20 μm, not more than 15 μm, or not more than 10 μm. 50The inorganic particles useful in the present invention, especially the inorganic particles with a small pore volume, may have a D of not more than 8 μm or not more than 3 μm. 10 .

[0061] The particle filter according to the present invention may include a particle loading of 0.005 g / in 3 Up to 0.83g / in 3 (i.e. about 0.3g / L to 50g / L), 0.01g / in 3 Up to 0.33g / in 3 (i.e. about 0.6 g / L to 20 g / L) or 0.015 g / in 3 Up to 0.1g / in 3 (ie, about 0.9 g / L to 6 g / L) of inorganic particle layer.

[0062] The inorganic particle layer may be applied to the surface of the porous wall of the substrate by any known process such as a dry coating process and a wash coating process.

[0063] Dry coating processes are well known and are generally carried out by blowing inorganic particles in granular form or suitable precursors thereof from an open end into the channels of the substrate by a carrier gas stream, and optionally drying and optionally calcining the coated substrate. By this process, no liquid carrier is used. The inorganic particles are usually distributed on the surface of the porous wall of the channel in the form of a particle bed.

[0064] In some embodiments, inorganic particles or suitable precursors thereof can be blown into the inlet channel from the open end of the channel toward the closed end of the channel. The particle bed formed in the inlet channel can be located on the porous wall of the inlet channel and is also opposite to the plunger blocking the channel. The particle bed, i.e., the inorganic particle layer, is breathable, which may help to capture particulate matter (PM) in the exhaust gas stream and allow gaseous pollutants in the exhaust gas stream to penetrate through.

[0065] The layer of inorganic particles in the form of a particle bed may extend along the porous wall of the channel supporting the inorganic particles. It will be appreciated that the particle bed may extend along the entire length of the porous wall of the channel, or only along a portion of the length of the porous wall of the channel.

[0066] Washcoating processes are also well known and are generally carried out by applying a slurry in a liquid solvent (e.g., water) containing inorganic particles or a suitable precursor thereof and an optional auxiliary agent into the channel of the substrate from the open end, drying and optionally calcining the coated substrate. The inorganic particle layer applied by washcoating can be in the form of a porous coating that can extend along the porous walls of the channel that loads the inorganic particles. In addition, the porous coating can extend along the entire length of the porous wall of the channel, or only extend along a portion of the length of the porous wall of the channel.

[0067] The particle filter according to the present invention may also include a TWC coating in at least a portion of the inlet channel and / or outlet channel of the substrate. In particular, the TWC coating is present in both the inlet channel and the outlet channel of the substrate.

[0068] The TWC coating is typically in the form of a washcoat, also known as an "in-wall" coating, comprising the TWC composition.

[0069] It is to be understood that the TWC coating is intended to be supported in the pores of the porous walls of the channels, while appreciable amounts of the TWC composition may also be found on the surfaces of the porous walls in the coated channels.

[0070] There is no particular limitation on the TWC composition that can be used for the TWC coating included in the particulate filter. Generally, the TWC composition contains a platinum group metal component as a catalytically active substance, such as a rhodium component and one or both of a platinum component and a palladium component supported on carrier particles. Available materials used as a carrier may be refractory metal oxides, oxygen storage components, and any combination thereof.

[0071] Examples of refractory metal oxides may include, but are not limited to, alumina, lanthanum oxide doped alumina, barium oxide doped alumina, ceria doped alumina, zirconia doped alumina, ceria-zirconia doped alumina, lanthanum oxide-zirconia doped alumina, barium oxide-lanthanum oxide doped alumina, barium oxide-ceria doped alumina, barium oxide-zirconia doped alumina, barium oxide-lanthanum oxide-neodymia doped alumina, lanthanum oxide-ceria doped alumina, and any combination thereof.

[0072] Examples of oxygen storage components (OSC) may include, but are not limited to, reducible rare earth metal oxides such as ceria. The oxygen storage component may also include one or more of lanthanum oxide, praseodymium oxide, neodymium oxide, europium oxide, samarium oxide, ytterbium oxide, yttrium oxide, zirconium oxide, and hafnium oxide to form a composite oxide with ceria. In particular, the oxygen storage component is selected from ceria-zirconia composite oxides and stable ceria-zirconia composite oxides.

[0073] The particle filter according to the present invention may include a particle loading of 0.1 g / in 3 Up to 5.0g / in 3 (i.e. about 6.1 g / L to 305.1 g / L) or 0.5 g / in 3 Up to 3.0g / in 3 (i.e. about 30.5 g / L to 183.1 g / L) or 0.8 g / in 3 Up to 2g / in 3 (ie, about 49 g / L to 122 g / L) of TWC coating.

[0074] TWC coatings can contain a total loading of 1.0 g / ft 3 Up to 50.0g / ft 3 (i.e. about 0.04 g / L to 1.8 g / L) or 5.0 g / ft 3 Up to 20.0g / ft 3 (i.e., about 0.18 g / L to 0.71 g / L) of PGM components, calculated as the corresponding PGM elements.

[0075] The TWC coating can be applied to the substrate by any known process, typically by a washcoating process. The washcoating process is generally performed by coating a slurry of TWC catalyst particles containing the supported PGM component and optional promoters in a solvent (e.g., water), drying and calcining the coated substrate.

[0076] When present, the TWC coating will be applied to the substrate prior to supporting the inorganic particle layer as described above. When present, the TWC coating may also be referred to as an undercoating, ie, located below the inorganic particle layer.

[0077] In some exemplary embodiments, the particle filter according to the present invention comprises:

[0078] - a substrate comprising a plurality of longitudinally extending porous walls to form a plurality of parallel channels extending from an inlet end to an outlet end, wherein a certain number of the channels are inlet channels open at the inlet end and closed at the outlet end, and a certain number of the channels are outlet channels closed at the inlet end and open at the outlet end; and

[0079] - a layer of inorganic particles supported on the surface of the porous wall in at least the inlet channel, and

[0080] - an optional TWC coating, preferably a washcoat comprising a TWC composition,

[0081] The inorganic particle layer comprises particles not larger than 0.5 cm 3 Inorganic particles with small BET pore volume of 1.1447 W / g.

[0082] In a further exemplary embodiment, the particle filter according to the present invention comprises:

[0083] - a substrate comprising a plurality of longitudinally extending porous walls to form a plurality of parallel channels extending from an inlet end to an outlet end, wherein a certain number of the channels are inlet channels open at the inlet end and closed at the outlet end, and a certain number of the channels are outlet channels closed at the inlet end and open at the outlet end; and

[0084] - a layer of inorganic particles supported on the surface of the porous wall in at least the inlet channel, and

[0085] - an optional washcoat layer comprising a TWC composition,

[0086] The inorganic particle layer comprises particles not larger than 0.5 cm 3 / g of inorganic particles with a small BET pore volume, and the amount of inorganic particles with a small BET pore volume is 75 volume % or more, 85 volume % or more, 90 volume % or more, or even 95 volume % or more based on the total volume of all inorganic particles in the inorganic particle layer.

[0087] In some other exemplary embodiments, the particle filter according to the present invention comprises:

[0088] - a substrate comprising a plurality of longitudinally extending porous walls to form a plurality of parallel channels extending from an inlet end to an outlet end, wherein a certain number of the channels are inlet channels open at the inlet end and closed at the outlet end, and a certain number of the channels are outlet channels closed at the inlet end and open at the outlet end; and

[0089] - a layer of inorganic particles supported on the surface of the porous wall in at least the inlet channel, and

[0090] - an optional washcoat layer comprising a TWC composition,

[0091] The inorganic particle layer is mainly or substantially composed of particles having a particle size not larger than 0.5 cm 3 / g is composed of inorganic particles of non-PGM inorganic materials with small BET pore volume.

[0092] In some further exemplary embodiments, the particle filter according to the present invention comprises:

[0093] - a substrate comprising a plurality of longitudinally extending porous walls to form a plurality of parallel channels extending from an inlet end to an outlet end, wherein a certain number of the channels are inlet channels open at the inlet end and closed at the outlet end, and a certain number of the channels are outlet channels closed at the inlet end and open at the outlet end; and

[0094] - a layer of inorganic particles supported on the surface of the porous wall in at least the inlet channel, and

[0095] - an optional washcoat layer comprising a TWC composition,

[0096] The inorganic particle layer is mainly or substantially composed of small BET pores with a volume of no more than 0.5 cm 3 / g and a BET surface area of ​​at least 60 m2 / g of inorganic particles.

[0097] In some specific embodiments, the particle filter according to the present invention comprises:

[0098] - a substrate comprising a plurality of longitudinally extending porous walls to form a plurality of parallel channels extending from an inlet end to an outlet end, wherein a certain number of the channels are inlet channels open at the inlet end and closed at the outlet end, and a certain number of the channels are outlet channels closed at the inlet end and open at the outlet end; and

[0099] - a layer of inorganic particles supported on the surface of the porous wall in at least the inlet channel, and

[0100] - an optional washcoat layer comprising a TWC composition,

[0101] The inorganic particle layer is mainly or substantially composed of small BET pores with a volume of no more than 0.5 cm 3 / g and a BET surface area of ​​at least 60 m 2 / g of inorganic particles of non-PGM inorganic material, and the non-PGM inorganic material is selected from alumina, hydrated alumina, boehmite, silica, zinc oxide, zirconium oxide or a combination or composite thereof.

[0102] In some preferred specific embodiments, the particle filter according to the present invention comprises:

[0103] - a substrate comprising a plurality of longitudinally extending porous walls to form a plurality of parallel channels extending from an inlet end to an outlet end, wherein a certain number of the channels are inlet channels open at the inlet end and closed at the outlet end, and a certain number of the channels are outlet channels closed at the inlet end and open at the outlet end; and

[0104] - a layer of inorganic particles supported on the surface of the porous wall in at least the inlet channel, and

[0105] - an optional washcoat layer comprising a TWC composition,

[0106] The inorganic particle layer is mainly or substantially composed of small BET pores with a volume of no more than 0.3 cm 3 / g and a BET surface area of ​​at least 80 m 2 / g of inorganic particles of non-PGM inorganic material, and the non-PGM inorganic material is selected from alumina, hydrated alumina, boehmite, silica, zinc oxide, zirconium oxide or a combination or composite thereof.

[0107] In some other preferred specific embodiments, the particle filter according to the present invention comprises:

[0108] - a substrate comprising a plurality of longitudinally extending porous walls to form a plurality of parallel channels extending from an inlet end to an outlet end, wherein a certain number of the channels are inlet channels open at the inlet end and closed at the outlet end, and a certain number of the channels are outlet channels closed at the inlet end and open at the outlet end; and

[0109] - a layer of inorganic particles supported on the surface of the porous wall in at least the inlet channel, and

[0110] - an optional washcoat layer comprising a TWC composition,

[0111] The inorganic particle layer is mainly or substantially composed of small BET pores with a volume of no more than 0.2 cm 3 / g and a BET surface area of ​​at least 90 m 2 / g of inorganic particles of non-PGM inorganic material, and the non-PGM inorganic material is selected from alumina, hydrated alumina, boehmite, silica, zinc oxide, zirconium oxide or a combination or composite thereof.

[0112] In each of the exemplary and specific embodiments described above, it is preferred that the inorganic particles consist essentially of inorganic particles having at least one, preferably all, of the following particle size characteristics:

[0113] -D not more than 30μm 90 ,

[0114] -D not more than 15μm 50 ,as well as

[0115] -D not more than 8μm 10 .

[0116] More preferably, the inorganic particles consist essentially of inorganic particles having at least one, preferably all, of the following particle size characteristics:

[0117] -D not more than 20μm 90 ,

[0118] -D not more than 10μm 50 ,as well as

[0119] -D not more than 3μm 10 .

[0120] In the above-mentioned exemplary and specific embodiments, it is preferred that the inorganic particle layer does not contain a PGM component.

[0121] In those exemplary and specific embodiments described above, it is preferred that the particulate filter includes a washcoat layer comprising a TWC composition.

[0122] The particulate filter may be housed within a housing having an inlet and an outlet for exhaust flow, which housing may be operatively associated with and in fluid communication with the rest of the engine's exhaust system.

[0123] According to a second aspect of the present invention, there is provided a method for producing a particle filter, the method comprising:

[0124] - providing a substrate comprising a plurality of longitudinally extending porous walls to form a plurality of parallel channels extending from an inlet end to an outlet end, wherein a certain number of the channels are inlet channels that are open at the inlet end and closed at the outlet end, and a certain number of the channels are outlet channels that are closed at the inlet end and open at the outlet end,

[0125] - applying inorganic particles or precursors thereof to the surface of the porous walls in the inlet channel and / or the outlet channel, and

[0126] - optionally, drying and / or calcining,

[0127] The deposit contains no more than 0.5cm 3 The inorganic particle layer comprises inorganic particles with a small BET pore volume of / g.

[0128] The inorganic particles or their precursors may be applied on the surface of the porous wall by a dry coating or wash coating process (preferably a dry coating process) as described above in the first aspect.

[0129] In some embodiments, the method for producing a particle filter further comprises applying a TWC coating in the porous walls in at least a portion of the inlet channel and / or outlet channel of the substrate before applying the inorganic particles to the surface of the porous walls. The TWC coating can be applied by a washcoating process as described above.

[0130] Any general description and described preferred requirements of the inorganic particle layer and the TWC coating in the first aspect above may be applied herein by reference.

[0131] In some embodiments, greater than 50% by volume of the inorganic particles applied, such as 75% by volume or more, 85% by volume or more, 90% by volume or more, or even 95% by volume or more, are particles having a particle size not greater than 0.5 cm as specified herein. 3 Inorganic particles with a small BET pore volume of no more than 0.5 cm 3 / g of inorganic particles with a small BET pore volume.

[0132] According to a third aspect, an exhaust gas treatment system is provided, comprising a particle filter as described in the first aspect or a particle filter obtainable or obtained by the method as described in the second aspect, the particle filter being located downstream of a gasoline engine.

[0133] According to a fourth aspect, there is provided a method for treating an exhaust gas flow from a gasoline engine, the method comprising contacting the exhaust gas flow with a particle filter as described in the first aspect, a particle filter obtainable or obtained from the method as described in the second aspect, or an exhaust gas treatment system as described in the third aspect.

[0134] Implementation

[0135] Various embodiments are listed below. It should be understood that the embodiments listed below can be combined with all aspects of the scope of the present invention and other embodiments.

[0136] Embodiment 1. A particle filter, comprising:

[0137] - a substrate comprising a plurality of longitudinally extending porous walls to form a plurality of parallel channels extending from an inlet end to an outlet end, wherein a certain number of the channels are inlet channels open at the inlet end and closed at the outlet end, and a certain number of the channels are outlet channels closed at the inlet end and open at the outlet end; and

[0138] - a layer of inorganic particles supported in the inlet channel and / or outlet channel, preferably on the surface of the porous wall in at least the inlet channel,

[0139] The inorganic particle layer comprises particles having a diameter not greater than 0.5 cm 3 Inorganic particles with small BET pore volume of 1.1447 W / g.

[0140] Embodiment 2. A particulate filter according to Embodiment 1, wherein the inorganic particle layer contains 50 volume % or more, 75 volume % or more, 85 volume % or more, 90 volume % or more, or even 95 volume % or more of the inorganic particles having a small BET pore volume.

[0141] Embodiment 3. The particulate filter according to Embodiment 2, wherein the inorganic particle layer consists essentially of the inorganic particles having a small BET pore volume.

[0142] Embodiment 4. The particulate filter according to any one of the preceding embodiments, wherein the inorganic particle layer exhibits no three-way conversion catalytic activity.

[0143] Embodiment 5. The particulate filter according to any of the preceding embodiments, wherein the inorganic particle layer does not contain a PGM component.

[0144] Embodiment 6. A particulate filter according to any of the preceding embodiments, wherein the inorganic particles, in particular the inorganic particles having a small BET pore volume, are non-PGM inorganic materials, in particular particles selected from alumina, hydrated alumina, boehmite, zirconium oxide, cerium dioxide, silicon dioxide, titanium dioxide, magnesium oxide, zinc oxide, zinc carbonate, calcium oxide, calcium carbonate, silicate zeolites, aluminosilicate zeolites or combinations or composites thereof.

[0145] Embodiment 7. A particulate filter according to Embodiment 6, wherein the non-PGM inorganic material is selected from alumina, hydrated alumina, boehmite, silica, zinc oxide, zirconium oxide, or a combination or composite thereof.

[0146] Embodiment 8. A particle filter according to any one of the preceding embodiments, wherein the small BET pore volume is no greater than 0.3 cm 3 / g or not more than 0.2cm 3 / g.

[0147] Embodiment 9. A particle filter according to any one of the preceding embodiments, wherein the inorganic particles having a small BET pore volume have a pore size of at least 60 m 2 / g, at least 80m 2 / g or at least 90m 2 / g of BET surface area.

[0148] Embodiment 10. A particle filter according to any one of the preceding embodiments, wherein the inorganic particles, in particular the inorganic particles having a small BET pore volume, have a D of no greater than 50 μm, no greater than 30 μm, or no greater than 20 μm. 90 .

[0149] Embodiment 11. The particulate filter according to any of the preceding embodiments, further comprising a three-way conversion catalyst (TWC) coating, preferably a washcoat layer comprising a TWC composition.

[0150] Embodiment 12. The particulate filter according to Embodiment 11, wherein the three-way conversion catalyst coating is located in at least a portion of the inlet channel and / or outlet channel of the substrate.

[0151] Embodiment 13. The particulate filter according to any one of the preceding embodiments, comprising the inorganic particle layer having a loading amount of 0.3 g / L to 50 g / L, 0.6 g / L to 20 g / L, or 0.9 g / L to 6 g / L.

[0152] Embodiment 15. The particulate filter according to any of the preceding embodiments, wherein the particulate filter is a gasoline particulate filter.

[0153] Embodiment 15. A method for producing a particle filter according to any one of embodiments 1 to 14, the method comprising:

[0154] - providing a substrate comprising a plurality of longitudinally extending porous walls to form a plurality of parallel channels extending from an inlet end to an outlet end, wherein a certain number of the channels are inlet channels that are open at the inlet end and closed at the outlet end, and a certain number of the channels are outlet channels that are closed at the inlet end and open at the outlet end,

[0155] - applying inorganic particles or precursors thereof to the surface of the porous walls in the inlet channel and / or outlet channel, and

[0156] - optionally, drying and / or calcining,

[0157] To deposit an inorganic particle layer including the inorganic particles having a small BET pore volume.

[0158] Embodiment 16. The method according to embodiment 15, wherein the inorganic particles are applied by a dry coating or wash coating process, preferably by a dry coating process.

[0159] Embodiment 17. An exhaust gas treatment system comprising a particulate filter according to any one of Embodiments 1 to 14 or a particulate filter obtainable or obtained from a method according to any one of Embodiments 15 to 16, and located downstream of a gasoline engine.

[0160] Embodiment 18. A method for treating an exhaust gas stream from a gasoline engine, the method comprising contacting the exhaust gas stream with a particulate filter according to any one of Embodiments 1 to 14, a particulate filter obtainable or obtained from a method according to any one of Embodiments 15 to 16, or an exhaust treatment system according to Embodiment 17.

[0161] Example

[0162] Various aspects of the present invention are more fully illustrated by the following examples, which are set forth for the purpose of illustrating certain aspects of the present invention and should not be construed as limiting the present invention.

[0163] I. Preparation of particle filters

[0164] Materials and characterization

[0165] The materials used to prepare the inorganic particle layer of the particle filter in the examples are summarized in the following Table 1. The particle size was measured by Sympatec HELOS laser diffraction particle size analyzer. The surface area and pore volume were measured by Micromeritics ASAP2420 surface area and porosity analyzer using the BET model at 77K under nitrogen adsorption.

[0166] Table 1

[0167]

[0168] Reference Example 1 (R1)

[0169] A gasoline particulate filter cordierite substrate S1 was used as a reference filter (blank filter), which had a size of 132.1 mm (D) × 127 mm (L) and a volume of 1.74 L (about 106.1 in 3 ), a pore density of 300 cells per square inch (cpsi), a wall thickness of 8 mils, and a porosity of 65% as determined by mercury intrusion measurement.

[0170] Reference Example 2 (R2)

[0171] A particulate filter with a TWC coating was prepared from the same filter substrate as the blank filter of Reference Example 1 (substrate S1) by applying the TWC washcoat layer to both the inlet and outlet channels of the blank filter.

[0172] In a planetary mixer (P-mixer), 20.08 g of a 9.79 wt % aqueous solution of rhodium nitrate was impregnated onto 257 g of high surface area gamma alumina powder to form a wet powder while achieving initial wetness. In a planetary mixer (P-mixer), 12.05 g of a 16.31 wt % aqueous solution of diethanolamine hexahydroxyplatinate was impregnated onto 698 g of a ceria / zirconia (40% ceria) composite powder to form a wet powder while achieving initial wetness. An aqueous slurry was formed by mixing the above two wet powders with 894 g of deionized water, to which 78 g of barium nitrate and 67 g of a 21.0 wt % aqueous solution of zirconium nitrate were added. The pH of the slurry was adjusted to 3.6 with nitric acid. The slurry was ground to a particle size D 90 The washcoat layer was 4.5 μm and then coated into the inlet channel of the blank filter at 50% of the washcoat layer loading, and coated into the outlet channel of the blank filter at the remaining 50% of the washcoat layer loading. The coated substrate was then dried at 150° C. for 1 hour and then calcined at 550° C. for 1 hour.

[0173] The obtained inlet TWC coating has a thermal conductivity of 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, with a Pt / Rh ratio of 5 / 5.

[0174] The TWC coating prepared by the same process is referred to herein as TWC-1.

[0175] Reference Example 3 (R3)

[0176] A gasoline particulate filter cordierite substrate S2 was used as a reference filter (blank filter) with a size of 118.4 mm (D) × 127 mm (L) and a volume of 1.4 L (about 85.4 in 3 ), a pore density of 300 cells per square inch (cpsi), a wall thickness of 8 mils, and a porosity of 65% as determined by mercury intrusion measurement.

[0177] Reference Example 4 (R4)

[0178] A particulate filter with a TWC coating was prepared from the same filter substrate as the blank filter of Reference Example 2 (substrate S2) by applying the TWC washcoat layer to both the inlet and outlet channels of the blank filter.

[0179] In a planetary mixer (P-mixer), 24.21 g of a 9.68 wt% aqueous solution of rhodium nitrate was impregnated onto 255 g of high surface area gamma alumina powder to form a wet powder while achieving initial wetness. In a planetary mixer (P-mixer), 14.37 g of a 16.31 wt% aqueous solution of diethanolamine hexahydroxyplatinate was impregnated onto 712 g of a ceria / zirconia (40% ceria) composite powder to form a wet powder while achieving initial wetness. An aqueous slurry was formed by mixing the above two wet powders with 1124 g of deionized water, to which 78 g of barium nitrate and 68 g of a 21.3 wt% aqueous solution of zirconium nitrate were added. The pH of the slurry was adjusted to 3.6 with nitric acid. The slurry was ground to a particle size D 90 The washcoat layer was 4.5 μm and then coated into the inlet channel of the blank filter at 50% of the washcoat layer loading, and coated into the outlet channel of the blank filter at the remaining 50% of the washcoat layer loading. The coated substrate was then dried at 150° C. for 1 hour and then calcined at 550° C. for 1 hour.

[0180] The obtained inlet TWC coating has a viscosity of about 1.23 g / in 3 (75 g / L) washcoat loading and about 10.0 g / ft 3 (0.35 g / L) total PGM loading, with a Pt / Rh ratio of 5 / 5.

[0181] The TWC coating prepared by the same process is referred to herein as TWC-2.

[0182] Comparative Example 1 (C1)

[0183] A particulate filter having a TWC coating and an alumina particle layer was prepared.

[0184] A particle filter with a TWC coating (TWC-1) was first prepared by applying the same process as described in Reference Example 2 on a blank filter (substrate S1) identical to that described in Reference Example 1. Then, alumina A powder was mixed with a carrier gas and heated at 600 m / s at room temperature. 3 / h flow rate into the inlet channel of the filter. After coating, the filter with the inorganic particle layer in the inlet channel was calcined at a temperature of 550°C for 1 hour. The loading amount of aluminum oxide A powder was 1 g / L (0.016 g / in 3 ).

[0185] Comparative Example 2 (C2)

[0186] A particulate filter having a TWC coating and an alumina particle layer was prepared.

[0187] The preparation of the particle filter was the same as that of Comparative Example 1, except that the loading amount of aluminum oxide A powder was 3 g / L (0.05 g / in 3 ).

[0188] Comparative Example 3 (C3)

[0189] A particulate filter having a TWC coating and an alumina particle layer was prepared.

[0190] The preparation of the particle filter was the same as that of Comparative Example 1, except that the loading amount of aluminum oxide A powder was 5 g / L (0.082 g / in 3 ).

[0191] Comparative Example 4 (C4)

[0192] A particulate filter having a TWC coating and an alumina particle layer was prepared.

[0193] The preparation of the particle filter was the same as that of Comparative Example 1, except that the loading amount of aluminum oxide A powder was 7 g / L (0.115 g / in 3 ).

[0194] Comparative Example 5 (C5)

[0195] A particulate filter having a TWC coating and an alumina particle layer was prepared.

[0196] A particle filter with a TWC coating (TWC-2) was first prepared by applying the same process as described in Reference Example 4 on a blank filter (substrate S2) identical to that described in Reference Example 3. Then, alumina A powder was mixed with a carrier gas and heated at 600 m / s at room temperature. 3 / h flow rate was blown into the inlet channel of the filter. After coating, the filter with the inorganic particle layer in the inlet channel was calcined at a temperature of 550°C for 1 hour. The loading amount of aluminum oxide A powder was 4 g / L (0.05 g / in 3 ).

[0197] Embodiment 1 (E1) of the present invention

[0198] A particulate filter having a TWC coating and an alumina particle layer was prepared.

[0199] A particle filter with a TWC coating (TWC-1) was first prepared by applying the same process as described in Reference Example 2 on a blank filter (substrate S1) identical to that described in Reference Example 1. Then, alumina B powder was mixed with a carrier gas and heated at room temperature at 600 m / s. 3 / h flow rate into the inlet channel of the filter. After coating, the filter with the inorganic particle layer in the inlet channel was calcined at a temperature of 550°C for 1 hour. The loading amount of aluminum oxide B powder was 1 g / L (0.016 g / in 3 ).

[0200] Embodiment 2 of the present invention (E2)

[0201] A particulate filter having a TWC coating and an alumina particle layer was prepared.

[0202] The preparation of the particle filter was the same as in Example 1 of the present invention, except that the loading amount of the inorganic particles was 2 g / L (0.033 g / in 3 ).

[0203] Embodiment 3 of the present invention (E3)

[0204] A particulate filter having a TWC coating and an alumina particle layer was prepared.

[0205] The preparation of the particle filter was the same as in Example 1 of the present invention, except that the loading amount of the inorganic particles was 3 g / L (0.05 g / in 3 ).

[0206] Embodiment 4 of the present invention (E4)

[0207] A particulate filter having a TWC coating and an alumina particle layer was prepared.

[0208] The preparation of the particle filter was the same as in Example 1 of the present invention, except that the loading amount of the inorganic particles was 4 g / L (0.05 g / in 3 ).

[0209] Embodiment 5 of the present invention (E5)

[0210] A particulate filter having a TWC coating and an alumina particle layer was prepared.

[0211] A particle filter with a TWC coating (TWC-1) was first prepared by applying the same process as described in Reference Example 2 on a blank filter (substrate S1) identical to that described in Reference Example 1. Then, alumina C powder was mixed with a carrier gas and heated at room temperature at 600 m / s. 3 / h flow rate into the inlet channel of the filter. After coating, the filter with the inorganic particle layer in the inlet channel was calcined at a temperature of 550°C for 1 hour. The loading amount of alumina C powder was 1 g / L (0.016 g / in 3 ).

[0212] Embodiment 6 of the present invention (E6)

[0213] A particulate filter having a TWC coating and an alumina particle layer was prepared.

[0214] The preparation of the particle filter was the same as in Example 5 of the present invention, except that the loading amount of the aluminum oxide C powder was 2 g / L (0.033 g / in 3 ).

[0215] Embodiment 7 of the present invention (E7)

[0216] A particulate filter having a TWC coating and an alumina particle layer was prepared.

[0217] The preparation of the particle filter was the same as in Example 5 of the present invention, except that the loading amount of the aluminum oxide C powder was 3 g / L (0.05 g / in 3 ).

[0218] Embodiment 8 of the present invention (E8)

[0219] A particulate filter having a TWC coating and an alumina particle layer was prepared.

[0220] The preparation of the particle filter was the same as in Example 5 of the present invention, except that the loading amount of the aluminum oxide C powder was 5 g / L (0.082 g / in 3 ).

[0221] Embodiment 9 of the present invention (E9)

[0222] A particulate filter having a TWC coating and an alumina particle layer was prepared.

[0223] A particle filter with a TWC coating (TWC-2) was first prepared by applying the same process as described in Reference Example 4 on a blank filter (substrate S2) identical to that described in Reference Example 3. Then, alumina B powder was mixed with a carrier gas and heated at room temperature at 600 m / s. 3 / h flow rate was blown into the inlet channel of the filter. After coating, the filter with the inorganic particle layer in the inlet channel was calcined at a temperature of 550°C for 1 hour. The loading amount of the aluminum oxide B powder was 3 g / L (0.05 g / in 3 ).

[0224] Embodiment 10 of the present invention (E10)

[0225] A particulate filter having a TWC coating and an inorganic particle layer was prepared.

[0226] The preparation of the particle filter was the same as in Example 9 of the present invention, except that aluminum oxide C powder was used instead of aluminum oxide B powder.

[0227] II. Filtration performance

[0228] II.1 Backpressure

[0229] Through SuperFlow SF-1020Flowbench at 600m 3 The back pressure (BP) of the particle filter in all examples was investigated, measured under a cold air flow of 1.25 W / h.

[0230] II.2 Fresh filtration efficiency

[0231] 1) According to the standard procedure defined in "BS EN ISO 29463-5:2018–Part 5:Test method for filter elements", at a 3 The filtration efficiency of the particle filters in Reference Examples 1 and 2, Comparative Examples 1 to 4, and Inventive Examples 1 to 8 in a fresh state (0 km or out-of-box state) was measured on a fixed air filter performance test bench with a cold air flow of 1.5 200 g / h using aerosol di(2-ethyl-hexyl) sebacate as the particles. The particle number (PN) of particles ranging between 0.10 μm and 0.15 μm was recorded by a PN counter both upstream and downstream of the test filter. The fresh filtration efficiency (FFE) was calculated according to the following equation:

[0232]

[0233] 2) The filtration efficiency of the particle filters in Reference Examples 3 and 4, Comparative Example 5, and Inventive Examples 9 and 10 in a fresh state (0 km or out-of-box state) was measured at a close-coupled position on a CSS2.0L turbo gasoline direct injection engine according to the standard WLTC test procedure defined in "GB18352.6-2016: Limits and measurement methods for emissions from light-duty vehicles". The particle number (PN) of particles larger than 23 nm was recorded by the PN counters at both the inlet and outlet of the tested filter.

[0234] Calculate the fresh filtration efficiency (FFE) according to the following equation:

[0235]

[0236] The test results of each particulate filter in the above examples are summarized in Table 2 below.

[0237] Table 2

[0238]

[0239] From the comparison of Reference Example 1 (R1) with Reference Example 2 (R2) and Reference Example 3 (R3) with Reference Example 4 (R4), it can be seen that the particulate filter with TWC coating has lower fresh filtration efficiency (FFE) and higher back pressure (BP) compared with the blank filter, which may be because the TWC component penetrates into the porous wall of the substrate of the particulate filter.

[0240] By applying a layer of alumina particles as shown in Comparative Examples 1 to 4 (C1 to C4), the fresh filter efficiency (FFE) can be improved and the back pressure is also increased. Surprisingly, by applying a layer of alumina particles with a small pore volume as shown in Inventive Examples 1 to 8 (E1 to E8), the fresh filter efficiency can be improved to a greater extent. It is noteworthy that the particle filters of the Inventive Examples using alumina particles with a small pore volume show a significantly higher fresh filter efficiency than the particle filters of Comparative Examples 1 to 4 using alumina particles with a large pore volume.

[0241] The surprising improvement provided by the inorganic particle layer with a small pore volume can also be observed from the comparison of inventive examples 9 and 10 (E9 and E10) with comparative example 5 (C5). It is noteworthy that the particle filters of inventive examples 9 and 10 exhibit significantly higher fresh filtration efficiency than comparative example 5, while the back pressure is the same or even slightly lower.

[0242] Although the present invention has been described herein with reference to specific embodiments, it should be understood that these embodiments are merely illustrative of the principles and applications of the present invention. It will be apparent to those skilled in the art that various modifications and variations may be made to the methods and apparatus of the present invention without departing from the spirit and scope of the present invention. Therefore, the present invention is intended to include modifications and variations within the scope of the appended claims and their equivalents.

Claims

1. A particle filter, comprising: - a substrate comprising a plurality of longitudinally extending porous walls to form a plurality of parallel channels extending from an inlet end to an outlet end, wherein a certain number of the channels are inlet channels open at the inlet end and closed at the outlet end, and a certain number of the channels are outlet channels closed at the inlet end and open at the outlet end; as well as - a layer of inorganic particles supported in the inlet channel and / or outlet channel, preferably on the surface of the porous wall in at least the inlet channel, The inorganic particle layer comprises particles having a diameter not greater than 0.5 cm 3 Inorganic particles with small BET pore volume of 1.1447 W / g.

2. The particulate filter according to claim 1, wherein the inorganic particle layer contains the inorganic particles having a small BET pore volume in an amount of 50 volume % or more, 75 volume % or more, 85 volume % or more, 90 volume % or more, or even 95 volume % or more. 3 . The particulate filter according to claim 2 , wherein the inorganic particle layer consists essentially of the inorganic particles having a small BET pore volume. 4 . The particulate filter according to claim 1 , wherein the inorganic particle layer exhibits no three-way conversion catalytic activity.

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

6. A particle filter according to any one of the preceding claims, wherein the inorganic particles, in particular the inorganic particles having a small BET pore volume, are non-PGM inorganic materials, in particular particles selected from alumina, hydrated alumina, boehmite, zirconium oxide, cerium dioxide, silicon dioxide, titanium dioxide, magnesium oxide, zinc oxide, zinc carbonate, calcium oxide, calcium carbonate, silicate zeolites, aluminosilicate zeolites 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, zirconium oxide, or a combination or composite thereof.

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

9. A particle filter according to any one of the preceding claims, wherein the inorganic particles having a small BET pore volume have a pore size of at least 60 m 2 / g, at least 80m 2 / g or at least 90m 2 / g of BET surface area.

10. The particle filter according to any one of the preceding claims, wherein the inorganic particles, in particular the inorganic particles having a small BET pore volume, have a D of not more than 50 μm, not more than 30 μm or not more than 20 μm. 90 .

11. A particle filter according to any one of the preceding claims, further comprising a three-way conversion catalyst (TWC) coating, preferably a washcoat comprising a TWC composition. 12 . The particulate filter according to claim 11 , wherein the three-way conversion catalyst coating is located in at least a portion of the inlet channel and / or outlet channel of the substrate.

13. The particle filter according to any one of the preceding claims, comprising a layer of inorganic particles having a loading of 0.3 g / L to 50 g / L, 0.6 g / L to 20 g / L, or 0.9 g / L to 6 g / L.

14. A particle filter according to any one of the preceding claims, which is a gasoline particle filter.

15. A method for producing a particle filter according to any one of claims 1 to 14, the method comprising: - providing a substrate comprising a plurality of longitudinally extending porous walls to form a plurality of parallel channels extending from an inlet end to an outlet end, wherein a certain number of the channels are inlet channels open at the inlet end and closed at the outlet end, and a certain number of the channels are outlet channels closed at the inlet end and open at the outlet end, - applying inorganic particles or precursors thereof to the surface of the porous walls in the inlet channel and / or outlet channel, and - optionally, drying and / or calcining, To deposit an inorganic particle layer including the 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 or wash coating process, preferably by a dry coating process.

17. An exhaust gas treatment system comprising a particle filter according to any one of claims 1 to 14 or a particle filter obtainable or obtained from a method according to any one of claims 15 to 16 and located downstream of a gasoline engine.

18. A method for treating an exhaust gas flow from a gasoline engine, the method comprising contacting the exhaust gas flow with a particle filter according to any one of claims 1 to 14, a particle filter obtainable or obtained from a method according to any one of claims 15 to 16, or an exhaust gas treatment system according to claim 17.

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