Particle filter

Abstract

The present invention relates to a particle filter, in particular to a particle filter for an internal combustion engine exhaust treatment system, which provides an advantageous combination of low back pressure and high fresh filtration efficiency.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to the entire contents of International Application No. PCT / CN2019 / 117575 filed on November 12, 2019.

[0003] describe Technical Field

[0004] The present invention relates to a particle filter, in particular to a particle filter for an emission treatment system of an internal combustion engine, which provides an advantageous combination of low back pressure and high fresh filtration efficiency.

[0005] background

[0006] The largest fraction of the exhaust gas from most internal combustion engines contains relatively harmless nitrogen (N2), water vapor (H2O) and carbon dioxide (CO2); but the exhaust gas also contains relatively small fractions of harmful and / or toxic substances, such as carbon monoxide (CO) from incomplete combustion, hydrocarbons (HC) from unburned fuel, nitrogen oxides (NOx) from excessive combustion temperatures, and particulate matter (PM).

[0007] Certain internal combustion engines, such as lean burn engines, diesel engines, natural gas engines, power plants, incinerators, or gasoline engines, tend to produce exhaust gas with significant amounts of soot and other particulate matter. Particulate matter emissions can be remedied by passing the PM-containing exhaust gas through a particulate filter.

[0008] Diesel particulate filters have proven to be very effective in removing soot from diesel engine exhaust. The most widely used diesel particulate filter is a wall-flow filter, which filters diesel exhaust by capturing soot on the porous walls of the filter body. Wall-flow filters are designed to provide almost complete filtration of soot without significantly obstructing exhaust gas flow.

[0009] As the soot layer accumulates on the surface of the filter inlet side, the lower permeability of the soot layer causes the filter pressure to drop and the filter back pressure relative to the engine gradually increases, causing the engine to work harder, thereby affecting the engine operating efficiency. Eventually, the pressure drop becomes unacceptable and filter regeneration becomes necessary.

[0010] Particulate emissions from gasoline engines are being regulated by legislation, including the Euro 6 (2014) standard. Certain gasoline direct injection (GDI) engines have been developed with operating procedures that result in the formation of fine particles. Aftertreatment systems for gasoline engines are required to meet particulate matter standards. Particles produced by gasoline engines such as GDI engines tend to be finer and less numerous than those produced by diesel lean burn engines. This is due to the different combustion conditions in diesel engines compared to gasoline engines. For example, gasoline engines operate at higher temperatures than diesel engines. The hydrocarbon composition of gasoline engine emissions is also different compared to diesel engines.

[0011] Original Equipment Manufacturers (OEMs), i.e. vehicle manufacturers, require gasoline particulate filters (GPFs) to have high fresh filtration efficiency and low back pressure. However, due to the low mass of engine-exhaust particulate matter and the high exhaust temperature of gasoline engines, the soot cake generated during the pre-conditioning of the aftertreatment system before testing can usually be ignored. This soot cake is at least partly responsible for the high filtration efficiency of the diesel particulate filter, and for diesel engines, an effective soot cake can be formed within 10-20 km of driving. Since this effect is generally not achievable for gasoline engines, the target fresh filtration efficiency is achieved by using a higher carrier coating loading and this increases the pressure drop on the component. This consideration only applies to fresh components to meet the requirements of the OEM's end-of-line test.

[0012] WO2012030533 A1 relates to a method for forming a porous discriminating layer on a ceramic support having at least one porous wall, the method comprising (a) forming a gas stream containing particle agglomerates through the at least one porous wall from the gas inlet side of the at least one porous wall to the gas outlet side of the at least one porous wall, so that at least a portion of the agglomerates are deposited to form a deposition layer of agglomerates, their constituent particles, or both on the gas inlet side of the at least one porous wall, wherein (1) at least a portion of the particles constituting the particle agglomerates are ceramic materials or precursors of ceramic materials, (2) the particles constituting the particle agglomerates have a size of 0.01-5 micrometers (μm), (3) the agglomerates have a size of 10-200 micrometers, and (4) the deposition layer only partially extends through the thickness of the at least one porous wall, and (b) calcining the deposition layer to form the discriminating layer.

[0013] WO2018115900 A1 relates to a particle filter for an emission treatment system of a gasoline engine, the filter having an inlet side and an outlet side, wherein at least the inlet side is loaded with synthetic ash.

[0014] On December 23, 2016, the Ministry of Environmental Protection of the People's Republic of China (MEP) announced the final legislation of the National VI Limits and Measurement Methods for Light Vehicle Emissions (GB18352.6-2016; hereinafter referred to as National VI), which is much stricter than the National V emission standards. In particular, National VIb incorporates limits on particulate matter (PM) and adopts on-board diagnostic (OBD) requirements. In addition, it is stipulated that vehicles should be tested under the World Harmonized Light Vehicle Test Cycle (WLTC). The WLTC includes many steep accelerations and long high-speed requirements, which require high power output, which may cause long (e.g., >5 seconds) "open-loop" conditions under rich (λ<1) or deep rich (λ<0.8) conditions (because the fuel paddle needs to be pushed all the way down). Although the standards have become more stringent, it is expected to provide a further improved particulate filter that provides a favorable combination of lower back pressure and higher fresh filtration efficiency.

[0015] Overview

[0016] The present invention relates to a particle filter, in particular to a particle filter for an exhaust treatment system of an internal combustion engine.

[0017] Aspects include a particulate filter for exhaust gas treatment of an internal combustion engine, comprising: a particulate filter having an inlet side and an outlet side; and a functional material layer coated on the inlet side, the outlet side, or both sides of the particulate filter.

[0018] Other aspects include a method of treating exhaust gas from an internal combustion engine, the method comprising: providing a particulate filter; and flowing exhaust gas from the engine through the particulate filter. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figures 1(a) and 1(b) show an exemplary wall-flow filter;

[0021] Figures 2(a) and 2(b) show the morphology of high surface area γ-alumina in powder form at different ratios in SEM images;

[0022] FIG3( a ) and FIG3( b ) show the morphology of low surface area boehmite alumina in powder form at different ratios in SEM images;

[0023] Figure 4 shows a graph of back pressure characteristics of a coated particulate filter according to an embodiment of the present invention and a comparative particulate filter;

[0024] Figure 5 shows a graph of filtration efficiency of a coated gasoline particulate filter according to an embodiment of the present invention and a comparative particulate filter;

[0025] Figures 6(a) and 6(b) show the morphology of low surface area magnesium oxide in powder form at different ratios in SEM images;

[0026] Figure 7 shows a graph of back pressure characteristics of a coated particulate filter according to an embodiment of the present invention and a comparative particulate filter;

[0027] Figure 8 A graph of the filtration efficiency of a coated gasoline particulate filter according to an embodiment of the present invention and a comparative particulate filter is shown.

[0028] Details

[0029] Before describing several exemplary embodiments of the invention, it is to be understood that the invention is not limited to the details of construction or process steps set forth in the following description. The invention is capable of other embodiments and of being practiced or carried out in various ways.

[0030] With respect to terms used within this disclosure, the following definitions are provided.

[0031] Throughout the description, including the claims, the terms "comprising one" or "comprising a" should be understood to be synonymous with the term "comprising at least one," unless otherwise indicated, and "between" or "to" should be understood to include limits.

[0032] The terms "a," "an," and "the" are used to refer to one or more than one (ie, to at least one) of the grammatical objects of the present clause.

[0033] The term "and / or" includes the meanings of "and", "or" and all other possible combinations of elements related to this term.

[0034] Unless otherwise indicated, all percentages and ratios are by weight.

[0035] Therefore, according to one aspect of the present invention, there is provided a particulate filter for exhaust gas treatment of an internal combustion engine, comprising:

[0036] (1) A particle filter having an inlet side and an outlet side;

[0037] (2) A functional material layer coated on the inlet side, outlet side, or both sides of the particulate filter.

[0038] In the following paragraphs, different aspects of the invention are defined in more detail. Each aspect so defined may be combined with any other aspect, unless expressly stated to the contrary. In particular, any feature indicated as preferred or advantageous may be combined with any other feature indicated as preferred or advantageous. The particle filter is typically formed from a porous substrate. The porous substrate may include a ceramic material, such as cordierite, silicon carbide, silicon nitride, zirconium oxide, mullite, spodumene, alumina-silicon dioxide-magnesium oxide, zirconium silicate and / or aluminum titanate, typically cordierite or silicon carbide. The porous substrate may be a porous substrate of the type typically used in emission treatment systems for internal combustion engines.

[0039] The internal combustion engine may be a lean burn engine, a diesel engine, a natural gas engine, a power plant, an incinerator or a gasoline engine.

[0040] The porous substrate may exhibit a conventional honeycomb structure. The filter may take the form of a conventional "through-flow filter". Alternatively, the filter may take the form of a conventional "wall flow filter" (WFF). Such filters are known in the art.

[0041] The particle filter is preferably a wall flow filter. Referring to Figures 1(a) and 1(b), an exemplary wall flow filter is provided. A wall flow filter works by forcing a flow of exhaust gas (13) (including particulate matter) through a wall formed of a porous material.

[0042] A wall-flow filter typically has a first face and a second face defining a longitudinal direction therebetween. In use, one of the first face and the second face will be the inlet face of the exhaust gas (13) and the other will be the outlet face of the treated exhaust gas (14). A conventional wall-flow filter has a first and a second plurality of channels extending along the longitudinal direction. The first plurality of channels (11) are open at the inlet face (01) and closed at the outlet face (02). The second plurality of channels (12) are open at the outlet face (02) and closed at the inlet face (01). The channels are preferably parallel to each other to provide a constant wall thickness between the channels. Therefore, a gas entering one of the plurality of channels from the inlet face cannot leave the monolith without diffusing to the other plurality of channels from the inlet side (21) to the outlet face (22) through the channel wall (15). The channels are closed by introducing a sealant material into the open end of the channel. Preferably, the number of channels of the first plurality of channels is equal to the number of channels of the second plurality of channels, and each group of channels is evenly distributed throughout the monolith. Preferably, the wall flow filter has 100-500 channels per square inch, preferably 200-400 channels, in a plane orthogonal to the longitudinal direction. For example, on the inlet face (01), the density of open and closed channels is 200-400 channels per square inch. The cross-section of the channel may be rectangular, square, circular, elliptical, triangular, hexagonal or other polygonal shapes.

[0043] In one or more embodiments, the inlet side (21) of the porous wall of the particle filter is coated with a layer of functional material. The layer of functional material can be coated on the outlet side (22) of the porous wall of the filter, or on both sides (21 and 22). The loading can be described as "on wall" loading or "in wall" loading. The former is characterized by forming a layer of functional material on the surface of the porous wall (15). The latter is characterized by extending part of the functional material through the thickness of the entire porous wall (15).

[0044] In one or more embodiments, the functional material layer comprises:

[0045] (1) the first inorganic material comprises one or more of alumina, zirconia, cerium oxide, silicon dioxide, titanium dioxide, and rare earth metal oxides other than cerium oxide; and (2) the second inorganic material comprises one or more of alumina, zirconia, cerium oxide, silicon dioxide, titanium dioxide, magnesium oxide, zinc oxide, manganese oxide, silicate zeolite, and aluminosilicate zeolite. In a specific embodiment, the first and second inorganic materials are mixed uniformly, layered, or partitioned.

[0046] In one or more embodiments, the functional material layer further comprises a first platinum group metal (PGM) selected from the group consisting of platinum (Pt), palladium (Pd) and rhodium (Rh) and mixtures thereof. The PGM is present in a catalytically effective amount to convert NOx, CO and hydrocarbons in the exhaust gas into N2, CO2 and H2O, and oxidize particulate matter captured on the particulate filter.

[0047] In one or more embodiments, the functional material layer further comprises at least one organic material, such as acetic acid, oxalic acid, citric acid, tartaric acid, fumaric acid, lactic acid, malic acid, maleic acid, hexanol, octanol, decanol, cellulose, hydroxyethyl cellulose, methyl hydroxyethyl cellulose, starch, polyethylene, polypropylene, polystyrene, polyethylene oxide, polyethylene terephthalate, polybutylene terephthalate, polyvinyl chloride, polyvinyl alcohol, polyvinyl pyrrolidone, polymethyl methacrylate, polyamide, polycarbonate or polyurethane.

[0048] In one or more embodiments, the second inorganic material has a D between 50 and 400 μm, preferably between 100 and 300 μm. 90 .

[0049] In one or more embodiments, the second inorganic material has a D between 10 and 200 μm, preferably between 50 and 150 μm. 50 .

[0050] In one or more embodiments, the second inorganic material has a D between 3 and 40 μm, preferably between 5 and 20 μm. 10 .

[0051] In one or more embodiments, the first inorganic material has a D of 1 to 50 μm, preferably 3.5 to 20 μm. 90 , more preferably D90 is 4 to 10 μm.

[0052] In one or more embodiments, the first inorganic material has a D of 1.2 to 8 μm, preferably 1.8 to 6 μm. 50 .

[0053] In one or more embodiments, the first inorganic material has a D of 0.6 to 2.2 μm, preferably 0.8 to 1.5 μm. 10 .

[0054] “D 90 ”, “D 50 ” and “D 10 "Usually means the points in the cumulative particle size distribution where the cumulative weight from the small particle diameter reaches 90%, 50% and 10%. 90are values ​​determined by measuring particle size distribution. The particle size distribution is measured by using a laser diffraction particle size distribution analyzer.

[0055] In one or more embodiments, the loading amount of the second inorganic material is between 0.05 and 5 g / L, preferably between 0.1 and 2 g / L, and more preferably between 0.15 and 1 g / L.

[0056] In one or more embodiments, the second inorganic material has a 3 The bulk density.

[0057] In one or more embodiments, the weight percentage of the second inorganic material in the functional material layer is between 1 and 25%, preferably between 5 and 20%.

[0058] In one or more embodiments, the functional material can be applied in the form of particles. In a preferred embodiment, the functional material is applied in the form of particles through a gas phase carrier, i.e., "dry coated" without using any liquid carrier. In other embodiments, the functional material can be applied in the form of a liquid suspension.

[0059] After coating, the functional material can take the form of a packed bed. For example, when the particle filter is a wall-flow filter, the functional material can form a packed bed relative to the wall of multiple channels opened at the inlet side. The packed bed can be formed in the channel opened at the inlet side and relative to the sealant material of the closed channel, i.e., toward the outlet end of the inlet channel. The packed bed is usually porous and usually gas permeable, and the size of the hole is to capture particulate matter such as smoke in the exhaust gas of the internal combustion engine. The pores of the packed bed are usually smaller than the pores of the porous substrate of the particle filter. As an alternative, or in addition, the packed bed may have more pores than the wall of the porous substrate (i.e., it can provide a high level of filtration by providing a long path length). The packed bed can extend along the wall of multiple channels opened at the inlet side. The packed bed can take the form of a layer or a membrane, such as a continuous layer or a membrane. The packed bed can extend along the entire length of multiple channel walls, or only along a partial length of the wall. The functional material can be in the form of a porous coating rather than a packed bed, such as a coating applied as (i.e., derived from) a carrier coating slurry. The porous coating may be disposed in a wall flow filter in a manner similar to the packed bed discussed above.

[0060] In one or more embodiments, the particulate filter further includes a porous body comprising a plurality of pores, and further includes a catalytic carrier coating within at least a portion of the plurality of pores. The use of the catalytic carrier coating can be used to treat components of internal combustion engine exhaust, such as unburned hydrocarbons, carbon monoxide and / or nitrogen oxides. The catalytic carrier coating includes one or more of a selective catalytic reduction (SCR) catalyst, a diesel oxidation catalyst (DOC), a three-way conversion (TWC) catalyst, an AMOx catalyst, a NOx trap, a NOx absorber catalyst, and a hydrocarbon trap catalyst. The catalytic carrier coating is generally substantially distributed throughout the plurality of pores. Before applying the functional material layer, the catalytic carrier coating is applied to the particulate filter. The catalytic washcoat may be present on the particle filter as a separate coating, or the catalytic washcoat may be integrally formed with the particle filter, for example, the catalytic washcoat may be impregnated as a solution or slurry into the material of the raw particle filter, or the catalytic washcoat may be combined with the components forming the substrate monolith structure and then extruded into a flow-through monolith, and after drying and calcining, the alternating ends of the channels are arranged in a checkerboard pattern at one end of the substrate monolith and the unsealed channels are alternately closed in a similar arrangement at the other end. This latter arrangement requires that the porosity of the extrudate after drying and calcining is sufficient to function as a wall-flow filter, i.e., the porosity of the substrate monolith is at least 40%, such as at least 45%, such as 50% or at least 55% or up to 75%.

[0061] As used herein, "selective catalytic reduction" and "SCR" refer to a catalytic process in which nitrogen oxides are reduced to dinitrogen (N2) using a nitrogen-containing reductant. The SCR catalyst may include at least one material selected from the foregoing: MOR; USY; ZSM-5; ZSM-20; β-zeolite; CHA; LEV; AEI; AFX; FER; SAPO; ALPO; vanadium; vanadium oxide; titanium dioxide; tungsten oxide; molybdenum oxide; cerium oxide; zirconium oxide; niobium oxide; iron; iron oxide; manganese oxide; copper; molybdenum; tungsten; and mixtures thereof. The support structure for the active component of the SCR catalyst may include any suitable zeolite, zeolite-type or non-zeolite compound. Alternatively, the SCR catalyst may include a metal, a metal oxide or a mixed oxide as an active component. Preferred are transition metal-loaded zeolites (e.g., copper-chabazite, or Cu-CHA, and copper intercalated chabazite, or Cu-LEV, and Fe-β) and zeotypes (e.g., copper-SAPO or Cu-SAPO).

[0062] As used herein, the terms "three-way conversion" and "TWC" refer to a catalytic process that can significantly eliminate HC, CO and NOx from gasoline engine exhaust. Typically, a TWC catalyst mainly comprises a platinum group metal (PGM), an oxygen storage component (OSC) and a refractory metal oxide support.

[0063] As used herein, the terms "platinum group metals" and "PGMs" refer to one or more chemical elements as defined in the Periodic Table of Elements, including platinum, palladium, rhodium, osmium, iridium and ruthenium, and mixtures thereof.

[0064] In some embodiments, the platinum group metal component of the TWC catalyst is selected from platinum, palladium, rhodium, or mixtures thereof. In specific embodiments, the platinum group metal component of the TWC catalyst includes palladium.

[0065] In some embodiments, the TWC catalyst does not include additional platinum group metals (i.e., the TWC includes only one platinum group metal). In other embodiments, the TWC catalyst includes additional platinum group metals. In one or more embodiments, when present, the additional platinum group metal is selected from platinum, rhodium, and mixtures thereof. In specific embodiments, the additional platinum group metal component includes rhodium. In one or more specific embodiments, the TWC catalyst includes a mixture of palladium and rhodium. In other embodiments, the TWC catalyst includes a mixture of platinum, palladium, and rhodium.

[0066] As used herein, the terms "oxygen storage component" and "OSC" refer to entities that have multiple valence states and can actively react with a reducing agent such as CO or hydrogen under reducing conditions, and then react with an oxidizing agent such as oxygen or nitrogen oxides under oxidizing conditions. Examples of oxygen storage components include rare earth oxides, particularly cerium oxide, lanthanum oxide, praseodymium oxide, neodymium oxide, niobium oxide, europium oxide, samarium oxide, ytterbium oxide, yttrium oxide, zirconium oxide, and mixtures thereof other than cerium oxide. The rare earth oxides may be in bulk (e.g., granular) form. The oxygen storage component may include cerium oxide in a form that exhibits oxygen storage properties. The lattice oxygen of cerium oxide can react with carbon monoxide, hydrogen, or hydrocarbons under A / F-rich conditions. In one or more embodiments, the oxygen storage component for the TWC catalyst includes a cerium oxide-zirconia composite or a rare earth stabilized cerium oxide-zirconia.

[0067] As used herein, the terms "refractory metal oxide support" and "support" refer to the underlying high surface area material on which the additional compound or element is loaded. The support particles have pores greater than 20 Å and a wide pore distribution. As defined herein, such supports, such as metal oxide supports, do not include molecular sieves, specifically zeolites. In certain embodiments, high surface area refractory metal oxide supports may be utilized, such as alumina support materials, also known as "gamma-alumina" or "activated alumina," which typically exhibit a surface area in excess of 60 square meters per gram ("m 2 / g”), typically up to about 200 m 2 / g or more. Such activated aluminas are typically mixtures of gamma and delta phases of alumina, but may also contain significant amounts of eta, kappa and theta alumina phases. Refractory metal oxides other than activated alumina may be used as supports for at least some of the catalytic components in a given catalyst. For example, bulk ceria, zirconia, alpha-alumina, silica, titania and other materials are known for such uses.

[0068] In some embodiments, the refractory metal oxide support for the TWC catalyst independently comprises an activated, stabilized, or both compound selected from the group consisting of alumina, zirconia, alumina-zirconia, lanthanum oxide-alumina, lanthanum oxide-zirconia-alumina, alumina-chromia, ceria, alumina-ceria, and combinations thereof.

[0069] As used herein, the terms "diesel oxidation catalyst" and "DOC" refer to diesel oxidation catalysts, which are well known in the art. Diesel oxidation catalysts are designed to oxidize CO to CO2 and gaseous HCs, and to oxidize the organic portion (soluble organic portion) of diesel particles to CO2 and H2O. Typical diesel oxidation catalysts include platinum and optionally palladium on a high surface area inorganic oxide support such as alumina, silica-alumina, titania, silica-titania, and zeolites. The term as used herein includes DECs (diesel exothermic catalysts) that generate exotherm.

[0070] As used herein, "ammonia oxidation catalyst" and "AMOx" refer to a catalyst that includes at least a supported precious metal component such as one or more platinum group metals (PGMs) that effectively removes ammonia from an exhaust stream. In specific embodiments, the precious metal may include platinum, palladium, rhodium, ruthenium, iridium, silver, or gold. In specific embodiments, the precious metal component includes a physical mixture or a chemically or atomically doped combination of precious metals.

[0071] The precious metal component is typically deposited on a high surface area refractory metal oxide support. Examples of suitable high surface area refractory metal oxides include alumina, silica, titania, ceria and zirconium oxides, magnesium oxide, barium oxide, manganese oxide, tungsten oxide and rare earth metal oxides, base metal oxides and physical mixtures, chemical combinations and / or atomically doped combinations thereof.

[0072] As used herein, the terms "NOx adsorption catalyst" and "NOx trap (also known as lean NOx trap, abbreviated as LNT)" refer to a catalyst that reduces nitrogen oxide (NO and NO2) emissions of lean-burn internal combustion engines by means of adsorption. Typical NOx traps include alkaline earth metal oxides such as oxides of Mg, Ca, Sr and Ba, alkali metal oxides such as oxides of Li, Na, K, Rb and Cs, and rare earth metal oxides such as oxides of Ce, La, Pr and Nd in combination with a precious metal catalyst such as platinum dispersed on an alumina support, which has been used to purify the exhaust gas of internal combustion engines. For NOx storage, barium oxide is generally preferred because it forms nitrates when the lean-burn engine is operated and releases the nitrates relatively easily under rich conditions.

[0073] As used herein, the term "hydrocarbon trap" refers to a catalyst that traps hydrocarbons during cold operation and releases them for oxidation during higher temperature operation. The hydrocarbon trap may be provided by one or more hydrocarbon (HC) storage components for adsorbing various hydrocarbons (HC). Typically, hydrocarbon storage materials with minimal noble metal and material interactions may be used, such as microporous materials, such as zeolites or zeolite-like materials. Preferably, the hydrocarbon storage material is a zeolite. Beta zeolite is particularly preferred because the large pore size of beta zeolite allows for efficient capture of hydrocarbon molecules of diesel derivatives. In addition to beta zeolite, other zeolites such as faujasite, chabazite, clinoptilolite, mordenite, silicalite, zeolite X, zeolite Y, ultrastable zeolite Y, ZSM-5 zeolite, offretite may also be used to enhance HC storage in cold start operation.

[0074] Other aspects include a method for treating exhaust gas from an internal combustion engine, comprising:

[0075] (1) providing a particle filter as described herein, and

[0076] (2) The exhaust gas of the engine is passed through the particulate filter.

[0077] In one or more embodiments, the particulate filter is canned. In an alternative embodiment, the filter is non-canned. "Canned" means that the particulate filter has been incorporated into a housing and is incorporated into the emission treatment system.

[0078] "Non-canned" means that the particulate filter has not yet been incorporated into a housing and is incorporated into an emission treatment system, but is still coated with a layer of functional material. In a typical canning process, the particulate filter is encased in a carrier mat (which is usually formed of ceramic fibers or alumina fibers) and then incorporated into a metal housing. Methods for incorporating a particulate filter into a metal housing include, for example, "clam shell", "stuffing" and "tourniquet" techniques. Such techniques are known in the art.

[0079] It has surprisingly been found that a particulate filter exhibits a combination of high fresh filtration efficiency and reduced backpressure increase when incorporated into an emissions treatment system of an internal combustion engine. Example

[0080] The present invention is more fully illustrated by the following examples, which are set forth for the purpose of illustrating the present invention and should not be construed as limiting it. Unless otherwise indicated, all parts and percentages are by weight, and all weight percentages are expressed on a dry basis, which means that water content is not included, unless otherwise indicated. In each example, the support is cordierite. SEM images of the inorganic material powders were obtained by Zeiss Supra 55.

[0081] Example 1 - Comparison

[0082] The gasoline particulate filter was obtained from Corning. The filter substrate had a size of 100 mm (D)*120 mm (L), 0.94 L (57 in 3 ), a pore density of 300 pores per square inch, a wall thickness of about 200 μm, a porosity of 65% and an average pore size of 20 μm in diameter (measured by mercury intrusion). This filter was used as a control sample without any treatment.

[0083] Example 2

[0084] A gasoline particulate filter according to Example 1, on which a functional layer is applied to the inlet side of the filter.

[0085] The applied functional material layer is high surface area gamma-alumina. The alumina is dry ground to a particle size of 90% 5 microns, 50% 2.5 microns and 10% 1 micron, which has a specific surface area (BET model, 77K nitrogen adsorption measurement) of 70 m after calcination at 1000°C in air for 4 hours. 2 ·g -1 As shown in Figures 2(a) and 2(b), high surface area γ-alumina in powder form was mixed with a gas carrier and blown into the component at room temperature. The flow rate of the gas carrier was 750 kg / h. The loading of the functional material layer was 0.123 g / in 3 .

[0086] After coating, the filter and inlet functional material layer were dried and then calcined at a temperature of 450° C. for about 30 minutes.

[0087] Example 3

[0088] A gasoline particulate filter according to Example 1, on which a functional layer is applied to the inlet side of the filter.

[0089] The applied functional material layer comprises high surface area γ-alumina and low surface area boehmite alumina. The high surface area γ-alumina is described in Example 2. As shown in FIG. 3( a) and FIG. 3( b), the low surface area boehmite alumina has a particle size of 90% 200 μm, 50% 70 μm and 10% 10 μm, and after calcination at 1000° C. in air for 4 hours, the specific surface area (BET model, 77K nitrogen adsorption measurement) is 10 m 2 ·g -1 The functional material layer was mixed with the gas carrier and blown into the filter at room temperature. The flow rate of the gas carrier was 750 kg / h. The total loading of the functional material layer was 0.123 g / in 3 , and the weight ratio of high surface area γ-alumina to low surface area boehmite alumina is 18:1.

[0090] After coating, the filter and inlet functional material layer were dried and then calcined at a temperature of 450° C. for about 30 minutes.

[0091] Example 4

[0092] The gasoline particulate filter according to Example 3, wherein the total loading amount of the functional material layer is 0.123 g / in 3 , and the weight ratio of high surface area γ-alumina to low surface area boehmite alumina is 7.3:1.

[0093] Example 5

[0094] The gasoline particulate filter according to Example 3, wherein the total loading amount of the functional material layer is 0.123 g / in 3 , and the weight ratio of high surface area γ-alumina to low surface area boehmite alumina is 4:1.

[0095] Example 6

[0096] The gasoline particulate filter according to Example 3, wherein the total loading amount of the functional material layer is 0.123 g / in 3 , and the functional material layer contains only low surface area boehmite alumina.

[0097] Example 7 - Testing

[0098] The back pressure characteristics of the above coated gasoline particulate filter examples (Examples 1 to 6) were studied under a cold air flow of 600 cubic meters per hour (cmh). The results are shown in Figure 4 The filters with the functional material layer applied exhibited a slight increase in backpressure compared to the prior art bare gasoline particulate filters; however, as shown in Examples 3 to 6, the introduction of low surface area boehmite alumina with larger sized particles significantly reduced the backpressure of the coated filters.

[0099] The filtration efficiency of the above coated gasoline particulate filter embodiment in the fresh state (0 km or out-of-box state) is in the first close-coupled position (SGE 1.5L turbo gasoline direct injection engine; WLTC test; PN engine out = 3.5×10 12 # / km) measurement, and the results are shown in Figure 5 All coated gasoline particulate filters with applied functional material layers exhibited significant increases in fresh filtration efficiency compared to prior art filters without a functional material layer applied thereto. Notably, as the proportion of low surface area boehmite alumina with larger sized particles in the functional material layer increased, the fresh filtration efficiency values ​​initially remained constant (Example 3, with ~5.3% boehmite alumina), and then rapidly decreased (Examples 4-6).

[0100] Example 8 - Comparison

[0101] A gasoline particulate filter with catalytic material was prepared using a single coating starting from the inlet side. Prior art three-way conversion (TWC) catalyst composites contain palladium and rhodium with a total precious metal loading of 7 g / ft 3 The ratio of Pt / Pd / Rh is 0 / 2 / 5. 3 ), a pore density of 300 pores per square inch, a wall thickness of about 200 μm, a porosity of 63%, and an average pore size of 19 μm in diameter (measured by mercury intrusion). The coating was prepared as follows:

[0102] The components applied from the inlet side were a high surface area gamma-alumina, ceria-zirconia composite (with 40 wt% ceria as an oxygen storage component, palladium, rhodium, barium oxide, and zirconium oxide in concentrations of about 24.8%, 68.7%, 0.1%, 0.2%, 5.0%, and 1.3%, respectively, based on the calcined weight of the catalyst). The barium oxide was introduced as a hydroxide solution. The zirconium oxide was introduced as a nitrate solution. The total coating loading was 1.23 g / in 3 .

[0103] Rhodium in the form of a rhodium nitrate solution is impregnated onto a high surface area gamma-alumina and ceria zirconia composite by a planetary mixer (P-mixer) to form a wet powder while achieving incipient wetness. Palladium in the form of a palladium nitrate solution is impregnated onto a high surface area gamma-alumina and ceria zirconia composite by a planetary mixer (P-mixer) to form a wet powder while achieving incipient wetness. An aqueous slurry is formed. The barium solution and the zirconium solution are added. The slurry is ground to a particle size of 90% 5 microns. The slurry is then coated on the inlet side of a wall flow cordierite filter using a deposition method known in the art. After coating, the filter and inlet coating are dried and then calcined at a temperature of 550°C for about 1 hour.

[0104] Example 9

[0105] A catalyzed gasoline particulate filter according to Example 8, wherein a prior art three-way conversion (TWC) catalyst composite is the primary catalytic layer and an additional functional material layer is loaded on the inlet side of the filter.

[0106] The applied functional material layer comprises high surface area gamma-alumina and low surface area boehmite alumina as described in the previous examples (Examples 2 and 3). The functional material layer is mixed with a gas carrier and blown into the filter at room temperature. The flow rate of the gas carrier is 750 kg / h. The total loading of the functional material layer is 0.052 g / in 3 , and the weight ratio of high surface area gamma-alumina to low surface area boehmite alumina is 8: 1. After coating, the filter and inlet functional material layer are dried and then calcined at a temperature of 450° C. for about 30 minutes.

[0107] Example 10

[0108] The catalytic gasoline particulate filter according to Example 10, wherein the applied functional material layer comprises high surface area γ-alumina (as in the previous example) and low surface area magnesium oxide. As shown in FIG. 6( a ) and FIG. 6( b ), the low surface area magnesium oxide has a particle size of 90% of 20 μm, 50% of 8 μm and 10% of 2 μm, and after calcination at 1000° C. in air for 4 hours, the specific surface area (BET model, 77K nitrogen adsorption measurement) is 18 m 2 ·g -1 The functional material layer was mixed with the gas carrier and blown into the filter at room temperature. The flow rate of the gas carrier was 750 kg / h. The total loading of the functional material layer was 0.052 g / in 3 , and the weight ratio of high surface area gamma-alumina to low surface area magnesium oxide is 8: 1. After coating, the filter and inlet functional material layers are dried and then calcined at a temperature of 450° C. for about 30 minutes.

[0109] Embodiment 11

[0110] A catalyzed gasoline particulate filter according to Example 8, wherein a prior art three-way conversion (TWC) catalyst composite is the primary catalytic layer and an additional functional material layer is loaded on the inlet side of the filter.

[0111] The applied functional material layer comprises a high surface area ceria-alumina containing PGM and a low surface area boehmite alumina (as used in Example 9). The high surface area ceria-alumina composite comprises 49.3% ceria, 49.3% alumina, 1.1% platinum and 0.3% palladium, based on the calcined weight of the powder. Platinum in the form of an amine complex solution is impregnated onto the high surface area ceria-alumina composite using a planetary mixer (P-mixer), and then impregnated with palladium in the form of a palladium nitrate solution to form a wet powder while achieving initial wetness. The powder is then calcined at a temperature of 550°C for about 2 hours and dry-milled to a particle size of 90% 5.1 microns, 50% 2.1 microns and 10% 0.8 microns, which has a specific surface area (BET model, 77K nitrogen adsorption measurement) of 66 m after calcination at 1000°C in air for 4 hours. 2 ·g -1 The high surface area ceria-alumina composite containing PGM and the low surface area boehmite alumina in powder form were mixed with a gas carrier and blown into the filter at room temperature. The flow rate of the gas carrier was 750 kg / h. The total loading of the functional material layer was 0.052 g / in 3 , the weight ratio of high surface area gamma-alumina to low surface area boehmite alumina is 8: 1. After coating, the filter and inlet functional material layer are dried and then calcined at a temperature of 450° C. for about 30 minutes.

[0112] Example 12

[0113] A catalyzed gasoline particulate filter according to Example 11, wherein the applied functional material layer comprises high surface area ceria-alumina containing PGM (as described in Example 11) and low surface area magnesium oxide (as described in Example 10).

[0114] Example 13 - Testing

[0115] The back pressure characteristics of the above coated gasoline particulate filter examples (Examples 8-12) were studied under a cold air flow of 600 cubic meters per hour (cmh). The results are shown in Figure 7The filters with the functional material layers applied showed a slight increase in back pressure compared to the prior art catalytic gasoline particulate filters. In addition, at the same functional material layer weight ratio, the boehmite alumina material was slightly more effective in reducing the back pressure of the final filter compared to the magnesium oxide material (Examples 9 and 11 vs. Examples 10 and 12).

[0116] The filtration efficiency of the coated gasoline particulate filter embodiment described above in the fresh state (0 km or out-of-box state) is in the first close-coupled position (SGE 1.5L turbo gasoline direct injection engine; WLTC test; PN engine failure = 3.5×10 12 # / km) and the results are displayed in Figure 8 All coated gasoline particulate filters with applied functional material layers also exhibited significant increases in fresh filtration efficiency compared to prior art filters without applied functional material layers. Notably, at the same functional material layer weight ratio, filters with boehmite alumina material and with magnesium oxide material showed no difference in fresh filtration efficiency.

Claims

1. A particulate filter for exhaust gas treatment of an internal combustion engine, comprising: (1) A particle filter having an inlet side and an outlet side; (2) A functional material layer coated on the inlet side, outlet side or both sides of the particle filter, wherein the functional material layer comprises: (1) A first inorganic material comprising one or more of aluminum oxide, zirconium oxide, cerium oxide, silicon dioxide, titanium dioxide, and rare earth metal oxides other than cerium oxide, wherein the first inorganic material has a D of 1.2 to 8 μm. 50 ;and (2) a second inorganic material, which includes one or more of aluminum oxide, zirconium oxide, cerium oxide, silicon dioxide, titanium dioxide, magnesium oxide, zinc oxide, manganese oxide, silicate zeolite, and aluminosilicate zeolite, wherein the second inorganic material has a D between 10 and 200 μm. 50 ,as well as The weight percentage of the second inorganic material in the functional material layer is between 1 and 25%. 2 . The particulate filter according to claim 1 , wherein the functional material layer further comprises a first platinum group metal (PGM) selected from the group consisting of platinum (Pt), palladium (Pd), rhodium (Rh), and mixtures thereof.

3. The particle filter according to claim 1, wherein the second inorganic material has a D 50 .

4. The particle filter according to claim 2, wherein the second inorganic material has a D 50 . 5 . The particle filter according to claim 1 , wherein the weight percentage of the second inorganic material in the functional material layer is between 5 and 20%. 6 . The particle filter according to claim 2 , wherein the weight percentage of the second inorganic material in the functional material layer is between 5 and 20%. 7 . The particle filter according to claim 3 , wherein the weight percentage of the second inorganic material in the functional material layer is between 5 and 20%.

8. The particle filter according to claim 4, wherein the weight percentage of the second inorganic material in the functional material layer is between 5 and 20%.

9. The particulate filter according to any one of claims 1 to 8, wherein the loading amount of the second inorganic material is between 0.05 and 5 g / L.

10. The particulate filter according to claim 9, wherein the loading amount of the second inorganic material is between 0.1 and 2 g / L.

11. The particulate filter according to claim 9, wherein the loading amount of the second inorganic material is between 0.15 and 1 g / L.

12. The particle filter according to any one of claims 1 to 8, wherein the first inorganic material has a D 50 .

13. The particle filter according to claim 9, wherein the first inorganic material has a D 50 .

14. The particulate filter according to any one of claims 1 to 8, wherein the particulate filter further comprises a porous body comprising a plurality of pores, and a catalytic carrier coating located within at least a portion of the plurality of pores, wherein the catalytic carrier coating comprises one or more of a selective catalytic reduction (SCR) catalyst, a diesel oxidation catalyst (DOC), a three-way conversion (TWC) catalyst, and an AMOx catalyst; wherein the catalytic carrier coating is applied to the particulate filter before applying the functional material layer.

15. The particulate filter of claim 13, wherein the particulate filter further comprises a porous body comprising a plurality of pores, and a catalytic washcoat layer disposed within at least a portion of the plurality of pores, wherein the catalytic washcoat layer comprises one or more of a selective catalytic reduction (SCR) catalyst, a diesel oxidation catalyst (DOC), a three-way conversion (TWC) catalyst, and an AMOx catalyst; Therein, a catalytic washcoat is applied to the particle filter before the functional material layer is applied.

16. The particulate filter according to any one of claims 1 to 8, wherein the particulate filter further comprises a porous body comprising a plurality of pores, and a catalytic washcoat layer located within at least a portion of the plurality of pores, wherein the catalytic washcoat layer comprises one or more of a NOx trap, a NOx absorber catalyst, and a hydrocarbon trap catalyst; Therein, a catalytic washcoat is applied to the particle filter before the functional material layer is applied.

17. The particulate filter of claim 13, wherein the particulate filter further comprises a porous body comprising a plurality of pores, and a catalytic washcoat layer disposed within at least a portion of the plurality of pores, wherein the catalytic washcoat layer comprises one or more of a NOx trap, a NOx absorber catalyst, and a hydrocarbon trap catalyst; Therein, a catalytic washcoat is applied to the particle filter before the functional material layer is applied.

18. The particle filter according to any one of claims 1 to 8, wherein the functional material layer is applied in the form of particles.

19. The particle filter according to claim 15 or 17, wherein the functional material layer is applied in the form of particles.

20. The particle filter according to claim 18, wherein the functional material layer is applied in a particle form via a gas phase carrier.

21. A method for treating exhaust gas from an internal combustion engine, comprising: (1) A particle filter according to any one of claims 1 to 20, and (2) Exhaust gas from the engine is passed through the particulate filter.

22. The method of claim 21, wherein the exhaust gas contains unburned hydrocarbons, carbon monoxide, nitrogen oxides, and particulate matter.

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