Method for manufacturing a catalytically active particulate filter, catalytically active particulate filter, exhaust gas cleaning system and exhaust gas cleaning method

Abstract

The present invention relates to a method for manufacturing particulate filters for use in exhaust gas systems. In particular, it relates to so-called wall-flow filter substrates coated with a dry ceramic powder in the inlet area. Also disclosed is a corresponding filter or an exhaust gas system containing the filter and its use in a method for exhaust gas purification.

Description

[0001] The present invention relates to a method for manufacturing particulate filters for use in exhaust gas systems. In particular, it relates to so-called wall-flow filter substrates coated with a dry ceramic powder in the inlet area. Also disclosed is a corresponding filter or an exhaust gas system containing the filter and its use in a method for exhaust gas purification.

[0002] The exhaust gases from combustion engines in motor vehicles typically contain the harmful gases carbon monoxide (CO) and hydrocarbons (HC), nitrogen oxides (NOx). x ) and, if applicable, sulfur oxides (SO₄) x), as well as particles consisting largely of solid carbonaceous particles and, where applicable, adhering organic agglomerates. These are referred to as primary emissions. CO, HC, and particles are products of the incomplete combustion of fuel in the engine's combustion chamber. Nitrogen oxides are formed in the cylinder from nitrogen and oxygen in the intake air when combustion temperatures exceed 1200°C. Sulfur oxides result from the combustion of organic sulfur compounds, which are always present in small quantities in non-synthetic fuels. Compliance with future legal emission limits for motor vehicles in Europe, China, North America, and India requires the extensive removal of these pollutants from the exhaust gas.To remove these emissions from vehicle exhaust gases, which are harmful to the environment and human health, a variety of catalytic exhaust gas purification technologies have been developed. Their basic principle typically involves passing the exhaust gas to be cleaned over a flow-through or wall-flow honeycomb structure with a catalytically active coating applied to it. The catalyst promotes the chemical reaction of various exhaust gas components, forming harmless products such as carbon dioxide, water, and nitrogen. Diesel particulate filters (DPF) and gasoline particulate filters (GPF) / gasoline particulate filters (GPF), with and without an additional catalytically active coating, are suitable devices for removing particulate emissions.

[0003] The flow-through or wall-flow honeycomb structures described above are also referred to as catalyst supports, substrates, monoliths, or substrate monoliths, as they carry the catalytically active coating on their surface or within the walls that form this surface. The catalytically active coating is often applied to the catalyst support in a so-called coating process in the form of a suspension. Many such processes have been published in the past by automotive catalytic converter manufacturers (EP1064094B1, EP2521618B1, WO10015573A2, EP1136462B1, US6478874B1, US4609563A, WO9947260A1, JP5378659B2, EP2415522A1, JP2014205108A2).

[0004] Exhaust gases from combustion engines that run predominantly (>50% of operating time) on a stoichiometric air / fuel mixture, such as gasoline or natural gas-powered spark-ignition engines, are cleaned using conventional methods with the aid of three-way catalytic converters (TWCs). These are capable of simultaneously converting the three main gaseous pollutants of the engine—hydrocarbons, carbon monoxide, and nitrogen oxides—into harmless components. Stoichiometric means that, on average, exactly as much air is available for the combustion of the fuel present in the cylinder as is required for complete combustion. The air-fuel ratio λ (air / fuel ratio) defines the actual mass of air m available for combustion. L,tats relative to the stoichiometric air mass m L,st : λ=mL.tatsmL,st If λ < 1 (e.g., 0.9), this means "lack of air," and the exhaust mixture is described as rich. If λ > 1 (e.g., 1.1), this means "excess air," and the exhaust mixture is described as lean. The statement λ = 1.1 means that there is 10% more air present than would be necessary for a stoichiometric reaction. The same applies to the exhaust gas of internal combustion engines.

[0005] The catalytically active materials used in well-known three-way catalysts are typically platinum group metals, especially platinum, palladium, and rhodium, which are present, for example, on γ-aluminum oxide as a support material. Three-way catalysts also contain oxygen storage materials, such as cerium / zirconium mixed oxides. In the latter, cerium oxide, a rare-earth metal oxide, is the fundamental component for oxygen storage. Besides zirconium oxide and cerium oxide, these materials can contain additional components such as other rare-earth metal oxides or alkaline earth metal oxides. Oxygen storage materials are activated by the application of catalytically active materials such as platinum group metals and thus also serve as a support material for the platinum group metals. Oxidation catalysts generally contain the noble metals platinum or palladium. These are placed on high-surface-area metal oxides such as...γ-Aluminium oxide is dispersed as a carrier material.

[0006] To comply with legal standards, it is desirable for current and future exhaust aftertreatment applications for combustion engines to combine particulate filters with catalytically active functionalities, both for cost reasons and due to space constraints. The use of a particulate filter—whether catalytically coated or not—leads to a noticeable increase in exhaust backpressure compared to a flow-through filter of the same dimensions, and thus to a reduction in engine torque or potentially increased fuel consumption. To avoid further increasing exhaust backpressure, the amount of oxide support material for the catalytically active elements of the catalyst, or the oxide catalyst materials themselves, is generally lower in a particulate filter than in a flow-through filter.Several efforts have already been made to provide particulate filters that exhibit good catalytic activity through an active coating while still displaying the lowest possible exhaust backpressure. With regard to low exhaust backpressure, it has proven advantageous, for example, if the catalytically active coating is not applied as a layer to the channel walls of a porous wall-flow filter, but rather if the channel walls of the filter are permeated with the catalytically active material (see, for example, WO2005016497A1, JPH01-151706, and EP1789190B1). For this purpose, the particle size of the catalytic coating is selected so that the particles can penetrate the pores of the wall-flow filter and be fixed there by calcination. A disadvantage of catalytically active filters with an in-wall coating is that the amount of catalytically active substance is limited by the absorption capacity of the porous wall.

[0007] It has been shown that applying catalytically active substances to the surfaces of the channel walls of a wall flux honeycomb structure can increase the conversion of pollutants in the exhaust gas. Combinations of surface and in-wall coatings with catalytically active material are also possible, which can further increase the catalytic performance without significantly increasing the back pressure (EP3501648A1).

[0008] In addition to its catalytic effectiveness, another filter function that can be improved by a coating is its filtration efficiency, i.e., the filtering effect itself. WO2011151711A1 describes a method for applying a dry aerosol to an uncoated or catalytically coated filter that carries the catalytically active material in the channel walls (in-wall coating with washcoat). The aerosol is provided by distributing a powdered mineral material and guided over the inlet side of a wall flow filter by means of a gas stream. Here, the individual particles, with a particle size of 0.2 µm to 5 µm, agglomerate into a bridged network of particles and are deposited as a layer on the surface of the individual inlet channels through the wall flow filter. The typical powder loading of a filter is between 5 g and 50 g per liter of filter volume.It is expressly pointed out that it is not desirable to achieve a coating in the pores of the wall flow filter with the metal oxide.

[0009] Another method for increasing the filtration efficiency of catalytically inactive filters is described in WO2012030534A1. In this method, a filtration layer ("discriminating layer") is created on the walls of the inlet-side flow channels by depositing ceramic particles via a particle aerosol. The layers consist of oxides of zirconium, aluminum, or silicon, preferably in fiber form with a length of 1 nm to 5 µm and a thickness of more than 10 µm, typically 25 µm to 75 µm. After the coating process, the applied powder particles are calcined in a thermal process.

[0010] Another method for increasing the filtration efficiency of non-catalytically active wall-flow filters, in which a membrane ("trapping layer") is created on the surfaces of the filter inlet channels, is described in patent US8277880B2. The filtration membrane on the inlet channel surfaces is created by drawing a gas stream loaded with ceramic particles (e.g., silicon carbide or cordierite) through it. After the filter layer is applied, the honeycomb structure is fired at temperatures above 1000°C to increase the adhesion of the powder layer to the channel walls. Further coating methods using powder application are mentioned in EP2502661A2 and EP2502662B1.

[0011] A coating within the pores of a wall-flow filter substrate by atomizing dry particles is described in US 8388721B2. Here, however, the powder is intended to penetrate deep into the pores. Between 20% and 60% of the wall surface should remain accessible to soot particles, and thus open. Depending on the flow velocity of the powder-gas mixture, a more or less pronounced powder gradient between the inlet and outlet sides can be established. The pores of the channel walls of the filter coated with powder according to US 8388721B2 can subsequently be coated with a catalytically active component. Here, too, the catalytically active material is located within the channel walls of the filter.

[0012] The introduction of the powder into the pores, e.g., using an aerosol generator, is also described in EP2727640A1. Here, a non-catalytically coated wall flow filter is coated with a gas stream containing, for example, aluminum oxide particles, such that the complete particles, which have a particle size of 0.1 µm to 5 µm, are deposited as a porous filling in the pores of the wall flow filter. The particles themselves can provide an additional functionality of the filter beyond its filtration effect. For example, these particles are deposited in the pores of the filter at a quantity of more than 80 g / l, based on the filter volume. They fill 10% to 50% of the volume of the filled pores in the channel walls. This filter exhibits improved filtration efficiency compared to the untreated filter, both when loaded with soot and when unloaded, while the soot-loaded filter has a lower exhaust backpressure.

[0013] In WO2018115900A1, wall flow filters are coated with a possibly dry synthetic ash in such a way that a continuous membrane layer is created on the walls of the possibly catalytically coated wall flow filter.

[0014] Applying dry powder to the filter inlet side generally leads to increased filtration efficiency with only a moderate increase in exhaust backpressure. However, this powder does not adhere firmly to the filter wall surface on which it is deposited. Therefore, it can be easily washed away by condensation present in the exhaust system, which reduces the filtration efficiency of the wall-flow filter with continued use.

[0015] WO2023026022A1 and US20240238772A1 each relate to a method for forming an inorganic oxide coating on a wall flow filter suitable for treating exhaust gas. In particular, the method includes spraying inorganic particles and a silicone resin as a dry particulate aerosol to form a coating layer. According to these documents, a powder mixture of silicone resin and inorganic particles is prepared, which is then sprayed together onto a suitable filter, which is subsequently calcined.

[0016] WO2020047708A1 describes a wall flow filter comprising a porous ceramic honeycomb structure with a first end, a second end, and multiple walls with porous wall surfaces defining several internal channels. A porous inorganic material, arranged on one or more wall surfaces, is bound to the wall flow filter by binders containing, among other things, silicone resin. A solution containing the silicone resin is contacted with the porous material in a solvent, and the porous material is then atomized onto the filter as the solvent evaporates. Finally, the organic material is burned out of the filter. During solvent evaporation, the described process generates aggregates or agglomerates of primary particles of varying sizes, which then preferentially deposit onto the wall of the wall flow filter.

[0017] Both of the aforementioned documents agree that adding silicone resin improves the adhesion of the powder to the wall surface of the particulate filter. However, the other desired properties of such a filter substrate for exhaust aftertreatment must not be overlooked. Therefore, there remains a need for potentially catalytically coated wall flow filters that are further optimized with regard to their filtration efficiency, exhaust backpressure, and any catalytic effectiveness. Likewise, care should be taken to ensure that the powder layer adheres as effectively as possible to or within the wall surface of the wall flow filter, thus maintaining consistently good filter performance even over extended periods of operation.

[0018] These and other problems that can be deduced from the prior art by a person skilled in the art are solved by a method for manufacturing a particulate filter with the features of claim 1. Claims 2-7 relate to preferred embodiments of the method. Claim 8 relates to a particulate filter manufactured according to the invention. Claims 9-12 relate to preferred embodiments of the particulate filter. Claims 13-15 relate to a corresponding exhaust system, and claims 16 and 17 relate to the use of the particulate filter and the exhaust system, respectively.

[0019] By comprising a wall flow filter substrate for reducing harmful components from the exhaust gas of combustion engines in a process for manufacturing a catalytically active particulate filter, wherein the wall flow filter substrate has a length L and channels E and A extending parallel between a first and a second end of the wall flow filter substrate, which are separated by porous walls and form surfaces OE and OA respectively, and wherein the channels E at the second end and the channels A at the first end are closed ( Fig. 1) In a first step, high-melting-point metal compound particles comprising a dry powder and coated with a silicone resin are produced such that the coating of the metal compound particles is carried out by bringing the particles together in a solvent suspension with the silicone resin and then evaporating the solvent, and in a second, separate step, the surfaces OE of the catalytically active filter, comprising the powder from the first step, are coated with a dry powder-gas aerosol, and in a third step, the filter together with the powder is heated so that organic components are removed from the filter, the problem is solved surprisingly simply, but no less advantageously. A corresponding particle filter is in Fig. Figure 2 illustrates the key improvement of the present invention over prior art methods in that a more defined powder-silicone resin aerosol can be provided for coating, thus enabling the adjustment of specific filter properties. For example, the dry powder particles coated with silicone resin can be standardized in size before application to the filter, if necessary, to achieve optimal coating of the filter with the powder-gas aerosol. Furthermore, the process is more robust because, for instance, the degree of dryness of the powder-silicone resin mixture can be more precisely controlled before the aerosol is atomized onto the filter. This prevents, for example, the semi-dry powder from adhering to the fixture walls and eliminates the need for periodic removal, thereby reducing maintenance costs.

[0020] All ceramic wall-flow filter substrates known from the prior art and commonly used in automotive exhaust gas catalysis can be employed as wall-flow substrates. Porous wall-flow filter substrates made of cordierite, silicon carbide, or aluminum titanate are preferred. These wall-flow filter substrates have channels E and channels A, which, as described above, function as inlet channels (also called flow channels) and outlet channels (also called outflow channels). The outflow ends of the inlet channels and the upflow ends of the outflow channels are offset from each other and typically sealed with gas-tight plugs. This forces the exhaust gas to be cleaned, which flows through the filter substrate, to pass through the porous wall between the inlet and outlet channels, thus creating a particulate filter effect.The filtration properties for particles can be designed by the porosity, pore / radius distribution, and wall thickness. According to the invention, the porosity of the uncoated wall flow filter substrates is generally more than 40%, for example, from 40% to 75%, particularly from 50% to 70% [measured according to DIN 66133 - latest version on the filing date]. The mean pore size d. 50 The thickness of the uncoated wall flow filter substrate is at least 4 µm, for example from 4 µm to 34 µm, preferably more than 6 µm, in particular more preferably from 6 µm to 25 µm or most preferably from 7 µm to 17 µm [measured according to DIN 66134 latest version on the filing date], wherein under the d 50 The value of the pore size distribution of the wall flow filter substrate is to be understood as meaning that 50% of the total pore volume determinable by mercury porosimetry is formed by pores whose diameter is less than or equal to that specified as d 50 The specified value is.

[0021] The powder contains high-melting-point metal compounds and advantageously does not include any precious metal. It is therefore preferably not catalytically active within the meaning of the present invention. In particular, it is essentially unable to oxidize carbon-containing particles such as soot or volatile hydrocarbon particles, or to oxidize the exhaust gas components CO and HC, or NO. x to reduce. The powder preferably consists of ceramic or oxide components and contains no other catalytic components. Particularly suitable components of the powder are high-melting-point metal compound particles selected from the group consisting of aluminum oxide, zirconium dioxide, cerium oxide, yttrium oxide, mullite, tin oxide, silicon nitride, zeolite, titanium dioxide, silicon dioxide, aluminum titanate, silicon carbide, cordierite, nesosilicates, layered silicates, technical silicates, chain silicates, group silicates, or mixtures thereof.

[0022] For a coating that increases filtration efficiency, powder particles with a tapped density between 50 g / l and 900 g / l are preferably used, more preferably between 200 g / l and 850 g / l, and most preferably between 400 g / l and 800 g / l. According to the invention, the term "filtration-enhancing" means that the powder coating enables the wall flow filter to retain particles from the exhaust gas stream better than the original filter, without causing an exorbitant increase in exhaust gas backpressure relative to the initial substrate. Preferably, this means that the filter's filtration efficiency increases by more than 2 percentage points, more preferably by more than 5 percentage points, and most preferably by more than 10 percentage points compared to the initial substrate, without the exhaust gas backpressure increasing by more than 60%, more preferably by less than 50%, and most preferably by less than 40% compared to the initial substrate.

[0023] The increase in filtration efficiency of the powder-coated filter compared to the raw filter is calculated using the following formula: FE increase through powder coating > / = (100% − FE before F) × increase factor

[0024] In the case according to the invention, the increase factor is in the range of 0.2 to 0.99, preferably in the range of 0.35 to 0.95, and particularly preferably in the range of 0.5 to 0.85. This is especially advantageous for filter substrates that already exhibit high filtration efficiency in the initial substrate.

[0025] The increase in exhaust back pressure can be calculated using the following formula: Increase in back pressure due to powder coating = ((back pressure with powder coating / back pressure without powder coating) - 1) × 100

[0026] The increase in exhaust back pressure remains rather moderate due to the powder coating. The increase should be less than 30%, preferably less than 20%.

[0027] The powder coating, comprising high-melting-point metal compound particles, preferably exhibits a monomodal, multimodal, or broad Q3 particle size distribution. Depending on the method used to determine the particle size distribution of the coating, a distinction is made between number-based (Q0) and volume-based (Q3) particle size distributions (M. Stieß, Mechanical Process Engineering - Particle Technology 1, Springer, 3rd edition 2009, page 29). The powder coating on the porous walls of the wall-flow filter substrate has a D 50 -value of the particle size distribution of the membrane particles (Q3; DIN 66143 - latest version on the filing date), which is advantageously equal to or smaller than the d 50-Value of the pore size distribution of the wall flow filter substrate (Q3; measured according to DIN 66133 - latest version on the filing date). The high-melting-point metal compound particles preferably have a mean particle diameter of 0.1 µm - 20 µm, more preferably 0.2 µm - 10 µm and most preferably 0.3 µm - 5 µm (D50; Q3 distribution).

[0028] The mean pore size d 50 The powder coating thickness is at least 50 nm, for example 50 nm to 5 µm, preferably more than 100 nm to 4 µm, and particularly preferably 200 nm to 2.5 µm, wherein the thickness is defined below the d 50 The value of the pore size distribution is understood to mean that 50% of the total pore volume determinable by mercury porosimetry is formed by pores whose diameter is less than or equal to that specified as d 50 The specified value is the value. The values ​​are determined as described above.

[0029] The BET surface area of ​​the silicone resin-coated powder is at least 85 m2 / g, for example 85 m2 / g to 210 m2 / g, preferably more than 100 m2 / g to 200 m2 / g, in particular more preferably 120 m2 / g to 180 m2 / g.

[0030] According to the invention, the powder, comprising the high-melting-point metal compound particles, is coated with a silicone resin, preferably encapsulated. This is advantageously achieved by bringing the powder into contact with a solvent in which the resin is dissolved and then drying it. After drying, the individual powder components are preferably present such that the primary particles have a coating of dry silicone resin. It is preferred if the high-melting-point metal compound particles do not bond together and form larger secondary particles. In particular, these should not be aggregated or agglomerated. The degree of agglomerated / aggregated particles is less than 25%, preferably less than 10%, of the total mass of the coated or encapsulated powder particles. If necessary,The agglomerated / aggregated particles are first deagglomerated / deaggregated using special processes known to those skilled in the art (e.g., by applying shear forces, such as baffle plates). Additionally, excessively large particles can be easily removed from the powder. Besides resulting in a more defined particle size distribution, which allows for better generation of a powder-gas aerosol, this also makes it possible to preferentially transport the powder particles into the surface pores of the wall flow filter, rather than simply depositing them on the wall surface. The result is ultimately improved adhesion of the powder to the wall of the wall flow filter.

[0031] As already mentioned, the coating or encapsulation of the metal compound particles is carried out by bringing the powder particles together with the silicone resin in a solvent suspension and then evaporating the solvent – ​​preferably in such a way that as few agglomerates / aggregates as possible form. On an industrial scale, this can be most easily achieved using a so-called spray drying process. Such processes are known to those skilled in the art (https: / / de.wikipedia.org / w / index.php?title=Spr%C3%BChtrocknunq&oldid=229912829). Spray drying further helps to avoid the formation of larger aggregates or agglomerates of powder particles. The final product preferably consists of the primary particles coated or encapsulated with the dry silicone resin. Therefore, it is particularly preferred if this process step is carried out in a spray dryer.The dry powder particles, or a more defined fraction thereof with a preferred particle size distribution, can then be used for powder coating the wall flow filter.

[0032] Silicone resins belong to the class of organopolysiloxanes and consist of an irregular, three-dimensional network of primarily tri- or tetrafunctional units. Thanks to their high Si-O bond energy, the various organopolysiloxane types are very stable. Silicone resins combine very well with organic polymers. This allows many properties, such as crosslinking behavior, flexibility, adhesion, and weather resistance, to be tailored as needed (https: / / spiegato.com / de / was-ist-silikonharz). Experts are familiar with the silicone resins that can be used advantageously in this context (https: / / de.wikipedia.org / w / index.php?title=Silikonharzlack&oldid=225671739). These are commercially available (https: / / www.wacker.com / cms / de-de / products / product-groups / silicone-resins / siliconeresins.html; https: / / www.dow.com / documents / de-de / cataloqg-selection-quide / 25-799-silicone-resins-intermediates-selection-quide.pdf?iframe=true).Advantageously, a silicone resin is selected for coating the metal compound particles from the group consisting of alkyl- or aryl- or alkyl- and aryl-functionalized oligomers or polymeric silicone resins of formula [A. w R x SiX y O z ] n with A as an alkyl group, R as an aryl group, and X as a functional group on silicon (e.g., hydroxyl, alkoxyl). Methyl- and / or phenyl-substituted polymeric silicone resins with hydroxyl functionalities on silicon are particularly preferred.

[0033] The amount of silicone resin used for the coating process can be determined by a person skilled in the art. It should be selected such that the powder exhibits sufficient strength on and / or within the filter wall after final calcination in the filter. This can be determined through routine experiments. Preferably, the powder particles have a silicone resin content of 20%–150% by mass, more preferably 50%–130%, and most preferably 80%–120% of the total weight of the high-melting-point metal compound particles.

[0034] The solvent used in this process can be determined by a person skilled in the art. It is generally an organic solvent, as silicone resins are readily soluble in it. Alternatively, water can be used if water-soluble silicone compounds are employed or if the silicone resins can be dispersed in the water with the aid of additives. A person skilled in the art knows how to proceed in this regard. Preferably, one or more solvents selected from the group consisting of ethanol (EtOH), mecoethanol (MeOH), isopropanol, toluene, benzene, acetone, tetrahydrofuran, xylene, ethyl acetate, methyl isobutyl ketone, 2-butanone, dimethyl sulfoxide, ethers, and esters are suitable. EtOH, mecoethanol, isopropanol, and acetone are particularly preferred. Mixtures can also be used.

[0035] After generating the dry, silicone resin-coated powder particles, these are transferred to the wall flow filter in a subsequent step independent of the powder particle production process. This is achieved by atomizing the powder particles into a gas stream, which is then passed through the catalytically active wall flow filter (e.g., EP3595796A1). Separating the steps for producing the dry, silicone resin-coated powder particles from the process of transferring them to the wall flow filter offers the advantage of allowing for the precise application of powder particles of specific sizes. Firstly, the desired particle sizes can be precisely set in the initial process step. Secondly, specific size ranges can be selected from the produced powder particles, and aggregated / agglomerated particle clumps can be deagglomerated if necessary and desired.Decoupling the production of the coated or encapsulated powder particles from their introduction into a wall flow filter allows for better adjustment of the filter's properties. The specifically manufactured powder particles and their introduction rate enable targeted optimization of the subsequent filtration efficiency and exhaust backpressure of the particulate filter.

[0036] An advantageous method involves dispersing these powder particles in a gas and introducing this aerosol into a gas stream, in order to subsequently allow the powder-gas aerosol to flow into the wall flow filter. Those skilled in the art know how to proceed in this manner (DE102018111246A1, WO2011151711A1, WO2021028691A1 and the literature cited therein). In a preferred process, the powder particles are introduced into the wall flow filter in the gas stream at such an accelerated speed that the particles penetrate the pores of the channel walls and form a loose mixture there. Preferably, the powder-gas aerosol enters the filter at a velocity of 10 m / s to 50 m / s, more preferably 10 m / s to 20 m / s, or is drawn into it. This is most preferably carried out in an apparatus as described in DE102018111246A1. The boundary conditions and preferred embodiments described therein also apply here mutatis mutandis.

[0037] In a final process step, the wall flow filter produced in this way is heated. During this process, organic components of the silicone resin are removed from the filter, and the resulting silicate matrix binds the powder particles to each other and to or within the wall of the wall flow filter. Treated in this way, the powder particles can no longer be carried out of the wall flow filter by water accumulating from the combustion of the fuel in the exhaust system. The powder therefore remains in place and gives the wall flow filter its advantageous properties over a long period of time.

[0038] The thermal treatment of the wall flow filter, which is coated with the powder material, is carried out according to the specifications of a person skilled in the art. For this purpose, the wall flow filter can, for example, be heated in a suitable oven, in particular a convection oven, for a certain period of time, possibly in a specific gas atmosphere, to elevated temperatures until the organic components have evaporated from the silicone resin. The thermal fixation of the powder particles generally takes place at 400–800°C, preferably at 500–600°C. The duration of the thermal fixation is generally 1–4 hours, preferably 2–3 hours.

[0039] In a further embodiment, the present invention also relates to a catalytically active particle filter produced according to the method just described. The particle filter according to the invention differs from those of the prior art. At a minimum, the particle filter should have a larger mass of powder particles in the wall, since—as already mentioned—primary particles are preferably introduced into the wall-flow filter, and preferably not agglomerates or aggregates thereof. In a preferred embodiment, at least 30% of the total mass of the powder is located in the porous walls of the wall-flow filter substrate. More preferably, at least 40%, and most preferably up to 60% or up to 50% of the total mass. The powder particles thus penetrate the porous filter wall. However, the penetration depth is preferably limited.The penetration depth of the powder particles into the filter wall is, on average across all particles, a maximum of 50% of the wall thickness, preferably a maximum of 40%, and most preferably a maximum of 25%. These determinations can be carried out analogously to DE102018111246A1 by appropriate measurements.

[0040] In total, the person skilled in the art can atomize any desired amount of powder into the wall flow filter. A certain value should not be undercut, otherwise the desired filtration efficiency will not be achieved. If the loading is chosen to be too high, the exhaust gas back pressure increases accordingly. If the powder consists, for example, of pyrogenically produced metal oxides, then the loading of the wall flow filter with powder particles can be less than 1 g / L, preferably less than 0.5 g / L. For other, non-pyrogenically produced metal compounds, the amount of powder particles in the wall flow filter is up to 50 g / L, based on the volume of the wall flow filter substrate, preferably up to 30 g / L and most preferably up to 25 g / L. A lower limit here is 1 g / L.

[0041] The catalytically active particle filter according to the invention is characterized by the fact that it comprises a thermally silicate-fixed powder with high-melting-point metal compound particles on or in the inlet surface O E of the filter. Corresponding powder particles were applied to the wall flow filter using a coating process in which a powder-gas aerosol was introduced into the filter. As a result, the powder particles are found at least in the surface pores of the wall flow filter. The powder particles can fill the pores up to the edge of the wall surface. E refill. However, it is also possible that more powder particles are introduced into the wall flow filter, so that the powder particles also settle on the surface O Ebegin collecting. However, a completely continuous surface coating with the powder particles should preferably be avoided. It is therefore preferable if the powder does not form a continuous coating on the surfaces O E trains.

[0042] The particle filter was coated with a catalytically active compound before being exposed to the powder. This compound may have been applied to the filter in the form of a washcoat according to a known pattern. The catalytic coating may be located on the surfaces O E or O A The catalytically active coating may be located within and / or present in the filter wall. It can be zoned. A length of 30%–90%, preferably 50%–80%, of the coatable filter length L is preferred.

[0043] This applies in particular to a coating on the walls O E and / or O A(measured from the end of the particulate filter in each case).

[0044] The catalytically active coating can possess an activity suitable for the present purpose, as would be understood by those skilled in the art. Within the scope of the present invention, "catalytically active" is understood to mean the ability to convert harmful components of the exhaust gas from internal combustion engines into less harmful ones. In particular, the exhaust gas components NOx, CO, and HC are to be mentioned here. Catalysts that are preferably suitable in this context can be selected from the group consisting of three-way catalysts, oxidation catalysts, and NO. xThese materials can be used as storage catalysts, hydrocarbon traps, SCR catalysts, or ammonia slip catalysts. A coating that is three-way catalytically active, particularly at operating temperatures of 250 to 1100 °C, is especially preferred. This coating preferably contains the precious metals palladium and / or rhodium, with platinum being present only exceptionally. The coating is particularly preferably composed of palladium and rhodium and no platinum. In another embodiment, the coating contains the precious metals platinum and / or rhodium, with palladium being present only exceptionally. In yet another embodiment, the coating contains the precious metals platinum, palladium, and rhodium. In this embodiment, it is advantageous if the mass ratio of platinum to palladium is 15:1 to 1:15, particularly 10:1 to 1:10.With regard to the particle filter according to the invention, the proportion of rhodium in the total precious metal content is particularly greater than or equal to 5 wt.%, preferably greater than or equal to 10 wt.%. For example, the proportion of rhodium in the total precious metal content is 5 to 20 wt.% or 5 to 15 wt.%. The precious metals are typically used in quantities of 0.10 to 5 g / l, based on the volume of the wall-flow filter substrate.

[0045] The precious metals are typically fixed to one or more substrate materials. Any material known to those skilled in the art for this purpose can be used as a substrate. Such materials include, in particular, metal oxides with a BET surface area of ​​30 to 250 m². 2 / g, preferably from 100 to 200 m 2 / g (determined according to DIN 66132 - latest version on the filing date). Particularly suitable carrier materials for the precious metals are selected from the following: aluminum oxide, doped aluminum oxide, silicon oxide, titanium dioxide, and mixed oxides of one or more of these. Doped aluminum oxides include, for example, lanthanum oxide, zirconium oxide, barium oxide, and / or titanium oxide-doped aluminum oxides. Aluminum oxide or lanthanum-stabilized aluminum oxide is advantageously used, with the latter containing lanthanum in amounts of, in particular, 1 to 10 wt.%, preferably 3 to 6 wt.%, each calculated as La₂O₃ and based on the weight of the stabilized aluminum oxide.

[0046] For three-way activity, it is preferred if a cerium / zirconium mixed oxide is also present as a support material for the precious metals. Preferred cerium / zirconium mixed oxides comprise one or more rare earth metal oxides and can thus be referred to as cerium / zirconium / rare earth metal mixed oxides. The term "cerium / zirconium / rare earth metal mixed oxide" as used in the present invention excludes physical mixtures of cerium oxide, zirconium oxide, and rare earth oxide. Rather, "cerium / zirconium / rare earth metal mixed oxides" are characterized by a largely homogeneous, three-dimensional crystal structure, which is ideally free of phases of pure cerium oxide, zirconium oxide, or rare earth oxide (solid solution). Depending on the manufacturing process, however, products that are not completely homogeneous may also be formed, which can generally be used without disadvantage. The same applies to cerium / zirconium mixed oxides that do not contain a rare earth metal oxide. Furthermore, the term rare earth metal includes...Rare earth metal oxide within the meaning of the present invention does not include cerium or cerium oxide.

[0047] Suitable rare earth metal oxides in the cerium / zirconium / rare earth metal mixed oxides include, for example, lanthanum oxide, yttrium oxide, praseodymium oxide, neodymium oxide, and / or samarium oxide. Lanthanum oxide, yttrium oxide, and / or praseodymium oxide are preferred. Lanthanum oxide and / or yttrium oxide are particularly preferred, and lanthanum oxide and yttrium oxide, yttrium oxide and praseodymium oxide, as well as lanthanum oxide and praseodymium oxide, are especially preferred. In embodiments of the present invention, the oxygen storage components are free of neodymium oxide. The proportion of rare earth metal oxide in the cerium / zirconium / rare earth metal mixed oxides is, in particular, 3 to 20 wt.% based on the cerium / zirconium / rare earth metal mixed oxide.

[0048] If the cerium / zirconium / rare earth metal mixed oxides contain yttrium oxide as a rare earth metal, its proportion is preferably 4 to 15 wt.% based on the cerium / zirconium / rare earth metal mixed oxide. If the cerium / zirconium / rare earth metal mixed oxides contain praseodymium oxide as a rare earth metal, its proportion is preferably 2 to 10 wt.% based on the cerium / zirconium / rare earth metal mixed oxide. If the cerium / zirconium / rare earth metal mixed oxides contain lanthanum oxide and another rare earth oxide, such as yttrium oxide or praseodymium oxide, their mass ratio is particularly 0.1 to 1.25, preferably 0.1 to 1.

[0049] The coating typically contains oxygen storage components in amounts of 15 to 120 g / l, based on the volume of the wall-flow filter substrate. The mass ratio of carrier materials and oxygen storage components in the coating is typically 0.25 to 1.5, for example, 0.3 to 1.3. For example, the weight ratio of the sum of the masses of all aluminum oxides (including doped aluminum oxides) to the sum of the masses of all cerium / zirconium mixed oxides in coating Z is 10:90 to 75:25.

[0050] In embodiments of the present invention, the coating comprises lanthanum-stabilized aluminum oxide, rhodium, palladium or palladium and rhodium, and a cerium / zirconium / rare earth metal mixed oxide containing yttrium oxide and lanthanum oxide as rare earth metal oxides. In other embodiments of the present invention, the coating comprises lanthanum-stabilized aluminum oxide, rhodium, palladium or palladium and rhodium, and a cerium / zirconium / rare earth metal mixed oxide containing praseodymium oxide and lanthanum oxide as rare earth metal oxides. In other embodiments of the present invention, the coating comprises lanthanum-stabilized aluminum oxide, rhodium, palladium or palladium and rhodium, a cerium / zirconium / rare earth metal mixed oxide containing praseodymium oxide and lanthanum oxide as rare earth metal oxides, and a second cerium / zirconium / rare earth metal mixed oxide containing yttrium oxide and lanthanum oxide as rare earth metal oxides.

[0051] The present invention also relates to a system for cleaning exhaust gases from internal combustion engines, in particular from predominantly stoichiometrically operated internal combustion engines, which includes a particulate filter according to the invention. A further preferred aspect is a system for cleaning exhaust gases characterized in that the particulate filter according to the invention is arranged with its first end (the side exposed to the powder forms the inlet area for the exhaust gas) optionally directly downstream of a three-way or oxidation catalyst located close to the engine. Three-way catalysts and oxidation catalysts are known to those skilled in the art. Both types oxidize HCs and CO in the exhaust gas to H2O and CO2. The three-way catalyst can also reduce NOx to N2 in a stoichiometric exhaust gas environment.

[0052] The filter is therefore arranged in the exhaust stream as a separate unit downstream of the (engine-adjacent) catalyst. It is particularly advantageous if a three-way catalyst is located in a position close to the engine, directly upstream of the wall-flow filter according to the invention. It is also advantageous if a three-way catalyst is located downstream of the wall-flow filter according to the invention. It is also particularly advantageous if a three-way catalyst is located both upstream and downstream of the wall-flow filter according to the invention.

[0053] A system for cleaning exhaust gases is particularly preferred, characterized in that, following the exhaust gas, at least one further catalyst, selected from the group consisting of three-way catalysts, oxidation catalysts, and NO₂ catalysts, is located after the wall flow filter according to the invention. xStorage catalyst, hydrocarbon trap, SCR catalyst, ammonia slip catalyst. The preferred embodiments described for the wall flow filter according to the invention also apply mutatis mutandis to the system mentioned here. Corresponding catalysts are described in the following literature: EP4079399A1, EP4204143A1, EP4072708A1, EP3794221A1, EP3826754A1, EP4126348A1 and the literature cited therein.

[0054] Also related to the present invention is a method for exhaust gas purification of an internal combustion engine, wherein the engine's exhaust gases are passed through a particulate filter or a system comprising such a filter according to the invention. Preferably, the internal combustion engine is one that is predominantly operated stoichiometrically. The preferred and alternative embodiments of the particulate filter and the system according to the invention apply mutatis mutandis. The exhaust gas is guided over the filter in such a way that the inlet side forms the side exposed to the powder.

[0055] "Close to the engine" in the sense of the invention refers to an area in the exhaust system that is located in a position close to the engine, i.e. approximately 10 - 80 cm, preferably 20 - 60 cm away from the engine outlet.

[0056] When the particulate filter according to the invention is used as intended for cleaning exhaust gases from combustion engines, the exhaust gas flows into the filter at one end and exits at the other end after passing through the porous walls. For example, if the exhaust gas enters the filter at the first end, the channels E designate the inlet channels or upstream channels. After passing through the porous walls, it then exits the filter at the second end, so that the channels A designate the outlet channels or downstream channels. L represents the average coatable length of the filter. Due to the plugs at the channel ends, not the entire length of the filter can be coated. L represents the total length actually available for coating in the coated channels, averaged over the number of coated channels. Fig. 2).

[0057] The particulate filter according to the invention exhibits excellent filtration efficiency with no or only a very slight increase in exhaust backpressure. The low overall backpressure is likely due to the fact that the presence of powder particles does not significantly reduce the cross-section of the channels on the inlet side. It is assumed that the powder particle coating forms a porous structure, which has a positive effect on the backpressure. As a result, a filter according to the invention also exhibits a lower backpressure after soot loading than an analogous filter without a powder particle coating, since the coating largely prevents the soot from penetrating the porous filter wall. Furthermore, no signs of detachment of the powder particles from the filter wall are observed, even after prolonged use. An additional catalytic coating, if present, gives the particulate filter according to the invention excellent catalytic capability.

[0058] "Dry" in the context of the present invention means the exclusion of the presence of any liquid, particularly water. In particular, the preparation of a suspension of the powder in a liquid for atomization into a gas stream, which is then fed directly into the wall flow filter with or without drying, should be avoided. A certain level of moisture may be tolerable for both the filter and the powder particles being exposed or coated, provided that the objective – the finest possible deposition of the powder in the porous walls and / or surfaces – is achieved. EThe properties of the wall-flow filter substrate are not negatively affected. The powder is generally free-flowing and dispersible by energy input. The presence of liquid in the dry powder or in the wall-flow filter substrate should be less than 10% by weight, preferably less than 5% by weight, and most preferably less than 1% by weight at the time of application. Those skilled in the art know how to analytically determine the proportion of liquid in the powder or filter.

[0059] The filter according to the invention is typically used primarily in internal combustion engines, especially those with direct injection or port injection. Preferably, these are predominantly stoichiometrically operated gasoline or natural gas engines. Turbocharged engines are also preferred. The requirements for gasoline particulate filters (GPFs) differ significantly from those for diesel particulate filters (DPFs). Diesel engines without a DPF can exhibit up to ten times higher particulate emissions, based on particle mass, than gasoline engines without a GPF (Maricq et al., SAE 1999-01-01530). Furthermore, gasoline engines produce significantly fewer primary particles, and the secondary particles (agglomerates) are considerably smaller than those from diesel engines. Emissions from gasoline engines range in particle sizes from less than 200 nm (Hall et al., SAE 1999-01-3530) to 400 nm (Mathis et al.).(Atmospheric Environment 38, 4347) with a maximum in the range of approximately 60 nm to 80 nm. Therefore, the filtration of nanoparticles in the GPF must primarily occur via diffusion separation. For particles smaller than 300 nm, separation by diffusion (Brownian molecular motion) and electrostatic forces becomes increasingly important with decreasing size (Hinds, W.: Aerosol technology: Properties and behavior and measurement of airborne particles. Wiley, 2nd edition 1999). Nevertheless, the wall flow filter according to the invention can also be used in diesel applications. Figures: Fig. 1: Fig. Figure 1 shows a particle filter with a first (1) and a second end (2) of the wall flow filter substrate extending, which are separated by porous walls (3) and surfaces O E or O AThe channels E at the second end (2) and the channels A at the first end (1) are closed. The flow of exhaust gas through the wall is shown. Fig. 2: Fig. Figure 2 shows a particulate filter according to the invention with surfaces OE and OA. The flow of the exhaust gas through the wall and the powder particle coating (3) is shown. The coatable length L of the wall flow filter is also shown. Fig. 3: Fig. Figure 3 shows a graphical plot of the filtration efficiency and back pressure of the comparison examples VGPF1, VGPF2 and VGPF3 as well as the examples GPF1, GPF2 and GPF3 for comparison. Fig. 4: Fig. Figure 4 shows the enlarged surface area O for comparison. Ea commercially available flow-through filter substrate that was treated with a filtration-enhancing powder (A) or alternatively with a silicone resin-modified filtration-enhancing powder (C) according to the invention and subsequently thermally treated. B shows surface A after treatment with water, D shows surface C after treatment with water. The red circles mark exemplary reopened pores in the surface. Examples:

[0060] If the particle filter is coated with a filtration-enhancing powder via a powder-gas aerosol, the coating is carried out according to the procedure described in EP3595796A.

[0061] Comparative example 1: First, application of filtration-enhancing powder, then coating of the porous wall with a catalytically active layer.

[0062] The surfaces O EA commercially available flow-through filter substrate was treated with a filtration-enhancing powder and then thermally treated. The total loading of the filter with the filtration-enhancing powder was 21 g / L. The surface area O A Subsequently, as described in the literature, a catalytically active layer containing an oxygen storage component, a lanthanum oxide-stabilized aluminum oxide, and palladium and / or rhodium as catalytically active metals was applied in a wet process, with the coating extending over 80% of the substrate length onto the porous filter wall O A The total coating of the filter was 62.5 g / L, the total precious metal coating being 1.67 g / L with a palladium to rhodium ratio of 3.75:1. The resulting coated filter was dried and then calcined. It is referred to below as VGPF1.

[0063] Comparative example 2: Coating with a catalytically active layer on commercially available flow-through filter substrate with a filtration-enhancing coating

[0064] The surfaces O A A commercially available flow-through filter substrate with a filtration-enhancing coating was treated, as described in the literature, with a catalytically active layer containing an oxygen storage component, lanthanum oxide-stabilized aluminum oxide, and palladium and / or rhodium as catalytically active metals in a wet process. The coating was applied to the porous filter wall over 80% of the substrate length. The total filter loading was 50 g / L, with a total precious metal loading of 1.33 g / L and a palladium to rhodium ratio of 3.75:1. The resulting coated filter was dried and then calcined. It is referred to below as VGPF2.

[0065] Comparative example 3: First, application of filtration-enhancing powder, then coating with a catalytically active layer into the porous wall of the flow-through filter substrate.

[0066] The surfaces O E A commercially available flow-through filter substrate was treated with a filtration-enhancing powder and then thermally treated. The total loading of the filter with the filtration-enhancing powder was 12 g / L. The surface area O ASubsequently, as described in the literature, the substrates were coated in a wet process with a catalytically active layer containing an oxygen storage component, lanthanum oxide-stabilized aluminum oxide, and platinum and / or rhodium as catalytically active metals. The coating was applied to over 80% of the substrate length within the porous filter wall. The total loading of the filter was 10 g / L, with a total precious metal loading of 0.11 g / L and a platinum-to-rhodium ratio of 12:1. The resulting coated filter was dried and then calcined. It is referred to below as VGPF3. Example 1: First coating with a catalytically active layer, then application of filtration-enhancing powder

[0067] The surfaces O AAs described in the literature, the porous filter wall was coated in a wet process with a catalytically active layer containing an oxygen storage component, lanthanum oxide-stabilized aluminum oxide, and palladium and / or rhodium as catalytically active metals. The coating was applied to over 80% of the substrate length. The total loading of the filter was 62.5 g / L, with a total precious metal loading of 1.67 g / L and a palladium-to-rhodium ratio of 3.75:1. The resulting coated filter was dried and then calcined. The surface O E The resulting calcined filter was treated with a filtration-enhancing powder and then thermally treated. The total loading of the filter with the filtration-enhancing powder was 21 g / L. The resulting filter is referred to below as GPF1. Example 2: First coating with a catalytically active layer, then application of filtration-enhancing powder

[0068] The surfaces O A As described in the literature, the porous filter wall was coated in a wet process with a catalytically active layer containing an oxygen storage component, lanthanum oxide-stabilized aluminum oxide, and palladium and / or rhodium as catalytically active metals. The coating was applied to over 80% of the substrate length. The total loading of the filter was 62.5 g / L, with a total precious metal loading of 1.67 g / L and a palladium-to-rhodium ratio of 3.75:1. The resulting coated filter was dried and then calcined. The surface O EThe resulting calcined filter was treated with a filtration-enhancing powder and then thermally treated. The total loading of the filter with the filtration-enhancing powder was 3 g / L. The resulting filter is referred to below as GPF2. Example 3: Coating with a catalytically active layer into the porous wall of the flow-through filter substrate and subsequent application of filtration-enhancing powder

[0069] The surfaces O AA commercially available flow-through filter substrate was coated, as described in the literature, with a catalytically active layer containing an oxygen storage component, lanthanum oxide-stabilized aluminum oxide, and platinum and / or rhodium as catalytically active metals in a wet process. The coating was applied to over 80% of the substrate length into the porous filter wall. The total filter loading was 10 g / L, with a total precious metal loading of 0.11 g / L and a platinum-to-rhodium ratio of 12:1. The resulting coated filter was dried and then calcined. Subsequently, the surfaces were O E The filter was loaded with a filtration-enhancing powder and then thermally treated. The total loading of the filter with the filtration-enhancing powder was 12 g / L. The resulting filter is referred to below as GPF3. Testing of filtration efficiency and exhaust back pressure

[0070] The two filters obtained in this way were then measured on a cold blow test rig to determine the pressure loss across each filter ( Fig. 3) At room temperature and a volume flow rate of 600 m³ / h 3 / h of air results in a back pressure of VGPF1 of 36.8 mbar, of VGPF 2 of 58.8 mbar, of VGPF3 of 10.9 mbar, of GPF1 of 32.1 mbar, of GPF2 of 51.2 mbar and of GPF3 of 9.5 mbar.

[0071] In parallel, fresh filters VGPF1, VGPF2, VGPF3, GPF1, GPF2, and GPF3 were investigated with regard to their particle filtration efficiency. For this purpose, the filters were measured between two particle counters. The filters according to the invention, GPF1, GPF2, and GPF3, exhibit a filtration efficiency of 91.7% (GPF1), 96.7% (GPF2), and 91.5% (GPF3), calculated from the particle values ​​of the two particle counters, while the comparison filters only achieved a filtration efficiency of 79.5% (VGPF1), 94.4% (VGPF2), and 88.1% (VGPF3). Test of the water stability of the powder according to the invention

[0072] In this embodiment, a ground, commercially available high-melting-point aluminum oxide (d50: 2.0 µm) is coated with 100 wt% organic silicone resin binder Silres 603 (Wacker Chemie AG). For this purpose, the silicone resin is dissolved in acetone as a solvent, the aluminum oxide is added, and the aluminum oxide is coated with the silicone resin by evaporating the solvent.

[0073] To test the water stability of the powder according to the invention, it is applied to a plate of commercially available monolithic porous cordierite and thermally treated in a convection oven at 550 °C for 2 hours. After cooling, the plate is examined under a microscope for open pores (dark spots), then held under running water for 20 seconds and subsequently dried at 120 °C for 30 minutes. The dried plate is examined again under a microscope for open pores. If no pores are open after treatment with water, the powder is considered water-stable.

[0074] In summary, it is evident that the production of a filter by coating it with a catalytically active layer and subsequently applying filtration-enhancing powder is particularly advantageous with regard to filtration efficiency and back pressure, in contrast to applying filtration-enhancing powder or using a commercially available flow-through filter substrate with a filtration-enhancing membrane and subsequently applying a catalytically active layer. Fig. 3).

[0075] In addition to the advantages described above, a silicone resin-coated powder can be used in the inventive method to obtain a water-stable, filtration-enhancing powder coating. The filter according to the invention is therefore more stable and robust with respect to water originating from the combustion process. Fig. 4).

Claims

[1] A method for producing a catalytically active particulate filter comprising a wall flow filter substrate for reducing harmful components from the exhaust gas of internal combustion engines, wherein the wall flow filter substrate has a length L and channels E and A extending parallel between a first and a second end of the wall flow filter substrate, which are separated by porous walls and form surfaces OE and OA respectively, and wherein the channels E at the second end and the channels A at the first end are closed, characterized by , that In a first step, high-melting-point metal compound particles comprising a dry powder, coated with a silicone resin, are produced; the coating of the metal compound particles is carried out in such a way that the particles are brought together in a solvent suspension with the silicone resin and the solvent is subsequently evaporated, and in a second, separate step, the surfaces OE of the catalytically active filter are treated with a dry powder-gas aerosol; the powder from the first step is applied; and; In a third step, the filter and powder are heated to remove organic components from the filter. [2] Method according to claim 1, characterized by , that the high-melting-point metal compound particles are selected from the group consisting of aluminium oxide, zirconium dioxide, cerium oxide, yttrium oxide, mullite, tin oxide, silicon nitride, zeolite, titanium dioxide, silicon dioxide, aluminium titanate, silicon carbide, cordierites, nesosilicates, layered silicates, technical silicates, chain silicates, group silicates or mixtures thereof. [3] Method according to claim 1 or 2, characterized by , that the high-melting-point metal compound particles have a mean particle diameter of 0.1 µm - 20 µm (D50; Q3 distribution). [4] Method according to any one of claims 1-3, characterized by that the high-melting-point metal compound particles coated with a silicone resin are not aggregated or agglomerated together. [5] Method according to any one of the preceding claims, characterized by , that for the application of the metal compound particles a silicone resin is selected from the group consisting of alkyl- or aryl- or alkyl- and aryl-functionalized oligomers or polymeric silicone resins. [6] Method according to any one of the preceding claims, characterized by that the application of the silicone resin to the metal compound particles takes place in a spray dryer. [7] Method according to any one of the preceding claims, characterized by , that the powder-gas aerosol is sucked into the filter at a speed of 10 m / s - 50 m / s. [8] Catalytically active particle filter, manufactured according to one of the preceding claims. [9] Catalytically active particle filter according to claim 8, characterized by , that up to 50% of the total mass of the powder is located in the porous walls of the wall flow filter substrate. [10] Catalytically active particle filter according to claim 8 or 9, characterized by that the powder has a mass of up to 50 g / l, based on the volume of the wall flow filter substrate. [11] Catalytically active particle filter according to one of claims 8 to 10, characterized by that the powder does not form a continuous coating on the OE surfaces. [12] Catalytically active particle filter according to any one of the preceding claims 8-11, characterized by that the filter has a catalytically active zone over a length of 30% - 100% of the coatable length L of the filter. [13] System for cleaning exhaust gases from, in particular predominantly stoichiometrically operated, internal combustion engines, comprising a catalytically active particulate filter of claims 9-12. [14] System according to claim 13, characterized by that the particulate filter may be located with its first end directly after a three-way or oxidation catalyst close to the engine. [15] System for cleaning exhaust gases according to claim 13 or 14, characterized by that at least one further catalyst, selected from the group of three-way catalyst, oxidation catalyst, NOx storage catalyst, hydrocarbon trap, SCR catalyst, ammonia slip catalyst, is located after the wall flow filter. [16] Method for exhaust gas purification of an internal combustion engine, in particular of a predominantly stoichiometrically operated internal combustion engine, in which the exhaust gases of the engine are passed through a particulate filter according to one of claims 9 – 12. [17] Method for exhaust gas purification of a predominantly stoichiometrically operated internal combustion engine, wherein the exhaust gases of the engine are routed via a system of claims 13 or 14.

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