DE102005063183A1 - Diesel particle filter e.g. soot separating filter, for motor vehicle, has porous and/or gas permeable channel walls with layers whose catalytic properties are different from each other - Google Patents

Abstract

The device for the treatment of combustion products, which are formed during engine combustion and flow through the device (1), has a particulate filter for particulate retention and catalytically active sections (9). In the throughflow direction, the combustion products pass an inflow side (6) and subsequently an outflow side (11). To increase the effectiveness and service life of the device, the catalytically active sections (9) comprise a first layer on the inflowing side (6) and a second layer on the outflow side (11), with the catalytic effects of the layers differing from each other.

Description

was standing of the technique

at The burning of fossil fuels, for example, can pollutants especially by incomplete Combustion are released. Treatment devices for combustion products can Remedy here. For example, exhaust gas aftertreatment exhaust filter or Used in catalytic converters, with which about 90% of Pollutants can be converted. For the Treatment of combustion products or exhaust gases from combustion Diesel fuels, for example, become diesel particulate filters used, which is a basic body of a ceramic material such as cordierite or silicon carbide exhibit. The exhaust gases overflow in the diesel particulate filter surfaces which are impregnated with a so-called washcoat, which as the carrier of catalytically active components of the exhaust treatment device serves.

Task of invention

task the invention is to provide a treatment device, with which a comparatively more effective treatment of combustion products possible is.

These The object is solved by claim 1.

epiphany the invention

The The invention is based on a device for the treatment of a Combustion of combustion products, e.g. Exhaust gases from diesel engines, which flow through the device, with a particle filter for a particle retention and catalytically active sections, wherein in the flow direction the combustion products an upstream side and then a Pass the inflow side. The core of the invention is that the catalytically active Sections a first layer on the upstream side and a second layer on the downstream side include, wherein the catalytic effects of the layers from each other differ. This allows targeted treatment of the combustion products or exhaust gases are improved or the proportion of catalytically treated be increased in the combustion products pollutants. In particular, you can incompletely oxidized gaseous fixed or particulate or liquid Exhaust components such as hydrocarbons (HC) or carbon monoxide (CO) completely or almost completely be oxidized to water or carbon dioxide. Through the two layers can each different catalytic reactions to different Side of the treatment device, such as a diesel particulate filter for diesel engines, supports become. The inflow side and the downstream side the treatment device or an exhaust particulate filter are in particular by a porous or gas-permeable Wall e.g. made of ceramic material separated from each other. The targeted catalytic effect of the respective layer becomes, for example by selecting or proportions of the catalyst components present in the layer certainly. In this case, the catalytically active component of a Catalyst or from a mixture of several catalyst materials consist.

In A preferred embodiment of the subject invention is the formed first layer to catalytically oxidize particles. With a comparatively high filtering or degrading effect for e.g. exhaust particles can with the first layer especially an environmentally relevant particulate matter through Exhaust gases are counteracted. This allows legal requirements especially regarding Ensure exhaust emissions safely. In particular, those on the inflow Filtered exhaust particles such as soot targeted mined. It is It is advantageous if the exhaust or soot exclusively or almost exclusively on the upstream side filtered out and there at least partially oxidized, because then can the resulting possibly not completely oxidized degradation products especially downstream within a subsequent Oxidized further section in the exhaust treatment device to the highest oxidation state become. Among particles or exhaust particles are in addition to soot particles especially all solid intermediates of the combustion of hydrocarbons, e.g. diesel fuel, to understand, for example, with attached to it harmful to health Hydrocarbons, e.g. polycyclic hydrocarbons.

In an advantageous embodiment of the subject invention, the second layer is constructed and adapted to the second layer, catalytically treated on the upstream side in the catalytic at least partial oxidation of the particulate combustion products formed substances and / or substances that pass the inflow side without catalytic treatment. The second layer can in particular be oriented for the catalysis of lower hydrocarbons or carbon monoxide or of substances which have formed during the catalysis by means of the first layer. In this case, for example, the first layer is preferably matched to the catalysis of higher hydrocarbons or to be degraded over several degradation stages substances. In particular, the layers can catalytically support in a targeted manner the expected degradation reactions of the combustion products that occur one after the other in the treatment device. Thus, preference may also be given to those in the first layer in the case of incomplete degradation of, for example, exhaust gas pollutants resulting intermediates, which may also have a pollutant potential, be catalytically further oxidized by the second layer to the fully oxidized products.

Further It is proposed that the first layer comprise a plurality of fiber elements includes. Fiber elements, in particular on the upstream side, e.g. of exhaust particulate filters the retention capacity for exhaust gas or soot particles across from fiber-free areas. Through the fiber elements in the first layer can almost all Particles of the combustion products or the exhaust gas filtered out on the upstream side or treated. In particular, can be comparatively by the fiber elements size for the Particles in an exhaust gas for adhesion suitable surfaces with realize relatively little fiber material. Is particularly advantageous while a comparatively small increase in the pressure loss during Flow through the treatment device. With the fiber elements can also have a Buffering property are provided. Because of the multitude For example, the fibers become a protective layer for the underlying lying carrier body for Example made of ceramic. The fibers act as if they were one heat-insulating carpet on the opposite if necessary Temperature peaks sensitive carrier body. The temperature peaks can e.g. through the soot burn arise on the fibers.

Especially It is advantageous if the fiber elements high-temperature resistant fibers include. With the temperature resistant Fibers of e.g. Alumina can the service lives of, for example, an exhaust gas or diesel particulate filter are increased, since the temperatures in the exhaust gas are usually several hundred degrees. In principle, in addition to aluminum oxide, other high temperature resistant materials for the Fibers conceivable.

Especially Preferably, the fiber elements of the first layer with a on the treatment of particulate Combustion products tuned catalytically active coating Mistake. Thus, the filterability of the first layer with regard to particles of the combustion products can be further increased.

Prefers For example, the coating of fiber elements includes soot oxidation catalyzing components. In particular, can be catalytically in the coating active substances are introduced, with which targeted an effective Degradation of the surfaces of the Carbon fiber particles adhering to fiber elements promoted becomes, if sooty Exhaust gases are treated. soot make e.g. the most significant component of the harmful exhaust particles at one Diesel combustion dar.

at a particularly advantageous embodiment of the subject invention For example, the coating of the fiber elements has at least one of the catalyst substances Cerium, iron and vanadium. In particular, come cerium, iron or Vanadium or mixtures of these components as catalyst materials in question. With these components in particular targeted the Rußabbrandtemperatur lowered, at which a Rußverbrennung can take place. In particular, the cold start behavior of diesel particulate filters for motor vehicles is thus significantly improved. Because the vast majority of unwanted Total emissions from vehicle exhaust gases are created in the first few minutes after the start of the engine combustion, because the temperatures the surfaces coming into contact with exhaust gas in the diesel particulate filter for one maximum catalytic activity not yet high enough. Because the conversion rate or the transformation into complete oxidized products by catalytically active substances is temperature-dependent, in particular is the Katalysatoranspringtemperatur about 250 to 300 degrees Celsius. As a further significant advantage of the catalyst materials mentioned is their property to name that the temperature peaks during occurring burning of soot particles is comparatively lower or damped. This is particularly gentle adjacent components and materials, for example a possibly underlying carrier made of ceramic material. The fiber elements can in particular with a Suspension, for example, as washcoat e.g. by dipping or Soak the ceramic support framework coated become.

Finally will further suggested that the second layer at least one of Catalysts platinum and palladium has. The second layer is thereby having a comparatively high catalytic activity for oxidation processes of gaseous Exhaust gas components formed. In particular, not completely oxidized Fuel or diesel components in the gas such as hydrocarbons or carbon monoxide are thus largely catalytically oxidized, ideally to carbon dioxide and water. This measure will targeted the diesel oxidation catalysis Strengthened (DOC). In addition to the listed Catalysts are also conceivable others, e.g. Rhodium or others.

In principle, a denitrification (DeNO _x ) function can be integrated with the proposed exhaust gas treatment device, for example in the first or second layer, or exhaust gas recirculation can be provided.

description of the embodiment

An embodiment of the invention is based on the following highly schematic Fi gures, stating further advantages and details.

1 shows very schematically a diesel particulate filter in perspective view and

2 a longitudinal section of in 1 shown diesel particulate filter in partial view.

1 shows a diesel particulate filter open on the inflow side 1 As Rußabbrennfilter which, for example, a metallic tubular shell 2 has, for example, which is flowed through a not shown exhaust pipe from a particulate exhaust gas according to the arrow P1. In a flow cross section 3 at the front end of the diesel particulate filter are alternately grid-like arranged in cross section in approximately square channel openings 4 and end faces of stopper 5 arranged for example of ceramic material. An optionally provided insulation of the interior of the shell 2 is in 2 not shown. The upstream channel openings 4 belong to longitudinal in the diesel particulate filter 1 parallel to each other in cross-section square channels 6 , which at an outflow cross section 7 (covered) by further stopper 8th closed gas-tight at the end.

A longitudinal section through the diesel particulate filter 1 in partial view is off 2 to take very simplified. This also shows the direction of flow through the diesel particulate filter for the exhaust gas to be treated. According to the arrows P1, the exhaust gas flows through the channel openings 4 into the channels 6 and occurs as it flows through the channels 6 through porous or gas-permeable channel walls 9 , where particulate matter such as exhaust or soot particles 10 on an inner wall of the channels 6 be held back. The exhaust gases pass through the passage walls after passing through 9 from the channels 6 in downstream channels 11 , Theoretically possible flow paths of the exhaust gas are indicated by arrows within the section 2 indicated. The downstream channels 11 are also substantially square in cross section adjacent to the channels 6 and with these to a channel bundle inside the shell 2 educated. At the outlet cross section 7 come in the diesel particulate filter 1 treated gas components or their treatment products from the diesel particulate filter 1 according to the arrows P2.

The inner walls of the channels 6 preferably have a layer of heat-resistant fibers, not shown, in particular of aluminum oxide. The fibers on the inner wall of the channels 6 can also be coated with a coating with catalytically active substances, which includes, for example, in addition to platinum and palladium in particular cerium, iron and vanadium.

The inner walls of the downstream channels 11 are in particular provided with a catalytically active coating, which comprises, for example, platinum and palladium, through which the partially oxidized components present in the exhaust gas are further oxidized or the diesel oxidation catalysis takes place. The largely purified or filtered exhaust gas with the oxidized components leaves the diesel particulate filter according to arrow P2 1 ,

Claims (9)

Device for the treatment of combustion products produced by combustion, comprising the device ( 1 ), with a particle filter for particle retention and catalytically active sections ( 9 ), wherein in the flow direction, the combustion products an upstream side ( 6 ) and then a downstream side ( 11 ), characterized in that the catalytically active portions ( 9 ) a first layer on the upstream side ( 6 ) and a second layer on the downstream side ( 11 ), wherein the catalytic effects of the layers differ from each other. Device according to claim 1, characterized in that that the first layer is formed, particulate combustion products catalytically at least partially oxidize. Apparatus according to claim 1 or 2, characterized in that the second layer is constructed and tuned to the first layer, on the upstream side ( 6 ) in the catalytic at least partial oxidation of the particulate combustion products formed substances and / or substances which the inflow side ( 6 ) pass without catalytic treatment, to catalytically treat. Device according to one of the preceding claims, characterized characterized in that the first layer comprises a plurality of fiber elements includes. Device according to one of the preceding claims, characterized characterized in that the fiber elements high temperature resistant fibers include. Device according to one of the preceding claims, characterized characterized in that the fiber elements of the first layer with a on the treatment of particulate Combustion products tuned catalytically active coating are provided. Device according to one of the preceding claims, characterized characterized in that the coating of the fiber elements is a soot oxidation catalyzing constituents. Device according to one of the preceding claims, characterized characterized in that the coating of the fiber elements at least one of the catalyst materials cerium, iron and vanadium. Device according to one of the preceding claims, characterized in that the second layer comprises at least one of the catalyst substances Platinum and palladium.