DE102018009233A1 - Exhaust after-treatment device for a motor vehicle with a catalytic converter, which has at least one SCR material and at least one NOx storage material, and method for operating such an exhaust gas aftertreatment device - Google Patents

Abstract

The invention relates to an exhaust gas aftertreatment device (10) for a motor vehicle, comprising at least one catalytic converter (18) through which exhaust gas from an internal combustion engine (12) of the motor vehicle flows, which catalyst comprises at least one SCR material for catalyzing a selective catalytic reduction for reducing nitrogen oxides contained in the exhaust gas at least one NO _x storage material for at least temporarily storing nitrogen oxides contained in the exhaust gas, and with an upstream of the catalyst (18) arranged feed device (24), by means of which a reducing agent, by means of which in the exhaust gas contained nitrogen oxides in the selective catalytic reduction are reducible, can be introduced into the exhaust gas, wherein the catalyst (18) is free of platinum metals.

Description

The invention relates to an exhaust aftertreatment device for a motor vehicle, in particular for a motor vehicle. Furthermore, the invention relates to a method for operating such an exhaust gas aftertreatment device. The invention also relates to a motor vehicle, in particular a motor vehicle, with at least one such Abg as a treatment device.

From the publication "A PGM-free NO _x adsorber + selective catalytic reduction catalyst system (AdSCR) for trapping and reducing NO _x in lean exhaust streams at low temperature", Tommaso Selleri et al., Catalysis Science & Technology, 2018, 8, No. 2467-2476, a so-called AdSCR catalytic converter is known, which can be flowed through by exhaust gas of an internal combustion engine and can store nitrogen oxides contained in the exhaust gas. In addition, the AdSCR may catalyze selective catalytic reduction (SCR) to reduce nitrogen oxides contained in the exhaust and / or stored in the coating of the AdSCR. In addition, the AdSCR catalyst is free of precious metals, in particular platinum metals (PGM - platinum group metals).

Object of the present invention is to provide an exhaust aftertreatment device, a method and a motor vehicle, so that exhaust gas of an internal combustion engine can be aftertreated particularly advantageous, especially in the low temperature range from room temperature.

This object is achieved by an exhaust aftertreatment device having the features of patent claim 1, by a method having the features of patent claim 10. Advantageous embodiments with expedient developments of the invention are specified in the remaining claims.

A first aspect of the invention relates to an exhaust aftertreatment device for a motor vehicle, for example for a motor vehicle designed as a passenger car or commercial vehicle. This means that the motor vehicle in its completely manufactured state comprises the exhaust aftertreatment device. In addition, the motor vehicle in its completely manufactured state, for example, designed as a reciprocating engine internal combustion engine, by means of which the motor vehicle can be driven. In this case, the exhaust gas aftertreatment device has at least or exactly one catalyst which can be flowed through by exhaust gas of the internal combustion engine and which has various chemically and / or physically active materials, in particular chemically and / or physically active coating materials. The catalyst comprises at least or precisely one SCR material, in particular SCR coating material for catalysing a selective catalytic reduction (SCR - selective catalytic reduction) for reducing nitrogen oxides (NO _x ). In the case of an embodiment as a coating, the SCR material is also referred to as the first coating material. In addition, the catalyst comprises at least or exactly one NO _x storage material, in particular NO _x storage coating material, for the at least temporary storage of nitrogen oxides contained in the exhaust gas. In other words, the catalyst has an NO _x storage function, in particular a so-called nitrogen oxide storage catalyst (NSK) or a passive NO _x adsorber (PNA). The NO _x storage coating material is also referred to as a storage material or, in the case of an embodiment as a coating, as a second coating material. The coating materials (SCR coating material and NO _x storage coating material) are for example part of a physical or chemical mixture or the coating materials form a physical or chemical mixture. In other words, for example, the coating of the catalyst is formed from a physical or chemical mixture of the coating materials. In the context of the invention, the SCR coating material and the NOx storage coating material can also be arranged as superimposed layers in a two-layered or multi-layered form, or as at least two coating zones arranged successively in the axial flow direction of the exhaust gas through the catalyst. In the context of the invention, it is also conceivable that the catalyst is prepared as a bulk extrudate of a physical mixture of an SCR catalyst material and a NO _x storage material, so that a catalyst prepared in this way a NO _x storage function and an SCR catalytic function However, these two functions are not shown with a coating of a catalyst body. Since the catalyst storing nitrogen oxides contained in the exhaust gas and the selective catalytic reduction (SCR) for the reduction of nitrogen oxides contained in the exhaust catalyze, that catalytically support or can cause, the catalyst is also referred to as AdSCR catalyst or simply as AdSCR. In the context of the invention, the carrier body of the catalyst may be formed as a flow-through substrate or as a filter substrate.

Furthermore, the exhaust aftertreatment device according to the invention comprises at least one addition device, by means of which at least one, in particular liquid or gaseous, reducing agent, by means of which and / or in the AdSCR Stored nitrogen oxides are reducible in the selective catalytic reduction, can be introduced into the exhaust gas. In other words, at least one reducing agent can be introduced into the exhaust gas by means of which in the course of the AdSCR catalyzable SCR contained in the exhaust and / or stored in the AdSCR nitrogen oxides reducible, that is at least partially removable from the exhaust gas. For this purpose, the at least one reducing agent and / or a substance resulting from the at least one reducing agent in the course of the SCR on the SCR coating material with nitrogen oxides contained in the exhaust gas and / or stored in the NOx storage coating material to substantially water and nitrogen. By the feature that the at least one feed device is arranged upstream of the AdSCR, it is to be understood in particular that the feed device can introduce the reducing agent into the exhaust gas at at least or exactly one feed point arranged upstream of the AdSCR.

The coating or its composition is already known, for example, from the publication "A PGM-free NO _x adsorber + selective catalytic reduction catalyst system (AdSCR) for trapping and reducing NO _x in lean exhaust streams at low temperature", Tommaso Selleri, et al. Catalysis Science & Technology, 2018, 8, 2467-2476 ", so that, for example, the respective coating materials are known from the abovementioned publication and can be taken from the same formed for example as a diesel engine, the internal combustion engine can be ensured. in particular, can particularly advantageously by means of the exhaust gas treatment device according to the invention a so-called nitrogen oxide NO _x breakthrough way relationship at or after a cold start and / or during a Abbr hlphase the internal combustion engine can be avoided. In other words, by means of the exhaust gas aftertreatment device according to the invention, it is possible with particular advantage to avoid excessive nitrogen oxide emissions of the internal combustion engine during or after its cold start and / or during a cooling phase. It has been found, surprisingly, that nitrogen oxides contained in the catalytic converter are stored in the catalytic converter at temperatures above room temperature or even lower in the catalytic converter, and the nitrogen oxides are at least already in part not only at temperatures above about 50 degrees Celsius be stored in the catalyst, but already converted to mainly nitrogen.

In one embodiment of the invention, the catalyst is free of oxidation-catalytically active noble metal-containing coating materials. In contrast to conventional nitrogen oxide storage catalysts, which always have a noble metal coating or at least one or more precious metals, in particular platinum metals, platinum metal coating for the oxidation of nitrogen oxides contained in the exhaust gas is provided in this embodiment of the exhaust aftertreatment device according to the invention that the AdSCR (catalyst ) is in particular free of oxidation-catalytically active platinum metals. In other words, it dispenses with a noble metal-containing coating of the AdSCR, which has an oxidation function. Thus, the catalyst advantageously has no or only low oxidation functionality of NH ₃ in the conventional temperature operating range of exhaust aftertreatment devices of up to 600 degrees Celsius.

It has proven to be particularly advantageous if the catalyst (AdSCR) is arranged in a first block of exhaust gas after-treatment elements in the flow direction of the exhaust gas after the exhaust gases have left the internal combustion engine. In this case, a first block of exhaust-gas aftertreatment elements is to be understood as meaning, in particular, a first exhaust aftertreatment element complex or a first accumulation of exhaust-gas aftertreatment elements, which are integrated, for example, in a common box for accommodating exhaust-gas aftertreatment elements. In particular, the feature that the AdSCR is arranged in a first block of exhaust aftertreatment elements in the direction of flow of the exhaust gas after exit of the exhaust gases from the internal combustion engine to understand that the AdSCR is not disposed on or in an underbody of the motor vehicle whose underbody, for example by the Structure is formed. Advantageously, during operation of the exhaust aftertreatment device according to the invention of this embodiment, a temperature in the AdSCR Rohabgastemperatur at the outlet of the internal combustion engine with comparatively little time delay, so that the AdSCR in cooling phases of the internal combustion engine comparatively quickly, ie with relatively little time delay, cools and in heating phases of the internal combustion engine The AdSCR heats up quickly. As a result, an operation, the exhaust gas aftertreatment device according to the invention, in particular a point in time and a quantity of reducing agent to be metered in, can be advantageously regulated in this embodiment of the invention.

In an advantageous embodiment of the invention, the exhaust gas aftertreatment device has at least or exactly one oxidation catalyst, which is preferably formed as a diesel oxidation catalyst (DOC). The oxidation catalyst, in particular its oxidation coating, is at a distance from the coating of the AdSCR, in particular from the AdSCR as a whole, in particular arranged upstream of the AdSCR in the flow direction of the exhaust gas. It is also conceivable that the oxidation catalyst is formed as a coating of a diesel particulate filter in the exhaust gas aftertreatment device according to the invention. Such a trained diesel particulate filter is also called cDPF. In contrast to the AdSCR, which has only an oxidation functionality for NO, the oxidation catalyst moreover has in particular an oxidation functionality for hydrocarbons, carbon monoxide and hydrogen. This is understood to mean that the oxidation catalyst is not only used to catalyze an oxidation of nitrogen oxides contained in the exhaust gas, in particular nitrogen monoxide contained in the exhaust gas, but in particular for catalyzing an oxidation of unburned hydrocarbons contained in the exhaust gas and / or for the oxidation of formed in the exhaust gas carbon monoxide (CO) is formed. As a result, a particularly advantageous exhaust aftertreatment can be ensured. In a particularly advantageous embodiment of the invention, the oxidation catalyst is arranged upstream of the feed device or upstream of the introduction point. As a result, undesired impairments of the oxidation catalyst by the reducing agent can be avoided and / or undesired effects of the reducing agent by the oxidation catalyst can be avoided.

In particular, it is provided in one embodiment of the invention that the at least one reducing agent can form ammonia and is thus adapted to provide ammonia. This is to be understood in particular that the reducing agent initially has a different substance from pure ammonia, which, for example, after its introduction into the exhaust gas to ammonia decomposes or, in particular pure, ammonia (NH ₃ ) reacts. As a result, a particularly advantageous exhaust aftertreatment can be ensured. The reducing agent is preferably designed such that gaseous ammonia (NH ₃ ) is formed from the reducing agent already at a temperature of the exhaust gas in the catalyst of less than at least about 100 degrees Celsius, advantageously already less than about 50 degrees Celsius, and that in particular at the latest on or in the entry section of the AdSCR. The gaseous, ammonia can react in the context of the SCR and thereby in the AdSCR with nitrogen oxides contained in the exhaust gas and / or stored in the AdSCR to substantially nitrogen and water, whereby the exhaust gas is de-embroidered. In this case, the reducing agent per se, in particular pure, comprise ammonia and / or be formed forming ammonia. In particular, it is conceivable that the reducing agent is initially liquid and can be introduced into the exhaust gas in the liquid state or is introduced. During or after the introduction of the liquid reducing agent into the exhaust gas, for example, the initially liquid reducing agent evaporates, so that gaseous, in particular pure, ammonia is formed from the reducing agent.

The reducing agent may be formed in one embodiment of the invention as, in particular aqueous, urea solution. Aqueous urea solutions are advantageously inexpensive and can also be stored inexpensively in a liquid tank.

In a further embodiment of the invention, the at least one reducing agent comprises at least ammonia, wherein the ammonia can be introduced into the exhaust gas in a gaseous state from the feed device. In other words, in this embodiment of the invention, a reducing agent is introduced into the exhaust gas, which already comprises gaseous ammonia, so that advantageous in this embodiment of the invention even at low exhaust gas temperatures, such as during or after a cold start of the internal combustion engine and / or during cooling phases, the reducing agent can be added to the exhaust gas. Thus, with this embodiment of the invention, the special property of the AdSCR found by the inventors can be utilized that a conversion of nitrogen oxides stored in the AdSCR or stored in the exhaust gas or stored in the AdSCR already at 50 degrees Celsius, or even at even lower temperatures Catalyst takes place if a reducing agent is available. The fact that the at least one reducing agent comprises at least ammonia in the context of the invention means in particular that the reducing agent is a component of the exhaust gas aftertreatment device according to the invention, wherein the reducing agent comprises ammonia (NH 3) per se. This means that the reducing agent does not or not only have a component which, in particular in hot exhaust gas, reacts or is converted to ammonia (NH 3), but the reducing agent already has ammonia (NH 3) before it is introduced into the exhaust gas. In this case, the reducing agent can be formed as ammonia and stored for example as a solid in cartridges in the motor vehicle. The reducing agent may also be formed forming ammonia. It is conceivable that the reducing agent is initially liquid and is evaporated before being introduced into the exhaust gas.

In a further embodiment of the invention, at least one further reducing agent, by means of which nitrogen oxides contained in the exhaust gas can be reduced in the selective catalytic reduction, can be introduced into the exhaust gas from a further feed device arranged upstream of the catalyst, wherein the further reducing agent comprises at least ammonia which can be introduced into the waste gas in the gaseous state from the further feed device. Advantageously, with this embodiment of the invention, in particular aqueous urea solution can be introduced as a reducing agent in the exhaust gas and gaseous ammonia as the further reducing agent, so that advantageously a metered addition of gaseous ammonia can be limited to the operating conditions at low exhaust gas temperatures and so on in the motor vehicle to be stored ammonia can be kept small.

In a further embodiment of the invention, it is provided that the exhaust aftertreatment device has at least or exactly one downstream of the AdSCR and from the coating of the AdSCR, in particular of the AdSCR total, spaced and provided in addition to the AdSCR provided SCR catalyst. As a result, excessive nitrogen oxide emissions can be avoided particularly reliably. The SCR catalyst may be formed as a through substrate or as a filter unit.

Furthermore, it has proven to be particularly advantageous if the exhaust-gas aftertreatment device has at least or exactly one particle filter arranged downstream or upstream of the AdSCR, in particular diesel particle filter. As a result, excessive particulate emissions can be avoided.

In order to ensure a particularly low-emission operation, it is provided in a further embodiment of the invention that the particle filter has a coating for catalysis of the selective catalytic reduction. Thus, the particulate filter, in particular when designed as a diesel particulate filter (DPF), is preferably designed as a SCF-coated diesel particulate filter (SDPF).

A second aspect of the invention relates to a method for operating an exhaust gas aftertreatment device of a motor vehicle having at least one exhaust gas of an internal combustion engine, which has a coating comprising at least one SCR coating material for catalyzing a selective catalytic reduction for reducing nitrogen oxides contained in the exhaust gas and at least a NO _x storage coating material for at least temporarily storing nitrogen oxides contained in the exhaust gas, and with at least one upstream of the catalyst arranged addition means by which at least one reducing agent, by means of which contained in the exhaust gas nitrogen oxides are reduced in the selective catalytic reduction, in the Exhaust gas can be introduced, in which ver on a regular implementation of regeneration phases of the NO _x storage coating material in a rich operation of the internal combustion engine ver is canceled. In the method according to the invention, regular regeneration phases in which the nitrogen oxides stored in the catalyst (AdSCR) are at least partially dispensed from the catalyst (AdSCR), in particular from the NO _x storage coating material of the catalyst (AdSCR), in a rich operation of the internal combustion engine In other words, in the method according to the invention, a regular execution of rich operating phases of the internal combustion engine at substoichiometric air-fuel ratios of the air-fuel mixture, for a withdrawal or desorption of nitrogen oxides from the NO _x storage coating material of the AdSCR is dispensed with. In nitrogen oxide storage catalysts, ie catalysts with nitrogen oxide storage material, from the prior art, the storage phases for nitrogen oxides (lean operation of the internal combustion engine) usually take about 100 seconds to about 2 to 3 minutes, wherein a duration of the storage phases of a storage capacity of the nitrogen oxide storage catalyst and the concentration the nitrogen oxides in the exhaust gas depends. However, for aged nitrogen oxide storage catalysts of reduced storage capacity, the duration of the storage phase may also decrease to 50 seconds or less. After a storage phase for nitrogen oxides is thus regularly in the known from the prior art catalysts with nitrogen oxide storage material in each case the implementation of a regeneration phase required to reduce or desorb the nitrogen oxides stored in the nitrogen oxide storage catalyst. Accordingly, in catalysts with prior art nitrogen oxide storage material, it is usually necessary to perform a regeneration phase at least every 50 seconds at the latest, to about every 2 to 3 minutes at the latest. For a regeneration of a prior art nitrogen oxide storage catalyst in which the desorbed nitrogen oxides are simultaneously reduced to nitrogen, rich operation of the internal combustion engine during the regeneration phase is required to recover the desorbed nitrogen oxides with the reducing agent products from the rich and thus incomplete combustion, such as hydrocarbons, carbon monoxide and hydrogen, to reduce nitrogen. With the method according to the invention and the exhaust gas aftertreatment device according to the invention, a fuel consumption of the motor vehicle can be reduced particularly advantageously, since Periodic with a fuel consumption associated rich mixture settings for the internal combustion engine for regeneration of the NOx storage material of the catalytic converter (AdSCR) can be omitted.

In one embodiment of the method for operating the exhaust aftertreatment device according to the invention, in a period of time for which the at least one addition device is activated, a metered amount of introduced reducing agent is raised regularly to a metered amount which is higher than a metered amount of reducing agent, which substantially for the reduction all of the nitrogen oxides contained in the exhaust gas upstream of the catalyst is necessary, wherein the reducing agent is introduced in particular as a liquid from the feed device into the exhaust gas, wherein the liquid is in particular formed as an aqueous urea solution. For this purpose, in the present method in a period of time for which the addition device is activated, a metered amount of introduced reducing agent regularly so dimensioned that this particular at least regularly after each end of a cooling phase of the internal combustion engine is raised to a Dosiermenge which is higher than a first Dosierschwellwert is, wherein the first Dosierschwellwert is a metered amount of reducing agent, which is necessary for the reduction of substantially all of the nitrogen oxides contained in the exhaust stream upstream of the catalyst. In the present method, it is preferably provided that, in particular for a regeneration of the AdSCR, the reducing agent, in particular as a function of an AdSCR fill level with nitrogen oxides, is regularly overdosed. The AdSCR level is understood to mean a quantity of nitrogen oxides stored in the AdSCR. In other words, the AdSCR level characterizes a quantity of nitrogen oxides stored in the AdSCR, so that, for example, for the regeneration of the AdSCR, the reducing agent is introduced, in particular overdosed, by means of the addition device as a function of an amount of nitrogen oxides stored in the AdSCR. Thus, with the present further method, it is advantageously effected that the AdSCR is not regenerated by specially provided regeneration phases in rich internal combustion engine combustion, but the AdSCR generally regenerates itself advantageously, since the SCRs in the AdSCR react freely with the NOx storage coating material can, that is rid of nitrogen oxides. In particular, it is proposed that if a temperature window is present, for which a dosage of, in particular as aqueous urea solution formed, reducing agent is possible, ie usually at temperatures of the exhaust aftertreatment device of about 150 degrees Celsius, the feed device for a predeterminable or predetermined period of time operated such that an introduced by means of the feed device into the exhaust or introduced amount of the reducing agent is slightly raised and thus overdosed.

In one embodiment of the method according to the invention for operating the exhaust gas aftertreatment device according to the invention, it is provided that introduction of the reducing agent into the exhaust gas by means of the at least one feed device is already started from or at a temperature of the exhaust gas in the catalytic converter (AdSCR) of less than 100 degrees Celsius, preferably even for temperatures of the exhaust gas of less than 50 degrees Celsius, is activated. Thus, it is preferably provided that by means of the at least one feed device, the reducing agent is introduced into the exhaust gas already from or at a temperature of the exhaust gas in the catalyst of less than 100 degrees Celsius, in particular less than 50 degrees Celsius. In this case, the at least one reducing agent, which can be introduced into the exhaust gas via the at least one feed device, advantageously comprises at least ammonia which can be introduced by the feed device into the gaseous state. Ammonia is already at ambient pressure from a temperature of about - 33 degrees Celsius gaseous. If, for example, ammonia is stored as a reducing agent in the motor vehicle, then there is a reducing agent which can be supplied to the catalyst in a gaseous state in a temperature range of the exhaust gas in and upstream of the catalytic converter (AdSCR).

The invention is based in particular on the following findings: Surprisingly, it was found in a laboratory experiment that when the ammonia (NH ₃ ) preloaded AdSCR with nitrogen monoxide (NO) reacted with nitrogen in the AdSCR, even at or above 50 degrees Celsius , in some laboratory tests, even at temperatures less than 50 degrees Celsius, begins or expires. This was detected by measurements on the fact that nitrogen flowing out of the AdSCR (N ₂ ), which is in particular a reaction product of the SCR, has already increased at or above a temperature of the exhaust gas of approximately 50 degrees Celsius or even at an already lower temperature. This was because even at or above 50 degrees Celsius or even at lower temperatures, the exhaust gas could be de-embroidered by means of the AdSCR. In addition, a strong increase of nitrogen flowing out of the AdSCR from temperatures of the exhaust gas in the AdSCR of about 100 degrees Celsius was detected.

In one embodiment of the method according to the invention for operating the The exhaust aftertreatment device according to the invention is promptly before stopping the motor vehicle to increase a metered amount of reducing agent to a value which is higher than a second Dosierschwellwert, the second Dosierschwellwert is a Dosiermenge of reducing agent, which for the reduction of substantially all of the nitrogen oxides contained in the exhaust and is necessary to reduce substantially all stored on the NO _x storage coating material of the catalyst nitrogen oxides. Within the scope of the invention, a time interval of less than approximately 10 minutes, in particular a time interval of less than 5 minutes, is to be understood as meaning, for example, within the scope of the invention. The inventive method of this embodiment not only a regeneration of the NO _x storage coating material of the AdSCR before stopping the motor vehicle can be displayed, but also a pre-loading of the SCR coating material of the AdSCR can be effected with reducing agent, so that particularly advantageous in or after a cold start, when after a cold start the NO _x storage capacity of the NO _x storage coating material is soon exhausted, a reduction of the nitrogen oxides to nitrogen can take place in the AdSCR, which, as was found in laboratory experiments, already from a temperature of 50 degrees Celsius even less.

In one embodiment of the method according to the invention is carried out in particular in an electronic computing device of the motor vehicle, in particular regularly updated, determination and evaluation of forecast data to determine a period of time until arrival of the motor vehicle at the destination and the associated very likely parking the motor vehicle. An electronic computing device may in particular be an electronic computing device of the exhaust aftertreatment device or the internal combustion engine. The forecast data can in particular be read out of a navigation system of the motor vehicle or transmitted from it to the electronic computing device. The remaining distance to the destination can be determined, for example, by means of a route planned by means of a navigation system of the motor vehicle. For example, the route passes from a starting location to the destination so that the motor vehicle arrives at the destination as it is driven along the route. By means of the navigation system, for example, at least one current position of the motor vehicle on the earth is determined. By determining the current position of the motor vehicle and by determining or knowing the destination, a distance between the current position and the destination can be determined, this distance corresponding to the remaining distance, so that a remaining travel time can be determined to the destination. Finally, it has proven to be particularly advantageous if the method is carried out several times in succession during a drive of the motor vehicle. This means that it is not a one-off, for example, provided before the start of a journey and / or planning or optimization of a route, but the query values are constantly determined and the operating parameters are constantly determined and updated,

In one embodiment of the method according to the invention for operating the exhaust gas aftertreatment device according to the invention takes place before a cooling phase of the motor vehicle, an increase in a dosage of reducing agent to a value which is higher than a second Dosierschwellwert, wherein the second Dosierschwellwert is a Dosiermenge of reducing agent, which for the reduction of essentially all of the nitrogen oxides contained in the exhaust gas and for the reduction of substantially all nitrogen oxides stored on the NO _x storage coating material of the catalyst is necessary. In this embodiment of the method according to the invention, the electronic computing device of the motor vehicle undertakes a, in particular regularly updated, determination and evaluation of look-ahead data in order to determine a time duration until a next cooling phase of the internal combustion engine. Cooling phases of the internal combustion engine are in particular downhills, stoppage phases of the motor vehicle or low-load trips.

Advantages and advantageous embodiments of the first aspect of the invention are to be regarded as advantages and advantageous embodiments of the second aspect of the invention, and vice versa.

A third aspect of the invention relates to a motor vehicle, which is preferably designed as a motor vehicle, in particular as a passenger car. The motor vehicle according to the invention has an engine compartment which, for example, is delimited by a construction of the motor vehicle, which is designed in particular as a self-supporting body. In addition, the motor vehicle comprises an internal combustion engine arranged in the engine compartment, which is also referred to as engine or internal combustion engine. By means of the internal combustion engine, the motor vehicle is driven. In addition, the motor vehicle comprises an exhaust aftertreatment device, in particular an exhaust aftertreatment device according to the first aspect of the invention. The exhaust gas aftertreatment device has at least one catalytic converter (AdSCR) through which exhaust gas of the internal combustion engine can flow, which has a coating comprising at least one SCR coating material for catalysing a selective catalytic converter Reduction for reducing nitrogen oxides contained in the exhaust gas and at least one NO _x storage-coating material for at least temporarily storing nitrogen oxides contained in the exhaust gas. In addition, the exhaust gas aftertreatment device comprises an addition device arranged upstream of the catalyst, by means of which a reducing agent, by means of which nitrogen oxides contained in the exhaust gas can be reduced in the selective catalytic reduction, can be introduced into the exhaust gas. The catalyst is in particular free of oxidation-catalytically active platinum metals. Advantages and advantageous embodiments of the first aspect of the invention and the second aspect of the invention are to be regarded as advantages and advantageous embodiments of the third aspect of the invention and vice versa.

Further advantages, features and details of the invention will become apparent from the following description of preferred embodiments and from the drawing. The features and feature combinations mentioned above in the description as well as the features and feature combinations mentioned below in the description of the figures and / or in the figures alone can be used not only in the respectively specified combination but also in other combinations or in isolation, without the scope of To leave invention.

• 1 eine schematische Darstellung einer erfindungsgemäßen Abgasnachbehandlungseinrichtung gemäß einer ersten Ausführungsform;
• 2 eine schematische Darstellung der Abgasnachbehandlungseinrichtung gemäß einer zweiten Ausführungsform;
• 3 eine schematische Darstellung der Abgasnachbehandlungseinrichtung gemäß einer dritten Ausführungsform;
• 4 eine schematische Darstellung der Abgasnachbehandlungseinrichtung gemäß einer vierten Ausführungsform;
• 5 eine schematische Darstellung der Abgasnachbehandlungseinrichtung gemäß einer fünften Ausführungsform; und
• 6 eine schematische Darstellung der Abgasnachbehandlungseinrichtung gemäß einer sechsten Ausführungsform;
• 7 ein Diagramm zur Veranschaulichung eines Betriebs der Abgasnachbehandlungseinrichtung.

The drawing shows in:

• 1 a schematic representation of an exhaust aftertreatment device according to the invention according to a first embodiment;
• 2 a schematic representation of the exhaust gas aftertreatment device according to a second embodiment;
• 3 a schematic representation of the exhaust aftertreatment device according to a third embodiment;
• 4 a schematic representation of the exhaust gas aftertreatment device according to a fourth embodiment;
• 5 a schematic representation of the exhaust aftertreatment device according to a fifth embodiment; and
• 6 a schematic representation of the exhaust aftertreatment device according to a sixth embodiment;
• 7 a diagram illustrating an operation of the exhaust aftertreatment device.

In the figures, the same or functionally identical elements are provided with the same reference numerals.

1 shows a schematic representation of an exhaust aftertreatment device 10 for a motor vehicle. It shows 1 a first embodiment of the exhaust aftertreatment device 10 , The example of a motor vehicle, especially as a passenger car, trained motor vehicle has in its fully prepared state, the exhaust aftertreatment device 10 and an internal combustion engine also referred to as an engine or internal combustion engine 12 on, by means of which the motor vehicle can be driven. The internal combustion engine 12 has, for example, trained as a cylinder combustion chambers 14 in which during a fired operation of the internal combustion engine 12 Burning processes take place. This puts the internal combustion engine 12 during its fired operation exhaust ready, the exhaust aftertreatment device 10 from the exhaust gas of the internal combustion engine 12 can be flowed through. In 1 illustrates an arrow 16 the exhaust aftertreatment device 10 flowing exhaust gas.

In order to treat the exhaust particularly advantageous and thus a particularly low-emission operation of the internal combustion engine 12 To be able to realize includes the exhaust aftertreatment device 10 at least or exactly one catalyst also called AdSCR 18 which has an in 1 particularly schematically illustrated coating 20 having. The coating 20 comprises at least or precisely a first coating material and at least or exactly a second coating material. The first coating material is an SCR coating material for catalyzing a selective catalytic reduction (SCR) for reducing nitrogen oxides (NO _x ) contained in the exhaust gas. The second coating material is a storage material in the form of a NO _x storage coating material for at least temporarily storing nitrogen oxides contained in the exhaust gas. Furthermore, the coating 20 , in particular the catalyst 18 Total, free of oxidation-catalytically active noble metals or platinum metals, by means of which an oxidation of exhaust gas contained in the exhaust gas (HC) and / or ammonia contained in the exhaust gas (NH3) and / or contained in the exhaust gas carbon monoxide (CO) could be effected. In other words, though the coating 20 has a storage functionality with respect to the at least temporary storage of nitrogen oxides contained in the exhaust gas and thus can act like a nitrogen oxide storage catalyst (NSK, PNA), is the catalyst 18 free of oxidation-catalytically active precious or platinum metals.

The exhaust aftertreatment device 10 also includes one as well Metering device or metering module called feed device 24 , by means of which a preferably liquid reducing agent, by means of which contained in the exhaust gas nitrogen oxides in the course of the selective catalytic reduction, which in the catalyst 18 expires, are reducible, in the exhaust gas is introduced or introduced. Here is the addition device 24 in the flow direction of the exhaust aftertreatment device 10 flowing exhaust gas upstream of the catalyst 18 arranged. Because the catalyst 18 is free from oxidation-catalytically active noble or PGM or platinum metal-containing coatings, the reducing agent, which upstream of the catalyst 18 is introduced into the exhaust gas, not by the catalyst 18 , in particular its functionality, impaired. The exhaust aftertreatment device 10 also has exactly one oxidation catalyst 26 on which of the catalyst 18 spaced apart and in addition to the catalyst 18 is provided. In this case, the oxidation catalyst 26 upstream of the feed device 24 arranged. The oxidation catalyst, in contrast to the AdSCR, which has an oxidation functionality of NO to NO ₂ only with the SCR coating material, additionally has an effect of catalyzing oxidation of unburned hydrocarbons contained in the exhaust gas and / or carbon monoxide contained in the exhaust gas. The internal combustion engine 12 is in particular a diesel engine, so that the oxidation catalyst 26 preferably a diesel oxidation catalyst (DOC) is the catalyst 18 further allows storage of nitrogen oxides, also referred to as storage, even at very low temperatures, which are far below the so-called light-off temperature of the catalyst, also referred to as light-off temperature 18 especially with regard to the catalysis of SCR.

In the first embodiment, the exhaust aftertreatment device 10 exactly one downstream of the catalyst 18 arranged and in the present case designed as a diesel particulate filter (DPF) particulate filter 28 on, by means of which particles contained in the exhaust gas, in particular soot particles, can be filtered out of the exhaust gas. In addition, the exhaust aftertreatment device comprises 10 one downstream of the catalyst 18 and downstream of the particulate filter 28 arranged, in addition to the catalyst 18 provided and from the catalyst 18 , in particular of its coating 20 , spaced SCR catalyst 30 , which is designed to catalyze the SCR and therefore has a corresponding coating. To by means of the catalyst 18 Particularly advantageous to be able to store nitrogen oxides, the NO _x storage coating material preferably comprises at least barium (Ba) and / or cerium (cerium or Ce).

In the first embodiment, the exhaust aftertreatment device comprises 10 one downstream of the catalyst 18 and downstream of the SCR catalyst 30 arranged second SCR catalyst 32 , which is designed to catalyze the SCR. The SCR catalyst 32 is from the catalyst 18 , in particular of its coating 20 , and from the SCR catalyst 30 spaced and in addition to the SCR catalyst 30 and in addition to the catalyst 18 intended. The catalyst 18 , the particle filter 28 and the first SCR catalyst 30 For example, are close to the engine exhaust aftertreatment elements, which like the internal combustion engine 12 in the engine compartment 22 are arranged. The exhaust aftertreatment elements are preferably arranged in a common housing or in a common exhaust gas box. In contrast, the SCR catalyst 32 as an underbody catalyst (UB catalyst), so that the SCR catalyst 32 is arranged in the region or below a subfloor formed by the body of the motor vehicle. The exhaust aftertreatment device 10 also includes an ammonia slip catalyst 34 (ASC), which is downstream of the SCR catalyst 32 is arranged. For example, the SCR catalyst 32 and the ammonia slip catalyst 34 arranged in a common housing or in a common box. The ASC is also an underbody catalyst.

Even at very low temperatures of the exhaust gas, the SCR, especially in the catalyst 18 To run advantageously, and thus a particularly low-emission cold start and a low-temperature activity of the catalyst 18 To be able to realize sees an operating strategy for operating the exhaust aftertreatment device 10 that a sufficient amount of, ammonia (NH ₃ ) already after or during the cold start and during cooling phases of the internal combustion engine 12 in the SCR coating material of the catalyst 18 is available. For this purpose, ammonia in particular already in the catalyst 18 be pre-stored, the ammonia in particular before a shutdown of the motor vehicle in the catalyst 18 stored, in particular pre-stored, is. Alternatively or additionally, it is conceivable that the reducing agent by means of the adding device 24 or another not in the 1 For example, in small amounts, the feed device is introduced into the exhaust gas, wherein, for example, the reducing agent per se already comprises ammonia. For this purpose, it is preferably provided that already from or at a temperature of the exhaust gas of 50 degrees Celsius or even already from room temperature by means of the addition device 24 or the further feed device, the reducing agent or ammonia in the exhaust gas is introduced. The reducing agent is, for example, gaseous ammonia (NH ₃ ), wherein the gaseous ammonia or the reducing agent is already introduced in gaseous form into the exhaust gas, in particular injected.

As a result of the fact that the AdSCR can store nitrogen oxides, excessive nitrogen oxide emissions, in particular, can be avoided by means of the catalyst 18 or in the catalyst 18 Nitrogen oxides are stored while the SCR catalysts 30 and 32 and the particulate filter designed as, for example, SDPF 28 are still too cold to convert NO _x with NH ₃ or to catalyze the SCR. As already indicated, it can be provided that the particle filter 28 a coating which is designed to catalyze the SCR or can catalyze the SCR.

2 shows a second embodiment of the exhaust aftertreatment device 10 , The second embodiment differs in particular from the first embodiment, that of the coating 20 having catalyst 18 downstream of the particulate filter 28 and downstream of the first SCR catalyst 30 is arranged, wherein the particle filter 28 upstream of the catalyst 18 and downstream of the first SCR catalyst 30 is arranged. In 1 and 2 illustrates an arrow 36 a so-called ammonia slip. Under the ammonia slip is to understand a lot of unused reducing agent or ammonia. Under the unused ammonia is to be understood ammonia, which has not been converted in the course of SCR or has not reacted with nitrogen oxides contained in the exhaust gas to nitrogen and water. Excessive emission of unconsumed ammonia may, for example, by means of the second SCR catalyst 32 be avoided because, for example, at least a portion of the still unused ammonia in the SCR catalyst 32 reacts with nitrogen oxides contained in the exhaust gas to substantially nitrogen and water. In addition, excessive emission of unconsumed ammonia by the ammonia slip catalyst 34 be avoided. In the first embodiment, the AdSCR can cool down more quickly compared to the second embodiment and is thus faster for a new cold start or for the next cooling phase of the exhaust aftertreatment device such as in a downhill drive available. In the second embodiment, the AdSCR stays cold longer and stores nitrogen oxides longer, however, the AdSCR stays warm longer in comparison to the first embodiment and therefore becomes available again later in the next cooling phase compared to the first embodiment.

Estimates with temperature profiles of MPS measurements show that the storage duration of the second embodiment is slightly longer than in the first embodiment. However, controlling the introduction of the reducing agent into the exhaust gas is more difficult in the second embodiment than in the first embodiment since both the SCR catalyst 30 as well as the trained as SDPF particulate filter 28 have a memory functionality with respect to storage of ammonia and therefore function as a kind of dead member. In the second embodiment can be expected later with water, which has a positive effect on the storage capacity. Overall, it can be seen that both embodiments have the same advantages and disadvantages as with technical objects and are to be selected for respective applications.

3 shows a third embodiment of the exhaust aftertreatment device 10 , In the third embodiment, downstream of the oxidation catalyst 26 and upstream of the catalyst 18 , in particular upstream of the feed device 24 , An institution 38 for storing and / or adsorbing water (H ₂ O) contained in the exhaust gas. The background is that water worsens the performance of the AdSCR. By means of the device 38 can be stored upstream of the AdSCR water, in particular adsorbed, which, for example, a delay in the arrival of water in the AdSCR is delayed. The device 38 is thus formed, for example, as a water adsorber for the adsorption of water and preferably before the addition device 24 and thus arranged in front of a metering point, at which by means of the feed device 24 the reducing agent is introduced into the exhaust gas, in particular injected, will or can be. The arrangement of the device 38 in front of the metering point is advantageous because the device 38 optionally also designed to store ammonia, in particular to adsorb. This depends, for example, on a material of the device 38 from. Again, in other words, by means of the device 38 Contained in the exhaust and / or contained in the exhaust water collected and retained at least temporarily, since the collected water or the collected ammonia from the exhaust gas in the device 38 at least temporarily stored, in particular adsorbed, can be.

The device 38 can be used both in the first embodiment and in the second embodiment. Since the AdSCR is positioned further forward than the second embodiment in the first embodiment, it is expected that the positive effect of the device formed as a water adsorber 38 in the first Embodiment is larger than in the second embodiment.

The following is a possible regeneration strategy for the regeneration of the catalyst 18 illustrated. Under the regeneration of the catalyst 18 it should be understood, for example, that in the catalyst 18 stored nitrogen oxides at least partially from the catalyst 18 be removed. Conventional, in particular passive, nitric oxide storage systems usually have the problem that their nitrogen oxide storage can be fully released again only at very high temperatures. This means that during or after a possible re-cold start or during a cooling down phase, the entire storage capacity may not be available. Active nitrogen oxide storage systems must be protected by leaking fat, that is, by a rich operation of the internal combustion engine 12 be regenerated. In contrast, AdSCR is active in terms of SCR. This means that the AdSCR, in particular its nitrogen oxide storage for storing nitrogen oxides contained in the exhaust gas, by an addition or addition of ammonia into the exhaust gas and / or with in the catalyst 18 pre-stored ammonia, in particular in a regular operation, can be regenerated. This means that the aforementioned regeneration strategy for regenerating the catalyst 18 only requires an overdose of ammonia in the exhaust gas. Under the overdose is to be understood that in the exhaust gas, a larger amount of ammonia or reducing agent is introduced, as for the complete removal of the nitrogen oxides from the exhaust gas, in particular theoretically, would be required. The regeneration strategy and thus the introduction of ammonia or reducing agent into the exhaust gas take place, in particular, as a function of a level of the AdSCR, the level of which characterizes or describes a quantity of nitrogen oxides stored in the AdSCR. In addition, a regeneration strategy can be configured such that upon determination of an amount of ammonia or reducing agent to be introduced in addition to a fill level of the NO _x storage coating material of the catalyst 18 an ammonia level of the SCR coating material of the catalyst 18 determined and taken into account.

The following describes an operating strategy of the AdSCR. The AdSCR shows already at or above 50 degrees Celsius or even at less than 50 degrees Celsius exhaust gas temperature a so-called SCR activity, that is, a catalyst effect in terms of catalysis of the SCR, especially if in the AdSCR ammonia is pre-stored, or when adding, for example, ammonia stored in an ammonia cartridge to the exhaust gas from very low temperatures, already already below 50 degrees Celsius.

Thus, the operating strategy may provide for pre-loading of the AdSCR with ammonia. In a cold start, the AdSCR, in particular nitrogen oxides, can store and simultaneously implement, in particular at temperatures which are considerably lower than 150 degrees Celsius. The introduction of the reducing agent or of ammonia into the exhaust gas should therefore be controlled or regulated accordingly, in particular in such a way that ammonia is present on or in the AdSCR during or after a cold start and / or during cooling phases. In principle, it is conceivable that the AdSCR at any position downstream of the feed device 24 can be arranged. The AdSCR has no oxidation functionality with respect to oxidation of components contained in the exhaust gas such as unburned hydrocarbons and carbon monoxide, in particular because the catalyst 18 free of oxidation-catalytically active platinum metals (PGM).

4 shows a fourth embodiment of the exhaust aftertreatment device 10 , In the fourth embodiment, the particulate filter is preferably formed as DPF, in particular as SDPF 28 upstream of the SCR catalyst 30 arranged, which upstream of the catalyst 18 (AdSCR) is arranged. Thus, the catalyst 18 downstream of the particulate filter 28 and downstream of the first SCR catalyst 30 arranged, wherein the exhaust aftertreatment elements are arranged in the common housing or in the common box. In the fourth embodiment, the AdSCR stays cold longer and still adsorbs during the SDPF and the SCR catalyst 30 already achieve partial sales. By adsorbing is meant that the catalyst 18 stored in the exhaust gas nitrogen oxides stores. In other words, it is the catalyst 18 For example, for storing nitrogen oxides contained in the exhaust gas formed by adsorption. Because the AdSCR after the SDPF and after the SCR catalyst 30 is less exposed to any sulfur contained in the exhaust gas. In addition, any water contained in the exhaust later arrives at the AdSCR.

5 shows a fifth embodiment of the exhaust aftertreatment device 10 , In the fifth embodiment, the catalyst 18 (AdSCR) and the particle filter 28 summarized or integrated into a common structural unit, wherein the first SCR catalyst 30 downstream of the assembly and thus downstream of the AdSCR and downstream of the particulate filter 28 is arranged. The integration of the AdSCR and the particle filter 28 in the common structural unit can be provided such that, for example, the particulate filter 28 the coating 20 and is thus supplemented by the AdSCR or its functionalities. As a result, an advantageous storage function for storing nitrogen oxides can be realized. In particular, in the catalyst 18 (AdSCR) nitrogen oxides are not only advantageously stored from room temperature, but even at low exhaust temperatures of less than 50 degrees Celsius already reduced to nitrogen, as long as the SCR catalysts 30 and 32 are still cold and can not convert nitric oxide.

Finally shows 6 a sixth embodiment. In the sixth embodiment, the exhaust aftertreatment device 10 exactly one SCR catalyst in the form of the underside catalyst designed as SCR catalyst 32 on which downstream of the catalyst 18 is arranged. Upstream of the catalyst 18 and upstream of the particulate filter 28 is no further SCR catalyst arranged, wherein the particulate filter 28 has the coating described above, which is effective for catalyzing the SCR.

7 FIG. 12 is a diagram for further illustrating an operation and a function of the exhaust aftertreatment device. FIG 10 , The in 7 illustrated operation of the exhaust aftertreatment device 10 coincides with the operation, in particular with the fired operation, the internal combustion engine 12 together so that during operation of the exhaust aftertreatment device 12 Exhaust gas of the internal combustion engine 12 flows through the exhaust aftertreatment device. This in 7 Diagram shown has an abscissa 40 on, on which the time is applied. On a first ordinate 42 In the diagram, a concentration is plotted, for example, in units of parts per million (ppm). On a second ordinate 44 For example, a temperature is plotted in degrees Celsius (° C). A first history entered in the diagram 46 illustrates a concentration of nitrogen monoxide (NO) contained in exhaust gas flowing into the AdSCR. In other words, the course illustrates 46 a concentration of nitrogen monoxide (NO) entering the AdSCR. A second history entered in the diagram 48 illustrates a temperature of the exhaust gas, especially in the AdSCR. Thus, the history illustrates 48 For example, a prevailing in the AdSCR temperature or a temperature of the AdSCR.

A third course in the diagram 50 illustrates a concentration of nitrogen dioxide (NO ₂ ) contained in the exhaust gas, in particular in the exhaust gas flowing out of the AdSCR. In other words, the course illustrates 50 a concentration of nitrogen dioxide (NO ₂ ) flowing out of the AdSCR. A fourth history entered in the diagram 52 illustrates a concentration of nitrogen monoxide (NO) contained in the exhaust gas, particularly in exhaust gas effluent from the AdSCR. In other words, the course illustrates 52 a concentration of nitrogen monoxide (NO) effluent from the AdSCR. A fifth course entered in the diagram 54 1 illustrates a concentration of, in particular pure, nitrogen (N ₂ ) present in the exhaust gas, in particular in the exhaust gas flowing out of the AdSCR. In other words, the course illustrates 54 a concentration of, in particular pure, nitrogen (N ₂ ) flowing out of the AdSCR. Out 7 is particularly well recognizable that already from a very low, in 7 With T1 designated temperature of the course 54 and thus the concentration of nitrogen flowing out of the AdSCR, in particular pure, nitrogen begins to increase. The temperature T1 is at least substantially 50 degrees Celsius, or even less than 50 degrees Celsius in some AdSCR configurations. Thus, it can be particularly well recognized from the diagram that the exhaust gas and the NO stored in the AdSCR can already be de-nitrogenized from a particularly low temperature by means of the AdSCR, whereby the nitrogen oxide emissions can be kept particularly low with the AdSCR. Next is out 7 to recognize that even at room temperature of the exhaust gas in the AdSCR a storage of NO takes place.

LIST OF REFERENCE NUMBERS

10

exhaust treatment device

12

Internal combustion engine

14

combustion chamber

16

arrow

18

catalyst

20

coating

22

engine compartment

24

adding means

26

oxidation catalyst

28

particulate Filter

30

SCR catalyst

32

SCR catalyst

34

Ammonia slip catalyst

36

arrow

38

Facility

40

abscissa

42

ordinate

44

ordinate

46

course

48

course

50

course

52

course

54

course

T1

temperature

Claims (13)

Exhaust gas aftertreatment device (10) for a motor vehicle, comprising at least one catalytic converter (18) through which exhaust gas from an internal combustion engine (12) of the motor vehicle has at least one SCR material for catalyzing a selective catalytic reduction for reducing nitrogen oxides contained in the exhaust gas and at least one NO _x Storage material for at least temporarily storing nitrogen oxides contained in the exhaust gas, and with at least one upstream of the catalyst (18) arranged feed device (24), by means of which at least one reducing agent by means of which contained in the exhaust gas nitrogen oxides are reduced in the selective catalytic reduction into which exhaust gas can be introduced. Exhaust after-treatment device (10) according to Claim 1 , characterized in that the catalyst (18) is free of oxidation-catalytically active noble metal-containing coating materials. Exhaust gas aftertreatment device (10) according to one of the preceding claims, characterized in that the catalyst (18) is arranged in a first block of exhaust aftertreatment elements in the flow direction of the exhaust gas after exit of the exhaust gases from the internal combustion engine (12). Exhaust after-treatment device (10) according to one of the preceding claims, characterized in that the exhaust-gas aftertreatment device (10) has at least one oxidation catalytic converter (26), in particular diesel oxidation catalytic converter, arranged upstream of the feed device (24). Exhaust after-treatment device (10) according to one of the preceding claims, characterized in that the at least one reducing agent is formed as an aqueous urea solution. Exhaust after-treatment device (10) according to Claim 1 to 4 , characterized in that the at least one reducing agent comprises at least, from the feed device (24) in the gaseous state einbringbares, ammonia. Exhaust after-treatment device (10) according to Claim 5 Characterized in that at least one further reducing agent by means of which contained in the exhaust nitrogen oxides are reduced in the selective catalytic reduction arranged from an upstream of the catalyst (18) further adding means can be introduced into the exhaust gas, wherein the additional reducing agent, at least, another of the Feed device in gaseous state einbringbares, ammonia comprises. Exhaust gas aftertreatment device (10) according to one of the preceding claims, characterized in that the exhaust aftertreatment device (10) at least or exactly one arranged downstream of the catalyst (18) and from the catalyst (18) spaced and in addition to the catalyst (18) provided SCR catalyst (30, 32). Exhaust after-treatment device (10) according to one of the preceding claims, characterized in that the exhaust-gas aftertreatment device (10) has at least or exactly one particle filter (28) arranged downstream or upstream of the catalytic converter (18). Method for operating an exhaust gas aftertreatment device (10) of a motor vehicle, comprising at least one catalytic converter (18) through which exhaust gas of an internal combustion engine (12) of the motor vehicle flows, comprising at least one SCR material for catalyzing a selective catalytic reduction for reducing nitrogen oxides contained in the exhaust gas and at least a NO _x storage material for at least temporarily storing nitrogen oxides contained in the exhaust gas, and with at least one upstream of the catalyst (18) arranged feed device (24), by means of which at least one reducing agent, by means of which contained in the exhaust gas oxides in the selective catalytic Reduction can be reduced, can be introduced into the exhaust gas, which is waived in regular regeneration phases of the NO _x storage material in rich operation of the internal combustion engine. Method for operating an exhaust aftertreatment device (10) of a motor vehicle according to Claim 10 , characterized in that in a period of time for which the at least one addition means (24) is activated, a metered amount of reducing agent introduced is regularly raised to a metered amount which is higher than a first Dosierschwellwert, wherein the first Dosierschwellwert is a metered amount of reducing agent which is necessary to reduce substantially all of the nitrogen oxides contained in the exhaust stream upstream of the catalyst (18). Method for operating an exhaust aftertreatment device (10) of a motor vehicle according to Claim 10 or 11 , characterized in that during operation of the motor vehicle promptly before stopping the motor vehicle, a metered amount of reducing agent is increased to a value which is higher than a second Dosierschwellwert, wherein the second Dosierschwellwert is a Dosiermenge of reducing agent, which for the reduction of substantially all of the nitrogen oxides contained in the exhaust stream and for the reduction of substantially all stored on the NO _x storage material of the catalyst (18) nitrogen oxides is necessary. Method for operating an exhaust aftertreatment device (10) of a motor vehicle according to Claim 10 to 12 , characterized in that the feed device (24) or the further feed device for an introduction of the reducing agent into the exhaust gas is activated already from a temperature of the exhaust gas in the catalyst (18) of less than 100 degrees Celsius.

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