DE102004018648A1 - Integrated catalyst system to remove e.g. nitric oxides from exhaust gases comprises nitric oxide storing component, ammonia-generating component, ammonia-storing component and selective catalytic reduction component on common substrate - Google Patents

Abstract

Integrated catalyst system for removal of harmful substances containing nitric oxides comprises at least one nitric oxide storing component, at least one in situ ammonia-generating component, which converts nitric oxide to ammonia, at least one ammonia-storing component, and at least one selective catalytic reduction component to decompose nitric oxide by ammonia. At least two of the components are present on a common substrate or on a joined substrate system. An independent claim is included for preparation of the catalyst using washcoat process.

Description

The present invention relates to an integrated system for exhaust aftertreatment, which preferably comprises at least one NO _x storage component, at least one in situ ammonia production component, at least one ammonia storage component and at least one ammonia (NH ₃ ) -SCR component (hereinafter also: SCR component). and a process for exhaust aftertreatment using such a system.

The exhaust aftertreatment system according to the invention (hereinafter also referred to as "system") is suitable for removing nitrogen oxides (NO _x ) from exhaust gases, preferably from engine exhaust gases, under cyclic rich / lean conditions.

In a preferred embodiment, the method according to the invention comprises at least the following partial steps:
Storing NO _x under lean exhaust conditions in at least one NO _x storage component;
in situ conversion of the stored NO _x to ammonia (NH ₃ ) under rich exhaust conditions;
Storage of NH ₃ in at least one NH ₃ storage component under rich exhaust conditions;
Reaction of NH ₃ with NO _x under lean exhaust conditions.

The sub-steps "storage of NO _x " and "conversion of NH ₃ with NO _x " are preferably carried out at least partially and / or temporarily simultaneously and / or in parallel.

The inventive method is characterized by a high NO _x conversion rate over a wide temperature range.

The inventive method is preferably used to reduce NO _x emissions from lean-burned gasoline and diesel engines from motor vehicles.

NO _x storage catalysts are known from the prior art. NO _x storage catalytic converters are greased alternately with the aid of the engine control system and exposed to lean exhaust gas conditions. NO _x storage catalysts store NO _x during lean operation. The resulting NO _x adsorbates are then catalytically decomposed into nitrogen and oxygen in short "enrichment phases" (ie in the case of oxygen deficiency) under reducing conditions under a complicated and program-intensive motor control. Accordingly, such catalysts are referred to as "NO _x storage catalysts", "NO _x adsorbers" or as "NO _x storage / reduction catalysts".

The operation of NO _x storage catalysts is described in detail in SAE document SAE 950809.

NO _x storage catalytic converters operate, depending on the used _NOx -Speichermedium, in particular "temperature window", typically between 200 and 500 ° C. In case of thermal aging of NO, the width _x catalysts decreases the temperature window. The limited temperature window for both the Another problem with conventional NO _x storage catalytic converters is that during the richening phases, it is necessary to reduce the nitrogen oxides stored in the diesel engine, where high low-temperature activity is desired, as well as in lean-burn gasoline engines are, high secondary emissions, for example in the form of NH ₃ and H ₂ S, may occur.

Selective catalytic reduction (SCR) processes for reducing NO _x using NH ₃ as the selective reducing agent are also known in the art.

The SCR process is a highly efficient process to reduce NO _x emissions. SCR processes are used, for example, in stationary incinerators. In the SCR process, nitrogen oxides are converted to N ₂ with the aid of ammonia as a selective reducing agent. The stoichiometry of the SCR reaction, ie the ratio of molar amounts of NH ₃ and NO _x necessary to achieve an almost complete NO _x conversion, depends inter alia on the reaction temperatures and the catalysts used. In general, it can be stated that the molar amounts of ammonia must be of the same order of magnitude as those of nitrogen oxides in order to ensure high conversions.

In the US 4782 039 and the US 5451 387 high NO _x conversions are found at molar NH ₃ / NO _x rates in ranges of 0.75 - 1.25. In practice, the maximum NH ₃ / NO _x rate to be set is limited, inter alia, by the increasing NH ₃ breakdown (so-called "ammonia slip") with increasing NH ₃ / NO _x rate.

The DE 199 09 933 A1 discloses a method of operating an exhaust gas purification plant with internal ammonia production. In one embodiment of the DE 199 09 933 A1 Ammonia production takes place by means of separately controllable combustion sources. At least one of the combustion sources generates a rich exhaust gas that is passed over an ammonia generation catalyst. The ammonia thus produced is introduced into the NO _x -containing effluent of the lean combustion sources. With the help of a nitrogen oxide reduction catalyst NO _x and NH _{3 are converted} to N ₂ .

This embodiment is limited in practical implementation, since the amount of NH ₃ generated at the ammonia generation catalyst and the amount of NO _x present in the other effluent must always be in a certain stoichiometry, since otherwise either NH ₃ or NO _x would be emitted in an increased concentration.

In a further embodiment of the DE 199 09 933 A1 a NO _x adsorption catalyst, an ammonia generating catalyst and a nitrogen oxide reduction catalyst are connected in series. For example, the nitrogen oxides increasingly contained in the exhaust gas during lean operating phases of the combustion sources can be temporarily stored in the nitrogen oxide adsorption catalyst and desorbed in a respective subsequent rich operation phase and used at least in part in the downstream ammonia production catalyst to produce ammonia. The fact that the catalysts are connected in series, a simultaneous enrichment of nitrogen oxides under lean exhaust conditions and a conversion of ammonia with the nitrogen oxides is not possible.

Another exhaust gas purification of this type is disclosed in WO97 / 17532. This document describes various arrangements of catalysts in which each catalyst performs a particular function. In one of the embodiments, an ammonia generating catalyst, an NO _x adsorption catalyst, a NH ₃ storage catalyst and another catalyst are connected in series. Such an arrangement is well suited to suppress secondary emissions in the form of NH ₃ . In addition, NO _x , which is no longer stored by the NO _x adsorption catalyst can be reduced in the downstream Ammoniakadsorptionskatalysator under desorption of ammonia. Thus, two different processes for NO _x reduction occur sequentially to each other: First, the NO _{x is} stored at the storage catalyst; if this is filled, breakthrough NO _x can be broken down with the NH ₃ to N ₂ . With the system set out NO _x and NH ₃ can breakthroughs are both lean and during rich operation decreased. A simultaneous storage and reduction of nitrogen oxides is not possible here.

US 2002/0116920 A1 describes an exhaust aftertreatment process in which an NH ₃ generation catalyst, an oxidation catalyst and an SCR catalyst are installed sequentially. In rich operation, NH _{3 is} generated by the NH ₃ generation catalyst. This is stored on the SCR catalyst. In lean operation, the SCR catalyst converts the previously stored NH ₃ with the NO _x emitted from the engine to N ₂ . The oxidation catalyst increases the efficiency of the SCR catalyst by oxidation of the NO to NO ₂ .

The method described in US 2002/0116920 A1 has the disadvantage that the stoichiometry between NO _x and NH ₃ necessary for the efficient conversion of NO _x by means of the SCR reaction is maintained only under technically high costs and with considerable additional fuel consumption in real operation can. In the case of rich operation, approximately the same molar amount of NH _{3 would have to be} formed as is emitted in the subsequent lean operation. However, this means that relatively long fat phases would have to be realized, which inevitably leads to increased fuel consumption and increased CO and HC emissions.

The object of the invention was to develop an exhaust aftertreatment method for removing NO _x from exhaust gases of lean-burn / lean-burn engines whose NO _x removal efficiency and secondary emission reduction efficiency is higher than that of the catalysts from the prior art.

The object of the invention is achieved by a method which in a preferred at least the following sub-steps:
Storing NO _x under lean exhaust conditions in at least one NO _x storage component;
in situ conversion of the stored NO _x to ammonia (NH ₃ ) under rich exhaust conditions;
Storage of NH ₃ in at least one NH ₃ storage component under rich exhaust conditions;
Reaction of NH ₃ with NO _x under lean exhaust conditions.

The sub-steps "storage of NO _x " and "conversion of NH ₃ with NO _x " are preferably carried out at least partially and / or temporarily simultaneously and / or in parallel.

The object according to the invention is also achieved by an integrated catalyst system in which at least two different components have at least the following functionalities: (i) NO _x storage under lean exhaust conditions, (ii) in-situ reduction of the stored NO _x to ammonia (NH ₃ ) under rich exhaust conditions, (iii) storage of the NH ₃ in an NH ₃ storage medium under rich exhaust conditions, (iv) reaction of NH ₃ with NO _x under lean exhaust conditions. The components of the system are functional and preferably also locally combined, preferably in direct contact with each other and more preferably on a contiguous or related or on or in a common substrate.

The Integrated invention Catalyst system consists of at least two components with at least the functionalities (i) to (iv) together. In addition, the catalyst system can be any number have further components with any other functionalities. Each individual component can itself be built from components be, for example, from carrier and active components.

According to the invention, the NO _x storage technology described above is combined with the SCR technology described above in an integrated exhaust aftertreatment system. The ammonia necessary for the SCR process is not exclusively, but to a considerable extent, recovered from the nitrogen oxides bound in the NO _x storage component, ie in situ. An additional supply of ammonia from outside in any quantities is possible.

Under The term (catalyst) component is used in the present context Scripture any material understood that at least one of the effect of the integrated catalyst system has necessary functionalities.

For the purposes of the present invention, the term NO _x conversion performance is understood to mean the measure for the removal of a specific amount of NO _x per unit time as a function of the exhaust gas composition, the exhaust gas temperature, the oxygen partial pressure, the NO _x engine emission, the exhaust gas volumetric flow and the lean operating time of an exhaust gas aftertreatment system become.

Under lean operating time is to be understood the length of time in which the exhaust aftertreatment system is continuously exposed to a lean exhaust gas. The lean operating time is an important factor for the level of the NO _x storage catalyst, ie the integral amount of NO _x taken up by the NO _x storage catalytic converter.

When an essential criterion for the classification of both engine types as well as catalysts, the ratio of air to fuel, expressed by the "air ratio" λ. This corresponds to a value of λ = 1.0 exactly the stoichiometric relationship from fuel to dry air, i. it is just enough Air in the combustion chamber, so that all fuel is stoichiometric to burn carbon dioxide and water.

Under lean exhaust gas is an exhaust gas with an air ratio λ> 1 understood, and exhaust gas under exhaust gas with an air ratio λ <1. In terms of a fuel consumption minimization as short as possible Anfettungszeiten, lowest possible enrichment depths and longest possible lean times. Fat-lean time ratios and enrichment depths depend, among other things, heavily on the NO _x conversion performance and NO _x regeneration capability of the exhaust aftertreatment systems. During enrichment, internal combustion engines emit increased amounts of carbon monoxide (CO) and hydrogen (H ₂ ) and also hydrocarbons (HC). These reductively active ingredients reduce the nitrogen oxides to nitrogen and ammonia and thereby themselves decompose to carbon dioxide (CO ₂ ) and water (H ₂ O).

As low as possible richening times and depths are also preferred for the reason that breakthroughs of CO and HC and increased secondary emissions, for example in the form of NH ₃ , H ₂ S and COS, should be minimized.

According to a preferred embodiment of the system according to the invention, at least one NO _x storage component, at least one in-situ ammonia production component, at least one ammonia storage component and at least one SCR component should be spatially and / or functionally integrated such that a high NO _x conversion performance by a simultaneous NO _x Sequence of NO _x storage and SCR reaction is ensured, and preferably secondary emissions in the form of NH ₃ to be minimized.

Despite the high complexity of the exhaust aftertreatment system of the present invention, in a further preferred embodiment it is possible to combine all the (catalytic) components necessary for the presentation of the system on a common or cohesive substrate and thus provide an efficient and cost effective exhaust aftertreatment system. The integration of the (catalytic) components (NO _x storage component, in situ ammonia production component, NH ₃ storage component, SCR component) on a common substrate, preferably in the form of a monolithic honeycomb body, is preferably achieved so that the aforementioned components simultaneously or sequentially applied to a common substrate, preferably by known washcoat methods.

The NO _x storage component used according to the invention may in principle be composed of prior art noble metal components and / or storage media.

As NO _x storage media are basically all materials suitable, which are due to their chemical, preferably basic, properties in a position to store or adsorb nitrogen oxides, the stored nitrogen oxides must be stable under the appropriate temperature conditions. Accordingly, compounds of alkali metals (Na, K, Rb, Cs), alkaline earth metals (Mg, Ca, Sr, Ba), rare earth metals (La, Ce, Pr, etc.) and zirconium as storage materials are preferred Consider, such. Example in the form of their oxides, hydroxides or carbonates. As active-metal components, the platinum metals (Pt, Pd, Rh, Ru, Ir) applied to porous carrier oxides are preferred.

During lean operation, the task of the NO _x storage component is to store the NO _x emitted by the engine. Falls due to the increasing saturation of the NO _x storage component by NO _x NO _x -Konvertierungsleistung to an unacceptable level, takes place by means of internal engine measures enrichment of the exhaust gas. The stored NO _x is reduced in the course of this enrichment. The extent to which an unacceptable NO _x storage level is achieved can preferably be determined by the use of a NO _x sensor, which is located downstream of the exhaust aftertreatment system according to the invention.

When using conventional, equipped with NO _x storage catalytic exhaust aftertreatment systems, the enrichment should lead to the most selective reduction of nitrogen oxides to N ₂ . The formation of NH ₃ is undesirable in these systems.

In the context of the present invention, however, the aim is to form NH ₃ during the Anfettungsphase. Unlike in the publications cited in the prior art, the NH ₃ formation according to the invention thus takes place largely or at least predominantly from the nitrogen oxides previously stored in the NO _x storage component.

The method according to the invention is distinguished, inter alia, by the fact that NH ₃ can be generated within a very short time interval, since the amount of NO _x accumulated over a relatively long period of time, namely that of the preceding lean phase, is available for the reduction to ammonia.

The highly selective reduction of the nitrogen oxides to N ₂ during the Anfettungsphasen is in the context of the present invention is not mandatory, yes even in principle undesirable. Efficient reduction of NO _x to NH ₃ can be controlled, on the one hand, by the amount of hydrogen (H ₂ ) and carbon monoxide (CO) emitted during enrichment and, on the other hand, by an optimized catalyst formulation.

Preferably, one of the active metal components present in the NO _x storage components additionally assumes the function of the in-situ ammonia generating component or of the ammonia generating.

It should be noted that the ammonia is not exclusively from those in the NO _x storage component must also be derived in subordinate or at least low (<50%, preferably <20%) amount of those nitrogen oxides that are emitted during the Anfettungsphasen from the engine.

The ammonia formed in this way is now stored in a suitable NH ₃ storage component. The NH ₃ storage component is preferably capable of sorbing the released NH ₃ in a wide temperature range, both under lean and rich exhaust conditions.

As the NH ₃ storage component, any material can be used which at least partially adsorbs, absorbs, attaches as an adduct or otherwise store NH ₃ . Lewis acids or Bronsted acids are preferred.

In the context of the present invention, the NH ₃ storage component preferably serves to absorb the NH ₃ produced in the fatty phase as quantitatively as possible, but at least to a considerable extent. Here, the retting times and depths should be as low as possible in order to minimize the additional fuel consumption

For the purposes of the present invention, the enrichment times and depths should be large enough to (i) emptying the NO _x storage catalyst as completely as possible and (ii) to ensure an efficient reduction of the nitrogen oxides liberated at the moment of enrichment to ammonia. Preferred time ratios of lean times to fat times are in the ranges from 5: 1 to 100: 1, preferably from 30: 1 to 80: 1. Preferred enrichment depths are in a range of 0.8 <λ <0.99.

When switching from rich operation to lean operation, the emission of the engine-emitted NO _{x is} reduced in two different ways, preferably simultaneously: one part of the NO _x is again stored in the NO _x storage component, while the other part directly with the bound in the NH ₃ storage component NH ₃ reacts to N ₂ . Since NO _x reduction now takes place simultaneously and on two different reaction paths, according to the invention overall a significantly higher NO _x conversion power than the prior art method can be achieved.

The emitted NH ₃ is bound in accordance with the present invention in an NH ₃ storage component. During the subsequent lean phase, the NH _{3 can} then according to the so-called SCR reaction (Selective Catalytic Reduction) with the emitted from the engine NO _x under lean exhaust conditions to N _{2 are} degraded. The SCR reaction takes place in or on an SCR component. As SCR component, any material known to those skilled in SCR reactions can be used, for example V / Ti catalysts as known from stationary exhaust gas treatment. In a preferred embodiment, the SCR component is a Lewis or Bronsted acid and thus also acts as an NH ₃ storage component.

According to the present invention, in a preferred embodiment, a combined NH ₃ storage component / SCR component is chemically constructed so that the stored NH ₃ does not reoxidize and emit NO _x in lean operation and only to a very limited extent with the oxygen contained in the exhaust gas becomes.

Since in this manner at least a portion of the _x first in the NO storage component stored NO _x in ammonia converted, and is then reacted in accordance with the SCR reaction to N _2, the inventive method allows increased NO _x -Konvertierungsleistungen, since the SCR reaction supports NO _x storage.

In order to enable the simultaneous execution of SCR reaction and NO _x storage, it is preferred to bring the NO _x storage component and / or the NH ₃ storage component and / or the SCR component into contact with each other, preferably in the form a physical (through) mixture. The contacting can also take place in other ways known to the person skilled in the art, for example by chemical and / or mechanical methods or by any desired combination of physical, chemical and mechanical methods.

In contrast, an exclusively or predominantly sequential arrangement of these components is not preferred since, in the case of a sequential arrangement, the SCR reaction and NO _x storage could occur only to a very small extent simultaneously with each other, but instead largely in succession. However, a certain amount of sequential execution of the reactions is not out of the ordinary of the present invention.

If, for example, the NO _x storage component were preceded by the NH ₃ storage component and the SCR component, lean operation would initially load the NO _x storage component with NO _x and only in the event of a decrease in NO _x storage with increasing lean operation mode The SCR reaction could make a significant contribution to the overall NO _x conversion.

In a preferred embodiment, the NH ₃ storage component and the SCR component are identical, ie, a corresponding material is capable of (i) incorporating NH ₃ under rich exhaust conditions and (ii) reacting under lean exhaust conditions in accordance with the SCR reaction.

In a preferred embodiment, the NO _x storage component contains at least one active metal. This ensures that even CO and HC can be effectively converted to carbon dioxide and water under rich, stoichiometric and lean exhaust conditions. Likewise, the conversion of NO _x to N ₂ or the NH ₃ formation under rich and stoichiometric exhaust gas conditions on an active metal contained in the NO _x storage component succeeds.

alternative can the catalyst system of the invention also additives such as oxygen storage materials - for example based on cerium-zirconium oxide.

Around CO and HC breakthroughs while To minimize the Anfettungsphasen, the exhaust aftertreatment system according to the invention in a preferred embodiment another catalyst, for example in the form of an oxidation catalyst, downstream be downstream.

The system of the invention has a higher NO _x conversion performance than conventional NO _x storage catalyst systems.

The method and system according to the invention can preferably be used for the following applications:
Particularly clear are the advantages of the invention, for example, if the exhaust gas temperatures, eg. B. caused by sudden load changes, either below or exceed the necessary for the storage of NO _x or favorable temperatures. In these cases, provided that sufficient NH _{3 is present} in the NH ₃ store, the SCR reaction alone can allow high NO _x conversions to N ₂ .

Further There are advantages in using the method according to the invention the engine is longer in the To be able to drive lean operation and secondary emissions to minimize.

A further advantage of the method and system according to the invention is that the four components necessary for the exhaust system according to the invention, ie NO _x storage component, NH ₃ generation component, NH ₃ storage component and SCR component, on a common carrier, body or substrate, such as a honeycomb body, can be integrated into a cohesive system. Compared to other processes, which rely on a continuous introduction of ammonia from the outside, the inventive method also has the advantage that the precise compliance with a defined, optionally active-regulated, stoichiometry of NH ₃ relative to NO _{x is} not necessary.

Short description of Characters:

1 shows the content of NO _x (vertical axis, in arbitrary units) in an engine exhaust as a function of time (horizontal axis) using a conventional storage catalyst at 250 ° C (5s lean / 60s lean);

2 shows the content of NH ₃ (vertical axis, in arbitrary units) in an engine exhaust as a function of time (horizontal axis) using a conventional storage catalyst at 250 ° C (5s lean / 60s lean);

3 shows the content of NO _x (vertical axis, in arbitrary units) in an engine exhaust as a function of time (horizontal axis) when carrying out the process according to the invention using the integrated system according to the invention at 250 ° C (5s lean / 60s lean);

4 shows the content of NH ₃ (vertical axis, in arbitrary units) in an engine exhaust as a function of time (horizontal axis) when carrying out the method according to the invention using the integrated system according to the invention at 250 ° C (5s lean / 60s lean).

The figures relate to the embodiments described below:
Measurements concerning the process of the invention using the system of the invention were performed in stainless steel fixed bed laboratory reactors in simulated engine exhaust. The system was tested in cyclic fat / lean operation (5 s fat / 60 s lean).

The test parameters were as follows: Temperature range: 150-450 ° C Gas mixture composition skinny: 1000 vppm CO, 100 vppm propene, 300 vppm NO, 10% O ₂ , balance - N ₂ . fat: 0.03% O ₂ , ~ 6% CO, ~ 2% H ₂ Gas flow rate: 45,000 h ^-1

The measurement of O _{2 was} carried out with a lambda meter from. Etas. NO _x was measured using a chemiluminescer from Ecophysics. The measurement of NH _{3 was} carried out with a mass spectrometer from. Balzers.

The in the 1 to 4 The measurements shown allow a comparison of a conventional method using a conventional NO _x storage catalyst ( 1 and 2 ) with the inventive method using the exhaust aftertreatment system according to the invention, consisting of NO _x storage component, NH ₃ generation component, NH ₃ storage component and SCR component ( 3 and 4 ). The four components mentioned were in the case of the embodiment together on a single honeycomb carrier. For comparison between the conventional reference system and the system according to the invention, the masses of NO _x storage component and active metal used were identical in each case. In addition to the NO _x storage component, the system according to the invention also contained a component which functions both as NH ₃ storage and as SCR catalyst.

1 shows the concentration of NO _x (vertical axis, in arbitrary units) in an engine exhaust as a function of time (horizontal axis) using a conventional storage catalyst at 250 ° C (5s lean / 60s lean). 2 Accordingly, the concentration of NH ₃ (vertical axis, in arbitrary units) in an engine exhaust as a function of time (horizontal axis) using the same conventional storage catalyst at 250 ° C (5s lean / 60s lean).

3 shows the concentration of NO _x (vertical axis, in arbitrary units) in an engine exhaust as a function of time (horizontal axis) when carrying out the process according to the invention at 250 ° C (5s lean / 60s lean); 4 shows accordingly the concentration of NH ₃ (vertical axis, in arbitrary units) in an engine exhaust as a function of time (horizontal axis) when carrying out the method according to the invention at 250 ° C (5s fat / 60s lean).

It is clear from the measurements that (i) the exhaust aftertreatment system according to the invention has no (significant) NH ₃ emissions during the enrichment phases unlike a conventional NO _x storage catalyst and also (ii) a (virtually) complete removal over the entire lean operating time guaranteed by NO _x . The conventional NO _x storage catalyst, however, loses significantly with increasing lean operating time efficiency.

Claims (9)

A method for the removal of NO _x from the exhaust gases of lean-burn engines in cyclic lean / rich operation, comprising at least the following substeps: storage of NO _x under lean exhaust conditions in at least one NO _x storage component, In-situ conversion of the stored NO _x to ammonia (NH ₃ ) under rich exhaust conditions, storage of NH ₃ in at least one NH ₃ storage component under rich exhaust conditions, reaction of NH ₃ with NO _x under lean exhaust conditions, the sub-steps "storage of NO _x "and" implementation of NH ₃ with NO _x "run at least temporarily and / or partially simultaneously and / or in parallel. The method of claim 1, wherein the for carrying out the different sub-steps required components a spatially and / or functionally coherent Form system. Method according to claim 2, wherein at least two, preferably all, components on a common substrate or an interconnected substrate system. Method according to one of the preceding claims, wherein NH ₃ storage and NH ₃ conversion according SCR process carried out using the same component. Method according to one of the preceding claims, wherein for the storage of NO _x all materials are used, which are due to their chemical properties in a position to interact with nitrogen oxides. Method according to one of claims 2 to 5, wherein the spatially and / or functionally coherent Contains system components, for the production of ammonia, ammonia storage and implementation from ammonia to nitrogen are used. Method according to one of the preceding claims, wherein the components on a molding be applied, preferably selected on moldings Honeycomb structures, pellets, beads, or extruded extrusions. Integrated catalyst system, at least consisting of at least one NO _x storage component, at least one in-situ ammonia generating component, at least one ammonia storage component, and at least one SCR component, wherein at least two of these components, preferably all of these components, on a common substrate or an interconnected Substrate system present. System according to claim 8, characterized in that downstream of the integrated catalyst system, an oxidation catalyst is downstream.