EP1225312A2 - Device for treating an exhaust gas from a combustion engine - Google Patents
Device for treating an exhaust gas from a combustion engine Download PDFInfo
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- EP1225312A2 EP1225312A2 EP01403246A EP01403246A EP1225312A2 EP 1225312 A2 EP1225312 A2 EP 1225312A2 EP 01403246 A EP01403246 A EP 01403246A EP 01403246 A EP01403246 A EP 01403246A EP 1225312 A2 EP1225312 A2 EP 1225312A2
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- substance
- upstream
- treatment device
- downstream
- nitrogen
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Classifications
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
- F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
- F01N3/0807—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents
- F01N3/0828—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents characterised by the absorbed or adsorbed substances
- F01N3/0842—Nitrogen oxides
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
- F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
- F01N3/0807—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents
- F01N3/0814—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents combined with catalytic converters, e.g. NOx absorption/storage reduction catalysts
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
- F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
- F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
- F01N3/24—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by constructional aspects of converting apparatus
- F01N3/28—Construction of catalytic reactors
- F01N3/2803—Construction of catalytic reactors characterised by structure, by material or by manufacturing of catalyst support
Definitions
- the invention relates to a gas treatment device. combustion engine exhaust.
- the invention relates more particularly to a device for exhaust gas treatment of a combustion engine, including a diesel or gasoline engine poor mixture.
- exhaust systems are equipped in a known manner with catalysts, in particular with "three-way" catalysts so as to cause the reaction polluting substances passing through them, to reduce harmful emissions.
- Such catalysts can allow the oxidation of unburnt hydrocarbons and carbon oxides when the fuel / air mixture is poor, i.e. the ratio between fuel mass and air mass is less than richness stoichiometric.
- These catalysts also allow the reduction of oxides nitrogen when the fuel / air mixture is rich, i.e. that the ratio between the mass of fuel and the mass of air is greater than stoichiometric richness.
- Such a treatment device called an oxide trap nitrogen
- the storage of nitrogen oxides mainly consists in oxidizing the nitrogen monoxide to nitrogen dioxide which is then stored in the form of nitrates (NO - 3 ) in the nitrogen oxide trap.
- the oxidation reaction of nitrogen monoxide to dioxide nitrogen is mainly produced by a first substance of the mixture which covers the structural element of the trap. This substance contains metals and especially metals precious.
- the first substance partly allows the storage of nitrogen dioxide as nitrates but this step is mainly due to a second substance in the mixture which covers the trap.
- the oxidation reaction has kinetics which is slow at low temperatures, i.e. at temperatures of the order of 200 to 300 ° C and which increases depending on the temperature.
- the trap then allows the storage of nitrogen dioxide formed in the initiation catalyst as well as nitrogen dioxide formed in the nitrogen oxide trap.
- Another solution is to increase the amount of precious metals, on the structure of the nitrogen oxide trap.
- increasing the amount of metals precious lowers the oxidation temperature of nitric oxide which increases the kinetics of the oxidation reaction, and by therefore improves the storage capacity of the low trap temperature.
- the invention offers a device for treating the exhaust gases of a combustion engine of the type which is inserted in the line exhaust and which has a support member which is crossed from upstream to downstream by the exhaust gases and which is coated with a mixture of at least one first substance which allows the oxidation of nitrogen monoxide to nitrogen dioxide and of a second substance which allows the storage of dioxide nitrogen, characterized in that the concentration of the first substance in the mixture decreases from upstream to downstream of the structural element so as to improve the ability of storage of nitrogen dioxide from the treatment device, especially when the exhaust gas temperature is less than 400 ° C.
- FIG. 1 shows a processing device 10 of the exhaust gases G of a combustion engine 12.
- the engine 12 can be a diesel engine or a gasoline operating in a lean mixture such as a gasoline with direct injection.
- An exhaust line 14 allows the flow of gases G from engine 12 to the atmosphere.
- a processing device 10 intended to purify the exhaust gases G is arranged to inside of line 14. It mainly consists of a catalyst 16 located in a room.
- the catalyst 16 consists of a support element 18 which is crossed from upstream to downstream by the exhaust gases G.
- the support member 18 is coated with a mixture.
- the mixture is consisting of a first substance 20, represented on the figures by black discs 20, which mainly allows a first stage of oxidation of nitrogen monoxide to dioxide nitrogen and a second substance 22, shown in the figures by black circles 22, which mainly allows a second stage of adsorption of nitrogen dioxide.
- catalyst 16 will therefore be called oxide trap nitrogen 16.
- the first substance 20 contains metals, especially precious metals.
- the second substance 22 is meanwhile, made from alkali or alkaline earth.
- Catalyst 16 can also include a substance which reduces nitrogen oxides when mixing air / fuel is rich.
- Catalyst 16 may also contain substances to oxidize unburnt hydrocarbons, as well as carbon oxides present in the exhaust gases which run on line 14.
- the concentrations of first and second substance 20, 22 in the mixture are evenly distributed over the support element 18 of the trap 16.
- such a processing device 10 does not have not sufficient storage capacity for nitrogen oxides to low temperature.
- the invention proposes that the concentration of the first substance 20 in the mixture is decreasing from upstream to downstream of the structural element 18, so as to improve the nitrogen oxides storage capacity of the treatment 10, especially when the gas temperature exhaust temperature is less than 400 ° C.
- the concentration of the first substance 20 upstream of the nitrogen oxides 16 according to the invention is greater than the homogeneous, i.e. constant, concentration of the first substance of a nitrogen oxide trap according to the state of the art.
- the variation in the concentration of the first substance causes an inverse variation in the concentration of the second substance.
- the concentration of the first substance 20 is lower than the concentration of the first substance in a trap with nitrogen oxides according to the state of the art.
- FIG. 2 represents a support element 18 made up of a single monolith which is coated with a mixture whose concentration of the first substance 20 is higher in upstream than downstream of the nitrogen oxide trap 16.
- the variation in concentration of the first substance 20 is regular between upstream and downstream of the support element 18. This solution is advantageous because nitrogen dioxide is formed near the areas in which nitrogen dioxide is adsorbed than what promotes this step.
- varying the concentration of the first substance 20 is done in stages. So the element of support 18 has several zones. The concentration of first substance 20 of an area is always less than the concentration of the first substance 20 in the adjacent area located upstream.
- the support element 18 may consist of a upstream monolith 24 and a downstream monolith 26 which are juxtaposed in the exhaust line 14 of the combustion engine 12.
- Each upstream 24 and downstream 26 monolith can correspond to an area which is coated with a mixture whose composition presents a concentration of the first and the second substances 20 and 22 which are constantly distributed upstream and downstream of the area.
- the concentration of the first substance of the upstream monolith 24 then being greater than that of the downstream monolith 26.
- the first substance 20 comprises a precious metal which may for example be platinum, palladium and / or radium.
- a nitrogen oxide trap 16 produced according to the invention thus allows, with an equal quantity of first substance 20, increase the storage capacity due to nitrogen oxide trap 16 at low temperature compared to a nitrogen oxide trap made according to the state of the art.
- the invention makes it possible to reduce significantly the overall amount of first substance 20 therefore precious metals, and therefore the manufacturing cost nitrogen oxide trap 16.
- the decrease in the amount of first substance 20 also reduces the dimensions of the support element 18 as well as those of the oxide trap of nitrogen 16, which reduces the overall size and weight of the exhaust line 14.
Abstract
L'invention concerne un dispositif de traitement (10) des gaz d'échappement (G) d'un moteur à combustion du type qui est inséré dans la ligne d'échappement (14) et qui comporte un élément de support (18) qui est traversé d'amont en aval par les gaz d'échappement (G) et qui est revêtu d'un mélange constitué d'au moins une première substance (20) qui permet l'oxydation du monoxyde d'azote en dioxyde d'azote et d'une seconde substance (22) qui permet le stockage du dioxyde d'azote, caractérisé en ce que la concentration de la première substance (20) dans le mélange est décroissante de l'amont vers l'aval de l'élément de structure (18) de façon à améliorer la capacité de stockage du dioxyde d'azote du dispositif de traitement (10), notamment lorsque la température des gaz d'échappement (G) est inférieure à 400°C. <IMAGE>The invention relates to a device (10) for treating exhaust gases (G) of a combustion engine of the type which is inserted into the exhaust line (14) and which comprises a support element (18) which is crossed from upstream to downstream by the exhaust gases (G) and which is coated with a mixture consisting of at least one first substance (20) which allows the oxidation of nitrogen monoxide to nitrogen dioxide and a second substance (22) which allows the storage of nitrogen dioxide, characterized in that the concentration of the first substance (20) in the mixture decreases from upstream to downstream of the element structure (18) so as to improve the nitrogen dioxide storage capacity of the treatment device (10), in particular when the temperature of the exhaust gases (G) is less than 400 ° C. <IMAGE>
Description
L'invention concerne un dispositif de traitement des gaz d'échappement d'un moteur à combustion.The invention relates to a gas treatment device. combustion engine exhaust.
L'invention concerne plus particulièrement un dispositif de traitement des gaz d'échappement d'un moteur à combustion, notamment d'un moteur diesel ou d'un moteur à essence à mélange pauvre.The invention relates more particularly to a device for exhaust gas treatment of a combustion engine, including a diesel or gasoline engine poor mixture.
De façon à réduire les émissions de substances polluantes telles que notamment les oxydes d'azote, les hydrocarbures imbrûlés et les oxydes de carbone, les dispositifs d'échappement sont équipés de manière connue de catalyseurs, notamment de catalyseurs de type "trois voies" de façon à provoquer la réaction des substances polluantes qui les traversent, pour diminuer les émissions nocives.In order to reduce emissions of polluting substances such as in particular nitrogen oxides, hydrocarbons unburnt and carbon oxides, exhaust systems are equipped in a known manner with catalysts, in particular with "three-way" catalysts so as to cause the reaction polluting substances passing through them, to reduce harmful emissions.
De tels catalyseurs peuvent permettre l'oxydation des hydrocarbures imbrûlés et des oxydes de carbone lorsque le mélange carburant/air est pauvre, c'est-à-dire que le rapport entre la masse de carburant et la masse d'air est inférieur à la richesse stoechiométrique.Such catalysts can allow the oxidation of unburnt hydrocarbons and carbon oxides when the fuel / air mixture is poor, i.e. the ratio between fuel mass and air mass is less than richness stoichiometric.
Ces catalyseurs permettent aussi la réduction des oxydes d'azote lorsque le mélange carburant/air est riche, c'est-à-dire que le rapport entre la masse de carburant et la masse d'air est supérieur à la richesse stoechiométrique.These catalysts also allow the reduction of oxides nitrogen when the fuel / air mixture is rich, i.e. that the ratio between the mass of fuel and the mass of air is greater than stoichiometric richness.
Cependant, de façon à diminuer la consommation de carburant, les moteurs à combustion fonctionnent fréquemment à mélange pauvre.However, in order to decrease the consumption of fuel, combustion engines frequently operate at poor mixture.
Ainsi, les conditions qui permettent la réduction des oxydes d'azote en substances moins polluantes sont rarement atteintes. De façon à limiter l'émission d'oxydes d'azote dans l'atmosphère, il est connu d'agencer dans la ligne d'échappement du moteur un dispositif de traitement des gaz d'échappement qui permet de stocker les oxydes d'azote lorsque le mélange air/carburant est pauvre et de les libérer lorsque le mélange air/carburant est riche. La libération des oxydes d'azote est rapide par rapport à la phase de stockage.Thus, the conditions which allow the reduction of nitrogen oxides to less polluting substances are rarely reached. In order to limit the emission of nitrogen oxides in the atmosphere it is known to arrange in the exhaust line of the engine an exhaust gas treatment device which allows nitrogen oxides to be stored when the mixture air / fuel is lean and release them when the mixture air / fuel is rich. The release of nitrogen oxides is rapid compared to the storage phase.
Un tel dispositif de traitement, appelé piège à oxydes d'azote, comporte notamment un mélange de substances qui recouvre un élément de structure du piège et qui permet de stocker les oxydes d'azote présents dans les gaz d'échappement et qui permet de les libérer périodiquement. La libération est réalisée par exemple par ajout d'une quantité prédéterminée d'une espèce réductrice dans les gaz d'échappement, de façon que les gaz d'échappement qui traversent le piège soient réducteurs.Such a treatment device, called an oxide trap nitrogen, includes a mixture of substances which covers a structural element of the trap which allows store the nitrogen oxides present in the exhaust gases and which allows them to be released periodically. Liberation is performed for example by adding a predetermined quantity of a reducing species in the exhaust gases, so that the exhaust gases passing through the trap are reducers.
Le stockage des oxydes d'azote consiste principalement à oxyder le monoxyde d'azote en dioxyde d'azote qui est alors stocké sous forme de nitrates (NO- 3) dans le piège à oxydes d'azote.The storage of nitrogen oxides mainly consists in oxidizing the nitrogen monoxide to nitrogen dioxide which is then stored in the form of nitrates (NO - 3 ) in the nitrogen oxide trap.
La réaction d'oxydation du monoxyde d'azote en dioxyde d'azote est principalement réalisée par une première substance du mélange qui recouvre l'élément de structure du piège. Cette substance comporte des métaux et notamment des métaux précieux.The oxidation reaction of nitrogen monoxide to dioxide nitrogen is mainly produced by a first substance of the mixture which covers the structural element of the trap. This substance contains metals and especially metals precious.
La première substance permet en partie le stockage du dioxyde d'azote sous forme de nitrates, mais cette étape est principalement due à une seconde substance du mélange qui recouvre le piège.The first substance partly allows the storage of nitrogen dioxide as nitrates but this step is mainly due to a second substance in the mixture which covers the trap.
La réaction d'oxydation présente une cinétique qui est lente à des températures basses, c'est-à-dire à des températures de l'ordre de 200 à 300 °C et qui augmente en fonction de la température.The oxidation reaction has kinetics which is slow at low temperatures, i.e. at temperatures of the order of 200 to 300 ° C and which increases depending on the temperature.
Ainsi, lorsque la température des gaz d'échappement qui traversent le piège à oxydes d'azote est trop faible, une quantité importante des oxydes d'azote produits par le moteur est rejetée dans l'atmosphère.So when the temperature of the exhaust gases that cross the nitrogen oxide trap is too low, a quantity significant amount of nitrogen oxides produced by the engine is rejected in the air.
Les normes concernant les émissions de substances polluantes sont de plus en plus strictes. Substance emission standards are becoming more and more stringent.
Or, dans certaines conditions de fonctionnement du moteur notamment lors de son démarrage à froid, les gaz d'échappement produits ne sont pas suffisamment chauds. L'efficacité du piège à oxydes d'azote, notamment sa capacité de stockage, est alors insuffisante.However, under certain engine operating conditions especially during cold start, the exhaust gases products are not hot enough. The effectiveness of the trap nitrogen oxides, including its storage capacity, is then insufficient.
Il est connu d'insérer dans la ligne d'échappement, en amont du piège à oxydes d'azote, un catalyseur appelé catalyseur d'amorçage qui permet l'oxydation du monoxyde d'azote en dioxyde d'azote. Ainsi, la quantité de monoxyde d'azote qui traverse le piège est réduite.It is known to insert into the exhaust line, upstream of the nitrogen oxide trap, a catalyst called catalyst priming which allows the oxidation of nitric oxide into nitrogen dioxide. So the amount of nitric oxide that crosses the trap is reduced.
Le piège permet alors le stockage du dioxyde d'azote formé dans le catalyseur d'amorçage ainsi que le dioxyde d'azote formé dans le piège à oxydes d'azote.The trap then allows the storage of nitrogen dioxide formed in the initiation catalyst as well as nitrogen dioxide formed in the nitrogen oxide trap.
Cependant, un tel catalyseur augmente l'encombrement ainsi que le coût du dispositif de traitement des gaz d'échappement.However, such a catalyst increases the size as well as the cost of the gas treatment device exhaust.
Une autre solution consiste à augmenter la quantité de métaux précieux, sur la structure du piège à oxydes d'azote. En effet, il est connu que l'augmentation de la quantité de métaux précieux diminue la température d'oxydation du monoxyde d'azote ce qui augmente la cinétique de la réaction d'oxydation, et par conséquent améliore la capacité de stockage du piège à basse température.Another solution is to increase the amount of precious metals, on the structure of the nitrogen oxide trap. In indeed it is known that increasing the amount of metals precious lowers the oxidation temperature of nitric oxide which increases the kinetics of the oxidation reaction, and by therefore improves the storage capacity of the low trap temperature.
Une telle solution, nécessitant plus de métaux précieux, augmente fortement le coût de fabrication du piège à oxydes d'azote.Such a solution, requiring more precious metals, greatly increases the cost of manufacturing the oxide trap nitrogen.
Dans le but de remédier à ces inconvénients, l'invention propose un dispositif de traitement des gaz d'échappement d'un moteur à combustion du type qui est inséré dans la ligne d'échappement et qui comporte un élément de support qui est traversé d'amont en aval par les gaz d'échappement et qui est revêtu d'un mélange constitué d'au moins une première substance qui permet l'oxydation du monoxyde d'azote en dioxyde d'azote et d'une seconde substance qui permet le stockage du dioxyde d'azote, caractérisé en ce que la concentration de la première substance dans le mélange est décroissante de l'amont vers l'aval de l'élément de structure de façon à améliorer la capacité de stockage du dioxyde d'azote du dispositif de traitement, notamment lorsque la température des gaz d'échappement est inférieure à 400°C.In order to remedy these drawbacks, the invention offers a device for treating the exhaust gases of a combustion engine of the type which is inserted in the line exhaust and which has a support member which is crossed from upstream to downstream by the exhaust gases and which is coated with a mixture of at least one first substance which allows the oxidation of nitrogen monoxide to nitrogen dioxide and of a second substance which allows the storage of dioxide nitrogen, characterized in that the concentration of the first substance in the mixture decreases from upstream to downstream of the structural element so as to improve the ability of storage of nitrogen dioxide from the treatment device, especially when the exhaust gas temperature is less than 400 ° C.
Selon d'autres caractéristiques de l'invention :
- l'élément de support est constitué d'un monolithe unique ;
- l'élément de support est constitué d'au moins un monolithe amont et d'un monolithe aval qui sont juxtaposés dans la ligne d'échappement ;
- l'élément de support comporte au moins une zone amont et une zone aval dont chacune est revêtue d'un mélange dont les concentrations de la première et de la seconde substances sont constantes d'amont en aval de chaque zone ;
- la zone amont correspond au monolithe amont et la zone aval correspond au monolithe aval ;
- un catalyseur d'amorçage est interposé dans la ligne d'échappement en amont de l'élément de support de façon à oxyder au moins partiellement le monoxyde d'azote qui le traverse;
- la première substance est un métal précieux ;
- le métal précieux comporte du platine ;
- le métal précieux comporte du palladium ;
- le métal précieux comporte du radium.
- the support element consists of a single monolith;
- the support element consists of at least one upstream monolith and one downstream monolith which are juxtaposed in the exhaust line;
- the support element comprises at least one upstream zone and one downstream zone, each of which is coated with a mixture of which the concentrations of the first and of the second substances are constant from upstream to downstream of each zone;
- the upstream zone corresponds to the upstream monolith and the downstream zone corresponds to the downstream monolith;
- a priming catalyst is interposed in the exhaust line upstream of the support element so as to at least partially oxidize the nitrogen monoxide which passes through it;
- the first substance is a precious metal;
- the precious metal contains platinum;
- the precious metal contains palladium;
- the precious metal contains radium.
D'autres caractéristiques et avantages de l'invention apparaítront à la lecture de la description détaillée qui suit pour la compréhension de laquelle on se reportera aux figures annexées parmi lesquelles :
- la figure 1 représente schématiquement une ligne d'échappement d'un moteur à combustion équipée d'un dispositif de traitement des gaz d'échappement d'un moteur à combustion réalisé selon l'état de la technique ;
- la figure 2 représente schématiquement un dispositif de traitement des gaz d'échappement d'un moteur à combustion réalisé selon un premier mode de réalisation de l'invention ;
- la figure 3 représente schématiquement une vue similaire à celle représentée à la figure précédente, le dispositif de traitement étant réalisé selon un second mode de réalisation.
- FIG. 1 schematically represents an exhaust line of a combustion engine equipped with a device for treating the exhaust gases of a combustion engine produced according to the state of the art;
- FIG. 2 schematically represents a device for treating the exhaust gases of a combustion engine produced according to a first embodiment of the invention;
- Figure 3 schematically shows a view similar to that shown in the previous figure, the processing device being produced according to a second embodiment.
On a représenté sur la figure 1 un dispositif de traitement
10 des gaz d'échappement G d'un moteur à combustion 12.FIG. 1 shows a
Le moteur 12 peut être un moteur diesel ou un moteur à
essence fonctionnant en mélange pauvre tel qu'un moteur à
essence à injection directe.The
Une ligne 14 d'échappement permet l'écoulement des gaz
G du moteur 12 vers l'atmosphère. Un dispositif de traitement 10
destiné à purifier les gaz d'échappement G est agencé à
l'intérieur de la ligne 14. Il se compose principalement d'un
catalyseur 16 situé dans une chambre.An
Le catalyseur 16 est constitué d'un élément de support 18
qui est traversé d'amont en aval par les gaz d'échappement G.The
L'élément de support 18 est revêtu d'un mélange. De façon
à permettre le stockage des oxydes d'azote, le mélange est
constitué d'une première substance 20, représentée sur les
figures par des disques noirs 20, qui permet principalement une
première étape d'oxydation du monoxyde d'azote en dioxyde
d'azote et d'une seconde substance 22, représentée sur les
figures par des cercles noirs 22, qui permet principalement une
deuxième étape d'adsorption du dioxyde d'azote. Dans la suite de
la description, le catalyseur 16 sera donc appelé piège à oxydes
d'azote 16.The
La première substance 20 comporte des métaux,
notamment des métaux précieux. La deuxième substance 22 est
quant à elle réalisée à base d'alcalin ou d'alcalino-terreux.The
Le catalyseur 16 peut aussi comporter une substance qui
permet de réduire les oxydes d'azote lorsque le mélange
air/carburant est riche.
Le catalyseur 16 peut encore comporter des substances
permettant d'oxyder des hydrocarbures imbrûlés, ainsi que les
oxydes de carbone présents dans les gaz d'échappement qui
circulent dans la ligne 14.
Conformément à la figure 1, les concentrations de la
première et la seconde substance 20, 22 dans le mélange sont
réparties de façon constante sur l'élément support 18 du piège
16.In accordance with Figure 1, the concentrations of
first and
Cependant, conformément à ce qui a été décrit
précédemment, un tel un dispositif de traitement 10 ne présente
pas une capacité de stockage suffisante des oxydes d'azote à
basse température.However, in accordance with what has been described
previously, such a
L'invention propose que la concentration de la première
substance 20 dans le mélange soit décroissante de l'amont vers
l'aval de l'élément de structure 18, de façon à améliorer la
capacité de stockage des oxydes d'azote du dispositif de
traitement 10, notamment lorsque la température des gaz
d'échappement est inférieure à 400°C.The invention proposes that the concentration of the
Ainsi, si on conserve la quantité globale de première
substance 20 dans le piège à oxydes d'azote 16 par rapport un
piège à oxydes d'azote réalisé selon l'état de la technique, la
concentration de la première substance 20 en amont du piège à
oxydes d'azote 16 selon l'invention est supérieure à la
concentration homogène, c'est-à-dire constante, de la première
substance d'un piège à oxydes d'azote selon l'état de technique.So if we keep the overall amount of
La variation de la concentration de la première substance provoque une variation inverse de la concentration de la seconde substance.The variation in the concentration of the first substance causes an inverse variation in the concentration of the second substance.
L'augmentation de la concentration en amont du piège diminue la température d'oxydation du monoxyde d'azote ce qui augmente, le rendement de la réaction d'oxydation du monoxyde d'azote en dioxyde d'azote à basse température.Increasing the concentration upstream of the trap decreases the oxidation temperature of nitrogen monoxide which increases, the yield of the monoxide oxidation reaction nitrogen to nitrogen dioxide at low temperatures.
Ainsi, la capacité de stockage des oxydes d'azote dans le
piège 16 est globalement augmentée. Thus, the storage capacity of nitrogen oxides in the
Dans la partie aval du piège à oxydes d'azote 16 selon
l'invention, la concentration de la première substance 20 est
inférieure à la concentration de la première substance d'un piège
à oxydes d'azote selon l'état la technique.In the downstream part of the
Une telle variation des concentrations de la première et de la seconde substance n'influence quasiment pas la deuxième étape d'adsorption du dioxyde d'azote puisque ce phénomène dépend principalement du dioxyde formé, c'est-à-dire que la quasi-totalité du dioxyde formé est adsorbée, même à des températures basses.Such a variation in the concentrations of the first and the second substance hardly influences the second nitrogen dioxide adsorption step since this phenomenon mainly depends on the dioxide formed, i.e. the almost all of the dioxide formed is adsorbed, even at low temperatures.
La figure 2 représente un élément de support 18 constitué
d'un monolithe unique qui est revêtu d'un mélange dont la
concentration de la première substance 20 est supérieure en
amont qu'en aval du piège à oxydes d'azote 16. La variation de la
concentration de la première substance 20 est régulière entre
l'amont et l'aval de l'élément de support 18. Cette solution est
avantageuse car le dioxyde d'azote est formé à proximité des
zones dans lesquelles le dioxyde d'azote est adsorbé que ce qui
favorise cette étape.FIG. 2 represents a
Selon une variante, la variation de la concentration de la
première substance 20 se fait par paliers. Ainsi, l'élément de
support 18 comporte plusieurs zones. La concentration de la
première substance 20 d'une zone est toujours inférieure à la
concentration de la première substance 20 de la zone adjacente
située en amont.Alternatively, varying the concentration of the
Selon un second mode de réalisation, conformément à la
figure 3, l'élément de support 18 peut être constitué d'un
monolithe amont 24 et d'un monolithe aval 26 qui sont juxtaposés
dans la ligne d'échappement 14 du moteur à combustion 12.According to a second embodiment, in accordance with the
FIG. 3, the
Chaque monolithe amont 24 et aval 26 peut correspondre à
une zone qui est revêtue d'un mélange dont la composition
présente une concentration de la première et de la seconde
substances 20 et 22 qui sont reparties de façon constante
d'amont en aval de la zone. La concentration de la première
substance du monolithe amont 24 étant alors supérieure à celle
du monolithe aval 26.Each upstream 24 and downstream 26 monolith can correspond to
an area which is coated with a mixture whose composition
presents a concentration of the first and the
La première substance 20 comporte un métal précieux qui
peut être par exemple du platine, du palladium et/ou du radium.The
De façon à augmenter encore la capacité de stockage du
piège à oxydes d'azote 16, il est avantageux d'interposer dans la
ligne d'échappement 14 en amont de l'élément de support 18 un
catalyseur d'amorçage, non représenté, pour oxyder partiellement
le monoxyde d'azote qui le traverse.In order to further increase the storage capacity of the
Un piège à oxydes d'azote 16 réalisé selon l'invention
permet ainsi, à quantité de première substance 20 égale,
d'augmenter la capacité de stockage dû piège à oxydes d'azote
16 à faible température par rapport à un piège à oxydes d'azote
réalisé selon l'état de la technique.A
Pour des capacités similaires, l'invention permet de réduire
de façon importante la quantité globale de première substance 20
donc de métaux précieux, et par conséquent le coût de fabrication
du piège à oxydes d'azote 16. La diminution de la quantité de
première substance 20 permet aussi de réduire les dimensions de
l'élément de support 18 ainsi que celles du piège à oxydes
d'azote 16, ce qui réduit l'encombrement et le poids global de la
ligne d'échappement 14.For similar capacities, the invention makes it possible to reduce
significantly the overall amount of
Claims (10)
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FR0016862A FR2818688B1 (en) | 2000-12-22 | 2000-12-22 | DEVICE FOR TREATING THE EXHAUST GASES OF A COMBUSTION ENGINE |
| FR1686200 | 2000-12-22 | ||
| FR0016862 | 2000-12-22 |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| EP1225312A2 true EP1225312A2 (en) | 2002-07-24 |
| EP1225312A3 EP1225312A3 (en) | 2004-05-19 |
| EP1225312B1 EP1225312B1 (en) | 2006-03-01 |
Family
ID=8858072
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| EP20010403246 Expired - Lifetime EP1225312B1 (en) | 2000-12-22 | 2001-12-14 | Device for treating an exhaust gas from a combustion engine |
Country Status (3)
| Country | Link |
|---|---|
| EP (1) | EP1225312B1 (en) |
| DE (1) | DE60117509T2 (en) |
| FR (1) | FR2818688B1 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP1273773A3 (en) * | 2001-07-02 | 2003-11-12 | Toyota Jidosha Kabushiki Kaisha | Exhaust gas purifying system for an internal combustion engine |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0716876A1 (en) * | 1994-12-16 | 1996-06-19 | Toyota Jidosha Kabushiki Kaisha | Catalyst for purifying exhaust gases |
| JPH08215545A (en) * | 1995-02-16 | 1996-08-27 | Kobe Steel Ltd | Method for removing nitrogen monoxide |
| WO1998010177A1 (en) * | 1996-09-05 | 1998-03-12 | Volkswagen Aktiengesellschaft | Exhaust fume purification process for an internal combustion engine |
| EP1033161A1 (en) * | 1999-02-25 | 2000-09-06 | DORNIER GmbH | Process and device for adsorption of nitrogen oxides contained in a gas |
-
2000
- 2000-12-22 FR FR0016862A patent/FR2818688B1/en not_active Expired - Fee Related
-
2001
- 2001-12-14 DE DE2001617509 patent/DE60117509T2/en not_active Expired - Lifetime
- 2001-12-14 EP EP20010403246 patent/EP1225312B1/en not_active Expired - Lifetime
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0716876A1 (en) * | 1994-12-16 | 1996-06-19 | Toyota Jidosha Kabushiki Kaisha | Catalyst for purifying exhaust gases |
| JPH08215545A (en) * | 1995-02-16 | 1996-08-27 | Kobe Steel Ltd | Method for removing nitrogen monoxide |
| WO1998010177A1 (en) * | 1996-09-05 | 1998-03-12 | Volkswagen Aktiengesellschaft | Exhaust fume purification process for an internal combustion engine |
| EP1033161A1 (en) * | 1999-02-25 | 2000-09-06 | DORNIER GmbH | Process and device for adsorption of nitrogen oxides contained in a gas |
Non-Patent Citations (1)
| Title |
|---|
| PATENT ABSTRACTS OF JAPAN vol. 1996, no. 12, 26 décembre 1996 (1996-12-26) & JP 08 215545 A (KOBE STEEL LTD), 27 août 1996 (1996-08-27) * |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP1273773A3 (en) * | 2001-07-02 | 2003-11-12 | Toyota Jidosha Kabushiki Kaisha | Exhaust gas purifying system for an internal combustion engine |
Also Published As
| Publication number | Publication date |
|---|---|
| FR2818688A1 (en) | 2002-06-28 |
| FR2818688B1 (en) | 2003-06-27 |
| EP1225312A3 (en) | 2004-05-19 |
| EP1225312B1 (en) | 2006-03-01 |
| DE60117509T2 (en) | 2006-08-31 |
| DE60117509D1 (en) | 2006-04-27 |
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