EP1225312B1 - Einrichtung zur Abgasnachbehandlung von Verbrennungsmotoren - Google Patents

Einrichtung zur Abgasnachbehandlung von Verbrennungsmotoren Download PDF

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Publication number
EP1225312B1
EP1225312B1 EP20010403246 EP01403246A EP1225312B1 EP 1225312 B1 EP1225312 B1 EP 1225312B1 EP 20010403246 EP20010403246 EP 20010403246 EP 01403246 A EP01403246 A EP 01403246A EP 1225312 B1 EP1225312 B1 EP 1225312B1
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EP
European Patent Office
Prior art keywords
substance
treatment apparatus
upstream
downstream
nitrogen
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
EP20010403246
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English (en)
French (fr)
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EP1225312A3 (de
EP1225312A2 (de
Inventor
Shanin Hodjati
Najar Moral
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Renault SAS
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Renault SAS
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Publication of EP1225312A3 publication Critical patent/EP1225312A3/de
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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
    • 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
    • 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 device for treating the exhaust gases of a combustion engine.
  • the invention relates more particularly to a device for treating the exhaust gases of a combustion engine, in particular a diesel engine or a lean gasoline engine.
  • the exhaust systems are equipped in the known manner with catalysts, in particular catalysts of the "three-way" type of catalyst. to cause the reaction of polluting substances that pass through them, to reduce harmful emissions.
  • Such catalysts can allow the oxidation of unburned hydrocarbons and oxides of carbon when the fuel / air mixture is poor, that is to say that the ratio between the mass of fuel and the air mass is less than the stoichiometric richness.
  • These catalysts also allow the reduction of nitrogen oxides when the fuel / air mixture is rich, that is to say that the ratio between the fuel mass and the air mass is greater than the stoichiometric richness.
  • Such a treatment device (see EP 1 033 161), called a nitrogen oxide trap, comprises in particular a mixture of substances which covers a structural element of the trap and which makes it possible to store the nitrogen oxides present in the gases of escape and that allows to release them periodically.
  • the release is carried out for example by adding a predetermined amount of a reducing species in the exhaust gas, so that the exhaust gas passing through the trap are reducing.
  • Nitrogen oxides consists primarily of oxidation of nitrogen monoxide to nitrogen dioxide, which is then stored as nitrates (NO - 3 ) in the nitrogen oxide trap.
  • the oxidation reaction of nitrogen monoxide to nitrogen dioxide is mainly carried out by a first substance of the mixture which covers the structural element of the trap. This substance contains metals and especially precious metals.
  • the first substance partly allows the storage of nitrogen dioxide in the form of nitrates, but this step is mainly due to a second substance of the mixture which covers the trap.
  • the oxidation reaction has slow kinetics at low temperatures, i.e. at temperatures of the order of 200 to 300 ° C and increases with temperature.
  • the trap then allows the storage of the nitrogen dioxide formed in the priming catalyst as well as the 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. Indeed, it is known that increasing the amount of precious metals decreases the oxidation temperature of nitric oxide which increases the kinetics of the oxidation reaction, and therefore improves the storage capacity of the trap. low temperature.
  • the invention proposes a device for treating the exhaust gases of a combustion engine of the type that is inserted in the exhaust line and which comprises a support element which is traversed by upstream downstream by the exhaust gas and which is coated with a mixture of at least one first substance which allows the oxidation of nitrogen monoxide to nitrogen dioxide and a second substance which allows the dioxide storage nitrogen, characterized in that the concentration of the first substance in the mixture is decreasing from upstream to downstream of the structural element so as to improve the storage capacity of the nitrogen dioxide of the treatment device , especially when the temperature of the exhaust gas is below 400 ° C.
  • FIG. 1 shows a device 10 for treating the exhaust gases G of a combustion engine 12.
  • the engine 12 may be a diesel engine or a gasoline engine operating in a lean mixture such as a direct injection gasoline engine.
  • An exhaust line 14 allows the flow of gases G from the engine 12 to the atmosphere.
  • a treatment device 10 for purifying the exhaust gas G is arranged inside the line 14. It consists mainly of a catalyst 16 located in a chamber.
  • the catalyst 16 consists of a support element 18 which is traversed from upstream to downstream by the exhaust gases G.
  • the support member 18 is coated with a mixture.
  • the mixture consists of a first substance 20, represented in the figures by black disks 20, which mainly allows a first step of oxidation of nitrogen monoxide to carbon dioxide.
  • the catalyst 16 will therefore be called a nitrogen oxide trap 16.
  • the first substance comprises metals, especially precious metals.
  • the second substance 22 is based on alkali or alkaline earth.
  • the catalyst 16 may also include a substance which makes it possible to reduce the nitrogen oxides when the air / fuel mixture is rich.
  • the catalyst 16 may also comprise substances for oxidizing unburned hydrocarbons, as well as the oxides of carbon present in the exhaust gas flowing in line 14.
  • the concentrations of the first and the second substance 20, 22 in the mixture are distributed in a constant manner on the support element 18 of the trap 16.
  • such a treatment device 10 does not have a sufficient storage capacity of nitrogen oxides at low temperature.
  • the invention proposes that the concentration of the first substance in the mixture is decreasing from upstream to downstream of the structural element 18, so as to improve the storage capacity of the nitrogen oxides of the treatment device. 10, especially when the temperature of the exhaust gas is less than 400 ° C.
  • the concentration of the first substance 20 upstream of the trap nitrogen oxide 16 according to the invention is greater than the homogeneous concentration, that is to say constant, of the first substance of a nitrogen oxide trap according to the state of the art.
  • the change in the concentration of the first substance causes an inverse variation in the concentration of the second substance.
  • the increase in the concentration upstream of the trap decreases the oxidation temperature of the nitric oxide which increases the yield of the oxidation reaction of nitric oxide to nitrogen dioxide at low temperature.
  • the storage capacity of the nitrogen oxides in the trap 16 is generally increased.
  • the concentration of the first substance 20 is lower than the concentration of the first substance of a nitrogen oxide trap according to the state of the art.
  • FIG. 2 shows a support element 18 consisting of a single monolith which is coated with a mixture whose concentration of the first substance 20 is greater upstream than downstream of the nitrogen oxide trap 16.
  • the variation of the concentration of the first substance 20 is regular between the upstream and the downstream of the support element 18. This solution is advantageous because the nitrogen dioxide is formed near the zones in which the nitrogen dioxide is adsorbed than what promotes this step.
  • the variation of the concentration of the first substance 20 is in steps.
  • the support element 18 has several zones. The concentration of the first substance in one zone is always less than the concentration of the first substance in the adjacent upstream zone.
  • the support element 18 may consist of an upstream monolith 24 and a downstream monolith 26 which are juxtaposed in the exhaust line 14 of the combustion engine 12 .
  • Each upstream monolith 24 and downstream 26 may correspond to an area which is coated with a mixture whose composition has a concentration of the first and second substances 20 and 22 which are distributed consistently upstream downstream of the zone. .
  • 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 be for example platinum, palladium and / or radium.
  • a priming catalyst not shown, for partially oxidize the nitric oxide that passes through it.
  • a nitrogen oxide trap 16 produced according to the invention thus makes it possible, for an amount of first substance equal to 20, to increase the storage capacity of the nitrogen oxide trap 16 at a low temperature compared to a trap for oxides of nitrogen. nitrogen produced according to the state of the art.
  • the invention makes it possible to significantly reduce the overall quantity of the first substance, and therefore of precious metals, and consequently the manufacturing cost of the nitrogen oxide trap 16.
  • the decrease in the amount of the first substance 20 also makes it possible to reduce the dimensions of the support element 18 as well as those of the nitrogen oxide trap 16, which reduces the space requirement and the overall weight of the exhaust line 14.

Landscapes

  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Health & Medical Sciences (AREA)
  • Toxicology (AREA)
  • Exhaust Gas After Treatment (AREA)

Claims (10)

  1. Vorrichtung (10) zur Behandlung von Abgasen (G) eines Verbrennungsmotors (12) von der Art, welche in die Abgasleitung (14) eingeführt ist und welche ein Trägerelement (18) aufweist, welches durch die Abgase (G) von stromaufwärts nach stromabwärts durchquert wird und welches mit einer Mischung überzogen ist, welche gebildet ist aus mindestens einer ersten Substanz (20), welche die Oxidation des Stickstoffmonoxids in Stickstoffdioxid erlaubt, und einer zweiten Substanz (22), welche die Speicherung von Stickstoffdioxid erlaubt, dadurch gekennzeichnet, dass die Konzentration der ersten Substanz (20) in der Mischung von stromaufwärts in Richtung stromabwärts des Strukturelements (18) (bzw. Trägerelement) in solche einer Weise abnehmend ist, um die Speicherkapazität von Stickstoffdioxid der Behandlungsvorrichtung (10) zu verbessern, insbesondere wenn die Temperatur der Abgase (G) niedriger als 400° C ist.
  2. Behandlungsvorrichtung (10) nach dem vorangegangenen Anspruch, dadurch gekennzeichnet, dass das Trägerelement (18) aus einem einzigen Monolithen gebildet ist.
  3. Vorrichtung (10) zur Behandlung von Abgasen nach Anspruch 1, dadurch gekennzeichnet, dass das Trägelement (18) aus mindestens einem Monolithen (24) stromaufwärts und einem Monolithen (26) stromabwärts gebildet ist, welche in der Abgasleitung (14) nebeneinanderliegen.
  4. Behandlungsvorrichtung (10) nach irgendeinem der vorangegangenen Ansprüche, dadurch gekennzeichnet, dass das Trägerelement (18) mindestens eine Zone stromaufwärts und eine Zone stromabwärts aufweist, von denen jede mit einer Mischung überzogen ist, deren Konzentrationen der ersten und der zweiten Substanz (22) von stromaufwärts nach stromabwärts von jeder Zone konstant sind.
  5. Behandlungsvorrichtung (10) nach Anspruch 4 in Kombination mit Anspruch 3, dadurch gekennzeichnet, dass die Zone stromaufwärts dem Monolithen (24) stromaufwärts entspricht, und dass die Zone stromabwärts dem Monolithen (26) stromabwärts entspricht.
  6. Behandlungsvorrichtung (10) nach irgendeinem der vorangegangenen Ansprüche, dadurch gekennzeichnet, dass ein Vor-Katalysator in die Abgasleitung stromaufwärts vom Trägerelement 18 in einer Weise zwischengesetzt ist, um mindestens teilweise das Stickstoffmonoxid, welches ihn durchquert, zu oxidieren.
  7. Behandlungsvorrichtung (10) nach irgendeinem der vorangegangenen Ansprüche, dadurch gekennzeichnet, dass die erste Substanz (20) ein Edelmetall ist.
  8. Behandlungsvorrichtung (10) nach dem vorangegangenen Anspruch, dadurch gekennzeichnet, dass das Edelmetall Platin umfasst.
  9. Behandlungsvorrichtung (10) nach einem der Ansprüche 7 oder 8, dadurch gekennzeichnet, dass das Edelmetall Palladium umfasst.
  10. Behandlungsvorrichtung (10) nach einem der Ansprüche 7 bis 9, dadurch gekennzeichnet, dass das Edelmetall Radium umfasst.
EP20010403246 2000-12-22 2001-12-14 Einrichtung zur Abgasnachbehandlung von Verbrennungsmotoren Expired - Lifetime EP1225312B1 (de)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
FR0016862A FR2818688B1 (fr) 2000-12-22 2000-12-22 Dispositif de traitement des gaz d'echappement d'un moteur a combustion
FR0016862 2000-12-22
FR1686200 2000-12-22

Publications (3)

Publication Number Publication Date
EP1225312A2 EP1225312A2 (de) 2002-07-24
EP1225312A3 EP1225312A3 (de) 2004-05-19
EP1225312B1 true EP1225312B1 (de) 2006-03-01

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EP20010403246 Expired - Lifetime EP1225312B1 (de) 2000-12-22 2001-12-14 Einrichtung zur Abgasnachbehandlung von Verbrennungsmotoren

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EP (1) EP1225312B1 (de)
DE (1) DE60117509T2 (de)
FR (1) FR2818688B1 (de)

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2003013732A (ja) * 2001-07-02 2003-01-15 Toyota Motor Corp 内燃機関の排気浄化装置

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP3358766B2 (ja) * 1994-12-16 2002-12-24 トヨタ自動車株式会社 排ガス浄化用触媒
JPH08215545A (ja) * 1995-02-16 1996-08-27 Kobe Steel Ltd 一酸化窒素の除去方法
WO1998010177A1 (de) * 1996-09-05 1998-03-12 Volkswagen Aktiengesellschaft Abgasreinigungsverfahren für eine brennkraftmaschine
DE19908023A1 (de) * 1999-02-25 2000-08-31 Dornier Gmbh Verfahren und Element zur Speicherung von in einem Gas enthaltenen Stickoxiden

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Publication number Publication date
DE60117509T2 (de) 2006-08-31
EP1225312A3 (de) 2004-05-19
EP1225312A2 (de) 2002-07-24
FR2818688A1 (fr) 2002-06-28
FR2818688B1 (fr) 2003-06-27
DE60117509D1 (de) 2006-04-27

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