GB2409656A - NOx storage catalytic converter, having storage materials with low temperature-dependency - Google Patents

NOx storage catalytic converter, having storage materials with low temperature-dependency Download PDF

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Publication number
GB2409656A
GB2409656A GB0427890A GB0427890A GB2409656A GB 2409656 A GB2409656 A GB 2409656A GB 0427890 A GB0427890 A GB 0427890A GB 0427890 A GB0427890 A GB 0427890A GB 2409656 A GB2409656 A GB 2409656A
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GB
United Kingdom
Prior art keywords
catalytic converter
component
barium
proportion
ceroxide
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.)
Granted
Application number
GB0427890A
Other versions
GB0427890D0 (en
GB2409656B (en
Inventor
Asmus Carstensen
Markus Paulovsky
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Volkswagen AG
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Volkswagen AG
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Filing date
Publication date
Application filed by Volkswagen AG filed Critical Volkswagen AG
Publication of GB0427890D0 publication Critical patent/GB0427890D0/en
Publication of GB2409656A publication Critical patent/GB2409656A/en
Application granted granted Critical
Publication of GB2409656B publication Critical patent/GB2409656B/en
Expired - Fee Related legal-status Critical Current
Anticipated expiration legal-status Critical

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Classifications

    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01NGAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • F01N3/0807Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents
    • F01N3/0828Exhaust 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
    • F01N3/0842Nitrogen oxides
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01DSEPARATION
    • B01D53/00Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34Chemical or biological purification of waste gases
    • B01D53/92Chemical or biological purification of waste gases of engine exhaust gases
    • B01D53/94Chemical or biological purification of waste gases of engine exhaust gases by catalytic processes
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01DSEPARATION
    • B01D53/00Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34Chemical or biological purification of waste gases
    • B01D53/92Chemical or biological purification of waste gases of engine exhaust gases
    • B01D53/94Chemical or biological purification of waste gases of engine exhaust gases by catalytic processes
    • B01D53/9404Removing only nitrogen compounds
    • B01D53/9409Nitrogen oxides
    • B01D53/9413Processes characterised by a specific catalyst
    • B01D53/9422Processes characterised by a specific catalyst for removing nitrogen oxides by NOx storage or reduction by cyclic switching between lean and rich exhaust gases (LNT, NSC, NSR)
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01JCHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/02Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the alkali- or alkaline earth metals or beryllium
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01JCHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/10Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of rare earths
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01JCHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J35/00Catalysts, in general, characterised by their form or physical properties
    • B01J35/19Catalysts containing parts with different compositions
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01NGAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N13/00Exhaust or silencing apparatus characterised by constructional features ; Exhaust or silencing apparatus, or parts thereof, having pertinent characteristics not provided for in, or of interest apart from, groups F01N1/00 - F01N5/00, F01N9/00, F01N11/00
    • F01N13/009Exhaust or silencing apparatus characterised by constructional features ; Exhaust or silencing apparatus, or parts thereof, having pertinent characteristics not provided for in, or of interest apart from, groups F01N1/00 - F01N5/00, F01N9/00, F01N11/00 having two or more separate purifying devices arranged in series
    • F01N13/0097Exhaust or silencing apparatus characterised by constructional features ; Exhaust or silencing apparatus, or parts thereof, having pertinent characteristics not provided for in, or of interest apart from, groups F01N1/00 - F01N5/00, F01N9/00, F01N11/00 having two or more separate purifying devices arranged in series the purifying devices are arranged in a single housing
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01NGAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01NGAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • F01N3/0807Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents
    • F01N3/0814Exhaust 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
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01DSEPARATION
    • B01D2255/00Catalysts
    • B01D2255/20Metals or compounds thereof
    • B01D2255/204Alkaline earth metals
    • B01D2255/2042Barium
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01DSEPARATION
    • B01D2255/00Catalysts
    • B01D2255/20Metals or compounds thereof
    • B01D2255/206Rare earth metals
    • B01D2255/2065Cerium

Landscapes

  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Combustion & Propulsion (AREA)
  • Materials Engineering (AREA)
  • Organic Chemistry (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Health & Medical Sciences (AREA)
  • Biomedical Technology (AREA)
  • Environmental & Geological Engineering (AREA)
  • Analytical Chemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Catalysts (AREA)
  • Exhaust Gas After Treatment (AREA)
  • Exhaust Gas Treatment By Means Of Catalyst (AREA)

Abstract

A NOx storage catalytic converter for the exhaust gas of an internal combustion engine, in particular a diesel engine or Otto engine capable of lean running, having storage materials with low temperature-dependency, resulting in minimal NOx desorption during engine operation. The low temperature-dependency is obtained by proportioning the storage catalyst components, being ceroxide and a barium salt and/or barium oxide, in a way where the proportion of the barium component in the outlet region of the catalytic converter is greater than the proportion of the ceroxide component.

Description

DESCRIPTION
NOx Storage Catalytic converter The invention relates to an NOx storage catalytic converter for the exhaust gas of an internal combustion engine, in particular a diesel engine or Otto engine capable of lean running, in accordance with the preamble of claim 1.
Current NOx storage catalytic converters for diesel combustion engines or other internal combustion engines which are capable of lean running contain storage components for the purpose of storing the nitrogen oxides produced during lean running, these storage components being from the group of oxides of alkaline metals and alkaline earth metals, in particular barium oxide and ceroxide, as described e.g. in DE 198 38 282 Al.
One problem with such catalytic converters, however, is the highly temperature- dependent storage behaviour of the storage materials. Thus during engine operation at exhaust gas temperatures of 240 C, which are typical for diesel in the partial load range, NOx desorption occurs in such catalytic converters even in lean running. It is observed that with each temperature wave which passes through the catalytic converter, i.e. through the monolith, after each regeneration, nitrogen oxides are released in the lean phase. Thus the temperature wave in the monolith reaches about 320 C. The temperature wave in the catalytic converter is triggered by the high availability of oxidizable components so that, after each rich phase, exothermic reactions take place on the catalyst, wherein the increase in temperature causes nitrogen oxides to be discharged.
It is therefore the object of the invention to create a catalytic converter whose NOx discharge in the lean running phase is minimised.
This object is achieved by means of an NOx storage catalytic converter in accordance with claim 1. Preferred embodiments of the invention are the subject of the subordinate claims.
The NOx storage catalytic converter in accordance with the invention comprises the components ceroxide and a barium salt and/or a barium oxide, wherein in the outlet region of the catalytic converter the proportion of the barium component is greater than the proportion of the ceroxide component. In the inlet region of the catalytic converter the proportion of the ceroxide component is preferably greater than the proportion of the barium component.
In a preferred embodiment the proportion of the barium component increases from the catalytic converter inlet side to the catalytic converter outlet side, while the ceroxide component decreases over this region. The decrease and/or increase preferably progresses in a continuous manner.
In a preferred embodiment the catalyst components are disposed in a monolith, wherein the distribution of the components over the monolith, i.e. in the through- flow direction of the exhaust gas, is as described above.
In a further preferred embodiment the catalyst components are disposed in two monoliths disposed one behind the other. Preferably in the first monolith the proportion of the ceroxide component exceeds that of the barium component, while in the second monolith the proportion of the barium component exceeds that of the ceroxide component.
The barium component is preferably formed by barium oxide and/or barium carbonate.
The catalytic converter in accordance with the invention can be used in diesel engines or Otto engines capable of lean running.
Preferred embodiments of the invention are explained hereinunder with the aid of the drawings in which: Fig. I is a diagram to explain the thermodesorption during the lean phase lean running over time, Fig. 2 shows a first embodiment of the storage catalytic converter in accordance with the invention, and Fig. 3 shows a second embodiment of the storage catalytic converter in accordance with the invention.
Fig. I serves to explain the thermo-desorption in an NOx storage catalytic converter over time. Rich phases A, which serve to regenerate the catalyst, and lean phases B are shown. Thus curve I shows the course of the air ratio as a function of the time t. Curve II shows the NOx content in ppm of the exhaust gas of an internal combustion engine prior to entry into the NOx storage catalytic converter. It can clearly be seen that the NOx content of the exhaust gas behaves in synchronism with the course of \. Curve III in Fig. I shows the NOx content of the exhaust gas downstream of the catalytic converter. The desorption peaks DPF caused by the rich phase can clearly be seen. Furthermore, curve 111 shows thermo- desorption peaks DPM during the lean phase, in other words, during the lean phase the storage capability of the catalytic converter decreases and the storage of NOx is detrimentally affected. This behaviour of the catalytic converter is based on the fact that the combustion of an excess of reducing agents during the rich phase results in an excessively high solids temperature in the storage material of the catalytic converter during the lean phase. This leads to a reduction in the storage capability of the catalyst material, which is manifested as thermo- desorption during the lean phase. The connection can be seen from the curves IV and V which illustrate the course of the temperature T of the exhaust gas upstream of the catalytic converter (curve TV) and the course of the temperature T of the exhaust gas downstream of the catalytic converter. It can be seen that the temperature peak of the curve 1V at the catalytic converter output appears flattened and with a time delay (curve V) by reason of the rich phase.
From this it can be concluded that a temperature wave moves through the solid body of the catalytic converter.
The storage material responsible for this effect is ceroxide, which at about 270 C can no longer store the nitrogen oxides in the form of carnitrates. In order to counteract temperature-dependency, barium oxide and/or barium carbonate is used as a second storage material in addition to the ceroxide component, which barium oxide or carbonate only begins to become unstable at about 350 C and can thus still absorb NOx during partial load operation.
Fig. 2 shows a first embodiment of the NOx storage catalytic converter I in accordance with the invention, which has an exhaust gas inlet side 2 and an exhaust gas outlet side 3, wherein exhaust gas flows through the catalytic converter in the direction of the arrows. The catalytic converter has a monolith 4, the ceroxide component proportion of which at the inlet side is greater than that of the barium component. At the outlet side this ratio is reversed; at that location the proportion of the barium component is greater than that of the ceroxide component. This is shown schematically by the arrows 5 and 6 in the monolith, wherein the arrow 5 illustrates and depicts the proportion of the ceroxide component and the arrow 6 the proportion of the barium component. In particular the proportion of the respective component changes continuously over the length of the monolith 4.
Fig. 3 shows a second embodiment of the NOx storage catalytic converter 1 in accordance with the invention, having an inlet side 2 and an outlet side 3. The catalytic converter I includes a first monolith 7 and a second monolith 8 disposed downstream thereof in the direction of exhaust gas flow. In this case the proportion of the ceroxide component, shown by the arrow 9, exceeds that of the barium component, symbolised by the arrow 10. In the second monolith the ratio is reversed, in that case the proportion of the barium component, illustrated by the arrow 12, exceeds that of the ceroxide component 1 1.
By these features it is ensured that with a temperature wave running through the solid body of the catalytic converter by reason of the rich phase, thermo desorption of nitrogen oxides during the lean phase is minimised or prevented.
REFERENCE LIST
t time T exhaust gas temperature air ratio (fuel/air ratio) A rich phase B lean phase I as a function of time t 1I NOx content upstream of the catalytic converter as a function of time t III NOx content downstream of the catalytic converter as a function of time t IV exhaust gas temperature upstream of the catalytic converter as a function of time V exhaust gas temperature downstream of the catalytic converter as a function of time DPF desorption peak in the rich phase DPM desorption peak in the lean phase 1 NOx storage catalytic converter 2 inlet side 3 outlet side 4 monolith proportion of car-component 6 proportion of barium component 7 first monolith second monolith 9 proportion of car-component in the first monolith proportion of barium- component in the first monolith 11 proportion of car-component in the second monolith 12 proportion of barium-component in the second monolith

Claims (9)

1 NOx storage catalytic converter for an internal combustion engine having the storage catalyst components ceroxide and a barium salt and/or barium oxide, characterized in that in the catalytic converter outlet region the proportion of the barium component is greater than the proportion of the ceroxide component.
2 Catalytic converter as claimed in claim 1, characterized in that in the catalytic converter inlet region the proportion of the ceroxide component is greater than the proportion of the barium component.
3 Catalytic converter as claimed in claim 1 or 2, characterized in that the proportion of barium component increases from the catalytic converter inlet side towards the catalytic converter outlet side and the ceroxide component decreases over this region.
4 Catalytic converter as claimed in claim 3, characterized in that the decrease and/or increase progresses in a continuous manner.
Catalytic converter as claimed in any one of the preceding claims, characterized in that the catalyst components are disposed in a monolith.
6 Catalytic converter as claimed in any one of claims I or 2, characterized in that the catalyst components are disposed in two monoliths disposed one behind the other.
7 Catalytic converter as claimed in claim 6, characterized in that in the first monolith the proportion of the ceroxide component exceeds that of the barium component and in the second monolith the proportion of the barium component exceeds that of the ceroxide component.
8 Catalytic converter as claimed in any one of the preceding claims, characterized in that the barium component is formed by barium oxide and/or barium carbonate.
9 Catalytic converter as claimed in any one of the preceding claims, characterized in that the internal combustion engine is a diesel engine or an Otto engine which is capable of lean running.
GB0427890A 2003-12-31 2004-12-21 NOx storage catalytic converter Expired - Fee Related GB2409656B (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
DE10361793A DE10361793A1 (en) 2003-12-31 2003-12-31 NOx storage catalytic converter

Publications (3)

Publication Number Publication Date
GB0427890D0 GB0427890D0 (en) 2005-01-19
GB2409656A true GB2409656A (en) 2005-07-06
GB2409656B GB2409656B (en) 2007-05-23

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Family Applications (1)

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GB0427890A Expired - Fee Related GB2409656B (en) 2003-12-31 2004-12-21 NOx storage catalytic converter

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DE (1) DE10361793A1 (en)
GB (1) GB2409656B (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2007009679A2 (en) * 2005-07-22 2007-01-25 Umicore Ag & Co. Kg Method for the reactivation of thermally aged nitrogen oxide storage catalytic converters

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE19838282A1 (en) * 1998-08-24 2000-03-02 Degussa Nitrogen oxide storage material and the nitrogen oxide storage catalyst produced therefrom
EP1317953A1 (en) * 2001-11-30 2003-06-11 OMG AG & Co. KG Catalyst for lowering the amount of nitrogen oxides in the exhaust gas from lean burn engines
EP1364699A1 (en) * 2002-05-15 2003-11-26 Toyota Jidosha Kabushiki Kaisha NOx storage catalyst

Family Cites Families (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5412945A (en) * 1991-12-27 1995-05-09 Kabushiki Kaisha Toyota Cho Kenkusho Exhaust purification device of an internal combustion engine
JPH09262471A (en) * 1996-03-29 1997-10-07 Tokyo Roki Kk Catalytic material for cleaning of exhaust gas, catalyst for cleaning of exhaust gas and its production
DE19640161A1 (en) * 1996-09-28 1998-04-02 Volkswagen Ag NOx emission control process
DE19847008A1 (en) * 1998-10-13 2000-04-20 Degussa Nitrogen oxide storage catalytic converter
DE10132890A1 (en) * 2001-07-06 2003-01-16 Daimler Chrysler Ag Solid used for adsorption and desorption of nitrogen oxides found in internal combustion engine exhaust gases comprises a porous support; a metal component selected from alkali metals, alkaline earth
GB0305415D0 (en) * 2003-03-08 2003-04-16 Johnson Matthey Plc Exhaust system for lean burn IC engine including particulate filter and NOx absorbent

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE19838282A1 (en) * 1998-08-24 2000-03-02 Degussa Nitrogen oxide storage material and the nitrogen oxide storage catalyst produced therefrom
EP1317953A1 (en) * 2001-11-30 2003-06-11 OMG AG & Co. KG Catalyst for lowering the amount of nitrogen oxides in the exhaust gas from lean burn engines
EP1364699A1 (en) * 2002-05-15 2003-11-26 Toyota Jidosha Kabushiki Kaisha NOx storage catalyst

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2007009679A2 (en) * 2005-07-22 2007-01-25 Umicore Ag & Co. Kg Method for the reactivation of thermally aged nitrogen oxide storage catalytic converters
WO2007009679A3 (en) * 2005-07-22 2007-03-08 Umicore Ag & Co Kg Method for the reactivation of thermally aged nitrogen oxide storage catalytic converters
US7638452B2 (en) 2005-07-22 2009-12-29 Umicore Ag & Co. Kg Method for the reactivation of thermally aged nitrogen oxide storage catalytic converters

Also Published As

Publication number Publication date
GB0427890D0 (en) 2005-01-19
DE10361793A1 (en) 2005-07-28
GB2409656B (en) 2007-05-23

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PCNP Patent ceased through non-payment of renewal fee

Effective date: 20141221