Exhaust-gas aftertreatment device with nitrogen oxide storage catalytic converter, and operating method therefor

• US 20030056499A1
• Filed: 06/26/2002
• Published: 03/27/2003
• Est. Priority Date: 07/03/2001
• Status: Active Grant

• Current Assignee: Daimler AG (Mercedes-Benz Group AG)
• Original Assignee: DaimlerChrysler AG (Mercedes-Benz Group AG)
• Inventors: Renfftlen, Stefan, Krutzsch, Bernd, Wunsch, Rolf, Hertzberg, Andreas, Weibel, Michel, Binder, Klaus, Voigtlander, Dirk, Olschlegel, Heinz-Jost, Gunther, Josef, Wenninger, Gunter, Konrad, Brigitte, Weirich, Marko
• Granted Patent: US 6,766,642 B2
• Time in Patent Office: Days
• US Class Current: 60/295
• CPC Class Codes: B01D 2255/20707 Titanium
• CPC Class Codes: B01D 2255/20723 Vanadium
• CPC Class Codes: B01D 2255/20776 Tungsten
• CPC Class Codes: B01D 2257/304 Hydrogen sulfide
• CPC Class Codes: B01D 53/9418 for removing nitrogen oxides by selective catalytic reduction [SCR] using a reducing agent in a lean exhaust gas
• CPC Class Codes: B01D 53/944 Simultaneously removing carbon monoxide, hydrocarbons or carbon making use of oxidation catalysts three-way-catalysts [TWC] B01D53/9445
• CPC Class Codes: B01D 53/9477 with catalysts positioned on separate bricks, e.g. exhaust systems
• CPC Class Codes: B01D 53/9481 Catalyst preceded by an adsorption device without catalytic function for temporary storage of contaminants, e.g. during cold start
• CPC Class Codes: F01N 13/009 having two or more separate purifying devices arranged in series
• CPC Class Codes: F01N 13/0097 the purifying devices are arranged in a single housing
• CPC Class Codes: F01N 2570/04 Sulfur or sulfur oxides
• CPC Class Codes: F01N 2610/02 the substance being ammonia or urea
• CPC Class Codes: F01N 3/0814 combined with catalytic converters, e.g. NOx absorption/storage reduction catalysts
• CPC Class Codes: F01N 3/0821 combined with particulate filters catalysed diesel particulate filters F01N3/035
• CPC Class Codes: F01N 3/0842 Nitrogen oxides
• CPC Class Codes: F01N 3/0885 Regeneration of deteriorated absorbents or adsorbents, e.g. desulfurization of NOx traps
• CPC Class Codes: F01N 3/2066 Selective catalytic reduction [SCR]
• CPC Class Codes: F02B 37/00 Engines characterised by provision of pumps driven at least for part of the time by exhaust
• CPC Class Codes: F02D 41/028 Desulfurisation of NOx traps or adsorbent
• CPC Class Codes: F02D 41/1475 Regulating the air fuel ratio at a value other than stoichiometry
• CPC Class Codes: F02M 26/00 : Engine-pertinent apparatus for adding exhaust gases to combustion-air, main fuel or fuel-air mixture, e.g. by exhaust gas recirculation [EGR] systems
• CPC Class Codes: F02M 26/05 : High pressure loops, i.e. wherein recirculated exhaust gas is taken out from the exhaust system upstream of the turbine and reintroduced into the intake system downstream of the compressor
• CPC Class Codes: Y02A 50/20 : Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters
• CPC Class Codes: Y02T 10/12 : Improving ICE efficiencies

Abstract

An exhaust-gas aftertreatment device with a nitrogen oxide storage catalytic converter for an internal combustion engine, and a method for operating an exhaust-gas aftertreatment device which is assigned to an internal combustion engine and has a nitrogen oxide storage catalytic converter. An SCR catalytic converter is arranged in the exhaust-gas aftertreatment device, it being possible for the exhaust gas which emerges from the nitrogen oxide storage catalytic converter to be fed to the SCR catalytic converter when the internal combustion engine is in a desulphating operating mode with a reducing exhaust-gas composition, in order for H₂S which is formed during the desulphating to be removed. When the internal combustion engine is in a desulphating operating mode, the following steps are performed: establishing a reducing exhaust gas composition upstream of the nitrogen oxide storage catalytic converter; releasing the sulphur which is bound in the nitrogen oxide storage catalytic converter, to form hydrogen sulphide (H₂S); feeding the hydrogen sulphide to an SCR catalytic converter which is arranged downstream of the nitrogen oxide storage catalytic converter in the exhaust-gas aftertreatment device; and reacting the hydrogen sulphide in the SCR catalytic converter to form sulphur dioxide under reducing exhaust-gas conditions. The method may be used in motor vehicles, e.g., passenger cars, with lean-burn internal combustion engines.

Claims

1. An exhaust-gas aftertreatment device for an internal combustion engine, comprising:

a nitrogen oxide storage catalytic converter; and

an SCR catalytic converter arranged so that exhaust gas that emerges from the nitrogen oxide storage catalytic converter is fed to the SCR catalytic converter when the internal combustion engine is in a desulphating operating mode with a reducing exhaust-gas composition, in order to remove H₂S which is formed during the desulphating.

2. The exhaust-gas aftertreatment device according to claim 1, wherein the SCR catalytic converter includes at least one of vanadium pentoxide, tungsten oxide, and titanium dioxide.

3. The exhaust-gas aftertreatment device according to claim 1, further comprising a particle filter.

4. The exhaust-gas aftertreatment device according to claim 3, further comprising an oxidation catalytic converter connected upstream of the particle filter.

5. The exhaust-gas aftertreatment device according to claim 3, wherein the nitrogen oxide storage catalytic converter is arranged downstream of the particle filter.

6. The exhaust-gas aftertreatment device according to claim 4, wherein the nitrogen oxide storage catalytic converter is arranged upstream of an oxidation catalytic converter.

7. A method for operating an exhaust-gas aftertreatment device assigned to an internal combustion engine, the device including a nitrogen oxide storage catalytic converter, the internal combustion engine in a desulphating operating mode, comprising the steps of:

establishing a reducing exhaust-gas composition upstream of the nitrogen oxide storage catalytic converter;

releasing sulphur bound in the nitrogen oxide storage catalytic converter to form hydrogen sulphide;

feeding the hydrogen sulphide to an SCR catalytic converter arranged downstream of the nitrogen oxide storage catalytic converter; and

reacting the hydrogen sulphide in the SCR catalytic converter to form sulphur dioxide under reducing exhaust-gas conditions.

8. The method according to claim 7, further comprising the step of passing the exhaust gas through a particle filter.

9. The method according to claim 8, wherein the exhaust-gas aftertreatment device is assigned an oxidation catalytic converter, the method further comprising the step of feeding the exhaust gas that flows out of the oxidation catalytic converter to the particle filter.

10. The method according to claim 8, wherein the exhaust-gas aftertreatment device is assigned an oxidation catalytic converter upstream of the particle filter, the method further comprising the step of feeding the exhaust gas that flows out of the particle filter to the nitrogen oxide storage catalytic converter.

11. The method according to claim 8, wherein the exhaust-gas aftertreatment device is assigned an oxidation catalytic converter, the method further comprising the step of feeding the exhaust gas that flows out of the nitrogen oxide storage catalytic converter to the oxidation catalytic converter.