Daimler Chrysler Ag

Josef Guenther

Bernd Krutzsch

Guenter Wenninger

Michel Weibel

Arno Nolte

Dirk Voigtlaender

Marko Weirich

Brititte Konrad

A method and apparatus for purifying an exhaust gas of an internal combustion engine includes an ammonia generating catalyst for generating ammonia from nitrogen oxides contained in the exhaust gas to be purified, and a nitrogen oxide reducing catalyst downstream of the ammonia generating catalyst, for reduction of nitrogen oxides contained in the exhaust gas to be purified. Generated ammonia is used as the reducing agent. A nitrogen oxide adsorption catalyst is arranged upstream of the ammonia generating catalyst, or the ammonia generating catalyst is arranged in an exhaust pipe branch which pertains to only a part of several separately controllable internal-combustion sources. One or more additional exhaust pipe branches assigned to the other internal-combustion sources and lead to the nitrogen oxide reducing catalyst, while bypassing the ammonia generating catalyst. The part of the internal-combustion sources pertaining to the exhaust pipe branch of which contains the ammonia generating catalyst is operated either continuously or intermittently in a rich mode. Also, one or more combustion sources which feed their exhaust gas to the nitrogen oxide adsorption catalyst may be operated alternately in a lean and rich mode.

Exhaust gas purification process and apparatus with internal generation of ammonia for reducing nitrogen oxide

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Affalterbach, Germany

Josef Guenther