A diesel engine exhaust aftertreatment system and method of use. The system and method combine the attributes of lean or stoichiometric operation, using multiple LNTs (lean NOx traps) with one being capable of acting both as a lean NOx trap and a three-way catalyst. The engine is operated with lean air-to-fuel ratios during times that LNT treatment can efficiently reduce NOx from the exhaust gas. During times that lean NOx treatment is ineffective, the diesel engine is operated at or near a stoichiometric air-fuel ratio, so that three-way catalyst treatment can be used.
Charles E. Roberts Jr.; Christopher J. Chadwell