Patent ID: 8151558

Claim:
An exhaust system, comprising: an exhaust passageway; a reduction catalyst located within the exhaust passageway; a particulate filter located within the exhaust passageway upstream of the reduction catalyst, at least part of the particulate filter being catalyzed to reduce NO X ; a first oxidation catalyst located within the exhaust passageway upstream of the reduction catalyst to provide a desired ratio of NO:NO 2 to the reduction catalyst; an exhaust gas recirculation loop situated to receive exhaust from the exhaust passageway at a location upstream of the first oxidation catalyst and downstream of the particulate filter; a first injector located to inject reductant into the exhaust passageway upstream of the reduction catalyst, wherein the exhaust gas recirculation loop is situated to receive exhaust from the exhaust passageway at a location upstream of both the first oxidation catalyst and the first injector; a second injector located to inject reductant into the exhaust passageway upstream of the particulate filter; and a second oxidation catalyst located downstream of the particulate filter and upstream of the location from which the exhaust gas recirculation loop receives exhaust to remove residual reductant from the exhaust.