Patent ID: 8316633

Claim:
A method for reducing the particulate matter and NOx content of the exhaust gas of a diesel engine, without use of a lean NOx trap, comprising: operating the diesel engine such that its normal operation is stoichiometric and does not include any active regeneration mode; wherein the engine-out exhaust normally contains more hydrocarbon and carbon monoxide emissions than NOx emissions; wherein the stoichiometric engine operation is achieved by using one or more of the following: intake air throttling and decreased intake air boosting; directing the exhaust gas from the engine to a diesel oxidation catalyst; wherein the diesel oxidation catalyst is formulated to provide an exothermic reaction from hydrocarbon and carbon monoxide in the exhaust gas and to use reduce the NOx content of the exhaust gas to a constant DOC-out level of less than 50 ppm; and directing the exhaust gas from the diesel oxidation catalyst to a catalyzed diesel particulate filter; wherein the diesel particulate filter is proximate the diesel oxidation catalyst such that the exothermic reaction raises the exhaust temperature at the input to the diesel particulate filter by an amount sufficient to passively regenerate the diesel particulate filter.