The United States of America As Represented by the Administrator of the U.S. Environmental Protection Agency

Byron J Bunker

Charles R Schenk

Joseph McDonald

Daniel C Stokes

Robert E Moss

Brian A Olson

Paul Anthony Way

Christopher A Laroo

The method of treating a fuel lean exhaust containing NO and SO includes splitting the exhaust into major and minor portions for flow through multiple flow paths each of which contains a particulate trap and an absorber containing a NO oxidation catalyst and a nitrate absorbent. The major portion is passed through a flow path in the lean state at a first temperature to convert the NO to nitrate and the SO to sulfate. After the first period of operation flows are switched so that one flow path receives a minor exhaust portion for a second period of time during which fuel is injected into that flow path along with diversion of a portion of exhaust from another flow path through a bypass. When during the second period of operation the particulate trap reaches a predetermined temperature, the flow path is opened to an increased exhaust flow to transfer heat from the particulate trap to the NO absorber to bring the NO absorber to a temperature suitable for sulfation, at which time fuel and a small portion of exhaust gas are again introduced in order to effect the desulfation.

Method for NOx adsorber desulfation in a multi-path exhaust system

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Ann Arbor, MI, United States of America

Byron J Bunker