Patent ID: 8302387

Claim:
A diesel exhaust after-treatment system for a vehicle comprising: a precious metal primary diesel oxidation catalyst located on an exhaust pipe and in fluid communication with and between an engine and an exhaust gas outlet; a precious metal secondary diesel oxidation catalyst selectively in fluid communication with the primary diesel oxidation catalyst; a fuel injector for injecting fuel into the exhaust gas and being oxidized at one of the primary diesel oxidation catalyst; and the secondary diesel oxidation catalyst for heating the exhaust gas that flows to the other of the primary diesel oxidation catalyst and the secondary diesel oxidation catalyst; and an electronic control unit including programming configured to execute at least three modes of operation, the at least three modes of operation comprising: a normal operating mode wherein the exhaust gas flows from the engine to the primary diesel oxidation catalyst to the outlet, and wherein the secondary diesel oxidation catalyst does not receive continuous, positive exhaust gas flow through the secondary diesel oxidation catalyst; a second operating mode wherein the primary diesel oxidation catalyst is saturated with sulfur, and the exhaust gas flows from the engine to the secondary diesel oxidation catalyst to the primary diesel oxidation catalyst to the outlet; and a third operating mode wherein the secondary diesel oxidation catalyst is saturated with sulfur, and the exhaust gas flows from the engine to the primary diesel oxidation catalyst to the secondary diesel oxidation catalyst to the outlet.