An apparatus for reactivating a sulfur poisoned oxidation catalyst operating in the exhaust of a lean burn, methane source (as in natural gas) fueled combustion device as in an engine. The reactivation includes desulfation of the poisoned catalyst through the use of a CO supplementation apparatus in communication with the control unit that is adapted to supplement the CO content in the exhaust reaching the catalyst, while avoiding an overall rich exhaust atmosphere at the catalyst. An example includes the added supply of hydrocarbons to one or more, preferably less than all, of the lean burn engine's combustion chambers such as by an ECU controlled extra supply of NG (e.g., CNG) to some of the combustion chambers. Also featured is a method for desulfation of an oxidation catalyst of a lean burn CNG engine by supplying excess CO to the exhaust reaching the catalyst while retaining an overall lean state, and a method of assembling an apparatus for reactivating a sulfur deactivated lean burn NO engine catalyst by assembling a CO supplementation apparatus with a control unit.

An internal combustion engine system is described herein. The system uses an additive added to the exhaust of the internal combustion engine to maintain a range of NO2 to NO within a range that provides for a fast SCR reaction in a selective catalyst reduction unit. The additive and the exhaust enter a diesel oxidation catalyst (DOC), whereby the NO2 undergoes a two-stage process. In the first stage, the NO2 from the exhaust is adsorbed onto the precious metal catalyst of the DOC and an atomic oxygen is removed from the NO2, reducing the NO2 to NO. Because of the higher reactivity of the additive, the additive scavenges a portion of the atomic oxygen from the catalyst. During the second stage of the DOC process, the NO is oxidized over the catalyst to form NO2.

An internal combustion engine system is described herein. The system uses an additive added to the exhaust of the internal combustion engine to maintain a range of NO2 to NO within a range that provides for a fast SCR reaction in a selective catalyst reduction unit. The additive and the exhaust enter a diesel oxidation catalyst (DOC), whereby the NO2 undergoes a two-stage process. In the first stage, the NO2 from the exhaust is adsorbed onto the precious metal catalyst of the DOC and an atomic oxygen is removed from the NO2, reducing the NO2 to NO. Because of the higher reactivity of the additive, the additive scavenges a portion of the atomic oxygen from the catalyst. During the second stage of the DOC process, the NO is oxidized over the catalyst to form NO2.

The present disclosure is directed at a ruthenium based catalyst for NOx reduction. More specifically, ruthenium based catalysts are used for NOx reduction in an internal combustion engine to reduce NO.sub.X to nitrogen, at relatively high conversion and selectivity, using carbon monoxide and hydrogen as reductants. The ruthenium based catalyst has particular utility in exhaust gas recirculation such as in dedicated exhaust gas recirculation (D-EGR) systems.

The present disclosure is directed at a ruthenium based catalyst for NOx reduction. More specifically, ruthenium based catalysts are used for NOx reduction in an internal combustion engine to reduce NO.sub.x to nitrogen, at relatively high conversion and selectivity, using carbon monoxide and hydrogen as reductants. The ruthenium based catalyst has particular utility in exhaust gas recirculation such as in dedicated exhaust gas recirculation (D-EGR) systems.