Patent ID: 8776499

Claim:
A system for treatment of an engine exhaust stream including nitrogen oxides and other exhaust gas components, the system comprising: an exhaust conduit in fluid communication with the engine via an exhaust manifold; an injector in fluid communication with the manifold and the conduit, the injector being coupled to an ammonia or ammonia precursor source and to periodically meter the ammonia or ammonia precursor into the system such that the ammonia or ammonia precursor contacts the manifold and the conduit; and a selective catalytic reduction (SCR) catalyst composition on a metal substrate having an oxidized surface that resists corrosion in fluid communication with and downstream of the injector, the catalyst composition effective to promote a SCR reaction between the ammonia and the nitrogen oxides, wherein the substrate is passivated with a component that inhibits oxidation reactions to minimize reaction of the substrate with the ammonia so that the ammonia is not oxidized, wherein the component that inhibits oxidation comprises an oxide selected from the group consisting of an aluminum oxide, iron oxide, titanium oxide, zirconia oxide, silicon oxide, zinc oxide, and combinations thereof, and wherein the component that inhibits oxidation reactions is in a first layer located on the metal substrate and the SCR catalyst composition is in a second layer including a zeolite and a base metal component on the first layer.