Integrated scr and amox catalyst systems

Abstract

Catalysts, methods of preparing catalyst, and methods for treating exhaust gas streams are described. In one or more embodiments, a catalyst system includes an upstream zone effective to catalyze the conversion of a mixture of NOand NHto N, and a downstream zone effective for the conversion of ammonia to Nin the presence or absence of NO. In an embodiment, a method for preparing a catalyst system includes: first coating one end of a substrate along at least 5% of its length with an undercoat washcoat layer containing a material composition effective to catalyze the removal of ammonia; second coating with an overcoat layer containing a material composition effective to catalyze the conversion of a mixture of NOand NHto N. A method for treating the exhaust gas stream is provided, which includes injecting ammonia or an ammonia precursor into an exhaust gas stream of a vehicle, passing the engine exhaust gas stream containing NOand NHthrough the upstream zone of a catalyst system to remove NOand then passing the exhaust gas stream through the downstream zone of the catalyst system to remove NH, as well as other oxidizable species such as hydrocarbons and CO.