Ammonia slip catalyst and a system containing it for exhaust emission control on diesel engines

摘要

An ammonia slip control catalyst having a layer containing perovskite and a separate layer containing an SCR catalyst is described. The ammonia slip catalyst can have two stacked layers, with the top overlayer containing an SCR catalyst, and the bottom layer containing a perovskite. The ammonia slip catalyst can alternatively be arranged in sequential layers, with the SCR catalyst being upstream in the flow of exhaust gas relative to the perovskite. A system comprising the ammonia slip catalyst upstream of a PGM-containing ammonia oxidation catalyst and methods of using the system are described. The system allows for high ammonia oxidation with good nitrogen selectivity. Methods of making and using the ammonia slip catalyst to reduce ammonia slip and selectively convert ammonia to N2 are described.