| 摘要 |
PROBLEM TO BE SOLVED: To provide catalysts, methods for preparing catalysts, and methods for treating exhaust gas streams.SOLUTION: A method for treating exhaust gas streams comprises injecting ammonia or an ammonia precursor into an exhaust gas stream of a vehicle, in which a catalyst system includes: an upstream zone effective to catalyze the conversion of a mixture of NOand NHinto N; and a downstream zone effective to convert ammonia into Nin the presence of NOor in the absence of NO. A method for preparing a catalyst system includes: coating one end of a substrate along at least 5% of its length with an undercoat wash coat layer 200 containing a material composition effective to catalyze the removal of ammonia, first; and coating the coated substrate with an overcoat layer 300 containing a material composition effective to catalyze the conversion of a mixture of NOand NHinto N, second.SELECTED DRAWING: Figure 1B |
