Multistage reductant injection strategy for slipless, high efficiency selective catalytic reduction

摘要

One aspect of the invention relates to an exhaust treatment apparatus having an NO_x reduction system comprising first and second catalyst beds in series with associated first and second ammonia injectors. The first catalyst bed with its associated ammonia injector preferably targets removing only about 80 to about 95% percent of the NO_x in the vehicle exhaust. The second catalyst bed with its associated injector preferably target removing about 70 to about 100% of the remaining NO_x. Staging the reduction system in this manner improves control over NO_x reduction and reduces the risk of ammonia slip. Other aspects of the invention relate to methods of treating vehicle exhaust to remove NO_x and an SCR reactor comprising a housing having an entrance port, an exit port, and an ammonia injection port, wherein the injection port is configured to inject ammonia in between SCR catalyst beds contained in the housing.