Catalyst to improve low temperature deNOx activity in a reformer-LNT exhaust aftertreatment system

摘要

A low temperature lean NO_x catalyst is configured in a diesel exhaust treatment system upstream of a fuel reformer-LNT system to provide low temperature performance. During system warm-up and anytime the LNT falls below an effective operating temperature, the exhaust aftertreatment system is provided with hydrocarbons at a rate proportional to the exhaust NO_x flow rate, whereby NO_x is reduced over the lean NO_x catalyst. Optionally, the lean NO_x catalyst is also adapted for use warming up the fuel reformer and or catalyzing NO to NO₂ conversion. These concepts allow the reformer and LNT to be designed for high temperature performance and durability without also having to be adapted for NO_x mitigation at the exhaust system's lowest temperatures.