Decrease in Activity of Diesel Hydrocarbon-Selective Catalytic Reduction on the Highway Fuel Economy Test

Transient exhaust emissions data were collected with a 4.9-L, V6 prototype diesel engine operated on an engine dynamometer using repetitive Highway Fuel Economy Tests (Hwy-FET). This procedure provided sufficient exhaust temperatures during transient operation to characterize the performance of an exhaust treatment system consisting of a diesel oxidation catalyst (DOC) followed by a hydrocarbon selective catalytic reduction (HC-SCR) system for NOx control under conditions typical of “real world”. The goal was to provide data needed for modeling the problem of hydrocarbon deactivation. Repetitive Hwy-FETs highlighted the effects of hydrocarbon deactivation over time. Stochastic Process Modeling showed that the observed catalyst deactivation was due mainly to a change in the reactivity of the catalyst and not to a change in the catalyst inlet conditions.