| abstract |
Ag/Al 2 O 3 materials may be packaged in a suitable flow-through reactor, in combination with another material selected as a passive NOx adsorber material (PNA), both the silver material and the adsorber material being close coupled to the exhaust manifold of a diesel engine, and upstream of other catalytic devices, such as a diesel oxidation catalyst and a selective reduction catalyst for NOx. The silver catalyst material uses hydrogen in a cold-start engine exhaust and serves to oxidize NO to NO 2 in the relatively low temperature, hydrocarbon-containing, exhaust during a short period following the engine cold start, and to temporarily store NOx during the start-up period. After the flowing exhaust gas stream has heated the PNA and the downstream catalytic devices, the silver yields its nitrogen oxides for conversion to nitrogen by the then-operating devices before NOx is discharged to the atmosphere. |