Analytical Study of Effectiveness of a Degreened and Aged DOC as an Oxidation Device for NO Under Variable Operating and Inlet Conditions 2009-01-0908

It has recently been suggested in an experimental study that an aged DOC could be net consumer of engine out NO₂ (Katare et al, 2007) thus inhibiting the fast reaction (2NH₃ + NO + NO₂ => 2N₂+3H₂O) in an SCR that might follow. Both engine test and flow reactor results indicated that at low temperatures CO and HC reduces NO₂ to NO and that CO is much better reductant than HC. The present study investigates the mechanistic story behind this experimentally observed phenomenon by means of a global reaction mechanism. It also investigates the role of CO inhibition of NO oxidation at higher temperature which also plays key role in the overall oxidation efficiency of a DOC. Once a suitable mechanism is defined by comparing against measurements, the current study will use it to examine conditions under which DOC can destroy NO₂ and to propose possible strategies to avoid NO₂ consumption in order to obtain high SCR efficiency. Additionally drive cycle data will be used to indicate cumulative NO₂ reduction effects of the aged DOC.