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

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.