Modeling and experimental insights on oxidation of heavy chain HCs on diesel oxidation catalysts

Abstract

A global kinetic model was developed for co-oxidation of n-dodecane and NOx on state-of-the-art DOC. The model captures the impact of HC (0.1–1.8% C1) and NOx feed concentrations on the oxidation of n-dodecane. The oxidation activity of n-alkanes has a weak dependence on chain length when n > 10 [18], implying the general applicability of the model to catalytic oxidation of heavy chain n-alkanes. Reactor-based co-oxidation data of dodecane and NO has been presented to emphasize the coupling of homogeneous and heterogeneous reactions inside DOC. We highlight how this coupling influences the oxidation performance of DOC. Diesel oxidation was more self-inhibiting than dodecane oxidation due to unsaturated HCs, primarily aromatics. HC speciation data of diesel fuel or diesel engine exhaust showed clear evidence for the co-existence of alkanes and aromatics, both 1-ring and multi-ring aromatics. Diesel oxidation data showing self-inhibition can be described using model-based proxies for alkylbenzenes and heavy n-alkanes, each for each category.