Modeling of Phosphorus Poisoning Phenomena over Diesel Oxidation Catalysts 2010-01-0884
To predict how DOC performance deteriorates with a lifetime of use, it is important to understand the mechanisms of catalyst aging. In off-road applications, due to the continuous high load usage and relatively high oil consumption rate, poisoning of the Diesel Oxidation Catalyst (DOC) with Phosphorus may become an important durability issue. In this study, 3D modeling has been performed to study the P poisoning mechanism and 1D modeling has been performed to investigate P poisoning parameters that effect DOC performance deterioration.
From postmortem analysis on engine aged DOCs there is a general trend that P deposits tend to collect at the outermost catalyst surface. Two types of 3D modeling were performed in this study to understand how P migrates into the bulk of the catalyst. In one case, P migrates into catalyst layer by gas phase diffusion and in the other case P first adsorbs on the catalyst surface and then migrates by solid diffusion into the bulk. The calculated result for the latter model showed a P poisoning trend that compared well to the engine aged, P poisoned DOC.
1D modeling of catalyst performance was based on information obtained from the 3D modeling. The catalyst performance was expressed by an Arrhenius type equation, loss of active sites by a decrease of the pre-exponential factor and deterioration of gas diffusion to the catalyst layer by the activation energy factor. Results will be compared to the catalyst durability requirements after 8000 h of catalyst usage.