Modelling of Phosphorus Poisoning Using Computational Fluid Dynamics and its Effect on Automotive Catalyst Performance

Accumulation of phosphorus in an automotive catalyst is detrimental to catalyst performance, leading to partial or total deactivation. The deactivation model described in this paper utilises CFD to derive a one-dimensional mathematical solution to obtain phosphorus accumulation profiles down the length of a catalyst. The early work of Oh and Cavendish [1] is the basis for this study. A model output, θ, represents the fraction of catalytic surface area that is deactivated. This poisoned fraction is shown to build up locally depending on exposure time to phosphoric acid (H₃PO₄) in the exhaust flow.

Having obtained the poisoned fraction from the model as a function of poison exposure time, θ is used to predict light off times and conversion efficiencies during the deactivation process through incorporation of a kinetic reaction scheme. The model provides a good representation of the phenomena noted in real catalysts; i.e. delayed light off times. The model can be readily adapted to 3D catalyst systems.