Degradation of catalyst performance with time is described as ageing. There are two significant ageing mechanisms: poisoning and sintering. Experimental data on ageing have been obtained on an engine test bed using a specially designed catalyst core holder; the catalyst samples were subjected to different accelerated ageing regimes and durations. The ageing regimes were as follows: low temperature dosed (mainly poisoning); high temperature not dosed (mainly sintering); high temperature dosed (both sintering and poisoning). The experiments provided a series of samples from which the spatial and time dependences of the poisoning have been found. Portions of the samples were subjected to X-ray fluorescence analysis after ageing. A combined model of poisoning and sintering was developed and incorporated into a computational fluid dynamics model. This combined model can predict the level of deactivation as a function of length along the catalyst and as a function of time. Agreement between measured poison accumulation and predictions was achieved by tuning the sintering parameter.

No abstract