Catalyst deactivation: Control relevance of model assumptions

Two principles for describing catalyst deactivation are discussed, one base d on the deactivation mechanism, the other based on the activity and cataly st age distribution. When the model is based upon activity decay, it is com mon to use a mean activity developed from the steady-state residence time d istribution. We compare control-relevant properties of such an approach wit h those of a model based upon the deactivation mechanism. Using a continuou s stirred tank reactor as an example, we show that the mechanistic approach and the population balance approach lead to identical models. However, com mon additional assumptions used for activity-based models lead to model pro perties that may deviate considerably from the correct one.