Catalyst deactivation: Control relevance of model assumptions

Two principles for describing catalyst deactivation are discussed, one base d on the deactivation mechanism and the other based on the activity and cat alyst age distribution. When the model is based upon activity decay, it is common to use a mean activity developed from the steady-state residence tim e distribution. We compare control-relevant properties of such an approach with those of a model based upon the deactivation mechanism. Using a contin uous stirred tank reactor as an example, we show that the mechanistic appro ach and the population balance approach lead to identical models. However, common additional assumptions used for activity-based models lead to model properties that may deviate considerably from the correct one.