Optimal Catalyst Activity Profiles In Pellets .10. the Role of Catalyst Loading

The design of nonuniformly active pellets which maximize catalyst performance is examined by considering the active element concentration as the optimization variable so as to explicitly account for its effect on the rate of reaction. If the reaction rate vs active element concentration relationship is linear, the optimal distribution is found, under very general conditions, to belong to the family of step-distributions. Furthermore, when the upper bound for the active element concentration due to saturation is neglected, such distributions take the form of a Dirac delta function, thus recovering the results of previous studies. If the above relationship is nonlinear, then the optimization problem is amenable to analytic solution only in some specific situations, while in the general case a suitable numerical procedure has to be utilized. Examples of both cases are given, with reference to specific reacting systems of practical interest.