Optimal catalyst activity distribution and generalized effectiveness factors in pellets: Single reactions with arbitrary kinetics

The problem of optimal catalyst activity distribution in pellets is analysed for single reactions with arbitrary kinetics. It is shown that the effectiveness factor for given catalyst mass is maximized (or the catalyst mass required to obtain a given global reaction rate is minimized) by concentrating all the active catalyst in a specific location in the pellet. The optimum location of the catalyst is expressed in terms of a single dimensionless group. General analytical effectiveness factor expressions are also obtained for arbitrary fixed location of the active component in the pellet in terms of a generalized shape-normalizing Thiele modulus ΦB. These expressions show that η = 1ΦB2 for large values of ΦB.