NONUNIFORM ACTIVITY DISTRIBUTION IN CATALYST PARTICLES - BENZENE HYDROGENATION ON SUPPORTED NICKEL IN A SINGLE PELLET DIFFUSION REACTOR

A single pellet diffusion reactor (SPDR) of new design has been used t o investigate the influence of nonuniform distributions of active ingr edient on the Ni-catalyzed hydrogenation of benzene. Five different di stributions, ranging from preferential shell-loading to uniform to pre ferential core loading have been studied under isothermal conditions. Analysis of results has been carried out using a simple one-dimensiona l diffusion/reaction analysis, which the configuration of the SPDR is set to mimic. The rate of the reaction follows an Eley-Rideal model, e ffectively positive fractional-order under the experimental conditions , for which kinetics the nonuniform distribution problem has not been studied experimentally before. Preferential shell-loading yields the h ighest catalytic effectiveness but because of the complex interactions between the reaction kinetics and the activity profiles within the pe llets, there is no simple relationship between diffusion lengths and e ffectiveness even for large values of the Thiele modulus.