Diffusion waves and selectivity modifications in cyclic operation of a porous catalyst

Abstract The selectivity for a complex heterogeneously catalyzed reaction is examined for steady and periodic control of reactant concentration at the exterior catalyst surface. Cycling alters the selectivity by creating waves of concentrations within the catalyst which interact favorably in this instance. This new phenomenon in periodic processing is revealed by an analytical perturbation solution for the reaction-limited regime, a technique which can be extended to other reaction mechanisms. Numerical simulations employing an orthogonal collocation technique reproduce the perturbation solution in the reaction-limited regime and show that favorable effects of cycling persist when mass transfer limits the overall reaction.