The Technological Impact of Diffusion in Nanopores

The impact of nanopore diffusion on the performance of adsorption separation processes is reviewed. Zeolite membrane processes and kinetically selective cyclic adsorption processes depend for their selectivity on differences in intracrystalline diffusion rates so these processes are designed to operate under conditions of intracrystalline diffusion control. In contrast, the performance of equilibrium based adsorption separation processes is adversely affected by diffusional resistance so in such processes the minimization of all resistances to mass transfer is a major design objective. Zeolite catalyzed reactions constitute a further important class of processes in which intrusion of diffusional resistance can be either advantageous or disadvantageous. Such effects are illustrated by considering in detail the conversion of methanol to light olefins (MTO) over SAPO34.