Diffusion in 4A zeolite. Study of the effect of crystal size

Abstract

Sorption rates for N₂, CH₄ and C₂H₆ have been measured in different size fractions of synthetic 4A zeolite crystals. Both the form of the uptake curves and the dependence of the time constant on crystal radius are entirely consistent with the assumption that the kinetics of sorption are controlled by intracrystalline diffusion, rather than by a surface barrier. Comparisons between different samples of crystals show large differences in diffusivity and the diffusivities are much smaller than the values derived from n.m.r. measurements.