Diffusion of Light Hydrocarbons in 5A Zeolite

Abstract

Experimental diffusivity data are presented for the diffusion of ethane, ethylene, propane, propylene, cyclopropane, n-butane, 1-butene, cis-2-butene, and trans-2-butene in Linde 5A zeolite. It is shown that the concentration dependence of the diffusivity may be accounted for by considering the non-linearity of the equilibrium isotherms. Activation energies for diffusion, derived from the temperature dependence of the limiting diffusivity at zero sorbate concentration, show a clear correlation with the critical diameters of the sorbate molecules. The data are interpreted in terms of the transition state theory of diffusion and it is shown that, for the simpler molecules, this theory gives a quantitatively correct prediction of the pre-exponential factor governing the temperature dependence of the zeolitic diffusivity.