The isotope exchange technique was used to measure equilibria and kinetics for the adsorption of pure N2, CH4 and Kr on a 4A zeolite sample. The intracrystalline self-diffusivities for these gases were measured under isothermal conditions (table 1). The self-diffusivities of Kr and CH4 were smaller than that of N2 by 2 and 1 orders of magnitude, respectively. The self-diffusivity of N2 was independent of its surface coverage, but the self-diffusivities of CH4 and Kr increased with increasing coverages in the high-pressure region. This effect was much more pronounced for Kr. The activation energies for self-diffusion of the gases decreased in the order Kr > CH4 > N2 while the isosteric heats of adsorption of the gases in the Henry's law region were very close. The activation energies were larger than the corresponding isosteric heats of adsorption for each gas.

Self-Diffusivities of N2, CH4, and Kr on 4A Zeolite Pellets by Isotope Exchange Technique. D.V.Cao, R.J.Mohr, M.B.Rao, S.Sircar: Journal of Physical Chemistry B, 2000, 104[45], 10498–501