Comparison of predicted and nuclear magnetic resonance zeolitic diffusion coefficients

Abstract

Application of the n.m.r. pulsed field gradient technique allows direct determination of molecular mean square displacements. The values of the mean square displacements obtained by a numerical solution of the proper diffusion problem agree well with the usual representation of effective self-diffusion coefficients in temperature regions of intracrystalline, restricted and intercrystalline diffusion. It is demonstrated that there are at least four different conditions correlating the n.m.r. diffusivity data with characteristic parameters of the zeolitic adsorbate–adsorbent system. Literature data on self-diffusion are in satisfactory agreement with these criteria.