Self-diffusion of simple alcohols in heteroionic forms of LTA zeolites

Radiotracers have been used to follow molecular diffusion of ethyl and n-bu tyl alcohols in LTA zeolite crystallites under the conditions of liquid pha se sorption. Evidence of a two-stage process has been observed. In the case of ethyl alcohol movement this prevented the estimation of energy barriers to molecular migration. Estimates were possible when n-butyl alcohol was t he labelled species. The effect of the presence of Mg, Ca, Sr, Zn, Na, Li, K, and H cations was studied. It was concluded that the mobility of unbound alcohol molecules contributed to the initial diffusion process and that th e second process was associated with alcohol molecules in some form of solv ation shield round the cations present in the larger zeolite cages. Compari sons to literature data for molecules moving in the gaseous phase through z eolites were made, and this enabled suggestions of the mechanism for moveme nts of molecules through zeolites in the liquid phase. (C) 2001 Elsevier Sc ience B.V. All rights reserved.