Experimental proof for resonant diffusion of normal alkanes in LTL and ZSM-12 zeolites

TL;DR

This study provides experimental evidence for resonant diffusion of normal alkanes in LTL and ZSM-12 zeolites, revealing periodic dependence of diffusion coefficients on alkane chain length and insights into alkane-zeolite interactions.

Contribution

It experimentally confirms resonant diffusion in zeolites and derives key parameters of alkane-zeolite interactions based on the theory.

Findings

Diffusion coefficient shows periodic dependence on alkane chain length.

Arrhenius law applies with periodic variations in parameters.

A compensation effect between activation energy and pre-exponential factor was observed.

Abstract

The intra-crystalline diffusion of normal alkanes in LTL and ZSM-12 zeolite was experimentally studied via gravimetric measurements performed at different temperatures. A periodic dependence of the diffusion coefficient on the number of carbon atoms in alkane was detected, which is an experimental proof for resonant diffusion. The present observations were described on the base of the existing theory of the resonant diffusion and several important parameters of the alkane-zeolite interaction and zeolite vibrations were obtained. In the considered temperature region the diffusion coefficient follows the Arrhenius law with periodic dependences of the pre-exponential factor and activation energy on the number of carbon atoms in alkanes. A compensation effect of simultaneous increases of the pre-exponential factor and the activation energy was also established.