Three-dimensional diffusion in nanoporous host-guest materials monitored by interference microscopy

¹  Faculty of Physics and Geosciences, University of Leipzig - Linnéstr. 5, 04103 Leipzig, Germany
²  Corporate Strategic Research, ExxonMobil Research and Engineering Company - Annandale, NJ 08801, USA
³  School of Chemistry, University of St. Andrews - North Haugh, St. Andrews, Fife, KY16 9ST UK

Corresponding author: kaerger@physik.uni-leipzig.de

Received: 12 September 2007
Accepted: 8 November 2007

Abstract

For the first time, by the application of interference microscopy, direct monitoring of three-dimensional guest diffusion in nanoporous host-guest systems has become possible. The primary experimental evidence accessible using this technique is the integral over the concentration in the direction of observation. In the present letter, an algorithm is presented which provides direct access to the local concentrations. For the system under study, methanol in the silicoaluminophosphate zeotype SAPO STA-7, the intracrystalline concentration evolving during a sorption experiment is calculated by the suggested method and the resulting data is used to determine the concentration dependence of the principal values of the diffusion tensor as well as of the surface permeability.