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Updated: Jun 23, 2026

In Situ Monitoring of Diffusion of Guest Molecules in Porous Media Using Electron Paramagnetic Resonance Imaging
Published on: September 2, 2016
Self-diffusion studies of binary mixtures in NaX zeolites using pulsed field gradient NMR and a Maxwell-Stefan model
1Department of Chemical and Biological Engineering and Institute for Catalysis in Energy Processes, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, USA.
Abstract:
Intracrystalline self-diffusion coefficients were measured by pulsed field gradient (PFG) NMR for single components and binary mixtures of CF(4) and various hydrocarbons in large-crystal NaX zeolites. A short-time diffusion model was used to obtain the unrestricted intracrystalline self-diffusivities by extrapolating to zero diffusion time, when no molecules can leave the crystal during the measurement. The results were used to test a theoretical model from Skoulidas, Sholl, and Krishna for predicting diffusion coefficients of mixtures in zeolites from single-component data. The predicted binary self-diffusivities are consistent with those directly measured in PFG NMR mixture experiments, thus providing an experimental validation of the model.
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