Diffusion in zeolites: A critical assessment on an observed 'Fickianity'

摘要

The diffusion of various chemicals in zeolites has been widely studied by different techniques. A large number of diffusivity data in zeolite microcrystals have been reported. In this communication, the estimations justifying the standard diffusion in zeolites are critically revisited. Using the logarithmic resealing it is demonstrated that the estimation procedure based on fitting the experimental data by a simple solution of the second Fick's law of diffusion is incomplete to draw a conclusion on the occurrence of the Fickian diffusion. As a consequence, the data on the standard Fickian diffusion in zeolite microcrystals is only an assumption, which is not proved and, thus, cannot be trusted. Several examples of the incompleteness of the estimation procedure are presented based on a reevaluation of the data previously published in the literature.