On the Diffusion of Cyclohexane in ZSM-5 Measured by Zero-Length-Column Chromatography

The sorption kinetics of cyclohexane in three samples of ZSM-5, differing in size and morphology, were measured using the zero-length-column (ZLC) method. The diffusivities were found to be consistent across the samples and agree well with data previously published in the literature, except that the small zeolite crystals exhibited values similar to those of the large particles, contrary to some results. Inconsistencies with the standard model assumptions were partly explained by the effect of the Langmuir-type adsorption equilibrium known to be a property of the system. These deviations do not seem to diminish the validity of the measured diffusion coefficients. ZLC appears to be a very robust technique for diffusion measurements when analyzed using the “long-time” solution method.