Transport of aromatic molecules in NaY Zeolite powders
Article first published online: 17 JUN 2004
Copyright © 1990 American Institute of Chemical Engineers
Volume 36, Issue 10, pages 1562–1568, October 1990
How to Cite
Chmelka, B. F., Gillis, J. V., Petersen, E. E. and Radke, C. J. (1990), Transport of aromatic molecules in NaY Zeolite powders. AIChE J., 36: 1562–1568. doi: 10.1002/aic.690361012
- Issue published online: 17 JUN 2004
- Article first published online: 17 JUN 2004
- Manuscript Revised: 20 AUG 1990
- Manuscript Received: 2 MAY 1990
Xenon-129 NMR is used to probe macroscopic distributions of aromatic molecules adsorbed in a packed bed of 1-μm NaY zeolite particles. Relative rates of guest transport through the intracrystalline (micro) and intercrystalline (macro) pores play a unique role in the axial distribution of sorbate molecules, such as hexamethylbenzene, in a zeolite powder. Xenon-129 NMR spectra show that a sharp HMB adsorption front advances through a bed of dehydrated NaY crystallites at 523 K. However, at 573 K or in the presence of coadsorbed water, HMB species disperse through the bed without forming a sharp boundary between adsorption zones.
When guest transport is controlled by pseudosteady-state diffusion in the macropores, axial penetration of the bed by vapor-phase guest species occurs in a sharp adsorption front. A shrinking-core transport model then quantitatively estimates the intracrystalline diffusivities of HMB in dehydrated and partially hydrated NaY zeolite of 10−11 and 10−13 m2/s, respectively, at 523 K. Xenon-129 NMR proves to be a powerful tool for probing adsorbed guest distribution in zeolites, allowing relative time scales to be established for transport of molecular guests in NaY powders.