Investigation of the Benzene Molecule Adsorbed on Faujasite Zeolite Using Double Quantum Filtered NMR Spectral Analysis
Resource
Journal of Physical Chemistry B 103 (24): 5070-5080
Journal
The Journal of Physical Chemistry B
Pages
5070-5080
Date Issued
1999
Date
1999
Author(s)
Chen, Yu-Huei
Hwang, Lian-Pin
Abstract
Deuteron NMR relaxation studies including double quantum filtered (DQF) spectral analyses, T1, and line widths are used to probe the dynamics and exchange process of various-loading benzene molecules adsorbed into NaY and dealuminated Y (DAY) including ultrastable Y (USY) zeolite. DQF NMR is a very sensitive method to determine the residual quadrupolar interaction resulting from the local order. In this work, we modified the cone model to describe the in-plane rotation around the hexad axis and the restricted wobbling motion of the benzene ring on the surface of the interaction site. The in-plane rotation and wobbling motion of adsorbed benzene molecules reflects a host−guest effect on the isolated adsorption site and also the mobility in the cage. In addition, the effect of a site-to-site hopping process results in a small net residual quadrupolar interaction. With increased loading, the in-plane rotation of benzene is significantly hindered in all faujasites but the population of adsorbed benzene dramatically reduces in DAY (including USY) systems only. This indicates the nature of site interaction on benzene molecules in a supercage. The population profile of adsorbate thus determined provides useful knowledge of loading effect, and the site interactions and distribution.
Type
journal article
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