Scott M. Auerbach, Neil J. Henson, Anthony K. Cheetham, and
Horia I. Metiu, ``Transport theory for cationic zeolites:
Diffusion of benzene in Na-Y,''
J. Phys. Chem. 99, 10600-10608 (1995).
Abstract
We have modelled benzene diffusion in Na-Y zeolite (Si:Al=2.0) over
the temperature range 100-500 K. We apply the kinetic Monte Carlo
random walk model, with activation energies derived from a new
zeolite-hydrocarbon potential energy surface (PES). An Arrhenius
fit yields the apparent activation energy Ea = 41 kJ mol-1
as compared with the previously determined experimental values
14-27 kJ mol-1.
Minimum energy paths from the new PES demonstrate ``cartwheel''
and ``skateboard'' hopping mechanisms for benzene in Na-Y.
Analysis of the results suggests that activation energies
from long length scale diffusion measurements, e.g. pulsed field
gradient NMR, should be interpreted as site-to-window
activation energies; whereas those from short length scale
experiments, e.g. spin lattice relaxation NMR, correspond to
intracage site-to-site activation energies.
Prof SM Auerbach
18 June 2004