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Analytical theory of benzene diffusion in Na-Y zeolite Scott M. Auerbach

Summary: Analytical theory of benzene diffusion in Na-Y zeolite
Scott M. Auerbach
Departments of Chemistry and Chemical Engineering, University of Massachusetts, Amherst,
Massachusetts 01003
Received 16 October 1996; accepted 3 February 1997
We have developed an analytical expression for the diffusion coefficient of benzene in Na-Y at
infinite dilution in terms of fundamental rate coefficients, which has been confirmed by extensive
kinetic Monte Carlo simulations. This model assumes that benzene jumps among SII and W binding
sites, located near Na ions in 6-rings and in 12-ring windows, respectively. Our diffusion theory
is based on D 1
where a 11 is the intercage length and k is the cage-to-cage rate
coefficient. We have determined that k k SIIW 1
23 1 k WW /k WSII) , a finding that
has resolved discrepancies between theory and simulation and has suggested new interpretations of
benzene diffusion in Na-Y. When (T) k WW /k WSII) is between 0 and 1, the factor
3 1 (T) counts the number of thermally allowed target sites for cage-to-cage motion.
Alternatively, when (T) 1, benzene mobility is interpreted as interstitial diffusion, wherein k is
controlled by the probability of W site occupancy multiplied by the rate of WW jump processes.
This limit is expected to arise with benzene loadings of four molecules per supercage. 1997


Source: Auerbach, Scott M. - Department of Chemistry, University of Massachusetts at Amherst


Collections: Chemistry