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Modeling the concentration dependence of diffusion in zeolites. I. Analytical theory for benzene in Na-Y
 

Summary: Modeling the concentration dependence of diffusion in zeolites. I.
Analytical theory for benzene in Na-Y
Chandra Saravanan
Department of Chemistry, University of Massachusetts, Amherst, Massachusetts 01003
Scott M. Auerbacha)
Departments of Chemistry and Chemical Engineering, University of Massachusetts, Amherst,
Massachusetts 01003
Received 12 June 1997; accepted 14 August 1997
We have developed an analytical expression for the diffusion coefficient of benzene in Na-Y at finite
loadings in terms of fundamental rate coefficients. Our theory assumes that benzene molecules jump
among SII and W sites, located near Na ions in 6-rings and in 12-ring windows, respectively. We
assume that instantaneous occupancies in different supercages are identical, a mean field
approximation yielding D 1
6k a2
where a 11 ┼ is the mean intercage jump length and 1/k is
the mean supercage residence time. We show that k Ěk1ĚP1 , where P1 is the probability of
occupying a W site, k1 is the total rate of leaving a W site, and is the transmission coefficient for
cage-to-cage motion. We assume 1
2 for all loadings, and derive analytical formulas for the T and
dependencies of k1 and P1 , assuming that SII and W site occupancies are either 0 or 1 and that

  

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

 

Collections: Chemistry