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Summary: VOLUME 81, NUMBER 26 P H Y S I C A L R E V I E W L E T T E R S 28 DECEMBER 1998
Direct Measurement of Intercage Hopping in Strongly Adsorbing Guest-Zeolite Systems
D. E. Favre,1
D. J. Schaefer,1
S. M. Auerbach,2
and B. F. Chmelka1,
*
1
Department of Chemical Engineering, University of California, Santa Barbara, California 93106
2
Departments of Chemistry and Chemical Engineering, University of Massachusetts, Amherst, Massachusetts 01003
(Received 24 July 1998)
Solid-state exchange 13
C NMR has been used to measure directly discrete intercage hopping of
strongly adsorbed molecules on a nanoporous zeolite. Such intercage motions represent the molecular
transport events that are central to macroscopic diffusion of guest molecules through zeolite pore spaces.
Apparent activation energies of 73 and 76 kJ mol have been measured for intra- and intercage hopping,
respectively, of benzene molecules on Ca-Y zeolite. Exchange NMR measurements at 338 to 368 K
yield benzene self-diffusion coefficients from 10219
10218
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