A model for mass transport in biporous packed beds was used to
simulate axial concentration
profiles of n-hexane measured with positron emission
profiling (PEP). Axial dispersion dominated
the mass transport behavior in the medium-pore zeolites H-mordenite and
H-ZSM-5. Comparison
of simulations of experiments using the small-pore zeolites (i.e.,
H-ZSM-22 and H-ferrierite)
shows that micropore diffusion limitation contributes significantly to
the peak width of the PEP
profiles. As a result, new micropore diffusion constants for
H-ZSM-22 and H-ferrierite are
reported. The prospects for studying the reaction kinetics of the
hydroisomerization reaction of
alkanes is discussed.