The isotope exchange technique (IET) can be used to simultaneously mea
sure multicomponent gas adsorption equilibria and self-diffusivities o
f the components in a single isothermal experiment without disturbing
the overall adsorbed phase. An experimental protocol for the IET and c
orresponding data analysis procedures is described. Isotherms and self
-diffusivities for adsorption of N-2 as a pure gas were measured on co
mmercial samples of a carbon molecular sieve and a 4-Angstrom zeolite
using IET, as well as those of O-2 and N-2 from their binary mixtures.
The carbon molecular sieve did not exhibit thermodynamic selectivity
for air separation, but had a kinetic selectivity of O-2 over N-2. Mas
s-transfer resistances for self-diffusion of N-2 and O-2 on the carbon
molecular sieve were controlled by pore mouth restrictions in the car
bon, but those for adsorption of N, into the 4-Angstrom zeolite by Fic
kian diffusion inside the adsorbent. A linear driving force model desc
ribed the uptakes of N-2 and O-2 in the carbon molecular sieve. The Fi
ckian diffusion model described the N-2 uptake in the 4-Angstrom zeoli
te. Mass-transfer coefficients for both O-2 and N-2 on the carbon mole
cular sieve increased linearly with increasing gasphase partial pressu
re of these gases, and the pressure of O-2 did nor affect mass-transfe
r coefficients for N-2. The self-diffusivity of N-2 in the 4-Angstrom
zeolite decreased with increasing adsorbate loading.