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Isotope exchange technique for measurement of gas adsorption equilibria and kinetics
Author(s) -
Rynders R. M.,
Rao M. B.,
Sircar S.
Publication year - 1997
Publication title -
aiche journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.958
H-Index - 167
eISSN - 1547-5905
pISSN - 0001-1541
DOI - 10.1002/aic.690431009
Subject(s) - molecular sieve , chemistry , zeolite , adsorption , mass transfer , diffusion , isothermal process , thermal diffusivity , carbon fibers , analytical chemistry (journal) , molecular diffusion , selectivity , thermodynamics , chromatography , organic chemistry , materials science , catalysis , metric (unit) , physics , operations management , composite number , economics , composite material
The isotope exchange technique (IET) can be used to simultaneously measure multicomponent gas adsorption equilibria and self‐diffusivities of the components in a single isothermal experiment without disturbing the overall adsorbed phase. An experimental protocol for the IET and corresponding data analysis procedures is described. Isotherms and self‐diffusivities for adsorption of N 2 as a pure gas were measured on commercial samples of a carbon molecular sieve and a 4‐Å zeolite using IET, as well as those of O 2 and N 2 from their binary mixtures. The carbon molecular sieve did not exhibit thermo‐dynamic selectivity for air separation, but had a kinetic selectivity of O 2 over N 2 Mass‐transfer resistances for self‐diffusion of N 2 and O 2 on the carbon molecular sieve were controlled by pore mouth restrictions in the carbon, but those for adsorption of N 2 into the 4‐Å zeolite by Fickian diffusion inside the adsorbent. A linear driving force model described the uptakes of N 2 and O 2 in the carbon molecular sieve. The Fickian diffusion model described the N 2 uptake in the 4‐Å zeolite. Mass‐transfer coefficients for both O 2 and N 2 on the carbon molecular sieve increased linearly with increasing gas‐phase partial pressure of these gases, and the pressure of O 2 did not affect mass‐transfer coefficients for N 2 . The self‐diffusivity of N 2 in the 4‐Å zeolite decreased with increasing adsorbate loading.