Journal of the Society of Powder Technology, Japan

On the basis of a cylindrical pore model, the estimation correlation for determining permeability in a Knudsen flow regime k_F by using that in a continum flow regime k_V was empirically investigated.
Assuming that the k_F values of porous media having the same k_V values are also the same, the relationship between k_F/k_V and equivalent pore radius r_e for any given porous media was converted to that of a packed bed with spherical particles.
The expression mentioned above fitted the data cited from the literature for porous media with a uniform structure or with a structure similar to that of a cylinder, accurately enough for practical usage.

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The Hüttig-type adsorption equation for mixed gas adsorption is derived based on the model where the molecules in the 1st layer are localized and the molecules in the 2nd or higher layers behaved as gas-like molecules in a different potential compared to that of gas molecules (similar to the free volume model in liquid). This equation was applied to the experimental isotherms of coadsorption. The monolayer values and adsorption constants obtained from the BET equation applied to experimental single component isotherms were necessary to apply the extended BET equation on mixed gas adsorption to the experimental isotherms. However, in the Hüttig-type adsorption equation, only the component isotherm and its application to the experimental isotherms was necessary. The data used for comparison were the amount of adsorption of a certain component against its relative pressure, the pressure of another component being constant and that of the adsorbed amount of a certain component against the relative pressure of another component, and the pressure of a certain component being constant in the coadsorption or (O₂-Ar) and (O₂-N₂) on chromia gel at-186°C. The isotherms calculated from the Hüttig-type adsorption equation agreed reasonably well with the experimental ones in the use of the parametric values, i. e., monolayer values, B₁, adsorption constants, C₁ and C₂ obtained from the application of the proposed adsorption equation to the experimental ones. The monolayer values obtained separately, from the experimental component isotherms, agreed well with each other, within 20%.

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