Studies on the physical adsorption equilibria of gases on porous solids over a wide temperature range spanning the critical region-adsorption on microporous activated carbon

Adsorption equilibria of nitrogen and methane on microporous ( < 2 nm) acti vated carbon were measured for a wide temperature range (103-298 K) spannin g the critical region. Information relating to Henry constants, the isoster ic heat of adsorption, and the amount of limiting adsorption were evaluated . Ali isotherms show type-I features for both sub- and supercritical temper atures. A new isotherm equation and a consideration for the importance of t he effect of the adsorbed phase volume allow this kind of isotherms to be m odeled satisfactorily. The model parameter of the saturated amount of absol ute adsorption (n(t)(o)) equals the limiting adsorption amount (n(lim)), le aving the physical meaning of the latter clarified, and the exponent parame ter (q) proves to be an appropriate index of surface heterogeneity.