ABSTRACT
With the recent interest in the development of new adsorbents and catalysts for gas separation as
well as chemical reaction applications, the problem of accurately estimating the pore-size
distribution (PSD) of microporous materials has achieved a certain imperative significance. This
is particularly so because of the strong dependence of adsorption and transport characteristics on
the structure and pore size of a material. By common convention, microporous materials are
those with pore sizes of width less than 2.0 nm. A large number of such materials are in use
today for a wide variety of applications. These include activated carbons, molecular sieve
carbons in the form of pellets as well as cloth fibers, silica-based materials such as MCM-41,
activated alumina, aluminophosphates, pillared clays, polymeric resins, and zeolites. The wide
variety of microporous materials occurring in chemical processes is equally matched by the
number of experimental techniques for PSD estimation which have been developed over the
years. Some examples are mercury porosimetry [1], BET analysis [2], nuclear magnetic
resonance (NMR) spin-lattice relaxation [3], x-ray diffraction (XRD), and calorimetry. However,
there are certain restrictions on the type of material and the minimum pore size that can be
analyzed by these techniques. By far, the most general experimental method today concerns the
measurement of an adsorption isotherm of a fluid (usually nitrogen or argon at its normal boiling
point) on the sorbent material.
