Direct method for evaluation of BET adsorbed monolayer capacity

Conventional method for measurement of the BET specific surface area involves guessing of a pressure range on the adsorption isotherm where the BET plot is linear and the BET equation appropriately fits the experiment. We report a simple and universal technique for normalization of adsorption isotherms with (1 - p/p degrees)(-k), k > 1 that directly yields the so-called Point B. This is the point on the adsorption isotherm where the adsorption uptake is equal to the BET adsorbed monolayer capacity. As a multipoint technique, this method is free of the pressure range guessing and, consequently, free from traditional linearization. It allows proper automatic characterization for majority of porous solids, including materials with pore distribution in the nanometer range where the BET pressure range guessing is questionable due to overlapping of multilayer adsorption and capillary condensation. (C) 2017 Elsevier Inc. All rights reserved.