Pore structure analysis by oxygen adsorption. I. t-curves and methods of analysis

Abstract

Two new approaches to pore structure analysis were developed by Brunauer and his coworkers: a method for the analysis of micropores, and a method for the analysis of wider pores in which capillary condensation occurs. The two methods were then applied to the analysis of a variety of porous adsorbents, using nitrogen and water vapor adsorption-desorption isotherms, and the pore structure results were compared. The present work was undertaken primarily to find out whether a given adsorbate at two different temperatures gives the same results for the same adsorbent. Oxygen was selected as the adsorbate partly because two temperatures for the isotherms, 77.3 and 90 K, were conveniently available, partly in order to compare the oxygen results with the nitrogen and water vapor results. The prerequisite for the analysis is to have appropriate t-curves, i.e., curves which give the statistical thickness of the film adsorbed on nonporous adsorbents as a function of the relative pressure. Using four nonporous adsorbents, t-curves were determined for oxygen at 77.3 and 90K. Besides presenting the t-curves, the paper also describes the methods of analysis employed at the two temperatures.