Studies on pore systems in catalysts: IX. Calculation of pore distributions from the adsorption branch of nitrogen sorption isotherms in the case of open cylindrical pores A. Fundamental equations

Abstract

A study is made of the possible cause for sorption hysteresis in the case of cylindrical pores of uniform diameter, open at both ends. By means of simple thermodynamic reasoning, the equation of Cohan for capillary condensation in open cylinders during adsorption, is shown not to be suitable for quantitative work. After the introduction of the t curve of multimolecular adsorption, a model is given for the occurrence of hysteresis in this special case. From this model, quantitative relations are derived for the spontaneous filling of pores during adsorption, as well as for the evaporation of capillary condensate on desorption, in dependence of the pore radius. The relation between these equations and the work of Foster and Derjaquin is discussed.