ABSTRACT:One of the essential foundations of the classical Polanyi adsorption potential theory has been assessed with respect to the invariability with temperature of the so-called characteristic adsorption curves. This has been achieved both numerically and experimentally for nitrogen and numerically for argon adsorption onto spherical as well as onto cylindrical mesopore entities at 77.35 K and 87.29 K, respectively. The adsorption results in these spherical and cylindrical pores were obtained from an application of the Broekhoff-de Boer equation and compared to nitrogen experimental sorption data obtained from cylindrical SBA-15 and spherical SBA-16 pore systems. The characteristic curves obtained in both ways were consistent with each other.

The Kelvin equation can approximately describe the conditions required for the occurrence of capillary condensation-evaporation phenomena. Nonetheless, nucleation phenomena imply noteworthy deviations from the Kelvin prediction. Nucleation occurs in porous media during liquid-vapor transitions and this phenomenon certainly influences the appearances of adsorptiondesorption isotherms. Nucleation plays indeed a capital role during capillary condensation whilst is mostly absent during capillary evaporation.