Phase behavior of symmetric binary mixtures with partially miscible components in spherical pores. Density functional approach

Abstract

We investigate adsorption in spherical pores of model symmetric binary mixtures exhibiting demixing in bulk phase, by using a density functional approach. Our focus is on the evaluation of the upper part of the coexistence envelope for the first-order phase transitions in adsorbed fluids, and the lines separating mixed and demixed phases. We show that the scenario for phase transitions is sensitive to the pore radius. This parameter can change the type of the phase diagram for the confined fluid comparing to its bulk counterpart. In particular, for not very big spherical pores and for strong wall–fluid interactions, the capillary condensation between mixed phases is strongly depressed, such that only condensation from mixed gas to demixed liquid phase terminating at tricritical point is observed.