Liquid-Liquid Phase Equilibria and Capillary Condensation in Confined Nanopores

摘要

Capillary condensation and phase diagrams of gases confined in nanoporous materials are of industrial and technological importance in gas adsorption operations with molecular sieves, membranes, and nanomaterials such as aerogels, carbon nanotubes, fullerenes, and nanopowders. The simplest fluid mixtures that can exhibit liquid-liquid phase separation are the non-additive hard sphere mixtures. This type of systems is studied inside random porous materials of nanometer-sized pores. Both Monte Carlo simulation and integral equation theory are used to investigate a series of mixtures of different nonadditivities Δ (from 0 to 0.2, and up to 0.4). We notice that the lower critical solution temperature (LCST) in pores is "lowered" as compared to the bulk case, even for simple gases such as hard spheres, in conformity to the experiments on helium 4 in aerogels.