Vapor and liquid equilibria in porous media

The alteration of the vapor–liquid equilibrium (VLE) of volatile organic mixtures by placing porous media at the liquid–vapor interface was studied. Kelvin, assuming ideal behavior of fluids, first introduced the vapor pressure of liquid over a meniscus as a function of its surface tension and the radius of the curvature. A thermodynamic model (SSmod model) predicting the VLE of non-ideal organic mixtures in porous media was developed as a function of pore sizes. The model was used to predict the VLE of two aqueous alcohol solutions, ethanol–water and propanol–water, and two binary solutions, methanol–isopropanol and ethanol–n-octane. Experiments were conducted using sintered metal and fritted glass plates as porous media, and the results were compared with the model predictions. Using the actual diameter of the porous media, the model prediction showed good agreement with the experimental results.