Adsorption equilibrium of solvent mixtures on silica gel and silica gel coated ceramics

This paper presents the sorption isotherms of the mixtures 2-propanol/water and n-heptane/methylcyclohexane as well as the isotherms of the pure solvents on the adsorbent silica gel and silica gel coated ceramics. The equilibrium data were obtained gravimetrically via an experimental set-up based on the through flowing method. The single component isotherms of all solvents are type IV of Brunauer classification, indicating strong interactions typically with a mesoporous solid. Due to small differences in molecule size, physical properties and interaction forces to silica gel, the mixtures of n-heptane and methylcyclohexane show a nonselective adsorption behavior over the complete composition range. An unusual phenomena has been observed for the adsorption equilibrium of the 2-propanol-water mixtures: at low relative pressures and low alcohol contents, 2-propanol is preferentially bounded so that the selectivity behavior according to the vapor liquid equilibrium of the fluid mixture is entirely inverted. (C) 1999 Elsevier Science S.A. All rights reserved.