Liquid-phase adsorption of binary ethanol–water mixtures on high-silica adsorbents

Abstract

A study was made of the adsorption of ethanol–water mixtures on adsorbents with high silicon-to-aluminium ratios and different structures. The shape of the resulting excess isotherms changes dramatically with the geometry and the growth of the channels and cavities inside the adsorbents. It is possible that water association within the free volume of the adsorbents causes the loss of efficiency of separation, although the adsorbents are distinctly hydrophobic. While the activity coefficients of the adsorbed phase for small channel systems (ZSM-5) show positive deviations from Raoult's law they change in the order ZSM-5, ZSM-35, US-Ex-zeolite with higher free adsorption volumes in the direction of the free liquid.