Adsorption of mixed vapors on solids—I Graphon

Abstract

The adsorption isotherms for ethanol-cyclohexane, ethanol-benzene, and benzene-cyclohexane vapor mixtures on Graphon at 20,30 and 40°C were measured at constant total pressure. The adsorption isotherms for the pure components were also obtained. Isosteric heats of adsorption were calculated for the pure adsorbates on Graphon. The binary vapor adsorption isotherms were compared to the pure component isotherms. The adsorbate-vapor composition diagrams for benzene-cyclohexane mixtures on Graphon all contained adsorption azeotropes. Very little selective adsorption of either component occurred. In general, benzene and cyclohexane were selectively adsorbed from benzene-ethanol and cyclohexane-ethanol mixtures on Graphon. The temperature dependence of the selectivity for the systems studied followed no consistent trend. Comparison of the binary vapor adsorption isotherms with the solution adsorption isotherms indicated that selectivity is generally higher in adsorption from solution. The experimental binary vapor adsorption isotherms compared favorably with those calculated from the pure vapor adsorption isotherms using the ideal adsorbed solution model. It was found that the adsorbed solutions were slightly non-ideal for benzene-cyclohexane mixtures on Graphon. The non-ideal behaviour observed for benzene-ethanol and cyclohexane-ethanol mixtures on Graphon was attributed to the presence of benzene or cyclohexane disrupting the hydrogen-bonded structure of ethanol on the Graphon surface.