Measurement of activity coefficients, mass-transfer coefficients and diffusion coefficients in multicomponent liquid mixtures by reversed-flow gas chromatography

Abstract

Reversed-flow gas-chromatography sampling is a new method for studying heterogeneous catalysis, diffusion, adsorption and evaporation. We report its application to the simultaneous determination of mass-transfer coefficients for the evaporation of multicomponent liquid mixtures and the diffusion coefficients of vapours from these liquid mixtures into the carrier gas. Using suitable mathematical equations the gaseous equilibrium concentration of each component under study, in the pure state and in the mixture, has been determined. Using these equilibrium concentrations, together with the mass-transfer coefficients and diffusion coefficients already determined, activities and activity coefficients were calculated. The liquid mixtures used were: n-hexane–n-heptane, n-hexane–methanol, n-hexane–ethanol, n-hexane–butan-2-ol, n-hexane–acetone, n-hexane–methanol–butan-2-ol, n-hexane–ethanol–butan-2-ol and n-hexane–methanol–butan-2-ol–water. All the activity coefficients found were compared with those calculated by the UNIFAC (universal quasichemical functional-group activity coefficients) method.