Vapor-liquid equilibrium in capillary distillation

Abstract

With the advent of capillary distillation (12, 28, 29 30, 31,32) vapor-liquid equilibrium data of solutions in small capillaries have become important. These data for various alcohol-water mixtures have been obtained and published recently (13). Although the experimental method used is simple, it is very time-consuming. Based on the theory developed by G. C. Yeh (33), the authors have computed vapor-liquid equilibria of eighty-four solutions by taking into account the effects of the dispersion interactions and of the polar interactions at solid-liquid interfaces and the effect of the curvature of vapor-liquid interfaces upon the surface tensions and the vapor pressures of the component liquids in solutions under isobaric and isothermal conditions. The systems studied include hydrocarbon solvents, halogenated hydrocarbons, organic sulfur compounds, monohydric alcohols, phenols, ketones, amines, esters and water. Most systems show an increase in relative volatility although some systems show a decrease or even a reversal in relative volatility. The predicted capillary vapor-liquid equilibrium compositions of each system were compared with the normal vapor-liquid compositions. In addition, the predicted values were compared with the experimental data for monohydric alcohol-water systems. The agreement is good, considering the simplicity of the theory. The accuracy of the theoretically predicted vapor-liquid equilibria for other systems has not yet been established experimentally. The theory and the method of calculation developed may apply also to multicomponent solutions.