The experimental determination of K-values and activity coefficients by gas-liquid partition chromatography

Abstract

A brief review of some important theoretical aspects of Gas-Liquid Partition Chromatography is presented, emphasizing in particular parameters connected with solution behavior. Preliminary to measurements conducted on light hydrocarbon systems, an apparatus was built trying to insure the best possible conditions to obtain physical and thermodynamic data through chromatographic techniques. The apparatus is described in detail. Experiments were performed with light hydrocarbons methane through normal butane as the solute and normal dodecane as the stationary phase, in a range of temperatures from 0 to 30°C, and pressures from 20 to 40 psia. The experimental equipment and technique were such that the concentration of the solute approached infinite dilution. Vaporliquid equilibria ratios or K-values obtained from these experiments have been compared with values obtained from static tests. The agreement range from poor agreement in the case of methane to excellent agreement in the case of propane and n-butane. The study of a system used in extractive distillation (n - butane, butenes, and Madiene 1,3 in furfural) is presented. Values for the activity coefficients at infinite dilution were obtained, which show inner consistency, and which are in substantial agreement with those reported by Mertes. This study covered a range of temperatures from -20 to 40°C and pressures from 20 to 40 psia. The variation of the activity coefficients with temperature was used to evaluate the differential heats of solution of the hydrocarbons in furfural. Other related thermodynamic properties such as excess free energy of solution, relative volatilities, etc., were calculated and are reported.