Measurement of activity coefficients at infinite dilution using gas-liquid chromatography. 9. Results for various solutes with the stationary phases 2-pyrrolidone and N-methylformamide

The selection of the most suitable selective solvent for separation processes such as extraction or extractive distillation plays an important role in the economical design. Since the largest deviation from ideality is observed at infinite dilution, limiting activity coefficients (γ∞) provide a useful tool for the optimal choice of the selective solvent (entrainer). Therefore, activity coefficients at infinite dilution have been measured for 31 solutes (alkanes, alkenes, cyclic hydrocarbons, aromatic hydrocarbons, alcohols, ketones, ethers, and halocarbons) in the solvents 2-pyrrolidone and N-methylformamide. The measurements were carried out with the help of gas-liquid chromatography (GLC) at four temperatures, (30, 40, 50, and 60) °C. The γ∞ values are compared with published data. Furthermore, the observed temperature dependence of the limiting activity coefficients is confirmed using excess enthalpy data. To verify the application as an entrainer, selectivity and capacity of the investigated solvents are compared to those of similar structured solvents such as N-methyl-2-pyrrolidone and N,N-dimethylformamide.