Isothermal vapor–liquid equilibria of benzene-dimethylformamide and toluene-dimethylformamide systems using a small modified ebulliometer

A small modified ebulliometer, whose structure is both simple and rational, has been proposed for the reliable measurement of vapor–liquid equilibrium. The ebulliometric method was used to determine isothermal VLE data for the dimethylformamide-benzene binary system at 343.2, 353.2, and 363.2 K and for the dimethylformamide-toluene binary system at 353.2, 363.2, 373.2, and 383.2 K. The parameters of the NRTL and Wilson models for the two binary systems have been obtained by calculating equilibrium compositions of the liquid and vapor phases with the experimental equilibrium temperatures, pressures and feed compositions. They were expressed as a function of the temperature from 343.2 to 363.2 K and from 353.2 to 383.2 K. Correlation results were satisfactory. Meanwhile, the major factors influencing the value of the mean evaporation coefficient, f̄, of the ebulliometer were investigated and the effect of the error f̄ of on the value of calculated equilibrium liquid and vapor compositions was examined. The results will allow a wide application of this ebulliometer to the determination of reliable VLE data.