The infinite-dilution activity coefficients of cyclohexane, cyclohexene, and benzene in N,N-dimethylformamide, N-methylpyrrolidone, N,N-dimethylacetamide, phenyl acetate, and dimethyl malonate have been determined at temperatures ranging from 40 to 80 °C, by non-steady-state gas chromatography. From these data, the limiting selectivity−solvency properties for cyclohexane−benzene, cyclohexene−benzene, and cyclohexane−cyclohexene, in the presence of the aforementioned solvents, are studied, and the solvents tested are considered for the cyclohexane−cyclohexene−benzene separation by extractive distillation. According to the results, N,N-dimethylacetamide seems to be an adequate solvent for the cyclohexane−benzene and cyclohexene−benzene separations. The separation of cyclohexane−cyclohexene is the most difficult, in spite of the difference of boiling points, much higher than for cyclohexane−benzene.

The infinite-dilution activity coefficients of cyclohexane, cyclohexene, and benzene in four solvents, isophorone (CAS 78-59-1), dimethyl sulfoxide (CAS 67-68-5), dimethyl succinate (CAS 106-65-0), and propylene glycol (CAS 57-55-6), have been determined at temperatures ranging from 40 °C to 80 °C, by non-steady-state gas chromatography. These solvents are used commercially in the separation of mixtures of these hydrocarbons by extractive distillation, so infinite-dilution selectivities have been calculated and studied in relation to this separation. The experimental activity coefficients were compared with those calculated by the UNIFAC method.