Cyclohexanol is an important intermediate for producing adipic acid and ε-caprolactame, as well as nylons. Furthermore, cyclohexene directly hydrated to cyclohexanol overcomes the shortcomings of the traditional methods and is attracting more and more attention, but due to the solubility of cyclohexene in water, it still suffers from rather low equilibrium conversion and a fairly slow reaction rate. The addition of isophorone can significantly increase the solubility of cyclohexene in the aqueous phase, and thus, it is appropriate as a cosolvent for the direct hydration of cyclohexene to cyclohexanol by extractive distillation. It is known from previous literature that cyclohexene hydration is under medium and high pressure. In this study, the vapor−liquid equilibrium (VLE) data for the vapor−liquid phase equilibrium of ternary systems cyclohexene + cyclohexanol + isophorone and quaternary systems cyclohexene + water + cyclohexanol + isophorone were measured at 500 kPa. The NRTL, Wilson, and UNIQUAC models were employed to correlate the binary VLE data of water−cyclohexene, water−cyclohexanol, water−isophorone, cyclohexene− cyclohexanol, cyclohexene−isophorone, and cyclohexanol−isophorone.

Vapor–liquid equilibrium (VLE) measurements have been performed for cyclohexene–isophorone and cyclohexanol–isophorone binary systems at 101.3 kPa. The L–W test method confirmed the thermodynamic consistency of the experimental VLE data for the binary systems. These data are compared to theoretical predictions by COSMOtherm and overall show good agreement. Due to the success of the COSMOtherm predictions, theoretical data for the cyclohexene–cyclohexanol–isophorone ternary system is obtained.