The ternary system cyclohexene + water + cyclohexanol is currently being studied with the aim of carrying out the reaction of cyclohexene and water to cyclohexanol in a reactive distillation column. The challenge this system poses for such a reactive separator lies in the liquid-liquid phase splitting behavior, which adds a third effect in addition to reaction and distillation. Cyclohexane is added as a fourth component into these studies, representing any C-6 inerts. To be able to describe the activities of all four components, measurements were conducted of the liquid-liquid and vapor-liquid equilibria, and appropriate NRTL parameters matching both vapor-liquid and liquid-liquid phase splitting behavior were identified.