The six-component system cyclohexene + water + cyclohexanol + cyclohexane + formic acid + formic acid cyclohexyl ester is currently being studied with the aim of carrying out the reaction of cyclohexene and water to cyclohexanol in a reactive distillation (RD) column. Because the direct reaction path of cyclohexene hydration is strongly limited by slow reaction rates with the known catalysts, an intermediate ester-formation step with formic acid was included in the studies. The challenge that this six-component system poses for a reactive separator such as an RD column lies in the liquid-liquid phase splitting behavior. This adds a third effect besides reaction and distillation. Cyclohexane is included in these studies to represent any inert C-6 components present under industrial conditions. To be able to design an RD column, 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.