Study of the Chemical Equilibrium of the Liquid-Phase Dehydration of 1-Hexanol to Dihexyl Ether

The equilibrium constants of the liquid-phase dehydration of 1-hexanol to dihexyl ether (DNHE) and water were determined in the temperature range of (423 to 463) K on Amberlyst 70. The equilibrium constants of the two main side reactions, DNHE decomposition to 1-hexene and 1-hexanol and isomerization of 1-hexene to 2-hexene, were also studied. The etherification reaction proved to be slightly exothermic, with an enthalpy change of reaction of −(9.5 ± 0.2) kJ·mol −1 at 298 K. From this value, the standard formation enthalpy and molar entropy of DNHE were computed to be −(478.6 ± 0.8) kJ·mol −1 and (517.4 ± 0.5) J·K −1 ·mol −1, respectively. A correction concerning the effect of pressure on the entropy proved to be necessary when computing liquid-phase entropy from gas-phase data. The isomerization of 1-hexene to 2-hexene is exothermic, whereas the decomposition of DNHE is endothermic.