Etherification of isobutene with 1-propanol and 2-propanol Review Article

The differential conversions and equilibrium composition in the etherification of isobutene with 1-propanol and 2-propanol were measured. A macroreticular, strong cation exchange resin was used as a catalyst. A plug flow reactor was used for differential experiments and a batch reactor for the equilibrium experiments. In the differential experiments the only side reaction observed was the dimerisation of the isobutene. The etherification and dimerisation reactions were dependent on temperature and on the isobutene/alcohol mole ratio. Both reactions were faster with 1-propanol than with 2-propanol, which could be due to the different steric hindrance of the reacting alcohols or forming intermediates. At a constant temperature the reaction rate of the etherification increased with the isobutene/alcohol mole ratio, reached a maximum value and then started to decrease. The equilibrium constants for the formation of propyl-tert-butyl ether (PTBE) and iso propyl-tert-butyl ether (IPTBE) from 1-propanol, 2-propanol and isobutene were measured in a batch reactor at temperatures of 313–353 K. As for the reaction rates in the differential experiments, the equilibrium constants were also significantly lower in the formation of IPTBE than in the formation of PTBE. The standard enthalpy and entropy change of the reaction were calculated from the equilibrium results to be −26.4 kJ mol−1 and −53.0 J mol−1K−1 for the formation of PTBE and −25.5 kJ mol−1 and −71.3 J mol−1K−1 for the formation of IPTBE, respectively.