KINETICS OF THE LIQUID-PHASE SYNTHESIS OF ETHYL TERT-BUTYL ETHER (ETBE)

The liquid-phase addition of ethanol to isobutene to give ethyl tert-b utyl ether (ETBE) on the ion exchange resin Lewatit K2631 has been stu died. Rate data were obtained free of mass transfer influence in a con tinuous differential reactor operated at 1.6 MPa and 40-90-degrees-C, measuring steady-state conversions <10% for ethanol-isobutene and etha nol-isobutene-ETBE feeds. The reaction is highly temperature-sensitive . Isobutene has an enhancing effect on the rate whereas ethanol has an inhibitor one. Besides, low ETBE concentrations enhance the reaction but as chemical equilibrium is approached the ether shows an inhibitor effect, as expected. As alcohol-olefin-ether mixtures behave nonideal ly, kinetic analysis has been performed by using the UNIFAC liquid-pha se activities of isobutene, ethanol, and ETBE. The best kinetic model stems from an Eley-Rideal mechanism in which the ethanol, adsorbed on one center, reacts with the isobutene from solution to give the ether adsorbed on one center. Surface reaction is the rate-limiting step. Tw o additional centers take part in this step.