KINETIC-STUDY OF MTBE LIQUID-PHASE SYNTHESIS USING C-4 OLEFINIC CUT

The liquid-phase addition of methanol to isobutene to give methyl tert .-butyl ether (MTBE) on the ion exchange resin Bayer Catalyst K2631 ha s been studied using a C-4 olefinic cut as the source of isobutene. Ra te data were obtained free of mass transfer influence in a continuous differential reactor operated at 1.5 MPa and 45-90 degrees C. Data sho w that isobutene has an enhancing effect on the rate whereas methanol has an inhibitory one. As alcohol-olefin-ether mixtures behave non-ide ally, kinetic analysis has been performed by using the UNIFAC liquid-p hase activities of isobutene, methanol and MTBE. The experimental data can be described by a three-parameter expression based on an Eley-Rid eal mechanism in which methanol, adsorbed on one catalytic center, rea cts with isobutene from solution to give the ether adsorbed on one cen ter. Surface reaction is the rate-limiting step, and an additional cen ter takes part in this step. The kinetic model emphasizes the relevant role of MTBE in the reaction, which competes for the active centers w ith the methanol. An activation energy of 81.1 +/- 4.2 kJ/mol, in good agreement with literature values, was found.