Kinetic study of mtbe liquid-phase synthesis using C 4 olefinic cut

Abstract

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