Molecular mechanisms of MTBE synthesis on a sulphonic acid ion exchange resin

Abstract

In the present work, molecular mechanisms of methyl t-butyl ether (MTBE) synthesis by methanol addition to isobutene in the gaseous and liquid phases are presented as an example of general and specific acid catalysis by sulphonated ion exchange resins, respectively. In the liquid phase and in a reaction medium with excess methanol (specific acid catalysis), the literature provides enough experimental evidence to support an ionic mechanism whose rate-determining step is olefin protonation. As an example of general acid catalysis, a concerted mechanism with a cyclical intermediate of six centers is proposed for this reaction in gaseous phase. It is based on the LHHW kinetic model determined for the reaction that explains rate data in a statistically significant fashion. Analysis of the significance of the LHHW model shows that it is thermodynamically consistent. Therefore, we can assume that the kinetic model is a simplified picture of the molecular process. The bibliography gives supplementary experimental evidence supporting the proposed concerted mechanism.