SCOPE AND LIMITATIONS OF MECHANISTIC INFERENCES FROM KINETIC-STUDIES ON ACIDIC MACROPOROUS RESINS - THE MTBE LIQUID-PHASE SYNTHESIS CASE

It has been hypothesized hitherto that the liquid-phase synthesis of M TBE on ion-exchange resins proceeds quasi-homogeneously in excess meth anol by an ionic mechanism whose rate-limiting step is the protonation of the alkene, and quasi-heterogeneously at very low methanol content likely by a concerted proton transfer involving adsorbed reactants. H owever, recent knowledge of the reaction involving the effect of the n on-ideality of the liquid phase on the kinetics of the reaction, and t he inhibitor effect of MTBE on the reaction rate, in addition to new d ata on byproducts formation, suggest that MTBE synthesis can be looked at as a quasi-heterogeneous catalysis independently of the methanol c ontent of the liquid phase. Moreover, a transition between a Eley-Ride al mechanism and an Langmuir-Hinshelwood one can be assumed as the met hanol concentration of the liquid phase decreases.