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.