Kinetics of methyl tertiary butyl ether liquid phase synthesis catalyzed by ion exchange resin—I. Intrinsic rate expression in liquid phase activities

Abstract

The microkinetics for the liquid phase synthesis of methyl tertiary butyl ether (MTBE) from methanol and isobutene using a macroporous sulfonic acid ion exchange resin as catalyst (Amberlyst 15, CVT resin) were determined experimentally in a continuous stirred tank reactor in the temperature range 323–363 K at 2.1 MPa. The reaction proceeds within the gel phase of the microspheres as the rate-controlling step overlapped by a multiple sorption equilibrium between components in the macropore liquid and the gel phase, where methanol is highly selectively sorbed. The experimental results can be described by a three-parameter model based on a Langmuir—Hinshelwood rate expression in liquid phase activities from the UNIQUAC method. The forward reaction is proportional to the activity ratio of isobutene to methanol (quasi-autocatalytic in methanol). The reverse reaction is first-order in MTBE and negative second-order in methanol (product inhibition). The activation energy was determined to 92.4 kJ/mol. No pressure dependence could be observed. The developed microkinetic model is independent of the degree of cross-linking of the resin in the investigated range 7.5–20% DVB by weight. The formation of isobutene dimers, the main by-product, was only observed if internal mass transfer influenced the rate of reaction.