KINETICS OF METHYL TERTIARY BUTYL ETHER LIQUID-PHASE SYNTHESIS CATALYZED BY ION-EXCHANGE RESIN .1. INTRINSIC RATE EXPRESSION IN LIQUID-PHASE ACTIVITIES

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. © 1990.