SYNTHESIS OF ETBE - RESIDUE CURVE MAPS FOR THE HETEROGENEOUSLY CATALYZED REACTIVE DISTILLATION PROCESS

The liquid phase synthesis of octane-enhancing ethers is increasingly realized as a reactive distillation process, catalysed by ion exchange resins. To study the physical and chemical phenomena occurring in the se systems, the present paper considers a reactive batch distillation process in a heated still. Because of its increasing technical importa nce, the synthesis of ETBE (ethyl tertiary butyl ether) from ethanol a nd isobutene is investigated as an example. The developed model is bas ed on the phase equilibrium between the liquid and vapour phases and a n adequate kinetic formulation of the heterogeneously catalysed etheri fication by application of generalized Langmuir-Hinshelwood rate expre ssions. To describe the non-ideal mixture behaviour, the liquid phase activities are introduced. Simulation results show that the shape of t he residue curves depends on two essential parameters: the Damkohler n umber, Da, and the operating pressure, p. The values of these paramete rs influence the existence and the position of fixed points in the res idue curve map. Therefore an analysis is carried out to calculate the steady state solutions in the reactive mixture and to forecast the num ber of stable nodes with given Da and p. (C) 1997 Elsevier Science S.A .