Sensitivity of Thermodynamic Model Parameter to the Design of Heterogeneous Reactive Distillation: Amyl Acetate Esterification

Reactive distillation offers an attractive alternative for process intensification, especially for reaction/separation systems. In this work, we continue the effort to explore a specific class of reactive distillations: heterogeneous reactive distillation (or three-phase reactive distillation). By heterogeneous reactive distillation, we mean two-liquid phase exists in the reflux drum and a decanter is employed to separate the aqueous product from the organic reflux. For esterification reactions, propyl acetate, butyl acetate, butyl propionate and amyl acetate are good examples of this type of reactive distillation, because they all share the following characteristics: (1) a large two-liquid zone exists, (2) the minimum boiling azeotrope is located in the two-liquid zone, and (3) all tie lines slop in the direction of high purity product (typically water). Since phase-split description and location of all minimum boiling azeotropes are crucial for correct process description, the selection of thermodynamic models and corresponding binary parameters become important Unlike typical vapor-liquid equilibria (VLE) systems, the model should be able to describe VLLE (vapor-liquid-liquid equilibria) behavior as well as to locate all minimum boiling azeotropes. In an amyl acetate case study, the results clearly indicate that erroneous process designs may result if the thermodynamic model fails to capture the azeotropes or to locate reasonable two-liquid zone.