Design Alternatives for the Amyl Acetate Process: Coupled Reactor/Column and Reactive Distillation

Recent advances in reactive distillation have led to renewed interest in the design/redesign of many esterification processes. For the esterification of amyl acetate, design alternatives exist that offer a gradual transition from the conventional recycle structure to reactive distillation. The phase behavior of the quaternary mixture immediately excludes the possibility of the conventional recycle structure, and in this work, we explore the designs of two different configurations, a coupled reactor/column and reactive distillation column, for the amyl acetate process. The total annual cost (TAC) is used to evaluate the economic advantages of different designs. Systematic design procedures were devised for the coupled reactor/column system, as well as for the reactive distillation process. The results clearly indicate the economic advantage of reactive distillation for the amyl acetate process. Unique characteristics of amyl acetate process include a significant two-liquid zone and high-purity water from the aqueous phase of a decanter. This leads us to a single-end-composition control problem. However, limit cycles can occur if the net reaction rate and production rate are not properly balanced or if the feeds are not stoichiometrically balanced. Therefore, a second composition loop is used to infer possible imbalances. Dynamic simulations indicate that reasonable control can be achieved for very complex reactive distillation dynamics.