Influences of Pressure on the Operation of Reactive Distillation Columns Involving Kinetically Controlled Exothermic Reactions

Abstract

For the reactive distillation column involving a kinetically controlled exothermic reaction, operating pressure can present nonmonotonic influences on process dynamics and operation. While the enhancement of operating pressure benefits process dynamics and controllability in the lower part of its feasible region (which is confined by the temperature levels of the available cold and hot utilities), it turns to deteriorate process dynamics and controllability in the higher part of its feasible region. Three reactive distillation systems, including an ideal reactive distillation column performing a hypothetical exothermic reaction, A + B ⇀↽kbkf C + D, and two real ones producing, respectively, methyl acetate from acetic acid and methanol and methyl tertiary butyl ether (MTBE) from isobutylene and methanol, are thoroughly studied in this work, and the results confirm the existence of this unique phenomenon. The intricate behavior of such kind of reactive distillation columns is essentially governed by the conflicting effects of operating pressure on reaction rate and chemical equilibrium constant and determines actually a favorable region of operating pressure for process dynamics and operation. Because the region may or may not coincide with the one in terms of process synthesis and design, operating pressure can therefore serve as an important decision variable to trade-off process design and operation, rendering the resultant process design with balanced steady-state performance and process dynamics and controllability.