Hybrid separation processes—Combination of reactive distillation with membrane separation

In this paper, the modelling, simulation and process analysis for a hybrid separation process, the combination of reactive distillation with membrane separation, is presented. The application is illustrated by the heterogeneously catalysed n-propyl propionate synthesis from 1-propanol and propionic acid. The membrane module is located in the distillate stream of the reactive distillation column in order to selectively remove the produced water without use of entrainers. Key aspects for the theoretical description of reactive distillation processes are discussed. For the stand-alone reactive separation process, the simulation results with a non-equilibrium model are in good agreement with experimental data obtained in a pilot-scale column. Additionally, a comparison of the most common modelling depths, namely the non-equilibrium model with Maxwell–Stefan equations, the equilibrium model taking into account reaction kinetics and the equilibrium model assuming chemical equilibrium, is presented. Vapour permeation experiments using Sulzer Pervap™ 2201(D) have been performed in a pilot-scale membrane plant in order to determine the separation characteristics for the dewatering of the non-ideal binary 1-propanol–water mixture. A first process analysis of the combined unit operations shows the influence of structural and operational parameters on the performance of the feasible hybrid process.