Reactive Distillation for Two-Stage Reaction Systems: Adipic Acid and Glutaric Acid Esterifications

Two new complete reactive distillation processes for two-stage reaction systems (adipic acid and glutaric acid esterifications with methanol) are explored. Similarities and differences between these two flowsheets have been identified. Both the diacid esterification reactions are catalyzed heterogeneously by an acidic ion-exchange resin, and reaction kinetics can be described using quasihomogeneous model. The UNIFAC method predicts suitable NRTL parameters for calculating liquid activity coefficients, which give a good description of experimental data. Results show that the plantwide flowsheets need a large recycle ratio for the light key reactants and ester products could be achieved with a purity of 99 mol %. A systematic design procedure for the complete flowsheets is presented, and the optimum operating conditions of the overall systems are studied to minimize the total annual cost while meeting the product specifications.