Reactive-extractive distillation processes design for aqueous ternary azeotrope separation

Abstract

In the production of ethyl tert-butyl ether using ethanol and tert-butyl alcohol, aqueous ternary azeotrope is generated, and efficient separation methods are crucial for resource recycling and environmental protection. This study proposes an innovative reactive-extractive distillation process, in which ethylene oxide hydration reaction is introduced to consume water and produce ethylene glycol as an extractant to enhance the relative volatility between ethanol and tert-butyl alcohol, thereby facilitating efficient separation of the azeotropic system. The accuracy of the UNIQUAC thermodynamic model was verified and subsequently utilized to evaluate the feasibility of the reactive-extractive distillation coupled process through ternary phase diagrams with residual curves. A genetic algorithm was employed to optimize the process by minimizing the total annual cost, and the overall performance was evaluated through economic, environmental, and exergy analyses. Two thermally integrated processes with preheat and intermediate heat exchange were designed based on the advanced exergy analysis. Results show that the intermediate heat exchange intensified reactive-extractive distillation process achieves significant improvements over the traditional three-column extractive distillation, including reductions of 76.74% in total annual costs, 72.43% in CO₂ emissions, and 29.23% in exergy destruction, thereby offering practical solutions for process intensification and industrial application.