The separation of the iso-propanol (IPA)-water azeotrope is a significant challenge in the chemical and biomedical industries, primarily due to strong hydrogen bonding interactions that hinder conventional distillation. Although extractive distillation offers a viable solution, conventional entrainers suffer from limitations such as corrosion, volatility, and environmental issues. Ionic liquids (ILs) have emerged as promising green alternatives owing to their negligible vapor pressure, high thermal stability, and tunable properties. In this study, three acetate-based ammonium ILs─N1111Ac, N2111Ac, and N4111Ac─were systematically screened using the COSMO-RS model. Isobaric vapor–liquid equilibrium (VLE) experiments were performed, and the thermodynamic consistency of the data was rigorously validated. The NRTL model correlated well with the experimental VLE results. Quantum chemical calculations further revealed that the ILs break the azeotrope by restructuring the molecular interaction network, a process driven by enhanced hydrogen bonding. Process simulation confirmed the industrial feasibility of using N1111Ac as an entrainer, which exhibited the highest separation efficiency, requiring only an IL molar fraction of 0.0385 to eliminate the azeotrope. Optimized process conditions showed that using N1111Ac led to a 20.09% reduction in the total annual cost and a 26.05% decrease in gas emissions (CO2, SO2, and NOx) compared to conventional organic solvent DMSO, aligning with the principles of green chemistry. Both experimental and computational results confirm that these ILs are efficient and environmentally benign entrainers for IPA-water separation. The integrated methodology established in this work provides a robust framework for designing sustainable separation processes.
Zhang et al. (Fri,) studied this question.
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