Sustainable Separation of Azeotrope <i>n</i> -Hexane/Isopropanol via Extractive Distillation: Molecular Insights, Process Optimization, and Techno-Economic–Environmental Analysis for Cleaner Production

Separation of the azeotrope n-hexane (HEX)/isopropanol (IPA) is critical for solvent recovery in electronic and pharmaceutical industries, yet conventional distillation faces challenges of energy inefficiency and high carbon footprint. This study proposes an energy-efficient extractive distillation (ED) strategy using N-methyl pyrrolidone (NMP) as an entrainer to separate HEX and IPA with a high solvent recyclability and low environmental impact. Three processes, including conventional extractive distillation (CED), dividing wall column, and vapor-phase side-stream extractive distillation (VSED), were proposed and optimized via NSGA-II and TOPSIS algorithms. The results demonstrate that the VSED process achieves the optimal performance, reducing the total annual cost by 13.62% and CO2 emissions by 6.35% compared to the CED process. This study provides a comprehensive decision-making framework with the integration of molecular interactions, MD-assisted ED optimization, and process intensification supported by NSGA-II for sustainable separation of the HEX/IPA azeotrope.