Effective separation of ethanol–water azeotrope using acetate‐based ionic liquids: from COSMO ‐ RS screening to process simulation

Abstract BACKGROUND The separation of ethanol and water is challenged by the formation of a minimum‐boiling azeotrope, rendering conventional distillation ineffective. Extractive distillation using ionic liquids (ILs) offers a promising alternative due to their negligible volatility and structural tunability. However, the vast number of potential cation–anion combinations necessitates a rational strategy for IL selection. RESULTS Three acetate‐based ILs – [N1111][Ac], [MMIM][Ac], and [EMMIM][Ac] – were identified via the conductor‐like screening model for real solvents (COSMO‐RS) and experimentally validated to effectively break the ethanol‐water azeotrope with separation performance following [N1111][Ac] > [MMIM][Ac] > [EMMIM][Ac]. The NRTL (non‐random two‐liquid) model accurately correlated the vapor–liquid equilibrium data and quantum chemical analyses revealed that hydrogen bonding between the acetate anion and water is the primary interaction governing separation. Process simulation using [EMMIM][Ac] in a double‐column extractive distillation system achieved ethanol purity exceeding 99.9 wt%. CONCLUSION Acetate‐based ILs demonstrate high efficacy as entrainers for ethanol‐water extractive distillation. The integrated methodology combining COSMO‐RS, experimental validation and molecular‐level analysis provided a robust framework for IL selection. These findings offer valuable insights for designing sustainable separation processes in biofuel and chemical industries. © 2026 Society of Chemical Industry (SCI).