Experimental investigation and mechanism analysis for the separation of ethyl formate‐ethanol Azeotropic system via liquid–liquid extraction with ionic liquids

Abstract BACKGROUND Ethyl formate (EF) and Ethanol (EtOH) are essential chemical feedstocks with extensive applications in industrial production, pharmaceuticals, and other critical fields. During production, the formation of an azeotropic mixture of EF and EtOH is inevitable, which is challenging to separate via conventional distillation. Effective separation of EF‐EtOH azeotropic systems is crucial for product purity and recovery efficiency. Liquid–liquid extraction can do this effectively. RESULTS In this work, the COSMO‐RS software was employed to screen ionic liquids (ILs) for separating the EF‐EtOH azeotrope. Liquid–liquid equilibrium (LLE) data for the EF‐EtOH‐ILs ternary system were measured at temperatures of 298.15 K and 303.15 K under atmospheric pressure. The data are correlated by the non‐random two‐liquids (NRTL) model and the consistency of NRTL model parameters was corroborated through topological analysis associated with the Gibbs tangent principle through Matlab software. The separation mechanism of ILs at the molecular level was investigated through interaction energy analysis, electrostatic potential analysis, and IGMH/QTAIM topological analysis. The process simulation was conducted using Aspen Plus V15. CONCLUSION LLE data showed the extraction performance follows the order: [EMIM][H 2 PO 4 ] > [PMIM][H 2 PO 4 ] > [BMIM][H 2 PO 4 ]. The average selectivity of ILs at 298.15 K is higher than those at 303.15 K. The quantum chemical calculation results demonstrated that ILs exhibit stronger interactions with EtOH than with EF and enabling effective extract EtOH from the azeotropic system. The simulation results show that the purity of EF could reach 99.94 wt%. The recovery rate of IL could reach 99.9 wt%. © 2026 Society of Chemical Industry (SCI).