Research strategy for the separation of toluene/methylcyclohexane azeotropes by ionic liquids

The separation of toluene (TOL) and methylcyclohexane (MCH) is a key step to achieve high‐purity aromatic recovery, but traditional distillation processes consume significant energy. In this study, an ionic liquids (ILs)‐based extractive distillation strategy was proposed to achieve efficient separation by computational screening, experimental validation, and process simulation. First, 1722 candidate ILs were systematically screened using the COSMO‐RS model, selecting three high‐performance ILs based on selectivity and viscosity criteria. Experimentally determined vapor–liquid equilibrium data showed that 1,3‐dimethylimidazolium bis(fluorosulfonyl)imide salt ([MMIM][FSI]) significantly enhanced the relative volatility of TOL‐to‐MCH. Quantum chemical analyses revealed the separation mechanism. Based on this, an extractive distillation process was constructed by Aspen Plus process simulation: the use of [MMIM][FSI] as an entraining agent reduced the total annualized cost (TAC) by 55.55% compared with conventional distillation. This study provides an industrially feasible solution for low‐carbon separation of aromatic/non‐aromatic systems through an innovative pathway of molecular design–experimental validation–process integration.