Computer-Aided Screening of Ionic Liquids as Entrainers for Separating Methyl Acetate and Methanol via Extractive Distillation

In the production of poly(vinyl alcohol), the raw materials methyl acetate (MeOAc) and methanol (MeOH) exist as a homogeneous azeotropic mixture. Twenty-five kinds of ionic liquids, composed of five types of cations and five types of anions, were studied using the COSMO-SAC method. The sigma-profile data for each component and the selectivity at infinite dilution (S-infinity) were calculated and analyzed, respectively. 1-Hexyl-3-methylimidazolium chloride ([HMIM][Cl]) and 1-butyl-3-methylimidazolium chloride ([BMIM][Cl]) were selected as suitable entrainers based on the COSMO-SAC method. The binary interaction parameters of the NRTL model of the MeOH/ionic liquid and MeOAc/ionic liquid systems were regressed. The conceptual design for the separation of MeOAc and MeOH using ionic liquids as entrainers was investigated. The comparison of two processes using two entrainers was carried out from an economic perspective. The total annual cost (TAC) of the process using [HMIM][Cl] as an entrainer can be reduced by 16.5% compared with that of the process using [BMINI][Cl]. The results indicated that the COSMO-SAC method is feasible for screening ionic liquids as optimal entrainers. This work could provide theoretical instruction for further industrial applications using ionic liquids as solvents via COSMO-SAC computer-aided screening.