Separation of Dimethyl Ether from Chloromethane Gas Using Ionic Liquids: Molecular Insights and Process Simulation

The technology for capturing dimethyl ether (DME) from chloromethane (CH 3 Cl) gas using ionic liquids (ILs) as absorbents has been proposed and scaled up from the molecular level to the industrial scale. Based on the Conductor Screening Model for Real Solvents (COSMO-RS) model, the solubility of CH 3 Cl and DME in different ILs and the separation selectivity of CH 3 Cl to DME were calculated, and the viscosity of 156 potential IL candidates containing 13 cations and 12 anions was predicted. Based on the requirements of low viscosity, large free volume, and high solubility of DME for the corresponding target IL, 1-Ethyl-3-methylimidazolium tetrafluoroborate ([EMIM][BF 4 ]) was selected as a suitable absorbent. Using COSMO-RS model analysis (σ-Profile and ILs free volume) and quantum chemical (QC) (binding energy, decomposition energy, electrostatic potential ESP, independent gradient model IGM, and Atoms in molecules AIM), the microscopic atomic and molecular mechanisms of the separation mechanism are revealed in depth. In addition, the Conductor Screening Model for Segment Activity Coefficient (COSMO-SAC) model parameters were used to construct a rigorous equilibrium-stage model for process simulation, and the process design and optimization of the CH 3 Cl dehydration and DME capture process were carried out. The results show that [EMIM][BF 4 ] is a promising absorbent with good ability for CH 3 Cl drying and DME capture. The technology of DME capture in CH 3 Cl has broad industrial application potential.