Mechanism Analysis and Multiobjective Optimization of Efficient and Energy-Saving Separation of Green Fuel Additives via Extractive Pressure Swing Distillation with an Ionic Liquid Mixed Entrainer

A mixed system for separation of green fuel additives containing diethyloxymethane and ethanol by extractive pressure swing distillation for ionic liquids mixed with organic solvents as an entrainer was proposed for the first time. The interaction mechanism between entrainers and the azeotrope was deeply explored via quantum chemistry and molecular dynamics methods. The optimal ionic liquid entrainer was determined as 1-buty-3-methylimidazolium acetate, and the most suitable organic solvent as the entrainer was p-diethylbenzene. The separation process of the ethanol, diethyloxymethane, and toluene system was developed. The process operation parameters were optimized through a multiobjective optimization method. In order to improve the energy utilization and separation efficiency of the process, a heat pump-assisted extractive pressure swing distillation process was proposed. Compared with the mixed entrainer extractive distillation process, the heat pump-assisted extractive pressure swing distillation process reduced TAC by 1.2% and gas emissions by 17.5%, demonstrating economic advantages and environmental protection effects. This work demonstrates the application of ionic liquid mixed solvents in systems containing green fuel additives, providing guidance for the screening and application of ionic liquid as an entrainer.