Phase Equilibrium of p-Xylene and Isobutanol in Ionic Liquid Separations: Thermodynamic and Mechanistic Analysis

With the continuous expansion of the global polyester industry chain, the market demand for p-xylene (PX) as an upstream raw material is becoming increasingly large. In response to the call for cleanliness, consumption reduction, emission reduction, and sustainable development, three kinds of imidazole ionic liquids (ILs) were used as extractants to efficiently clean and separate the isobutanol-PX azeotropic system for the first time in this work. The conductor-like screening model for realistic solvents (COSMO-RS) and σ-profile were used to select the best extraction agent, and then, target ILs were synthesized. Their extraction effects were analyzed through liquid–liquid phase equilibrium experiments, and the separation effect of bisulfate was the best. Furthermore, given the high cost of ILs, recycling extraction experiments were performed for the first time. Finally, this work combined molecular dynamics simulation with quantum chemistry calculation to reveal the extraction mechanism from the microscopic mechanism level, which provided theoretical support for the separation of the azeotropic system of alcohols and aromatics.