Abstract This study developed an efficient method for separating C9 aromatics, valuable by‐products in petrochemical processes. Using the COSMO‐SAC model, a suitable ionic liquid (IL) was selected as the extractant. Extraction experiments at varying concentrations and solvent ratios confirmed its high separation performance. Multi‐stage extraction and IL regeneration experiments verified the feasibility of the selected IL in industrial applications. To explore the influence of different components on C9 aromatics, experiments with different solutes, solvents, and IL extractants were carried out. Molecular dynamics and quantum chemical simulations elucidated the extraction mechanism at the molecular level. At the system engineering scale, based on the liquid–liquid equilibrium data, the C9 aromatics separation process was conceptually designed and optimized. The new method can produce high‐purity fuel oil with C9 aromatics of less than 0.7% by weight, thereby reducing the overall heat duty of the process.
Wang et al. (2026) studied this question.