Multiscale modeling for separating methylnaphthalene from light cycle oil via benzyl alcohol-based deep eutectic solvent

Novel benzyl alcohol-based DESs enable efficient methylnaphthalene separation from LCO. • Multi-stage extraction outperforms high solvent ratio for achieving high removal rates. • Synergistic O-H…π, Cl − /Br − …π, C-H…π interactions underpin the high extraction selectivity. In this study, novel benzyl alcohol (BnOH)-based deep eutectic solvents (DESs) were designed and, for the first time, applied to extract 1-methylnaphthalene from n-dodecane as a light cycle oil (LCO) model system. Liquid-liquid extraction experiments, optimization of operating parameters, quantum-chemical calculations, and molecular dynamics simulations were systematically conducted to evaluate the separation performance and elucidate the underlying mechanism. The results show that TEMAC/BnOH (1:3) exhibited the highest extraction efficiency among the investigated DESs, with a single-stage extraction efficiency exceeding 60% and a cumulative 1-methylnaphthalene removal efficiency of over 90% after four stages of extraction. Increasing the extraction stages is more effective than merely increasing the solvent-to-feed mass ratio. The separation mechanism demonstrates that the high selectivity originates from three synergistic interactions, including the O-H…πbond between the hydroxyl group in BnOH and the aromatic ring, the Cl − /Br − …π interaction, and the methyl-induced C-H…π interaction in the quaternary ammonium salt.