Precise regulation of weak intermolecular interaction forces and their application to high-purity aromatic monomer separation from direct coal liquefaction oil

The separation of high-purity aromatic monomers from direct coal liquefaction (DCL) contributes to their value-added utilization. However, the complexity of its components often leads to additional reactions. To achieve efficient separation of monocyclic aromatics from DCL, this paper proposes a separation strategy of ‘fractionation − column chromatography − extractive distillation’ through precise regulation of weak intermolecular interaction forces. The results showed that monocyclic aromatics are enriched up to 19.12 wt% through fractionation, followed by the separation of mixed aromatics via atmospheric pressure column chromatography. Finally, o-xylene with a purity of 99.16 wt% was separated by extractive distillation using sulfolane as the solvent. The separation mechanisms are investigated through quantum chemical calculations and UV–vis analysis. Results indicated that the polarity difference was the driving force for separating mixed aromatics. The interaction between the solvent and the C8 aromatics in the extractive distillation was primarily governed by Van der Waals forces. The difference in interaction energy, ranging from 2.22 to 6.53 kJ/mol, serves as the driving force for the separation of o-xylene. The separation strategy proposed in this study provides a new perspective for the separation of high-purity aromatic monomers from DCL.