Deciphering the intermolecular interactions for separating bicyclic and tricyclic aromatics via different naphthalene-based solvents

The traditional separation of bicyclic and tricyclic aromatics from coal tar involves complicated multi-steps and consumes significantly more energy. Previous work accomplished the separation between anthracene-phenanthrene isomers using electrostatic interaction, but for the separation between bicyclic and tricyclic aromatics, electrostatic interactions are difficult to produce a recognizable effect. Naphthalene-based solvents, named as naphthaleneacetamide, naphthaleneethanol, naphthalenemethanol, naphthol, naphthylacetic acid, naphthylacetonitrile, and naphthylamine, respectively, were used for the efficient separation of naphthalene and phenanthrene via dispersion interaction. Results showed that the pre-studied structural parameters are the key factors in selecting an efficient solvent. And the substituents on the intermolecular interactions involved in the separation processes had an important impact, which were evaluated. Naphthalenemethanol exhibited a superior performance with a purity of 96.3 wt % naphthalene products because its electron-donating substituent enables the selective recognition of naphthalene via the dispersion interaction. The used naphthalene-based solvents can be regenerated and recycled via back extraction with a purity of over 90 wt % naphthalene products, suggesting solvent structural stability during the regeneration processes. Notably, the naphthalene-based solvents also demonstrated better separation performance for polycyclic aromatics from coal tar with a purity of over 80 wt % for bicyclic aromatics. This study would enhance the utilization of coal tar as a valuable source of polycyclic aromatics besides broadening the knowledge for applying non-bonded interaction in the separation of polycyclic aromatics technologies.