Solute structure effect on aromatics-alkanes extractive separation toward rational LCO upgrading

Unravelling solute effect on extractive separation of aromatics and alkanes is highly required toward its rational incorporation into economical upgrading of light cycle oil (LCO). This work systematically examines the effect of aromatic and alkane structures on extraction performance from experimental and theoretical perspectives. Liquid-liquid extraction experiments demonstrate that the distribution coefficient and extraction efficiency strongly depend on the aromatic structure, whereas the selectivity and theoretical purity of aromatics significantly rely on the alkane structure. The extraction mechanism is elucidated from interaction strength and interfacial thickness analysis using molecular dynamics simulation. The diaromatics of 1-methylnaphthalene has stronger affinity to deep eutectic solvent (DES) than the monoaromatics of tetralin, while longer alkyl-chain in hexadecane enhances its repulsive interaction with DES than dodecane. Extraction process simulation was then carried out with well-regressed parameters of NRTL thermodynamic model. Process simulation confirms that a high extraction performance can be achieved for model LCO containing more diaromatics. Therefore, it is preferable to incorporate aromatics-alkanes extractive separation into the pre-hydrotreating step of LCO upgrading process.