Highly selective extraction of aromatics from aliphatics by using metal chloride-based ionic liquids

Abstract

The separation of aromatics from aliphatics is essential for achieving maximum exploitation of oil resources in the petrochemical industry. In this study, a series of metal chloride-based ionic liquids were prepared and their performances in the separation of 1,2,3,4-tetrahydronaphthalene (tetralin)/dodecane and tetralin/decalin systems were studied. Among these ionic liquids, 1-ethyl-3-methylimidazolium tetrachloroferrate ([EMIM][FeCl4]) with the highest selectivity was used as the extractant. Density functional theory calculations showed that [EMIM][FeCl4] interacted more strongly with tetralin than with dodecane and decalin. Energy decomposition analysis of [EMIM][FeCl4]–tetralin indicated that electrostatics and dispersion played essential roles, and induction cannot be neglected. The van der Waals forces was a main effect in [EMIM][FeCl4]–tetralin by independent gradient model analysis. The tetralin distribution coefficient and selectivity were 0.8 and 110, respectively, with 10% (mol) tetralin in the initial tetralin/dodecane system, and 0.67 and 19.5, respectively, with 10% (mol) tetralin in the initial tetralin/decalin system. The selectivity increased with decreasing alkyl chain length of the extractant. The influence of the extraction temperature, extractant dosage, and initial concentrations of the system components on the separation performance were studied. Recycling experiments showed that the regenerated [EMIM][FeCl4] could be used repeatedly.