Green separation pathway for hydrocarbon compounds: Ionic liquid extraction technology

Abstract

In recent years, ionic liquids (ILs) have demonstrated various potential applications in separating hydrocarbon compounds due to their low volatility, high thermal stability, and excellent solubility properties. This work reviews the progress of research on ILs in separating aromatics, polycyclic aromatic hydrocarbons (PAHs), heterocyclic aromatic compounds, and olefin-alkanes. ILs demonstrate unique separation mechanisms and excellent performance for the various separation objects by modulating their cationic and anionic structures based on the combined application of π-π interactions, electrostatic interactions, and hydrogen bonding networks. Functionalized imidazole-based ILs significantly improve the selectivity and efficiency through synergistic interaction with the target compounds for separating aromatic hydrocarbons. Due to their enhanced complexation, metal-based ILs have become a critical technology in extracting polycyclic aromatic hydrocarbons. Regarding separating heterocyclic compounds, introducing fluorine-containing anions and metal complexes improves the separation ability of nitrogen compounds and sulfides. The combination of hybrid ILs, supercritical extraction, and other innovative technologies has further expanded the application scope of ILs. Moreover, introducing thermodynamic models provides more accurate predictions of the separation behavior of ILs. Briefly, this review provides a perspective on ILs and their application in the separation and purification of hydrocarbon compounds. Therefore, the realization of effective separation of specific classes or specific substances from hydrocarbon mixtures to obtain high-purity target products is far-reaching for petrochemical, energy, environmental protection, and other fields.