Exceptional functionalized dual-acidic ionic liquid: High-efficiency catalytic reaction medium for oxidation desulfurization

Abstract

The development of highly active functionalized ionic liquids (ILs) as both extractants and catalysts for use in achieving deep desulfurization continues to pose challenges. In this study, a highly efficient oxidative desulfurization system was constructed, composed of dual-acidic ionic liquids (DILs) and H₂O₂-AcOH. The investigation results of four DILs prepared from different metal chlorides ([HSO₃C₃NEt₃]Cl-MnCl_n, MnCl_n = AlCl₃, ZnCl₂, CuCl₂, FeCl₃) in oxidative desulfurization showed that [HSO₃C₃NEt₃]Cl–AlCl₃ had an outstanding catalytic effect and significantly promoted the oxidation of sulfides. With a 0.2 g [HSO₃C₃NEt₃]Cl–AlCl₃, the removal rate of dibenzothiophene (DBT) reached 100% in 10 mL model oil under mild conditions at 55 °C for 20 min. The key is its ability to induce the dismutation of superoxide anions (•O₂⁻), which facilitates the generation of singlet oxygen (¹O₂). The efficient oxidation of DBT is accomplished through a predominantly ¹O₂-mediated non-radical mechanism. [HSO₃C₃NEt₃]Cl-AlCl₃ serves as a favorable medium for contact to be made between ¹O₂ and sulfides, which indicates an efficient catalytic-adsorption synergy.