Extraction-oxidation desulfurization by pyridinium-based task-specific ionic liquids

► The extraction-oxidation desulfurization system by TSIL [CH2COOHPy][HSO4] without adding additional catalyst. ► The TSIL which was halogen-free and had high catalytic oxidative activity was synthesized and used as both extractant and catalyst. ► The TSIL showed the good recycling performance.