Ionic liquid extraction and catalytic oxidative desulfurization of fuels using dialkylpiperidinium tetrachloroferrates catalysts

A new family of dialkylpiperidinium tetrachloroferrate catalysts, such as [C 2 OHmpip]FeCl 4 , [C 4 mpip]FeCl 4 , [C 8 mpip]FeCl 4 , and [C 12 mpip]FeCl 4 , were synthesized and characterized by FT-IR, Raman, and ESI-MS. Their catalytic activities for oxidation of dibenzothiophene (DBT) in extraction and catalytic oxidative desulfurization system (ECODS) were evaluated using different ionic liquids. Results indicated that the 97.1% removal of DBT was obtained with [C 4 mpip]FeCl 4 as catalyst in ionic liquid [C 8 mim]BF 4 at 30   °C in 60   min. The optimal H 2 O 2 /sulfur molar ratio was only 3.5:1, which suggested that the catalyst was one of the most efficient catalysts reported so far. UV–Vis spectra provided an evidence that the lower desulfurization reactivity in PF 6 − -containing ionic liquids was attributed to the strong interaction between ionic liquid and DBT. Through the gas chromatography–mass spectrometer (GC–MS) analysis, dibenzothiophene sulfone was proved to be the only product of oxidation of DBT. Furthermore, the process of ECODS system was confirmed by GC–MS.