Mechanism and optimization for oxidative desulfurization of fuels catalyzed by Fenton-like catalysts in hydrophobic ionic liquid

• Several Fenton-like catalysts were synthesized and characterized systematically.
• Deep desulfurization can be obtained in both hydrophilic IL and hydrophobic IL.
• The oxidative desulfurization mechanism was studied by ESR spin-traping technique.
• The oxidized products could be determined by GC–MS.

Various Fenton-like catalysts prepared by choline chloride (ChCl) and metal salts (FeCl3, ZnCl2, SnCl2) were characterized by FT-IR, UV–vis, Raman, ESI-MS and elemental analysis. High desulfurization efficiency of dibenzothiophene (DBT) could be obtained not only in hydrophilic ionic liquid (IL) [Bmim]BF4 (94.9%) but also in hydrophobic IL [Omim]BF4 (97.2%) by using ChFeCl4 as a catalyst under mild conditions. ESR measurements could give the evidence that the active oxygen species generated by ChFeCl4 and H2O2 in IL were involved in the catalytic oxidation of DBT. The influential factors, including reaction time, temperature, catalyst dosage, and O/S (H2O2/DBT) molar ratio, were investigated in detail to estimate the optimal conditions for the desulfurization system in [Omim]BF4. The aromatic sulfur compounds, DBT, benzothiophene (BT), and 4,6-dimethyldibenzothiophene (4,6-DMDBT), could be oxidized to the corresponding sulfones, which were detected by GC–MS. Moreover, the catalytic system containing IL and catalyst could be easily separated from oil and could be recycled at least five times without a significant decrease on removal of DBT.

Dibenzothiophene (DBT) in model oil was first extracted into IL phase and oxidized to the corresponding sulfone by O2−, which was generated by ChFeCl4 upon interaction with H2O2 in IL.Figure optionsDownload high-quality image (155 K)Download as PowerPoint slide