A coupled catalyst composed of CoFe2O4 magnetic nanoparticle and [HMIM]Br-FeCl3 to intensify the oxidative desulfurization of FCC diesel

Abstract

Ionic liquids have been extensively studied as solvents or catalysts for oxidative desulfurization (ODS) of diesel fuel, but it is still a challenge to reduce the desulfurization time and steps. In this work, a new highly efficient desulfurization system composed of CoFe2O4 magnetic nanoparticle, [HMIM]Br-FeCl3 and H2O2 was developed for the ODS of FCC diesel fuel. The desulfurization performances were investigated including desulfurization time, temperature, volume ratio of IL/oil, O/S molar ratio, dosage of CoFe2O4, FeCl3 content in ILs, regeneration, and reuse of catalyst and solvent. Owing to the coupled catalytic roles of CoFe2O4 magnetic nanoparticle and [HMIM]Br-FeCl3, where Co2+ and Fe3+ interact with H2O2 to produce •OH radical that converts S-compounds into sulfone and sulfoxide compounds, such a desulfurization system is highly effective in removing S-compound in diesel fuel. The S-content in FCC diesel fuel was reduced from the original 272.8 ppm to 0.5 ppm with 99.82% S-removal efficiency after one step within 8 min under the optimal conditions of 25 °C, 8 min, V(IL/oil) = 1:10, O/S = 20, 5 wt% CoFe2O4 dosage and n([HMIM]Br)/n(FeCl3) = 1:1; the desulfurization performance is much better in desulfurization time and steps than other desulfurization systems reported previously. The desulfurization system can be regenerated and reused without remarkable loss of desulfurization activity. A desulfurization mechanism was proposed.

Keywords

• CoFe2O4 magnetic nanoparticle
• Ferric chloride ionic liquids
• Oxidative desulfurization