Lewis ionic liquid-loaded Fe3O4@SiO2 magnetic catalytic microspheres coupled with persulfate for catalytic oxidative desulfurization

Abstract

Lewis acidic ionic liquid-loaded Fe₃O₄@SiO₂ magnetic catalytic microspheres were prepared. When coupled with persulfate, the microspheres catalytically oxidized and removed dibenzothiophene (DBT) from octane. The microspheres used for catalytic desulfurization were characterized and analyzed by SEM, TEM, FT-IR, VSM, and TG-DTA. The results indicated that the prepared catalytic desulfurization microspheres had a uniform particle size distribution, an overall diameter of 200 nm, and a core diameter of Fe₃O₄ of about 180 nm. The saturation magnetization of the catalytic desulfurization microspheres was 39.8 emug⁻¹, which allowed them to be rapidly magnetically separated. The optimal experimental conditions were 1.5 g catalyst, 1.2 g PMS (20%) oxidant, 30 °C, an initial sulfur content of 500 ppm, 6.0 g octane, and 3.0 g acetonitrile. Under these conditions, the desulfurization rate reached 98.5% after 25 min, which decreased by about 10% after five recycles. GC-MS analysis indicated the oxidation product was dibenzothiophene sulfone (DBTO₂). In the desulfurization mechanism, DBT was first extracted by acetonitrile. Then, in the acetonitrile phase, Co²⁺ catalyzed hydrogen persulfate to form active oxygen atoms that oxidized DBT and eventually formed DBTO₂.