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Keywords:

  • desulfurization;
  • ionic liquids;
  • oxidation;
  • peroxides;
  • sulfur heterocycles

Abstract

Oxidation of the sulfur-containing compounds benzothiophene (BT), dibenzothiophene (DBT), and 4,6-dimethyldibenzothiophene (4,6-DMDBT) has been studied in a desulfurization system composed of model oil, hydrogen peroxide, and different types of ionic liquids [(C8H17)3CH3N]Cl/FeCl3, [(C8H17)3CH3N]Cl/CuCl2, [(C8H17)3CH3N]Cl/ZnCl2, [(C8H17)3CH3N]Cl/SnCl2, [(C4H9)3CH3N]Cl/FeCl3, [C10H21(CH3)3N]Cl/FeCl3, [(C10H21)2(CH3)2N]Cl/FeCl3. Deep desulfurization is achieved in the Fenton-like ionic liquid [(C8H17)3CH3N]Cl/FeCl3 at 25 °C for 1 h. The desulfurization of DBT reaches 97.9 %, in consuming very low amount of [(C8H17)3CH3N]Cl/FeCl3 (only 0.702 mmol). The reaction conditions, for example, the amount of [(C8H17)3CH3N]Cl/FeCl3 or H2O2, the temperature, and the molar ratio of FeCl3 to [(C8H17)3CH3N]Cl, are investigated for this system. The oxidation reactivity of the different sulfur-containing compounds is found to decrease in the order of DBT>BT>4,6-DMDBT. The desulfurization system can be recycled six times without significant decrease in activity. The sulfur level of FCC gasoline could be reduced from 360 ppm to 110 ppm.