A simplified extraction and catalytic oxidative desulfurization (ECODS) system composed of phosphotungstic acid (H3PW12O40 center dot 14H(2)O), 30% H2O2, and [bmim]BF4 was found suitable for the deep removal of sulfur in model oil. By this desulfurization system dibenzothiophene (DBT), 4,6-dimethyldibenzothiophene (4,6-DMDBT), and benzothiophene (BT) could be effectively removed. Removal of DBT could reach 98.2% at room temperature (30 degrees C) for 1 h, which was remarkably superior to mere solvent extraction with IL (14.2%) or catalytic oxidation without IL (15.9%). When the reaction temperature increased to 70 degrees C, treatment of BT, DBT, and 4,6-DMDBT with our ECODS system showed 100% removal of sulfur compounds in 3 h. This desulfurization system could be recycled five times with slight decrease in activity.