Catalytic oxidative desulfurization with a hexatungstate/aqueous H2O2/ionic liquid emulsion system

Three hexatungstates ([(C4H9)3NCH3]2W6O19, [(C8H17)3NCH3]2W6O19, [(C12H25)3NCH3]2W6O19) have been synthesized and characterized. The hexatungstates were dissolved in the hydrophobic 1-octyl-3-methylimidazolium hexafluorophosphoric ([Omim]PF6) ionic liquid (IL) forming a water-in-IL emulsion system with aqueous hydrogen peroxide. Catalytic oxidation of sulfur-containing model oil and real gasoline was studied under different conditions with this system. The multiphase reaction of the new IL emulsion system made for easy separation and exhibited good recycleability. As a stable macrocosm, the separated catalytic system could be directly added to fresh oil and H2O2 for the next run without any treatment and after recycling 15 times, the sulfur removal could still reach a high level without any decrease. The supposed mechanism is given to show the superiority of the new emulsion catalytic system.