Deep Desulfurization of 4,6-Dimethyldienzothiophene by an Ionic Liquids Extraction Coupled with Catalytic Oxidation with a Molybdic Compound

A series of the imidazolium-based phosphoric ionic liquids, N-methyl-N-methylimidazolium dimethyl phosphate ([Mmim]DMP), N-ethyl-N-methylimidazolium diethyl phosphate ([Emim]DEP), and N-butyl-N-methylimidazolium dibutyl phosphate ([Bmim]DBP), were synthesized and employed in the extraction and catalytic oxidation desulfurization system (ECODS) for the removal of 4,6-dimethyldienzothiophene (4,6-DMDBT) from a model oil, with hexaammonium heptamolybdate tetrahydrate ((NH4)(6)Mo7O24 center dot 4H(2)O) as catalyst and 30 wt % hydrogen peroxide (H2O2) solution as oxidant. The effects of the type of ionic liquid, amount of catalyst and H2O2, ILs/oil mass ratio, reaction time, reaction temperature, and regeneration of ionic liquid on the 4,6-DMDBT removal of a model oil were investigated in detail. The results indicate that a sulfur system containing H2O2, (NH4)(6)Mo7O24 center dot 4H(2)O), and [Bmim]DBP, exhibited such a high catalytic activity that the removal of 4,6-DMDBT could reach 89.2% at 50 degrees C in 3 h, which was markedly superior to mere solvent extraction with IL (9.29%) or catalytic oxidation without IL (5.34%). The desulfurization system for a model oil could be recycled six times with an unnoticeable decrease in activity. Meanwhile, ((NH4)(6)Mo7O24 center dot 4H(2)O) not only possessed good catalytic activity but hardly contaminated the oil. This work shows that ECODS containing (NH4)(6)Mo7O24 center dot 4H(2)O), [Bmim]DBP, and H2O2 may be a new option for producing cleaning fuel.