Commercially available molybdic compound-catalyzed ultra-deep desulfurization of fuels in ionic liquids

Abstract

A simple liquid–liquid extraction and catalytic oxidative desulfurization (ECODS) system composed of molybdic compound, 30% H2O2 and 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim]BF4) has been found suitable for the ultra-deep removal of dibenzothiophene (DBT) in model oil. The precatalyst of molybdic compound was oxidized with H2O2 to form peroxomolybdic compound, which was soluble in ionic liquid and dissolved in oil. The sulfur-containing compounds, such as benzothiophene (BT), DBT and 4,6-dimethyldibenzothiophene (4,6-DMDBT), in model oil were extracted into ionic liquid phase and oxidized to their corresponding sulfones by peroxomolybdic compound. In the case of the system containing model oil (DBT), H2O2, Na2MoO4·2H2O and [bmim]BF4, extraction and catalytic oxidation increased the sulfur removal to 99.0%, which was remarkably superior to mere solvent extraction with IL (13.6%) or catalytic oxidation without IL (4.1%). The desulfurization system could be recycled five times with very little decrease in activity.