Light irradiation induced aerobic oxidative deep-desulfurization of fuel in ionic liquid

Abstract

An aerobic oxidative deep-desulfurization process for aromatic sulfides, such as dibenzothiophene (DBT), benzothiophene (BT), 4,6-dimethyldibenzothiophene (4,6-DMDBT), was carried out via ionic liquids (ILs) extractive coupled with photochemical oxidation. In this process, sulfur compounds in n-octane were firstly extracted into the IL phase and then oxidized to corresponding sulfones. The sulfur removal efficiency of DBT with air as the oxidizing agent could reach up to 99.1% under mild conditions. Then, a possible reaction mechanism of this metal-free photochemical oxidative desulfurization system was proposed. The sulfur removal efficiency decreased slightly, even though the original S-concentration of DBT increased from 500 to 1000 ppm. The oxidation reactivity of different sulfur compounds decreased in the order of: DBT > 4,6-DMDBT > BT. The influences of alkene and aromatic addition were also investigated. Gas Chromatograph-Mass Spectrometer (GC-MS) measurements demonstrated that the sulfur compounds were converted to their corresponding sulfones and separated out of the oil phase. Under optimal conditions, the IL could be recycled at least 5 times without a remarkable decrease in activity.