Scalable and Green Engineering of MoOx with Abundant Oxygen Vacancies for Efficient and Recyclable Aerobic Oxidative Desulfurization of Fuels

Efficient oxidation of refractory sulfides, such as dibenzothiophene (DBT) and its derivatives, provides a promising strategy to produce fuel oils with ultra-low sulfur content, or even completely sulfur-free. In this study, a series of non-stoichiometric molybdenum oxides (MoOx) were synthesized via a facile procedure and employed as efficient catalysts. These catalysts can effectively oxidize DBT and its derivatives into insoluble sulfones, which subsequently precipitate from the oil phase, achieving efficient sulfur removal. In this system, molecular oxygen from air can be activated by the MoOx catalysts with oxygen vacancies into superoxide radicals, which act as active oxygen species to efficiently oxidize refractory sulfides. Under atmospheric pressure at 120 °C, complete sulfur removal (100%) was achieved for both DBT and its derivatives, representing significantly milder conditions compared to conventional hydrodesulfurization. The aerobic oxidation system could be reused for up to 12 consecutive cycles without any significant decline in sulfur removal. And complete desulfurization (100%) was regained after a simple washing of the separated solid phase. Then, a possible reaction procedure was subsequently proposed to describe the desulfurization route. The remarkable catalytic performance, together with the facile synthesis strategy, indicates the potential of this approach for constructing other transition metal oxides used in various advanced aerobic oxidation reactions.