In-situ fabrication of MoO2/MoxC heterojunction on rodlike carbon-coated zirconia for enhanced oxidative desulfurization of fuel oils

Abstract

Electronic structure of catalysts is of great importance in redox reactions. Virtually, fabricating Mo-based heterojunction nanocomposites and elucidating their role in the nature of synergic effect between Mo compounds hold the key to promoting the electron transfer and eventually improving oxidative desulfurization (ODS) performances. Herein, the molybdenum dioxide/molybdenum carbides (MoO2/MoxC) heterojunction was in situ dispersedly immobilized on a rodlike N-doped carbon (NC)-coated zirconia (ZrO2) via a facile annealing route employing phosphomolybdic acid (PMo12)-loaded Zr(IV) porphyrinic metal–organic framework (MOF-545) (i.e. PMo12@MOF-545) as a precursor. The optimized catalyst (MoO2/MoxC@NC@ZrO2) exhibits outstanding oxidative desulfurization (ODS) activities for fuel oil with sulfur content in a wide range of 200～4000 ppm. It is indicated that the extraordinary ODS activity of MoO2/MoxC@NC@ZrO2 significantly stems from the accelerated electron transfer by the MoO2/MoxC heterojunction, the strong electron-donating effect of NC layer, and abundant active sites from the extremely dispersed Mo compounds realized by both NC and ZrO2. The ODS reaction is elucidated by the •OH radical mechanism. Moreover, MoO2/MoxC@NC@ZrO2 shows excellent stability, and the sulfur removal could remain over 96.5 % after thirteen cycles. This work not only opens up a new avenue for in situ integrating Mo-based heterojunctions, but also manifests a promising potential for practical ODS process.