Amorphous MoOx loaded on N-doped carbon-modified SiO2 for strongly enhanced oxidative desulfurization activity

Transition-metal oxides (TMOs) are good catalyst candidates for oxidation desulfurization (ODS) reaction, and its excellent dispersion in carriers could exert great influence on its catalytic performance. However, improving its catalytic activity still remains challenging. Herein, the amorphous molybdenum oxide (MoOx) was synthesized as the active sites for ODS reaction. Via a facile adsorption-pyrolysis approach, the amorphous MoOx was dispersedly immobilized onto N-doped carbon layer (NC)-encapsulated SiO2 using zinc pyridine porphyrin (ZnTPyP) and phosphomolybdic acid (PMo12)-modified SiO2 nanocomposites as precursor, obtaining the MoOx@NC@SiO2 catalyst. Owing to the wonderful pre-dispersion of Mo sources on the precursor leaded by the electrostatic interaction and spacial effect, the confinement effect of the derived carbon matrix, and the strong Mo-N bonds, the growth of MoOx crystal could be inhibited in pyrolysis procedure, ensuring the amorphous structure and good dispersion of MoOx species on SiO2. The as-prepared MoOx@NC@SiO2 exhibits excellent oxidation desulfurization (ODS) performances, and could promote the complete oxidation of DBT in model fuel into DBTO2 at the theoretical O/S molar ratio of 2, due to the perfect activation of all oxygen atoms of H2O2 by the amorphous MoOx. In addition, a plausible ODS mechanism over MoOx@NC@SiO2 is depicted to be the •OH radicals. Moreover, MoOx@NC@SiO2 still displays an outstanding reusability over at least 10 cycles owing to the encapsulation of NC layers and the strong Mo-N bonds. Therefore, this work provides a promising catalyst for industrial ODS application, and opens up a new avenue for developing the amorphous TMOs catalysts.