Defective silicotungstic acid-loaded magnetic floral N-doped carbon microspheres for ultra-fast oxidative desulfurization of high sulfur liquid fuels.

Highly active Keggin-type silicotungstic acid (SiW 12 ) with oxygen vacancy (O v ) defects was encapsulated into the magnetic floral N-doped carbon microspheres (γ-Fe 2 O 3 @NC-300) through the facile one-step air pyrolysis of the precursor comprising core-shell Fe 3 O 4 @polydopamine (Fe 3 O 4 @PDA) and SiW 12 to prepare γ-Fe 2 O 3 @NC@SiW 12 -300. The fabricated catalysts were systematically characterized and subsequently employed for the oxidation desulfurization (ODS) of the model fuel. The magnetic floral γ-Fe 2 O 3 @NC@SiW 12 -300 catalyst exhibited nearly perfect catalytic activity, which under mild conditions could remove 100% amount of 4000 ppm DBT in model fuel within 20 min (0.03 g catalysts and n (H 2 O 2 )/ n (S) of 2). The catalyst activity is mainly attributed to the high activity SiW 12 with the O v defect and its outstanding dispersibility in γ-Fe 2 O 3 @NC, along with the high number of exposed active sites. A selected catalyst, γ-Fe 2 O 3 @NC@SiW 12 -300, showed a noticeable turnover frequency (TOF) (110.07 h -1 ) and lower activation energy (38.79 kJ mol -1 ) in oxidative desulfurization (ODS) with good recyclability. HO˙ radical was found to be the active species involved in ODS as confirmed by the EPR and scavenger experiments. Additionally, the fabricated catalyst can be conveniently separated and recycled within an externally applied magnetic field.