Ultrafast Oxidative Desulfurization of Diesel Fuels by Mass Transfer Enhancement of Polyoxometalate Modified Alumina Catalysts

Deep desulfurization of fuels has long been and remains to be a highly challenging issue. In this work, a trilacunary polyoxometalate of Na12[α-P2W15O56]·24H2O (P2W15) was covalently tethered onto the γ-Al2O3 sphere, to which different alkyl chains (Cn, n = 8, 12, or 18) were grafted, leading to the formation of the Al2O3-P2W15-Cn. When the Al2O3-P2W15-Cn were applied to catalyze oxidative desulfurization reaction of dibenzothiophene (DBT) in the presence of H2O2, it displayed high efficiency for removal of sulfur content in 9 min under optimized conditions at 60 °C. In addition, the Al2O3-P2W15-Cn exhibited excellent structural stability during the catalytic reaction and can be used to remove 4,6-dimethyldibenzothiophene (4,6-DMDBT) and benzothiophene (BT) from fuel oils. The excellent performance of Al2O3-P2W15-C18 was verified by sulfur removal for an actual diesel sample. Molecular dynamics simulations indicated that DBT showed strong tendency to be adsorbed on active sites, while DBTO2 (dibenzothiophene sulfone) can be desorbed much easier. This work opens up a new avenue for further study on oxidative desulfurization catalytic materials and the influence of catalyst structure on mass transfer.