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 Na 12 [α-P 2 W 15 O 56 ]·24H 2 O (P 2 W 15 ) was covalently tethered onto the γ-Al 2 O 3 sphere, to which different alkyl chains (C n, n = 8, 12, or 18) were grafted, leading to the formation of the Al 2 O 3 -P 2 W 15 -C n . When the Al 2 O 3 -P 2 W 15 -C n were applied to catalyze oxidative desulfurization reaction of dibenzothiophene (DBT) in the presence of H 2 O 2, it displayed high efficiency for removal of sulfur content in 9 min under optimized conditions at 60 °C. In addition, the Al 2 O 3 -P 2 W 15 -C n 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 Al 2 O 3 -P 2 W 15 -C 18 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 DBTO 2 (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.