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 (C
n
, n = 8, 12, or 18) were grafted, leading to the formation of the Al2O3-P2W15-C
n
. When the Al2O3-P2W15-C
n
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-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 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.
The energetically viable fabrication of stable and highly efficient solid acid catalysts is one of the key steps in large‐scale transformation processes of biomass resources. Herein, the covalent modification of the classical Dawson polyoxometalate (POMs) with sulfonic acids (‐SO3H) is reported by grafting sulfonic acid groups on the POM's surface followed by oxidation of (3‐mercaptopropyl)trimethoxysilane. The acidity of TBA6‐P2W17‐SO3H (TBA=tetrabutyl ammonium) has been demonstrated by using 31P NMR spectroscopy, clearly indicating the presence of strong Brønsted acid sites. The presence of TBA counterions renders the solid acid catalyst as a promising candidate for phase transfer catalytic processes. The TBA6‐P2W17‐SO3H shows remarkable activity and selectivity, excellent stability, and great substrate compatibility for the esterification of free fatty acids (FFA) with methanol and conversion into biodiesel at 70 °C with >98 % conversion of oleic acid in 20 min. The excellent catalytic performance can be attributed to the formation of a catalytically active emulsion, which results in a uniform catalytic behavior during the reaction, leading to efficient interaction between the substrate and the active sites of the catalyst. Most importantly, the catalyst can be easily recovered and reused without any loss of its catalytic activity owing to its excellent phase transfer properties. This work offers an efficient and cost‐effective strategy for large‐scale biomass conversion applications.
Photocatalytic decarboxylative alkylations of C(sp 3 )-H and C(sp 2 )-H bonds enabled by ammonium iodide in amide solvent SCIENCE CHINA Chemistry 64, 439 (2021); Photoredox-catalyzed amide-directed selective sp 3 C-H bond functionalization Science Bulletin 61, 1892 (2016); Existence of aromatic sp 2 C-H…O = C intramolecular interaction similar to hydrogen bond Science in China Series B-Chemistry 39, 285 (1996); Palladium-catalyzed R 2 (O)P-directed C(sp 2 )-H activation SCIENCE CHINA Chemistry 58, 1280 (2015); C(sp 3 )-H bond functionalization of non-cyclic ethers by decarboxylative oxidative coupling with α,β-unsaturated carboxylic acids
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