Herein, three polyoxometalates, namely K3PW12O40·10H2O, K6[α-P2W18O62]·14H2O, and K8H[P2W15V3O62]·9H2O, were successfully prepared and used in the air/n-octanaloxidative desulfurization (ODS) system. Among the compounds, the Dawson-type polyoxometalate K6[α-P2W18O62]·14H2O exhibited the best performance, with a 99.63% desulfurization ratio. Then, K6[α-P2W18O62]·14H2O was supported on graphene oxide (GO) to obtain K6P2W18O62/GO. The prepared catalysts were characterized by Fourier transform infrared spectroscopy (FTIR), 31P nuclear magnetic resonance (31P NMR) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDX) spectroscopy, transmission electron microscopy (TEM), and Boehm titration. Using K6P2W18O62/GO as a catalyst, a final sulfur removal ratio of 96.10% was achieved without extraction post-treatment due to the inherent adsorption capacity of the catalyst. In addition, the factors influencing the desulfurization process were investigated. The recovery experiment showed that the supported catalyst could be reused 5 times with slight catalyst deactivation. Finally, the reaction mechanism was proposed with the aid of gas chromatography (GC), gas chromatography-mass spectrometry (GC-MS) and contrast tests.
Eight Dawson-type polyoxometalates were successfully prepared and used in an octanal/air oxidative desulfurization (ODS) system for model oil. Among which, the classical 2:18 polyoxometalate K 6 [α-P 2 W 18 O 62 ]·14H 2 O exhibited the best catalytic performance with a sulfur removal ratio of 99.63%. Then, K 6 [α-P 2 W 18 O 62 ]·14H 2 O was supported on graphene oxide (GO) to afford K 6 P 2 W 18 O 62 /GO using the hydrothermal method. Due to the in situ adsorption of the supported catalysts in the ODS process, the sulfur removal ratio was 96.10% without extraction treatment. Compared with the octanal/air ODS system using pure GO as an adsorbent for the oxidation products, the sulfur removal ratio increased from 89.21 to 96.10%, and the n -octanal/S molar ratio decreased from 24 to 4. To facilitate the recycling of the catalyst and avoid catalyst loss, K 6 [α-P 2 W 18 O 62 ]·14H 2 O was supported on magnetic graphene oxide (mGO) to afford K 6 P 2 W 18 O 62 /mGO. The results showed that the supported catalyst could be easily recovered with the aid of an external magnetic field, while maintaining high catalytic activity during five cycles of reuse with little catalyst loss. Furthermore, all the prepared materials were analyzed by a series of characterizations, and the reaction mechanism of the studied system was proposed through contrast tests and GC-MS characterization analysis.
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