PMo11V polyoxometalate encapsulated into hollow mesoporous carbon spheres: A highly efficient and ultra-stable catalyst for oxidative desulfurization

• PMo 11 V clusters are immobilized on hollow mesoporous carbon for catalytic oxidative desulfurization. • PMo 11 V@HMCS exhibit ultra-high DBT removal of 99.6% within 30 min. • PMo 11 V@HMCS can be easily recovered and reused more than 20 times. • The nanoscale pores in HMCS could effectively confine and anchor PMo 11 V. The synthesis of highly efficient and stable catalysts for oxidative desulfurization is still a challenging task. Herein, a composite material (PMo 11 V@HMCS) of vanadium-substituted polyoxometalate (PMo 11 V) encapsulated in the hollow mesoporous carbon spheres (HMCS) was prepared via an incipient wetness impregnation method. As-synthesized catalysts were systematically characterized by ICP-OES, Contact angle testing, FT-IR, XRD, SEM, TEM, BET and XPS. The oxidative desulfurization experiments showed that PMo 11 V@HMCS had higher conversion of dibenzothiophene (DBT) than PMo 11 V@AC and could completely remove DBT in the model fuel in 30 min. It is found that the hollow mesoporous structure can not only effectively promote the contact between substrate and catalytic active sites to provide sufficient internal space for the catalytic reaction, but also significantly improve diffusion and mass transfer. The amphiphilic catalyst with hydrophilicity and lipophilicity was in full contact with the reaction substrate and oxidant, which improved the catalytic performance. In addition, because the nanoscale pore size in HMCS can effectively confine and anchor the POM clusters and prevent the loss of catalytic active species, the catalyst also exhibited outstanding recyclability and stability. PMo 11 V@HMCS could be reused for at least twenty runs without an obvious decline in activity.