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

Abstract

The synthesis of highly efficient and stable catalysts for oxidative desulfurization is still a challenging task. Herein, a composite material (PMo11V@HMCS) of vanadium-substituted polyoxometalate (PMo11V) 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 PMo11V@HMCS had higher conversion of dibenzothiophene (DBT) than PMo11V@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. PMo11V@HMCS could be reused for at least twenty runs without an obvious decline in activity.