Room-temperature catalytic oxidation of benzo(a)pyrene by Ce-SBA-15 supported active CeSiO4 phase

A series of cerium-incorporated SBA-15 mesoporous materials were prepared through direct hydrothermal synthesis method, which was characterized by PXRD, N2 physisorption and TEM measurements. The low-angle PXRD and N2 physisorption results show the cerium successfully incorporated into the framework of SBA-15. The large angle PXRD results indicate that Ce-SBA-15 mesoporous materials supported CeSiO4 phase was in situ synthesized by adjusting pH to 6 with anhydrous triethylamine, and then calcined in air at 550 °C. The room-temperature adsorption behaviors of SBA-15 and Ce-SBA-15 materials for benzo(a)pyrene in cyclohexane solutions were investigated. Interestingly, Ce-SBA-15 materials reveal good catalytic performance for room-temperature oxidation benzo(a)pyrene to corresponding quinone through a radical oxidation mechanism, attributable to in situ forming active CeSiO4 phase which was supported in Ce-SBA-15 material. The benzo(a)pyrene transfer to quinone by CeSiO4 phase leads to higher adsorption capacity owing to higher affinity of quinone with mesoporous channels, as a result, some Ce-SBA-15 materials exhibit higher adsorption capacity for benzo(a)pyrene than SBA-15 material. The radical oxidation mechanism was demonstrated by EPR and the interception effect of a radical scavenger, TEMPO. The quinone-type molecule was identified by photoluminescence, ESI-MS, IR and NMR.

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► CeSiO4 phase was in situ formed during synthesis of Ce-SBA-15 mesoporous materials.
► Ce-SBA-15 possess of higher adsorption capacity for BaP than SBA-15.
► BaP can be transferred to corresponding quinone by CeSiO4 at room temperature.
► BaP transfer to corresponding quinone was ascribed to radical oxidation mechanism.