The mechanism of Ce-MCM-41 catalyzed peroxone reaction into •OH and •O2− radicals for enhanced NO oxidation

Abstract

A series of Cerium-doped MCM-41 were prepared by hydrothermal method and used in peroxone process (O3/H2O2) for low-temperature NO oxidation. The experimental results showed that the NO oxidation efficiency could reach 93% for 3Ce-MCM-41 (molar ratio Ce/Si = 3%) under the molar ratio of H2O2/NO = 2.8 and O3/NO = 0.5. The addition of SO2 was conducive to the improvement of NO oxidation efficiency, which was assigned to SO2 improving the desorption of the intermediate product NO2 and promoting the progress of NO oxidation reaction. The hydroxyl and superoxide radical scavenger tert‑butanol and p-Quinone confirmed that O3/H2O2/3Ce-MCM-41 followed the •OH and •O2− radicals co-oxidation mechanism. Afterwards, the characterized results exhibited that Ce was incorporated into the framework of MCM-41 and presented in tetrahedral coordination, which enhanced Lewis acid sites over Ce-MCM-41 samples. Besides, the presence of Ce3+/Ce4+ promoted electron transfer. Meanwhile, the high surface area of 3Ce-MCM-41 (819 m2•g−1) was benefited to reactants transfer. Thus, O3/H2O2/3Ce-MCM-41 process achieved a high NO oxidation efficiency.