Vacuum-treated MnxCe1-xO2 nanorods for catalytic ozonation of 1,2-dichloroethane

Abstract

MnxCe1-xO2 nanorod catalysts were synthesized using SBA-15 as a template. In MnxCe1-xO2, ultrahigh Mn ions entered into the CeO2lattice, resulting in Mn-O-Ce solid solution generation with increasing surface oxygen vacancies. Mn-O-Ce structure lessened crystalline MnO2 to decrease strong-acidity sites but to increase weak-moderate-acidity sites on the surface of MnxCe1-xO2. Vacuum drying deoxidated the surfaces of catalysts to elevate their surface oxygen vacancies. The deoxidation also decreased strong-acidity sites while increasing weak-moderate-acidity sites on the surface of MnxCe1-xO2. Among MnxCe1-xO2catalysts, NMn0.4Ce0.6O2 was screened out as the optimal catalyst, with outstanding catalytic performance and long-term stability, whose 1,2-dichloroethane (DCE) conversion and CO2 selectivity could reach up to 96% and 82%, respectively. The results indicated that the synergistic effect between surface acidity and oxygen vacancy played a critical role in the catalytic ozonation of DCE. The mechanism analysis indicated that chlorine species from DCE decomposition were easily bound to manganese oxides to form MnOxCly on NMnO2 during catalytic ozonation, leadingto the deactivation of NMnO2 and the formation of polychlorinated byproducts. Most of chlorine species were oxidated into ClO3- and ClO4- and further removed as Cl2 and HCl on NMn0.4Ce0.6O2 during the catalytic ozonation of DCE.