Catalytic Oxidation Of Chlorobenzene Over MnOx With Different Phase Structures And Morphology

Chlorinated volatile organic compounds （CVOCs） are hazardouspollutants due to their strong bioaccumulation potential and acute toxicity,and therefore, the safe disposal of CVOCs pollutants has acquired greatimportance with the ever increasing concern for environmentalprotections. So far as we are concerned, the catalytic oxidation of CVOCsto carbon dioxide, HCl, and water is the best method for their degradation.In this paper, the related research and progress on catalysts for catalyticdestruction of CVOCs and dioxins were reviewed. The main concern wasfocused on the controlled preparation and catalytic properties of differentphase structures MnO₂nanorods and different morphologies Mn₂O₃forthe combustion of chlorobenzene （CB）.The α、β、γ-MnO₂nanorods were synthesized via a hydrothermalroute, the MnO₂nanorods with different phase structures exhibited highactivities for low temperature catalytic oxidation of CB, and had highresistance to chloride poisoning. The activities of the MnO₂nanorods forCB oxidation depended strongly on the crystal phase of MnO₂, followingin the order of α-MnO₂> γ-MnO₂> β-MnO₂. In addition, the excellentreducibility and catalytic performance of α-MnO₂nanorods resulted fromexcellent reducibility and weaker Mn-O bond due to its better latticeoxygen mobility. The excellent reducibility and Mn-O bond strength ofthe MnO₂nanorods were the major factors to their catalytic activity inCB oxidation. Catalysts of CeO2/α-MnO₂with different Ce content weresubsequently prepared by impregnation. The results indicated that thecatalytic activity of CeOX/α-MnO₂for CB combustion decreased. The Ceion doped onto the surface of α-MnO₂may block up the microsporetunnel with the surface area dropping dramatically.Various Mn₂O₃structures such as hollow spheres、hollow cubes、nanorods and sea urchin were synthesized, Mn₂O₃hollow cubes exhibitedthe highest catalytic activity. The activity of catalytic combustion for CB obviously depended on the morphologies of Mn₂O₃, the hollow structurewith excellent reducibility showed higher CB removal efficiencies.