Preparation And Properties Of MnOx, LaMnO₃ And LaVO₄ Catalysts For Catalytic Oxidation Of Chlorobenzene

The emission abatement of toxic chemicals, such as chlorinated aromatics and polychlorinated dioxins/furans (PCDD/F) has attracted much attention from academia, industry, government and public with the growing environmental crisis; and the zero emission of dioxins through catalytic oxidation of dioxin-like compounds at low temperatures is a useful strategy and becomes the ultimate goal for scietists and industry. In this thesis work, the catalytic oxidation of chlorobenzene (CB), a common substitute material of dioxins in laboratory, on MnOx/TiO2-CNTs, LaMnO3 and LaV04 catalysts has been investigated.Catalytic oxidation of CB was tested over MnOx/TiO2-CNTs catalysts prepared by mechanical-chemical (high-energy ball-milling). The results show that, all the samples showed high catalytic activity for CB oxidation; among them the catalyst with 20wt%MnOx was identified as the most active one with an efficiency to destruct 97.4%of CB at 300℃. Moreover, effects of space velocity, and TiO2/CNTs supports on their catalytic activity and stability were also studied. To further improve the catalytic oxidation of CB at low temperature, we doped the catalyst with CeO2 and V2O5. The results showed that the doping of CeO2 increased the catalytic oxidation of CB, while the doping of V2O5 decreased the catalytic property at low temperature.Catalytic oxidation of CB was also tested over perovskite-type LaMnO3 and LaVO4 catalysts prepared by sol-gel. The results showed that the LaMnO3 catalyst presented higher catalytic oxidation of CB than LaVO4 catalyst at low temperature. While the reaction temperature was higher than 300℃, LaVO4 showed higher catalytic oxidation of CB than LaMnO3 catalyst. When Sr partial substituted for La to form Lao.8Sr0.2Mn03 perovskite catalyst, the conversion rate of CB was lower than LaMnO3 catalyst at low temperatures. But, when the reaction temperature was above 200℃, exhibited superior performance on catalytic oxidation of CB. After catalyst was activated at 300℃for 12 hours, the conversion of CB had been significantly improved at low temperature. The efficiency of catalytic oxidation of CB increased from 67.9%to 77.6%at 150℃. In addition, both of LaMnO3 and LaVO4 showed good activity for catalytic oxidation of NH3 to NOx. The NOx conversion achieved 88% and 95% for LaMnO3 and LaVO4, respectively at 600℃.