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Chlorobenzene oxidation using ozone over iron oxide and manganese oxide catalysts

Wang, Hou Chuan, Liang, Hsu Shang, Chang, Moo Been
Journal of hazardous materials 2011 v.186 no.2-3 pp. 1781-1787
activation energy, active sites, byproducts, carbon dioxide, catalysts, iron oxides, manganese oxides, oxidation, ozone, temperature
A low-temperature catalytic oxidation of chlorobenzene (CB) has been performed at temperatures of 60–210°C using ozone (O₃) over iron oxide and manganese oxide, respectively. In the absence of ozone, CB conversion achieved with these two catalysts at 200°C was below 10%. However, addition of 1200ppm ozone results in a remarkable increase in CB conversion and the conversion reaches 91.7% at 150°C for iron oxide, while 81.5% conversion is achieved with manganese oxide at 90°C. The activation energy of manganese oxide (48kJmol⁻¹) is higher than that of iron oxide (43kJmol⁻¹) without ozone. However, as ozone is added, the activation energy is significantly reduced to 20.0kJmol⁻¹ for iron oxide. CO and CO₂ are the only carbon-containing products detected in the effluent gas stream. For the long-term test, no obvious deactivation was found in iron oxide and ozone. However, in the case of manganese oxide and ozone, 3% reduction of CB conversion was observed. Slight deactivation might be attributed to a small amount of reaction byproducts (carboxylic acid species) and residual chloride (MnCl₂) being deposited on the active sites of the catalysts.