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Manganese oxide catalysts, including γ-MnO₂, Mn₂O₃ and Mn₃O₄, were synthesized by a precipitation method using different precipitants and calcination temperatures. The catalytic oxidations of benzene and 1,2-dichloroethane (1,2-DCE) were then carried out. The effects of the calcination temperature on the catalyst morphology and activity were investigated. It was found that the specific surface area and reducibility of the catalysts decreased with the increase in the calcination temperature, and both the γ-MnO₂ and Mn₃O₄ were converted to Mn₂O₃. These catalysts showed good activity and selectivity for the benzene and 1,2-DCE oxidation. The γ-MnO₂ exhibited the highest activity, followed by the Mn₂O₃ and Mn₃O₄. The high activity could be associated with the large specific surface area, abundant surface oxygen species and excellent low-temperature reducibility. Additionally, the catalysts were inevitably chlorinated during the 1,2-DCE oxidation, and a decrease in the catalytic activity was observed. It suggested that a higher reaction temperature could facilitate the removal of the chlorine species. However, the reduction of the catalytic reaction interface was irreversible.