Studies on Reaction Mechanism of SO_2 Reduction Catalyzed by CeO_2-La_2O_3/γ-Al_2O_3

Supported catalysts CeO 2/γ-Al 2O 3, La 2O 3/γ-Al 2O 3 and CeO 2-La 2O 3/γ-Al 2O 3 were prepared by impregnation. The studies were engaged in the catalytic reduction of SO 2 by CO over the catalysts under the following conditions: feed gas 25%SO 2-75%CO, with N 2 as a carrier gas, flow rate 1 L/min and catalyst mass 15 g. The activation process and catalytic activity of the catalysts, as well as the effect of the concentration ratio of the reactants on the catalytic reaction were investigated. The XRD and XPS were used to characterize the catalysts before and after the reaction. The result demonstrated that the activation temperature of CeO 2-La 2O 3/γ-Al 2O 3 is 50～100 ℃ lower than that of La 2O 3/γ-Al 2O 3 or CeO 2/γ-Al 2O 3, and CeO 2-La 2O 3/γ-Al 2O 3 has higher activity than La 2O 3/γ-Al 2O 3 or CeO 2/γ-Al 2O 3 for catalytic reduction of SO 2 by CO. This result revealed the synergism between redox reaction of CeO 2 and COS intermediate reaction of La 2O 3. The experimental results showed that the generation of elemental sulfur from the redox reaction of CeO 2 was an important source of COS intermediate reaction through the whole reaction, based on which a redox-COS overlapped reaction mechanism was proposed for the reduction of SO 2 by CO over CeO 2-La 2O 3/γ-Al 2O 3.