Catalytic oxidation and adsorption of Hg0 over low-temperature NH3-SCR LaMnO3 perovskite oxide from flue gas

• LaMnO3 was used for Hg0 removal at low temperature.
• O2 enhanced the Hg0 catalytic oxidation efficiency of LaMnO3.
• Hg-TPD were used for discuss the combing state of mercury on the surface of LaMnO3.

To simultaneously remove elemental mercury (Hg0) and NOx at low temperature from flue gas in coal-fired power plants, an efficient NH3-SCR LaMnO3 perovskite oxide was chosen as the catalyst for Hg0 removal. The physicochemical properties, surface reaction and mercury desorption were investigated using BET, XRD, XPS, H2-TPR and Hg-TPD, to investigate the Hg0 capture mechanism over LaMnO3 oxides. The results indicated that LaMnO3 exhibits a Hg0 capacity that is as high as 6.22 mg/g (600 min) at 150 °C. O2 enhanced the Hg0 removal performance by re-oxidation of reduced Mn3+ to Mn4+ and providing additional adsorbed oxygen. NO enhanced the Hg0 removal performance. However, NH3 exhibited negative effects on Hg0 removal. The NH3 + O2-TPD and NO + O2-TPD results indicated that the ad-NH3 species prevent Hg0 adsorption, but the ad-NO2 species were beneficial for Hg0 oxidation. The effects of SO2 and H2O were also investigated, and the results indicated that they inhibited Hg0 removal. Hg-TPD under different reaction atmospheres was employed to further investigate the combing state of Hg0 on LaMnO3 surface, the results indicated that mercury primarily existed as Hg–O, and LaMnO3 can be regenerated using thermal desorption.

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