Low-temperature co-purification of NOx and Hg0 from simulated flue gas by CexZryMnzO2/r-Al2O3: the performance and its mechanism.

In this study, series of CexZryMnzO2/r-Al2O3 catalysts were prepared by impregnation method and explored to co-purification of NOx and Hg0 at low temperature. The physical and chemical properties of the catalysts were investigated by XRD, BET, FTIR, NH3-TPD, H2-TPR, and XPS. The experimental results showed that 10% Ce0.2Zr0.3Mn0.5O2/r-Al2O3 yielded higher conversion on co-purification of NOx and Hg0 than the other prepared catalysts at low temperature, especially at 200-300 °C. 91% and 97% convert rate of NOx and Hg0 were obtained, respectively, when 10% Ce0.2Zr0.3Mn0.5O2/r-Al2O3 catalyst was used at 250 °C. Moreover, the presence of H2O slightly decreased the removal of NOx and Hg0 owing to the competitive adsorption of H2O and Hg0. When SO2 was added, the removal of Hg0 first increased slightly and then presented a decrease due to the generation of SO3 and (NH4)2SO4. The results of NH3-TPD indicated that the strong acid of 10% Ce0.2Zr0.3Mn0.5O2/r-Al2O3 improved its high-temperature activity. XPS and H2-TPR results showed there were high-valence Mn and Ce species in 10% Ce0.2Zr0.3Mn0.5O2/r-Al2O3, which could effectively promote the removal of NOx and Hg0. Therefore, the mechanisms of Hg0 and NOx removal were proposed as Hg (ad) + [O] → HgO (ad), and 2NH3/NH4+ (ad) + NO2 (ad) + NO (g) → 2 N2 + 3H2O/2H+, respectively. Graphical abstract ᅟ.