Simultaneous oxidation of Hg0 and NH3-SCR of NO by nanophase Ce x Zr y Mn z O2 at low temperature: the interaction and mechanism.

Simultaneous oxidation of Hg0 and NH3-SCR of NO by catalyst is one of the key methods for co-purification of coal-fired flue gas. Till now, the interaction between the oxidation of Hg0 and NH3-SCR of NO and its mechanism have not clarified. In this study, a series of nanophase Ce x Zr y Mn z O2 was prepared for the simultaneous oxidation of Hg0 and NH3-SCR of NO at low temperature. The catalysts were characterized using surface area analysis, X-ray diffraction, temperature-programmed techniques, and several types of microscopy and spectroscopy. The experimental results indicated that the Ce0.47Zr0.22Mn0.31O2 exhibited superior Hg0 removal efficiency (> 99%) and NO conversion efficiency (> 90%) even at 150 °C, and it also exhibited a good durability in the presence of SO2 and H2O. The excellent performance of Ce0.47Zr0.22Mn0.31O2 on co-purifying Hg0 and NO was due to the stronger synergistic effects of Ce-Zr-Mn in Ce0.47Zr0.22Mn0.31O2 than that of the others, which was illustrated by the characterization results of XPS, XRD, and FT-IR. Moreover, it was found that the NO conversion of Ce0.47Zr0.22Mn0.31O2 could be slightly influenced by Hg0 and was decreased about 4% to the max, while that of Hg0 could rarely be affected by the selected catalytic reduction process of NO. It might be due to the co-purification mechanism of NO and Hg0. The mechanism of the simultaneous oxidation of Hg0 and NH3-SCR of NO was mainly due to the synergetic effect on the mobility of surface oxygen and the activation of lattice oxygen of Ce0.47Zr0.22Mn0.31O2. The effect of the oxidation of Hg0 on the NH3-SCR of NO was mainly due to the absorbed Hg0/Hg2+ on the surface of Ce0.47Zr0.22Mn0.31O2, which attenuated the formation of NH3(ad), -NH2(ad), and NH4+ on its acid sites. Similarly, the NH3-SCR of NO process could hardly influence the oxidation of Hg0 when NO and Hg0 were co-purified.