Boxiong Shen

Effects of flue gas components on removal of elemental mercury over Ce-MnOx/Ti-PILCs.

The adsorption and oxidation of elemental mercury (Hg(0)) under various flue gas components were investigated over a series of Ce-MnOx/Ti-PILC catalysts, which were synthesized by an impregnation method. To discuss the mechanism, the catalysts were characterized by various techniques such as N2 adsorption-desorption, scanning electron microscope (SEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR) analysis and X-ray photoelectron spectroscopy (XPS). The results indicated that the presence of 500 ppm SO2 in the flue gas significantly restrained the Hg(0) adsorption and oxidation over 6%Ce-6%MnOx/Ti-PILC due to the formation of SO4(2-) species. Hg(0) could be oxidized to HgCl2 in the presence of HCl, because the Deacon process occurred. NO would react with active oxygen to form NO2-containing species, which facilitated Hg(0) oxidation. While the presence of NO limited the Hg(0) adsorption on 6%Ce-6%MnOx/Ti-PILC due to the competitive adsorption of NO with Hg(0). The addition of NH3 in the flue gas significantly restrained Hg(0) adsorption and oxidation, because the formed NH4(+) species covered the active adsorption sites on the surfaces, and further limited Hg(0) oxidation. However, when NO and NH3 were simultaneously added into the flue gas, the Hg(0) oxidation efficiency of 6%Ce-6%MnOx/Ti-PILC exhibited a relatively high value (72%) at 250°C, which indicated the practicability to use Ce-MnOx/Ti-PILC for Hg(0) removal under SCR conditions.

Simultaneous removal of NO and Hg0 over Ce-Cu modified V2O5/TiO2 based commercial SCR catalysts

A series of novel Ce-Cu modified V2O5/TiO2 based commercial SCR catalysts were prepared via ultrasonic-assisted impregnation method for simultaneous removal of NO and elemental mercury (Hg0). Nitrogen adsorption, X-ray diffraction (XRD), temperature programmed reduction of H2 (H2-TPR) and X-ray photoelectron spectroscopy (XPS) were used to characterize the catalysts. 7% Ce-1% Cu/SCR catalyst exhibited the highest NO conversion efficiency (>97%) at 200-400°C, as well as the best Hg0 oxidation activity (>75%) at 150-350°C among all the catalysts. The XPS and H2-TPR results indicated that 7% Ce-1% Cu/SCR possess abundant chemisorbed oxygen and good redox ability, which was due to the strong synergy between Ce and Cu in the catalyst. The existence of the redox cycle of Ce4++Cu1+↔Ce3++Cu2+ could greatly improve the catalytic activity. 7% Ce-1% Cu/SCR showed higher resistance to SO2 and H2O than other catalysts. NO has a promoting effect on Hg0 oxidation. The Hg0 oxidation activity was inhibited by the injection of NH3, which was due to the competitive adsorption and oxidized mercury could be reduced by ammonia at temperatures greater than 325°C. Therefore, Hg0 oxidation could easily occurred at the outlet of SCR catalyst layer due to the consumption of NH3.

A comparative study of manganese–cerium doped metal–organic frameworks prepared via impregnation and in situ methods in the selective catalytic reduction of NO

Mn and Ce were loaded on metal–organic frameworks (MOFs) via impregnation and in situ doping methods. The catalytic capacities of the obtained composite materials were evaluated in the selective catalytic reduction (SCR) of NO. The existing form of Mn–Ce in the MOF originates from different doping methods and its effect on the catalytic performance was investigated. Mn–Ce introduced by impregnation was deposited on the surface of the MOF and exhibited high catalytic efficiency of more than 98% from 200 °C to 300 °C. According to the results of BET, XRD, XPS, and ICP analyses, it was concluded that Mn–Ce introduced via the in situ doping method was inserted in the crystal lattice structure of the MOF, which resulted in an enlarged surface area, low Mn concentration, and poor redox property as compared to that introduced via the impregnated method. By exploring these factors, it was proven that the limited redox ability was the direct reason that resulted in the low activity of the MnCeMOF. Using thermal decomposition, the in situ doped Mn–Ce was liberated from the MnCeMOF crystal lattice and subsequently, exhibited recovered redox properties and catalytic activity. In this study, we proved that different doping methods lead to different forms of Mn–Ce in the MOF, which exhibit different redox properties and thus directly lead to different catalytic performance.