Shu-ming Liu

The enhanced resistance to P species of an Mn–Ti catalyst for selective catalytic reduction of NOx with NH3 by the modification with Mo

Phosphorous has a deactivation effect on an SCR catalyst. In this study, the effect of Mo modification on the resistance to P species of a Mn–Ti catalyst for selective catalytic reduction of NOx with NH3 was investigated. It was found that the addition of Mo could greatly improve the P species tolerance of the Mn–Ti catalyst. From the characterization results of BET, XRD, H2-TPR, NH3-TPD and XPS, it could be concluded that the modification of the Mn–Ti catalyst by Mo could enhance its specific surface area, redox ability and NH3 adsorption capacity, along with the generation of more surface chemisorbed oxygen species, as a result, greatly enhancing the P species resistance of the Mn–Ti catalyst. The results of an in situ DRIFT study indicated that the NH3-SCR reactions over Mn–Ti and Mn–Mo–Ti catalysts were governed by L–H mechanism (≤200 °C) and E–R mechanism (>200 °C) respectively.

The enhanced performance of a CeSiOx support on a Mn/CeSiOx catalyst for selective catalytic reduction of NOx with NH3

A series of Mn/CeSiOx catalysts were prepared by the wet impregnation method and used for selective catalytic reduction of NO with NH3. As can be seen from the experimental results, the Mn/CeSiOx catalyst with a Ce/Si molar ratio of 2/1 showed excellent low-temperature SCR activity, high N2 selectivity and excellent SO2 and H2O tolerance. The relationship between the CeSiOx support and the SCR performance of Mn/CeSiOx (2 : 1) catalyst was investigated based on the characterization results of N2 adsorption, XRD, XPS, H2-TPR, NH3-TPD and in situ DRIFT. The strong interaction between Ce and Si resulted in the good dispersion of Mn species on the support; correspondingly, the redox ability and NH3 adsorption capacity were greatly enhanced. The results of in situ DRIFT study revealed that the NH3-SCR reactions over Mn/CeO2 and Mn/CeSiOx (2 : 1) mainly obeyed both the E–R mechanism and the L–H mechanism. Furthermore, the formation of more Mn4+ and chemisorbed oxygen greatly facilitates the oxidation of NO to NO2, as a result, promoting the low-temperature SCR performance of Mn/CeSiOx (2 : 1).

A study on simultaneous catalytic ozonation of Hg0 and NO using Mn–TiO2 catalyst at low flue gas temperatures

Mn–TiO2 catalysts were utilized as an ozonation catalyst for the first time to study the simultaneous catalytic ozonation of Hg0 and NO at low flue gas temperatures. BET, SEM–EDS, XRD, XPS, H2-TPR, NOx-TPD and Hg0-TPD were used to characterize the catalysts. The Mn–TiO2 catalyst, in which the molar content of metal Mn was 60%, exhibited the best catalytic activities of Hg0 and NO oxidation, compared with other Mn–TiO2 catalysts. It was found that within the range of experiment, the catalytic ozonation efficiency of Hg0 and NO was higher than that of ozonation or catalytic oxidation. The results also showed that the presence of NO gas inhibited the catalytic ozonation of elemental mercury, and the inhibition was enhanced with the NO inlet concentration, while few elemental mercury molecules did promote the catalytic ozonation of NO. The addition of H2O vapor promoted the catalytic ozonation of Hg0 and NO. In addition, 0.6Mn–TiO2 catalyst demonstrated a good TOS and cyclic stability. The catalytic ozonation of NO and Hg0 on Mn–TiO2 catalyst likely followed the Langmuir–Hinshelwood mechanism, where the hydroxyl radicals reacted with adjacently adsorbed NO molecules and elemental mercury on catalyst surface.