A study on simultaneous catalytic ozonation of Hg-0 and NO using Mn-TiO2 catalyst at low flue gas temperatures

摘要

Mn-TiO2 catalysts were utilized as an ozonation catalyst for the first time to study the simultaneous catalytic ozonation of Hg-0 and NO at low flue gas temperatures. BET, SEM-EDS, XRD, XPS, H-2-TPR, NO (x) -TPD and Hg-0-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 Hg-0 and NO oxidation, compared with other Mn-TiO2 catalysts. It was found that within the range of experiment, the catalytic ozonation efficiency of Hg-0 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 Hg-0 and NO. In addition, 0.6Mn-TiO2 catalyst demonstrated a good TOS and cyclic stability. The catalytic ozonation of NO and Hg-0 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.