Catalytic oxidation of elemental mercury by Mn–Mo/CNT at low temperature

• Mn/CNT showed strong mercury oxidation ability in the presence of only 6% O2.
• SO2 obviously promoted the Hg0 oxidized by Mn–Mo/CNT.
• Mn–Mo/CNT was an effective low temperature catalyst for Hg0 oxidation.

Mercury oxidized by a type of novel carbon nanotube catalyst was studied in this work. The results of this suggest that in the absence of HCl, Mn/CNT could perfectly catalytic the process of O2 oxidizing Hg0 at 150–250 °C, and even with only 10 ppm HCl present, this catalyst could attain a high mercury oxidation efficiency. The optimal temperature and MnO2 content for mercury oxidation was 250 °C and 5 wt%. However, Mn/CNT almost lost the ability to oxidize mercury in the presence of 500 ppm SO2 because SO2 reacted with MnO2 in the catalyst to form manganese sulfate. Tests of mercury oxidized by Mn–Mo/CNT indicated that SO2 could enhance mercury oxidation by this catalyst and that the optimal temperature for mercury oxidized by Mn–Mo/CNT decreased to 150 °C mainly because Mo was able to promote the transformation of SO2 to SO3, which is beneficial for mercury oxidation, and Mo was also able protect the catalytic activation of MnO2 on the catalyst. Tests over a long period of time showed that Mn–Mo/CNT was an effective available low temperature catalyst for mercury oxidation and that Hg0 oxidized by HCl over Mn–Mo/CNT follows the Langmuir–Hinshelwood mechanism.