Efficient MnFeW/Ti catalyst for simultaneous removal of NO and Hg-0 in flue gas at low temperature: Effect of NO on Hg-0 oxidation and reaction mechanism

The MnFeW/Ti catalyst was synthesized and used for simultaneously removing NO and Hg-0 from flue gas at low temperature and its catalytic performance has been tested. The MnFeW/Ti catalyst showed over 80% NOx conversion and 88% Hg-0 removal between 180 and 300 degrees C at a high GHSV of 100000 h(-1). NO obviously enhanced the catalytic capability for Hg-0 removal and NH3 had almost no effect on Hg-0 removal because NH3 did not affect the adsorption of NO and Hg-0. Hg balance results revealed that Hg-0 removal over MnFeW/Ti catalyst proceeded via both chemisorption and catalytic oxidation, which is attributed to the different bonding strength between Hg-0 and active sites. The Hg-0 oxidation process was also investigated through transient reaction experiments along with Hg-TPD and XPS characterization. Hg-0 oxidation over MnFeW/Ti catalyst obeys both Mars-Maessen mechanism in which active oxygen reacts with adsorbed Hg-0 and Langmuir - Hinshelwood mechanism comprising the reaction of formed NO2 with adsorbed Hg-0. HgO, resulted from the reaction between NO2 as an active intermediate and adsorbed Hg-0, is liable to desorb from MnFeW/Ti catalyst.

Automated summary

The MnFeW/Ti catalyst shows excellent performance in simultaneously removing NO and Hg-0 from flue gas at low temperature, with complex mechanisms involved in the oxidation of Hg-0.