Insights into the Inhibitory Effect of H 2 O on Hg‐Catalytic Oxidation over the MnO x ‐Based Catalysts

MnO x ‐based catalyst has been used for elemental mercury (Hg 0 ) removal in the coal‐fired flue gas, but the H 2 O in the flue gas significantly inhibits its activity. Generally, it is believed the inhibitory effect is caused by competitive adsorption between Hg 0 /HCl and H 2 O. In this study, we found that the MnO x was also aged in the flue gas with high concentration of H 2 O. The results indicated that the catalysts would be aged by H 2 O. The characterization of the fresh and aged catalysts showed that the amount of Mn 4+ and chemisorbed oxygen species decreased. H 2 O didn't inhibit HCl adsorption on the catalyst surface, but suppressed the formation of active chlorine species, which was active for Hg 0 removal. Therefore, besides the generally known competitive adsorption mechanism, there should be other possible reasons to interpret the inhibitory effects of water vapor on Hg 0 oxidation process.