Stabilization of mercury over Mn-based oxides: Speciation and reactivity by temperature programmed desorption analysis.

Mercury temperature-programmed desorption (Hg-TPD) method was employed to clarify mercury species over Mn-based oxides. The elemental mercury (Hg0) removal mechanism over MnOx was ascribed to chemical-adsorption. HgO was the primary mercury chemical compound adsorbed on the surface of MnOx. Rare earth element (Ce), main group element (Sn) and transition metal elements (Zr and Fe) were chosen for the modification of MnOx. Hg-TPD results indicated that the binding strength of mercury on these binary oxides followed the order of Sn-MnOx<Ce-MnOx∼MnOx<Fe-MnOx<Zr-MnOx. The activation energies for desorption were calculated and they were 64.34, 101.85, 46.32, 117.14, and 106.92eV corresponding to MnOx, Ce-MnOx, Sn-MnOx, Zr-MnOx and Fe-MnOx, respectively. Sn-MnOx had a weak bond of mercury (Hg-O), while Zr-MnOx had a strong bond (HgO). Ce-MnOx and Fe-MnOx had similar bonds compared with pure MnOx. Moreover, the effects of SO2 and NO were investigated based on Hg-TPD analysis. SO2 had a poison effect on Hg0 removal, and the weak bond of mercury can be easily destroyed by SO2. NO was favorable for Hg0 removal, and the bond strength of mercury was enhanced.