Analysis of mercury species over CuO-MnO2-Fe2O3/γ-Al2O3 catalysts by thermal desorption

The efficiency of the CuO-MnO2-Fe2O3/γ-Al2O3 (CMFA) catalysts on mercury oxidation and the effects of individual flue gas (O2, HCl, NO, SO2) were investigated in our previous study. To elucidate the mercury oxidation mechanism, a thermal desorption (TD) method was applied in this study to analyze the characteristics of the mercury species formed on the CMFA catalysts. A series of pure mercury compounds mixed with fresh CMFA were first studied as the controls. Then, the TD method was employed to identify the Hg species formed on used CMFA catalysts pretreated under different operation conditions. The formation of HgO, HgCl2, Hg(NO3)2 and HgSO4 during the oxidation process was confirmed and the reaction pathway proposed. The mercury species present were mainly HgCl2 after CMFA catalysts were used to oxidize Hg0 under simulated flue gas conditions. HgO and HgSO4 were found to exist in very low concentrations. This has shown that the TD method is an efficient technique for mercury speciation on the catalyst surface.