Adsorption and Catalytic Oxidation of Gaseous Elemental Mercury in Flue Gas over MnOx/Alumina

MnOx/Al2O3 A catalysts (i.e., impregnating manganese oxide on alumina) were employed to remove elemental mercury (Hg-0) from flue gas. MnOx/Al2O3 was found to have significant adsorption performance on capturing Hg-0 in the absence of hydrogen chloride (HCl), and its favorable adsorption temperature was about 600 K. However, the catalytic oxidation of Hg-0 became dominant when HCl or chlorine (Cl-2) was present in flue gas, and the removal efficiency of Hg-0 was up to 90% with 20 ppm of HCl or 2 ppm of Cl-2. In addition, the catalysts with adsorbed mercury could be chemically regenerated by rinsing with HCi gas to strip off the adsorbed mercury in the form of HgCl2. Sulfur dioxide displayed inhibition to the adsorption of Hg-0 on the catalysts, but the inhibition was less to the catalytic oxidation of Hg-0, especially in the presence of Cl-2. The analysis results of XPS and pyrolysis-AAS indicated that the adsorbed mercury was mainly in the Forms of mercuric oxide (HgO) and the weakly bonded speciation, and the ratio of them varied with the adsorption amount and manganese content on catalysts. The multifunctional performances of MnOx/Al2O3 on the removal of Hg-0 appeared to he promising in the industrial applications.