Catalytic Oxidation of Elemental Mercury over the Modified Catalyst Mn/alpha-Al2O3 at Lower Temperatures

In order to facilitate the removal of elemental mercury (Hg-0) from coal-fired flue gas, catalytic oxidation of Hg-0 with manganese oxides supported on inert alumina (alpha-Al2O3) was investigated at lower temperatures (373-473 K). To improve the catalytic activity and the sulfur-tolerance of the catalysts at lower temperatures, several metal elements were employed as dopants to modify the catalyst of Mn/alpha-Al2O3. The best performance among the tested elements was achieved with molybdenum (Mo) as the dopant in the catalysts. It can work even better than the noble metal catalyst Pd/alpha-Al2O3. Additionally, the Mo doped catalyst displayed excellent sulfur-tolerance performance at lower temperatures, and the catalytic oxidation efficiency for Mo(0.03)-Mn/alpha-Al2O3 was over 95% in the presence of 500 ppm SO2 versus only about 48% for the unmodified catalyst The apparent catalytic reaction rate constant increased by approximately 5.5 times at 423 K. In addition, the possible mechanisms involved in Hg-0 oxidation and the reaction with the Mo modified catalyst have been discussed.