(399d) Sulfur Tolerant MnOx/CeO2 Sorbents for Elemental and Oxidized Hg Removal From Flue Gas

Mercury is a highly toxic element that is released both naturally and as a result of human activity. The U.S. EPA has identified mercury as a Hazardous Air Pollutant. Mercury vapor is emitted from power plants as a mixture of elemental mercury, oxidized mercury, and mercury adsorbed to particulates. In our previous studies we reported developments of Mn/TiO₂ and Mn/CeO₂-TiO₂ sorbents for the combined removal of the elemental and oxidized mercury. Addition of CeO₂ to the Mn/TiO₂ increased the Hg capacity and sulfur tolerance. X-ray photoelectron spectroscopy (XPS) results indicate that the adsorbed mercury is present as both Hg⁰ and Hg²⁺ on these ceria-based materials. The XPS observations also suggest that the presence of both Ce³⁺ and Ce⁴⁺ oxidation states in the CeO₂-TiO₂ support and interaction between Mn and Ce is responsible for the HgO formation as well as sulfur tolerance. Hence, the present study mainly aimed at investigating Mn/CeO₂ materials for the elemental and oxidized mercury capture. We prepared MnOx-CeO₂ materials in different ways by using different synthesis methods like co-impregnation, sequential impregnation, co-precipitation, and deposition-precipitation methods. These materials were evaluated for the simultaneous capture of elemental and oxidized mercury from gas phase; the effects of manganese loading and gas-phase sulfur dioxide, carbon monoxide, and nitrogen monoxide were determined. To determine the structural and surface properties of the catalysts and to find out the elemental oxidation state of Mn, the fresh and spent catalysts were characterized by using XRD, TPR, TPD and X-ray photo electron spectroscopy techniques. These results will be presented in this study.