Adsorption of Gas-Phase Mercury Using Ceria-Titania Materials

It has long been known that metal oxides can adsorb mercury from the vapor phase. In particular, in a study of the application titania-supported manganese oxide to the removal of mercury from coal combustion flue gas, titania-supported manganese oxide was found to have an elemental mercury uptake of more than 50 mg/g in fixed-bed adsorption tests using a nitrogen environment at 175°C. However, sulfur dioxide, which is typically present in flue gas, has a negative and irreversible effect on elemental mercury capture. To overcome this limitation, ceria-titania materials were considered as mercury adsorbents. Manganese dioxide supported on ceria-titania can be used for vapor phase elemental mercury capture from nitrogen at 160 to 200°C; mercury capacities ranged from 4 to 54 mg Hg⁰/g adsorbent depending on the specific gas composition and temperature. High mercury capacities were observed for elemental mercury capture using ceria-titania-supported manganese oxide in the absence of sulfur dioxide; while low but consistent mercury capacities (6 – 8 mg Hg⁰/g adsorbent) were observed for the ceria-titania support alone at 160°C. The mercury capacity of the ceria-titania support was relatively insensitive to the presence of sulfur dioxide and nitrogen oxide. Additional testing indicates that these materials can be used to capture elemental and oxidized mercury simultaneously; thus ceria-titania merits additional investigation as a mercury adsorbent.