Heterogeneous oxidation of elemental mercury vapor over RuO2/rutile TiO2 catalyst for mercury emissions control

• Highly dispersed RuO2 catalyst was synthesized over rutile TiO2.
• RuO2/rutile TiO2 catalyst showed good Hg(0) oxidation performance.
• HCl adsorption onto RuO2 was competitive with SO2 and NH3.
• RuO2/rutile TiO2 catalyst showed excellent SO2 resistance.

The catalytic oxidation of elemental mercury (Hg(0)) vapor is an effective way to enhance mercury removal from coal-fired power plants. RuO2 catalyst was found to be an excellent Hg(0) oxidation catalyst. When rutile TiO2 was used as the catalyst support, RuO2 formed well dispersed nano-layers due to the very similar crystal structures of RuO2 and rutile TiO2, giving higher Hg(0) oxidation activity over anatase TiO2 support. The RuO2/rutile TiO2 catalyst can be used at the tail end section of the selective catalytic reduction (SCR) unit for Hg(0) oxidation. It showed good Hg(0) oxidation performance under sub-bituminous and lignite coal simulated flue gas conditions with low concentration of HCl or HBr gas. The RuO2/rutile TiO2 catalyst also showed excellent resistance to SO2 under bituminous coal simulated flue gas, maintaining higher than 90% Hg(0) oxidation with up to 2,000 ppmv SO2 present. The oxidized mercury in a form of HgCl2 has a high solubility in water and can be easily captured by other air pollution control systems such as wet scrubbers in coal-fired power plants.

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