Development of silica/vanadia/titania catalysts for removal of elemental mercury from coal-combustion flue gas
- University of Florida, FL (United States). Department of Environmental Engineering Sciences
SiO{sub 2}/V{sub 2}O{sub 5}/TiO{sub 2} catalysts were synthesized for removing elemental mercury (Hg{sup 0}) from simulated coal-combustion flue gas. Experiments were carried out in fixed-bed reactors using both pellet and powder catalysts. In contrast to the SiO{sub 2}-TiO{sub 2} composites developed in previous studies, the V{sub 2}O{sub 5} based catalysts do not need ultraviolet light activation and have higher Hg{sup 0} oxidation efficiencies. For Hg{sup 0} removal by SiO{sub 2}-V{sub 2}O{sub 5} catalysts, the optimal V{sub 2}O{sub 5} loading was found between 5 and 8%, which may correspond to a maximum coverage of polymeric vanadates on the catalyst surface. Hg{sup 0} oxidation follows an Eley-Rideal mechanism where HCl, NO, and NO{sub 2} are first adsorbed on the V{sub 2}O{sub 5} active sites and then react with gas-phase Hg{sup 0}. HCl, NO, and NO{sub 2} promote Hg oxidation, while SO{sub 2} has an insignificant effect and water vapor inhibits Hg{sup 0} oxidation. The SiO{sub 2}-TiO{sub 2}-V{sub 2}O{sub 5} catalysts exhibit greater Hg{sup 0} oxidation efficiencies than SiO{sub 2}-V{sub 2}O{sub 5}, may be because the V-O-Ti bonds are more active than the V-O-Si bonds. This superior oxidation capability is advantageous to power plants equipped with wet-scrubbers where oxidized Hg can be easily captured. The findings in this work revealed the importance of optimizing the composition and microstructures of SCR (selective catalytic reduction) catalysts for Hg{sup 0} oxidation in coal-combustion flue gas. 33 refs., 5 figs., 2 tabs.
- OSTI ID:
- 21085059
- Journal Information:
- Environmental Science and Technology, Vol. 42, Issue 14; Other Information: cywu@ufl.edu; ISSN 0013-936X
- Country of Publication:
- United States
- Language:
- English
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