Li Ying, Murphy Patrick D, Wu Chang-Yu, Powers Kevin W, Bonzongo Jean-Claude J
Department of Environmental Engineering Sciences, University of Florida, USA.
Environ Sci Technol. 2008 Jul 15;42(14):5304-9. doi: 10.1021/es8000272.
SiO2/V2O5/TiO2 catalysts were synthesized for removing elemental mercury (Hg0) from simulated coal-combustion flue gas. Experiments were carried out in fixed-bed reactors using both pellet and powder catalysts. In contrast to the SiO2-TiO2 composites developed in previous studies, the V2O5 based catalysts do not need ultraviolet light activation and have higher Hg0 oxidation efficiencies. For Hg0 removal by SiO2-V2O5 catalysts, the optimal V2O5 loading was found between 5 and 8%, which may correspond to a maximum coverage of polymeric vanadates on the catalyst surface. Hg0 oxidation follows an Eley-Rideal mechanism where HCI, NO, and NO2 are first adsorbed on the V2O5 active sites and then react with gas-phase Hg0. HCI, NO, and NO2 promote Hg oxidation, while SO2 has an insignificant effect and water vapor inhibits Hgo oxidation. The SiO2-TiO2-V2O5 catalysts exhibit greater Hg0 oxidation efficiencies than SiO2-V2O5, 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 Hg0 oxidation in coal-combustion flue gas.
合成了SiO2/V2O5/TiO2催化剂，用于从模拟煤燃烧烟气中去除单质汞（Hg0）。使用颗粒催化剂和粉末催化剂在固定床反应器中进行了实验。与先前研究中开发的SiO2-TiO2复合材料不同，基于V2O5的催化剂不需要紫外线活化，并且具有更高的Hg0氧化效率。对于SiO2-V2O5催化剂去除Hg0，发现最佳V2O5负载量在5%至8%之间，这可能对应于催化剂表面聚合钒酸盐的最大覆盖率。Hg0氧化遵循Eley-Rideal机理，其中HCl、NO和NO2首先吸附在V2O5活性位点上，然后与气相Hg0反应。HCl、NO和NO2促进Hg氧化，而SO2的影响不显著，水蒸气抑制Hg0氧化。SiO2-TiO2-V2O5催化剂比SiO2-V2O5表现出更高的Hg0氧化效率，这可能是因为V-O-Ti键比V-O-Si键更具活性。这种优异的氧化能力对于配备湿式洗涤器的发电厂是有利的，在那里氧化态的Hg可以很容易地被捕获。这项工作的研究结果揭示了优化SCR（选择性催化还原）催化剂的组成和微观结构对于煤燃烧烟气中Hg0氧化的重要性。
