Novel Effective Catalyst for Elemental Mercury Removal from Coal-Fired Flue Gas and the Mechanism Investigation

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• 作者：Wanmiao Chen ; Yang Pei ; Wenjun Huang ; Zan Qu ; Xiaofang Hu ; Naiqiang Yan
• 刊名：Environmental Science & Technology
• 出版年：2016
• 出版时间：March 1, 2016
• 年：2016
• 卷：50
• 期：5
• 页码：2564-2572
• 全文大小：485K
• ISSN：1520-5851

文摘

Mercury pollution from coal-fired power plants has drawn attention worldwide. To achieve efficient catalytic oxidation of Hg⁰ at both high and low temperatures, we prepared and tested novel IrO₂ modified Ce–Zr solid solution catalysts under various conditions. It was found that the IrO₂/Ce_0.6Zr_0.4O₂ catalyst, which was prepared using the polyvinylpyrrolidone-assisted sol–gel method, displayed significantly higher catalytic activity for Hg⁰ oxidation. The mechanism of Hg⁰ removal over IrO₂/Ce_0.6Zr_0.4O₂ was studied using various methods, and the Hg⁰ oxidation reaction was found to follow two possible pathways. For the new chemisorption–regeneration mechanism proposed in this study, the adsorbed Hg⁰ was first oxidized with surface chemisorbed oxygen species to form HgO; the HgO could desorb from the surface of catalysts by itself or react with adsorbed HCl to be release in the form of gaseous HgCl₂. O₂ is indispensable for the chemisorption process, and the doping of IrO₂ could facilitate the chemisorption process. In addition, the Deacon reaction mechanism was also feasible for Hg⁰ oxidation: this reaction would involve first oxidizing the adsorbed HCl to active Cl species, after which the Hg⁰ could react with Cl to form HgCl₂. Additionally, doping IrO₂ could significantly improve the Cl yield process. In summary, the novel IrO₂ modified catalyst displayed excellent catalytic activity for elemental mercury oxidation, and the proposed reaction mechanisms were determined reasonably.