Mechanism of Heterogeneous Mercury Oxidation by HBr over V2O5/TiO2 Catalyst

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• 作者：Zhen Wang ; Jing Liu ; Bingkai Zhang ; Yingju Yang ; Zhen Zhang ; Sen Miao
• 刊名：Environmental Science & Technology
• 出版年：2016
• 出版时间：May 17, 2016
• 年：2016
• 卷：50
• 期：10
• 页码：5398-5404
• 全文大小：451K
• 年卷期：0
• ISSN：1520-5851

文摘

Catalytic oxidation of elemental mercury (Hg⁰) through a selective catalytic reduction (SCR) system is a promising method to reduce mercury emissions from coal-burning power plants. The density functional theory (DFT) and periodic slab models were used to study the reaction mechanism of Hg⁰ oxidation by HBr on V₂O₅/TiO₂ SCR catalyst surface. The interaction mechanisms of Hg⁰, HBr, HgBr, and HgBr₂ on V₂O₅/TiO₂(001) were investigated. The oxidation reaction energy profiles and the corresponding geometries of the intermediates, final states, and transition states were researched. The results indicate that Hg⁰ and HgBr₂ are weakly adsorbed on the oxygen sites of the V₂O₅/TiO₂(001) surface with physisorption. HgBr is chemically adsorbed on the surface. HBr is dissociatively adsorbed on the surface with an energy barrier of 85.59 kJ/mol. The reaction of Hg⁰ oxidation by HBr follows the Eley–Rideal mechanism: Hg⁰ interacts with a surface Br from HBr dissociation to form HgBr, and surface HgBr further interacts with HBr to form HgBr₂, last HgBr₂ desorbs from the surface. Comparing the energy pathway of Hg⁰ oxidation over V₂O₅/TiO₂(001) surface by HBr to that of HCl, it is found that the dissociation energy barrier of HBr is lower than that of HCl, the formation and desorption energy barriers of HgBr₂ are also lower than that of HgCl₂, which explains why HBr is much more effective than HCl in promoting Hg⁰ oxidation.