Toward predicting the mercury removal by chlorine on the ZnO surface

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• 作者：Lixia Ling^a ; ^b ; Senpeng Zhao^a ; Peide Han^b ; Baojun Wang^c ; ^{wangbaojun@tyut.edu.cn" class="auth_mail} ; Riguang Zhang^c ; Maohong Fan^d
• 关键词：Hg0 removal ; Coal ; Flue gas ; Oxidation mechanism ; Density functional theory
• 刊名：Chemical Engineering Journal
• 出版年：15 May, 2014
• 年：2014
• 卷：244
• 期：Complete
• 页码：364-371
• 全文大小：2125 K

文摘

The density functional theory with the generalized gradient approximation has been used to determine the binding mechanism of Cl₂, HCl and Hg species on the ZnO() surface, and the Hg⁰ oxidation mechanism by Cl₂ (or HCl) on the ZnO surface. Cl₂ and HCl are dissociatively adsorbed on the surface, and Cl atom bonds to two adjacent Zn atoms. Binding energy of Hg⁰ is showing a physisorption mechanism, while HgCl₂ is strongly adsorbed on the surface in the molecularly mode, which indicates that the oxidation of Hg⁰ is necessary for its removal from flue gas. HgCl is not an indispensable intermediate during the Hg⁰ oxidation to form HgCl₂. Three Hg⁰ oxidation mechanisms have been investigated, and the HgCl₂ is easy to be formed via both the Eley-Rideal and Langmuir鈭扝inshelwood mechanisms, while Mars鈭扢aessen mechanism is unfavorable since high activation energy is needed for Hg⁰ reacting with the lattice oxygen of ZnO. The adsorbed H atoms by HCl dissociation inhibit the formation of HgCl₂, and Cl₂ is the primary species being responsible for the Hg⁰ oxidation on the ZnO surface.