Yang Yingju, Liu Jing, Wang Zhen, Miao Sen, Ding Junyan, Yu Yingni, Zhang Jinchuan
State Key Laboratory of Coal Combustion, School of Energy and Power Engineering, Huazhong University of Science and Technology, Wuhan, 430074, China.
State Key Laboratory of Coal Combustion, School of Energy and Power Engineering, Huazhong University of Science and Technology, Wuhan, 430074, China.
J Hazard Mater. 2019 Jul 5;373:660-670. doi: 10.1016/j.jhazmat.2019.03.133. Epub 2019 Apr 1.
RuO-based catalysts have attracted great attention in mercury emission control region due to their outstanding catalytic activity and long-term stability. Quantum chemistry calculation was performed to uncover the atomic-scale reaction mechanism of Hg oxidation by HCl over RuO/TiO catalyst. The results indicate that Hg adsorption on RuO/TiO(110) surface is controlled by a weak chemisorption mechanism. The 5-fold coordinated surface Ru atom is identified as the active center for Hg adsorption. HgCl molecule serves as an intermediate connecting reactant state to product state. The weak interaction between HgCl and catalyst surface is favorable for product desorption. HCl activation is an O-assisted surface reaction process in which HCl is oxidized into active Cl atom for Hg oxidation. The heterolytic cleavage of HCl molecule occurs without noticeable activation energy barrier. Hg oxidation by HCl over RuO/TiO catalyst proceeds through two independent reaction channels. The dominant reaction channel of Hg oxidation is identified as a four-step process. Finally, a complete catalytic cycle that can produce the correct stoichiometry was proposed to understand the heterogeneous reaction mechanism of Hg oxidation over RuO/TiO catalyst. The catalytic cycle consists of HCl activation, mercury oxidation and surface reoxidation. Mercury oxidation is the rate-determining step of the catalytic cycle.
基于RuO的催化剂因其出色的催化活性和长期稳定性，在汞排放控制领域备受关注。进行了量子化学计算，以揭示HCl在RuO/TiO催化剂上氧化汞的原子尺度反应机理。结果表明，Hg在RuO/TiO(110)表面的吸附受弱化学吸附机制控制。五重配位的表面Ru原子被确定为Hg吸附的活性中心。HgCl分子作为连接反应物状态和产物状态的中间体。HgCl与催化剂表面之间的弱相互作用有利于产物解吸。HCl活化是一个O辅助的表面反应过程，其中HCl被氧化成活性Cl原子用于Hg氧化。HCl分子的异裂裂解在没有明显活化能垒的情况下发生。HCl在RuO/TiO催化剂上氧化Hg通过两个独立的反应通道进行。Hg氧化的主要反应通道被确定为一个四步过程。最后，提出了一个能产生正确化学计量比的完整催化循环，以理解RuO/TiO催化剂上Hg氧化的多相反应机理。催化循环包括HCl活化、汞氧化和表面再氧化。汞氧化是催化循环的速率决定步骤。
