Yang Yingju, Liu Jing, Ding Junyan, Yu Yingni, Zhang Junying
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. 2022 Feb 15;424(Pt B):127556. doi: 10.1016/j.jhazmat.2021.127556. Epub 2021 Oct 20.
CuFeO is regarded as a promising candidate of catalyst for Hg oxidation in industrial flue gas. However, the microcosmic reaction mechanism governing mercury oxidation on CuFeO remains elusive. Herein, experiments and quantum chemistry calculations were conducted for understanding the chemical reaction mechanism of oxygen-assisted mercury oxidation on CuFeO. CuFeO shows the optimal catalytic activity towards mercury oxidation at 150 ºC. The reactivity difference of different lattice oxygen species is associated with its atomic coordination environment. The lattice oxygen coordinating with two octahedral Cu atoms and a tetrahedral Fe atom shows higher catalytic activity towards mercury oxidation than other lattice oxygen atoms. The inverse spinel structure of CuFeO is favorable for O activation due to the Jahn-Teller effect, thereby promoting mercury oxidation. O molecule preferably adsorbs on iron active site and dissociates into active oxygen species. Hg oxidation is a three-step reaction process: Hg adsorption, Hg(ads) → HgO(ads), and HgO desorption. The energy barrier of mercury oxidation by chemisorbed oxygen is lower than that of mercury oxidation by lattice oxygen. The chemisorbed oxygen preserves higher reactivity towards mercury oxidation than lattice oxygen. Hg(ads) → HgO(ads) is the rate-determining step of mercury oxidation by chemisorbed oxygen because of the higher energy barrier of 116.94 kJ/mol. This work could provide the theoretical guidance for the diversified structure design of highly-efficient catalysts used for elemental mercury oxidation.
CuFeO被认为是工业烟气中汞氧化的一种有前景的催化剂候选物。然而，CuFeO上汞氧化的微观反应机理仍不清楚。在此，进行了实验和量子化学计算以了解CuFeO上氧辅助汞氧化的化学反应机理。CuFeO在150 ºC时对汞氧化表现出最佳催化活性。不同晶格氧物种的反应活性差异与其原子配位环境有关。与两个八面体Cu原子和一个四面体Fe原子配位的晶格氧对汞氧化的催化活性高于其他晶格氧原子。由于 Jahn-Teller 效应，CuFeO的反尖晶石结构有利于O的活化，从而促进汞氧化。O分子优先吸附在铁活性位点并分解为活性氧物种。汞氧化是一个三步反应过程：Hg吸附、Hg(ads) → HgO(ads)和HgO解吸。化学吸附氧氧化汞的能垒低于晶格氧氧化汞的能垒。化学吸附氧对汞氧化的反应活性高于晶格氧。由于116.94 kJ/mol的较高能垒，Hg(ads) → HgO(ads)是化学吸附氧氧化汞的速率决定步骤。这项工作可为用于元素汞氧化的高效催化剂的多样化结构设计提供理论指导。
