理想与还原Fe_2O_3[001]表面上汞吸附协同催化CO分解作用（英文）

Synergetic Effect of Mercury Adsorption on the Catalytic Decomposition of CO over Perfect and Reduced Fe_2O_3[001] Surface

煤化学链燃烧必然释放汞,汞与载氧体表面相互作用,影响表界面的氧化还原反应。本文采用密度泛函理论计算,研究汞(Hg0)在理想表面(Fe_2O_3[001])和一系列被还原表面(Fe_2O_(2.75)、Fe_2O_(2.5)、Fe_2O_(2.25)、Fe_2(O1.625)、Fe_2O_(0.875)、Fe_2O_(0.375)和Fe)的吸附,以及Hg0对Fe_2O_(1.625)、Fe_2O_(0.875)、Fe_2O_(0.375)和Fe等表面催化CO分解反应的协同作用机理。Hg0物理吸附在理想Fe_2O_3[001]表面。随着Fe_2O_3[001]表面不断被还原,Hg0发生化学吸附。Hg0吸附降低了CO与Fe_2O_3、Fe_2O_(2.75)、Fe_2O_(2.5)和Fe_2O_(2.25)等表面之间的相互作用,抑制O传递氧化CO为CO_2的反应;载氧体进一步还原过程中,Hg0吸附促进了CO与Fe_2O_(1.625)、Fe_2O_(0.875)、Fe_2O_(0.375)及Fe等表面之间的相互作用,进而促进了表面对CO的催化分解反应,加速了载氧体表面的积碳,降低了化学链燃烧效率。因此,合理控制载氧体的还原程度既可以减弱Hg0的吸附,也可以抑制积碳的形成,这对化学链燃烧的操作优化至关重要。

Mercury emission from coal during chemical-looping combustion （CLC） is an inevitable process, which can lead to adverse interactions with the surface of the oxygen carrier, thereby affecting the interfacial redox reactions. Density functional theory calculations were performed to investigate the mechanism of elemental mercury （Hg0） adsorption and the synergetic effect of Hg0 on the catalytic decomposition of CO over a perfect surface （Fe2O3[001]）, as well as a series of reduced surfaces （Fe2O2.75, Fe2O2.5 Fe2O2.25 Fe2O1.625 Fe2O0.875, Fe2O0.375 and Fe） during a deep CLC process. In this study, Hg0 was physically adsorbed on to a perfect Fe2O3 surface, and then chemically adsorbed on to a series of reduced surfaces. The adsorption of Hg0 inhibited the formation of meaningful interactions between CO and Fe2O3 [Fe2O2.75, Fe2O2.5 and Fe2O2.25] and hindered the efficient transport of oxygen to oxidize CO into CO2. In contrast, this process promoted the interactions between CO and Fe201.625 [Fe2O0.875, Fe2O0.375, and Fe], favoring the catalytic decomposition of CO on these surfaces, which accelerated the carbon deposit reducing CLC efficiency. Rationally controlling the reduction degree of the oxygen carrier could therefore be used to either decrease the adsorption of Hg0 or depress the deposition of carbon, which are both crucial for the optimization of CLC processes.