钛改性对γ-Fe2O3选择催化还原脱硝性能强化机制的分子模拟研究  

Promoting effect of Ti in the Ti-modifiedγ-Fe2O3 catalyst on its performance in the selective catalytic reduction of NO with ammonia,a DFT calculation study

作　　者：周文波 牛胜利[1] 王栋 路春美[1] 韩奎华[1] 李英杰[1] 朱英 ZHOU Wen-bo;NIU Sheng-li;WANG Dong;LU Chun-mei;HAN Kui-hua;LI Ying-jie;ZHU Ying(School of Energy and Power Engineering,Shandong University,Jinan 250061,China;Brook Byers Institute for Sustainable Systems and School of Civil and Environmental Engineering,Georgia Institute of Technology,Atlanta,GA 30332,United States;Advanced Materials Institute,Qilu University of Technology(Shandong Academy of Science),Jinan 250014,China)

机构地区：[1]山东大学能源与动力工程学院,山东济南250061 [2]佐治亚理工学院布鲁克贝尔可持续发展学院,佐治亚亚特兰大30332 [3]齐鲁工业大学(山东省科学院)新材料研究所,山东济南250014

出　　处：《燃料化学学报》2020年第10期1224-1235,I0005,共13页Journal of Fuel Chemistry and Technology

基　　金：国家自然科学基金(51576117,21906090);山东省重大科技创新工程项目(2019JZZY020305)资助。

摘　　要：采用密度泛函理论(DFT)研究了典型过渡金属Ti掺杂改性对γ-Fe2O3选择催化还原(NH3-SCR)脱硝性能强化影响的作用机制。构建了单Ti和双Ti在γ-Fe2O3(001)表面的不同Fe位置的掺杂模型,计算了表面掺杂形成能,探讨了O2、NO和NH3分子在Ti掺杂前后的γ-Fe2O3(001)表面的吸附特性,并进行了反应机理分析。结果表明,单Ti倾向于掺杂在八面体Feoct位,双Ti倾向于两个Feoct位。Ti的掺杂增强了催化剂表面对O2的吸附能力,吸附性能随Ti掺杂量增加而增强。单Ti和双Ti的掺杂都抑制了NO以N端在催化剂表面的吸附。Ti能够强化NH3的吸附,增强了Lewis酸位,有利于SCR反应。Ti的掺杂增大了NO2生成的反应能垒,降低了γ-Fe2O3低温区的SCR反应。Ti的掺杂抑制了NH和N的形成,避免了NH3的过度氧化,提高NH3的利用率,有利于SCR反应,并且抑制了通过E-R机理产生的N2O,具有良好的N2选择性。Ti的掺杂能够改善γ-Fe2O3在NH3-SCR中还原NO的性能。The promoting effect of a typical transition metal Ti in the Ti-modifiedγ-Fe2O3 catalyst on its performance in the selective catalytic reduction(SCR)of NO with ammonia was investigated by density functional theory(DFT)calculation.Various doping models of single Ti and double Ti at different Fe sites on theγ-Fe2O3(001)surface were constructed;the surface doping formation energy was calculated,the adsorption characteristics of O2,NO and NH3 molecules onγ-Fe2O3(001)surface before and after Ti doping were compared,and the reaction mechanism was analyzed.The results illustrate that single Ti atom tends to be doped at octahedral Feoct site,whereas two Ti atoms at two Feoct sites.The adsorption of O2 onto the catalyst surface can be enhanced through the Ti doping;moreover,the enhancement increases with an increase in the doping content of Ti.Both single Ti and double Ti doping inhibit the N-terminal adsorption of NO on the catalyst surface.Ti can enhance the Lewis acid sites and promote the adsorption of NH3,which is beneficial to SCR reaction.The doping of Ti increases the energy barrier of NO2 formation and reduces the SCR reaction ofγ-Fe2O3 at low temperature.The doping of Ti can inhibit the formation of NH and N,avoid the excessive oxidation of NH3,and improve the utilization of NH3,which are beneficial to the SCR reaction by suppressing the N2O produced by the E-R mechanism and enhancing the selectivity to N2.As a result,the Ti doping can significantly improve catalytic performance ofγ-Fe2O3 in the NH3-SCR of NO.

关 键 词：NH3-SCR Γ-FE2O3 钛掺杂 DFT 

分 类 号：TQ534[化学工程—煤化学工程]