NO在Cu-ZSM-5上吸附机理的量化研究  

Theoretical study of NO adsorption on Cu-ZSM - 5

作　　者：丁波[1] 孙岳明[1] 张远[1] 

机构地区：[1]东南大学化学化工系,江苏南京210096

出　　处：《计算机与应用化学》2003年第5期583-586,共4页Computers and Applied Chemistry

基　　金：国家重点基础研究专项基金(G1999022209);国家教育项目基金

摘　　要：采用密度泛函理论(DFT)的B3LYP方法,在LanL2DZ基组下,研究了NO在铜离子交换型沸石分子筛催化剂(Cu-ZSM-5)上的吸附情况。首先优化了吸附模型的几何构型参数,然后通过分析Mulliken电荷分布和轨道布居数,进一步探讨了NO在Cu-ZSM-5上吸附成键和活化机理。结果表明:与非负载型Cu相比,Cu-ZSM-5对NO的吸附和活化性能均有提高(其中,负载型Cu^0对N-O键的拉长效应以及吸附能分别为:E=146.2～175.5 kJ·ml^(-1),r=0.065～0.088 A;负载型Cu^+对N-O键的拉长效应以及吸附能分别为:E=105.8～120.8 kJ·mol^(-1),r=0.006～0.012 A)。轨道分析还表明:Cu的3d和4s电子通过dsp杂化参与π~*反馈而导致NO的活化,同时Cu的σ价电子与NO的5σ电子排斥作用的减小是吸附能增加的主要原因。通过相关系列的量化研究,将为氮氧化物NO_x(NO+NO_2)的去除寻找合适的有应用价值的高效催化剂及最佳的去除条件提供理论依据。A systematically theoretical research of NO adsorption on Cu-exchanged zeolite catalyst ( Cu-ZSM - 5) was performed, using Density Functional Theory (DFT) at B3LYP/LanL2DZ level. The equilibrium geometries for adsorption model was optimized, and the mechanism of NO adsorption on Cu-ZSM -5 was studied through analyzing the Mulliken charge and population. It was showed that, compared to Cu, Cu-ZSM - 5 could strengthen the stability of adsorption model and enhance the NO decomposition activity effectively (Cu-ZSM-5: E = 146.2 ~ 175. 5 kJ mol-1 , r = 0. 065 ~ 0. 088 λ;Cu+ -ZSM -5:E = 105.8~120. 8 kJ mol-1 , r = 0.006 ~ 0. 012 A). In addition, the 3d and 4s electron of Cu contribute to the NO decomposition activity by dsp hybrid orbital, and the decrease of the repulsion between σ electron of Cu and 5σ electron of NO was the primary reason to the increase of adsorption energy. To further Quantum Chemical Study would provide theoretical basis for the guidance of seeking particularly valuable catalyst and optimal catalysis conditions.

关 键 词：NO CU-ZSM-5 吸附机理 量化研究 分子筛 密度泛函理论 吸附能 

分 类 号：O613.61[理学—无机化学] O647.3[理学—化学]