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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。
The B3LYP method of density functional theory (DFT) was used to study the adsorption of NO on Cu-ZSM-5 zeolites under the LanL2DZ basis set. Firstly, the geometrical parameters of the adsorption model were optimized. Then, the adsorption and activation mechanism of NO on Cu-ZSM-5 were further discussed by analyzing the Mulliken charge distribution and orbital population. The results showed that the adsorption and activation properties of Cu on ZSM-5 were improved compared with unsupported Cu (the elongation effect and adsorption energy of Cu-0 on NO bond were E = 146.2 ~ 175.5 kJ · ml -1, r = 0.065 ~ 0.088 A; the elongation effect and adsorption energy of supported Cu ~ + on NO bond were: E = 105.8-120.8 kJ · mol -1, r = 0.006 to 0.012 A). The orbital analysis also shows that the 3d and 4s electrons of Cu participate in π ~ * feedback through dsp hybridization, resulting in the activation of NO. The decrease of 5σ electron excitations of Cu valence electrons and NO is the main reason for the increase of adsorption energy. Through the related quantitative research, this paper will provide a theoretical basis for the search of suitable and efficient catalysts and removal conditions for the removal of nitrogen oxides NO_x (NO + NO_2).