Different copper species as active sites for NH3-SCR reaction over Cu-SAPO-34 catalyst and reaction pathways: A periodic DFT study
Different copper species as active sites for NH3-SCR reaction over Cu-SAPO-34 catalyst and reaction pathways: A periodic DFT study
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不同铜物种作为 Cu-SAPO-34 催化剂上 NH3-SCR 反应的活性位点和反应途径：定期 DFT 研究
DOI：
10.1016/j.micromeso.2018.01.034
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发表时间：
2018-08
影响因子：
5.2
通讯作者：
Li Zhang
中科院分区：
文献类型：
--
作者：
Guangpeng Yang;Jingyu Ran;Xuesen Du;Xiangmin Wang;Yanrong Chen;Li Zhang
Cu-SAPO-34 SCR催化剂因具有较高的NH3-SCR活性和N2选择性而备受关注。采用密度泛函理论（DFT）研究了Cu-SAPO-34催化剂中不同铜物种作为SCR反应活性中心的情况，主要集中在六元环（6 MR）和八元环（8 MR）中的铜中心.计算了各种Cu物种的相对能量，并组织成相图，以研究Cu物种的稳定性。DFT计算结果表明，NH 3在8 MR中的吸附能最高，而NH 3在8 MR中几乎不能解离，说明孤立的Cu离子会阻碍NH 3-SCR反应的进行。然而，额外的Cu离子和O原子在8 MR有效地降低解离能垒。这些结果表明，孤立的Cu ~（2+）是6 MR的活性中心，[Cu-O-Cu]~（2+）是8 MR的活性中心。此外，NH 3在Cu 2+和[Cu-O-Cu]2+上的解离是6 MR和8 MR反应的关键步骤。
Cu-SAPO-34 SCR catalyst has drawn much attention because of its high NH3-SCR activity and N2selectivity. Different copper species as active sites for SCR reaction in Cu-SAPO-34 catalyst were studied by DFT calculations, primarily focusing on copper sites in six-membered rings (6 MR) and eight-membered rings (8 MR). The relative energies of various Cu species were calculated and organized as phase diagrams to investigate the stabilities of Cu species. The diagrams show that Cu2+can exist in 6 MR, and [Cu-O-Cu]2+tends to form in 8 MR.The DFT results show that the adsorption energies for NH3on Cu+and Cu2+in 8 MR are the highest and but NH3can hardly dissociate in 8 MR, which indicate isolated Cu ions located in 8 MR will hinder the NH3-SCR reaction. However, the additional Cu ion and O atom in 8 MR effectively reduces the dissociation energy barrier. These results indicate that isolated Cu2+is the active site in 6 MR, and [Cu-O-Cu]2+is the active site in 8 MR. Besides, the NH3dissociation on Cu2+and [Cu-O-Cu]2+are the key steps for the reactions in 6 MR and 8 MR.
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