Disproportionation of associated Cu2+ sites in Cu-ZSM-5 to Cu+ and Cu3+ and FTIR detection of Cu3+(NO)x (x = 1, 2) species
Disproportionation of associated Cu2+ sites in Cu-ZSM-5 to Cu+ and Cu3+ and FTIR detection of Cu3+(NO)x (x = 1, 2) species
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DOI：
10.1016/j.jcat.2013.10.018
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发表时间：
2014
影响因子：
7.3
通讯作者：
M. Tortorelli;K. Chakarova;L. Lisi;K. Hadjiivanov
中科院分区：
文献类型：
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作者：
M. Tortorelli;K. Chakarova;L. Lisi;K. Hadjiivanov
NO在过交换的Cu-ZSM-5（SiO2/Al 2 O3 = 23）上的吸附导致了Cu ~（2+）和Cu ~+的亚硝酰基物种的形成。此外，在1960和1947 cm−1处的IR谱带检测到两种Cu 3 +-NO单亚硝基化合物。Cu ~（3+）的生成是由于Cu ~（2+）离子从缔合位Cu ~（2+）-O-Cu ~（2+）→ Cu ~（2+）-O-Cu ~（3+）的解离作用。用CO封闭预先存在的Cu+位点的样品证明了NO吸附过程中Cu+离子的形成。在NO存在下，Cu 3 +-NO复合物被还原为Cu+-NO和Cu 2 +-NO。在低温下，Cu 3 +-NO单亚硝基能够接受第二个NO配体，从而形成Cu 3+（NO）2物种（1915和1863-53 cm-1）。NO-15 NO同位素混合物吸附证明了二亚硝酰基结构。这些新发现支持了Cu+离子是NO分解的活性中心和二亚硝酰基物种是反应中间体的假设。
Adsorption of NO on an over-exchanged Cu-ZSM-5 sample (SiO2/Al2O3= 23) leads to formation of the well-known nitrosyl species of Cu2+and Cu+. In addition, two kinds of Cu3+–NO mononitrosyls are detected by IR bands at 1960 and 1947 cm−1. The Cu3+species are produced as a result of disproportionation of Cu2+ions from associated sites: Cu2+–O–Cu2+→ Cu+–O–Cu3+. The formation of Cu+ions during NO adsorption is proven with a sample where the preexisting Cu+sites were blocked by CO. In the presence of NO, the Cu3+–NO complexes are reduced to Cu+–NO and Cu2+–NO. At low temperature, the Cu3+–NO mononitrosyls are able to accept a second NO ligand forming thus Cu3+(NO)2species (1915 and 1863–53 cm−1). The dinitrosyl structures are proven by adsorption of NO–15NO isotopic mixture. The new findings support the hypothesis that Cu+ions are active sites in NO decomposition and the dinitrosyl species, reaction intermediates.