Anomalous valence changes and specific dinitrogen adsorption features of copper ion exchanged in ZSM-5 zeolite prepared from an aqueous solution of [Cu(NH3)2]+
Anomalous valence changes and specific dinitrogen adsorption features of copper ion exchanged in ZSM-5 zeolite prepared from an aqueous solution of [Cu(NH3)2]+
复制标题
[Cu(NH3)2]水溶液制备的ZSM-5沸石中铜离子交换的异常价态变化和特定氮吸附特征
DOI：
10.1039/b316172m
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发表时间：
2004
影响因子：
3.3
通讯作者：
M. Nagao
中科院分区：
文献类型：
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作者：
Y. Kuroda;Atsushi Itadani;R. Kumashiro;T. Fujimoto;M. Nagao
采用二胺-铜(I)离子[Cu(NH3)2]+水溶液，将一价铜离子直接与ZSM-5型沸石进行离子交换，制备出仅含一价铜离子的铜离子交换ZSM-5型沸石，并考察了一价铜离子对沸石吸附二氮（N2）性能的影响。奇怪的是，ZSM-5中交换的单价铜离子在473 K左右的疏散过程中发生了再氧化。利用x射线吸收精细结构（XAFS）、红外光谱和光电发射光谱等光谱技术，以及吸附等温线和吸附热的测量，研究了交换铜离子在室温下与N2分子相互作用过程中价态和结构的变化。根据x射线吸收近边结构（XANES）和扩展x射线吸收精细结构（EXAFS）分析，发现ZSM-5沸石中交换的Cu+在473 K真空热处理后，被水氧化形成具有cuo样结构的二价Cu+。在高于673 K的温度下进一步热处理，导致二价物质还原为一价物质，即使在室温下也表现出对N2的明显吸附特征。XANES和光电发射数据清楚地表明，873 k处理的CuZSM-5样品中的Cu+具有晶格氧原子的三坐标结构，并在室温下与N2分子发生强烈的相互作用。通过吸附热和红外数据验证了与N2的强相互作用：初始吸附能为85 kJ mol−1，吸收带在2295 cm−1处。该体系的一个突出特点是，在300 K下，一些被吸附的物质在疏散后仍然存在，这表明N2与三坐标铜离子之间存在很强的相互作用。
Direct ion-exchange of monovalent copper ions into a ZSM-5-type zeolite was carried out using an aqueous solution of diammine–copper(I) ions, [Cu(NH3)2]+, to prepare a copper ion-exchanged ZSM-5 zeolite including only monovalent copper ions, and the effect of monovalent copper ions on the zeolite's adsorption properties for dinitrogen (N2) was examined. Strangely enough, the reoxidation of monovalent copper-ion exchanged in ZSM-5 took place in the evacuation process at around 473 K. The changes in valence and structure of the exchanged copper-ions during the evacuation process and the interaction with N2 molecules at room temperature have been investigated by using spectroscopic techniques such as X-ray absorption fine structure (XAFS), IR and photoemission spectroscopy, as well as by measurements of adsorption isotherms and adsorption heats. On the basis of X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) analyses, it has become apparent that the Cu+ species exchanged in ZSM-5 zeolite is oxidized by water to form a divalent species having a CuO-like structure through heat-treatment in vacuo at 473 K. Further heat-treatment at temperatures above 673 K caused a reduction of the divalent species to a monovalent one that exhibits a pronounced adsorption feature for N2 even at room temperature. XANES and photoemission data clearly indicated that the Cu+ species in an 873 K-treated CuZSM-5 sample has a three-coordinate structure with lattice oxygen atoms and interacts strongly with an N2 molecule at room temperature. The strong interaction with N2 was also verified through the adsorption heat and IR data: an initial adsorption energy of 85 kJ mol−1 and an absorption band at 2295 cm−1. A prominent feature of this system is that some of the adsorbed species survives after evacuation at 300 K, indicative of a strong interaction between N2 and the three-coordinate copper ion.
影响因子：
--
作者：
IWAMOTO, M;YAHIRO, H;KAGAWA, S
通讯作者：
KAGAWA, S