Characterization of Cu-ZSM-5 Prepared by Solid-State Ion Exchange of H-ZSM-5 with CuCl
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- 作者：Yihua Zhang ; Ian J. Drake ; and Alexis T. Bell
- 刊名：Chemistry of Materials
- 出版年：2006
- 出版时间：May 2, 2006
- 年：2006
- 卷：18
- 期：9
- 页码：2347 - 2356
- 全文大小：237K
- 年卷期：v.18,no.9(May 2, 2006)
- ISSN：1520-5002
文摘
The solid-state ion exchange (SSIE) of H-ZSM-5 by CuCl vapor was investigated with the objectiveof establishing the effects of the temperature at which exchange is carried out on the level of protonexchange for Cu+, the position of the Cu+ cations relative to the zeolite lattice, and the extent of CuClocclusion in the zeolite pores. After SSIE, the resulting Cu-ZSM-5 was characterized by XRD, 27AlMAS NMR, infrared spectroscopy, H2-TPR, and Cu and Cl K-edge X-ray absorption spectroscopy.Evidence was found for clusters of CuCl, in addition to Cu+ cations present at zeolite cation-exchangepositions (ZCu). It was also observed that a part of the occluded CuCl is hydrolyzed to Cu2O duringSSIE. The distribution of ZCu, CuCl, and Cu2O was a strong function of the temperature at which cationexchange was carried out. Virtually complete exchange of all Br
nsted acid protons for Cu+ cations wasachieved at a SSIE temperature of 1023 K. No loss of framework Al was observed at this temperature,and only 10% of the copper introduced into the zeolite was occluded as CuCl. The Cu+ cations exchangedfor Brnsted acid protons are both doubly and triply coordinated to O atoms, with an average Cu-Obond distance of 1.98 Å. Cu EXAFS and Cl XANES indicated that CuCl is occluded in the form of(CuCl)n (n = 2, 3, 4) clusters in the channels and intersections of the zeolite. With a decrease in theamount of occluded CuCl, the amount of Cu2O formed by hydrolysis during SSIE decreases substantially.
nsted acid protons for Cu+ cations wasachieved at a SSIE temperature of 1023 K. No loss of framework Al was observed at this temperature,and only 10% of the copper introduced into the zeolite was occluded as CuCl. The Cu+ cations exchangedfor Brnsted acid protons are both doubly and triply coordinated to O atoms, with an average Cu-Obond distance of 1.98 Å. Cu EXAFS and Cl XANES indicated that CuCl is occluded in the form of(CuCl)n (n = 2, 3, 4) clusters in the channels and intersections of the zeolite. With a decrease in theamount of occluded CuCl, the amount of Cu2O formed by hydrolysis during SSIE decreases substantially.