Behavior of cesium cation in zeolite Y (FAU, Si/Al = 1.56) and their single-crystal structures, |Cs_75−xNa_x|[Si₁₁₇Al₇₅O₃₈₄]-FAU (x = 35 and 54)

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• 作者：Hu Sik Kim ; Sang June Choi ; Woo Taik Lim
• 关键词：Cesium ; Zeolite Y ; Ion exchange
• 刊名：Journal of Porous Materials
• 出版年：2017
• 出版时间：February 2017
• 年：2017
• 卷：24
• 期：1
• 页码：55-64
• 全文大小：
• 刊物类别：Chemistry and Materials Science
• 刊物主题：Catalysis; Characterization and Evaluation of Materials; Physical Chemistry;
• 出版者：Springer US
• ISSN：1573-4854
• 卷排序：24

文摘

To study the tendency of Cs+ exchange into zeolite Y (Si/Al = 1.56) dependence on Cs+ and Na+ concentration of aqueous solution during exchange, two single-crystals of fully dehydrated, Cs+-and Na+-exchanged zeolites Y were prepared by the flow method using a mixed ion-exchange solution whose CsNO₃:NaNO₃ mol ratios were 1:1 (crystal 1) and 1:100 (crystal 2), respectively, with a total concentration of 0.1 M, followed by vacuum dehydration at 723 K. Their crystals were determined by single-crystal synchrotron X-ray diffraction techniques in the cubic space group Fd\(\overline{ 3}\)m, respectively, and were refined to the final error indices R₁/wR₂ = 0.084/0.248 and 0.088/0.274 for crystals 1 and 2, respectively. In the structure of |Cs₄₀Na₃₅|[Si₁₁₇Al₇₅O₃₈₄]-FAU (crystal 1), 40 Cs+ ions per unit cell occupy five different equipoints; 3, 3, 14, 9, and 11 are at sites I, II′, II, IIIa and IIIb, respectively, whereas, the remaining 35 Na+ ions occupy three different sites: 9, 11, and 15 are at sites I, I′, and II, respectively. In the structure of |Cs₂₁Na₅₄|[Si₁₁₇Al₇₅O₃₈₄]-FAU (crystal 2), 21 Cs + ions per unit cell occupy three equipoints; 4, 6, and 11 are at sites II, IIIa, and IIIb, respectively. The residual 54 Na+ ions per unit cell are found at three different sites; 6, 20 and 28 are at sites I, I′, and II, respectively. The degrees of ion exchange are 53 and 28 % for crystals 1and 2, respectively. This result shows that the degree of Cs+ exchange decreased sharply by decreasing the initial Cs+ concentration and increasing the initial Na+ concentration in given ion-exchange solution.