New Insight into Cation Relocations within the Pores of Zeolite Rho: In Situ Synchrotron X-Ray and Neutron Powder Diffraction Studies of Pb- and Cd-Exchanged Rho
New Insight into Cation Relocations within the Pores of Zeolite Rho: In Situ Synchrotron X-Ray and Neutron Powder Diffraction Studies of Pb- and Cd-Exchanged Rho
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对 Rho 沸石孔内阳离子迁移的新见解：Pb 和 Cd 交换 Rho 的原位同步加速器 X 射线和中子粉末衍射研究
DOI：
10.1021/jp0100349
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发表时间：
2001
期刊：
影响因子：
--
通讯作者：
J. Z. Larese
中科院分区：
文献类型：
--
作者：
Yongjae Lee;B. Reisner;J. Hanson;G. A. Jones;J. Parise;D. Corbin;B. Toby;A. Freitag;J. Z. Larese
在加热时，交换到沸石RHO中的某些阳离子在其孔内的位置经历大的位移。在这些材料中的几种中，观察到负热膨胀与这些阳离子迁移有关。而不是纯粹的温度驱动的影响，在以前的报告中推测，结合原位时间分辨同步辐射X射线和中子粉末衍射研究表明，在铅和镉交换沸石rho中观察到的阳离子迁移和框架扭曲介导的水的存在下，在特定的网站在RHO的孔隙。使用这些数据进行Rietveld精修表明，初始晶胞收缩（50 °C ≤ T ≤ 100 °C）是由于rho α笼中的未结合水的损失。双八环（D8R）结构单元中的水分子在这一步骤后仍然存在，与骨架外阳离子结合。然后随着水分子逐渐被去除，框架收缩（200 °C ≤ T ≤ 400 °C）。在此期间，外框架C...
Upon heating, certain cations exchanged into zeolite RHO undergo large shifts in their positions within the pores. In several of these materials, negative thermal expansion is observed in conjunction with these cation relocations. Rather than being the purely temperature-driven effects presumed in previous reports, a combination of in situ time-resolved synchrotron X-ray and neutron powder diffraction studies indicates that the cation relocations and framework distortions observed in Pb- and Cd-exchanged zeolite rho are mediated by the presence of water in specific sites in the pores of RHO. Rietveld refinements using these data reveal that the initial unit cell contraction (50 °C ≤ T ≤ 100 °C) is due to the loss of unbound water in the α-cages of rho. Water molecules in the double eight-ring (D8R) building units persist after this step, bound to the extraframework cations. The framework then contracts as water molecules are gradually removed (200 °C ≤ T ≤ 400 °C). During this period, the extraframework c...