Crystal Structures of Fully La3+-Exchanged Zeolite X: an Intrazeolitic La2O3 Continuum, Hexagonal Planar and Trigonally Monocapped Trigonal Prismatic Coordination
Crystal Structures of Fully La3+-Exchanged Zeolite X: an Intrazeolitic La2O3 Continuum, Hexagonal Planar and Trigonally Monocapped Trigonal Prismatic Coordination
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DOI：
10.1021/jp992153i
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发表时间：
2000-02
影响因子：
3.3
通讯作者：
Hyun Sook Park and;K. Seff
中科院分区：
文献类型：
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作者：
Hyun Sook Park and;K. Seff
钠沸石X的三个单晶在90 °C下从水溶液（在22 °C下分别为pH = 7.45、7.45和6.89）中完全交换La 3+。一种在400 °C下真空脱水（晶体1），另一种在22 °C下真空脱水（晶体2），第三种保持完全水合（晶体3）。它们在22 °C下的结构通过单晶X射线晶体学确定，分别在立方空间群Fd 3 m（a = 24.999（4）和25.059（4）A）和Fd 3（a = 25.154（3）A）中。它们被细化为最终误差指数R1 = 0.076、0.091和0.078，分别具有471、374和725个反射，其中Fo > 4σ（Fo）。在这三种结构中发现的La ~（3+）、H ~（3 O+）和OH ~-离子的数目分别为每晶胞约38、0、18; 38、28、50;和33、16、24。晶体1也有48个非骨架氧离子和92个H+离子每晶胞。在所有情况下都发生了过度变化。在晶体1中，每个晶胞中有32个La 3+离子填充位置I '，其余6个在12环中心（位置V）。这六个坐标中的每一个都是三...
Three single crystals of sodium zeolite X were fully La3+-exchanged at 90 °C from aqueous solution (pH = 7.45, 7.45, and 6.89 at 22 °C, respectively). One was vacuum dehydrated at 400 °C (crystal 1), another at 22 °C (crystal 2), and the third remained fully hydrated (crystal 3). Their structures at 22 °C were determined by single-crystal X-ray crystallography in the cubic space groups Fd3m (a = 24.999(4) and 25.059(4) A) and Fd3 (a = 25.154 (3) A), respectively. They were refined to the final error indices R1 = 0.076, 0.091, and 0.078 with 471, 374, and 725 reflections, respectively, for which Fo > 4σ(Fo). The number of La3+, H3O+, and OH- ions found in the three structures are about 38, 0, 18; 38, 28, 50; and 33, 16, 24, respectively, per unit cell. Crystal 1 also has 48 nonframework oxide ions and 92 H+ ions per unit cell. In all cases overexchange occurred. In crystal 1, 32 La3+ ions per unit cell fill site I‘, with the remaining six at 12-ring centers (site V). Each of these six coordinates to thre...