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首页> 外文期刊>The journal of physical chemistry, B. Condensed matter, materials, surfaces, interfaces & biophysical >Crystal Structure of a Benzene Sorption Complex of Dehydrated Fully Ca~(2+)-Exchanged Zeolite X
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Crystal Structure of a Benzene Sorption Complex of Dehydrated Fully Ca~(2+)-Exchanged Zeolite X

机译：完全脱水的Ca〜（2+）交换沸石X的苯吸附配合物的晶体结构

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摘要

The crystal structure of a benzene sorption complex of fully dehydrated Ca~(2+)-exchanged zeolite X, Ca_(46)Si_(100)Al_(92)O_(384) · 28C_6H_6 (a = 24.953(6) A), has been determined by single-crystal X-ray diffraction techniques in the cubic space group Fd3 at 21 ℃. The crystal was prepared by ion exchange in a flowing stream of 0.05 M aqueous Ca(NO_3)_2 for 3 days, followed by dehydration at 400 ℃ and 2 * 10~(-6) Torr for 2 days, followed by exposure to about 48 Torr of benzene vapor at 16 ℃. The structure was determined in this atmosphere and refined to the final error indices R_1 = 0.051 and R_w = 0.049 with 358 reflections for which I > 3σ(I). Filling site I (at the centers of the double six-rings), 16 octahedrally coordinated Ca~(2+) ions (Ca-O = 2.399(7) A) are found per unit cell. The remaining 30 Ca~(2+) ions are found at two nonequivalent sites II (in the supercages) with occupancies of 8 and 22 ions. Each of these Ca~(2+) ions coordinates to three framework oxygens, either at 2.270(10) or 2.318(7) A, respectively, and extends either 0.24 or 0.55 A, respectively, into the supercage from the plane of the three oxygens to which it is bound. The benzene molecules are found at two distinct sites within the supercages. Twenty-two benzenes lie on 3-fold axes in the large cavities, where they interact facially with the latter 22 site-II Ca~(2+) ions (Ca~(2+)-benzene center = 2.75 A; occupancy = 6 molecules/16 sites. Each hydrogen of these six benzenes is ca. 3.0 A from three 12-ring oxygens.
机译：完全脱水的Ca〜（2+）交换沸石X，Ca_（46）Si_（100）Al_（92）O_（384）·28C_6H_6（a = 24.953（6）A）的苯吸附复合物的晶体结构，用单晶X射线衍射技术测定了立方空间群Fd3在21℃的温度。通过在0.05 M Ca（NO_3）_2水溶液中进行3天离子交换，然后在400℃和2 * 10〜（-6）Torr下脱水2天，然后暴露于约48中，来制备晶体。在16℃下产生苯蒸气的托。在这种气氛下确定结构，并将其精炼到最终误差指数R_1 = 0.051和R_w = 0.049，并进行358次反射，其中I>3σ（I）。填充位点I（在双六环的中心）每个单元格中找到16个八面体配位的Ca〜（2+）离子（Ca-O = 2.399（7）A）。剩余的30个Ca〜（2+）离子存在于两个非等价位点II（在超笼中），占据8和22个离子。这些Ca〜（2+）离子分别与三个构架氧配位，分别在2.270（10）或2.318（7）A，并分别从这三个构架的平面延伸0.24或0.55 A进入超笼它所结合的氧。在超笼内的两个不同位置发现了苯分子。 22个苯位于大腔中的3倍轴上，在那里它们与后22个II位Ca〜（2+）离子（Ca〜（2 +）-苯中心= 2.75 A;占用率= 6）在表面上相互作用分子/ 16个位点，这六个苯中的每个氢均来自三个12环氧，约为3.0A。

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