2 NEW 3-DIMENSIONAL 12-RING ZEOLITE FRAMEWORKS OF WHICH ZEOLITE BETA IS A DISORDERED INTERGROWTH
2 NEW 3-DIMENSIONAL 12-RING ZEOLITE FRAMEWORKS OF WHICH ZEOLITE BETA IS A DISORDERED INTERGROWTH
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DOI：
10.1038/332249a0
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发表时间：
1988-03-17
期刊：
影响因子：
64.8
通讯作者：
NEWSAM, JM
中科院分区：
文献类型：
--
作者：
TREACY, MMJ;NEWSAM, JM
19671年首次描述的β沸石是一种活性催化剂和有用的吸附剂。吸附和催化数据表明，该沸石可能具有三维12环孔系统。这样的孔系统表明类似于八面沸石骨架材料的技术潜力，但到目前为止，这种沸石的结构还没有确定。粉末X射线衍射图案包括尖锐和宽的特征，指示广泛的断层结构。在这里，我们通过高分辨率电子显微镜，电子衍射和计算机辅助建模来确定β沸石的结构。沸石是两种不同但密切相关的结构的共生混合物。两者都是由相同的层中排列的第三级结构单元构成的，并且都具有三维12环孔系统。一个末端成员，多晶型物A，形成对映体对，具有对称性P4122和P4322，其中a = 12.4 π和c = 26.5 π。多聚体B，其中层的堆叠在旋向上交替，是非手性的，空间群为P1 <$，并且α <$b= 12.4 <$，c= 14.5 <$，α <$β= 73°，γ <$90 °。β沸石材料中堆垛层错的高密度出现是因为连续层必须以左手或右手方式互连，并且两种连接模式以几乎相等的概率发生。
Zeolite beta, first described in 19671, is an active catalyst and a useful sorbent1. Sorption1,2and catalytic data3,4suggest that the zeolite could possess a three-dimensional 12-ring pore system. Such a pore system suggests technological potential similar to that of faujasite framework materials, but until now the structure of this zeolite has eluded determination. Powder X-ray diffraction patterns comprise both sharp and broad features, indicative of an extensively faulted structure. Here we determine the structure of zeolite beta by high-resolution electron microscopy, electron diffraction and computer-assisted modelling. The zeolite is an intergrown hybrid of two distinct but closely related structures. Both are constructed from the same centrosymmetrlcal tertiary building unit arranged in layers, and both possess three-dimensional 12-ring pore systems. One end member, polymorph A, forms an enantiomorphic pair, with symmetries P4122 and P4322, witha= 12.4 Å andc= 26.5 Å. Polymorpb B, in which the stacking of layers alternates in handedness, is achiral with space group P1 ¯, anda≃b= 12.4 Å,c= 14.5 Å,α≃β= 73°,γ≃ 90°. The high density of stacking faults in zeolite beta materials arises because successive layers must interconnect in either a left- or a right-handed fashion, and both modes of linkage occur with almost equal probability.