Hierarchically Structure-Directing Effect of Multi-Ammonium Surfactants for the Generation of MFI Zeolite Nanosheets
Hierarchically Structure-Directing Effect of Multi-Ammonium Surfactants for the Generation of MFI Zeolite Nanosheets
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DOI：
10.1021/cm201709q
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发表时间：
2011-12-13
影响因子：
8.6
通讯作者：
Ryoo, Ryong
中科院分区：
文献类型：
--
作者：
Park, Woojin;Yu, Doae;Ryoo, Ryong
多季铵盐表面活性剂可与硅酸阴离子协同组装生成MFI分子筛纳米片，其中铵盐作为微孔分子筛的结构导向剂，而表面活性剂尾部组装成层状胶束。用尾- n (+)(CH(3))(2)-(间隔- n (+)R(2)}(n-1)-R*的公式研究了不同分子的两能级结构定向效应。这里，n随1-4变化。尾部选择在线性烷基链(C（m)H(2m+1), m = 6-22）之间。间隔是一个烷基桥(- c （l)H(2i)-, i = 3,6和8）。R和R*为烷基(C（i)H(2j+1), j = 1-6）。结果表明，表面活性剂分子除了具有两亲性和胶束堆积能力外，还必须具有至少2个合适的铵基，才能形成沸石结构。此外，纳米片的厚度可以根据铵基的数量来增加和定制。详细考虑模板分子特征的影响可能有助于设计用于纳米型沸石的分层结构导向表面活性剂。
Multi-quaternary ammonium surfactants can assemble co-operatively with silicate anions to generate MFI zeolite nanosheets, where the ammonium acts as a structure-directing agent for the microporous zeolite, while the surfactant tails assemble into a lamellar micelle. The two-level structure-directing effects have been investigated for various molecules with the formula of tail-N(+)(CH(3))(2)-(spacer-N(+)R(2)}(n-1)-R*. Here, n is varied over 1-4. The tail is selected among linear alkyl chains (C(m)H(2m+1), m = 6-22). The spacer is an alkylene bridge (-C(l)H(2i)-, i = 3, 6 and 8). R and R* are alkyl groups (C(i)H(2j+1), j = 1-6). The result highlights that the surfactant molecule should be equipped with at least 2 suitable ammonium groups for the formation of zeolite structure, in addition to the amphiphilic nature and micelle packing ability. Moreover, the thickness of the nanosheets can be increased and tailored according to the number of the ammonium groups. Detailed consideration of the effects of template molecular features may be useful for the design of hierarchically structure-directing surfactants for nanomorphic zeolites.