Methodology for synthesizing crystalline metallosilicates with expanded pore windows through molecular alkoxysilylation of zeolitic lamellar precursors.
Methodology for synthesizing crystalline metallosilicates with expanded pore windows through molecular alkoxysilylation of zeolitic lamellar precursors.
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DOI：
10.1021/ja0758739
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发表时间：
2008-06
影响因子：
15
通讯作者：
Peng Wu;Juanfang Ruan;Lingling Wang;Leilei L Wu;Yong Wang;Yue M. Liu;W. Fan;M. He;O. Terasaki-O.
中科院分区：
文献类型：
--
作者：
Peng Wu;Juanfang Ruan;Lingling Wang;Leilei L Wu;Yong Wang;Yue M. Liu;W. Fan;M. He;O. Terasaki-O.
用二乙氧基二甲基硅烷对MWW、FER、CDO和MCM-47等各种拓扑结构的沸石片层前体进行烷氧基硅烷化后改性，目的是构建层间孔径扩大的新晶体结构。用XRD、IR、（13）C和（29）Si MAS NMR、ICP、SEM、HRTEM、元素分析和N2吸附等技术研究了硅烷基化反应过程及产物的晶体结构和孔结构。与直接煅烧层状前体后形成已知的三维沸石结构相反，甲硅烷基化导致具有开放孔的新的晶体结构，如通过XRD图案中的层相关衍射向低角度区域的移位和通过HRTEM图像发现的增大的层间孔所证明的。通过优化处理条件，特别是硅烷试剂的用量，实现了最大限度的均匀硅化，保证了层间膨胀沸石的相纯度。在823 K下煅烧或在水中回流1至2周后，膨胀的结构被很好地保留，表明高的热稳定性以及水热稳定性。由MWW拓扑结构的金属硅酸盐前驱体制备的层间扩展沸石在大分子的氧化还原和固体酸催化反应中表现出比具有常规MWW拓扑结构的对应物更高的催化活性。
Postalkoxysilylation with diethoxydimethylsilane has been carried out on the zeolitic lamellar precursors of various topologies such as MWW, FER, CDO and MCM-47 aiming to construct new crystalline structures with expanded pore apertures between the layers. The silylation process and the crystalline and pore structures of the resulting materials have been investigated with the techniques of XRD, IR, (13)C and (29)Si MAS NMR, ICP, SEM, HRTEM, elemental analyses, and N 2 adsorption. In contrast to forming known three-dimensional zeolite structures after direct calcination of the lamellar precursors, the silylation led to new crystalline structures with opener pores, as evidenced by the shift of layer-related diffractions to the lower-angle region in XRD patterns and the enlarged interlayer pores found by HRTEM images. After optimizing the treatment conditions, particularly the amount of silane agent, a maximum and homogeneous silylation was realized, which guaranteed the phase purity in interlayer expanded zeolites. The expanded structures were well preserved after calcination at 823 K or reflux in water for 1 to 2 weeks, indicating a high thermal stability and also a hydrothermal stability. The interlayer expanded zeolites prepared from the metallosilicate precursors of MWW topology exhibited higher catalytic activities in the redox and solid acid-catalyzed reactions of bulky molecules than that of their counterparts with conventional MWW topology.