中孔型沸石的晶體形狀之研究; Morphogenesis of Shapes in Mesoporous Molecular Sieves

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题名:	中孔型沸石的晶體形狀之研究;Morphogenesis of Shapes in Mesoporous Molecular Sieves
作者:	周孟達;Meng-Ta Chou
贡献者:	化學工程與材料工程研究所
关键词:	晶體形狀;球形;麵條狀;中孔分子篩;HMS;Morphologies;Synthesis;Noodle-like Particles;Spherical Particles;Mesoporous;HMS;Molecular Sieves
日期:	2002-06-17
上传时间:	2009-09-21 12:21:13 (UTC+8)
出版者:	國立中央大學圖書館
摘要:	HMS是利用1o胺界面活性劑（C12H25NH2, DDA）當作模版與中性醇氧矽（TEOS）以氫鍵結合在室溫下所合成出來的中孔分子篩。本研究改變了許多製備上的條件和配方，包括TEOS加入速度、DDA濃度和醇水比例,合成出均一粒徑的球形HMS和麵條狀的HMS。在鑑定樣品的物理性質上，以X光繞射分析（XRD）鑑定其晶相；由氮吸附、脫附分析測定表面積、孔洞大小及孔洞分布；利用熱重損失分析儀（TGA）做熱分析；藉掃描式電子顯微鏡（SEM）觀察外部形態；最後以穿透式電子顯微鏡了解內部結構。當TEOS加入的速度愈快，則HMS顆粒愈小且聚集嚴重，但是組織孔洞體積會增加；反之，當TEOS加入的速度愈慢，所得到的顆粒會變大，但是幾乎沒有組織孔洞體積。在均一粒徑的球形HMS的合成上，隨著DDA的濃度的降低，HMS的孔洞會隨之縮小，且會由小顆粒變成有裂痕的大顆粒，當[DDA]＝0.0159 M時，可以得到均一且無裂痕的HMS球形粒子。HMS球形粒子具有很大的表面積（1012 m2/g）和中孔洞（2 nm）。另外，TEOS加入的速度也會影響球形粒子的大小。麵條狀的HMS是在不含乙醇當共溶劑的條件下所合成出來的，但是大部分仍為小顆粒。這些麵條狀的HMS長度有次微米到數個微米，而直徑約有0.1μm。麵條狀的HMS佔全部樣品的比例並沒有與TEOS的濃度有絕對關係。但在[TEOS]=0.4693 M時，麵條狀的HMS所佔的比例最多；[TEOS]=0.2346 M時，最少；而在[TEOS]=0.0587 M時，發現直徑22μm表面像哈密瓜的HMS球體。 A neutral templating route to mesoporous molecular sieves has been reported by Pinnavaia based on hydrogen bonding interactions and self-assembly between neutral primary amine micelles and neutral inorganic precursors. The effect of cosolvent on the morphology of HMS is still not clear. Hexagonal mesoporous silica (HMS) was prepared at ambient temperature by using dodecylamine (DDA) as the template and tetraethyl orthosilicate (TEOS) as a silica derivative in this study. The properties of HMS were characterized by X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, thermogravimetric analysis, and N2 adsorption/desorption. The morphology of HMS is usually irregular and small particle. To investigate the morphological change of this HMS material, the samples prepared at various TEOS adding rate, solvent compositions and compositions were studied. With decreasing TEOS adding rate, the sizes of HMS particles increase and the textural porosity reduces. With the concentration of DDA reduces, HMS particles become crackled bigger particles from small particles and the pore size reduces from 2.32nm to 1.72 nm. As [DDA]=0.0159 M, the spherical particles of HMS silicas with uniform size and isolated are obtained. Besides, TEOS adding rate also affects the size of the spheroids. The noodle-like structures are prepared in HMS silicas prepared at R/H ratio=0. These noodle-like structures were about 0.1μm in diameter and about submicrometer to several micrometers in length. In a series of HMS silicas synthesized by various [TEOS], the irregular trends indicated that it is required to prepare the samples under non-alcoholic solution to have non-spherical particles. However, some other parameters may also play a role.
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