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具有纳米质点性质的MFI型硅沸石微细晶粒的合成及表征(英)

The preparation and characterization of siliceous MFI type zeolite fine crystals with nanoparticle properties
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摘要 分别以白炭黑(Ⅰ)和硅溶胶(Ⅱ)为硅源,在(TPA)2O-Na2O-SiO2-H2O体系(TPA为四丙基铵)中,反应温度为60℃,合成了高结晶度纯硅沸石.用扫描电子显微镜(SEM)法测得的晶粒大小分别为0.20μm(Ⅰ)和0.45μm(Ⅱ);用粉末X射线衍射(XRD)线宽法测得的晶粒大小为0.02μm.与高温(180℃)合成的硅沸石样品相比较,低温合成的微细晶粒硅沸石样品已具备纳米级材料的若干特性.微细晶粒硅沸石的正己烷吸附量和比表面都非常大.XRD谱,红外吸收光谱(FT-IR),29Si魔角固体核磁共振(29SiMASNMR)和热重分析(TG/DTG/DTA)的研究证明,微细晶粒硅沸石的结构破坏温度和单斜/正交对称性相转变温度明显地比高温合成的硅沸石低,硅羟基缺陷也明显地增加.0.20~0.45μm的微细晶粒硅沸石的比表面几乎与胶体质点相同,它的外表面积达100m2/g,中孔容积为0.10~0.12ml/g,平均孔径为2.6~2.7nm.这表明微细晶粒硅沸石实际上是纳米质点的结合体. Siliceous MFI type zeolites with high crystallinity were synthesized in the system of (TPA)2O-Na2O-SiO2-H2O at 60℃ by using fumed silica(Ⅰ ) or silica sol(Ⅱ ) as silicon source. The crystal size of products obtained in (Ⅰ ) is 0. 20 μm and in (Ⅱ ) is 0. 45 μm measured by SEM,and 0. 02 μm determined by the method of XRD peak broadness. In comparison with the properties of sample A prepared at 180℃ in the same reactant system,the fine crystals B synthesized at 60℃ possess some nanoparticle characters. The adsorption of n-hexane and specific surface area are abnormally high. Investigated by XRD, FT-IR, 29Si MAS NMR and TG/DTG/DTA, the temperatures for structural damage and for monoclinic /orthorhombic symmetry transfromation of sample B are obviously lower than that of sample A. The defects of Si-OH in sample B are increased apparently. The fine crystals with size of 0. 20-0. 45 μm possesses almost the same BET area as the colloidal particles,which have about 100 m2/g of external surface area, 0. 10-0. 12 ml/g of mesopore volume,and 2. 6~ 2. 7 um of average pore diameter. It indicates that the fine crystals is practically an aggregate composed by nanoparticles.
出处 《复旦学报(自然科学版)》 CAS CSCD 北大核心 1997年第1期97-102,共6页 Journal of Fudan University:Natural Science
关键词 硅沸石 低温合成 纳米质点 微细晶粒 合成 zeolite silicalite-1 low temperature synthesis fine crystals nanoparticle
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