From Molecular Fragments to Crystals: A UV Raman Spectroscopic Study on the Mechanism of Fe-ZSM-5 Synthesis
From Molecular Fragments to Crystals: A UV Raman Spectroscopic Study on the Mechanism of Fe-ZSM-5 Synthesis
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从分子碎片到晶体：紫外拉曼光谱研究 Fe-ZSM-5 合成机理
DOI：
10.1002/chem.200801916
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发表时间：
2009-01-01
影响因子：
4.3
通讯作者：
Li, Can
中科院分区：
文献类型：
--
作者：
Fan, Fengtao;Sun, Keju;Li, Can
利用紫外拉曼光谱、HRTEM、UV/Vis光谱、x射线衍射图和周期DFT计算等手段对Fe-ZSM-5的结晶过程进行了监测。为了避免有机模板在拉曼光谱中的信号干扰，采用无有机方法合成了Fe-ZSM-5。框架铁原子在516、1115和1165 cm处的共振拉曼带（-1）。在1016 cm（-1）处检测到Fe-ZSM-5的拉曼带。在Fe-ZSM-5合成的早期，前驱体含有扭曲四面体配位的铁原子和五元和六元硅酸盐环。基于共振拉曼效应，利用紫外拉曼光谱监测了前驱体物质的聚集成核，并通过周期DFT计算进行了证实。利用紫外拉曼光谱（244和325 nm）和HRTEM监测了表面和体相中铁的演变。非晶颗粒的核部首先成核，并通过吞噬非晶壳在核部形成具有Fe-ZSM-5结构的晶核。最后，非晶颗粒完全转变为Fe-ZSM-5晶体。
The entire sequence of crystallization events of Fe-ZSM-5 was monitored by UV Raman spectroscopy in combination with HRTEM, UV/Vis spectroscopy, X-ray diffraction patterns, and periodic DFT calculations. Fe-ZSM-5 was synthesized by an organic-free method to avoid signal interference from the organic template in Raman spectra. Framework iron atoms with resonance Raman bands at 516, 1115, and 1165 cm(-1). and a Raman band at 1016 cm(-1) are detected for Fe-ZSM-5. In the early stage of Fe-ZSM-5 synthesis, the precursor contains iron atoms in distorted tetrahedral coordination and five- and six-membered silicate rings. Nucleation by aggregation of the precursor species was monitored by U V Raman spectroscopy based on the resonance Raman effect, and confirmed by periodic DFT calculations. Evolution of iron species on the surface and in the bulk phase was monitored by UV Raman spectroscopy with excitation at 244 and 325 nm, as well as HRTEM. Nucleation takes place first in the core of the amorphous particles, and crystalline nuclei with Fe-ZSM-5 structure are formed in the core by consuming the amorphous shell. Finally the amorphous particles are completely transformed into Fe-ZSM-5 crystals.