MFI-type zeolites from natural materials: a comparative study of MFI-type zeolites generated from different diatomite species (part I)
MFI-type zeolites from natural materials: a comparative study of MFI-type zeolites generated from different diatomite species (part I)
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DOI：
10.1007/s10934-016-0222-z
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发表时间：
2016-12-01
影响因子：
2.6
通讯作者：
Enke, Dirk
中科院分区：
文献类型：
--
作者：
Alyosef, Hallah Ahmad;Roggendorf, Hans;Enke, Dirk
报道了一种由预改性沸石直接转化一步法制备MFI型沸石的新方法。采用煅烧和酸处理改性的两种硅藻土作为硅源和铝源。通过对453 K下不同晶化时间后的样品进行分析，研究了相变过程。四丙基氢氧化铵首次被用作双功能分子，用于在沸石形成过程中的二氧化硅溶解和结构导向剂。以这种方式，不需要使用另外的碱源如氢氧化钠来溶解二氧化硅。所应用的硅藻土样品含有无定形二氧化硅以及像长石、硅藻土和石英这样的杂质。这使得改性程序的影响，无定形二氧化硅含量和结晶杂质的不同改性剂样品的MFI型沸石中的直接转化的系统的调查。在转化过程中，长石完全溶解。与经改性的改性的聚碳酸酯起始材料相比，最终产物中的石英含量降低至< 10重量%。采用X射线衍射、氮吸附、扫描电子显微镜和光发射光谱对材料进行了表征。
A new one step approach for the preparation of MFI-type zeolites through direct trans-formation of pre-modified diatomite is reported. Two diatomite species modified by calcination and acid treatment were used as silica and alumina sources. The progress of the transformation was investigated by analyzing samples after different crystallization times at 453 K. Tetrapropylammonium hydroxide was utilized for the first time as bi-functional molecule for silica dissolution in diatomite and structure directing agent during zeolite formation. In this way, the use of an additional alkaline source, such as sodium hydroxide, for silica dissolution was not necessary. The applied diatomite samples contained amorphous silica in combination with impurities like feldspar, anatase and quartz. This allowed the systematic investigation of the influence of modification procedure, amorphous silica content and crystalline impurities of the different diatomite samples on the direct transformation in MFI-type zeolites. During the transformation process, the feldspar was totally dissolved. The quartz content was reduced to < 10 wt% in the final products as compared with the modified diatomite starting material. X-ray diffraction, nitrogen adsorption, scanning electron microscopy and optical emission spectroscopy were used to characterize these materials.