MFI-type zeolites from natural materials: a comparative study of MFI-type zeolites generated from different diatomite species (part I)

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• 作者：Hallah Ahmad Alyosef ; Hans Roggendorf ; Denise Schneider…
• 关键词：Modified diatomite ; Silica source ; MFI ; type zeolite ; Amorphous silica ; Quartz
• 刊名：Journal of Porous Materials
• 出版年：2016
• 出版时间：December 2016
• 年：2016
• 卷：23
• 期：6
• 页码：1609-1618
• 全文大小：1,650 KB
• 刊物类别：Chemistry and Materials Science
• 刊物主题：Chemistry
  Catalysis
  Characterization and Evaluation Materials
  Physical Chemistry
  
• 出版者：Springer Netherlands
• ISSN：1573-4854
• 卷排序：23

文摘

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.