Zeolites with Fewer Defects and Improved Stability

  • Author: ChemistryViews.org
  • Published: 19 February 2020
  • Copyright: Wiley-VCH Verlag GmbH & Co. KGaA
  • Source / Publisher: Journal of the American Chemical Society/ACS Publications
  • Associated Societies: American Chemical Society (ACS), USA
thumbnail image: Zeolites with Fewer Defects and Improved Stability

Zeolites are porous aluminosilicates. They have applications, e.g., in ion-exchange processes, adsorption, and catalysis. Zeolites are very stable compared to many other porous materials. However, they are often used under very harsh conditions, for example, as a catalyst for steam cracking or exhaust gas treatment. In these processes, the zeolites are exposed to high-temperature steam, which causes degradation. This degradation generally starts at defect sites in the zeolite structure.


Toru Wakihara, The University of Tokyo, Japan, and colleagues have developed a method for healing defects in zeolites and making these porous materials even more stable. The team used high-silica zeolites of the types ZSM-5 (pictured), beta zeolite, and mordenite and treated them in an aqueous solution of NH4F and tetramethylammonium hydroxide (TEAOH) at 40–170 °C for 3–24 h. The samples were then washed, dried, and calcined at 550 °C.


The team found that the treated zeolites can withstand extremely high-temperature steam (900–1150 °C), while their untreated counterparts degrade under the same conditions. The team attributes this improvement to a reduction in structural defects, which is caused by silicate species that migrate within the structure and heal the defects. This migration process is promoted by the hydroxide and fluoride ions in the treatment solution, while the trimethylammonium cations act as "pore fillers" and stabilize the crystalline network during treatment.


 

 

Article Views: 960

Sign in Area

Please sign in below

Additional Sign In options

Please note that to comment on an article you must be registered and logged in.
Registration is for free, you may already be registered to receive, e.g., the newsletter. When you register on this website, please ensure you view our terms and conditions. All comments are subject to moderation.

Article Comments - To add a comment please sign in

Bookmark and Share

If you would like to reuse any content, in print or online, from ChemistryViews.org, please contact us first for permission. more


CONNECT:

ChemistryViews.org on Facebook

ChemistryViews.org on Twitter ChemistryViews.org on YouTube ChemistryViews.org on LinkedIn Sign up for our free newsletter


Magazine of Chemistry Europe (16 European Chemical Societies)published by Wiley-VCH