Fluoride removal from double four-membered ring (D4R) units in As-synthesized Ge-containing zeolites

Type
Article

Authors
Liu, Xiaolong
Ravon, Ugo
Tuel, Alain

KAUST Department
KAUST Catalysis Center (KCC)

KAUST Grant Number
UK-C0017

Date
2011-11-22

Abstract
Fluoride anions can be removed from the framework of as-prepared Ge-containing zeolites ITQ-13 and ITQ-17 without modification of the crystallinity and crystal habit. By contrast to all-silica ITQ-13 for which fluoride could not get out from D4R units, F is completely removed from Ge rich zeolites, even from D4R cages. This has been explained by the relaxing effect of germanium, making F less necessary for the stabilization of the small D4R units. Si/Ge ratios are similar in as-prepared and treated zeolites, indicating that the framework composition is not affected by the removal of anions. The fluoride-free zeolites possess XRD patterns similar to those of the as-made solids but their 29Si NMR spectra are significantly different, revealing the sensitivity of the method to the environment of silicon atoms in the framework. The extent of fluoride that can be removed from D4R units depends not only on the framework Ge content but also on the zeolite topology: for similar contents, F is much more easily eliminated from ITQ-17 than from ITQ-13. © 2011 American Chemical Society.

Citation
Liu, X., Ravon, U., & Tuel, A. (2011). Fluoride Removal from Double Four-Membered Ring (D4R) Units in As-Synthesized Ge-Containing Zeolites. Chemistry of Materials, 23(22), 5052–5057. doi:10.1021/cm2025735

Acknowledgements
This publication is based on work supported by Award UK-C0017, made by King Abdullah University of Science and Technology (KAUST). The authors thank Laurence Burel for SEM pictures.

Publisher
American Chemical Society (ACS)

Journal
Chemistry of Materials

DOI
10.1021/cm2025735

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