Impact of aqueous medium on zeolite framework integrity

Aleksei Vjunov, John L. Fulton, Donald M. Camaioni, Jian Z. Hu, Sarah D. Burton, Ilke Arslan, Johannes A. Lercher

Research output: Contribution to journalArticlepeer-review

50 Scopus citations

Abstract

In this work, Al K-edge extended X-ray absorption fine structure and 27Al MAS NMR spectroscopies in combination with DFT calculations are used to determine both qualitative and quantitative structural changes of two well-characterized samples with the BEA structure. The effects of various properties, including Al concentration, Al distribution, particle size, and structural defects, on zeolite stability are explored. As the samples are degraded by treatment in hot liquid water, the local structure about the Al T-site remains mostly intact, including the Al-O-Si angles and bond distances, while the crystalline structure as measured by XRD and STEM is disrupted. The combined data suggests the crystallinity decreases via selective hydrolysis of the T1- and T2-sites that form the 4-member rings of the zeolite framework. The hydrolysis eventually leads to the dissolution of the T-sites followed by reprecipitation on the particle surface resulting in amorphization of the sample.

Original languageEnglish
Pages (from-to)3533-3545
Number of pages13
JournalChemistry of Materials
Volume27
Issue number9
DOIs
StatePublished - 12 May 2015

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