Stepwise dehydration of Cd-exchanged levyne:thermal stability and structural modifications

Cametti, Georgia (2021). Stepwise dehydration of Cd-exchanged levyne:thermal stability and structural modifications. Physics and chemistry of minerals, 48(6), p. 23. Springer 10.1007/s00269-021-01146-6

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Zeolites show remarkable properties that can be tuned through cation exchange of their original extraframework content. In this respect, the response of the modified zeolite to the heating stimuli, in terms of structural modifications and thermal stability, can drastically change and is therefore an important factor to consider. In this study, the dehydration mechanism of a natural levyne previously exchanged with Cd2+ has been monitored in situ by single crystal X-ray diffraction. The initial dehydration trend between 50 and 175°C is similar to that observed for the pristine material, levyne-Ca. The water loss is accompanied by extraframework cation migration within the zeolitic cavities and the unit-cell volume slightly contracts from 3503.8(1) to 3467.8(6) Å3. From 200 to 250°C, a pronounced drop of the unit-cell volume (-7%) is observed. The dehydrated structure at 250°C corresponds to levyne B topology of natural levyne, characterized by the statistical rupture of the T-O-T bonds of the double six-ring membered cage. However, in contrast to levyne-Ca, the fraction of broken connections reached 50% instead of 37%, and no additional structural modifications were detected up to 350°C. At 400°C, diffraction data pointed to the onset of the structural collapse. At this temperature, the measured unit-cell volume was 8% smaller compared to that of the RT structure. The corresponding contracted structure did not rehydrate after exposure to humid conditions for 21 days.

Item Type:

Journal Article (Original Article)

Division/Institute:

08 Faculty of Science > Institute of Geological Sciences > Mineralogy
08 Faculty of Science > Institute of Geological Sciences

UniBE Contributor:

Cametti, Georgia

Subjects:

500 Science > 540 Chemistry
500 Science > 550 Earth sciences & geology

ISSN:

0342-1791

Publisher:

Springer

Language:

English

Submitter:

Georgia Cametti

Date Deposited:

25 Mar 2022 13:28

Last Modified:

27 Mar 2022 01:58

Publisher DOI:

10.1007/s00269-021-01146-6

PubMed ID:

34720350

BORIS DOI:

10.48350/167889

URI:

https://boris.unibe.ch/id/eprint/167889

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