Abstract: The advanced approach for the preparation of the NH4 form of highly crystalline LSX zeolite under gentle drying conditions (40 °C, membrane pump dynamic vacuum) is discussed. Decationization of this form at moderate temperatures led to the formation of Brønsted acid sites (BASs), whose concentration and strength were characterized by IR spectroscopy. It was found that a maximum concentration of three BASs per unit cell can be achieved at 200 °C prior to the initiation of zeolite structure degradation. The proton affinity of BASs is unusual, and aspires 1240 kJ/mol, which is significantly higher compared to faujasites with higher moduli. The increase in temperature of the heat treatment (up to 300 °C) resulted in thermal decomposition of BASs and the manifestation of amorphous phase with corresponding Lewis acid sites (LASs) as well as terminal Si–OH groups. Both the destruction of BASs and formation of the LAS-containing amorphous phase are the key reasons for the significant decrease in the adsorption capacity in the micropore region revealed for the sample decationized at 300 °C.

Cite: Leonova A.A. , Yashnik S.A. , Paukshtis E.A. , Mel’gunov M.S.
Unusual Acid Sites in LSX Zeolite: Formation Features and Physico-Chemical Properties
Materials. 2023. V.16. N6. 2308 :1-17. DOI: 10.3390/ma16062308 WOS Scopus РИНЦ AN PMID OpenAlex

Dates:

Submitted:	Dec 19, 2022
Accepted:	Mar 4, 2023
Published print:	Mar 13, 2023
Published online:	Mar 13, 2023

Identifiers:

Web of science:	WOS:000958417700001
Scopus:	2-s2.0-85151555738
Elibrary:	54020003
Chemical Abstracts:	2023:649200
PMID:	36984188
OpenAlex:	W4324148973

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