Properties of multiple Lewis acid sites in alkali metal-exchanged chabazites probed by CO adsorption

0585773 - ÚOCHB 2025 RIV NL eng J - Článek v odborném periodiku
Halámek, J. - Bulánek, R. - Rubeš, Miroslav - Bludský, Ota
Properties of multiple Lewis acid sites in alkali metal-exchanged chabazites probed by CO adsorption.
Microporous and Mesoporous Materials. Roč. 374, June (2024), č. článku 113152. ISSN 1387-1811. E-ISSN 1873-3093
Grant CEP: GA ČR(CZ) GA20-12735S
Výzkumná infrastruktura: e-INFRA CZ - 90140
Institucionální podpora: RVO:61388963
Klíčová slova: ab initio modeling * adsorption * lewis acid sites * alkali metal * carbon monoxide * chabazite * FT-IR * calorimetry
Impakt faktor: 5.2, rok: 2022
Způsob publikování: Omezený přístup
https://doi.org/10.1016/j.micromeso.2024.113152

Carbon monoxide adsorption on alkali-metal exchanged chabazites (M-CHA, where M = Li, Na, K) was investigated across various Si/Al ratios. The study reveals significant insights into the adsorption behavior, including the persistence of cationic preferences with decreasing Si/Al ratios and the existence of multiple-center interactions involving alkali-metal cations and CO. Results show that for high-silica M-CHA zeolites, CO adsorption is effectively described by single and dual adsorption site models, with cation preferences varying by type. In low-silica zeolites, cation positions are primarily influenced by the aluminum distribution and Coulombic interactions. However, the propensity for single-site cation positions (Si/Al→∞) is preserved to a certain degree. The most noticeable example is the small difference between SIII’ occupancies (cations in 8-membered ring windows) in Na-CHA-2 and K-CHA-2 (0.80 vs. 0.85) that strongly influences the rate of diffusion of CO in the M-CHA-2 samples. While FT-IR spectra of high-silica zeolites can be accurately described using cation site stabilities, interaction energies, and CO stretching frequencies, predicting spectra of low-silica chabazites requires a statistical approach and/or molecular dynamics simulations at the DFT level. The findings demonstrate that the dynamical behavior of adsorbates changes dramatically between different alkali metal-exchanged chabazites, highlighting the complex nature of CO adsorption at multiple Lewis acid sites.
Trvalý link: https://hdl.handle.net/11104/0353453