Publikace detail

Re-examining the interpretation of CO adsorbed on Lewis acid sites of alkali metal-exchanged MOR zeolite

Autoři: Bulánek Roman | Koudelková Eva | Trachta Michal | Bludsky Ota | Rubes Miroslav

Rok: 2020

Druh publikace: článek v odborném periodiku

Název zdroje: Microporous and Mesoporous Materials

Název nakladatele: Elsevier Science BV

Místo vydání: Amsterdam

Strana od-do: "110007-1"-"110007-8"

Tituly:

Jazyk	Název	Abstrakt	Klíčová slova
cze	Přehodnocení interpretace CO adsorbovaného na Lewisových kyselých polohách v MOR zeolitech s alkalickými kovy	Interakce CO s mordenity s ionty alkalických kovů byly studovány pomocí IR spektroskopie a kalorimetrie. Výsledky byly porovnány s teoretickými výpočty na bázi DFT/CC.	ab initio výpočty; CO; IR spektra; Izosterické teplo; Lewisovy kyselé polohy; zeolity
eng	Re-examining the interpretation of CO adsorbed on Lewis acid sites of alkali metal-exchanged MOR zeolite	The interaction of CO with alkali metal-exchanged mordenite has been investigated by means of IR spectroscopy and calorimetry along with theoretical calculations based on DFT corrected to coupled-cluster accuracy (DFT/CC). It has been convincingly shown that Li+ is at least partially exchanged into the constricted part of the MOR structure as manifested by the low-frequency band at 2181 cm−1 and the isosteric heat of 44 kJ/mol. In the case of Na-MOR samples, significant changes have been observed in the stabilities of high- (2177 cm−1) and low-frequency (2165 cm−1) bands upon CO desorption, with the change of the Si/Al ratio from 40 to 9. Based on the kinetic measurements, it can be concluded that a crucial role in the MOR material is played by diffusion limitations, which are significantly influenced by the Si/Al ratio and the size of the cations. Similar effects also result in the increased stability of the 2138 cm−1 band of Na/K-MOR samples with higher Al content, where the “gate” effect is observed upon N2 adsorption. The dual cationic sites are directly observed only for the K-MOR sample via the weak band around 2150 cm−1. The formation of dual cationic sites cannot be completely ruled out in the case of Na-MOR, but their presence is most likely hidden in the low-frequency band.	Ab initio calculations; CO; IR spectra; Isosteric heats; Lewis acid sites; Zeolites

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