Effect of Alkali-Free Synthesis and Post-Synthetic Treatment on Acid Sites in Beta Zeolites

0537817 - ÚFCH JH 2021 RIV CH eng J - Journal Article
Mlekodaj, Kinga - Olszówka, Joanna Elżbieta - Tokárová, V. - Tabor, Edyta - Kašpárek, A. - Nováková, J. - Šťávová, G. - Gonsiorová, O. - Pelíšková, L. - Brus, Jiří - Pilař, Radim - Klein, Petr - Dědeček, Jiří
Effect of Alkali-Free Synthesis and Post-Synthetic Treatment on Acid Sites in Beta Zeolites.
Molecules. Roč. 25, č. 15 (2020), č. článku 3434. E-ISSN 1420-3049
R&D Projects: GA ČR GA18-20303S; GA MŠMT(CZ) LM2015073; GA MŠMT(CZ) EF16_013/0001821
Institutional support: RVO:61388955 ; RVO:61389013
Keywords : al-27 mas * nmr-spectroscopy * bea-asterisk * aluminum * catalysis * silicon * nox * dealumination * framework * pyridine * beta zeolite * alkali-free synthesis * acid sites
OECD category: Physical chemistry; Polymer science (UMCH-V)
Impact factor: 4.412, year: 2020
Method of publishing: Open access

Beta zeolites with Si/Al around 14 were prepared using three new alkali-free synthesis methods based on the application of amorphous aluminosilicate precursor and calcined in ammonia or air. All samples exhibit structural and textural properties of standard beta zeolite. Comprehensive study by(27)Al and(29)Si MAS NMR, together with FTIR adsorption of d(3)-acetonitrile and pyridine were used to characterize the influence of both the synthesis and calcination procedure on the framework Al atoms and related Bronsted and Lewis acid sites. While calcination in ammonia preserves all framework Al atoms, calcination in air results in 15% release of framework Al, but without restrictions of the accessibility of the beta zeolite channel system for bulky pyridine molecules. Terminal (SiO)(3)AlOH groups present in the hydrated zeolites were suggested as a precursor of framework Al-Lewis sites. Surprisingly, the mild dealumination of the air-calcined zeolites result in an increase of the concentration of Bronsted acid sites and a decrease of the total concentration of Lewis sites with the formation of the extra-framework ones.
Permanent Link: http://hdl.handle.net/11104/0315652