Probing acid sites in MAPO-36 by solid state NMR

1996 ◽  
Vol 39 (3-4) ◽  
pp. 141-146 ◽  
Author(s):  
S. Prasad ◽  
Dewey H. Barich ◽  
James F. Haw
Keyword(s):  
Solid State ◽  
Solid State Nmr ◽  
Acid Sites

scholarly journals Effect of aluminum and sodium on the sorption of water and methanol in microporous MFI-type zeolites and mesoporous SBA-15 materials

Adsorption ◽  
2020 ◽  
Author(s):  
Zheng Li ◽  
Carolin Rieg ◽  
Ann-Katrin Beurer ◽  
Michael Benz ◽  
Johannes Bender ◽  
...  
Keyword(s):  
Solid State ◽  
Solid State Nmr ◽  
Acid Sites ◽  
Mas Nmr ◽  
Nmr Studies ◽  
Oh Groups ◽  
Adsorption Sites ◽  
Low Field ◽  
Strong Adsorption ◽  
Nmr Signals

Abstract The interaction and nature of surface sites for water and methanol sorption on MFI-type zeolites and mesoporous SBA-15 were investigated by solid-state NMR spectroscopy and correlated with the desorption enthalpies determined via TGA/DSC. For siliceous Silicalite-1, 29Si CPMAS NMR studies support stronger methanol than water interactions with SiOH groups of Q3-type. On siliceous SBA-15, SiOH groups of Q2-type are accompanied by an enhanced hydrophilicity. In aluminum-containing Na-ZSM-5, Na+ cations are strong adsorption sites for water and methanol as evidenced by 23Na MAS NMR in agreement with high desorption enthalpies of ΔH = 66–74 kJ/mol. Solid-state NMR of aluminum-containing Na-[Al]SBA-15, in contrast, has shown negligible water and methanol interactions with sodium and aluminum. Desorption enthalpies of ΔH = 44–60 kJ/mol hint at adsorption sites consisting of SiOH groups influenced by distant framework aluminum. On H-ZSM-5, Brønsted acidic OH groups are strong adsorption sites as indicated by partial protonation of water and methanol causing low-field shifts of their 1H MAS NMR signals and enhanced desorption enthalpies. Due to the small number of Brønsted acid sites in aluminum-containing H-[Al]SBA-15, water and methanol adsorption on this material is suggested to mainly occur at SiOH groups with distant framework aluminum species, as in the case of Na-[Al]SBA-15.

A solid-state NMR study of acid sites in zeolite Y using ammonia and trimethylamine as probe molecules

1987 ◽  
Vol 91 (8) ◽  
pp. 2091-2095 ◽  
Author(s):  
William L. Earl ◽  
Paul O. Fritz ◽  
Atholl A. V. Gibson ◽  
Jack H. Lunsford
Keyword(s):  
Solid State ◽  
Solid State Nmr ◽  
Zeolite Y ◽  
Acid Sites ◽  
Probe Molecules ◽  
Nmr Study
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