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Probing the Brønsted Acidity of the External Surface of Faujasite‐Type Zeolites
Author(s) -
Lakiss Louwanda,
Vicente Aurélie,
Gilson JeanPierre,
Valtchev Valentin,
Mintova Svetlana,
Vimont Alexandre,
Bedard Robert,
Abdo Suheil,
Bricker Jeffery
Publication year - 2020
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.202000062
Subject(s) - faujasite , zeolite , chemistry , brønsted–lowry acid–base theory , mesoporous material , adsorption , molecule , nuclear magnetic resonance spectroscopy , inorganic chemistry , spectroscopy , catalysis , organic chemistry , physics , quantum mechanics
We outline two methodologies to selectively characterize the Brønsted acidity of the external surface of FAU‐type zeolites by IR and NMR spectroscopy of adsorbed basic probe molecules. The challenge and goal are to develop reliable and quantitative IR and NMR methodologies to investigate the accessibility of acidic sites in the large pore FAU‐type zeolite Y and its mesoporous derivatives often referred to as ultra‐stable Y (USY). The accessibility of their Brønsted acid sites to probe molecules (n‐alkylamines, n‐alkylpyridines, n‐alkylphosphine‐ and phenylphosphine‐oxides) of different molecular sizes is quantitatively monitored either by IR or 31 P NMR spectroscopy. It is now possible, for the first time to quantitatively discriminate between the Brønsted acidity located in the microporosity and on the external surface of large pore zeolites. For instance, the number of external acid sites on a Y (LZY‐64) zeolite represents 2 % of its total acid sites while that of a USY (CBV760) represents 4 % while the latter has a much lower framework Si/Al ratio.