Accurate Measurements of NH3 Differential Adsorption Heat Unveil Structural Sensitivity of Brønsted Acid and Brønsted/Lewis Acid Synergy in Zeolites.
J Phys Chem Lett
; 15(4): 863-868, 2024 Feb 01.
Article
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| MEDLINE
| ID: mdl-38237052
ABSTRACT
Differential adsorption heats of NH3 on a series of zeolites, including MOR, MFI, FER, and BEA, are accurately measured to probe their acidity using flow-pulse adsorption microcalorimetry. Initial adsorption heats of NH3 at Brønsted acid sites (BAS) vary between 105 to 136 kJ/mol, depending on framework aluminum amounts and topography structures of zeolites. A Brønsted/Lewis acid synergy between BAS and proximate tricoordinated framework-associated aluminum species is identified to generate super acid sites with initial adsorption heats of NH3 around 150 kJ/mol, but occurs only in the MFI zeolites and sensitively depends on the Si/Al ratio. These accurate data of NH3 differential adsorption heats unveil structural sensitivity of BAS and Brønsted/Lewis acid synergy in zeolites and provide experimental benchmark data for fundamental understanding of acidity and acid-catalysis of zeolites.
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1
Colección:
01-internacional
Base de datos:
MEDLINE
Tipo de estudio:
Diagnostic_studies
Idioma:
En
Revista:
J Phys Chem Lett
Año:
2024
Tipo del documento:
Article