ISSN:
1572-879X
Keywords:
Acidity
;
heat of adsorption
;
microcalorimetry
;
ammonia
;
zeolite
;
γ-Al2O3
;
HNa-Y
;
H-mordenite
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
Notes:
Abstract The acidities ofγ-Al2O3, HNa-Y zeolite, and H-mordenite have been examined by microcalorimetric measurements of ammonia adsorption at 423 K. The differential heat of adsorption on γ-Al2O3 decreases continuously with ammonia coverage from an initial value of 165 kJ/ mol at low coverages to a value of 70 kJ/mol at higher coverages. The differential heat of adsorption on HNa-Y zeolite shows similar behavior, with a plateau of nearly constant heat at 115 kJ/mol. H-mordenite exhibits a nearly constant heat of adsorption equal to 155 kJ/mol. The results from these microcalorimetric measurements are in agreement with thermogravimetric and temperature-programmed desorption results collected at higher temperatures. Adsorbed ammonia has sufficient mobility at 423 K to equilibrate with the catalyst surface on the time scale of microcalorimetric measurements, and these measurements provide an effective method for quantifying acid site distributions of solid-acid catalysts.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00811355
