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Titolo:
Determination of the heat of adsorption of ammonia on zeolites from temperature-programmed desorption experiments
Autore:
Joly, JP; Perrard, A;
Indirizzi:
Univ Lyon 1, CNRS, UMR 5634, LACE, F-69622 Villeurbanne, France Univ Lyon 1 Villeurbanne France F-69622 CE, F-69622 Villeurbanne, France Inst Rech Catalyse, CNRS, UPR 5401, F-69626 Villeurbanne, France Inst RechCatalyse Villeurbanne France F-69626 9626 Villeurbanne, France
Titolo Testata:
LANGMUIR
fascicolo: 5, volume: 17, anno: 2001,
pagine: 1538 - 1542
SICI:
0743-7463(20010306)17:5<1538:DOTHOA>2.0.ZU;2-6
Fonte:
ISI
Lingua:
ENG
Soggetto:
POROUS CATALYSTS; ACIDITY;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
15
Recensione:
Indirizzi per estratti:
Indirizzo: Joly, JP Univ Lyon 1, CNRS, UMR 5634, LACE, 43 Blvd 11 Novembre 1918, F-69622 Villeurbanne, France Univ Lyon 1 43 Blvd 11 Novembre 1918 VilleurbanneFrance F-69622
Citazione:
J.P. Joly e A. Perrard, "Determination of the heat of adsorption of ammonia on zeolites from temperature-programmed desorption experiments", LANGMUIR, 17(5), 2001, pp. 1538-1542

Abstract

A general equation, obtained from the classical TPD theory and statisticalthermodynamics, has been designed for determining the enthalpy of adsorption, DeltaH, from a series of temperature-programmed desorption (TPD) runs carried out with various sample masses, heating rates, or inert gas flow rates. This equation applies to TPD performed either under vacuum or under an inert gas stream, provided that readsorption occurs freely during the experiments. It has been applied to ammonia TPD (under vacuum) from HY zeolite samples of different masses. The pressure of ammonia over the sample was in the range 1 x 10(-4)-15 Pa. The value of DeltaH obtained is -136 kJ/mol. Results showed that the molecule of ammonia in the gas phase completely losesits translational motion when it is adsorbed. Finally, a simple experimental method has been proposed to rapidly investigate whether readsorption occurs during the TPD runs. It has been found that, under our experimental conditions, free readsorption effectively takes place at temperatures under 750 K but that desorption is irreversible above this temperature.

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Documento generato il 08/07/20 alle ore 07:49:34