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Stoeckli, Fritz

Nom
Stoeckli, Fritz
Affiliation principale
Fonction
Professeur.e émérite
Email
fritz.stoeckli@unine.ch
Identifiants
https://libra.unine.ch/handle/123456789/471

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  • Publication
    Accès libre
    Modelling of water adsorption by activated carbons: effects of microporous structure and oxygen content
    (2005)
    Slasli, Abdou
    ;
    Jorge, M.
    ;
    Stoeckli, Fritz 
    ;
    Seaton, N. A.
    The present paper examines the adsorption of water by microporous carbons containing various amounts of surface oxygen and a smaller proportion of basic centres. The modelling of water adsorption for 293 and 310 K, using variable pore size distributions (PSD), confirms that the overall type IV isotherm is the sum of a type I isotherm associated with the specific interactions, and a type V isotherm reflecting the non-specific interactions. The principle of temperature invariance is followed by these isotherms, which indicates that modelling leads to the Dubinin–Astakhov equation.

    The present approach allows the prediction of water adsorption near room temperature, on the basis of the PSD and the density of oxygen present on the surface area of the micropores. It is assumed, to a first and good approximation, that the pores are slit-shaped and the oxygen distribution is random.
  • Publication
    Accès libre
    Water adsorption by activated carbons in relation to their microporous structure
    (2003)
    Slasli, Abdou
    ;
    Jorge, M.
    ;
    Stoeckli, Fritz 
    ;
    Seaton, N. A.
    The present paper examines the adsorption of water by microporous carbons in the absence of specific interactions. The modelling of water adsorption for 293 and 310 K, using variable pore size distributions (PSD), shows that the type V isotherms follow the Dubinin–Astakhov (DA) equation and fulfill the requirement for temperature invariance. Furthermore, the parameters of the DA equation can be related in a simple way to structural properties of the model carbons. For a number of well-characterized carbons, the type V isotherms generated by combining model isotherms with the corresponding PSDs are in good agreement with the limiting isotherms at 293 and 310 K derived on the basis of a recent development of Dubinin’s theory. This approach will provide the basis for further studies including specific interactions.
  • Publication
    Accès libre
    Reference isotherm for high pressure adsorption of CO2 by carbons at 273 K
    (2001)
    Guillot, André
    ;
    Stoeckli, Fritz 
    It is suggested that the adsorption of CO2 on Vulcan 3G at 273 K and up to 3.2 MPa can be used as a reference isotherm for the characterization of porous and non-porous carbons. The results obtained with the proposed reference are in good agreement with those of the nitrogen (77 K) and benzene (293 K) comparison plots. The external surface areas have also been compared with those obtained from immersion calorimetry into C6H6 at 293 K. It also appears that at low relative pressures CO2 adsorbed on Vulcan 3G follows the Dubinin–Radushkevich–Kaganer equation between 253 and 273 K.
  • Publication
    Accès libre
    On the use of standard DRK isotherms in Dubinin’s t/F method
    (2000)
    Hugi-Cleary, Deirdre
    ;
    Stoeckli, Fritz 
    It is shown that the adsorption of benzene, carbon tetrachloride, dichloromethane and nitrogen by a typical non-porous carbon black follows the Dubinin–Radushkevich–Kaganer equation. The requirement for temperature invariance is fulfilled, with an average characteristic energy Eo=10.8 kJ mol−1. This expression is compared with the standard isotherms for benzene and carbon tetrachloride at 293 K proposed by Dubinin and used as a reference in the so-called t/F method, which leads to the non-porous surface area of active carbons. It appears that Dubinin’s isotherm contains inconsistencies, which are compensated for internally. Alternative DRK expressions, applicable to different vapours, are therefore proposed. The present study also shows the limits of Dubinin’s method with respect to comparison plots at higher relative pressures.
  • Publication
    Accès libre
    On the characterization of microporous carbons by immersion calorimetry alone
    (1997)
    Stoeckli, Fritz 
    ;
    Centeno, Teresa A.
    Immersion calorimetry is a useful tool for the characterization of solid surfaces in general, but in the case of microporous solids it usually requires complementary information, obtained from an adsorption isotherm. This article demonstrates the possibilities and the limitations of this technique when used alone. It appears that the use of a standard value for the enthalpy immersion does not always provide a reliable assessment of the total surface area.