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Stoeckli, Fritz

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

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  • Publication
    Accès libre
    Adsorption and structural studies on activated carbons
    (1977)
    Stoeckli, Fritz 
    ;
    Huber, U.
    The porous structure of activated carbons is examined from the point of view of gas adsorption, and in relation to classical methods such as X-ray diffraction and electron microscopy. It is suggested that the different approaches to the problem of microporosity should provide complementary information, which can be useful for a better understanding of static and dynamic adsorption processes in activated carbons.
  • Publication
    Accès libre
    Comparative study of gas adsorption and small angle X-ray scattering by active carbons, in relation to heterogeneity
    (1979)
    Jánosi, A.
    ;
    Stoeckli, Fritz 
    A comparative study of selected active carbons shows that the spread of the structural parameter B, implied by the generalized adsorption equation of Stoeckli, is compatible with the spread of the Guinier gyration radii suggested by the small-angle scattering of X-rays. In the case of a molecular-sieve carbon having a large micropore volume, there is no spread for either parameter. It is suggested, that all available SAXS and adsorption data should be reconsidered in terms of continuous distributions.
  • Publication
    Accès libre
    Specific and Nonspecific Interactions between Methanol and Ethanol and Active Carbons
    (2000)
    López-Ramón, María Victoria
    ;
    Stoeckli, Fritz 
    ;
    Moreno-Castilla, Carlos
    ;
    Carrasco-Marín, Francisco
    The interaction of methanol and ethanol with active carbons of different origins and containing between 0.81 and 7 mmol g-1 surface oxygen has been examined by immersion calorimetry and by vapor adsorption at 293 K, benzene being the reference. The results obtained by these independent techniques are in excellent agreement. With respect to pure carbons, the surface oxygen leads to excess enthalpies of immersion of 5.32 and 2.64 J mmol-1 oxygen for methanol and ethanol. Alternatively, it appears that the affinity coefficients β(CH3OH) and β(C2H5OH), which appear in the Dubinin−Astakhov equation, are functions of the oxygen content and of the enthalpy of immersion into benzene. The limiting values, as the oxygen content tends to zero, are respectively 0.40 and 0.62, in agreement with the values quoted in the literature. It is also found that the adsorption of CO2 is not affected by the oxygen content of the surface and β(CO2) = 0.40.
  • Publication
    Accès libre
    The Excess Enthalpies and volumes of Mixing of Methanol with Octan-2-ol
    (1981)
    Leupin, Paulette
    ;
    Powell, Bernard
    ;
    Stoeckli, Fritz 
    The functions HE and VE have been measured at 303.15 K. for the mixtures of methanol with (±), (+) and (-) octan-2-ol. As expected, it is found that the excess functions are identical for the optical isomers, within experimental error. The volume of mixing of the ( +) and ( —) isomers is also found to be equal to zero.
  • Publication
    Accès libre
    The physical and chemical characterization of a sulphur-impregnated active carbon, by combined adsorption and immersion techniques
    (1991)
    Rebstein, Patrick
    ;
    Stoeckli, Fritz 
    A commercially available active carbon, impregnated with sulphur, has been characterized and compared to the original carbon by using adsorption and immersion techniques. The specific reaction of liquid CS2 with sulphur, following the preadsorption of various amounts of n-nonane, shows that the accessibility of sulphur decreases rapidly. It is also found that the impregnated carbon becomes hydrophilic but, in the case of SO2 adsorption, no change in adsorption capacity is detected.
  • Publication
    Accès libre
    Applications of Immersion Calorimetry in Dubinin’s Theory and Electrochemistry
    (2008)
    Stoeckli, Fritz 
    ;
    Centeno, Teresa A.
    This study shows that immersion calorimetry is a useful technique which simplifies considerably the analysis of porosity and chemical nature of activated carbons. The characterization of activated carbons in the general theoretical framework of Dubinin's theory with its extensions to calorimetry and adsorption from solutions allows the identification of some key parameters for the performance of these materials in electrochemical capacitors.
  • Publication
    Accès libre
    Activation chimique des charbons par les hydroxydes, carbonates et oxydes des métaux alcalins
    (1994)
    Lebgaa, Dénia
    ;
    Ehrburger, Pierre
    ;
    Papirer, Eugène
    ;
    Donnet, Jean-Baptiste
    ;
    Stoeckli, Fritz 
    Chemical activation of coals using aïkali metal hydroxides, oxides and carbonates. The preparation of active carbons is described, starting from two coals originating from Freyming and Oignies. Varions hydroxides, oxides and aïkali carbonates were used but the originality of this study is the use of cesium derivatives. The interpretation of the Coa adsorption isotherms shows clear differences among the various reagents. It is seen that CsOH is more efficient than KOH, and that Cs20 is even more active than CsOH. Furthermore, by mixing an inactive hydroxide (NaOH) with KOH, a new, more efficient, activating agent was obtained. Immersion calorimetry studies confirm the gas adsorption results. Finally, scanning electron microscopy and scanning tunnelling microscopy evidence the formation of porosity.
  • Publication
    Accès libre
    Equilibrium adsorption of binary mixtures of gases by zeolites and the state of the adsorption phase
    (1998)
    Ustinov, E. A.
    ;
    Polyakov, N. S.
    ;
    Stoeckli, Fritz 
    A method for analyzing the state of the adsorption phase was developed on the basis of statistical thermodynamics for the case of equilibrium adsorption of binary gaseous mixtures. The procedure for treating experimental data to determine the Helmholtz energy and other thermodynamic functions of a mixture of molecules occluded within zeolite cavities was proposed. A measure of ideal behavior of a mixture of a small number of molecules in the micropore was formulated; in the asymptotic limit such a behavior leads to the Raoult law and to assumption of the validity of the Raoult law when moving along the line of constant value of the Gibbs integral in the ideal adsorption solution theory.
  • Publication
    Accès libre
    The Dubinin theory of micropore filling and the adsorption of simple molecules by active carbons over a large range of temperature
    (1976)
    Stoeckli, Fritz 
    ;
    Houriet, Jean-Philippe
    It is shown that the values of the structural constant B and of the micropore volume Wo can change considerably for certain active carbons, when the adsorption of simple gases is measured over a large range of temperature. The changes are probably related to ultramicroporosity, present in heterogeneous carbons, and to activated diffusion into typical micropores, through constrictions. It is suggested that the quantity B is not necessarily a constant for a given solid, as assumed previously.