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Stoeckli, Fritz

Nom
Stoeckli, Fritz
Affiliation principale
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Professeur honoraire
Email
fritz.stoeckli@unine.ch

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  • Publication
    Accès libre
    Dubinin’s Theory: A Versatile Tool in Adsorption Science
    (1998)
    Stoeckli, Fritz 
    ;
    Lavanchy, A.
    ;
    Hugi-Cleary, Deirdre
    Ce travail présente la théorie de Dubinin, ses conséquences en calorimétrie d'immersion ainsi que des développements recents. En particulier, la description des isothennes de type V par I'équation de Dubinin-Astakhov (vapeur d'eau sur les charbons actifs) et la combinaison avec la theorie de Myers et Prausnitz qui conduit à une description de l’adsorption multiple en régimes statique et dynamique. La théorie de Dubinin inclut également l’adsorption de vapeurs par certains solides non poreux., The paper presents the main features of Dubinin's theory for the volume-filling of micropores, its direct consequences in the field of immersion calorimelry and recent developments such as the possibility to describe type V isotherms (water on active carbons) with the Dubinin-Astakhov equation, and to deal with multiple adsorption under static and dynamic conditions. It also confirmed that in some cases Dubinin's theory applies to adsorption by non-porous surfaces.
  • Publication
    Métadonnées seulement
    Dubinin's theory and its contribution to adsorption science
    (2001)
    Stoeckli, Fritz 
    Dubinin's theory for the volume filling of micropores (TVFM), originally developed for the adsorption of single vapours by microporous solids such as activated carbons and Zeolites, has gradually been extended to other areas. They include immersion calorimetry, the adsorption of water vapour and of mixtures, as well as adsorption front aqueous solutions. Recent studies in the field of adsorption from aqueous solutions, by activated carbons, suggest that the principle of temperature invariance is fulfilled and in the case of phenolic compounds a modified DRK equation can be used to predict the adsorption equilibrium over a certain range of temperatures. Computer modelling of CO2 adsorption by carbons at 273 K leads to micropore distributions, which are in good agreement with those derived from other techniques. It also appears that the model isotherm, in single slit-shaped micropores can be fitted to the Hill-de Boer isotherm, in agreement with mathematical studies of the origin of the Dubinin-Astakhov equation.
  • Publication
    Accès libre
    The Dubinin Equation and the Size of Micropores in Active Carbons
    (1974)
    Stoeckli, Fritz 
    A recently suggested relation between the Polanyi adsorption potential and the width Z of slot-like pores, is examimed from the point of view of Dubinin’s theory for the filling of micropores. The relation involves the structural constant B which varies with Z2.
  • Publication
    Accès libre
  • Publication
    Accès libre
    The characterization of microporosity in carbons with molecular sieve effects
    (2002)
    Stoeckli, Fritz 
    ;
    Slasli, Abdou
    ;
    Hugi-Cleary, Deirdre
    ;
    Guillot, André
    The apparent and the real micropore size distributions (PSDs) of molecular sieve carbons can be assessed by combining the adsorption of CO2 at 273 K with immersion calorimetry into liquids of increasing molecular dimensions. On the basis of model isotherms resulting from computer simulations, the adsorption of carbon dioxide, a relatively small probe, leads to the overall PSD of the carbon (essentially the internal micropore system). Immersion calorimetry, on the other hand, reveals the distribution of the pores accessible directly from the liquid phase, that is without constrictions. Liquid CS2 probes the same volume as CO2 and can be used as a reference. The paper describes the case of an industrial molecular sieve carbon obtained by blocking partly the entrance to a relatively broad micropore system, thus limiting its accessibility to molecules with diameters below 0.5–0.6 nm. It is shown how activation by steam at 900 °C removes the constrictions and leads to a gradual overlap of the two PSDs. The distribution of the pore widths on the surface, observed directly by scanning tunnelling microscopy, is also given.
  • Publication
    Accès libre
  • Publication
    Accès libre
    Changes in the micropore structure of strongly activated carbons, induced by large adsorbate molecules
    (1980)
    Stoeckli, Fritz 
    ;
    Perret, André
    ;
    Mena, Philippe
    Adsorption of molecules with increasing sizes, by strongly activated carbons, is characterized by a restricted accessibility of the micropore system for relative pressures p/p0< 10−3 approx. The adsorption capacity at low pressures increases with successive adsorption-desorption cycles. The adsorption of relatively small molecular probes, considered in the light of the generalized equation proposed by Stoeckli, suggests that substantial but largely reversible modifications are induced in the micropore system by the large adsorptives. This is also in agreement with the results obtained from the heats of immersion of a heterogeneous carbon into benzene and tertiobutyl-benzene, before and after treatment with tertiobutyl-benzene.
  • Publication
    Accès libre
    Recent Developments in the Context of the Dubinin-Astakhov Equation
    (1982)
    Stoeckli, Fritz 
    ;
    Lavanchy, A.
    ;
    Kraehenbuehl, F.
    The present work deals with two important aspects of the Dubinin-Astakhov equation, the fundamental relation of the theory for the filling of micropores. First, the theoretical basis of this equation is examined in the framework of a possible model, which leads to a reasonable agreement with experimental results. Secondly, it is shown how the D-A equation leads to an exact relation for the calculation of enthalpies of immersion of microporous carbons into organic liquids. So far, this relation has been tested with more than 35 systems (10 carbons and 8 liquids).
  • Publication
    Accès libre
    Microporosity in carbon blacks
    (2002)
    Stoeckli, Fritz 
    ;
    Guillot, André
    ;
    Slasli, Abdou
    ;
    Hugi-Cleary, Deirdre
    Microporous carbon blacks can be characterized by the same techniques as activated carbons, using the classical DR equation and comparison plots based on non-porous materials. The CO2 adsorption isotherm at 273 K, combined with computer modelling, also leads to an assessment of microporosity. The results agree with independent techniques such as immersion calorimetry into liquids of variable molecular dimensions and a modified Dubinin equation. The study also confirms that the comparison plots based on N2 (77 K), CO2 (273 K) and C6H6 (293 K) do not necessarily lead to overlapping results for the total micropore volume and the external surface area of the carbons.