Stoeckli, Fritz

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.

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 E_o=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.

2002, Stoeckli, Fritz, Guillot, André, Slasli, Abdou, Hugi-Cleary, Deirdre

Activated carbons are disorganized materials with variable pore size distributions (PSD). If one assumes that the porosity consists mainly of locally slit-shaped micropores, model isotherms can be obtained by computer simulations and used to assess the PSD on the basis of experimental isotherms. In the present study, CO2 isotherms have been measured at 273 K on seven well-characterized microporous carbons with average micropore widths between 0.65 and 1.5 nm and analysed with model isotherms obtained with standard Monte Carlo simulations. The resulting PSD are in good agreement with those obtained from a modified Dubinin equation, from liquid probes of molecular dimensions between 0.4 and 1.5 nm, from STM and from modelling based on CH4 adsorption at 308 K. The present study validates the determination of micropore distributions in active carbons based on CO2 isotherms, provided that no gate effects are present.

2001, Stoeckli, Fritz, López-Ramón, M. V., Hugi-Cleary, Deirdre, Guillot, André