Calorimetric measurement of heats of vapour adsorption on graphitized thermal carbon black

Abstract

Heats of adsorption of various vapours have been measured on Sterling FT-FF graphitized carbon black in a calorimeter at 293–383 K. Curves representing the dependence of the heat of adsorption on surface concentration have a maximum at temperatures of 352 K or higher. After treatment of the carbon black surface with hydrogen at 1423 K this maximum remains in the case of triethylamine and iso-octane but it is absent in the case of cyclohexane. Corresponding isotherms of adsorption have steps at the same surface concentration as the maximum. This phenomenon seems to be related to the penetration of molecules into defects of molecular size in the graphite basal planes. Such penetration can take place if there are increases of temperature and adsorbate concentration. Adsorption isotherms at low coverage are similar to Henry's isotherms, and values of the heat of adsorption decrease when the temperature increases. These values are compared with the results of other authors.