High-pressure adsorption measurements. A comparative study of the volumetric and gravimetric methods

In this paper, we propose a comparative study between a volumetric apparatus and a gravimetric one, which were developed for the acquisition of high-pressure adsorption isotherms. The volumetric apparatus is able to perform measurements in the temperature range 278-323 K and in the pressure range 0-4000 kPa. We provide a complete report on the experimental errors due to the mass balance calculation based on pressure-volume-temperature measurements. The same analytical study has been achieved for a gravimetric apparatus (temperature range: 223-393 K, pressure range: 0-10 000 kPa). The comparison comments are based on experimental data obtained for the system: activated carbon (CENTAUR Chemviron Carbon)-nitrogen. It appears that for such a system exhibiting quite low adsorbed quantities, important discrepancies may appear if the measurements are not properly achieved. Minimizing the experimental errors for the two experimental techniques leads to an average observed deviation (relative error) between the two methods equal to 3% in the whole measurement range.