Oscillometric–gravimetric measurements of pure gas adsorption equilibria without the non-adsorption of helium hypothesis

• Published in: Adsorption : journal of the International Adsorption Society Vol. 23; no. 6; pp. 753 - 766
• Main Authors: Keller, J. U., Goebel, M. U., Seeger, Th
• Format: Journal Article
• Language: English
• Published: New York Springer US 01.08.2017; Springer Nature B.V
• Subjects: Activated carbon; Adiabatic flow; Adsorbates; Adsorption; Carbon dioxide; Chemistry; Chemistry and Materials Science; Cylinders; Engineering Thermodynamics; Gravimetry; Heat and Mass Transfer; Helium; Industrial Chemistry/Chemical Engineering; Low frequencies; Oscillations; Resonant frequencies; Reversion; Surfaces and Interfaces; Thin Films; Vertical orientation; Oscillometric measurement method; Sorptive gas oscillations; Gravimetric measurement method; Gas adsorption; Helium non-adsorption hypothesis; Magnetic suspension balances
• ISSN: 0929-5607; 1572-8757
• DOI: 10.1007/s10450-017-9893-2

The adsorption of gaseous carbon dioxide (CO 2 ) at near ambient conditions (297 K, 995 mbar) on activated carbon BAX 1100 (Ingevity), has been measured by a new oscillometric-gravimetric method. The method consists of combined gravimetric and dynamic measurements, namely observations of the frequency of small and nearly adiabatic oscillations of the sorptive gas being in equilibrium with the adsorbed phase of adsorbate. The oscillations observed are actually eigenoscillations of a sorptive gas–sorbate–sorbent system. They are initiated by small oscillations of a sphere or a cylinder positioned in a vertical tube above the vessel containing the gas and the sorbent material reversion of experiment by Rüchardt (Phys. Zeitschr XXX:58, 1929)–Flammersfeld (Z. Naturforsch. 23a:3, 1972). Experiments show that the adsorbate includes two different phases consisting respectively of molecules which are only weakly bound to sorbent’s atoms so that they can participate in the low frequency gas oscillations (<10 Hz), and other molecules being strongly bound to sorbent’s atoms so they are “stiff”, i.e. cannot participate in the gas oscillations, eigenfrequencies being in the range of (10 10 –10 12 ) Hz. The theory of these measurements is outlined and data of adsorption equilibria of carbon dioxide gas on activated carbon BAX 1100 at near ambient conditions which have been measured by three different methods are presented and compared to each other.