Page 105 - Gas Adsorption Equilibria

2. Volumetry / Manometry 91

4. VOLUMETRIC MEASUREMENT OF
MULTICOMPONENT GAS ADSORPTION
EQUILIBRIA (N > 1)

4.1 Experimental

Coadsorption equilibria of multi-component gases on porous materials
today most often are measured by using volumetric / manometric instruments.
The flow diagram of such a device is sketched in Fig. 2.6. It basically has the
same structure as the instrument for pure gas adsorption measurements, Fig.
2.1. However, one now has to provide a gas circulation loop including a pump
between the storage vessel and the adsorption chamber in order to maintain
equal and constant sorptive gas concentrations everywhere in the system. Also
a sample loop has to be added which may be outside the thermostat but in any
case has to be connected to a gas chromatograph or mass spectrometer. No
commercial suppliers of volumetric multi-component gas adsorption
instruments are known to the authors, cp. [2.3, 2.4]. However, an instrument
which easily can be used as such, after having been equipped with a standard
gas chromatograph, is offered by BEL Japan, cp. Chapter 4. Materials of
vessels and tubes should be chosen according to the recommendations given
in Section 2.1. For the analysis of a sorptive gas sample in a gas
chromatograph, helium at elevated temperatures (373 K – 473 K) should be
used as a carrier gas. More information for design of a multicomponent
volumetric gas adsorption instrument is given in [2.20].

Figure 2.6. Experimental set-up for (static) volumetric / manometric measurements of
multicomponent gas adsorption equilibria.