Page 196 - Gas Adsorption Equilibria

182 Chapter 4

automated instrument equipped with a magnetic suspension balance,
Rubotherm, Bochum for volumetric-gravimetric measurements, cp. Sect. 2.4.

In this chapter we will present experimental information (Sect. 2.1), the
theory of measurement (Sect. 2.2), and uncertainties (Sect. 2.3), and several
examples (Sect. 2.4) of this method. Two modified versions of the
measurement procedure which may be called densimetric-gravimetric and
densimetric-volumetric / manometric methods (which especially seems to be
suited for online industrial coadsorption measurements) are also outlined
(Sect. 3). These methods also may be used to measure adsorption of gases and
/ or vapors on surfaces of arbitrary solid materials as for example the inner
walls of vessels, tubes, valves etc. of the experimental device(s) used
(Sect.3.6). Advantages and disadvantages of the methods proposed are
discussed in Sect. 4. A list of symbols used is given in Sect. 5, followed by
references to journal articles and books cited.

2. VOLUMETRIC – GRAVIMETRIC
MEASUREMENTS OF BINARY COADSORPTION
EQUILIBRIA

2.1 Experimental

A multipurpose instrument allowing multicomponent coadsorption
measurements by the volumetric/manometric-chromatographic method, Chap.
2, as well as by gravimetric-chromatographic measurements, Chap. 3, has
been designed and built for the first time in the working group of the authors
in 1989, [2.5], [4.2]. It mainly consisted in a gas storage vessel an
adsorption chamber a two beam microbalance outside the adsorption
vessel (Sartorius 4104, Göttingen), a gas circulation loop including a pump
(Brey, GK 24-02N, Memmingen), a gas chromatograph, thermostats, gas
supply, vacuum pump, thermocouples and manometers to take measurements
of temperatures and pressures. A schematic diagram of this installation is
given in Figure 4.1, followed by a photo, cp. also [2.5], p. 207. More
information on the instrument, especially specifications of vessels, tubes,
valves etc. can be found in the literature [2.6, 2.20, 4.2–4.4].