Page 220 - Gas Adsorption Equilibria

206 Chapter 4

Figure 4.12. Schematic representation of the working positions of a dual mode suspension
balance. In position (0) only the permanent magnet and the stem below of it are
floating whereas both the sorbent in the basket and the sinker above of it are
resting on their respective mechanical supports. In measuring position (1) the
basket including the sorbent material is lifted. In measuring position (2) both the
baskets filled with sorbent and the sinker above of it are lifted and the total weight
being recorded at the microbalance on top of the installation. (Reprint by
permission of RUBOTHERM GmbH, Bochum, Germany.)

An interesting consequence of simultaneous weighing and sorptive gas
density measurements is that in the case of binary gas mixtures with non-
isomeric components, coadsorption equilibria can be determined from the
data. This procedure is much faster than volumetric – gravimetric
measurements. A basic scheme of the experimental installation is given in
Figure 4.14. It mainly consists of an adsorption chamber (AC) of volume
including a 3 position magnetic suspension balance (RUBOTHERM
GmbH, Bochum, Germany), supply lines for sorptive gases and vacuum,
thermocouples and manometers to take temperatures and pressures inside the
chamber.

To measure binary coadsorption equilibria by the densimetric–gravimet-ric
method one should proceed as follows: After preparing a sorbent sample, i. e.
activating it, cp. Sect. 2.1 and weighing it in vacuum to determine its mass
the adsorption chamber (AC) is filled with a gas mixture of known
concentrations and the circulation pump is turned on.