Page 70 - Gas Adsorption Equilibria

56 Chapter 1

Figure 1.21. Surface structure of zeolite molecular sieve UOP/Linde MS13X. Macropores and
capillaries supporting transport of sorptive gas molecules to and from meso- and
micropores clearly can be recognized.

5.1 Models for the Void Volume of a Sorbent
Material and the Volume of a Sorbate

In this Section we are going to present four different models for the
volume of porous solid impenetrable to the molecules of a sorptive gas
a
and also for the volume of the absolute or total mass of a sorbate
phase [1.50].

The approximation of the void volume of a sorbent material most
often used in practice today is the so-called helium volume i. e. the
proposition

can be calculated from the mass balance (1.19) of helium sorption
experiments, assuming helium not to be adsorbed, i. e. Then the
mass balance Eq. (1.19) reads

leading to