The effect of small amounts of water
in inhibiting the adsorption
of N2 gas on different cationic forms of LSX zeolite was
investigated using thermogravimetric and derivative thermogravimetry
(TG-DTG) techniques at different heating rates, which is shown to
be a very effective way of studying the influence of strongly adsorbed
water on adsorption of less-strongly adsorbed N2 molecules.
According to DTG profiles, the apparent activation energies (E) relating to the thermal desorption of water molecules
existing in the skeleton of Na- and Li-LSX zeolites were estimated
through both the Kissinger and Flynn–Wall–Ozawa methods.
The E values calculated from these two equations
were in close agreement, and the thermal dehydration mechanism was
further studied on the basis of the Coats–Redfern method. Moreover,
the observations for the exponential declination of N2 adsorption
amount with the loading of water revealed that the adsorption capacity
of cationic zeolites was significantly influenced by water through
reducing heterogeneity and strength of the electric field. More specifically,
the E value at high temperature was higher than that
at low temperature, implying that at high temperature, decomposition
of bonded water belongs to dynamic-based control, whereas the dehydration
process of physisorbed water belongs to diffusion-based control at
low temperature.