Thermal and Kinetic Performance of Water Desorption for N2 Adsorption in Li-LSX Zeolite

The effect of small amounts of water in inhibiting the adsorption of N-2 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 N-2 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 FlynnWallOzawa 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 CoatsRedfern method. Moreover, the observations for the exponential declination of N-2 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.