In this study,
we performed the TG-MS analyses on all of the synthesized mesoporous aluminosilicates to verify the existence of the hydroxyl
groups on the adsorbents. As shown in Fig. 6(b), the dehydroxylation
of mesoporous aluminosilicate takes place at around
200 C. Since hydroxyl (water) species is the only species detected
by MS, the amount of hydroxyl groups can be quantified based on
the weight loss determined by thermogravimetric analysis. The
quantity of the hydroxyl group on the mesoporous aluminosilicates
increases with the amount of aluminum dopant, whereas
the 1 C/min and 5 C/min heating rates during calcination produce
the highest and lowest amount of hydroxyl groups on the mesoporous
aluminosilicates, respectively. The reason for this phenomenon
was not clear. One possible explanation is given here.
The formation of hydroxyl groups is mainly affected by calcination
and rehydroxylation steps.