3.2. Thermal Stability
The thermal stability of the functionalized samples derived from SBA-15, exemplified by IL1/SBA-15 and IL2/SBA-15, had to be investigated for application. As shown in Fig. 3, the TGA-DSC curve for functionalized silica samples shows a small endothermic peak at 100 oC with some weight loss (~ 4.7% and 7.5% for IL1/SBA-15 and IL2/SBA-15 respectively) up to 110 oC, mainly referring to the evolution of adsorbed retained water. In the temperature range from ~ 110 oC to 280oC, the observed slight weight loss of 2-2.5 % may be attributed to the removal of loosely linked ionic liquid moieties, ensuring the formation of stable and compact functionalizing sheet of ionic liquids (Cao, 2013). The decomposition of the organic sheet on the surface of SBA-15 observed in the 280 oC – 380oC region, with a weight loss of ~ 6%, probably due to the evolution of the charred organic residue. The last stage of weight loss up to 500 oC (with ~ 1% loss) correlated with a broader endothermic peak is likely due to dehydroxylation and/or collapse of silanol sets in the surface network(Cao, 2013).