Effect of the amine type on thermal stability of modified mesoporous silica used for CO2 adsorption

In this study, the preparation by grafting of amino-functionalized SBA-15 molecular sieves was carried out. Amino-functionalized molecular sieves were synthesized using a silane coupling agent and different types of amination reagents which react with modified SBA-15. These composites were characterized by FT-IR spectroscopy, X-ray diffraction at low angles, nitrogen physisorption at 77 K, and evaluated by the adsorption of CO2 and its temperature-programmed desorption—TPD. Thermal stability was investigated by TGA and DTA methods. In the view of a possible use of these amino-functionalized molecular sieves as sorbents for CO2 removal, their adsorption–desorption properties towards CO2 were also investigated by the TPD method. The mass loss of amino-functionalized molecular sieves above 215 °C was due to the oxidation and decomposition of amino propyl functional groups. This means that these composites could be used for adsorption of CO2 at temperatures below 215 °C. The adsorption of CO2 and its temperature programmed desorption using thermogravimetry were studied for amino-functionalized molecular sieves at 60 °C. The evolved gases during the adsorption–desorption of CO2 on amino-functionalized molecular sieves were identified by online mass spectrometry coupled with thermogravimetry. CO2 adsorption isotherms of functionalized samples at 60 °C showed that both the adsorption capacity (mg CO2/g adsorbent) and the efficiency of amino groups (mol CO2/mol NH2) depend on the type of amination reagents and the amount of organic compound used.