Amine-modified SBA-12 mesoporous silica for carbon dioxide capture: Effect of amine basicity on sorption properties

SBA-12 mesoporous silica was modified by 3-aminopropyl (AP), 3-(methylamino)propyl (MAP) and 3-(phenylamino)propyl (PAP) ligands. The electronic effects in AP, MAP and PAP ligands resulted in different surface basicity of the modified silica materials. The materials were characterized by thermogravimetry, X-ray powder diffraction, nitrogen adsorption/desorption and transmission electron microscopy. The CO2 sorption/desorption experiments performed at 25 oC by gravimetric method showed that carbon dioxide sorption capacities were 1.04 mmol/g for the sample SBA-12/AP, 0.98 mmol/g for the sample SBA-12/MAP and 0.68 mmol/g for the sample SBA-12/PAP. The modified silica can be regenerated by purge with inert gas without heating. The fastest desorption was observed for the SBA-12/PAP silica containing amine of low basicity (pKb = 8.9). The desorption process of SBA-12/AP and SBA-12/MAP samples was accompanied by consumption of heat evolved on adsorption, while no thermal effect was recorded on the DTA curve of SBA-12/PAP sample.