Adsorptive Removal of Carbon Dioxide Using Polyethyleneimine Supported on Propanesulfonic-Acid-Functionalized Mesoporous SBA-15

One-step synthesized sulfonic-acid-functionalized SBA-15 (denoted as alpha SSBA-15) impregnated with polyethyleneimine (PEI) was used for CO2 capture in this study. The resulted sorbents were characterized via a range of analytical techniques, including transmission electron microscopy (TEM), Si-29 magic angle spinning (MAS) nuclear magnetic resonance (NMR), infrared (IR), thermogravimetry-differential scanning calorimetry (TG DSC), etc. Experimental results showed that the incorporation of propanesulfonic acid groups into the inner structure of the silica support had brought dramatic improvement in CO2 adsorption capacity, of which PEI/SSSBA-15 showed the highest CO2 adsorption amount. The main reason of this increased capacity could be attributed to the enhanced CO2 diffusion into bulk networks of PEI polymers because of its better dispersion in the pores of support, where the extended propanesulfonic acid groups on the inner surface could spatially disperse the subsequent loaded PEI molecules. Furthermore, the PEI/5SSBA-15 also exhibited superior stable cyclic adsorption/desorption performance compared to PEI/SBA-15, especially after 5 cycles. This was assumed because the enhanced surface acidity of PEI/5SSBA-15 anchored the NH2/NH groups through acid-base interaction, reducing the loss of active sites.