Non-aqueous energy-efficient absorbents for CO2 capture based on porous silica nanospheres impregnated with amine

Colloidal suspensions as absorbents were synthesized by dispersing porous silica nanospheres (PSNs) modified by amine impregnation in dimethyaminoethoxyethanol (DMEE) for CO2 capture. The results of SEM, TEM, BET, FTIR analysis and TGA indicated that PSNs presented high surface areas and uniform morphology, and the impregnation method could effectively control the amine loading content. In addition, CO2 absorption measurements were conducted to investigate the effects of PEI loading content. The results revealed that the absorption capacities of PEI-PSNs/DMEE first increased and then decreased, and 50 wt%PEI-PSNs/DMEE exhibited the highest CO2 capture capacity, which could be up to 0.728 mmol g−1. Further studies on the effects of the structure of the amines were conducted using polyamines (PEI(600) and PEI(1800)), alkylamines (DETA, TETA, TEPA), and other amines (MEA and [N1111][Gly]). It was found that MEA-PSNs/DMEE and DETA-PSNs/DMEE exhibited better absorption performance than PEI(1800)-PSNs/DMEE and ILs-PSNs/DMEE. This suggested that the functional groups and molecular weight of the amines were important factors affecting the CO2 absorption performance of the colloidal suspensions. Finally, regeneration studies suggested that CO2 could be easily removed from the anhydrous sorbents, thus avoiding the generation of waste water and thereby significantly reducing the energy consumption during the regeneration process.