CO₂ adsorption by polyamine-based protic ionic liquid-functionalized mesoporous silica: regenerability and influence of flue gas contaminants

Polyamine-based protic ionic liquid (PILs)-functionalized mesoporous silica has drawn much attention due to its high CO₂ adsorption rate, high CO₂ adsorption capacity, and recyclability. However, the performance of these materials under realistic operating conditions and the influence of flue gas contaminants such as SO_x, NO_x, and water vapor remain unexplored. In this study, the effects of these flue gas contaminants on CO₂ adsorption of PILs-functionalized SBA-15 are evaluated through breakthrough experiments. The results show that the CO₂ adsorption capacity and capture rate of the hybrid sorbents are increased by about one-third in the presence of trace water vapor. This is attributed to additional CO₂ capture pathways with amine groups that result from the humid environment. The additional pathway was further explained with FT-IR spectroscopy and DFT calculations, which reveal that in the presence of water vapor the CO₂ molecules react with amine groups to form stable zwitterionic bicarbonate ions. On the other hand, the sorbents have strong resistance to SO₂ and NO over the tested concentration range of 0–500 ppm, with limited impact on CO₂ capture. After 8 cyclic adsorption/regeneration experiments, the CO₂ adsorption capacities of the sorbents almost are constant when compared to the first cycle performance.