Effect of amine structure on CO₂ adsorption of modified poly(ethyleneimine)-impregnated mesostructured silica sorbents

Poly(ethyleneimine) (PEI) was modified to investigate the effect of amine type and introduced hydroxy groups on its ability to capture CO₂. Amines were impregnated in as-synthesized mesostructured silica (MSU-F) to fabricate solid amines, and the obtained samples were characterized. Nitrogen contents, structural properties, adsorption capacity, and sorbent durability during CO₂ adsorption/desorption processes were determined to evaluate the CO₂ sorption performances of the sorbents. Reaction between PEI and propylene oxide altered the ratio of primary, secondary, and tertiary amines, and also produced hydroxy groups on amine molecules. With a specific reactant ratio, a modified amine-impregnated sorbent (M-EP10) demonstrated a 13.90 wt. % and 0.37 CO₂ adsorption capacity and amine efficiency, respectively, which were higher than that of the pristine PEI-impregnated sorbent. Also, the new adsorbents exhibited great stability in cyclic adsorption-desorption operations, even under pure CO₂ desorption conditions in which commercial PEI adsorbents are known to lose CO₂ adsorption capacity due to urea formation.