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.
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