Rational Design of the Polymeric Amines in Solid Adsorbents for Postcombustion Carbon Dioxide Capture.

Substantial efforts have been made to increase the CO working capacity of amine adsorbents for an efficient CO capture. However, the more important metric for assessing adsorbents is the regeneration heat required for capturing a fixed amount of CO. In this work, we synthesized polyethyleneimine (PEI)/SiO adsorbents functionalized with various epoxides. This provided adsorbents with six different amine structures showing various CO/HO adsorption properties. Our studies revealed that the CO working capacity was not a decisive factor in determining the regeneration heat required for CO capture. This is because the benefit of large CO working capacity was canceled out by the difficulty of CO desorption. Instead, the suppression of HO co-adsorption was critical for reducing the regeneration heat because substantial latent heat is required for HO desorption. Consequently, the PEI/SiO functionalized with 1,2-epoxybutane required a much lower regeneration heat (2.66 GJ tCO) than the conventional PEI/SiO (4.03 GJ tCO) because of suppressed HO co-adsorption as well as moderately high CO working capacity.