Oxidative degradation of silica-supported polyethylenimine for CO2 adsorption: insights into the nature of deactivated species

Abstract

The oxidative degradation of polyethylenimine-impregnated mesoporous SBA-15 silica for CO₂ capture was investigated at the molecular level. The adsorbents were exposed to flowing air at different temperatures, and their degree of deactivation was evaluated through the measurement of CO₂ adsorption capacity prior and subsequent to air exposure. A solvent-extraction method was employed to isolate the deactivated species from the silica support. The extracted species were investigated by a variety of 1D and 2D NMR techniques such as ¹³C, ¹H, ¹H–¹⁵N HMBC, ¹H–¹³C HMQC, and ¹H–¹³C HMBC. This in-depth investigation showed that they contain predominantly fragments involving imine and carbonyl groups. Several structural units were conclusively established.