Applicability of linear polyethylenimine supported on nano-silica for the adsorption of CO2 from various sources including dry air

Abstract

Adsorbents based on linear polyethylenimines (LPEIs) supported on fumed silica were prepared and studied for the reversible adsorption of CO₂ under mild conditions from various gas mixtures, including dry air with a CO₂ concentration of only 400 ppm. While the adsorption kinetics were similar between linear and branched PEI impregnated on fumed silica, the desorption rate was noticeably faster on linear PEI, which is advantageous for fast adsorption/desorption cycling. The enthalpy of CO₂ adsorption was also lower on LPEI based adsorbents (−43 to −53 kJ mol⁻¹ CO₂). Desorption of the adsorbed CO₂ occurred rapidly at relatively low temperatures (50 to 100 °C). The adsorption/desorption process can be repeated for more than one hundred cycles with no noticeable decrease in adsorption capacity even under humid conditions. The stability of the adsorbents under CO₂, air, and N₂ was also investigated.