Role of additives in silica-supported polyethylenimine adsorbents for CO₂ adsorption

SiO₂ aerogels were prepared by sol-gel method and methyl alkylation reaction using TEOS as silicon sources. Silica-supported polyethylenimine (PEI/SiO₂) adsorbents for CO₂ adsorption were prepare by grafting techniques, in which mesoporous SiO₂ aerogel was loaded with PEI and organic compounds functionalized by hydroxyl or amino groups as dopants. CO₂ adsorption isotherms of PEI amine-modified SiO₂ aerogels were measured and the results show that the maximum CO₂ adsorption capacity (1.8 mmol g⁻¹) was obtained over a doped SA-PEI-N-Y loaded with 45% PEI and 15% N-Y (N-[3-(Trimethoxysilyl)propyl]ethylenediamine, denoted as N-Y). In addition, SA-PEI-N-Y has stronger thermal stability than SA-PEI-60% in nitrogen from room temperature to 800 °C at a heating rate of 10 °C min⁻¹. It turns out that N-[3-(Trimethoxysilyl)propyl]ethylenediamine is the best dopant. (paper)