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

Abstract

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.