Polyethyleneimine-Modified Amorphous Silica for the Selective Adsorption of CO2/N2 at High Temperatures

Abstract

Mechanochemistry is very attractive as an efficient, solvent-free, and simplified technique for the preparation of composite adsorbents. Here, a series of polyethyleneimine (PEI)-modified SiO2 adsorbents were prepared via mechanical ball milling for selective adsorption of CO2 at high temperatures. The structural properties of these adsorbents were characterized by XRD, SEM, TGA, FTIR, and N2 adsorption–desorption. This method can better disperse the PEI evenly in the SiO2 as well as maintain the porous structure of the adsorbents by comparing with the impregnated adsorbents. These adsorbents presented appreciable performance in separating CO2 at high temperatures, and the CO2 adsorption capacity of PEI(70%)/SiO2 is up to 2.47 mmol/g at 70 °C and 1.5 bar, which is significantly higher than that of the same type of CO2 adsorbent reported in the literature. Furthermore, the adsorbent of PEI(70%)/SiO2 provided an ideally infinite selectivity for CO2/N2 (15:85) at 70 °C. These results showed that mechanical grinding methods are a simple and effective approach to producing amine-modified silica composite adsorbents.