Amino-Functionalized Pore-Expanded MCM-41 for CO2 Adsorption: Effect of Alkyl Chain Length of the Template

Abstract

Solid adsorbents modified with N-containing functional groups have been extensively studied due to their excellent CO2 adsorption performance. In this work, an adsorbent was obtained to capture CO2 by impregnating polyethylenimine (PEI) into MCM-41 with a reserved template that had different alkyl chain lengths [myristyltrimethylammonium bromide (C14), cetyltrimethylammonium bromide (C16), and stearyltrimethylammonium bromide (C18)]. The thermogravimetric analysis, small-angle X-ray diffraction, N2 adsorption–desorption, Fourier transform infrared (FTIR) spectroscopy analysis, and in situ FTIR spectra were employed to study the properties of adsorbents. The results showed that the template had been successfully introduced into the supports in the synthetic process, and the CO2 adsorption performance was quite sensitive to the alkyl chain length of the template. Besides, the adsorbent with the template (C16) exhibited the highest CO2 adsorption capacity (2.49 mmol/g) and amine utilization rate (0.28 mmol CO2/mmol N) under 25 °C and pure CO2. It is believed that the appropriate alkyl chain length of the template could act as an important role in the enhancement of PEI distribution and decrease the CO2 transfer resistance, thereby improving the CO2 adsorption capacity.