Amino-Functionalized Pore-Expanded MCM-41 for CO₂Adsorption: Effect of Alkyl Chain Length of the Template

Solid adsorbents modified with N-containing functional groups have been extensively studied due to their excellent CO₂adsorption performance. In this work, an adsorbent was obtained to capture CO₂by 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, N₂adsorption-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 CO₂adsorption performance was quite sensitive to the alkyl chain length of the template. Besides, the adsorbent with the template (C16) exhibited the highest CO₂adsorption 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 CO₂transfer resistance, thereby improving the CO₂adsorption capacity.