Development of polyethylenimine-functionalized mesoporous Si-MCM-41 for CO2 adsorption

•We investigated CO2 adsorption on polyethylenimine (PEI)-functionalized Si-MCM-41•Effects of amine loading, temperature and pressure on CO2 adsorption were studied•CO2 adsorption was highest (99.44 mg/g) at 100 °C for 50 wt% PEI-Si-MCM-41•The adsorbent possessed good cyclic regenerability and CO2 selectivity over N2 and H2•FTIR analysis confirmed the CO2 interaction with amino groups via chemisorption

This work describes the functionalization of mesoporous Si-MCM-41 with different loadings of polyethylenimine (PEI), their characterization and detailed study of their CO2 adsorption performance. A series of Si-MCM-41 samples functionalized with 10-50 wt% PEI was synthesized by wet impregnation method. The physicochemical properties such as pore structural ordering and textural properties of the samples were characterized by X-ray diffraction and N2 adsorption/desorption analysis, respectively. The XRD analysis of pristine Si-MCM-41 showed well-defined four diffraction peaks of (100), (110), (200) and (210) planes. Upon loading of 10-50 wt% PEI, intensity of these diffraction peaks reduced gradually due to decrease in scattering contrast. Also, N2 adsorption/desorption analysis showed change in textural properties from porous to non-porous material as the loading of PEI increased from 10 to 50 wt%. To optimize the loading of PEI for maximum CO2 adsorption, samples were screened at 25 °C and 0-1 bar using a gravimetric method. The sample containing 50 wt% PEI showed the highest CO2 uptake of 47.93 mg/g due to high content of CO2-affinity sites and was further used to investigate the effect of temperature ranging from 25 to 125 °C on CO2 adsorption performance. The best CO2 adsorption (99.44 mg/g) was obtained at 100 °C and 1 bar due to flexible behavior of PEI. At this optimized temperature, the Si-MCM-41 containing 50 wt% PEI was used to evaluate the effect of pressure ranging from 0 to 20 bar where it showed increase in CO2 adsorption uptake of 156 mg/g. Si-MCM-41 containing 50 wt% PEI showed strong affinity for CO2 compared to N2 and H2. In a regeneration study, a gradual decline in CO2 uptake was observed as the number of adsorption/desorption cycles increased. Infrared spectroscopy revealed carbamates formation confirming the interaction of CO2 with the amino groups of PEI incorporated into Si-MCM-41 containing 50 wt% PEI via chemisorption.

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