Adsorption of Co₂ from flue gas streams by a highly efficient and stable aminosilica adsorbent

Three ordered mesoporous silicas (OMSs) with different pore sizes and pore architectures were prepared and modified with amine functional groups by a postgrafting method. The carbon dioxide (CO₂) adsorption on these amine-modified OMSs was measured by using microbalances at 348 K, and their adsorption capacities were found to be 0.2–1.4 mmol g⁻¹ under ambient pressure using dry 15% CO₂. It was found experimentally that the CO₂ adsorption capacity and adsorption rate were attributed to the density of amine groups and pore volume, respectively. A simple method is described for the production of densely anchored amine groups on a solid adsorbent invoking direct incorporation of tetraethylenepentamine onto the as-synthesized OMSs. Unlike conventional amine-modified OMSs, which typically show CO₂ adsorption capacity less than 2 mmol g⁻¹, such organic template occluded amine-OMS composites possessed remarkably high CO₂ uptake of approximately 4.6 mmol g⁻¹ at 348 K and 1 atm for a dry 15% CO₂/nitrogen feed mixture. The enhancement of 8% in CO₂ adsorption capacity was also observed in the presence of 10.6% water vapor. Durability tests done by cyclic adsorption-desorption revealed that these adsorbents also possess excellent stability.