Recent concern over the anthropogenic CO2 and its impact on global climate change has driven the investigation of new potentially more efficient CO2 capture technologies. Among several possible strategies to reduce CO2 emissions from large point sources such as coal-fired power plants, adsorption by solid sorbents has been widely studied because of its potential to be less energy-intensive than the current aqueous amine solution processes. Post-combustion CO2 capture is normally carried out between 45¢ªC and 125¢ªC, near ambient pressure, from the flue gases containing diluted CO2 (~10-15 volume %). A number of supported amine adsorbents are known to be applicable for post-combustion capture, as reviewed recently.  . We recently reported a hyperbranched aminosilica (HAS) as an example of a new class of amine-based solid adsorbents that can provide a large CO2 capacity as well as outstanding regenerability in a cyclic CO2 capture process. This material is prepared by the ring-opening polymerization of aziridine on a porous supports such as mesoporous silica, yielding low molecular weight aminopolymers functionalized onto the inorganic substrates. For example, early investigation of an unoptimized HAS adsorbent revealed a relatively high adsorption capacity of >3 mmol CO2/g at 25 ° from humidified, simulated flue gas, that was fully regenerable over 10 adsorption/desorption cycles.
This talk will describe the engineering of these inorganic-organic hybrids to improve its CO2 adsorption characteristics, including its CO2 capture capacity and adsorption kinetics. For this objective, synthesis-structure-property relationships were established for the family of HAS adsorbents. Specifically, the adsorbent structure was controlled by tuning the synthesis variables such as solvent and reactant concentration, as well as by changing the pore characteristics and surface functionalities of the supports. The effects of these structural changes on the CO2 capture properties of the HAS adsorbents will be described by analyzing the adsorption parameters such as the working CO2 capacity and adsorption half time. Based on these data, we will present a potential route to optimize the configuration of the HAS hybrids, which allows an ability to design enhanced HAS adsorbents with desired CO2 adsorption properties.
 S. Choi, J. H. Drese, C. W. Jones, ChemSusChem 2009, 2, 796-854.
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