Silica-Supported Hindered Aminopolymers for CO₂ Capture

Abstract

Sterically\nhindered amine solutions have been studied extensively\nfor CO₂ capture via absorption due to their high theoretical\namine efficiencies (1 CO₂/N) and weak amine–CO₂ species formed. More recently, extensive research has been\nundertaken on amine-based solids in adsorptive CO₂ separations.\nHowever, very limited work exists that describes the behavior of sterically\nhindered amines on solid supports for acid gas separations. To this\nend, the sterically hindered aminopolymer, poly­(2,2-dimethylenimine),\nis synthesized and incorporated into the pores of mesoporous silica,\nSBA-15. The CO₂ adsorption performance of the hindered\npolymer/silica composite is compared with unhindered aminopolymer/silica\ncomposites under dry and humid conditions using in-situ Fourier-transform\ninfrared spectroscopy and fixed bed breakthrough analysis. The\nhindered polymer sorbents had lower amine efficiencies when compared\nwith unhindered polymer sorbents under both dry and humid conditions.\nThe addition of poly­(ethylene glycol) helps alleviate some of the\nlimitations associated with the hindered aminopolymer/silica composites,\nimproving the CO₂ adsorption performance under the conditions\nstudied. The experiments suggest that these hindered polymer sorbents\nare less effective at CO₂ capture than their unhindered\npolymer counterparts due to the poor molecular mobility and hydrophobicity\nof the polymer chains.