Developing strategies for the regeneration of polyethylenimine based CO2 adsorbents

Abstract

Abstract Adsorption is considered to be one of the more promising technologies for capturing CO 2 from flue gases. The efficient adsorption of CO 2 at low partial pressures, associated with post-combustion capture, require chemical type adsorbents containing basic amine functional groups. It has been demonstrated that amine polymers, for example polyethylenimine (PEI), immobilised on various porous substrates, silica, zeolites and fly ash, are effective adsorbents for CO 2 . When considering the use of adsorption for large scale CO 2 capture, the ease of regeneration and the lifetime of the adsorbents are critical factors in determining their efficiency, cost and therefore feasibility for use. In this paper two approaches, thermal swing adsorption (TSA) cycles over a range of temperatures and time in an atmosphere of CO 2 and thermally assisted pressure swing desorption, are explored for the regeneration of the PEI based adsorbents. The reactions occurring during the TSA regeneration of PEI based adsorbents in an atmosphere of CO 2 , especially the formation of a thermostable complex between PEI and CO 2 above 130 ∘ C are described. Identification of the complex by FTIR, XPS and 13 C NMR as a urea linkage will be described. Overall, the results from this research have implications for the selection of regeneration strategies of all amine based CO 2 adsorbents.