Thermal stability of polyethylenimine based carbon dioxide adsorbents and its influence on selection of regeneration strategies

Two approaches, thermal swing desorption over a range of temperatures and time in an atmosphere of CO2 and using nitrogen as a stripping gas at elevated temperatures, are explored for the regeneration of the polyethylenimine based adsorbents. Thermal swing regeneration was demonstrated to give good cyclic regeneration capacities (2 mmol g−1). However, further reaction of the regenerable carbamate ion to form urea linkages, significantly reduces cyclic capacity and therefore the lifetime of the adsorbent. Regeneration of this secondary reaction product at elevated temperatures was attempted in a nitrogen atmosphere, and whilst recovering some of the original capacity did not fully regenerate the adsorbent. Adsorbent regeneration with nitrogen as a stripping gas was used as an alternative regeneration method, the results of which suggest that steam stripping may be a potential method for adsorbent regeneration.