(30a) Design of Aminopolymer Structure to Enhance Performance and Stability of CO2 Sorbents: Poly(propylenimine) Vs. Poly(ethylenimine)

Authors: 
Pang, S. H., Georgia Institute of Technology
Lively, R. P., Georgia Institute of Technology
Jones, C. W., Georgia Institute of Technology
Research efforts in CO2 capture technologies have dramatically increased due to interest in reducing the effect of anthropogenic emissions on atmospheric CO2 concentrations. Much of this research has focused on capture from large point sources such as flue gas. Direct capture of CO2 from ambient air is proposed as a complementary technology that has the advantage of not needing a flue gas feed stream and thus is more versatile in its deployment. However, at an ultradilute concentration of 400 ppm, the driving force for adsorption is low, necessitating the development of adsorbents that may be different from those used in flue gas capture. Additionally, these adsorbents must be stable under oxidizing conditions due to the presence of oxygen in the feed stream and the potential for oxygen to contact the adsorbent material during high temperature regeneration.

In this contribution, we report the finding that poly(propylenimine) (PPI) based structures have significantly improved sorption properties compared to the structurally-similar and well-studied poly(ethylenimine) (PEI). Specifically, we find that PPI-based sorbents are more effective at CO2 capture, resulting in higher amine efficiencies, and perhaps more importantly, have improved stability under high temperature oxidizing conditions. Our experiments suggest that PPI-based CO2 sorbents may allow for longer sorbent working lifetimes due to an increased tolerance to sorbent regeneration conditions and will have larger adsorption swing capacities, both of which will drive down the cost associated with CO2 capture.