Incomplete CO2 Desorption Enhances O2 Stability of Solid Amine Carbon Capture Sorbents.

Reducing carbon dioxide (CO2) emissions is a critical environmental challenge. Capturing CO2 by solid polyethylenimine (PEI) sorbents is proposed as a strategy to address this concern. The CO2 forms carbamates with the amine groups on the solid sorbent. However, solid PEI sorbents are unstable under O2-containing flue gas streams, a property that has greatly limited their industrial importance. To combat this O2-sensitivity, the amount of CO2 desorbed per cycle is reduced to protect amines by the formed carbamates. These carbamates sufficiently reduce oxidative cleavage and maintain a low kdeac of -0.00373 cycle-1 while maintaining a working capacity of 2.88 wt% (0.65 mmol g-1) under an O2-containing gas mixture. Additionally, it is discovered that the degradation rate can be tuned through adjusting the sorbent working capacity; this tunability can be used to inform future process simulations. This approach offers an additive-free pathway toward oxidatively stable PEI carbon capture sorbents.