CO2 Capture Partner Molecules in Highly Loaded PEI Sorbents

Decoupling amine loading from diffusion resistance is one of the main challenges in the development of immobilized amine CO2 sorbents. Water has been reported to serve this goal, alleviating CO2 diffusional hindrance in highly loaded amine sorbents. Acting as a mass transport facilitator, water is not the only partner molecule able to enhance bulk CO2 diffusion. Herein, we show that the enhancing effect of methanol is comparable to that of water in polyethylenimine-based sorbents. Other molecules, such as ethanol, isopropanol, and chloroform, were also examined but did not appear to facilitate CO2 transport and uptake. Based on a comparison of the Hansen solubility parameters of these molecules, it appears that polarity plays a crucial role in enhancing CO2 diffusion together with molecular hindrance and hydrogen bonding to a lesser extent.