Enhancing Degradation Resistance of Polyethylenimine for CO2 Capture with Cross-Linked Poly(vinyl alcohol)

One critical issue in the development of immobilized amine sorbents for CO2 capture is sorbent degradation, which leads to a significant increase in the overall CO2 capture cost. Here we report a novel approach for enhancing the degradation resistance of a branched polyethylenimine (PEI) by hydroxyl groups (i.e., −OH) of a porous cross-linked poly(vinyl alcohol) (PVA) support. The CO2 capture capacity of a PEI/PVA sorbent showed a 25% decrease and then leveled off. In contrast, the PEI/SiO2 sorbent exhibited more than a 3-fold decrease in CO2 capture capacity after exposure to a cyclic CO2 capture and oxidative degradation environment (15 vol % of CO2 in air at 130 °C). In situ infrared spectroscopic study revealed that the secondary amine is more liable to degrade than the primary amine on PEI/SiO2. On PEI/PVA, the PVA's −OH groups interacted mainly with the secondary amine of branched PEI through a hydrogen bonding, which could contribute to enhancing the resistance of PEI against degradation. This new finding could provide new pathways in the development of low-cost and highly durable amine sorbents by using highly porous polymeric supports with −OH groups.