CO2 absorption using a hybrid 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide/titanium dioxide/polyethylene glycol absorbent

Developing novel hybrid ionic liquid/porous material/co-solvent absorbents with the confinement effect is essential for CO2 separation. In this study, CO2 solubilities in 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide/titanium dioxide/polyethylene glycol ([Hmim][Tf2N]/TiO2-PEG200) with different ratios of [Hmim][Tf2N]/TiO2 and various roughnesses of TiO2 (P25 and T500) were measured and described with the Henry's law. Furthermore, the contribution of the confinement effect on the CO2 solubility was quantified, and the relationship between the surface roughness and molecular parameters was established for predicting its contribution to the confinement effect. In addition, the hybrid absorbent was recycled by a multi-cycle experiment. The results show that the contribution of confinement effect on CO2 absorption capacity (on mass basis) and Gibbs free energy occupy around 24.5% and 8.12% in [Hmim][NTf2]/T500-PEG200 (w([Hmim][NTf2]/T500) = 2.88 wt%) at 308.2 K, respectively. The surface roughness can double the confinement effect. Based on the CO2 absorption capacity and enthalpy, [Hmim][NTf2]/T500-PEG200 (w([Hmim][NTf2]/T500) = 2.88 wt%) is a promising hybrid absorbent for CO2 separation. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

This study measured CO2 solubilities in different hybrid absorbents, quantifying the contribution of the confinement effect and establishing the relationship between surface roughness and molecular parameters. The results showed that a specific hybrid absorbent is promising for CO2 separation based on CO2 absorption capacity and enthalpy.