Assessment of CO 2 Capture into Efficient EAE/NHD Water Lean Solvent: CO 2 Capture Performance, Phase Change Behavior, and Mechanism Analysis

Water lean solvents have received growing attention for CO 2 capture due to their low solvent evaporation and potential for energy saving. The previous study mainly focused on the organic diluent selection and paid less efforts on the amine effect. In this study, 11 types of amines with representative structures were selected to explore the effect of amine on CO 2 loading and CO 2 distribution with poly(ethylene glycol) dimethyl ether (NHD) as organic diluent. Based on the cyclic loading and reaction heat comparison, N -ethylethanolamine (EAE) was selected and the EAE/NHD water lean solvent was constructed. The liquid–liquid phase separation was found in the EAE/NHD/H 2 O system with more than 95% CO 2 concentrated in the lower phase, which yielded high cyclic loading and benefited regeneration energy consumption. The water content effect was further investigated in terms of CO 2 cyclic loading and phase separation behaviors, suggesting that EAE/NHD/H 2 O with a mass ratio of 3:6:1 exhibited the excellent performance of 3.03 mol·kg –1 cyclic loading and 2.27 GJ·t –1 CO 2 regeneration energy consumption. 13 C NMR and quantum chemistry calculations were conducted to explain the reaction route and phase change mechanism. The large difference between the ion–dipole interaction of ion–H 2 O and the molecule–molecular interaction of ion-NHD was regarded as the main reason for phase separation. The long-term tests indicated the cycling stability and low corrosivity of EAE/NHD/H 2 O, as exhibited by the stable CO 2 cyclic loading during 8 runs of absorption–desorption and lower corrosivity rate of carbon steel than 30 wt % MEA aqueous solution.