Novel alkanolamine-based biphasic solvent for CO2 capture with low energy consumption and phase change mechanism analysis

Abstract

Biphasic solvents for CO2 capture have received significant attention due to their potential for energy conservation. However, traditional biphasic solvents result in highly viscous CO2 rich-phases and high amine losses. To overcome these drawbacks, we have developed a novel alkanolamine-based biphasic solvent by blending 2-(methylamino) ethanol (MAE), 3-(dimethylamino)propan-1-ol (3DMA1P), diethylene glycol dimethyl ether (DGM), and water. The aqueous MAE/3DMA1P/DGM solvent showed a cyclic capacity of 0.45 mol CO2/mol amine, which is 1.8 times that of monoethanolamine (MEA), and a desorption rate and regeneration efficiency twice those of MEA. The viscosity of the biphasic solvents can be reduced to 13.12 mPa⋅s at 313 K, which is lower than that of reported biphasic solvents. The evaluated regeneration energy was 2.33 GJ/ton CO2. Cation chromatography measurements revealed the tendency of MAE to accumulate in the CO2-rich phase with increasing CO2 absorption loading. Quantitative 13C NMR analyses were performed to investigate the species distribution in both phases, and DGM was found to be the major component of the CO2-lean phase. Different solubilities of the MAE molecules and MAE carbamate in DGM resulted in phase separation. Molecular dynamics (MD) simulations on the CO2-unloaded and CO2-loaded solutions verified the phase separation mechanism. MAE molecules tended to cluster, and the interactions between MAE and DGM dropped significantly, with increasing DGM concentration.