Loosely bonded dual-functionalized ionic liquid-based phase change solvent for energy-saving CO2 capture

A phase change solvent based on a novel loosely bonded dual-functionalized ionic liquids (ILs) containing diethylenetriamine (DETA) and 1-methylimidazole (1-MI), namely [DETA][1-MI], was developed. The strong anion-cation interactions in an ILs inhibited the CO2-ILs interaction and decrease the absorption capacity of the ILs. The weak interaction of [DETA][1-MI] retained most of the absorption capacity of DETA and 1-MI (up to 2.06 mol CO2/mol ILs). When simulated flue gas was fed into the [DETA][1-MI] + dimethylformamide (DMF) + H2O phase change solvent, the CO2-rich phase had a CO2 concentration of up to 6.51 mol CO2/L and a volume ratio of 42.2%. Moreover, a regeneration efficiency of > 90% was maintained even after three regeneration cycles at 393 K. The corresponding regeneration heat (1.40 GJ/ton CO2) was only 36.8% of 30 wt% mono-ethanolamine (MEA, 3.80 GJ/ton CO2). To the best of our knowledge, it's well below the reported regeneration energy of amine-based absorbents. In addition, the corrosion rates of the rich and lean phases were only 0.58% and 0.51% of those of the saturated MEA solution, indicating that the corrosivity of [DETA][1-MI] + DMF + H2O was negligible. Moreover, [1-MI]- was observed to promote the formation of m-DETACOO- and HCO3-/CO32-, further enhancing the CO2 absorption capacity. Therefore, the proposed [DETA][1-MI] + DMF + H2O was verified to be a promising absorbent with favorable absorption properties, a low corrosion rate, high cyclic stability, and superior energy efficiency for CO2 capture.