Biphasic solvents based on dual-functionalized ionic liquid for enhanced post-combustion CO2 capture and corrosion inhibition during the absorption process

To reduce the energy consumption for solvent regeneration and mitigate the corrosiveness of saturated solvents, dual-functionalized ionic liquid (IL) [DMAPA][TZ] was synthesized as a primary absorbent, and mixed with a phase separation accelerator poly (ethylene glycol) dimethyl ether (NHD) or propylene carbonate (PC) as biphasic solvents, to achieve high efficiency, energy savings, and corrosion inhibition of post-combustion CO2 capture. The results demonstrated a transition from a homogeneous solvent to a biphasic system upon CO2 absorption, with the majority of CO2 being concentrated in the rich phase, which is related to the formation of hydrogen bonds. Molecular dynamics analysis showed that interaction between the IL and PC is significantly stronger than that with NHD, resulting in a reduced absorption capacity of IL-PC relative to IL-NHD, while NHD effectively suppressed the formation of HCO3−/CO32−. At 373 K, both solvents exhibited efficient regeneration of their respective rich phases within 10 min. The calculated absorption enthalpies for IL-NHD and IL-PC are remarkably low at 0.662 and 0.772 GJ·t−1, respectively, and the regeneration energy consumption of IL-NHD was lower to 1.387 GJ·t−1. Notably, the phase separation accelerator exerts a significant influence on the phase-transition behavior and absorption products of biphasic solvents. Furthermore, ILs effectively inhibited corrosion through the adsorption-passivation mechanism; specifically, the corrosion rate of the CO2-rich phase in IL-NHD relative to 20# carbon steel was only 0.1896 mpy, which is only 1/865 of the rate of the saturated 5 M MEA solution.