CO₂ absorption mechanism and kinetic modeling of mixed amines with ionic liquid activation

Abstract

Ionic liquid (IL) can not only serve as solvents to reduce carbon capture energy consumption, but also may activate the CO2 absorption of amine solutions. Here, the absorption mechanism and kinetic modeling of IL‐activated single and mixed amines were studied in wetted wall column. N‐(2‐aminoethyl) ethanolamine (AEEA) and N,N‐diethylethanolamine (DEEA) were used as representatives to evaluate the IL activation effects on primary and tertiary amines. It was found that IL activated the reaction process of primary amine, but had no activation effect on tertiary amine. The activation energy of AEEA‐IL‐CO2 was 22.2 kJ/mol, which was 21.0% lower than AEEA‐CO2. Kinetic modeling of IL‐activated AEEA and mixed amines was established. Besides, the density functional theory calculations showed that IL can form hydrogen bonding and other interactions with AEEA and CO2 to activate the absorption reaction, which can reduce 29.3% activation energy during the zwitterion formation stage.