The effect of ionic liquid [Bmim][BF4] on the kinetics of CO2 desorption in amine solutions

Here, the effect of ionic liquid (IL) on the kinetics of CO2 desorption in amine solutions was investigated. N-(2-aminoethyl) ethanolamine (AEEA) and N,N-diethylethanolamine (DEEA) were used as representatives of primary/secondary and tertiary amines. Results indicated that IL had a promoting effect on AEEA, but not on DEEA. The initial desorption rate of AEEA can be improved by up to 36.4%. Kinetics for IL-activated AEEA was developed through a modified Arrhenius equation, and the activation energy was 38.48 kJ/mol, which was 10.7% lower than that of AEEA. The species distribution was monitored by 13C NMR, which showed that the IL was not directly involved in the reaction, but might activate desorption through hydrogen bonding. Furthermore, theoretical calculations revealed that the IL can form hydrogen bonding with carbamate during the desorption of primary/secondary amines to lower the energy barrier for the zwitterion formation reaction, while only weaker hydrogen bonding was formed during the desorption of tertiary amines.