A novel phase change absorbent with ionic liquid as promoter for low energy-consuming CO2 capture

Phase change absorbents had great potential to achieve low energy-consuming CO2 capture. In this work, a novel four-component phase change absorbent system, N,N-diethylethanolamine (DEEA)/N-(2-aminoethyl) ethanolamine (AEEA)/1-butyl-3-methyl imidazolium tetrafluoroborate ([Bmim][BF4])/H2O blends, was designed. AEEA and DEEA were used as the main absorption component and the phase separation component, respectively. As one of the most conventional ionic liquids, [Bmim][BF4] was introduced as a promoter to improve the phase separation capability and the absorption/desorption performance. The species distribution was determined by C-13 NMR analysis, and it was found that [Bmim][BF4] was located in the lower phase. Quantum chemical calculations unveiled that the main reason for phase separation was the difference in polarity and hydrogen bond interactions. The introduction of the [Bmim][BF4] not only promoted CO2 absorption through chemical and physical intensification effects but also enhanced the desorption rate through hydrogen bond formation. Moreover, the [Bmim][BF4] addition significantly reduced regeneration energy consumption due to its lower heat capacity and less water evaporation. The energy consumption of this absorbent could be reduced to 2.06 GJ center dot t(-1) CO2, which was 45.8% less than 30 wt% MEA.