Aqueous 2-Ethyl-4-methylimidazole Solution for Efficient CO2 Separation and Purification

Carbon capture and storage (CCS) technology is considered as one of the most effective short-term solutions in reducing atmospheric CO2 concentrations. A key of CCS technology is to seek the absorbent with low cost, fast absorption rate, and high stability. In this study, we show that 2-ethyl-4-methylimidazole is particularly suitable for efficient CO2 capture. The aqueous solution of 2-ethyl-4-methylimidazole displays a maximum CO2 molar absorption capacity of 1.0 mol center dot mol(-1) and the absorbed CO2 can be completely released through heating the solution at a relatively low temperature (<100 degrees C). Stability tests show that the aqueous system is quite stable, with less than 10% loss of the molar absorption capacity after eight absorption-desorption cycles. Time-related in-situ attenuated total reflection infrared absorption spectroscopy and C-13 nuclear magnetic resonance spectroscopy studies reveal that the intermediates are HCO3- and H2CO3 in the process of CO2 absorption-desorption. These intermediates are easily decomposed, which are responsible for the low CO2 desorption temperature and high desorption efficiency of the system. Moreover, the aqueous solution of 2-ethyl-4-methylimidazole is able to separate and purify CO2 from flue gas and even ambient air. Consequently, 2-ethyl-4-methylimidazole is a promising low-cost CO2 absorbent for industrial implementation.