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

Abstract

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∙mol−1 and the absorbed CO2 can be completely released through heating the solution at a relatively low temperature (<100 °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 13C 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.