School of Earth Sciences and Resources, China University of Geosciences, Beijing 100083, China.
School of Science, China University of Geosciences, Beijing 100083, China.
Int J Mol Sci. 2022 Feb 8;23(3):1893. doi: 10.3390/ijms23031893.
Deep eutectic solvents (DESs) have been widely used to capture CO in recent years. Understanding CO mechanisms by DESs is crucial to the design of efficient DESs for carbon capture. In this work, we studied the CO absorption mechanism by DESs based on ethylene glycol (EG) and protic ionic liquid ([MEAH][Im]), formed by monoethanolamine (MEA) with imidazole (Im). The interactions between CO and DESs [MEAH][Im]-EG (1:3) are investigated thoroughly by applying H and C nuclear magnetic resonance (NMR), 2-D NMR, and Fourier-transform infrared (FTIR) techniques. Surprisingly, the results indicate that CO not only binds to the amine group of MEA but also reacts with the deprotonated EG, yielding carbamate and carbonate species, respectively. The reaction mechanism between CO and DESs is proposed, which includes two pathways. One pathway is the deprotonation of the [MEAH] cation by the [Im] anion, resulting in the formation of neutral molecule MEA, which then reacts with CO to form a carbamate species. In the other pathway, EG is deprotonated by the [Im], and then the deprotonated EG, HO-CH-CH-O, binds with CO to form a carbonate species. The absorption mechanism found by this work is different from those of other DESs formed by protic ionic liquids and EG, and we believe the new insights into the interactions between CO and DESs will be beneficial to the design and applications of DESs for carbon capture in the future.
近年来，深共晶溶剂（DESs）已被广泛用于 CO 的捕获。理解 DESs 对 CO 的捕获机制对于设计高效的 CO 捕获用 DESs 至关重要。在这项工作中，我们研究了由乙二醇（EG）和质子离子液体([MEAH][Im])形成的 DESs 对 CO 的吸收机制，其中 [MEAH][Im] 是由单乙醇胺（MEA）和咪唑（Im）组成的。通过应用氢核和碳核核磁共振（NMR）、二维 NMR 和傅里叶变换红外（FTIR）技术，深入研究了 CO 与 DESs [MEAH][Im]-EG（1:3）之间的相互作用。令人惊讶的是，结果表明 CO 不仅与 MEA 的胺基结合，还与去质子化的 EG 反应，分别生成氨基甲酸酯和碳酸盐物种。提出了 CO 与 DESs 之间的反应机制，包括两条途径。一条途径是 [MEAH]阳离子被 [Im]阴离子去质子化，生成中性分子 MEA，然后与 CO 反应生成氨基甲酸酯物种。另一条途径是 EG 被 [Im]去质子化，然后去质子化的 EG，HO-CH-CH-O，与 CO 结合形成碳酸盐物种。这项工作发现的吸收机制与由质子离子液体和 EG 形成的其他 DESs 不同，我们相信对 CO 与 DESs 之间相互作用的新认识将有助于未来设计和应用 DESs 进行 CO 捕获。
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