Impurities effect on CO2 capture from flue gas by energy-efficient diazole-functionalized ionic liquid solvents

As one of the main greenhouse gases, carbon dioxide (CO 2 ) excessive emission has brought a series of climate change and environmental concerns, especially vast majority of CO 2 emission from coal-fired flue gas due to characteristics of energy structure in China, so CO 2 capture from flue gas is crucial to achieve carbon neutrality and mitigate these problems. Functionalized ionic liquid (IL) hybrid solvents have been regarded as potential absorbents for CO 2 capture, but they still face great challenge how to simultaneously realize high CO 2 mass uptake, low energy consumption and great tolerance under flue gas situation. In this study, the diazole-functionalized IL (DZIL) 1-ethyl-3-methylimidazolium triazole ([Emim][Triz]) was synthesized and blended with N-methylimidazole (N-MI) to form novel DZIL binary anhydrous solvents for CO 2 capture from flue gas. The results indicated that the DZIL solvent ([Emim][Triz]/N-MI) with mass ratio of 90 wt%/10 wt% can not only absorb 0.112 g CO 2 /g absorbent under a feed of 15 % CO 2 in N 2 at 40 °C and 1 bar, but also shows lower regeneration energy consumption of 1.49 GJ/t CO 2 , which is 65 % less than that of 30 wt% MEA solution (4.28 GJ/t CO 2 ). Meanwhile, the results of impurities effect demonstrated that the presence of H 2 O can improve CO 2 capacity and keep good recyclability of DZIL solvents, CO 2 absorption and recyclability performance have almost no change in the presence of O 2 , but a decrease less than 10 % in the presence of SO 2 occurs due to strong interaction between SO 2 and DZIL. The mechanism analysis revealed that both cation [Emim] + and anion [Triz] − of the DZIL can react with CO 2 to form Emim-CO 2 and [Triz-CO 2 ] − , respectively, and the former plays a dominant role in CO 2 absorption. The presence of H 2 O attenuates the formation of Emim-CO 2 but promotes CO 2 absorption capacity by introducing a new pathway of [Triz] − reacting with H 2 O and CO 2 to form [HCO 3 ] − . This study provides a feasible thought for CO 2 capture from flue gas with functionalized IL as energy-efficient absorbents to solve environmental problems.