CO<sub>2</sub>-Binding Organic Liquids Comprised of 1,1,3,3-Tetramethylguanidine and Alkanol for Postcombustion CO<sub>2</sub> Capture: Water Inhibitory Effect of Amine Promoters
Ali Hedayati, Farzaneh Feyzi
Abstract
CO2-binding organic liquids (CO2-BOLs) are switchable polarity solvents that can be used as nonaqueous green solvents for energy-efficient CO2 capture. In this study, the novel three-component CO2-BOLs comprised of 1,1,3,3-tetramethylguanidine (TMG) as a superbase, an alkanol (methanol, n-butanol, sec-butanol, and 1-hexanol), and an amine (EEA, MEA, AMP, DEA, AEEA, PZ, TETA, and DETA) were introduced. Screening experiments were performed to find the best combination of solvent components based on CO2 loading and absorption rate. The TMG/methanol/MEA BOL with a molar ratio of 0.3/0.6/0.1 was selected as the preferred solvent, which has an equilibrium absorption (αeq) and a CO2 uptake within 30 min (αR) of 0.396 and 0.283 mol CO2/mol solvent, respectively. CO2-BOLs were characterized using FTIR, 1H NMR, and 13C NMR spectroscopy to specify the produced ionic species, explain the water inhibitory effect of MEA, and propose a plausible reaction mechanism for the reaction of CO2 with the three-component BOLs in the absence and presence of water impurity. It was found that the addition of MEA to the two-component BOLs (base/alcohol) restricts the formation and precipitation of bicarbonate salt that leads to the lower energy consumption for solvent regeneration.