Three-component CO2 binding organic liquids for efficient and reversible CO2 capture: Effect of molar ratio of component on mechanism

CO2 binding organic liquids (CO2-BOLs) belong to the CO2-triggered switchable polar solvents (SPSs) in switchable solvents (SSs), which can be used as green non-aqueous CO2 absorbers. A three-component CO2-BOLs composed of superbase, alcohol and amine are introduced in this study. After investigating the effects of different alcohols and amines on the ternary system, the optimum combination of DBN/EG/MEA was determined. In addition, considering the sensitivity of superbase to CO2 in CO2-BOL system, the absorption performance of DBN, DBU and TMG with different pKa in this combination was compared. The temperature, molar ratio and water content of DBN/EG/MEA were explored, and it was found that the optimal absorption was 0.267 g CO2/g solvent at the molar ratio of 1/1/3, 40 °C and 1 bar. Interestingly, different absorption effects are observed when the molar ratio of each component in the ternary system is increased. With the increase of DBN and MEA, the absorption of CO2 increased, but the increase of EG is not conductive to CO2 absorption. Based on nuclear magnetic spectroscopy analysis and quantum chemical calculation, it is found that DBN/EG/MEA with different ratios presents different absorption mechanisms. When the content of DBN is increased to a certain extent, EG which does not have absorptive activity can be activated, so that both MEA and EG can absorb CO2. In addition, the CO2-BOLs synthesized in this study exhibited excellent recoverability. It provides a valuable reference for further design and synthesis of efficient CO2 capture solvents.