Regulation mechanism of CO2 capture into the novel non-aqueous biphasic solvent: Solid-liquid phase change controllable

Solid-liquid biphasic absorbents have great potential to reduce the energy consumption for CO2 capture. However, the main problem of the existing solid–liquid phase change absorbents is that solid products are generated immediately at the initial stage of CO absorption, and they are prone to form colloidal solids. A novel non-aqueous biphasic absorbent with solid–liquid phase change controllable feature was proposed in this work, which consisted of ethylenediamine (EDA), 2-amino-2-methyl-1-propanol (AMP) and N-methylformamide (NMF). The absorbent kept a homogeneous phase during the starting process when the loading of the solution was below 1.04 mol mol−1. After that, the solution underwent solid–liquid phase separation as the loading further increased. The CO2 absorption saturation load of the absorbent reached 1.07 mol mol−1, and about 91.45 % of CO2 enriched into the solid phase. The regulation mechanism was investigated by using 13C NMR and molecular simulations. During the absorption process, CO2 first reacted with EDA to form EDACOO− and EDAH+ due to the high reactivity of CO2 and EDA, and as the reaction proceeded to a certain extent, CO2 then combined with AMP to form AMPCOO−. The process products EDAH+ and EDACOO− weakened the hydrogen bond strength and van der Waals forces between AMPH+ and AMPCOO−, increasing the solubility of the intermediate, which resulted in the control of the solid–liquid phase transition that occurred during the reaction.