A functionalized ionic liquid phase change absorbent ([DETAH][Py]-DEDM-water) for reversible carbon dioxide capture

Abstract

Phase change absorbent can effectively reduce energy consumption in the process of CO2 capture. In the present work, a series of CO2-capturing phase change absorbents consisting of diethyltriamine pyrazole ([DETAH][Py])-solvent–water have been studied. Among them, [DETAH][Py]-diethylene glycol dimethyl ether (DEDM)-water present good absorption and phase change performance. The experimental results showed that under the conditions of 303.15 K, C[DETAH][Py] = 1 mol/L, VDEDM:water = 4:6, the CO2 absorption reached 1.515 mol CO2/mol IL, and the regeneration efficiency remained 90.75 % at 403.15 K. In addition, the absorption mechanism was explored based on FT-IR and 13C NMR. [DETAH][Py] captured CO2 to generate carbamate, which was then partially hydrolyzed to HCO3−/CO32−. In order to further explain the phase change mechanism, as to absorbed products, the difference of solvation free energy (ΔGsol) between water phase and DEDM phase was calculated by DFT. The results showed that the solubility of products in water is different from the solubility of DEDM, and most of products will dissolve in water, where the organic phase undergoes self-aggregation and is extruded out of the aqueous phase due to salting-out effect, causing phase change.