How to enhance the regenerability of biphasic absorbents for CO2 capture: An efficient strategy by organic alcohols activator

Abstract

Biphasic absorbents feature energy-saving potential but suffer disadvantages in CO2 regenerability. Choosing the proton transfer as the object, an efficient strategy for improving the regeneration process of the biphasic absorbents activated by organic alcohols was proposed in this work. Aided by quantum chemical calculation, the organic alcohols were predicted that could promote proton transfer between CO2 product, which were in the form of ion pairs, thus help CO2 desorption. The shortest H-bond length, the highest binding energy between ion pairs, and the highest partial charges on protons made Ethanol (EtOH) screened as the best activators; for example, activation of N-aminoethylpiperazine (AEP)/sulfolane/H2O with EtOH increased the regeneration efficiency by 27.75%. EtOH promoted the decomposition of carbamate and converted it into ethyl carbonate (C2H5OCOO−), facilitating CO2 release, as revealed by 13C NMR spectra. Furthermore, the activation mechanism was proposed for EtOH-activated CO2 regeneration through theoretical calculations. The most obvious Van der Waals interaction in C2H5OCOO−-protonated AEP (AEPH+) was observed, which help reduce the activation barrier of the proton transfer process. The enhancement of proton transfer between ion pairs, the conversion of carbamate, and the reduction of activation barriers led to the use of organic alcohol activators, especially EtOH, which efficiently enhanced the regenerability of biphasic absorbents for CO2 capture.