Study on CO2 absorption by novel choline chloride-diethylenetriamine-water deep eutectic solvents in a rotor-stator reactor

Abstract

Excessive CO2 emissions from flue gas lead to the greenhouse effect and catastrophic climate change and have become a global concern. To address this problem, novel choline chloride-diethylenetriamine-water (ChCl-DETA-H2O) deep eutectic solvents (DESs) with high CO2 absorption capacity was synthesized in this study. It was found that the DES with a composition of 1ChCl-5DETA-2H2O had the highest CO2 absorption capacity, which was up to 0.250 gCO2/gDES. The as-synthesized DESs were adopted for CO2 absorption in a rotor-stator reactor (RSR), and the effects of ChCl-DETA-H2O molar ratio, high gravity factor, liquid flow rate, gas flow rate, temperature, and inlet CO2 concentration on the CO2 absorption efficiency, overall gas-phase volumetric mass-transfer coefficient (KGa) and height of a transfer unit in the RSR were investigated. Analyses on the mechanism of CO2 absorption in the DES suggest that carbamate formed after CO2 absorption by 1ChCl-5DETA-2H2O. A comparison with the traditional packed columns indicates that the KGa in the 1ChCl-5DETA-2H2O/RSR process was about one order of magnitude larger than that in the DETA/packed column process. Also, the 1ChCl-5DETA-2H2O/RSR process achieved a higher CO2 absorption efficiency and KGa than the DETA/rotating packed bed process. This work demonstrates that the RSR enhanced the absorption of CO2 by the DES and the combination of RSR and DES can provide an efficient process for CO2 capture.