Role of 1-methylimidazole in regulating the CO2 capture performance of triethylenetetramine-based biphasic solvents

Abstract

Biphasic solvents are promising candidates for CO2 capture for low regeneration energy consumption. In this study, a novel phase splitter 1-methylimidazole (1-MI) was proposed for triethylenetetramine (TETA) aqueous solvent. 1-MI was proved to act as a phase splitter to induce the phase separation and as an absorption promoter to enhance the absorption rate. By tuning the concentrations of TETA and 1-MI, good phase separation performance was obtained in TETA-1-MI biphasic solvent, achieving a CO2-rich phase loading of 5.41 mol/L. 13C NMR revealed that the upper layer was the CO2-lean phase, containing 1-MI and a small amount of water, while the lower layer was the CO2-rich phase and mainly comprised of TETAH+ and TETA-carbamate. The kinetics results based on the double-film theory indicated that the CO2 absorption rate was mainly controlled by the gas film mass transfer resistance at lower CO2 loading and then by liquid film mass transfer resistance when CO2 loading was higher than 1 mol/L. Owing to the good phase separation behavior triggered by 1-MI, the regeneration heat of TETA-1-MI was 2.26 GJ/t CO2, which was comparable to that of the second-generation solvents, and 43.5 % lower than that of 5 M monoethanolamine (MEA). The present findings indicated that TETA-1-MI had a large loading capacity, high absorption rate, and low energy consumption, which can serve as a novel candidate for CO2 capture.