Development of biphasic solvent for CO2 capture by tailoring the polarity of amine solution

A facile screening method for amine/phase splitter/H2O biphasic solvents was proposed. The polarity difference between the high polarity absorption products and the low polarity phase splitter was recognized as the decisive factor for phase separation. In this study, biphasic solvent was developed by tailoring the polarity of absorption products. It’s revealed that the amine/1-propanol/H2O solvents with a dipole moment difference above 6.0 Debye featured phase separation. After screening, TETA/1-propanol/H2O biphasic absorbent with high CO2-rich loading and low regeneration energy was developed. The phase separation behavior was affected by TETA concentration, 1-propanol concentration, and the absorption temperature. Remarkably, the CO2 capacity and volume distribution of the rich phase can be simply tuned by altering the 1-propanol concentration. For the optimal composition of 30 wt% TETA and 50 wt% 1-propanol, a rapid phase separation in 2 min was observed at 60 °C. And the rich phase exhibited a CO2 capacity as high as 6.06 mol/L with a volume proportion of 38.9%. With the promotion of 1-propanol, the CO2 mass transfer coefficient in TETA/1-propanol reached 21.4 × 10−11 mol/cm2·s·Pa, 42.7% higher than 30 wt% TETA and 110.2% higher than 30 wt% MEA. The estimated regeneration heat was 2.06 GJ/t CO2, 48.4% lower than 30 wt% MEA. This research provided a facile screening method and a promising alternative absorbent for CO2 capture.