A low viscosity and energy saving phase change absorbent of DMEA/MAE/ H2O/TGME for post-combustion CO2 capture

The biphasic absorbent is considered one of the best substitutes for amine solutions because of its great potential to save energy consumption. However, high viscosity and poor CO2 capture capacity of biphasic solvents have emerged as major obstacles to their commercial use. In this work, a strategy to lower the viscosity of the CO2-rich phase was proposed. Based on this strategy, a promising biphasic solvent 2-Dimethylaminoethanol (DMEA)/2Methylaminoethanol (MAE)/H2O was developed by Triethylene glycol monobutyl ether (TGME) regulation. The results show that the maximum viscosity of the CO2-rich phase after CO2 absorption was only 8.34cp. When ignoring the phase separation enthalpy, the CO2 capture efficiency can reach 89.3 % when the energy consumption is 1.99GJ/ tCO2. Besides, the speciation concentration of DMEA/MAE/TGME/H2O with different CO2 loadings was determined by gas-liquid equilibrium theory. Based on the speciation concentration distribution, the possible reaction between CO2 and 2 mol DMEA/ 1.25 mol MAE goes through three stages. 13C NMR analysis was used to investigate the reaction mechanism and phase change behavior, and the salting-out effect was proved to be the reason for the phase change behavior of the DMEA/MAE/TGME/H2O systems. This work also shows that DMEA/MAE/TGME/H2O has a high CO2 absorption capacity and superior CO2 removal efficiency.