Energy Reduction in Phase-Change Absorbents: Bridging the Gap between Theory and Practice with Additives

Biphasic absorbents show promise for energy-efficient CO2 capture. This study evaluates 1-(2-aminoethyl)piperazine (AEP)/triethylene glycol dimethyl ether (TEGDME)/H2O systems with low volatility. To further enhance the cyclic CO2 capacity and decrease the viscosity of an absorbent and then reduce the energy consumption, four additives were incorporated. The optimal formulation of 10 wt %AEP/20 wt %DMEA/35 wt %TEGDME/35 wt %H2O achieved 82.5% regeneration efficiency and 1.04 mol/L cyclic CO2 capacity, which were 3.24 and 2.23 times higher than the non-additive baseline, respectively. Additionally, at 40 °C, the viscosity decreased from 60.5 to 12.4 mPa s. Compared with the 30 wt % MEA solution, the relative heat duty was reduced by 56% and 24% at 20 and 40 min, respectively. The molecular composition before and after phase separation was determined. Quantitative analysis using 13C NMR and LAMMPS simulations elucidated the phase separation mechanisms of the AEP/DMEA/TEGDME/H2O absorbent system.