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.