Devising piperazine-based liquid-liquid phase change absorbents with MEA and triglyme for energy-efficient CO₂ capture

The PZ-MEA-TGM-H 2 O phase change absorbent system was developed for CO 2 capture. • The phase-transition behavior of the PZ-MEA-TGM-H 2 O system is regulated by the PZ-to-water ratio. • The P 15 M 6 T 39 H 40 system exhibits high absorption rate and low energy consumption during CO 2 capture. • The phase-transition mechanism of PZ-MEA-TGM-H₂O has been fully elucidated. Liquid-liquid phase change absorbents offer substantial potential for reducing energy consumption in industrial CO₂ capture. Building on the favorable CO₂ capture performance of piperazine (PZ) and the high boiling point of triethylene glycol dimethyl ether (TGM), a PZ-TGM-H₂O phase change absorption system was developed. By incorporating various organic amines to tune the system, the addition of MEA was found to effectively enhance the absorption performance. Through systematic ratio optimization, the optimal formulation was identified as P 15 M 6 T 39 H 40 (mass ratio). Experimental results indicate that the P 15 M 6 T 39 H 40 system exhibits a cyclic CO 2 capacity of 2.1 mol/kg. The viscosity of the rich phase in the P 15 M 6 T 39 H 40 system at 30 °C is as low as 18.76 mPa·s, and the regeneration energy consumption is 2.75 GJ·t −1 CO₂, representing a 27.6% reduction relative to the conventional 30 wt% MEA system. Furthermore, 13 C NMR analysis and density functional theory (DFT) calculations confirmed that the driving force for the liquid-liquid phase transition primarily arises from the polarity difference between the product and the solvent. Cycling experiments demonstrated that the P 15 M 6 T 39 H 40 phase change absorbent developed in this study exhibits excellent cycling stability and holds significant potential for industrial CO 2 capture applications. Download: Download high-res image (186KB) Download: Download full-size image