Study on the CO2 Absorption Performance of an AEP + DEGDME + H2O Phase-Change Absorbent

CO₂ capture, utilization, and storage (CCUS) is recognized as a pivotal approach for meeting the net-zero carbon emission targets of the international shipping industry. However, developing high-performance carbon-capture absorbents that can minimize the equipment size and reduce the energy consumption of the carbon-capture process is challenging. Based on the characteristics of polyamine molecules (aminoethylpiperazine (AEP)), which have a heterocyclic structure and exhibit high boiling point, good stability, and low reaction enthalpy, as well as the advantages of low viscosity and low volatility of alcohol ether solvents, this study investigated the absorption and desorption performance of the AEP + bis(2-methoxyethyl)ether (DEGDME) + H₂O (A–D–H) ternary phase-change system. Absorption experiments were conducted to optimize the ternary component ratios, revealing that an absorbent formulation of 20 wt % AEP + 40 wt % DEGDME + 40 wt % H₂O achieved a CO₂ absorption efficiency of 49% at 50 °C. This formulation demonstrated a rich-phase load of 2.42 mol CO₂ kg^–1 and a viscosity of 12.69 mPa s, with an average absorption rate of 0.0429 mol CO₂ kg^–1 min^–1. Desorption experiments showed that the desorption temperature and solid acid catalysts greatly influence the desorption performance. When the desorption temperature was 120 °C, the A–D–H system exhibited a desorption load of 1.96 mol CO₂ kg^–1 and a desorption efficiency of 81.04%. Incorporation of the 6 wt % γ-Al₂O₃ catalyst increased the desorption efficiency of the A–D–H system to 98.34%. Energy consumption calculations showed that the regeneration energy for the A–D–H system was 2.8 GJ t^–1 CO₂, which was 70.7% of the energy required for the regeneration of the 30 wt % MEA solution. ¹³C nuclear magnetic resonance spectroscopy was used to elucidate the absorption and desorption mechanisms of the A–D–H absorbent.