Mechanism Investigation of Advanced Metal-Ion-Mediated Amine Regeneration: A Novel Pathway to Reducing CO₂ Reaction...

The high energy consumption of CO₂ and absorbent regeneration is one of the most critical challenges facing commercial application of amine-based postcombustion CO₂ capture. Here, we report a novel approach of metal-ion-mediated amine regeneration (MMAR) to advance the process of amine regeneration. MMAR uses the dual ability of amine to reversibly react with CO₂ and reversibly complex with metal ions to reduce the enthalpy of the CO₂ reaction, thus decrease the overall heat requirement for amine regeneration. To elucidate the mechanistic effects behind MMAR's ability to reduce CO₂ reaction enthalpy, we developed a comprehensive chemical model describing the chemistry of Me(II)-monoethanolamine(MEA)-CO₂-H₂O system. The model was then validated using experimentally determined CO₂ partial pressures via vapor-liquid equilibrium (VLE) measurements. We used the validated chemical model to gain insight into VLE behavior and solution chemistry, and to identify the specific changes in CO₂ reaction enthalpy with and without metal ions. Two metals and five amines were evaluated in detail, which revealed that metal-ions with high complexation enthalpy and amines with large carbamate stability constant are preferred in MMAR, owing to their large reduction in reaction enthalpy and regeneration duty. We anticipate that MMAR could provide an alternative pathway to reducing the energy consumption of absorbent regeneration, ultimately making amine-based processes more technically and economically viable.