Development of aqueous-based phase change amino acid solvents for energy-efficient CO₂ capture: the role of antisolvent

The energy penalty is a primary limitation for the implementation of the aqueous solvents for large-scale post-combustion CO₂ capture processes. In this study, a novel aqueous-based phase change solvent, composed of potassium glycinate (GlyK, reactive species), water (H₂O, solvent) and dimethylformamide (DMF, antisolvent) was developed to improve the energy efficiency of CO₂ capture. To examine the role of the antisolvent, a series of aqueous-based amino acid solvents (GlyK-X) with different DMF:H₂O (X) volume ratios was prepared, fully characterized and assessed. It was observed that a CO₂-free phase appeared at the top of the aqueous-based amino acid GlyK-X solvents after CO₂ absorption which can be easily separated and recycled to the absorption column and save energy. The results showed that the GlyK-60 solvent with DMF:H₂O volume ratio of 60:40 had a very high CO₂-free phase volume (63%). Moreover, the GlyK-60 solvent exhibited 26.1% (0.433–0.546 mol CO₂/mol GlyK) enhancement in CO₂ absorption capacity, 38.5% (130–80 min) decrease in regeneration time and 59.1% reduction in relative heat duty compared to the conventional aqueous GlyK solvent. Overall, the outcomes confirmed that the aqueous-based phase change GlyK-60 solvent is a viable solvent option for large-scale CO₂ capture with extra-low energy consumption and a key to the success of Paris Climate Accord.