“Concentration” of the CO2-rich phase in the PZ/DEEA/NPA system for CO2 capture: Solvation effect

Biphasic absorbents are regarded as highly promising absorbents for carbon dioxide (CO 2 ) capture, owing to their potential energy savings and facile separation. This study introduces a novel piperazine (PZ)/2-(diethylamino)-ethanol (DEEA)/n-propanol (NPA) biphasic absorbent, in which the addition of NPA to the PZ/DEEA binary system results in a doubling of absorption rate, a reduction of the lower phase volume by over 50% to just 28.77% of the total volume, and a CO 2 enrichment level of up to 95.59%, achieving rich phase concentration. Furthermore, the PZ/DEEA/NPA absorbent exhibited excellent absorption-desorption stability and a high desorption efficiency (~ 90%), with a regeneration heat approximately 31% lower than that of benchmark monoethanolamine (MEA). NMR and molecular simulation analyses indicate that NPA's weak competitive solvation effect reduces dispersive interactions with CO 2 absorption products, thereby indirectly strengthening hydrogen bonding of products. This facilitates dense aggregation, resulting in a volumetrically contracted, high-concentration solid product during the final absorption stages. Additionally, corrosion assessments indicate that both fresh and CO 2 -saturated absorbents demonstrate extremely low corrosion rates, favoring industrial implementation. In conclusion, the PZ/DEEA/NPA biphasic absorbent proves to be a potential alternative to the conventional MEA for sustainable CO 2 capture.