Application of Surface-Active Amines for CO ₂ Capture from Low-Purity Sources

Surface-active tertiary amines have recently emerged as promising solvents for CO2 capture by promoting bicarbonate formation in aqueous media. This paper presents the systematic evaluation of a new class of surface-active amines, N-xPO (x = 4, 6, 9, 12, and 15), under experimental conditions relevant to industrial scenarios, such as low-purity CO2 streams and high-concentration amine solutions. A structure-performance relationship governing solubility, surface tension, and bicarbonate production was studied by modifying the propylene oxide (PO) chain length. Results indicated that N-4PO achieved an optimal balance between surface activity and water solubility, enabling reactions at high amine concentrations (1.6 mol/L, 40 wt %) for diluted CO2 sources. N-4PO demonstrated effective bicarbonate production across CO2 concentrations ranging from pure to dilute streams (3.5% CO2). The maximum bicarbonate concentration reached 1.09 mol/L, equivalent to a loading capacity of 0.119 g CO2 per gram of N-4PO. Moreover, N-4PO produced approximately 50% more bicarbonate with faster kinetics than 3-(dimethylamino)-propylamine-6-propylene oxide (DMAPA-6PO) for a CO2 concentration of 3.5%, in which its single tertiary amino group promoted faster mass transfer and protonation kinetics at the gas–liquid interface. This study presents a practical, structure-focused approach to designing efficient surface-active amines for next-generation carbon capture solvents.