Monoethanolamine (MEA) and N,N-dimethylformamide (DMF) with fast absorption rate as nonaqueous absorbent for CO2 capture

To address the limitations of amine-based aqueous solutions, nonaqueous mixtures of monoethanolamine (MEA) and N,N-dimethylformamide (DMF) were developed for CO 2 capture. Key factors affecting absorption were systematically investigated, including MEA concentration (10–50 wt%), temperature (30–60 °C), pressure (100–220 kPa) and water content (0–70 wt%). At 30 °C and 140 kPa, the nonaqueous absorbent exhibited a comparable CO 2 absorption capacity to its aqueous solution, while achieving a fivefold increase in absorption rate. Thermogravimetric (TG) analysis revealed that the thermal decomposition temperature of 30 wt%MEA-DMF was 83 °C, which was higher than that of the aqueous solution (70 °C), indicating improved thermal stability. The reaction mechanism was elucidated through Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), pH and conductivity measurements, density functional theory calculations and molecular dynamics simulations. The solvent interactions in water-lean systems were found to impair absorption performance. CO 2 could react with MEA in nonaqueous environments to form carbamic acid, carbamate, and protonated MEA. The DMF component significantly enhanced the absorption rate by facilitating deprotonation. Overall, MEA-DMF solutions had superior CO 2 absorption capacity, faster reaction rate and greater thermal stability, without undergoing phase change. Additionally, the low evaporability, specific heat capacity, and evaporation enthalpy of DMF suggest reduced energy requirements for solvent regeneration. These findings support the potential of MEA-DMF systems as viable alternatives to conventional aqueous amine solutions for CO₂ capture.