CO2 absorption kinetics and species analysis of DMEDA water-lean absorbents

Traditional aqueous amine-based absorbents face high energy consumption challenges in CO₂ capture processes. Replacing water with organic solvents of low viscosity, low specific heat, and high boiling point in amine-based CO₂ absorbents can effectively reduce the sensible and latent heat required for solvent regeneration. However, the introduction of organic solvents significantly alters mass transfer kinetics and chemical equilibrium, and the quantitative relationship between these effects remains unclear. In this study, water-lean absorbents EFH series with varying organic solvent concentrations were formulated using N , N -dimethyl-1,2-ethanediamine(DMEDA), N , N -dimethylformamide (DMF), and water. Kinetic parameters were measured for DMEDA aqueous solutions, MEA aqueous solutions, pure DMF, and the EFH series. The results revealed an inconsistency between the liquid film mass transfer coefficient ( kₗ ) and viscosity trends, indicating that physical mass transfer dominates the efficiency limitation of DMEDA absorbents under low CO₂ loading, while DMEDA retains sufficiently rapid chemical reaction rates even in water-lean environments. 13 C NMR analysis demonstrated that carbamate species exist as incompletely dissociated ion pairs in aprotic solvent environments. The stabilization of these ion pairs by organic solvents suppresses the generation of neutral carbamic acid, thereby restricting mass transfer and leading to an inflection point in the absorption rate. These findings highlight a dual strategy for optimizing water-lean absorbents: (1) prioritizing low-viscosity, high-CO₂-solubility solvents to enhance initial mass transfer, and (2) tuning solvent polarity or introducing proton donors to sustain reaction efficiency at higher CO₂ loadings. This work provides quantitative mechanistic insights into balancing the trade-off between chemical equilibrium and mass transfer in non-aqueous systems, offering guidance for designing energy-efficient carbon capture solvents.