Diamine-based water-lean absorbent for CO₂ capture: Performance and molecular dynamics insights

Achieving carbon neutrality requires efficient, energy-saving carbon dioxide capture technologies. Conventional monoethanolamine (MEA) solutions suffer from high energy consumption, volatility, and degradation. This study develops a diamine-based water-lean solvent, consisting of 2-ethylhexylamine (EHA), N,N-dimethylethylenediamine (DMEDA), and dimethyl sulfoxide (DMSO), and evaluates its CO₂ capture performance. The EHA-based solvent achieved a CO₂ absorption capacity of 3.7 mol/kg and a rate of 1.83 mol/kg·s, outperforming Aminoethyl Ethanolamine (AEEA)-based and MEA-H₂O solutions. Regeneration energy was reduced by 65 %, with activation energies of 31.2 kJ/mol (EHA) and 33.15 kJ/mol (AEEA). Molecular dynamics (MD) simulations revealed enhanced CO₂ diffusion and solvent stability due to optimized bond length distribution. DMSO improved mass transfer, mitigated viscosity resistance, and stabilized carbamate formation. Fourier transform infrared (FTIR) spectroscopy confirmed that water-lean systems favored carbamate selectivity over bicarbonate formation. These findings demonstrate the industrial potential of EHA-based solvents for high-emission scenarios, offering reduced energy use and improved process stability. This work provides a framework for designing efficient, low-viscosity solvents for sustainable CO₂ capture.