Experimental and Speciation Analysis of Biphasic TETA/TMEDA Blend for CO₂ Capture

Biphasic solvents show promise for CO₂ capture due to lower energy consumption but face challenges like high regeneration energy and phase separation instability. This study introduces a biphasic aqueous solvent system with triethylenetetramine (TETA) and tetramethylethylenediamine (TMEDA). The effects of TETA:TMEDA ratios on CO₂ absorption, viscosity, density, and phase separation were tested at various temperatures and compared to 5 M mono-ethanolamine (MEA). The optimal 1.5 M TETA:2.5 M TMEDA at 40 °C captured 0.72 mol CO₂ mol⁻¹ amine, with 84 % CO₂ in the lower phase. Desorption at 90 °C achieved 0.43 mol CO₂ L⁻¹, improving cyclic capacity by 62 % over MEA. The solvent required 2.77 GJ t CO₂⁻¹ for regeneration, 22 % less than MEA. Nuclear magnetic resonance (NMR) analyses elucidated reaction mechanisms and phase behavior. Stability was confirmed by over 10 absorption–desorption cycles.