Fundamental properties and intermolecular interaction of triethylene glycol + ethylenediamine aqueous solution for CO2 capture

Abstract

Solvent absorption as a significant method for carbon dioxide capture, exploring the mechanism of CO2 capture and regeneration solvents is essential for industrial applications. In this work, water (H2O) + (ethylenediamine (EDA) + triethylene glycol (TEG)) system with the constant mole ratio (TEG: EDA = 1: 1) was chosen as the liquid absorbent. In order to gain a deeper comprehension of solution properties of H2O + (EDA + TEG) system, the density (ρ) and viscosity (η) of fundamental properties were measured at P = 1005 hPa and T = (298.15 K to 318.15 K) with the temperature step of 5 K. The excess properties, including excess molar volume (VmE), viscosity deviation (Δη), and excess Gibbs energy of activation of viscous flow (ΔG*E) of H2O + (EDA + TEG) system were calculated from the experimental ρ and η values, and fitted well with the Redlich-Kister polynomial equation. The above results combined with the spectra proved the existence of intermolecular interaction in H2O + (EDA + TEG) system, which favorably fixed CO2. Subsequently, the aqueous solution with mass fraction of 15 wt% EDA and molar ratio EDA: TEG = 1: 1 was used for absorbing CO2 (room temperature) and desorbing (378.15 K) for 5-time cycles, and the cycling absorption performance decreased. So as to explore the reason of degradation, Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, and nuclear magnetic resonance carbon spectroscopy (13C NMR) were used to analyze the circulating absorption mechanism of CO2 in H2O + (EDA + TEG) system, which revealed that alkyl carbonates and partially indecomposable substance 2-imidazolidinones generated in the cyclic process, and provided some implications for the industrial application.