Physicochemical Properties, Interaction Analysis, and CO₂ Capture Capacity for the Binary Mixtures of Ethylene Glycol and 1,3-Propanediamine

In this study, the density (ρ) and viscosity (η) of the mixed solvent of ethylene glycol (EG) and 1,3-propanediamine (1,3-PDA) were experimentally measured over a temperature range of 293.15–318.15 K under an experimental pressure of 100.5 kPa. From these measurements, the excess molar volumes (VmE), partial molar volume (V̅), excess activation Gibbs energy (ΔG*E), and coefficient of thermal expansion (αp) of the binary mixtures were derived. The Redlich–Kister (R-K) equation was employed to fit the data for excess molar volume (VmE), viscosity deviation (Δη), and excess activation Gibbs energy (ΔG*E). Strong hydrogen bonding interactions between EG and 1,3-PDA were confirmed through spectroscopic analyses and density functional theory (DFT) calculations. Furthermore, the binary mixture exhibiting the strongest intermolecular interactions demonstrated an exceptional CO2 uptake capacity of up to 0.98 mol of CO2/mol of PDA, significantly higher than the 0.49 mol of CO2/mol of PDA observed for pure 1,3-PDA. This enhancement in CO2 absorption can be attributed to the strong hydrogen bonding interactions that suppress the volatility of 1,3-PDA.