Density, Viscosity, Thermodynamic and Excess Properties, and Intermolecular Interactions of a 1,3-Butanediol + 3-Diethylaminopropylamine Binary System for CO ₂ Absorption

Density and viscosity of a 1,3-butanediol (1,3-BDO) and 3-diethylaminopropylamine (DEAPA) binary system with various molar ratios were measured at atmospheric pressure and a temperature range from 298.15 to 318.15 K. Based on density and viscosity data, the relationship between the system’s density and temperature/composition was studied using the Jouyban–Acree model and nonlinear least-squares. To discuss the connection between the viscosity and molar fraction, the McAllister three-body model, the McAllister four-body model, the Eyring–Margules viscosity model, and the Heric viscosity model were used. The dependence of viscosity on temperature is characterized by the Arrhenius equation. Furthermore, the excess properties (excess molar volume, viscosity deviation, and excess activation Gibbs free energy) of the binary system were fitted using the Redlich–Kister equation. Activation thermodynamic properties (Gibbs free energy, enthalpy, and entropy) of the binary system were calculated. As demonstrated by findings from Raman spectroscopy, nuclear magnetic resonance spectroscopy, fluorescence spectroscopy, and density functional theory calculation, further evidence confirms intermolecular hydrogen bonds in the binary system in the form of –OH···N(H2)–. Finally, the CO2 absorption capacities of the pure components and binary system were measured separately, indicating that adding 1,3-BDO to DEAPA significantly enhances CO2 uptake and provides a promising method for CO2 capture.