Density, speed of sound, refractive index, and hydrogen bonding network in the binary system of N-Methylpiperazine and ethanolamine

This study investigates the thermodynamic behavior and hydrogen bonding network in N -methylpiperazine (NMP) + ethanolamine (EA) binary systems—a promising hybrid amine solvent. Density, speed of sound, and refractive index were measured at 0.1 MPa over 293.15–318.15 K. Excess and deviation properties ( V m E , k s E , and ∆ n ) calculated from experimental data reveal significant non-ideality. V m E exhibits negative deviations, indicating volume contraction driven by strong intermolecular interactions. Molecular dynamics simulations demonstrate that NMP–EA cross-interactions are dominated by O–H···N hydrogen bonds, surpassing van der Waals forces in pure components. FTIR and 1 H NMR confirm hydrogen bond reorganization, with EA's O H stretch shifting. The synergistic hydrogen bonding network enhances molecular packing, providing a mechanistic basis for optimizing low-energy-consumption CO₂ absorbents.