Density, Viscosity, and Surface Tension of Aqueous 1‑Methylpiperazine and Its Carbonated Solvents for the CO₂ Capture Process

Physicochemical properties of amine solutions like density, viscosity, and surface tension results are indispensable for designing carbon dioxide (CO₂) absorption and regeneration columns, and they are also crucial for modeling and simulation for CO₂ capture applications using the postcombustion capture method. In the present work, the density and viscosity of 1-methylpiperazine (1-MPZ) solution are studied for the temperature range of 298.15 to 348.15 K. Surface tension measurements for temperatures ranging from 303.15 to 348.15 K are reported for various concentrations of 1-MPZ. To validate the instrumental accuracy and procedure, properties of aqueous 0.3 weight fraction (w) monoethanolamine (MEA) were first measured and compared with reported results before the study of 1-MPZ. The weight fraction of 1-MPZ was kept at 0.1, 0.2, 0.3, and 0.4 for the physical property study of unloaded aqueous 1-MPZ, and 0.3w was considered for CO₂-loaded properties. The 1-MPZ solution was loaded with CO₂ up to 0.45 mol CO₂/mol amine. The Redlich–Kister equation for excess molar volume was used to correlate the measured density of the fresh and CO₂-loaded solvents. The viscosity data of unloaded aqueous 1-MPZ and CO₂-loaded aqueous 1-MPZ were correlated using the Grunberg–Nissan and modified Weiland models, respectively. Surface tension results of fresh and CO₂-loaded 1-MPZ were fitted by a polynomial function. These new data and models are helpful for the design of postcombustion CO₂ capture using 1-MPZ-based solvents and their blends.