Surface Tension and Viscosity of Ternary Mixtures of N‑Methyldiethanolamine + Sulfolane + Water

A ternary mixture of N-methyldiethanolamine + sulfolane + water called Sulfinol-M is usually used as an absorbent to remove acid gas species from natural gas. The surface tension and viscosity of N-methyldiethanolamine + sulfolane + water ternary mixtures with different compositions in the temperature range from 298.2 to 323.2 K were measured at atmospheric pressure. The surface tension of the mixed solution decreased linearly with the increasing temperature. The surface tension deviation was negative and increased with the decrease of the water content in the solutions. The viscosity–temperature dependence was nonlinear and conformed to an extended Arrhenius equation. When the concentration of N-methyldiethanolamine was ≤50 wt %, the viscosity deviation was negative and increased with the increasing temperature. For the surface tension of ternary mixtures, the average absolute relative deviation (AAD%) values of the simplified extended Wilson model and the simplified FLW model were 0.69 and 1.37, respectively. The modified Grunberg–Nissan model and Jouyban–Acree model were used to correlate the viscosity data, and the AAD% values were 3.26 and 8.61, respectively.