Keywords: Surface tension Long-chained hydrocarbon mixtures Pendant drop method Modelling

This work contributes to the experimental measurements and modelling of the surface tension for the medium-to long-chained hydrocarbon mixtures involved in the Fischer-Tropsch process under the high-temperature con-ditions. For this purpose, the experimental surface tension measurements for the four investigated binary mix-tures of n-Hexadecane with n-Dodecane, 2,2,4,4,6,8,8-Heptamethylnonane, n-Octacosane and Squalane were performed by pendant drop method at temperatures up to 573.15 K covering the mass fractions of wn-Hexadecane = (0.25, 0.50 and 0.75). The combined expanded uncertainties of temperature, mole fraction and surface tension with a level of confidence of 0.95 (k = 2) are estimated to be 20 mK, within 0.6% and less than 2.2% over the entire temperature, respectively. On the basis of the surface tension correlations of pure substances in our previous study, the experimental surface tension data of the four investigated binary mixtures were correlated with the three-parameter Jouyban -Acree model and two-parameter Fu-Li-Wang (FLW) model. However, the experimental results show increasing negative deviations from Jouyban -Acree model with maximum values up to-2.66% and increasing positive deviations from FLW model with maximum values up to 9.93% in the high temperature zone. Therefore, we proposed a new model for correlating the surface tension of multicomponent mixtures with excellent reproducibility. The relative deviations of the experimental data from the present model are distributed evenly on both sides of the zero line and the relative absolute deviations are within 0.6%.