Experimental and Modeling Investigations of Density and Viscosity for the Ternary (N-Octane + Ethylcyclohexane + Ethylbenzene) Mixtures

Biofuels are increasingly recognized as the most practical way to reduce carbon dioxide emissions and pollution in the transport industry. However, the production and promotion of biofuels have encountered many obstacles due to their complex composition and the ambiguity in studies on the physicochemical properties. To achieve a thorough comprehension of biofuel density and viscosity properties, developing suitable surrogate mixtures is an accurate and efficient method. N-Octane, ethylcyclohexane, and ethylbenzene are important components of biofuel surrogate mixtures to reflect the thermophysical properties of three primary hydrocarbons (alkanes, cycloalkanes, and alkylbenzenes). Therefore, the liquid density and viscosity of ternary mixtures (n-octane + ethylcyclohexane + ethylbenzene) are measured using a vibrating-tube densimeter and vibrating-wire viscometer, respectively, over the temperature range from 283.15 to 363.15 K and at pressures of up to 60 MPa. Moreover, the excess volume and viscosity deviations of the mixtures were obtained. For density, the group contribution (GC) PC-statistical associating fluid theory (PC-SAFT) equation of state (EoS) and SAFT-γ Mie EoS have been compared to assess the effect of different interaction potential functions on the prediction of liquid-phase densities. The results showed that the SAFT-γ Mie EoS gave the best prediction, followed by the GC PC-SAFT EoS. In terms of viscosity, a new mapping law for effective molecular weight has been developed to improve the predictive accuracy of the 1-cEHS model, and the absolute average deviations (AAD%) are 3.3–5%. In addition, excess molar volumes and viscosity deviations in this work are derived and discussed to further explore the influence of different molecular structures on thermophysical properties.