Thermophysical characterization of a new potential bio-oxygenate fuel formed by hexane, ethanol and diethyl carbonate

Abstract

The thermophysical characterization of a new potential bio-oxygenate fuel formed by ethanol, diethyl carbonate, and hexane is carried out by the direct determinations and theoretical predictions of the selected fundamental thermophysical properties (i.e., vapor–liquid equilibria, dynamic viscosity, and surface tension) over the entire mole fraction range. Specifically, vapor–liquid equilibria (VLE) are reported at 94.00 kPa, over 330.0 K to 356.0 K, while liquid dynamic viscosity and surface tension are explored at 298.15 K and 101.3 kPa. The experimental VLE are modeled using the Perturbed Chain Statistical Associating Fluid Theory Equation of State (PC-SAFT EoS), which accounts for hydrogen bonding interactions between alcohol molecules and cross-interactions with the negative sites on the diethyl carbonate molecule. For the other two reported properties, the PC-SAFT EoS is coupled with free-volume theory and linear gradient theory, respectively. The advantage of this combined approach is that all required parameters are obtained from the corresponding pure fluids and binary mixtures that form the ternary mixture; therefore, the thermophysical properties of the ternary mixture are completely predicted. Based on experimental determinations and theoretical modeling, the VLE of the ternary mixture exhibits a positive deviation from Raoult's law, indicating zeotropic behavior under the conditions explored. The dynamic viscosities and surface tension display a monotonic behavior with the mole fraction. Finally, the combination of experimental measurements and molecular-based theoretical model provides a reliable framework to predict with physical sound and good accuracy these thermophysical properties over a broad range of temperature, pressure, and mole fractions that can be safely used to carry out further evaluations related to the use of this oxygenate fuel in complementary engine tests.