Thermodynamic Properties of 1-Butanol + Ethyl Laurate Binary Mixtures by Combining Experimental Speeds of Sound with Volume Translated Peng–Robinson Equation of State

The speeds of sound in 1-butanol + ethyl laurate binary mixtures determine the injection time and combustion characteristics of diesel engine. The speed of sound of 1-butanol + ethyl laurate binary mixture system was measured by the Rayleigh–Brillouin light scattering method at temperatures from 293 to 520 K and pressures from 0.1 to 7.5 MPa. A set of parameters was fitted using 1-butanol and ethyl laurate experiment data for the volume-translated Peng–Robinson (VTPR-BE) equation of state (EoS), taking into account the temperature influence on the binary interaction parameter kij. Increasing the order of the temperature function of kij can reduce the calculation deviation of the VTPR-BE EoS. However, beyond the second-order term, further increases in order do not yield significant improvements in accuracy. By adopting the second-order kij form, the density and the speed of sound of 1-butanol + ethyl laurate binary mixture system were calculated using the VTPR-BE EoS. The average absolute relative deviation is 1.05% for density and 3.90% for the speed of sound. Especially, when the molar fraction of 1-butanol is 0.5, the absolute relative deviation of the speed of sound is 1.79%.