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 k_ij. Increasing the order of the temperature function of k_ij 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 k_ij 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%.