Investigation on Thermodynamic Properties of Ethanol + Gasoline Blended Fuel

Abstract

The heat capacities (C_p) of ethanol, unleaded gasoline 93^# (where the “93” represents the octane number), and gasohol (which consisted of 10 wt % ethanol and 90 wt % unleaded gasoline 93^#) were measured by adiabatic calorimetry in the temperature range of 80−320 K. For the gasoline, a glass−liquid transition was found at 92.42 K; for the gasohol, a glass−crystal transition and a solid−liquid transition were observed, at 93.17 and 150.86 K, respectively. The enthalpy and entropy of all of the transitions were derived based on the C_p data. For the gasoline, the enthalpy and entropy of the glass-liquid transitions were determined to be 6.80 J g^-1 and 0.0736 J K^-1 g^-1, respectively; for the gasohol, the enthalpy and entropy of the glass−crystal transition were determined to be 9.93 J g^-1 and 0.107 J K^-1 g^-1 , respectively, and the enthalpy and entropy of the solid−liquid phase transition were determined to be 9.99 J g^-1 and 0.0662 J K^-1 g^-1, respectively. The polynomial equations of C_p, with respect to the thermodynamic temperature T, were established through the least-squares fitting. According to the thermodynamic relationship and the equations, the thermodynamic functions of the gasoline and the gasohol, and the excess thermodynamic functions of the gasohol, were derived.