Binary Mixtures of n-Alkylbenzenes and Pentadecane: Densities, Speeds of Sound, and Viscosities within the Range of 288.15 and 333.15 K and at 0.1 MPa

The physical properties of mixtures of alkanes and aromatic compounds can aid in the understanding and modeling of their combustion in engines. Herein, densities, viscosities, and speeds of sound of binary mixtures of n-alkylbenzenes with pentadecane and their corresponding excess molar volumes (V_m^E), excess speeds of sound (c^E), excess isentropic compressibilities (Κ_s^E), and viscosity deviations (Δη) are reported. In general, mixture densities, viscosities, and speeds of sound increased monotonically with changing mole fractions, except for the speeds of sound of toluene, ethylbenzene, propylbenzene, and butylbenzene mixtures. These properties can be used for fuel modeling purposes. V_m^E’s, Δη’s, c^E’s, and K_s^E’s ranged from 0.04 to 0.56 cm·mol^–1, −0.14 to 0.09 mPa·s, −14.8 to 2.5 m·s^–1, and −2.2 to 18.1 TPa^–1, respectively. Increasing the n-alkylbenzene size (up to decylbenzene) caused the equimolar mixture’s V_m^E’s, Δη’s, and K_s^E’s to decrease and c^E’s to increase at 293.15 K. The properties of smaller n-alkylbenzene molecules were more affected by the aromatic group. In comparison with n-alkylcyclohexane/pentadecane mixtures, n-alkylbenzene/pentadecane mixture Δη trends were similar, but V_m^E’s, c^E’s, and K_s^E’s trends were different, suggesting that molecular interactions of the benzyl and cyclohexyl groups affect volume and compressibility more than they affect viscosity.