Study of Density, Surface Tension, and Refractive Index of Binary Mixtures Containing Alkyl Levulinate and n-Alcohol from 298.15 to 323.15 K

Abstract

Alkyl levulinate, prepared from the esterification of levulinic acid and n-alcohol, has the potential to be used as a fuel additive. Alcohol has also been used as an additive in fuel to improve ignition and combustion characteristics to a certain extent. For this reason, the properties of mixtures containing these compounds are of particular interest. Herein, measurements of density (ρ), surface tension (γ), and refractive index (n) were conducted for three binary mixtures of methyl levulinate–methanol (ML–M), ethyl levulinate–ethanol (EL–E), and n-butyl levulinate–butanol (BL–B). These properties were measured over the entire range of compositions in 0.1 increments of the molar fraction of the components in the temperature range of T = 298.15–323.15 K and at an atmospheric pressure of p = 0.1 MPa. The experimental data were used to calculate the excess and deviation properties, that is, excess molar volumes (VmΕ), surface tension deviations (Δγ), and molar refraction deviations (ΔR). The VmΕ, Δγ, and ΔR values were fitted to the Redlich–Kister polynomial equation. The VmΕ and ΔR values were negative for all compositions, whereas Δγ exhibited both negative and positive values at different compositions. The molecular interactions of the binary mixtures are discussed from these excess and deviation functions. Furthermore, the Jouyban–Acree model was used for the correlation of properties: density, surface tension, and refractive index of the studied mixtures at different temperatures (T = 298.15–323.15 K). The results are expected to provide fundamental data for understanding the properties of alkyl levulinate as a potential bio-based fuel additive.