Effects of 2-Butanol Addition on Waste Cooking Oil Biodiesel Density: An Updated Experimental Measurement and Thermodynamic Modeling Study

Abstract

Biodiesels will become the most popular alternative energy resource to fossil diesels; they can be used alone or blended with an oxygenated additive in any proportion. The properties of biodiesels strongly depend on the type of the fatty acid methyl esters (FAME) that compose them. The main objective of the present work is to investigate the influence of 2-butanol addition on the waste cooking oil biodiesel (WCOB), for this fact, the new experimental density data (952 points) of WCOB + 2-butanol binary mixtures over a wide range of composition [seven compositions; 0 ≤ (WCOB) mole fraction x ≤ 1] between 0.1 and 140 MPa and 298.15 and 393.15 K are presented. The experimental data were correlated using Tait and perturbed chain-statistical associating fluid theory (PC-SAFT) equations of state (EoS), to our knowledge, this is the first time that density measurements for the WCOB + 2-butanol mixture are correlated using the famous PC-SAFT EoS. The Tait equation predicts successfully the density with a global absolute average deviation (AAD) of 0.089%, while the PC-SAFT model correlates well the density with a very small global AAD of 0.223% in each composition. Furthermore, contrary to the Tait equation, the PC-SAFT model can explain some interactions between fluid molecules. From the experimental data, the excess volumes VE have been calculated and fitted using the Redlich-Kister equation with a very small global standard deviation of 7.49 × 10-5 cm3 mol-1, and VE show a positive and symmetric parabolic shape in all composition ranges. Finally, the isobaric thermal expansivity, αp, and the isothermal compressibility, κT, have been derived from the Tait equation and their observed trend was as expected.