Density and Viscosity in Biodiesel + Diesel Mixtures from Recycled Feedstocks

The objective of this work was to study the volumetric and transport properties of mixtures made up of biodiesel and diesel, in order to meet the desirable properties of these formulations for their practical applications. The volumetric and transport properties were analyzed for two pseudobinary mixtures constituted of diesel + beef tallow butyl ester biodiesel and diesel + waste cooking oil methyl ester biodiesel in the whole range of composition at 0.078 MPa. The study of butyl ester biodiesel was motivated by the scarcity of these properties’ data for butyl esters and the improvement of some of its physicochemical properties. The biofuels were previously transesterified from waste materials and alcohols, beef tallow with 1-butanol and cooking oil with methanol. Density measurements were performed in a vibrating tube densimeter from 293.15 to 363.15 K; the kinematic viscosity experiments were carried out in Cannon-Fenske viscometers from 293.15 to 343.15 K. The derived thermophysical properties evaluated were the excess molar volume, the partial molar volume, the thermal expansion coefficient, the dynamic viscosity and the viscosity deviation. The excess molar volumes presented positive and negative values. The Redlich–Kister correlation and the theoretical ERAS (Extended Real Association Solution) model were applied for modelling the excess molar volume. Both approaches resulted in good agreement. For viscosity, the McAllister model was implemented and yielded lower deviations for the butyl ester biodiesel.