Critical Volumes of Biodiesel-Related Esters: An Indirect Approach to Evaluating Estimation Models

Knowledge of critical properties of biodiesel components is essential for designing processes involving biodiesel and its mixtures. In a previous work (Ind. Eng. Chem. Res. 2018, 57, 8552–8565), we evaluated group contribution methods for estimating critical temperatures and pressures of fatty acid alkyl esters (FAAEs) and recommended feasible values of these properties for engineering applications. In this study, we analyze models for estimating critical molar volumes (V c ) of FAAEs and identify reliable methods for future use. Because experimental V c data are not available for FAAEs, we propose an indirect evaluation in which the model accuracy is inferred from comparisons of calculated and experimental liquid densities. The results demonstrate that the critical volumes recommended in this work lead to highly accurate density estimates, with an average absolute relative deviation of 0.68% for a database containing 2158 experimental density values for 47 FAAEs, supporting their use in future studies involving biodiesel.