The effect of bio-derived additives on fatty acid methyl esters for improved biodiesel cold flow properties

•Bio-based additives reduce the cloud point of both model and commercial biodiesels.•The mechanisms by which the bio-based additives acted as cloud point depressants are varied.•Thermodynamic modeling satisfactorily predicts the cloud point of a majority of systems examined in this study. Biodiesel is a promising replacement for petroleum based diesel in a number of different applications. Although biodiesel offers numerous advantages over petrodiesel, one of its major disadvantages is its inferior cold flow properties. Additives are often added to biodiesel to remediate issues with cold flow and other problematic properties. This work explored the feasibility of using compounds derived from bio-based sources as an additive for biodiesel. Specifically, the additive’s efficacy in reducing the cloud point of model biodiesels was analyzed using differential scanning calorimetry. Each of the additives studied depressed the biodiesel cloud point, although most of the additives showed diminishing returns above a certain weight percent. For many of the additives, the mechanism of cloud point depression was found to be dilution. For these additives, their efficacy was hampered by self-association, a phenomenon confirmed by thermodynamic modeling. However, tripropionin and dimethyl azelate, molecules of similar size to the FAMEs in the biodiesel studied in this work, interfered with the development of a critical nucleus, causing more significant depressions in the cloud point. Overall, a thermodynamic model based on ideal solution theory was able to accurately predict cloud points for most mixtures studied. Large deviations were observed for systems with significant amounts of self-association and/or cocrystallization.