Harnessing the synergies between lipid-based crystallization modifiers and a polymer pour point depressant to improve pour point of biodiesel.

A series of binary mixture additives made of a pour point depressant (PPD) and a vegetable oil based crystallization modifier (VOCM) have been used to substantially improve the cold flow performance of fatty acid methyl esters (FAME) of soybean oil (Soy1500). An apparatus improving on the ASTM methods was designed to measure the cloud point (CP) and pour point (PP). The mixtures dramatically altered Soy1500 crystallization from nucleation to aggregation, and delivered PP depressions reaching 30 °C. The effect was confirmed to be due to synergistic effects wherein the VOCM delays the nucleation by first combining with the saturated FAME of the biodiesel then growing structure specific crystal surfaces that effectively adsorb the PPD which provides barriers to agglomeration. The VOCM-PPD mixture constrains the biodiesel microstructure to very small crystals that are prevented from aggregating over an extended temperature range, leading to a significant depression in the PP. The most dramatic effects were achieved when the PPD is combined in optimal concentration with a VOCM having a structural element which initiates packing and another that prevents further crystallization. Importantly, the results and understanding gathered from the study can be used for the design of highly functional cold flow improver cocktail additives. [ABSTRACT FROM AUTHOR]