Optimized separation of FAME from soybean oil: a route to biodiesel with superior cold-flow properties

Abstract

This study presents the optimization of an innovative urea complexation method for efficiently separating fatty acid methyl esters (FAMEs) from soybean oil to obtain a high-purity biodiesel as the main product. Operating parameters, including urea-to-FAMEs mass ratio (0.5:1–1.5:1), crystallization temperature (4 °C and −5 °C), and time (2–24 h), were evaluated, and the optimal conditions were identified as a 0.75:1 ratio with crystallization at 4 °C for 2 h. This process yielded biodiesel which was highly enriched in C18 methyl esters (~100%), meeting international quality specifications and showing excellent cold-flow behavior, with a cloud point of −15 °C and superior filterability for low-temperature engine operation. Additionally, a C16-enriched fraction suitable for methyl ester sulfonate production was obtained, offering a sustainable alternative to palm-oil-derived inputs. Overall, urea complexation provides an efficient, eco-friendly, and economically attractive alternative to fractional distillation for producing cold-resistant biodiesel and green surfactant feedstocks.