Proposing blends for improving the cold flow properties of ethylic biodiesel

Abstract

Despite the several advantages compared to conventional diesel fuel, the biodiesel has poor cold flow properties, limitng its use as a fuel in moderate and cold climates. Considering that the fatty esters profile and the alcohol used affect the biodiesel physico-chemical behavior, this work explored the crystallization/melting profiles of ethyl biodiesel from different oil sources as well as of binary blends among them to improve their cold flow properties. Therefore, model ethyl biodiesels from soybean oil, beef tallow, palm oil, their fractions, olein and stearin, palm kernel, macauba, and macauba kernel oils were formulated by pure ethyl esters, their melting/crystallization temperature, cloud point, pour point, cold filter plugging point and the fraction of crystallized esters analysed. For all cases, blends decreased the cold flow properties of the heavier biodiesel. Soybean oil and tallow biodiesels, economically relevant sources, presented a CFPP of −4.28 °C and 17.12 °C, respectively, whilst some alternative sources, such as macauba and palm kernels biodiesels, presented values lower than −15 °C, which is more advantageous in cold climates. Tallow biodiesel was the only not in accordance with Regulation Agencies considering cold climates. Macauba and palm kernel oils were especially interesting to decrease the melting/crystallization temperatures of heavier biodiesels, including those from tallow beef. The best blend was those formulated with soybean and macauba kernel oils with a CFPP lower than −20 °C. This work suggested that not only biodiesels mainly composed by unsaturated esters but also by short-saturated esters could significantly improve the cold flow properties of high saturated biodiesel, being a low-cost and feasible alterative.