A key property that limits the full utilization of traditionally biodiesel fuel is its cloud point, or the tendency of refined biodiesels to form crystalline complexes of methyl esters at low temperatures. Low cloud point biodiesel is desirable for cold climates and low temperature applications such as aviation fuel. Previous research has demonstrated that the selective treatment of fatty acid methyl esters (FAME) with urea results in the selective formation of complexes of urea and fatty acids with no or little unsaturation, leaving the remaining fraction of FAME enriched in highly unsaturated fatty acids and subsequently a lower cloud point. These previous methods suffer from limitations for incorporation into industrial processes, included the use of large amounts of urea and high quantities of organic solvents. This work focuses on two main area, the first being to address these limitations of urea complexation on biodiesel final products. Experimental parameters studied included the use of different additives, varying reaction times and temperatures, and varying crystallization temperatures to determine the optimum conditions for generation of low cloud point fractions from commercially produced biodiesel. Additives including solid absorbents and other small organic molecules were shown to facilitate the formation of the urea/FAME complexes, leading to formation of low cloud point fractions. In many case cloud points were reduced 10 to 40 degrees from the starting biodiesel, with the lowest ones comparable to petroleum-based diesel products.  Using the significant results from this study, the second objective was the identification of key points during the industrial biodiesel production process to incorporate urea complexation, with the ultimate goal being to adapt existing biodiesel production methodology to produce a lower cloud point product. Complete results from both these studies will be presented.

Advances in urea complexation for cloud-point reduction of biodiesel

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