Lowering the boiling point curve of biodiesel by cross-metathesis

One of the challenges of today's biodiesel (FAME) is its unsuitable boiling curve behavior. A more or less continuously increasing curve is beneficial because it provides good fuel ignition and combustion in the cylinder of the engine. Here, we present the results of our investigation on the chemical modification of biodiesel with the use of a well-known catalytic reaction, olefin metathesis. Self- and cross-metathesis of biodiesel and 1-hexene were carried out. Ten different ruthenium-based metathesis catalysts were initially subjected to a screening. After selection of the most active catalyst, a series of reactions were prepared wherein the concentration of the biodiesel was held constant, while the amount of 1-hexene was varied. The samples were then analyzed by simulated distillation to determine their boiling curve range. Results revealed that as the hexene amount was increased, a more favorable distillation curve was observed since it generated a fairly good distribution of low to high molecular weight compounds, which in turn exhibited an almost steadily increasing distillation curve, more similar to that of a conventional diesel fuel.