More renewable components in diesel fuel could be useful in reducing its environmental impact. However, the resulting fuel mixture needs to be suitable for use in modern diesel engines without, for example, expensive additives. One critical factor for good engine performance, especially at startup, is the boiling point behavior.

Lukas J. Goossen, Ruhr University Bochum, Germany, and colleagues have converted rapeseed oil methyl esters (RME) to biofuel with a boiling point curve that fulfills the specifications for state-of-the-art diesel engines. The team used a three-step process involving sequential semihydrogenation, double-bond isomerization, and metathesis.

In the first step, polyunsaturated esters were semihydrogenated in the presence of a solvent-stabilized Pd⁰ colloid. The resulting mono-unsaturated fatty esters were further converted into a defined mixture of double-bond isomers by passing them over an inexpensive, Brønsted-acidic Amberlyst resin. The resulting mixture was then converted into a blend of terminally unsaturated olefins and monoesters by cross-metathesis with ethylene, using a cyclic alkyl amino carbene (CAAC)-based ruthenium catalyst.

All three steps were conducted with neat feedstock at relatively low temperatures (60–100 °C). Overall, the work demonstrates that sustainable diesel fuel for use in contemporary diesel engines can be obtained from RME and ethylene via industrially viable reaction steps.

• Sustainable diesel from rapeseed oil esters by sequential semi-hydrogenation, double bond isomerization, and metathesis,
  Mykhailo Kondratiuk, Maximilian L. Spiekermann, Thomas Seidensticker, Lukas J Goossen,
  Chem. Eur. J. 2025.
  https://doi.org/10.1002/chem.202500523