The main criterion for sustainable aviation fuels is that no modifications to aircraft engines or other infrastructure are required. This means that the chemical composition should be very similar to that of conventional kerosene: a mixture of aromatics, cycloalkanes, iso-alkanes and n-alkanes with chains between 8 and 18 carbon atoms – the C9-15 fraction being particularly important for aviation fuels.

Airlines also want to reduce the proportion of aromatics in the blend because they contribute to condensation, soot formation and particulate emissions. Bert Sels’ group (KU Leuven), together with researchers from TotalEnergies, looked at alternative methods to produce sustainable aviation fuels based on lignin oil.

Reductive Catalytic Fractioning (RCF) produces lignin oil with a high oxygen content, which makes it unsuitable as a fuel. One possible solution is catalytic hydrodeoxygenation (HDO), which reduces the oxygen content of the oil. Several studies have shown the effectiveness of HDO, but in Leuven they have now looked more closely at the properties of the lignin source in the end product. This involved using a Ni₂P/SiO₂ catalyst in the refining process.

The results are promising: eucalyptus, poplar and pine oils yielded 91%, 84% and 75% respectively. In addition, high selectivity was achieved for the desired C9-15 fraction (70%, 60% and 62%, respectively).

The Leuven research shows that it is important to study the properties of lignin oil prior to the refining process. By focusing on the properties of the specific biomass source, more efficient and effective routes to sustainable aviation fuels can be developed.

Bruno Pandalone, et al., Optimum lignin oil — Finding the most suitable feedstock to replace cycloalkanes in sustainable aviation fuel (SAF), ChemSusChem (2025), doi:10.1002/cssc.202402531