A new two-stage catalytic process selectively converts lignin to jet-range aromatics at unprecedented carbon yields and offers a route toward a 100% drop-in sustainable aviation fuel (SAF).

Jet fuel is a blended mixture of different hydrocarbon molecules, including aromatics and cycloalkanes. Current commercialized technologies do not produce those components to qualify for a 100% SAF. Instead, SAF blendstocks are combined with conventional hydrocarbon fuels. As the largest source of renewable aromatics in nature, lignin could hold the answer to achieving a complete bio-based jet fuel.

Schematic of the lignin hydrodeoxygenation process. Source: Michael L. Stone et al./JouleSchematic of the lignin hydrodeoxygenation process. Source: Michael L. Stone et al./Joule

This biopolymer is recalcitrant to oxygen removal, preventing its exploitation in jet fuel. Researchers from the U.S. National Renewable Energy Laboratory, Massachusetts Institute of Technology and Washington State University have demonstrated an efficient method based on abundant molybdenum carbide as the catalyst in a continuous process, achieving an oxygen content of about 1%. The process effectively deoxygenated lignin from poplar into aromatic hydrocarbons with 87.5% selectivity toward aromatic hydrocarbons at 86% of the theoretical carbon recovery.

The lignin pathway outlined in Joule allows the produced SAF to have fuel system compatibility at higher blend ratios.

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