Sustainable aviation fuel (SAF) from lignin: Pathways, catalysts, and challenges

The aviation industry plays a crucial role in global trade and cultural exchange, but it faces significant challenges due to high production cost and environmental impacts. To achieve carbon neutrality, promoting the development of sustainable aviation fuel (SAF) is essential, with projections indicating that 65% of emissions reductions in the aviation industry by 2050 will come from the use of SAF. Lignin, as an abundant renewable resource, has great potential for conversion into aviation fuel components. It can be depolymerized and/or hydrodeoxygenated (HDO) to produce C6-C9 alkanes. However, to produce high-density SAF, lignin monomers need to undergo coupling, alkylation, and transalkylation reactions to extend the carbon chain to C8-C16 precursors, which can then be converted into long-chain alkanes suitable for SAF through HDO reactions. This paper reviews the research progress on synthesis of lignin-based SAF, highlights key synthetic methods, and analyzes how catalyst and reaction conditions affect the synthesis pathways, efficiency, and properties of SAF. Additionally, the obstacles and challenges hindering the development of biomass-based SAFs are discussed to provide theoretical support for future research in this field.