Catalysis for Sustainable Aviation Fuels: Focus on Fischer‐Tropsch Catalysis

The aviation sector accounts for around 12% of the energy consumption of the entire transport sector and thus contributes significantly to global greenhouse gas emissions. Electrifying this sector, as is being done with cars and other modes of transport, is not an easy task, as batteries are heavy and can compromise an aircraft's power-to-weight ratio. Significant improvement in battery energy density will still be required before electric powered long-haul aviation becomes a reality. Power-to-liquid (PtL) solutions are positioned as future pathways to decarbonize hard to abate transport sectors such as aviation, which is expected to grow significantly in the future. One such solution to produce sustainable aviation fuels (SAF) utilizes Fischer-Tropsch (FT) chemistry to convert green H 2 and sustainable carbon to kerosene-range hydrocarbons. FT chemistry can be used in three main ways to convert a sustainable source of carbon into jet-fuel. The first route involves the gasification of biomass or waste to a synthesis gas (syngas) feed that can undergo a FT reaction to form hydrocarbon products. A second indirect route involves the conversion of CO 2 +green H 2 to CO and water via reverse water gas shift (RWGS). CO produced in this way is then combined with H 2 to produce syngas, which is converted into useful hydrocarbon products over a suitable Fischer Tropsch synthesis (FTS) catalyst, typically cobalt. A third path involves tandem catalysis combining RWGS and FTS, converting the green H 2 and CO 2 directly into a range of products. This can be achieved with iron catalysts that are active for both RWGS and FTS at typical FT reaction conditions. There are several challenges to overcome in applying Fischer-Tropsch catalysts for PtL applications in an efficient and sustainable manner. These include the need to: Move toward greener, efficient methodologies to produce catalysts. Develop catalysts that perform at higher per pass conversions, implying higher reactor water partial pressures, to minimize the need for recycling and to simplify process design. Design a FT catalyst with high selectivity and yields to the desired jet-fuel range hydrocarbons, minimizing the production of light hydrocarbons, thus simplifying product work-up. Understand the performance and deactivation of catalysts in synthesis gas containing impurities that are present in biogenic-derived feedgas. Develop ways to regenerate and re-use catalysts to ensure a circular catalyst lifecycle. The review will focus on elements of these topics as well as future perspectives contributing toward a deeper understanding of the application of FT catalysts to produce SAS.