(205b) Two-Stage Hydroconversion of Algal Oil to Sustainable Aviation Fuel (SAF)

Research into Sustainable Aviation Fuels (SAFs) continues to gain interest as an alternative fuel for decarbonizing the aviation sector. The US government’s initiative, the SAF Grand Challenge, aims to spur research and industry towards the production of 35 billion gallons of SAF annually by 2050. Unlike other energy sources which require extensive infrastructure changes, SAFs adhere to ASTM specifications for jet fuels, making them compatible with current infrastructure. Amidst the biojet fuel technologies under development, leveraging microalgae shows promise due to their rapid proliferation rates and high oil yields. This study explores a novel pathway for converting algal lipids to SAF via a two-stage hydrodeoxygenation-isomerization process. In the first stage, hydrodeoxygenation is conducted to reduce the oxygen content, followed by the isomerization of linear alkanes to meet jet fuel specifications, in the second stage. Algal oil feedstock was extracted from concentrated algal slurry, and Fatty Acid Methyl Ester (FAME) analysis on algal oil shows that long fatty acid chains ranging from C₁₃ to C₂₀ are predominant. Therefore, for the hydrodeoxygenation step, analysis of the liquid product focused on the formation of these C₁₃ to C₂₀ hydrocarbons. Hydrodeoxygenation experiments were carried out on varying concentrations of algal oil in dodecane for different process variables. Catalysts employed were presulfided NiMo catalyst, a conventional hydrotreating catalyst, and precious metal-based catalysts: 1% Pt/Al₂O₃ and 0.5% Rh/Al₂O₃. Results indicated higher yields at lower oil concentrations, with the precious metal-based catalysts having a superior performance compared to the NiMo catalyst. Plans are underway to advance to the second stage using an isomerization catalyst, and evaluation studies will be conducted to identify the optimal process conditions for high product yields. Overall, the successful hydrodeoxygenation step validates the feasibility of microalgae-based biojet fuel through a two-stage approach and highlights the potential of commercial-scale production of SAF using microalgae.