Development of Jet Fuel Components with Ultralow Freezing Points from Biomass-Derived Compounds via Claisen Condensation

Jet fuels must simultaneously meet stringent requirements for energy density and freezing point to ensure safe operation under extreme flight conditions. The common technical route of biojet fuel is hydrodeoxidation after the platform molecule C–C coupling. The branched long-chain alkanes synthesized from biomass-derived C5–C6 esters and ketones platform molecules can meet the performance requirements of jet fuel, via the Claisen condensation as the C–C coupling step. The acetone-derived methyl isobutyl ketone (MIBK) and methyl pivalate were efficiently converted to C11 fuel precursor with branched chain structure over potassium tert-butoxide (t-BuOK) in N,N-dimethylformamide solution. MIBK was fully converted at room temperature for 7 h, with a 95% yield of C11 oxygenated compounds. Under the same conditions, a series of C10–12 oxygenated compounds with a yield around 80% could be synthesized from methyl pivalate and other ketones. In addition, the oxygenated compounds generated alongside the Claisen condensation reaction could serve as jet fuel precursors, thereby ensuring high atomic economy of ketones. After hydrodeoxygenation, these oxygenated precursors are transformed into isomeric alkanes with freezing points below −100 °C, meeting and even surpassing aviation fuel standards. Importantly, the mild conditions, high selectivity, and compatibility with a wide range of ketone feedstocks indicate the route’s strong industrial application potential for large-scale production of ultralow freezing biojet fuel for extreme aviation environments.