Production of Low-Freezing-Point Highly Branched Alkanes through Michael Addition

A new approach for the production of low-freezing-point, high-quality fuels from lignocellulose-derived molecules was developed with Michael addition as the key step. Among the investigated catalysts, CoCl₂ ⋅6 H₂ O was found most active for the Michael addition of 2,4-pentanedione with FA (single aldol adduct of furfural and acetone, 4-(2-furanyl)-3-butene-2-one). Over CoCl₂ ⋅6 H₂ O, a high carbon yield of C₁₃ oxygenates (about 75 %) can be achieved under mild conditions (353 K, 20 h). After hydrodeoxygenation, low-freezing-point (<223 K) branched alkanes with 13 carbons within jet fuel ranges were obtained over a Pd/NbOPO₄ catalyst. Furthermore, C_18,23 fuel precursors could be easily synthesized through Michael addition of 2,4-pentanedione with DFA (double-condensation product of furfural and acetone) under mild conditions and the molar ratio of C₁₈ /C₂₃ is dependent on the reaction conditions of Michael addition. After hydrodeoxygenation, high density (0.8415 g mL^-1 ) and low-freezing-point (<223 K) branched alkanes with 18, 23 carbons within lubricant range were also obtained over a Pd/NbOPO₄ catalyst. These highly branched alkanes can be directly used as transportation fuels or additives. This work opens a new strategy for the synthesis of highly branched alkanes with low freezing point from renewable biomass.