Synthesis of Decaline-Type Thermal-Stable Jet Fuel Additives with Cycloketones

Decalin is a jet fuel additive with high thermal stability and energy density. Herein, we reported a novel method for the preparation of decalin from cyclopentanone, a hemicellulose derived cycloketone. Ethanolamine acetate (EAOAc), an ionic liquid catalyst which can be derived from biomass, was first applied to the self-aldol condensation of cyclopentanone and demonstrated good activity for this reaction. After the optimization of reaction conditions, ∼83.5% carbon yield of 2-cyclopentylidenecyclopentanone was achieved over the EAOAc catalyst. The hydrodeoxygenation of 2-cyclopentylidenecyclopentanone over a physical mixture of Ru/C and H-β zeolite afforded bi(cyclopentane) which could be further isomerized to decalin. Among the screened catalysts, La-Y zeolite exhibited excellent performance for the isomerization process. According to the characterization results, the high activity of La-Y was rationalized by its large medium-strong acid amount and the appropriate ratio of Brønsted acid to Lewis acid. Analogously, branched decalins were synthesized with cyclohexanone using the same procedure.