Synthesis of Renewable High-Density Fuel with Cyclopentanone Derived from Hemicellulose

1-(3-Cyclopentyl)cyclopentyl-2-cyclopentylcyclopentane, a renewable high-density fuel, was first produced in a high overall carbon yield (∼70%) with cyclopenanone that can be derived from hemicellulose. The synthetic route used in this work contains three steps. In the first step, 2-cyclopentyl cyclopentanone was synthesized for the first time by a one-pot reaction of cyclopentanone and hydrogen under the catalysis of Raney metal and alkali hydroxides. Over the optimized catalyst (Raney cobalt + KOH), a high carbon yield (83.3%) of 2-cyclopentyl cyclopentanone was achieved at 353 K. In the second step, 2-cyclopentyl-5-(2-cyclopentylcyclopentylidene)cyclopentanone was produced in a high carbon yield (95.4%) by the solvent-free self-aldol condensation of 2-cyclopentyl cyclopentanone under the vacuum conditions. In the third step, the 2-cyclopentyl-5-(2-cyclopentylcyclopentylidene)cyclopentanone was hydrodeoxygenated over the Ni-SiO2 catalyst under solvent-free conditions. High carbon yields of 1-(3-cyclopentyl)cyclopentyl-2-cyclopentylcyclopentane (88.5%) and polycycloalkanes (99.0%) were obtained. The Ni-SiO2 catalyst was stable under investigated conditions. No evident deactivation was noticed during the 50 h time on stream. The as-obtained polycycloalkane mixture has a density of 0.943 g mL–1 and a freezing point of 233.7 K. As a potential application, it can be blended into conventional high density fuels (e.g., JP-10) for rockets and missile propulsion.