Synthesis and Performance of Cyclopentadiene-Based Spirocyclopropane High-Energy-Density Fuels

High-energy-density fuels play a vital role in the development of the aviation industry because they can provide more propulsion energy than conventional liquid fuels. Constructing more five- or six-membered rings in fuel molecules is an efficient way to increase fuel density. However, as the number of rings increases, the hydrogen content of fuel molecules gradually decreases, resulting in a decrease in the mass calorific value, which limits the further improvement of the volumetric calorific value, meanwhile, the low-temperature characteristics of the fuel become worsen. Considering the high strain energy stored in cyclopropane moiety and the good cryogenic properties of spiro fuel, in this work, two spirocyclopropane high-energy-density fuels have been synthesized from cyclopentadiene by phase transfer catalytic cyclopropanation and palladium catalytic cyclopropanation, and the reaction conditions have been optimized. The synthesized fuels possess heat value and specific impulse higher than the widely used high-energy-density fuel JP-10. Additionally, their kinematic viscosity at low temperatures is only about one-third that of JP-10. The outstanding properties of the synthesized strained fuels suggest their good potential as high-energy-density fuels.