Synthesis and fuel properties of high-energy density cyclopropanated monoterpenes

Seven different high-performance fuels were synthesized from bio-based monoterpenes (3-carene, sabinene, α-pinene, β-pinene, limonene, 1,6-dimethyl-1,5-cyclooctadiene, and myrcene) by Simmons-Smith cyclopropanation. Key fuel properties of the resulting multicyclic fuel mixtures were measured including, density, net heat of combustion (NHOC), and low-temperature viscosity. The mixtures exhibited densities 10–16% higher and volumetric NHOCs 12–16% higher than conventional jet fuel, while maintaining low temperature (−20 °C) viscosities either below or close to the specification limit. To evaluate the fuels as potential rocket propellants, heats of formation were calculated using the G4 composite method. These values were then used to calculate specific impulse (Isp) and density-specific impulse (d-Isp) for each fuel mixture. The cyclopropanated monoterpenes exhibited sea level Isp values up to 1.2% higher than conventional rocket propellant (RP-1) and d-Isp values up to 4.1% higher than RP-1. The results of this study suggest that cyclopropanated monoterpenes may have utility as high-performance jet fuel blendstocks or specialized rocket propellants, offering the ability to increase the payload capacity and enhance the mission capability of space-delivery systems. This work further highlights the potential of biosynthetic fuels for high-performance applications.