Synthesis and comprehensive fuel properties of mono-substituted alkyl adamantanes for advanced aerospace propulsion

Abstract Design and choice of fuels continue to be improved for aviation propulsion, and alkyl adamantanes have attracted great attention due to their high density, good low-temperature properties and potential characteristics. Herein, we reported a facile route to synthesize mono-substituted alkyl adamantanes via modified Grignard coupling (followed with one-step hydrodeoxygenation), including 1-ethyl-adamantane, 2-ethyl-adamantane, and 1-n-propyl-adamantane with high yields (> 75%). The process was modified via concentrating the Grignard reagents and altering the solvent, and one-step hydrodeoxygenation catalyzed by commercial Pd/C and zeolites was developed. Subsequently, comprehensive characteristics of alkyl diamondoid series, such as oxidation stability and combustion properties, were evaluated using pressure differential scanning calorimetry, rapid small-scale oxidation test, and hot-plate ignition test. Also, the specific impulse of alkyl diamondoids were revealed by theoretical calculation. The high-density alkyl diamondoids present adequate oxidation stability and possess better combustion characteristics over JP-10, thus can be considered as potential high-energy-density fuel for aerospace propulsion.