Multicyclic hydrocarbons are intriguing molecules that have applications as high performance fuels. The dense structures of these molecules allow for volumetric net heats of combustion (NHOCs) significantly higher than conventional jet or diesel fuels. Recent work by our group has shown that renewable fuels prepared by blending multicyclic sesquiterpanes with ethanol-derived synthetic paraffins have cetane numbers &gt;45 and densities of up to 0.85 g/mL. The multicyclic sesquiterpanes increase the density and NHOC of the mixture, while the paraffins decrease the low temperature viscosity and increase the cetane number of the blends. Building on this research, a series of alkyl diamondoids have now been synthesized that combine a dense multicyclic core with a straight chain alkyl group in the same molecule. These molecules have NHOCs up to 15% higher than conventional jet fuel and derived cetane numbers from 42 to 50. These are the first examples of multicyclic fuels with densities and NHOCs comparable to the synthetic missile fuel JP-10 and cetane numbers high enough for combustion in conventional diesel engines. In addition to the derivation of these molecules from petrochemical feedstocks, the bio-derived multicyclic sesquiterpane cedrane has been isomerized with aluminum chloride to generate a mixture of alkyl adamantanes with 1-ethyl-3,5,7-trimethyladamantane as the major product. This fuel mixture has a cetane number of 46 and a -20 °C viscosity ca. three times lower than previously studied tricyclic sesquiterpanes. Regardless of the source, the alkyl diamondoid fuels presented here have potential applications as dynamic high performance fuels that can extend the range of both turbine and diesel powered vehicles.

Synthesis and characterization of high density multicyclic fuels based on sesquiterpanes and alkyl diamondoids

253rd National Meeting (2017)

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