No abstract

Endothermic hydrocarbon fuels (EHFs) are meant to regeneratively cool high-speed flight components and surfaces. In addition to physical heat absorption, they also undergo thermal decomposition thus offering a chemical heat sink. In this study, two single-molecule hydrocarbons, i.e., JP-10 (exotetrahydrodicyclopentadiene) and 3-carene (3,7,7-trimethylbicyclo[4.1.0]­hept-3-ene), are tested for their applicability as EHF. Noncatalytic and catalytic pyrolysis tests were carried out in an analytical Curie point pyrolyzer coupled with gas chromatograph/mass spectrometer using zeolites (HY, Hβ, and Mordenite) at 500 and 650 °C. A quantitative analysis of the pyrolysate composition is performed to evaluate the effects of temperature, catalyst type and catalyst loading. The results demonstrated that the effect of temperature was minimal since the pyrolytic reactions were driven primarily by the protolysis of the reactants. The yields of low molecular weight (LMW) hydrocarbons were higher with HY and Hβ, whereas the extent of cracking was low over Mordenite. The highest LMW alkene and alkane yields of 11.9 and 5.8 wt %, respectively, were achieved with HY in the case of JP-10. Similarly, for 3-carene, LMW alkene and alkane yields were 15.2 and 11.4 wt %, respectively, in the presence of HY. Propylene, isobutylene and isopentane were the dominant pyrolysates from both the fuels with catalysts. Cycloalkanes and cycloalkenes were the major alicyclic hydrocarbons formed from JP-10 and 3-carene, respectively. The yields of alkanes, alkenes, cycloalkanes and benzene derivatives increased with catalyst loading for JP-10. In the case of 3-carene, a similar trend was followed except for cycloalkenes whose yield decreased with catalyst loading. Plausible reaction pathways for the formation of LMW hydrocarbons from both the fuels are proposed.