Thermal cracking of jet propellant-10 with the addition of a core-shell macroinitiator

Abstract To accelerate the thermal cracking of hydrocarbon fuels and improve the cooling capacity for aircraft heat exchangers, cetyl-hyperbranched polyethyleneimine (CHPEI) synthesized from the modification of hyperbranched polyethyleneimine (HPEI) with a lipophilic alkyl chain was used as a novel macroinitiator. The pyrolysis performances under supercritical conditions (4.0 MPa, and 600–700 °C) of Jet propellant-10 (JP-10 or exo -tricyclo[5.2.1.0 2.6 ]decane) with CHPEI and the monomer triethylamine were compared in an electrically heated alloy tube. Both types of initiators with C-N bonds can promote the thermal cracking of JP-10, while CHPEI with a large molecular weight shows a similar crack-promoting effect to that of triethylamine with adding only one-tenth of the amount of the latter. As a typical example, the addition of 0.20 wt% CHPEI increased the conversion rate of JP-10 from 16.4% to 33.9%, and the corresponding heat sink was improved from 1.96 MJ/kg to 2.18 MJ/kg at 675 °C. On the basis of investigations on the intermediate species from different decomposition pathways of JP-10, it is proved that CHPEI accelerates the thermal cracking of JP-10 by generating lots of free radicals to participate in the H-abstraction reaction of JP-10. These efforts demonstrate that the macroinitiator CHPEI displays a great promise in hydrocarbon fuels for hypersonic applications.