Alkyl-adamantane as high-density endothermic fuel: Synthesis and thermal cracking performance

Abstract

High-density endothermic fuels have drawn much attention for aerospace vehicles due to their advantage in high density and heat sink. Herein, a new high-density endothermic fuel, hexyl-substituted 1,3-dimethyl adamantane (HS-1,3-DMA), was synthesized by alkylation of 1,3-DMA with hexene catalyzed by AlCl3. The alkylation reaction conditions (catalyst and its amount, 1,3-DMA/hexene ratio and reaction temperature) were optimized, and the 1,3-DMA conversion of 46.0% with HS-1,3-DMA selectivity of 67.9% can be obtained. Importantly, HS-1,3-DMA shows high density of 0.89 g·cm−3, high combustion energy of 42.4 MJ·kg−1 and high heat sink of 1.93 MJ·kg−1 at 575 °C (4 MPa), which is 11.6% and 9.7% higher than those of JP-10 and 1,3-DMA. Moreover, the thermal cracking of HS-1,3-DMA leads to lower coke deposition, whose amount is ca. 50.0% of JP-10 and 1,3-DMA. Notably, HS-1,3-DMA has a higher density and heat sink at low temperatures than that of EHF-80, respectively, while at high temperatures, heat sink of HS-1,3-DMA is also similar to that of EHF-80. This work provides a promising route to produce high-density endothermic fuel for practical application.