Shock reaction of hexane at 77, 193, and 273 K with special reference to shock pressure

Abstract

Shock waves generated by projectile impacts were transmitted into hexane and the shocked hexane was analyzed by TCD-GC, FID-GC, GCMS, and FABMS for produced aliphatic hydrocarbons. The projectile length and its velocity were varied from 10 to 40 mm and from 220 to 1040 m/s, respectively. The initial temperature of the hexane was 77, 193 and 273 K. The major products detected throughout the reactions were hydrogen, light alkanes from C\(_1\) to C\(_4\), and light alkenes from C\(_2\) to C\(_3\). The minor products were heavy alkanes from C\(_8\) to C\(_{12}\) and soot-like materials. Experiments with varied projectile length revealed that the shock reaction occurred only while the shock wave was transmitted through hexane (about \(10^{-6}\) seconds). This short reaction time may be responsible for a lower yield of branched products in the shock reaction compared with yield produced by hexane pyrolysis in previous studies. In the shock reaction of hexane, the dehydrogenation was one of the important reactions and the recombination of hexyl radicals might play a role in the formation of \(n\)-C\(_{12}\). Experiments with varied initial temperature suggested that the molar yield of products depends not on the shock temperature but on the shock pressure, and that the reaction mechanisms for solid hexane and for liquid hexane are not identical. As the shock pressure increased, the relative yield of heavy products increased while that of light products decreased. This could be interpreted mainly by considering the activation volumes of the reaction involved.