Experimental and modeling study of hex-5-en-1-yl radical pyrolysis at very high pressure and temperature

Abstract

The pyrolysis of the hex-5-en-1-yl radical was studied with the use of 6-bromo-1-hexene as the precursor. Shock tube experiments were completed at high pressures (40, 100, and 200 bar) and temperatures (900 to 1450 K) with dilute mixtures of 6-bromo-1-hexene (approximately 160 ppm) to determine whether a variation of the experimental pressure has an effect on the product distribution, and whether high experimental pressures may lead to the formation of alkylcyclopentanes. Another set of experiments was completed using a higher concentration fuel mixture of 6-bromo-1-hexene (358 ppm) to determine whether the product distribution changes were caused by varying the experimental pressure, or the initial fuel concentration in the reaction zone. It was found that at the current experimental conditions the product distribution is sensitive to the initial fuel concentration. Among the major products observed in the current work were ethylene, propadiene, propyne, methane, acetylene, propene, diacetylene, vinylacetylene, 1,5-hexadiene, benzene, and cyclohexene. An additional set of experiments was also completed using 1,5-hexadiene as the fuel to determine whether 6-bromo-1-hexene pyrolysis might be dominated by HBr loss which would result in the formation of 1,5-hexadiene as the dominant initial product, but it was found not to be the case. A mechanism was generated using the Reaction Mechanism Generator with the JetSurF 2 mechanism as the seed mechanism in an attempt to model the current experimental data, but it was found to not be able to capture the benzene formation in the 6-bromo-1-hexene experiments. A reasonable prediction of the 6-bromo-1-hexene pyrolysis data was obtained with the mechanism if the fuel mixture used for simulations was composed of 50% 1,5-hexadiene and 50% hex-5-en-1-yl radical. Using purely hex-5-en-1-yl radical as the fuel for the simulations resulted in poor prediction of the experimental data for almost all the species, except for methane.