Thermal Isomerization and Decomposition of 1,2-Butadiene in Shock Waves

Article abstract of DOI:10.1002/kin.550270404

1,2-Butadiene diluted with Ar was heated behind reflected shock waves over the temperature and the total density ranges of 1100 - 1600 K and 1.36*10^-5 - 1.75*10^-5 mol/cm³.The major products were 1,3-butadiene, 1-butyne, 2-butyne, vinylacetylene, diacetylene, allene, propyne, C2H6, C2H4, C2H2, CH4, and benzene, which were analyzed by gas-chromatography.The UV kinetic absorption spectroscopy at 230 nm showed that 1,2-butadiene rapidly isomerizes to 1,3-butadiene from the initial stage of the reaction above 1200 K.In order to interpret the formation of 1,3-butadiene, 1-butyne, and 2-butyne, it was necessary to include the parallel isomerizations of 1,2-butadiene to these isomers.The present data were successfully modeled with a 82 reaction mechanism.From the modeling, rate constant expressions were derived for the isomerization 1,2-butadiene = 1,3-butadiene to be k₃ = 2.5*10¹³ exp(-63 kcal/RT) s^-1 and for the decomposition 1,2-butadiene = C3H3 + CH3 to be k₆ = 2.0*10¹⁵ exp(-75 kcal/RT) s^-1, where the activation energies, 63 kcal/mol and 75 kcal/mol, were assumed.These rate constants are only applicable under the present experimental conditions, 1100 - 1600 K and 1.23 - 2.30 atm.