Thermal Isomerization and Decomposition of 2-Butyne in Shock Waves

Article abstract of DOI:10.1021/j100144a014

The thermal isomerization and decomposition of 2-C4H6 behind reflected shock waves with 1100 < T₅ < 1600 K and 1.6 x 1E-5 < ρ < 2.1 x 1E-5 mol/cm³ were studied by UV kinetic absorption spectroscopy, IR laser kinetic absorption spectroscopy, and gas-chromatographic analysis of reaction products.The major products of the pyrolysis were 1,2-butadiene, 1,3-butadiene, CH4, C2H2, C2H6, allene, propyne, C4H2, vinylacetylene, and benzene. 1,3-butadiene and 1,2-butadiene were produced before the appearance of any other decomposition products.This fact means that the very fast isomerization of 2-butyne take place before the decomposition.The present data were successfully modeled with a 80 reaction mechanism which included the isomerizations among 1- and 2-butynes and 1,2- and 1,3-butadienes and the decomposition of these C4H6 isomers.From the modeling, the following rate constants of the isomerizations were obtained: 2-butyne = 1,3-butadiene (k = (3.0 x 1E13) exp(-65.0 kcal/RT) s^-1). and 2-butyne = 1,2-butadiene (k = (3.0 x 1E13) exp(-67.0 kcal/RT) s^-1), where the activation energies, 65 and 67 kcal/mol, were estimated from literature data.We discussed the possible route of the isomerizations of 2-butyne to 1,3- and 1,2-butadienes.