Pyrolysis mechanism of carbon matrix precursor cyclohexane(III) - pyrolysis process of intermediate 1-hexene

The pyrolysis mechanism of important intermediate 1-hexene of carbon matrix precursor cyclohexane was studied theoretically. Possible reaction paths were designed based on the potential surface scan and electron structure of the initial C-C bond breaking reactions. Thermodynamic and kinetic parameters of the possible reaction paths were computed by UB3LYP/6-31+G* at different temperature ranges. The results show that 1-hexene pyrolyzes at 873 K. When below 1273 K, the major reaction paths are those that produce C3H4, and above 1273 K, the major reaction paths are those that produce .C3H3 from the viewpoint of thermodynamics. From the viewpoint of kinetics, the major product is .C3H3, it results from the pyrolysis reaction of I-hexene cracking bond C-3-C-4 and generating .C3H5 and .C3H7 with the activation energy DeltaE(0)(not equaltheta)=296.32 kJ/mol. Kinetic results also show that product C3H4 accompany simultaneously, which is the side reaction starting from the pyrolysis of I-hexene forming .C4H7 and .C2H5 with the activation energy of 356.73 kJ/mol. When reaching 1473 K, the rate constant of the rate-determining steps of these two reaction paths do not show much difference, which means both the reaction paths exist in the pyrolysis process at the high temperature. The above results are basically in accordance with mass spectrum analysis and far more specific. (C) 2004 Elsevier B.V. All rights reserved.