pyrolysis of n-butane, initiated by methyl radicals has been studied in the temperature range 750–1000 K and at pressures 0.08–0.13 bar in a quasi-wall-free reactor using laser heating by fast vibrational–translational
(V–T) energy transfer. This is a convenient method to study homogeneous high-temperature kinetics since the
reactor walls remain cold. The radial temperature distribution in the reactor has been investigated by four different methods: stationary heat balance, optical absorption, pressure rise, and the temperature dependence
of the rate of an isomerization reaction. Methyl radicals were produced ia the fast thermal dissociation
of di-tert-butyl peroxide and product analysis was performed by the use of GC-MS. The main products
of the overall reaction of the model system (n-C4H10
+ CH3) were C2H4, C3H6, C3H8, whereas 1-C4H8, n-C5H12,
iso-C5H12 were minor components, all showing a strong dependence on temperature. The product distribution
and the temperature dependence were analyzed by a kinetic model of 61 species and 164 reactions developed
for the high-temperature butane and the low-temperature n-pentane oxidation. Good agreement was found between our experimental investigations and the modeling. However, we had to slightly adjust the rate constants for the reactions
a temperature of 1000 K we found a larger branching ratio of k3/(k3
k4) = 1/3 compared to 1/8 as
extrapolated from low-temperature data. The total rate coefficient was found to be (k3
k4) = 8 × 109 cm3
mol−1 s−1 which is about 50% higher than the extrapolated values.
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