Determination of the arrhenius parameters for the initiation reaction C3H6+ O2? CH2CHCH2+ HO2

Abstract

Results obtained from studies of the oxidation of propene between 400 and 520 °C have been used to obtain the first Arrhenius parameters for the important chain initiation reaction RH + O2→ R + HO2, where RH is a hydrocarbon.A full product analysis in the early stages of reaction has been made for a number of mixtures at 400, 440, 480 and 520 °C. It has been shown that hexa-1,5-diene is a major initial product and that its formation in reaction (8) represents the major termination process. By use of measurements of the initial rate of formation of hexa-1,5-diene [(RH D E)0], so that secondary initiation is negligible, then in the absence of radical branching the simple relationship k7[C3H6][O2]=(RH D E)0 holds. Values of k7 at a constant temperature obtained from the relationship vary by less than a factor of two over a wide range of mixture composition, and the average values at each temperature give A7= 109.2 dm3 mol–1 s–1 and E7= 162 kJ mol–1. CH3CHCH2+ O2→ [graphic omitted] + HO2(7), [graphic omitted] → CH2CHCH2CH2CHCH2(8)When allowance is made for minor termination processes and for the radical-branching reaction (17), the values of A7 and E7 change only slightly, confirming the essential validity of the interpretation and of the simple relationship above. Final values of A7= 109.29 ± 0.41 dm3 mol–1 s–1 and E7= 163.5 ± 6 kJ mol–1 are obtained for reaction (7). The interpretation also gives reliable Arrhenius parameters of A17= 108.21 ± 0.60 dm3 mol–1 s–1 and E17= 72.5 ± 8.3 kJ mol–1 for the radical-branching reaction (17). No previous estimates are available for either reaction. CH2CHCH2+ O2→ 2 radicals + products (17)