Determination of the Arrhenius Parameters for the Initiation Reaction C3H6 + O2 -> CH2CHCH2 + HO2

DOI: 10.1039/ft9918700241

Source and publish data:

Journal of the Chemical Society - Faraday Transactions p. 241 - 247 (1991)

Update date:2022-08-11

Topics:

Authors:

Stothard, Nigel D.

Walker, Raymond W.

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Article abstract of DOI:10.1039/ft9918700241

Results obtained from studies of the oxidation of propene between 400 and 520 deg 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 deg 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 <(R_HDE)_O>, so that secondary initiation is negligible, then in the absence of radical branching the simple relationship k₇ = (R_HDE)_O 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 = 10^9.2 dm³ mol^-1 s^-1 and E₇ = 162 kJ mol^-1.CH3CH=CH2 + O2 -> CH2CHCH2 + HO2 (7) 2CH2CHCH2 -> CH2=CHCH2CH2CH=CH2 (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 interpretaion and of the simple relationship above.Final values of A₇ = 10^{9.29 +/- 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 = 10^{8.21 +/- 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)