Arrhenius parameters for the addition of HO2 radicals to ethene between 400 and 500 °C

Abstract

The decomposition of tetramethylbutane in the presence of O₂ has been used to provide a source of HO₂ radicals in order to obtain Arrhenius parameters for reaction (2) over the range 400–500 °C. HO₂+ C₂H₄→ C₂H₄O + OH (2) From measurements of the initial values of the product ratio [C₂H₄O]/[isobutene] over a range of mixture composition at 400, 440, 470 and 500 °C, values of A₂/A^1/2₇= 10^5.23(dm³ mol^–1 s^–1)^1/2 and E₂–½E₇= 75.4 ± 5.0 kJ mol^–1 are obtained. HO₂+ HO₂→ H₂O₂+ O₂(7) These results are in good agreement with previous values obtained in aged boric-acid-coated vessels and KCl-coated vessels, and optimum parameters of A₂/A^1/2₇= 10^{4.94 ± 0.25}(dm³ mol^–1 s^–1)^1/2 and E₂–½E₇= 71.5 ± 3.5 kJ mol^–1 are recommended between 380 and 500 °C. Use of the recommended values of A₇= 1.87 × 10⁹ and E₇= 6.4 gives A₂= 10^{9.58 ± 0.35} dm³ mol^–1 s^–1 and E₂= 74.7 ± 4.5 kJ mol^–1.