Arrhenius parameters for the reaction HO2+ C2H6→ C2H5+ H2O2 over the temperature range 400–500 °C

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Abstract
Studies have been made of the addition of C2H6 to mixtures of tetramethylbutane (TMB)+ O2 over the temperature range 400–520 °C in both boric acid-coated and KCl-coated Pyrex vessels. From measurements of the relative yields of i-C4H8 and C2H4, formed from TMB and C2H6, respectively, values of k10/k½ 7 have been determined: HO2+ C2H6→ H2O2+ C2H5(10), HO2+ HO2→ H2O2+ O2. (7) By use of low total pressures (ca. 15 Torr), the contribution of OH attack to the overall formation of C2H4 has been reduced to a very low level. At temperatures above 470 °C, the values of k10/k½ 7 in KCl-coated vessels were noticeably above those obtained from the boric acid-coated vessels, and this has been attributed to possible gas-phase regeneration of radicals when H2O2 is removed at the KCl surface. Values of E10–½E7= 82.7 ± 1.5 kJ mol–1 and A10/A½ 7= 105.49 ± 0.11(dm3 mol–1 s–1)½ were obtained. Low-temperature values of k7 have been partially re-interpreted and combined with Tröe's single temperature value at 1100 K to obtain values of k7 for use under the conditions of the present study. In this way, Arrhenius parameters of E10= 85.6 ± 2.5 kJ mol–1 and A10= 1010.23 ± 0.16 dm3 mol–1 s–1 were obtained. No other data are available for this reaction, but the parameters are in good agreement with A= 1010.38 dm3 mol–1 s–1 and E= 84.5 ± 8 kJ mol–1 for the reaction of HO2 radicals with TMB, both alkanes containing only primary C—H bonds.

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