ARRHENIUS PARAMETERS FOR THE ADDITION OF HO2 RADICALS TO ETHENE BETWEEN 400-DEGREES-C AND 500-DEGREES-C

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-degrees-C. [GRAPHICS] From measurements of the initial values of the product ratio [C2H4O]/[isobutene] over a range of mixture composition at 400, 440, 470 and 500-degrees-C, values of A2/A7(1/2) = 10(5.23) (dm3 mol-1 s-1)1/2 and E2 - 1/2E7 = 75.4 +/- 5.0 kJ mol-1 are obtained. [GRAPHICS] 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/A7(1/2) = 10(4.94 +/- 0.25) (dm3 mol-1 s-1)1/2 and E2 - 1/2E7 = 71.5 +/- 3.5 kJ mol-1 are recommended between 380 and 500-degrees-C. Use of the recommended values of A7 = 1.87 x 10(9) 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.