Reaction of hydrogen atoms with propane in the temperature range 298–534 K
Abstract
The reaction of hydrogen atoms with propane has been investigated at a helium pressure of ca. 5 Torr in the temperature range 298–534 K using a conventional flow-discharge system coupled to a quadrupole mass spectrometer. Two sets of pseudo-first-order experiments were performed: (i) where [C3H8][H], in which case decay of [H] was measured, and (ii) where [C3H8]
[H], in which case formation of CH4 was measured.
In order to evaluate the rate constant, k1, of the reaction assumptions concerning the stoichiometry of the overall process have to be made. It is shown that previous assumptions are wrong. We have used computer integration of a detailed mechanism for the overall process to evaluate self-consistent values of k1 from our experimental data. We obtain the Arrhenius parameters log (k1/cm3 mol–1 s–1)=(13.81 ± 0.07)–(28.8±0.6) kJ mol–1/2.3 RT from our results for T 370 K. At lower temperatures there is evidence for curvature of the Arrhenius plot and the activation energy drops to 21.8±1.8 kJ mol–1 for temperatures < 370 K.