A new method for determination of reactivity ratios in hydrocarbon oxidation processes

A new method has been devised to determine reactivity ratios in hydrocarbon oxidation processes. Reactivity ratio is defined as the ratio of rate constants of the elementary chain propagation processes between the initial hydrocarbon and chain carrier radicals to similar reactions of the hydrocarbon intermediates. The determination is carried out by introducing the intermediate in question in labeled form and subsequently measuring its concentration and radioactivity during the oxidation. It is established that the appropriate equations can be accurately applied to liquid-phase oxidations. In gas-phase oxidations, however, certain difficulties arise when using this procedure. For the application in the latter case the necessary conditions are fulfilled only when chain carrier radicals stemming from the radical isomerization processes possess similar reactivity or when one contributes significantly to the chain propagation. Calculations have been made for six oxidation processes and the corresponding reactivity ratios are reported.