Oxidation of n-Butane: Transition in the Mechanism across the Region of Negative Temperature Coefficient

Abstract

An experimental investigation has been conducted of the transition in the oxidation chemistry of n-butane across the region of negative temperature coefficient from low to intermediate temperatures. The experimental results indicated a region of negative temperature coefficient between approximately 640 and 695 K and a shift in the nature of the reaction intermediates and products across this region. On the basis of these experimental results and some recent kinetic modeling results for the reaction R + O{sub 2} {r_equilibrium} RO{sub 2}, a new mechanism is presented for n-butane to describe the observed phenomena. At low temperatures the major reaction path of butylperoxy is isomerization followed by O{sub 2} addition, further isomerization, and decomposition to mainly carbonyl and OH radicals. At intermediate temperatures, the major reaction of butylperoxy is isomerization followed by decomposition to butenes and HO{sub 2} and to epoxides and OH. The mechanism is consistent with these and other experimental results and predicts the negative temperature coefficient and the shift in product distribution with temperature.