OXIDATION OF N-BUTANE - TRANSITION IN THE MECHANISM ACROSS THE REGIONOF NEGATIVE TEMPERATURE-COEFFICIENT

An experimental investigation has been conducted of the transition in the oxidation chemistry of n-butane across the region of negative temp erature coefficient from low to intermediate temperatures. The experim ental results indicated a region of negative temperature coefficient b etween approximately 640 and 695 K and a shift in the nature of the re action intermediates and products across this region. On the basis of these experimental results and some recent kinetic modeling results fo r the reaction R + O-2 reversible arrow RO(2), a new mechanism is pres ented for n-butane to describe the observed phenomena. At low temperat ures the major reaction path of butylperoxy is isomerization followed by O-2 addition, further isomerization, and decomposition to mainly ca rbonyls and OH radicals. At intermediate temperatures, the major react ion of butylperoxy is isomerization followed by decomposition to buten es and HO2 and to epoxides and OH. The mechanism is consistent with th ese and other experimental results and predicts the negative temperatu re coefficient and the shift in product distribution with temperature.