Kinetics of Oxidation of Pyridine in a Flow System

Abstract

The rate of oxidation of pyridine and the nitrogen containing products formed during the oxidation were studied in the temperature range of 675–775° C using a Vycor, stirred-flow reactor. The rate was found to be half-order in pyridine, first-order in oxygen and half-order in oxygen consumed for both rich and lean mixtures. The activation energy and log frequency factor were 54·0 kcal/mole and 14·9 (using M^-1 sec^-1), respectively. Coating the reactor wails with KG had no significant effect on reaction order or activation energy, although the rate was increased by about a factor of two. An alternative to the apparent autocatalysis factor, ( δO₂)1/2, could be that the rate of radical escape was competitive with that of chemical termination. The treatment using this assumption was applied to the data, however, the scatter prevented drawing a definite conclusion concerning these two alternatives. Product determinations indicated that nitrogen was accounted for by the HCN and N₂ formed for lean mixtures when oxygen concentration was 7·0 mole percent or below; significant nitrogen appeared in the smoke for rich mixtures. However, at higher oxygen concentrations, N₂O and NO became more significant as products. The mechanistic implications of these observations are discussed.