Kinetics of Decomposition of Nitric Oxide at Elevated Temperatures. II. The Effect of Reaction Products and the Mechanism of Decomposition

Abstract

The effects of nitrogen and oxygen on the kinetics of decomposition of nitric oxide have been investigated. In the temperature region in which the heterogeneous mechanism prevails (at T<1000°K) the presence of nitrogen has a marked retarding influence on the reaction rate of nitric oxide due to poisoning of the surface. On the other hand, the addition of oxygen results in a marked increase in the rate of decomposition of nitric oxide over the entire temperature range studied. At high concentrations of oxygen the following empirical rate expression obtains, $$-\frac{\mathrm{d[}\mathrm{NO}]}{\mathrm{dt}}{\mathrm{=k}}_a[\mathrm{NO}{]}^2{\mathrm{+k}}_b[\mathrm{NO}\mathrm{][}{\mathrm{O}}_2{]}^{\frac{1}{2}},$$ with an activation energy of 78.2 kcal for the rate‐determining step. It is apparent therefore that the decomposition of nitric oxide is autocatalytic. On the basis of these experimental observations a mechanism is proposed involving a chain propagated by the atomic species formed in the reaction.