Kinetics of the gas-phase oxidation of methanol catalysed by nitric oxide

Abstract

The oxidation of methanol catalysed by nitric oxide has been studied in a static system in the temperature range 300-400°. The kinetics and product distribution were compared with previously published data on the uncatalysed reaction and shoum to dlffer significantly. The reaction vessel was of Pyrex glass and the maximum rate was found to be sensitive to the condition of its surface. The rate of pressure change was shown to be a valid measure of the reaction rate which accelerated rapidly to a maximum, remained constant for some time, and then decreased slowly.

The overall activation energy was about 8 kcal mole^-1 in the range 300-330°, and 25 kcal mole^-1 between 360 and 400°. At 310°

(d(Δp)/dt)max. ∝ [CH₃OH]₀^0.4[O₂]₀^-1 [NO]₀^1.7

and at 380°

(d(Δp)/dt)max. ∝ [CH₃OH]₀^0.75[O₂]₀^-1 [NO]₀^0.75

provided that [O₂]₀ < [CH₃OH]₀ = 100 mmHg. At [O₂]₀ > [CH₃OH]₀, the maxi- mum rates were approximately independent of [O₂]₀ The pressure of the product, formaldehyde, always rose to a maximum and then decayed in the later stages of an experiment. Oxides of nitrogen appear to participate in the chain reaction.