Mass-spectrometric investigation of reaction of oxygen atoms with methane

Abstract

A mass-spectrometric stirred-reactor technique was used to study the reaction of atomic oxygen with methane with low concentrations of molecular oxygen. An overall rate constant for oxygen-atom disappearance due to added methane was obtained for the temperature range 375 to 576°K. This rate constant was 4 × 1014 exp (− 10 000/RT) cm3 mole−1 s−1 and was compared with a previous rate constant for this reaction that had been measured in the presence of a large excess of molecular oxygen. This comparison showed that the presence of an excess of molecular oxygen produced a considerable increase in oxygen-atom consumption at low temperatures, but only a small increase at high temperatures. From product analyses, the stoichiometry of the reaction could be approximately represented by [Formula: see text]From the reaction stoichiometry and the rate constant for the oxygen-atom disappearance, the rate constant for methane disappearance was calculated to be 1 × 1014 exp (− 10 000/RT) cm3 mole−1 s−1. The presence of excess molecular oxygen has very little effect on this rate constant, contrary to the result found for the disappearance of atomic oxygen.