On the Dependence of the Rate of Moist CO Oxidation on O2Concentration at Atmospheric Pressure.

Counter·intuitively, moist CO oxidation is experimentally shown to be inhibited by the addition of oxygen to stoichiometric mixtures at 1000 K and atmospheric pressure. At these conditions, oxygen essentially reduces the ratio of [H]/[OH] such that the consumption of HO2 occurs through chain-terminating rather than chain propagating reactions, Although multiple sets of reactions are active in this transition, the principal effect results from a transition from HO2 + H - OH + OH to HO2 + OH - H2O+O2 and H02+0-0H+02 as oxygen concentration is increased, As temperature is increased these reactions have a lesser influence on the 0, Hand OH radical pool due to the reduced production of HO2, Near 1040 K, the inhibition effects cease to be observed and the reaction rate is essentially independent of oxygen concentration. At higher temperatures still, previous experiments have shown that oxygen addition increases the rate of CO consumption. These experimental trends are qualitatively predicted by a comprehensive mechanism for CO/H2/02 oxidation developed previously. Quantitative predictions can be obtained by updating the rate of H02 + OH - H20 + 02 to the values given by recently published reviews of low temperature data and to new high temperature experimental data.