Ignition kinetics of the carbon monoxide-oxygen reaction

Abstract

An analytic solution for the ignition kinetics of the dry CO−O2 reaction is obtained by assuming an initiation reaction followed by the chain-branching steps C O + O → C O 2 * C O 2 * + O 2 → C O 2 + 2 O together with chain termination by quenching of CO2* and three-body recombination of CO and O. It is concluded that shock-tube induction times on reportedly dry CO−O2 mixtures cannot be explained by this mechanism. The shock-tube data can be explained by the following scheme, if a water vapor content of 20 ppm or less is assumed: C O + O 2 → k i C O 2 + O O + H 2 O → k 5 2 O H O H + C O → k 6 C O 2 + H H + O 2 → k 2 ' O H + O The rate constant for the initiation reaction was found to be k i = 2.5 × 10 9 exp ⁡ ( − 48 , 000 / R T ) l i t e r s m o l e − 1 sec ⁡ − 1 . The rate constant for the reaction between O and H2O at 1600°K was estimated by two different methods to be 8×108 and 1.5×109 liters mole−1 sec−1. Induction periods for mixtures with deliberate additions of hydrogen can be fit by adding the steps O + H 2 → k 3 ' O H + H O H + H 2 → k 1 ' H 2 O + H