The kinetics and mechanism of the slow oxidation of hydrogen

A low‐temperature matrix isolation method has been developed which makes possible the isolation and detection of HO 2 radicalsfrom a gas‐phase radical chain‐reaction system containing atomic H, O and OH radicals as well. The formation of HO 2 radicals is demonstrated in the rarified hydrogen flame. The same radicals are observed to exist during the slow oxidation reaction of hydrogen between the second and third inflammation limits The kinetics of accumulation of HO 2 , H 2 O 2 , and H 2 O has been studied as a function of total pressure, composition of reacting mixtures, temperature, and diameter and the treatmentof the surface of the reaction vessel. It has been established that in a reactor treated with boric acid, the concentration of HO 2 radicalsis in the order of 10 1 2 –10 1 4 particles/cm 3 . The kinetic relationship obtained confirms the necessity of including the following step in the mechanism of slow oxidation of hydrogen: For a quantitative description of the experimental results, calculationsof the complete mechanism of the slow reaction are performed by computer methods. The values of the rate constants of the elementary reactions that enter into the mechanism proposed were taken from published data. Some of them were varied by small intervals to give a better agreement with experimental values. The agreement justifies the mechanism proposed for the experimental conditions employed.