INHIBITION OF THE THERMAL REACTION BETWEEN HYDROGEN AND OXYGEN.

Abstract : The kinetics of the inhibiting action of hydrogen bromide and hydrogen chloride on the thermal reaction between hydrogen and oxygen was investigated. Hydrogen bromide was found to be a very effective inhibitor of the reaction, while hydrogen chloride was relatively inefficient. The kinetic characteristics of the inhibition were examined, and it was shown that in the case of hydrogen bromide the primary inhibition step is: H + HBr yields H2 + Br. Only a fraction of the bromine atoms produced in this reaction react to give chain termination, however, and the majority react to give chain propagation by: Br + H2 yields HBr + H. It is suggested that chain termination occurs by: Br + HO2 yields HBr + O2. The corresponding mechanism is also operative when hydrogen chloride is the inhibitor, but a second primary inhibition step is also important in this case: OH + HCl yields H2O + Cl. The reason for the marked difference in efficiency of hydrogen bromide and hydrogen chloride is discussed. (Author)