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Kinetics of the reaction of HO2 with nitric oxide and nitrogen dioxide

1975; Elsevier BV; Volume: 4; Issue: 1-2 Linguagem: Inglês

10.1016/0047-2670(75)80020-7

1873-2658

R. A. Cox, Richard G. Derwent,

Air Quality Monitoring and Forecasting

The photolysis of low concentrations of nitrous acid in CO + N2 + O2 mixtures at 1 atm. has been used as a source of HO2 radicals. The photolyses were carried out in a flow system in which the rates of formation or removal of the oxides of nitrogen, NO and NO2, were measured at small conversion. From the effect of added NO and NO2 on these rates, it is concluded that the following reactions of HO2 radicals with the oxides of nitrogen occur: By computer simulation of the kinetic system using available literature rate constants for the reaction HO2 + HO2 → H2O2 + O2 (8) and the OH-radical reactions which occur, all of the experimental results could be accurately predicted using the following rate constants for the HO2 + NOx reactions at room temperature (296 ± 2K): k5 = 1.2 × 10−12; k10 = 1.4 × 10−13; k7 = 1.2 × 10−13 cm3 molecule−1 s−1. The uncertainty on these rate constants is ± 25%. These values of k5 and k7 are consistent with previous experimental estimates, although k5 has usually been assumed to be approximately a factor of five less than found in this work. The alternative path for NO + HO2, reaction (10), does not appear to have been proposed previously on the basis of experimental observations.