Experimental study of the interaction of HO2 radicals with soot surface

Abstract

The reaction of HO₂ with toluene and kerosene flame soot was studied over the temperature range 240–350 K and at P = 0.5–5 Torr of helium using a discharge flow reactor coupled to a modulated molecular beam mass spectrometer. A flat-flame burner was used for the preparation and deposition of soot samples from premixed flames of liquid fuels under well controlled and adjustable combustion conditions. The independent of temperature in the range 240–350 K value of γ = (7.5 ± 1.5) × 10⁻² (calculated with geometric surface area) was found for the uptake coefficient of HO₂ on kerosene and toluene soot. No significant deactivation of soot surface during its reaction with HO₂ was observed. Experiments on soot ageing under ambient conditions showed that the reactivity of aged soot is similar to that of freshly prepared soot samples. The results show that the HO₂ + soot reaction could be a significant loss process for HO_x in the urban atmosphere with a potential impact on photochemical ozone formation. In contrast this process will be negligible in the upper troposphere even in flight corridors.