Oxidation rates of soot particulates by oxygen in the temperature range 1500–3500 K determined using a shock tube

Abstract

The oxidation rates of soot particulates have been studied at high temperatures (1500–3500 K) in a shock tube in oxygen–argon mixtures at pressures between 4 and 14 atm. Complex Arrhenius plots were found above 2200 K for the lower oxygen concentrations with the rate going through a maximum and then increasing again. Below 2200 K, simple Arrhenius plots were obtained and the order of reaction with respect to oxygen was found to be 0.5.

A final expression for the rate ω was obtained: log(ω/g cm^–2 s^–1)= log A+ 0.5 log([O₂]/mol cm^–3)– [graphic omitted]6366//_T[graphic omitted] with log A= 3.731 ± 0.1, giving an activation energy of 121.9 ± 2.5 kJ mol^–1 or log(ω/g cm^–2 s^–1)= log B+ 0.5 log([P(O₂)]/atm)– [graphic omitted]6048//_T[graphic omitted] with log B= 0.946 ± 0.1, giving an activation energy of 115.8 ± 2.8 kJ mol^–1. From these data the reaction probabilities, α, for the attack of oxygen molecules on soot can be calculated to be α= 3.45 exp[graphic omitted]–14919//_T[graphic omitted] which yields an activation energy of 124 037 J mol^–1.

No effect of total pressure other than that due to increasing oxygen was found. The results have been compared with those obtained by other workers.