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

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 omega was obtained: log(omega/g cm(-2) s(-1) = log A + 0.5 log([O-2]/mol cm(-3)) - (6366/T) with log A = 3.731 +/- 0.1, giving an activation energy of 121.9 +/- 2.5 kJ mol(-1) or log(omega/g cm(-2) s(-1)) = log B + 0.5 log([P(O-2)]/atm) - (6048/T) 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, alpha, for the attack of oxygen molecules on soot can be calculated to be alpha = 3.45 exp(-14919/T) 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.