Experimental investigation of soot oxidation characteristic with NO ₂ and O₂ using a flow reactor simulating DPF

Characteristics of soot oxidation were investigated with a carbon black (Printex-U). A flow reactor system which can simulate the condition of diesel particulate filter and diesel exhaust gas (1 bar, O₂ 0 ∼ 10%, NO₂ 200 ∼ 900ppm) was designed and used with the temperature programmed oxidation (TPO) and constant temperature oxidation (CTO) techniques. The temperature increase rate was 5°C/min for TPO experiments. From the experiments, the apparent activation energy for carbon oxidation with nitrogen dioxide was determined as 60 ± 3 kJ/mol with the first order of carbon in the range of 10∼90% oxidation and the temperature range of 250∼500°C. This value was exceedingly lower than the activation energy of oxygen oxidation which was 177 ± 1 kJ/mol. When oxygen exists with nitrogen dioxide, the reaction rate increased with the concentration of oxygen. Its rate of increase was faster for low oxygen concentration and slower for high concentration.