Kinetics of catalyzed and non‐catalyzed soot oxidation with nitrogen dioxide under regeneration particle trap conditions

BACKGROUND: For compliance with the regulations on diesel particulate matter, car manufacturers have developed diesel particulate filters (DPF). These technologies require a regeneration method which oxidizes soot deposits in the filter. In diesel exhaust emissions there are two suitable oxidizing gases: oxygen and nitrogen dioxide. Nitrogen dioxide is much more active than O 2 and can directly attack the carbon surface. This work describes the kinetics of the oxidation of soot by NO 2 over a wide range of conditions relevant for DPF. RESULTS: The catalyzed and the non‐catalyzed oxidation of soot have been performed in a fixed‐bed reactor. The experimental results show that the overall oxidation process can be described by two additive parallel reactions: a direct C − NO 2 reaction catalyzed by H 2 O and a cooperative C − NO 2 − O 2 reaction catalyzed by the Pt/Al 2 O 3 catalyst. The results obtained allow to propose the following kinetic law for the specific rates of the catalyzed and the non‐catalyzed oxidation of soot in the regeneration filter conditions:$$\eqalign{ r\left(s^{-1}\right) &= 0.48\ \exp \left({-\,26700\over RT}\right)X_{NO_{2}}^{0.6} + 1395\ \exp \left({-\,47800\over RT}\right) X_{NO_{2}}X_{O_{2}}^{0.3} \cr r_{cat}\left(s^{-1}\right) &= 0.51\ \exp \left({-\,26800\over RT}\right)X_{NO_{2}}^{0.6} + 51.4\ \exp \left({-\,52200\over RT}\right)\ X_{NO_{2}}^{0.4}X_{O_{2}}^{0.3} \cr }$$CONCLUSION: The kinetic parameters describing the oxidation rate of soot by NO 2 over a range of temperature and gas composition have been obtained. The extracted kinetics data are relevant for modeling the removal of trapping soot in automotive gas exhaust technology. Copyright © 2009 Society of Chemical Industry