Soot oxidation in diesel exhaust on manganese oxide catalyst prepared by flame spray pyrolysis

A Mn2O3 catalyst prepared by flame spray pyrolysis was physico-chemically characterized and tested for the oxidation of soot in diesel model exhaust. A special focus lay on the effect of O-2 on the kinetics and local temperatures. The catalyst was tightly mixed with model soot Printex U and was evaluated by temperature programmed oxidation. The catalytic tests showed significant temperature gradients inside the Mn2O3/soot bed already at low O-2 proportions (1 vol.%), whereas hot spots appeared at 5 vol.% O-2 and above strongly affecting local oxidation rates. Furthermore, kinetic studies were carried out with diluted catalyst/soot mixtures providing homogenous temperature distribution. Based on these results, a global kinetic model was constructed inferring the evolution of the surface area of the soot, the number of reactive carbon sites and the reaction order of soot and O-2. Finally, the kinetic model was validated by prediction of experimental data.