EFFECT OF THE CONTACT BETWEEN CARBON BLACK AND CATALYST PARTICLES ON CARBON OXIDATION RATE: EXPERIMENTS AND MODELLING

The reduction of soot emission from Diesel engines is an important challenge due to their adverse effects on human health and environment. Therefore, Diesel particulate filters (DPF) are used to trap soot in the gas exhaust lines. DPF must be regenerated periodically and/or continuously by burning-off the soot deposit in order to prevent high back pressure level. Catalysts are used to increase the soot combustion rate. They can be added to the fuel in the form of organometallic precursors or coated on the filter. The nature of the soot-catalyst contact is an important parameter for its oxidation.

For this purpose the oxidation of carbon black “CB” used as a model of Diesel soot in presence of a commercial ceria (CeO₂) is investigated to gain a better understanding of the effect of the type of contact between the two solids (loose or tight). Different CB/CeO₂ mixtures are tested in a fixed bed reactor (mass ratio ranging from 10/90 to 50/50). Both isothermal and temperature programmed runs are performed. The mixtures are characterized by scanning electron microscopy (SEM). The experimental data are used to propose a model of CB oxidation in the presence of CeO₂. This model enables to predict with a good agreement the rate of CB combustion obtained experimentally.