Microwave-assisted in-situ regeneration of a perovskite coated diesel soot filter

Dielectric heating may be used as an in situ technique for the periodic regeneration of soot filters, as those used in Diesel engines. As generally the Diesel exhaust temperatures are below the soot light-off temperature, passive regeneration is not possible. Presently, we have investigated the dielectric heating of a monolithic soot filter, coated with a La0.8Ce0.2MnO3 perovskite. This type of perovskite has suitable dielectric properties, i.e., a high dielectric loss factor, and simultaneously acts as an oxidation catalyst. It is shown that a perovskite coated cordierite filter, covered with synthetic carbon, can be fully regenerated with selectivity towards CO2 close to 100%. In contrast, the same filter without such a coating can only be partially regenerated. Moreover, considerable amounts of CO are formed. The La0.8Ce0.2MnO3 coating is shown to have excellent temperature shock resistance and thermo-chemical stability. It is shown that the microwave cavity design is crucial to obtain a uniform filter heating. Following the development of such a design, microwave assisted soot filter regeneration becomes feasible.