Preparation and Morphological Characterization of a Catalytic Soot Oxidation SiC Foam Filter

The coating characteristics of Pb-Co mixed metal oxide soot oxidation catalysts over a SiC foam filter were studied. The coating was done via incipient wetness impregnation of a slurry with Pb/Co weight ratio = 2. The coating was accomplished by 3 consecutive impregnation-drying-calcination cycles. After each cycle surface structure and composition were monitored by scanning electron microscope (SEM). SEM analysis revealed that the surface composition of Pb was high on the high porosity region and surface composition of Co was high on the low porosity region inside the filter. These overlayers were tested for their soot oxidation ability by depositing paraffin soot from a candle flame, thermally oxidizing, and collecting SEM pictures before and after oxidation. SEM pictures after soot deposition/oxidation cycles revealed that high amounts of Pb were necessary for efficient removal of soot. However, Pb composition of the surface decreased due to the evaporative loss of Pb.