CeMn/AlSiO ceramic layers on metallic supports for high-temperature catalytic processes

The CeO2-Mn/SiO2Al2O3 coating (also as Al2O3 or A1OOH•H2O) on metallic supports was fund to be best suited for high-temperature catalytic oxidation of diesel soot. With a thickness of 15-20 m, the ceramic layer coated by the sol-gel method showed no cracks either before or after a thermal shock. Scanning micrographs revealed a tight contact between coating and substrate. The crystallites of active cerium oxides were uniformly distributed in the top part of the layer. No segregation of Cr or Fe from substrate bulk to surface was evidenced, but - advantageously - it was Al that segregated (surface concentration rose from 14 to 24 wt. %), forming a protective layer on the metal surface and a bond with SiO2/Al2O3 coated by the sol-gel method. Making use of DTA and DTG techniques, the catalytic activity of the coating in the diesel soot oxidation reaction was determined. Two temperature peaks (at 350 °C and 470 °C) corresponding to the maxima of the soot oxidation rate were distinguished.