Thermal stability and SO2 resistance of Pd/Rh-perovskite based three-way catalyst wash-coated on cordierite monoliths

The effect of hydrothermal aging and SO2 poisoning on the three-way catalytic performance of dispersed Pd/Rh-based and Pd/Rh perovskite-based catalysts were studied by using a dynamic activity test system that simulates redox fluctuations of gasoline engine exhaust conditions. Both catalysts were supported on ceria-zirconia-alumina and wash-coated on cordierite monoliths and were characterized by ICP-OES, BET, XRD, TEM-EDX, DRIFTS, and CO chemisorption. Their performance was very close when the catalysts were fresh but, after 3 h of hydrothermal aging at 1000 degrees C, the dispersed Pd/Rh-based catalyst lost its performance especially with respect to C3H8 and NO conversions; however, the Pd/Rh perovskite-based catalyst kept its activity. Parallel to that, CO uptake capacity losses after hydrothermal aging were 85% and 30% for the dispersed metallic catalyst and the perovskite-based catalyst, respectively. Moreover, 20 ppm SO2 exposure decreased CO uptake capacities by 61% and 48% for the two catalysts, respectively.