The Effect of Palladium on the Performance of Three-Way Catalyst

There is a great interest in the use of palladium in automotive emission control catalysts because of cost and availability. On the above basis, we made a prompt effort to replace platinum by palladium in conventional platinum/rhodium systems. This paper reports the performance of aged palladium containing three-way catalysts in the laboratory.

Increasing the palladium and rhodium loading from 0.5 g/1 and 0.1 g/1, respectively, to 1.0 g/1 and 0.2 g/1, respectively, resulted in improved catalyst light-off and conversion performances. The light-off performance under the dynamic conditions improved with the increasing A/F perturbation until the optimum value, and its behavior was different from platinum/rhodium catalyst. The effect of palladium on the durability performance of the palladium/rhodium catalyst was compared with that of the platinum/palladium/rhodium catalyst. Further studies were done in the characterization of catalysts and the surface enrichment of palladium-rhodium and platinum-rhodium alloy systems heated in air and hydrogen.