Recent Trends in the Application of Tri-Metal Emission Control Catalysts 940928
The use of Pd together with Pt/Rh in automotive emission control catalytic converters is discussed. The drawbacks and advantages of Pd are explained for the conversion of CO, HC and NOx. The performance of high loaded Pd-only catalysts is demonstrated in vehicle tests according to the FTP75, ECE and Japan-10-mode procedures. It is shown that the advantageous lean HC-light-off temperature observed with high loaded Pd-only catalyst can also be reached with similar loaded Pt-only catalysts. Various alternative ways to incorporate Pd in multi-brick converters are evaluated in vehicle tests. It is shown that single brick three metal converters with high Pd-content can have advantages over conventional Pt/Rh-three way catalysts. However, the extent of the improvement depends strongly upon the particular application, and with the present trend of increasing Pd-prices these three metal converters might lead to increased precious metal costs over conventional Pt/Rh-catalysts.