W. B. Williamson

Durability of Palladium Only Three-way Automotive Emisson Control Catalysts

The noble metal palladium (Pd) has the capability of simultaneously converting significant quantities of HC, CO and NO/sub x/ in automotive exhaust. Primary interests in using palladium-containing TWC catalysts are overall noble metal cost reduction, reduction in rhodium usage and important performance advantages. Dynamometer aging experiments comparing palladium and platinum/rhodium catalysts were conducted under a variety of operating conditions. Vehicle evaluation of these aged catalysts under U.S. FTP-75, European ECE-15 and Japan 10-Mode conditions indicate that palladium-only TWC technology is vaiable for achieving high levels of three-way control. Vehicle aging studies (25K miles) were also conducted. The results of these studies are discussed in this work.

Uses of Palladium in Automotive Emission Control Catalysts

On a signal basis there is a resurgence of interest in the use of palladium in automotive emission control catalysts because of cost, availability and performance advantages under certain operating conditions relative to more expensive noble metals. This paper reviews a variety of potential vehicle applications for the use of palladium containing catalysts. Included in the study are for the replacement of platinum by palladium in conventional platinum/rhodium systems, palladium-only three-way catalysts, palladium-only three-way catalysts, palladium-only dual bed catalysts and two-stroke and lean-burn engine applications.

Performance of Copper Base Metal Catalysts in Stoichiometric Automotive Exhausts

Durability performance characteristics of copper-containing base metal catalysts and base metallow noble metal catalysts have been determined in laboratory and engine aging conditions under well controlled stoichiometric closed-loop AF operation. Cu-Cr base metal formulations yield significant HC and CO conversions under stoichiometric operation after aging at 620/sup 0/C, but deteriorate rapidly at high-temperature (750/sup 0/C inlet) stoichiometric operation. Incorporation of Rh into the base metal formulation substantially improved NO/sub x/ performance, a major weakness of base metal catalysts. The addition of Cu-Cr base metals substantially improves CO oxidation over Pt, Pd, and Rh catalysts but was accompanied by some loss of HC conversion over Pt and Rh. A Cu-CrPd catalyst, however, also had better HC conversions as well as significantly improved light-off performance when compared to a Pd-only catalyst. The stoichiometric operating strategy and performance envelope for base metal catalysts were probed in engine dynamometer and vehicle studies. The aged performance of the Cu containing catalysts is significantly lowered by lean AF preconditioning due probably to sulfur poisoning of Cu at low-temperature lean operating conditions.