Sathiamoorthy, B., Graper, A., McIntosh, A., and Kaminski, W., "The Benefits and Challenges Faced by Aftermarket Catalyst Manufacturers in Implementing Advanced Coating Techniques in TWC (Gasoline Applications)," SAE Technical Paper 2017-01-0921, 2017, doi:10.4271/2017-01-0921.
The automotive aftermarket industry is an extremely cost competitive market to say the least. Aftermarket manufacturers are sought by customers primarily for their ability to replace an OES (Original Equipment Supplier) for a fraction of the cost. This forces the manufacturers to yield on performance abilities to get a share in the market place. The TWC system in gasoline vehicles not only acts as an emissions reduction device but is an integral part of the overall vehicle performance itself, especially since the introduction of OBD (On-Board Diagnostics) II systems in 1995. An inefficient catalyst not only leads to excessive tailpipe emissions but also acts detrimental to vehicle fueling and hence overall performance. The aftermarket catalyst industry which is regulated by EPA (United States Environmental Protection Agency) and CARB (California Air Resource Board) for gasoline engines is subject to meeting a mandatory performance standard for the same reason. There are several advancements in catalyst technologies to gain performance but this may or may not apply to the aftermarket manufacturers.This paper will discuss three established coating techniques in TWC (Three Way Catalyst) catalyst and their influence on PGM (Precious Group Metal) reduction, emissions performance, and cost reduction and production feasibility. The first method is referred to as slurry coating and possibly the easiest coating method, PGM+WC (Wash Coat) slurry where all precious metals and the supporting washcoat is mixed and applied as one slurry. The second method is referred to as layer coating where the Palladium is in the slurry solution with the washcoat and coated as the first layer on the substrate and then the Rhodium is layered on top as a metal impregnation. The third method is referred to as zone coating where the palladium is in the slurry with the washcoat and it is coated in the inlet of the substrate, while the Rhodium is in the slurry with the washcoat and it is coated in the outlet of the substrate.