Effective Rhodium Utilization in Automotive Exhaust Catalysts

On vehicles equipped with fuel shut-off, the rhodium in conventional TWC catalyst tends to strongly interact with the washcoat components during the high temperature lean excursions seen during deceleration. Studies were conducted to elucidate the conditions under which rhodium interacts with the alumina washcoat support and the rare earth components used in some of the new “High Tech” catalyst compositions. Technology was developed which decreased the rhodium interaction with these washcoat components which permits the catalyst to operate under a much broader set of engine control conditions.

Laboratory hydrothermal and engine dynamometer aging studies were used to demonstrate the feasibility of lowering precious metal usage and especially rhodium content of TWC catalysts without sacrificing “High Tech” performance. It is anticipated that this technology will result in lower rhodium TWC catalysts and provide durable catalysts for engine control strategies featuring fuel shut-off or lean A/F ratio calibraiton.