Zeolite Supported Pd Catalysts for Low Temperature NO and HC storage
Hai-Ying Chen, Johnson Matthey Inc.
Control of emissions at low temperatures, especially during the cold start periods of a vehicle operation, is one of the main challenges for fuel efficient vehicles to meet the stringent emission regulations. Recent development effort at Johnson Matthey has led to the discovery of zeolite supported Pd catalysts that are capable of adsorbing NO and HC at temperatures below ~200C with high storage efficiency and capacities. The materials also show high resistance to SO2 poisoning. The NO storage temperature profiles as well as the NO release temperature profiles of the Pd-zeolite materials are significantly affected by the framework structures of the zeolite supports. A detailed study focusing on the characterisation of the Pd storage sites on zeolites and comparing them to oxide supports to understand the unique nature of the active species in these materials will be presented. Examples of full exhaust emission control systems will be provided to illustrate the benefits of the zeolite supported Pd catalysts in enabling cold start diesel emission control. Modelling work to optimize system configurations will also be discussed.