| abstract |
Passive NO x adsorption (PNA) compositions have a formula Pd—NiFe 2 O 4 wherein Pd represents a palladium component, such as palladium oxide, that is adsorbed on surfaces of the nickel ferrite. Such compositions can be synthesized by wet impregnation of nickel ferrite with a palladium salt, and exhibit efficient NO x adsorption at low temperature, with NO x desorption occurring predominantly at high temperature. Two-stage NO x abatement catalysts, effective under engine cold start conditions, include a PNA composition upstream from an NO x conversion catalyst. |