In situ deposition of silver and palladium nanoparticles prepared by the polyol process, and their performance as catalytic converters of automobile exhaust gases

摘要

In situ deposition of silver particles onto alumina and palladium particles onto mixed Ce-Zr oxides has been achieved upon chemical reduction of the corresponding metal species (AgNO_3 and PdCl_2) by ethylene glycol in the presence of polyvinylpyrrolidone. The support oxide powders were found to keep their crystalline structure and morphology after treatment with hot ethylene glycol while the BET surface area decreased after metal deposition. Microprobe maps obtained from energy dispersive X-ray analysis revealed a homogeneous distribution of metal nanoparticles on the surfaces of alumina and of the mixed Ce-Zr oxides. Supported silver and palladium were tested as catalytic converters of simulated exhaust automobile gases. The catalytic activity of silver-loaded alumina powder catalyst for CO and hydrocarbon oxidation as well as NO and NO_x reduction, was found to be higher than that of a reference silver catalyst. Palladium-loaded mixed Ce-Zr oxides powder catalyst showed a similar performance to that of a reference palladium catalyst as a three-way catalyst converter.