ANALYSIS OF HYDROCARBON POISONING FOR PD CATALYSTS

Hydrocarbon(HC) poisoning for Pd catalysts has been investigated. Adso rbed species on deteriorated Pd catalysts were analyzed by various met hods such as GC-MS, FT-IR, XPS etc. The relations of the oxidation sta tes of Pd, Al and Ce of Pd/Al2O3 and Pd/CeO2 with the HC chemisorption were examined. It was concluded that the cause of deterioration of Pd /Al2O3 was due to the decrease of the number of active sites by HC che misorption, and that the cause of deterioration of Pd/CeO2 was due to the decrease of O-2 storage capacity by HC chemisorption. Particularly , the mechanism of the decrease of O-2 storage capacity was that HC be came to adsorb on the position the oxygen vacancies of CeO2. It was cl arified that the performance of deteriorated Pd catalysts was regenera ted by heat treatment at 500 degrees C for 1 hour in the air.