Influence of the Preparation Method and Metal Precursor Compound on Alumina-Supported Pd Catalysts

Supported palladium catalysts were prepared by two different methods: wet impregnation and incipient-wetness impregnation. Commercial gamma-Al2O3 and sol-gel derived alumina were used as support. The synthesis of alumina xerogel was carried out by hydrolysis of aluminum isopropoxide (AIP) in 2-propanol solution. Organometallic -Pd(C5H7O2)2- and inorganic precursor -Pd(NH3)4Cl2.H2O- were used for the synthesis of the catalytic systems. Samples were characterized by BET surface area measurement, atomic absorption spectroscopy (AAS), X-ray diffraction (XRD), temperature-programmed reduction (TPR), and hydrogen chemisorption. The activity of these catalysts was studied for the stoichiometric reduction of NO by methane. The decomposition of NO and methane oxidation were also used as a test reaction. Catalyst prepared by wet impregnation method using Pd(C5H7O2)2 and alumina xerogel presented the best performance for the studied reaction. The activity of Pd/alumina catalysts for NO-CH4 reaction is related to the facility for reduction/oxidation of the metal. This property is affected by the nature of the support as well as the metal precursor.