Characterization of Pd–Au/SiO₂ Catalysts by X-ray Diffraction, Temperature-Programmed Hydride Decomposition, and Catalytic Probes

Author： Bonarowska M. Pielaszek J. Juszczyk W. Karpin´ski Z.

Publisher： Academic Press

ISSN： 0021-9517

Source： Journal of Catalysis, Vol.195, Iss.2, 2000-10, pp. : 304-315

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Abstract

Two series of Pd–Au/SiO₂ catalysts, differing widely in metal particle size distribution, were prepared by a direct redox method, which involves reductive deposition of gold onto prereduced palladium particles. The method yields good results; i.e., a significant Pd–Au alloying was achieved in reduced bimetallic catalysts. The catalysts were investigated at various stages of their preparation by X-ray diffraction and temperature-programmed hydride decomposition. These techniques appear valuable in assessing the degree of alloying. Being sensitive to palladium particle size, the temperature-programmed hydride decomposition could also be applied to estimate the palladium dispersion. 2,2-Dimethylpropane conversion carried out on Pd–Au/SiO₂ also appeared to be a useful probe. Apparent activation energy decreased considerably with gold addition. This result is contrary to a relative constancy of the activation energy observed earlier for Pd–Au/SiO₂ catalysts, which were prepared by an incipient wetness coimpregnation when the resulting bimetallic samples were not satisfactorily homogenized.