Structural Analysis of Platinum Paladium Nanoparticles Supported on amorphous Silica by High Resolution Electron Microscopy.
N. Castillo, L. Diaz Barriga and R. Pérez
nanoparticles, Pt-Pd, HREM, X-RD
Bimetallic nanoparticles structures and properties are distinct from those of pure elemental clusters. Particularly nanoalloy clusters finely dispersed onto high surface area supports, play an important role in heterogeneous catalysis because the performance of a supported metal catalyst can be related to design, which is crucial for the development of novel catalytic processes[1-3]. Ptx-Pd(1-x) nanoparticles supported on amorphous silica (SiO2) were prepared by wetness impregnation techniques with choroplatinic acid (H2PtCl6) and palladium chloride (PdCl4) with different concentrations of Pt and Pd at about 1% in overall metallic weight. The structural and physic characterization of these samples were carried out by BET Surface Area, X-Rays Diffraction (XRD), Transmission Electron Microscopy (TEM), attach with X-Ray and Energy Dispersive Spectroscopy (XEDS). Our interest in Pt-Pd system has been initiated by both practical and theoretical reasons. Both metals, in supported or unsupported forms, are active in skeletal isomerization, C5-cyclization, aromatization, and, to a lesser extent, hydrogenolysis. Of the two metal blacks, Pd was more selective toward C6 product formation from various hexane isomers than Pt. Compared to the catalysts containing only Pt, Pt alloys are more stable, more selective, and showed higher activity in the conversion of hydrocarbons. By XRD technique we observe that nanoparticles have a single phase alloy, with face centered structure. In this work, we observed the distribution of Pt and Pd in nanoparticle alloy by HREM . Ptx-Pd(1-x) Nanoalloy are made of a single solid solution of Pt and Pd atoms, and the particles diameter of about 4 nm was estimated by HREM and Bright field image, the Pt-Pd nanoparticles were found mainly to have cuboctahedral structures with fcc packing,. by using energy dispersive X-ray spectrometry (XEDS) and their values were found to be close to the stochiometric relative concentrations in weight of the metals in the precursor aqueous solution. .. J.H. Sinfelt, Bimetallic Catalysts-Discoveries, Concepts and Applications, Wiley, New York, 1983.(1958). p. 96. .. M. Campanati, G. Fornasari, A. Vaccari, Catal. Today 77, (2003), p. 299-314. . . Z. Karpinski and T. Koscielki Atalic, Catal. 63, (1980), p. 313-323
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Nanotech 2007 Conference Program Abstract