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4904551 
Journal Article 
Palladium-platinum powder catalysts manufactured by colloid synthesis II. Characterization and catalytic tests after oxidizing and reducing treatment 
Gyorffy, N; Toth, L; Bartok, M; Ocsko, J; Wild, U; Schlogl, R; Teschner, D; Paal, Z 
2005 
Yes 
Journal of Molecular Catalysis A: Chemical
ISSN: 1381-1169 
ELSEVIER SCIENCE BV 
AMSTERDAM 
238 
1-2 
102-110 
English 
WOS:000231018800014 
Unsupported Pd, Pt and PdPt bimetallic catalysts were prepared in different atomic ratios using methods of colloid chemistry. They were characterized by XPS, UPS and TEM. Four subsequent treatments with O-2 and H-2 up to T= 603 K were applied in the preparation chamber of the electron spectrometer and before the catalytic runs. Platinum strongly hindered the oxidation of palladium in the bimetallic samples indicating an alloying of the two components. The H-2 treatment after O-2 led to rather clean metals. These treatments up to 603 K decreased the Pt enrichment near to the surface found by XPS, destroying presumably the Pt islands on the surface of a Pd-rich matrix. The particle composition approached thus a homogeneous metal mixture. The catalytic behavior was tested in the hydrogenative ring opening reaction of cis- and trans-methyl-ethyl-cyclopropane (MECP) at 373 K. The product ratios 2-methylpentane/3-methylpentane (2MP/3MP) and 2-methylpentane/n-hexane (2MP/nH) were used to characterize the ring-opening pattern of the samples. The bimetallic catalysts revealed higher activity and completely different selectivities than the monometallic Pt and Pd. Moreover, the 2MP/3MP ratio from trans-MECP and 2MP/nH ratio from cis-MECP increased as the surface Pt enrichment decreased. PdPt catalysts were cleaner than Pd or Pt, their activity higher and selectivity closer to random C-C rupture, due, very likely, to the presence of active Pd-Pt ensembles. (c) 2005 Elsevier B.V. All rights reserved. 
bimetallic catalyst; Pd; Pt; cyclopropane ring opening; XPS; UPS