Pd-Pt/Al<sub>2</sub>O<sub>3</sub> catalysts: preparation by redox reactions, characterization and catalytic activity

Micheaud, C; Marécot, P.; Guérin, M.; Barbier, J.

doi:10.1051/jcp/1997941897

Cited by 5 publications

(2 citation statements)

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“…In the presence of preadsorbed hydrogen, Pt was located as a "decoration" on low-coordination sites of Pd. Deposition of Pt by direct redox reactions brought it on to low Millerindex Pd faces, like (111) [26]. This latter method led ultimately to "more intimately mixed bimetallic system".…”

Section: Introductionmentioning

confidence: 99%

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Palladium-platinum powder catalysts manufactured by colloid synthesis

Győrffy

Tóth

Bartók

et al. 2005

Journal of Molecular Catalysis A: Chemical

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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 cisand trans-methyl-ethylcyclopropane (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 CC rupture, due, very likely, to the presence of active Pd-Pt ensembles.

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Section: Introductionmentioning

confidence: 99%

“…This latter method led ultimately to "more intimately mixed bimetallic system". The importance of oxygen treatment is evident, since these catalysts were also tested in 18 O/ 16 O exchange reactions at 723 K [26]. O 2 -H 2 titration reportedly promoted segregation of Pt and Pd [27].…”

Section: Introductionmentioning

confidence: 99%