Selectivity of hydrogen chemisorption on clean and lead modified palladium particles; a TPD and photoemission study

Paál, Z.; Loose, G.; Weinberg, Gisela; Rebholz, M.; Schlögl, Robert

doi:10.1007/bf00763996

Cited by 8 publications

(5 citation statements)

References 14 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The Pd 3d lines show a completely different picture ( Figure 3). The BE of PdO and Pd silicides were reported to be between 336.3 and 336.8 eV [35,36]. The Pd sample was profoundly oxidized after C, the amount of Pd n+ exceeding that of Pd 0 .…”

Section: Catalytic Measurementsmentioning

confidence: 99%

Palladium-platinum powder catalysts manufactured by colloid synthesis

Győrffy

Tóth

Bartók

et al. 2005

Journal of Molecular Catalysis A: Chemical

View full text Add to dashboard Cite

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.

show abstract

Section: Catalytic Measurementsmentioning

confidence: 99%

Palladium-platinum powder catalysts manufactured by colloid synthesis

Győrffy

Tóth

Bartók

et al. 2005

Journal of Molecular Catalysis A: Chemical

View full text Add to dashboard Cite

show abstract

“…The broad band at ca. 13 eV is due to water. All Case history: sample 4 was regenerated to sample 1; sample 6 was regenerated to sample 2; sample 7 was regenerated to sample 3.…”

Section: Photoelectron Spectroscopy Of Purified Pt Black Samplesmentioning

confidence: 99%

Photoelectron spectroscopy of polycrystalline platinum catalysts

Paál¹,

Schlögl²,

Ertl³

1992

J. Chem. Soc., Faraday Trans.

View full text Add to dashboard Cite

Pt black catalysts have been characterized by X-ray photoelectron spectroscopy (XPS) and ultraviolet photoelectron spectroscopy (UPS). The spectra measured after standard purification (O2 and H2 at 600 K) compared well with those of a purified reference Pt foil. All samples exhibited pronounced Fermi-edge intensities in UPS although only 60–70% Pt was detected on their surfaces by XPS, the remainder being C and O. Line analysis of the C 1s XPS, region showed the presence of partly oxidized graphite and hydrocarbon polymer, likely in three-dimensional islands. OH/H2O species attached to the metallic Pt sites were detected by UPS bands, in agreement with O 1s XPS line analysis. Similar spectral features are recorded at 600 K. Carbon could not be removed entirely by O2 up to 850 K; hydrogen did not remove surface oxygen even up to 750 K. UPS features of C on Pt used in hydrocarbon reactions were similar to those reported for amorphous hydrogenated carbon overlayers. Consequences of the present findings for the catalytic properties of Pt in n-hexane reactions and the quantification of H2–O2 titration are discussed briefly

show abstract

“…TPD study of PdH-dec/Al 2 O 3 confirms this assumption (Figure ) and demonstrates lower stability and content of Pd hydride in the sample (Table ). Earlier studies show decrease of H/Pd ratio in hydrides and temperature of decomposition with decrease of the size of Pd nanoparticles. , …”

mentioning

confidence: 88%

“…Earlier studies show decrease of H/Pd ratio in hydrides and temperature of decomposition with decrease of the size of Pd nanoparticles. 23,24 The effect of increase of the dispersion of Pd could be the result of the interaction of Pd with hydrogen peroxide and increase of the mobility of Pd on the surface of alumina. In order to check this effect, the catalyst was treated by hydrogen peroxide without preliminary hydrogen absorption, which is denoted as Pd-dec/Al 2 O 3 .…”

mentioning

confidence: 99%