Neue Phasen vom MnP (B 31)-Typ

Pfisterer, H.; Schubert, K.

doi:10.1007/bf00623719

Cited by 40 publications

(18 citation statements)

References 1 publication

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“…Recent magnetic measurements of the bulk susceptibility and n.m.r, parameters (Weaver, Knauer, Quinn & Baughman, 1972) have provided information regarding the nature of the conduction electrons. Interestingly, the appearance of two overlapping peaks in the '95pt n.m.r, spectra is not consistent with the published structure of PtSi (Pfisterer & Schubert, 1950: hereafter P & S) which possesses only one symmetry site for Pt. Diffraction photographs to determine the correctness of the space group were taken below, at and above room temperature in order to corroborate the n.m.r, results; however, these photographs were found to be consistent with the results of P & S. Furthermore, these photographs suggested that the value of the linear thermal expansivity along the c axis greatly differed from those along the other two axes.…”

Section: Introductioncontrasting

confidence: 63%

Crystal structure and linear thermal expansitivities of platinum silicide and platinum germanide

Graeber¹,

Baughman²,

Morosin³

1973

Acta Crystallogr Sect B

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Positional and thermal parameters for PtSi and PtGe have been refined by the full-matrix least-squares method using 123 and 131 three-dimensional intensity data, reslzectively. The compounds are isostructural with MnP, space group Pbnm, four formulae per cell, with lattice constants a=5"916 (1), b= 5.577 (1), c=3.587 (1)/~ for PtSi, and a=6"084 (2), b=5.719 (2), c=3.697 (1)/~ for PtGe. Linear thermal expansivities have been determined from the lattice constants measured as a function of temperature over the interval 100-900 °K for PtSi and 298-900 °K for PtGe. An anomaly in the expansivities for PtSi occurs at 400°K.

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Section: Introductioncontrasting

confidence: 63%

Crystal structure and linear thermal expansitivities of platinum silicide and platinum germanide

Graeber¹,

Baughman²,

Morosin³

1973

Acta Crystallogr Sect B

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“…After reduction at 723 K, bimetallic formation led to the formation of an even Ge-richer PdGe bimetallic. This phase is identified by its very small peaks at 3.046 Å, 2.697 Å and 2.165 Å (marked by black squares), corresponding to the (101), (111) and (211) lattice planes of orthorhombic PdGe [40]. However, Pd 2 Ge still persists.…”

Section: Pd/snomentioning

confidence: 99%

Origin of different deactivation of Pd/SnO2 and Pd/GeO2 catalysts in methanol dehydrogenation and reforming: A comparative study

Lorenz

Zhao

Turner

et al. 2010

Applied Catalysis A: General

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Pd particles supported on SnO2 and GeO2 have been structurally investigated by X-ray diffraction, (High-Resolution) transmission and scanning electron microscopy after different reductive treatments to monitor the eventual formation of bimetallic phases and catalytically tested in methanol dehydrogenation/reforming. For both oxides this included a thin film sample with well-defined Pd particles and a powder catalyst prepared by incipient wetness impregnation. The hexagonal and the tetragonal polymorph were studied for powder GeO2. Pd2Ge formation was observed on all GeO2-supported catalysts, strongly depending on the specific sample used. Reduction of the thin film at 573 K resulted in full transformation into the bimetallic state. The partial solubility of hexagonal GeO2 in water and its thermal structural instability yielded Pd2Ge formation at 473 K, at the cost of a structurally inhomogeneous support and Ge metal formation at higher reduction temperatures. Pd on tetragonal GeO2 entered a state of strong metal-support interaction after reduction at 573-673 K, resulting in coalescing Pd2Ge particles on a sintered and re-crystallized support, apparently partially covering the bimetallic particles and decreasing the catalytic activity. Pd2Ge on amorphous thin film and hexagonal GeO2 converted methanol primarily via dehydrogenation to CO and H2. At 573 K, formation of Pd2Sn and also PdSn occurred on the Pd/SnO2 thin film. Pd3Sn2 (and to some extent Pd2Sn) were predominantly obtained on the respective powder catalyst. Strong deactivation with increasing reduction temperature was observed, likely not based on the classical strong metal-support interaction effect, but rather on a combination of missing active structural ensembles on Sn-enriched bimetallic phases and the formation of metallic β-Sn. Correlations to Pd and its bimetallics supported on ZnO, Ga2O3 and In2O3 were also discussed.

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“…In the intermetallic compounds PdGa [18][19][20] and Pd 3 Ga 7 [20][21][22] the Pd atoms are only surrounded by gallium atoms in the first coordination shell and, thus, may be promising catalysts with an improved selectivity and longterm stability in acetylene hydrogenation [23]. Furthermore, modification of the electronic structure by promoting or alloying of the Pd catalyst to tailor adsorption or desorption properties may be employed to increase the selectivity in hydrogenations [6].…”

Section: Experimental T Ure Fmmentioning

confidence: 99%

Palladium–gallium intermetallic compounds for the selective hydrogenation of acetylenePart II: Surface characterization and catalytic performance

Osswald

Kovnir

Armbrüster

et al. 2008

Journal of Catalysis

313

234

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The structurally well-defined intermetallic compounds PdGa and Pd 3 Ga 7 constitute suitable catalysts for the selective hydrogenation of acetylene. The surface properties of PdGa and Pd 3 Ga 7 were characterized by X-ray photoelectron spectroscopy, ion scattering spectroscopy and CO chemisorption. Catalytic activity, selectivity and long-term stability of PdGa and Pd 3 Ga 7 were investigated under different acetylene hydrogenation reaction conditions, in absence and in excess of ethylene, in temperature-programmed and isothermal long-term experiments. Chemical treatment with ammonia solution -performed to remove the gallium oxide layer introduced during the milling procedure from the surface of the intermetallic compounds -yielded a significant increase in activity. Compared to Pd/Al 2 O 3 and Pd 20 Ag 80 reference catalysts, PdGa and Pd 3 Ga 7 exhibited a similar activity per surface area, but higher selectivity and stability. The superior catalytic properties are attributed to the isolation of active Pd sites in the crystallographic structure of PdGa and Pd 3 Ga 7 according to the active-site isolation concept.

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Neue Phasen vom MnP (B 31)-Typ

Cited by 40 publications

References 1 publication

Crystal structure and linear thermal expansitivities of platinum silicide and platinum germanide

Crystal structure and linear thermal expansitivities of platinum silicide and platinum germanide

Origin of different deactivation of Pd/SnO2 and Pd/GeO2 catalysts in methanol dehydrogenation and reforming: A comparative study

Palladium–gallium intermetallic compounds for the selective hydrogenation of acetylenePart II: Surface characterization and catalytic performance

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