Monitoring particle size changes of a supported phase by ESCA

Hoffmann, Douglas P.; Proctor, Andrew; Houalla, Marwan; Hercules, David M.

doi:10.1021/j100167a035

Cited by 6 publications

(5 citation statements)

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“…It has been demonstrated that XPS can be used for monitoring the dispersion of metals as a function of metal loading on supported catalysts [5][6][7][8]. Those studies showed that information about dispersion obtained by using XPS can then be correlated with catalytic activity.…”

Section: Resultsmentioning

confidence: 99%

“…The XPS metal-to-support intensity ratio will be proportional to the metal-to-support atomic ratio if the supported metal is dispersed as a monolayer. A thorough discussion of the model and some selected applications to supported catalysts are described elsewhere [5][6][7][8][9]. Some small modifications were made in the application of the K-M model for the calculation of the Pd/Al intensity ratios for monolayer coverage.…”

Section: Resultsmentioning

confidence: 99%

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Surface characterization of Pd/Al₂O₃sorbents for mercury capture from fuel gas

Baltrus

Granite

Stanko

et al. 2008

Main Group Chemistry

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The surface composition of a series of Pd/alumina sorbents has been characterized to better understand the factors influencing their ability to adsorb mercury from fuel gas. Both a temperature effect and a dispersion effect were found. Maximum adsorption of Hg occurred at the -lowest temperature tested, 204°C, and decreased with increasing temperatures. Maximum adsorption of Hg on a per-atom basis of Pd is observed at low loadings of Pd ( < S.5% Pd) due to better dispersion of Pd at those loadings; a change in its partitioning occurs at higher loadings. The presence of H2S "in the fuel gas acts to promote the adsorption of Hg through its association with Hg in the Pd lattice.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Surface characterization of Pd/Al₂O₃sorbents for mercury capture from fuel gas

Baltrus

Granite

Stanko

et al. 2008

Main Group Chemistry

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“…Understanding of chemical phenomena due to heat treatment of these catalysts is of fundamental interest because thermal treatment can influence the morphology, stability, chemical nature, and activity of supported metal catalysts. Previous investigations on thermal behavior have mainly focused on the metal catalysts dispersed on silica, alumina, magnesia, carbon, and zeolite supports. − These catalysts are commonly prepared by impregnation, ion exchange, coprecipitation, and deposition methods. Chen et al have shown the diffusion of Rh from the top surface layer to bulk Al 2 O 3 upon heating Rh/Al 2 O 3 at 825 °C.…”

Section: Introductionmentioning

confidence: 99%

Ionic Dispersion of Pt over CeO₂ by the Combustion Method: Structural Investigation by XRD, TEM, XPS, and EXAFS

et al. 2003

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The structure and chemical nature of Pt in combustion-synthesized Pt/CeO2 catalysts have been investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), extended X-ray absorption fine structure (EXAFS), and temperature-programmed reaction (TPR). Catalytic oxidation of CO over Pt/CeO2 is correlated with its structure. High-resolution XRD studies show that the structure could be refined for the composition of Ce1 - x Pt x O2 - δ in the fluorite structure with 6% oxide ion vacancy. TEM images show very few Pt particles on the CeO2 crystallite surface in as-prepared samples and a decrease in the density of Pt metal particles is observed on heating. XPS studies demonstrate that Pt is dispersed mostly in +2 (72%) and +4 (21%) oxidation states on CeO2, whereas only 7% is present as Pt metal particles. On heat treatment, Pt2+ species increase at the cost of Pt4+ ions. EXAFS studies show the average coordination number of 1.3 around the platinum ion in the first shell of 1% Pt/CeO2 at a distance of 1.98 Å, indicating oxide ion vacancy around the platinum ion. On heating, the average oxygen coordination of Pt and oxygen increases to 2.3. The second shell at 2.97 Å is due to Pt−Pt coordination, which is absent in PtO2 and PtO. The third shell at 3.28 Å is not observed either in Pt metal or any of the platinum oxides, which could be attributed to Pt2+−Ce4+ correlation. Thus, Pt/CeO2 forms a Ce1 - x Pt x O2 - δ type of solid solution having −□−Pt2+−O−Ce4+− kinds of linkages.

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“…An interesting group of binary oxides used in catalytic and magnetic applications is that of the oxides formed in the Fe−Al system ,, . Likewise, the surface oxide on bulk Fe−Al alloys plays an important role in high-temperature applications because it determines the corrosion resistance and bonding properties of the alloy.…”

Section: Introductionmentioning

confidence: 99%

Oxidation of Iron Deposited on PolycrystallineAluminum Surfaces

and

Arranz

2001

J. Phys. Chem. B

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The interaction of oxygen with iron deposited on polycrystalline aluminum surfaces has been investigated using AES, XPS, and ARXPS. The growth of the iron on the aluminum surfaces occurs in two stages: formation of FeAl islands 10-ML thick up to a coverage of θ FeAl ≈0.65, followed by the formation of metallic iron islands 8-ML thick that grow over the intermetallic islands previously formed. For surfaces containing FeAl islands alone, the chemical information obtained by the analytical techniques shows that oxygen exposure causes the formation of aluminum intermediate oxidation states Al 2+ and Al 1+ , in addition to Al 3+ , which are attributed to the formation of Al-O-Fe cross-linking bonds at the interface. The analysis of the Fe 2p peak shape shows that no iron oxide is formed, the small changes observed in this band being attributed to Fe atoms in an aluminum depleted layer at the interface. The oxidation of surfaces containing iron islands leads to results consistent with the formation of an Fe 2 O 3 oxide film that grow over a film containing a mixture of intermediate aluminum and iron oxidation states.

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Monitoring particle size changes of a supported phase by ESCA

Cited by 6 publications

References 0 publications

Surface characterization of Pd/Al₂O₃sorbents for mercury capture from fuel gas

Surface characterization of Pd/Al₂O₃sorbents for mercury capture from fuel gas

Ionic Dispersion of Pt over CeO₂ by the Combustion Method: Structural Investigation by XRD, TEM, XPS, and EXAFS

Oxidation of Iron Deposited on PolycrystallineAluminum Surfaces

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Monitoring particle size changes of a supported phase by ESCA

Cited by 6 publications

References 0 publications

Surface characterization of Pd/Al2O3sorbents for mercury capture from fuel gas

Surface characterization of Pd/Al2O3sorbents for mercury capture from fuel gas

Ionic Dispersion of Pt over CeO2 by the Combustion Method: Structural Investigation by XRD, TEM, XPS, and EXAFS

Oxidation of Iron Deposited on PolycrystallineAluminum Surfaces

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Product

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Surface characterization of Pd/Al₂O₃sorbents for mercury capture from fuel gas

Surface characterization of Pd/Al₂O₃sorbents for mercury capture from fuel gas

Ionic Dispersion of Pt over CeO₂ by the Combustion Method: Structural Investigation by XRD, TEM, XPS, and EXAFS