Regular Alumina-Supported Nanoparticles of Iridium, Rhodium and Platinum Under Hydrogen Reduction: Structure, Morphology and Activity in the Neopentane Conversion

Hayek, K.; Goller, Harald; Penner, Simon; Rupprechter, Günther; Zimmermann, Curt

doi:10.1023/b:catl.0000011081.32980.e0

Cited by 37 publications

(27 citation statements)

References 30 publications

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“…29, 39, 40, 47 Similar to SiO 2 , intermetallic compound or alloy formation with participation of Al 2 O 3 needs very harsh reduction conditions at and above 773 K. Al‐Pt alloys and the intermetallic compound AlPt 3 were reported 13. 14, 25, 31, 33, 157 Reduction of Pt/SnO 2 and Pt/In 2 O 3 catalysts at 673 and 523 K caused the formation of the intermetallic compounds SnPt, Sn 2 Pt, Sn 4 Pt, and In 2 Pt, respectively 3. 6, 93, 140 On Pt/V 2 O 3 catalysts, the ordering of the intermetallic compound Pt 3 V, prepared by reduction at 773 K, could be triggered by preoxidation treatments prior to reduction 94.…”

Section: Formation Of Intermetallic Compoundsmentioning

confidence: 98%

Formation of Intermetallic Compounds by Reactive Metal–Support Interaction: A Frequently Encountered Phenomenon in Catalysis

2014

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This Review discusses the structural and catalytic aspects of the recently introduced reactive metal-support interaction. This special term was coined to account for the inability of the original concept of the strong metal-support interaction to accurately describe the structural, compositional, and electronic changes frequently occurring in oxide-supported metal particle catalysts at very high temperatures upon reduction in hydrogen, in many cases leading to intermetallic compound or substitutional alloy formation. This inaccuracy predominantly refers to the requirement of full reversibility upon oxidation and mild reduction for a strong metal-support interaction. A close look at the formation of oxide-supported intermetallic compounds upon high-temperature reduction reveals that these compounds are very common in catalysis and the situation is much more complex compared to unsupported intermetallic compounds due to the presence of the intermetallic compound-oxide interface

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Section: Formation Of Intermetallic Compoundsmentioning

confidence: 98%

Formation of Intermetallic Compounds by Reactive Metal–Support Interaction: A Frequently Encountered Phenomenon in Catalysis

2014

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“…These ''model'' surfaces [2][3][4][5][6] typically consist of a planar oxide support decorated with metal nanoparticles, making these surfaces amenable to surface characterization and microscopy techniques. Such model surfaces can be prepared by various techniques, such as solution-based methods [7,8] or vapor deposition techniques [2][3][4][5][6][9][10][11][12][13]. Model catalyst surfaces prepared by vapor deposition methods under UHV conditions, allow for creation of planar oxide films decorated by metal nanoparticles in an ultra clean environment [2][3][4][5][6].…”

Section: Introductionmentioning

confidence: 99%

Characterization of Pt/SiO2 Model Catalysts at UHV and Near Atmospheric Pressures

et al. 2009

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Pt/SiO 2 model catalyst samples, prepared under UHV conditions in a contiguous high pressure reactor cell surface analysis chamber, have been characterized via CO oxidation reaction kinetics under elevated pressure conditions (approaching 1 atm). Reaction kinetics are studied as a function of Pt coverage (h Pt = 1-10 mL), along with measurements on a Pt(110) single crystal for direct comparison. CO desorption measurements and STM measurements on Pt/SiO 2 films at T = 300 K have been obtained at various h Pt . Kinetic results show agreement between observations on single crystal and catalyst samples, and general agreement and correlation is obtained for site calculations across the various methods. Results demonstrate the utility of well characterized model catalyst samples in obtaining qualitative and quantitative reactivity data at elevated pressures.

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“…In particular, recent studies in our laboratory of the structure and morphology of oxide-supported epitaxially grown Pt particles, subjected to various reduction procedures between 673 and 1073 K, have shown that the kinetic barrier for alloy formation is strongly influenced by the way of catalyst preparation. Defined threshold temperatures for alloying were observed after a 1 bar hydrogen treatment of regular Pt particles supported by ceria (about 723 K [18,27,45]), silica (773 K [19,20]) and alumina (823 K [19,28]). In each case, the cubic Pt 3 Me alloy is formed in a first step, probably in a topotactic transition at the interface between the octahedral particle and the respective oxide.…”

Section: Structural and Chemical Changes Of Oxide-supported Metal Parmentioning

confidence: 99%

“…The metal crystals are flattened and neighboring particles tend to coalesce. Parallel studies of different catalyst films of equal particle size and distribution have shown that under otherwise comparable conditions (hydrogen pressure, particle size and interparticle distance) coalescence of rhodium particles starts to occur near 573 K on vanadia [26], between 573 and 623 K on titania [17], above 623 K on ceria [27] and above 673 K on alumina [17,28].…”

Section: Structural and Chemical Changes Of Oxide-supported Metal Parmentioning

confidence: 99%

Hydrogen-induced metal-oxide interaction studied on noble metal model catalysts

Unterberger

Jenewein²,

Klötzer³

et al. 2006

React Kinet Catal Lett

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The effect of hydrogen reduction on the structure and catalytic properties of "thin film" and "inverse" model systems for supported metal catalysts is discussed. Thin film model catalysts were obtained by epitaxial growth of Pt and Rh nanoparticles on NaCl (001), which were coated with amorphous or crystalline supports of alumina, silica, titania, ceria and vanadia. Structural and morphological changes upon hydrogen reduction between 473 and 973 K were examined by high resolution electron microscopy. Metal-oxide interaction sets in at a specific reduction temperature and is characterized by an initial "wetting" stage, followed by alloy formation at increasing temperature, in the order VO x < TiO x < SiO 2 < CeO x < Al2O 3 . "Inverse" model systems were prepared by deposition of oxides on a metal substrate, e.g. VO x /Rh and VO x /Pd. Reduction of inverse systems at elevated temperature induces subsurface alloy formation. In contrast to common bimetallic surfaces, the stable subsurface alloys of V/Rh and V/Pd have a purely noble metal-terminated surface, with V positioned in near-surface layers. The uniform composition of the metallic surface layer excludes catalytic ensemble effects in favor of ligand effects. Activity and selectivity, e.g. for CO and CO 2 methanation and for partial oxidation of ethene, are mainly controlled by the temperature of annealing or reduction. Reduction above 573 K turned out to be beneficial for the catalytic activity of the subsurface alloys, but not for the corresponding thin film systems which tend to deactivate via particle encapsulation.

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Regular Alumina-Supported Nanoparticles of Iridium, Rhodium and Platinum Under Hydrogen Reduction: Structure, Morphology and Activity in the Neopentane Conversion

Cited by 37 publications

References 30 publications

Formation of Intermetallic Compounds by Reactive Metal–Support Interaction: A Frequently Encountered Phenomenon in Catalysis

Formation of Intermetallic Compounds by Reactive Metal–Support Interaction: A Frequently Encountered Phenomenon in Catalysis

Characterization of Pt/SiO2 Model Catalysts at UHV and Near Atmospheric Pressures

Hydrogen-induced metal-oxide interaction studied on noble metal model catalysts

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