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  • 1
    Digitale Medien
    Digitale Medien
    The effect of water on the formation of strongly bound oxygen on silver surfaces (1995)
    Springer
    Catalysis letters 32 (1995), S. 171-183 
    Details
    ISSN: 1572-879X
    Schlagwort(e): oxygen ; partial oxidation ; reconstruction ; reflection electron microscopy ; Raman spectroscopy ; silver ; water
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Interaction of water with an oxygenated Ag(111) surface leads to an enhancement of the surface restructuring and an activated formation of hydroxyl groups (OH) located stably on the surface and incorporated in the subsurface region, as evidenced by means of reflection electron microscopy (REM) and in situ Raman spectroscopy. Dehydroxylation of OHads at elevated temperatures releases the strongly bound oxygen species labelled Oγ at the surface, and offers an alternative to the energetically less favorable pathway for the direct formation of the Oγ species from molecular oxygen.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00806112
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  • 2
    Digitale Medien
    Digitale Medien
    Microstructure of the activated industrial ammonia synthesis catalyst (1991)
    Springer
    Catalysis letters 11 (1991), S. 19-31 
    Details
    ISSN: 1572-879X
    Schlagwort(e): Ammonia synthesis ; iron catalyst ; surface characterization ; promoter effects ; nitrides ; ion scattering spectroscopy ; XPS ; HRTEM
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Industrial doubly-promoted iron catalysts and model systems of singly-promoted K- and Al-iron catalysts were characterised by their catalytic performance at 1 bar pressure. The relevance of bulk nitrogen for catalytic performance is shown. The catalysts were also activated in an in-situ reaction chamber of a He-ion scattering spectrometer (ISS) and their top atomic layer elemental composition was determined after they had reached similar performance as in the microreactor tests. The bulk microstructure of these samples was investigated by high resolution transmission electron microscopy (TEM) and microdiffraction. All evidence indicates that small highly crystalline α-Fe platelets act as active phase. Their surfaces are covered to a large extent by promotor compounds which are partly present as poorly crystalline aggregates with iron oxide leaving only a small fraction of elemental iron directly exposed to the gas phase. The intimate contact between iron crystals and promoters particles prevents recrystallisation and is the key to the understanding of the structural stability of the catalyst system.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00866897
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  • 3
    Digitale Medien
    Digitale Medien
    Surface and subsurface products of the interaction of O2 with Ag under catalytic conditions (1991)
    Springer
    Catalysis letters 11 (1991), S. 253-265 
    Details
    ISSN: 1572-879X
    Schlagwort(e): Silver ; oxygen ; selective oxidation ; thermal desorption ; subsurface compounds
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Polycrystalline Ag treated with O2 at pressures up to 1 bar and at temperatures up to 920 K was examined by TDS. It was found that the peak commonly observed at 595±25 K and assigned to adsorbed atomic oxygen (Oa) is shifted to higher desorption temperatures with rising dosing temperatures. Since saturation of the uptake was not possible either, this peak was identified as dissolved atomic oxygen (Od). The existence of a maximum for the O2 uptake after exposure at 820 K was found. Hence, under conditions of formaldehyde synthesis (≈ 920 K) the ability of the catalyst to dissolve oxygen is near its maximum.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00764316
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  • 4
    Digitale Medien
    Digitale Medien
    On the nature of the active state of silver during catalytic oxidation of methanol (1993)
    Springer
    Catalysis letters 22 (1993), S. 215-225 
    Details
    ISSN: 1572-879X
    Schlagwort(e): Ion-scattering spectroscopy (ISS) ; methanol oxidation ; oxygen ; Raman spectroscopy ; reflection electron microscopy (REM) ; silver ; X-ray photoelectron spectroscopy (XPS)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Under the applied high reaction temperatures (∼900 K) the Ag surface is restructured and a tightly held oxygen species is formed on the surface (Oγ) apart from O atoms dissolved in the bulk (Oβ). Methanol oxidation to formaldehyde proceeds through this Oγ species as demonstrated by application of a variety of spectroscopic techniques.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00810368
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  • 5
    Digitale Medien
    Digitale Medien
    Ruthenium supported on zeolite A: preparation and characterisation of a stable catalyst for ammonia synthesis (1994)
    Springer
    Catalysis letters 25 (1994), S. 61-74 
    Details
    ISSN: 1572-879X
    Schlagwort(e): Ammonia synthesis ; supported ruthenium catalyst ; dispersed ruthenium ; instationary kinetics ; lifetime effects ; ruthenium oxidation ; surface analysis ; XPS
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Reaction of Ru(NH3)6Cl3 with Na-A and K-A zeolites yielded oligomeric amino-oxo-complexes supported on the zeolite. Controlled thermal activation under hydrogen converted the precursor in a two-step reaction into an active catalyst with good long-term stability and resistance against small doses of oxygen poison. Several nanometers sized Ru metal particles are chemically bonded to the zeolite surface which provides in the K form an alkali promoter at the metal-zeolite interface. Extensive oxidation breaks the metal-support anchoring and re-reduction produces Ru metal particles sintering rapidly into large metal crystals with only small residual catalytic activity.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00815416
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  • 6
    Digitale Medien
    Digitale Medien
    Identification of RuO2 as the active phase in CO oxidation on oxygen-rich ruthenium surfaces (2000)
    Springer
    Topics in catalysis 14 (2000), S. 95-100 
    Details
    ISSN: 1572-9028
    Schlagwort(e): ruthenium ; ruthenium dioxide ; oxide ; CO oxidation ; oxygen ; chemisorption
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract CO oxidation over ruthenium dioxide (RuO2) dominates the CO/CO2 conversion rate over the catalytically active oxygen-rich Ru(0001) surfaces. In sharp contrast, chemisorbed O overlayers on Ru(0001) (with and without dissolved oxygen) are virtually inactive with respect to CO oxidation.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009063201555
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  • 7
    Digitale Medien
    Digitale Medien
    Model identification of a spatiotemporally varying catalytic reaction (1993)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 39 (1993), S. 89-98 
    Details
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: The occurrence of instabilities in chemically reacting systems, resulting in unsteady and spatially inhomogeneous reaction rates, is a widespread phenomenon. In this article, we use nonlinear signal processing techniques to extract a simple, but accurate, dynamic model from experimental data of a system with spatiotemporal variations. The approach consists of a combination of two steps. The proper orthogonal decomposition [POD or Karhunen-Loève (KL) expansion] allows us to determine active degrees of freedom (important spatial structures) of the system. Projection onto these “modes” reduces the data to a small number of time series. Processing these time series through an artificial neural network (ANN) results in a low-dimensional, nonlinear dynamic model with almost quantitative predictive capabilities.This approach is demonstrated using spatiotemporal data from CO oxidation on a Pt (110) crystal surface. In this special case, the dynamics of the two-dimensional reaction profile can be successfully described by four modes; the ANN-based model not only correctly predicts the spatiotemporal short-term behavior, but also accurately captures the long-term dynamics (the attractor). While this approach does not substitute for fundamental modeling, it provides a systematic framework for processing experimental data from a wide variety of spatiotemporally varying reaction engineering processes.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/aic.690390110
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  • 8
    Digitale Medien
    Digitale Medien
    Die Kristall- und MolekülStruktur von S4N4·2C7H8Anmerkung b. d. Korr.: Die Struktur ist inzwischen auch von anderer Seite veröffentlicht (Griffin u. Sheldrick, Acta Crystallogr. B31, 895 (1975)). Die Publikation unserer Ergebnisse scheint trotzdem sinnvoll, da sie wesentlich genauer sind. (1132 gegenüber 338 Reflexen, R-Wert 3,9 gegenüber 8,8% und damit kleinere δ-Werte, H-Atome aus Differenzfouriersynthese und nicht nur geometrisch lokalisiert.) (1976)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 420 (1976), S. 155-158 
    Details
    ISSN: 0044-2313
    Schlagwort(e): Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Beschreibung / Inhaltsverzeichnis: Crystal and Molecular Structure, of S4N4 · 2C7H8The structure of the title compound has been determined from threedimensional X-ray data. Crystals are monoclinic, with unit cell dimenions a = 16.532 Å, b = 8.563 Å, c = 10.880 Å, β = 103.2°, space group C2h6—C2/c and Z = 4. Least squares refinement, by use of 1132 independent reflections measured on a diffractometer has reached 3.9%.In the S4N4·2C7H8 molecules the organic components are linked to two sulfur atoms of the S4N4, ring each.
    Notizen: Die Struktur von S4N4 · 2C7H8 wurde röntgenographisch bestimmt. Die Verbindung kristallisiert monoklin, in der Raumgruppe C2h6—C2/c, mit a = 16,532 Å, b = 8,563 Å, c = 10,880 Å, β = 103,2° und Z = 4. Die Verfeinerung nach der Methode der kleinsten Quadrate ergab einen R-Wert von 3,9%.Die beiden Bicyclopentadien-Molekeln sind an je 2 Schwefelatome des S4N4-Ringes gebunden.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/zaac.19764200208
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  • 9
    Digitale Medien
    Digitale Medien
    Darstellung von Chloro-aqua-Komplexen des Indium(III) und Röntgenstrukturanalyse von [InCl4(H2O)2][S4N3] - einem Tetrachloro-cis-diaqua-Komplex des Indium(III) (1975)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 415 (1975), S. 193-201 
    Details
    ISSN: 0044-2313
    Schlagwort(e): Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Beschreibung / Inhaltsverzeichnis: Synthesis and X-Ray Structure Determination of [InCl4(H2O)2][S4N3] - a Tetrachloro-cis-diaqua Complex of Indium(III)The compounds [InCl4(H2O)2][S4N3] (I) and In2Cl8H2O(S4N3)2 (II) were synthesized and the structure of the former determined by x-ray methods. The compound crystallizes in the space group D2h16-Pnam, the unit cell dimensions are a = 19.473 ± 0.003 Å, b = 6.183 ± 0.003 Å, c = 10.814 ± 0.003 Å. Least squares refinement has reached R = 4.9%.
    Notizen: Die Verbindungen [InCl4(H2O)2][S4N3] (I) und In2Cl8H2O(S4N3)2 (II) wurden dargestellt und die Struktur der ersteren mittels Röntgenstrukturanalyse bestimmt. Die Verbindung kristallisiert in der Raumgruppe D2h16 - Pnam mit den Gitterkonstanten a = 19,473 ű 0,003 Å, b = 6,183 ± 0,003 Å, c = 10,814 ± 0,003 Å. Die Verfeinerung nach der Methode der kleinsten Quadrate ergab einen R-Wert von 4,9%.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/zaac.19754150302
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  • 10
    Digitale Medien
    Digitale Medien
    Elementarprozesse bei Reaktionen an reinen OberflächenVortrag auf dem Jahrestreffen der Verfahrens-Ingenieure, 1. bis 3. Oktober 1968 in Stuttgart. (1969)
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 41 (1969), S. 289-294 
    Details
    ISSN: 0009-286X
    Schlagwort(e): Chemistry ; Industrial Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Primärvorgänge bei der heterogenen Katalyse können mit atomar reinen Einkristall-Oberflächen untersucht werden. Aussagen über die Struktur von Oberflächenphasen werden mit der Methode der Beugung niederenergetischer Elektronen (LEED) erhalten, mit deren Hilfe eine allgemeine Charakterisierung von Adsorptionserscheinungen und katalytischen Reaktionen möglich ist. Es wird über ausgewählte Beispiele berichtet.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cite.330410513
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