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  • 1
    Electronic Resource
    Electronic Resource
    Application of Ru exchanged zeolite-Y in ammonia synthesis (1992)
    Springer
    Catalysis letters 14 (1992), S. 339-348 
    Details
    ISSN: 1572-879X
    Keywords: Ammonia synthesis ; Ru-zeolite ; metal clusters ; conversion measurements
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Na-Y zeolite was cation exchanged with Ru(NH3)6Cl3 yielding at 25% exchange level a light-purple solid which was active in ammonia synthesis at atmospheric pressure. Pulse conversion experiments show that the catalyst stores nitrogen as it was observed with the conventional iron catalyst. At 810 K the conversion reached about 20% of the maximum conversion of the iron catalyst. The catalyst deactivated reversibly within 30 h due to agglomeration. The active species in the catalyst is most likely a cluster-like Ru metal particle prevented from sintering under the reducing conditions of catalysis by the zeolite framework.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00769672
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  • 2
    Electronic Resource
    Electronic Resource
    The reduction of NO with H2 over Ru/MgO (1998)
    Springer
    Catalysis letters 53 (1998), S. 77-81 
    Details
    ISSN: 1572-879X
    Keywords: SCR of NO ; Ru ; MgO ; frontal chromatography ; TPD ; TPSR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Ruthenium supported on magnesia was found to be a highly active and selective catalyst for the reduction of NO to N2 with H2. The adsorption of NO on Ru/MgO was studied at room temperature by applying frontal chromatography with a mixture of 2610 ppm NO in He. Subsequently, temperature‐programmed desorption (TPD) and temperature‐programmed surface reaction (TPSR) experiments in H2 were performed. The adsorption of NO was observed to occur partly dissociatively as indicated by the formation of molecular nitrogen. The TPD spectrum exhibited a minor NO peak at 340 K indicating additional molecular adsorption of NO during the exposure to NO at room temperature, and two N2 peaks at 480 K and 625 K, respectively. The latter data are in good agreement with previous results with Ru(0001) single‐crystal samples, where the interaction with NH3 was found to lead to two N2 thermal desorption states with a maximum coverage of atomic nitrogen of about 0.38. Heating up the catalyst after saturation with NO at room temperature in a H2 atmosphere revealed the self‐accelerated formation of NH3 after partial desorption of N2, whereby sites for reaction with H2 become available. As a consequence, the observed high selectivity towards N2 under steady‐state reduction conditions is ascribed to the presence of a saturated N+O coadsorbate layer resulting in an enhanced rate of N2 desorption from this layer and a very low steady‐state coverage of atomic hydrogen. The formation of H2O by reduction of adsorbed atomic oxygen is the slow step of the overall reaction which determines the minimum temperature required for full conversion of NO.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1019072915187
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  • 3
    Electronic Resource
    Electronic Resource
    Microstructure of the activated industrial ammonia synthesis catalyst (1991)
    Springer
    Catalysis letters 11 (1991), S. 19-31 
    Details
    ISSN: 1572-879X
    Keywords: Ammonia synthesis ; iron catalyst ; surface characterization ; promoter effects ; nitrides ; ion scattering spectroscopy ; XPS ; HRTEM
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00866897
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  • 4
    Electronic Resource
    Electronic Resource
    The temperature-programmed desorption of N2 from a Ru/MgO catalyst used for ammonia synthesis (1996)
    Springer
    Catalysis letters 36 (1996), S. 229-235 
    Details
    ISSN: 1572-879X
    Keywords: N2 TPD ; N2 adsorption ; Ru ; MgO ; NH3 synthesis ; microkinetic analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The temperature-programmed desorption (TPD) of N2 from a Ru/MgO catalyst used for ammonia synthesis was studied in a microreactor flow system operating at atmospheric pressure. Saturation with chemisorbed atomic nitrogen (N-*) was achieved by exposure to N2 at 573 K for 14 h and subsequent cooling in N2 to room temperature. With a heating rate of 5 K/min in He, a narrow and fairly symmetric N2 TPD peak at about 640 K results. From experiments with varying heating rates a preexponential factor Ades = 1.5×1010 molecules/(site s) and an activation energy Edes = 158 kJ/mol was derived assuming secondorder desorption. This rate constant of desorption is in good agreement with results obtained with a Ru(0001) single crystal surface in ultra-high vacuum (UHV). The rate of dissociative chemisorption was determined by varying the N2 exposure conditions. Determination of the coverage of N-* was based on the integration of the subsequently recorded N2 TPD traces yielding Aads = 2×10−6 (Pa s)−1 and Eads = 27 kJ/mol. The corresponding sticking coefficient of about 10−14 at 300 K is in agreement with the inertness of Ru(0001) in UHV towards dissociative chemisorption of N2. However, if the whole catalytic surface were in this state, then the resulting rate of N2 dissociation would be several orders of magnitude lower than the observed rate of NH3 formation. Hence only a small fraction of the total Rumetal surface area of Ru/MgO seems to be highly active dominating the rate of ammonia formation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00807624
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  • 5
    Electronic Resource
    Electronic Resource
    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
    Keywords: Ammonia synthesis ; supported ruthenium catalyst ; dispersed ruthenium ; instationary kinetics ; lifetime effects ; ruthenium oxidation ; surface analysis ; XPS
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00815416
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  • 6
    Electronic Resource
    Electronic Resource
    Model identification of a spatiotemporally varying catalytic reaction (1993)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 39 (1993), S. 89-98 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: 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.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690390110
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  • 7
    Electronic Resource
    Electronic Resource
    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
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: 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.
    Notes: 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.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19764200208
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  • 8
    Electronic Resource
    Electronic Resource
    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
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: 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%.
    Notes: 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%.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19754150302
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  • 9
    Electronic Resource
    Electronic Resource
    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
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: 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.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cite.330410513
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  • 10
    Electronic Resource
    Electronic Resource
    Dechema-Monographien Bd. 78: Moderne Verfahren der Oberflächenanalyse. Herausgeg. v. D. Behrens u. K. Fischbeck. Verlag Chemie GmbH, Weinheim/Bergstr. 1975. 1. Aufl., 306 S., zahlr. Abb. u. Tab., Ln. DM 57,75 f. Mitglieder d. DECHEMA u. d. Mitgliedsvereine d. Europ. Föderation f. Chemie-Ingenieur-Wesen, DM 72,20 f. Nichtmitglieder (1975)
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 47 (1975), S. 533-533 
    Details
    ISSN: 0009-286X
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cite.330471207
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