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  • 1
    ISSN: 0020-1693
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1572-879X
    Keywords: CuO-ZnO-MeO x catalysts ; characterization by XRD ; DTA ; adsorption ; alcohol synthesis ; C2-C5-OH selectivity ; influence of porosity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Some relations between the preparation of modified CuO-ZnO catalysts, their structural properties and their catalytic performance in the hydrogenation of carbon monoxide have been demonstrated. The different activities in the formation of higher alcohols have been attributed to an influence of the porosity on chain growth. The coupling or insertion of C1 intermediates seems to be favoured by an increasing surface coverage with C1 intermediates due to a transport limitation of methanol production. The pore size distribution of the catalysts has been varied by different calcination, thermal ageing, CuO/ZnO ratios, the method of promoting with Al2O3 and pelleting.
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  • 3
    ISSN: 1572-879X
    Keywords: faujasite-hosted rhodium ; in situ FTIR spectroscopy ; CO hydrogenation ; rhodium dispersion ; methanol selectivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract In situ FTIR spectroscopy has been applied to study the reason of the different selectivity behaviour of rhodium in the CO hydrogenation reaction in dependence on the different particle size. Several forms of molecularly adsorbed CO are observed, such as linearly- and bridgedbonded CO on metallic rhodium as well as dicarbonyl species with Rh(I) centres formed by oxidation of Rh(0) with protons in presence of CO. Furthermore, non-reactive formate, acetate, and carbonate species are produced as side products of the reaction. The higher selectivity to oxygenates, particularly to methanol, is explained by the existence of multiple-bonded CO present only on small rhodium crystallites. The multiple-bonded CO formed at low temperatures is converted at higher temperatures to the highly reactive formyl species, which is hydrogenated to methanol.
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  • 4
    ISSN: 1572-879X
    Keywords: Faujasite X hosted rhodium ; rhodium particle size ; IR-spectroscopy ; TEM ; CO hydrogenation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Different metal dispersions of Na-faujasite X hosted rhodium were generated and characterized by transmission electron microscopy (TEM) and IR-spectroscopy. CO hydrogenation has been studied over these Rh/NaX-zeolite catalysts. The finer rhodium dispersion with a mean particle size of 1–2 nm shows a higher selectivity towards oxygenates (methanol, ethanol and dimethyl ether) as compared to the coarser dispersion (4–5 nm), where nearly exclusively methane and higher hydrocarbons are formed.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1572-879X
    Keywords: Solid-state ; ion exchange ; dealuminated Y zeolite ; rhodium catalysts ; infrared ; spectroscopy ; Rh dicarbonyl ; acid hydroxyls
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The solid-state ion exchange of Rh chloride with highly dealuminated Y zeolite has been studied by in situ FTIR spectroscopy. Thermal treatment in vacuum and calcination in oxygen up to 600°C results in an exchange limited to ca. 25% at temperatures higher than 400°C. The ion exchange can be performed much more effectively (over 50%) and at lower temperatures (100–150°C) in the presence of CO in the gas phase. A linear correlation has been found between the formation of well-defined Rh(CO) 2 + species and the simultaneous loss of acid hydroxyl groups for samples treated at different conditions. From these results a model is proposed with the formation of Rh subcarbonyls, the migration of these species to the cation positions of the zeolite and, finally, the formation of the stable well-defined Rh(CO) 2 + species at these positions as essential steps of the ion exchange in the presence of CO.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Reaction kinetics and catalysis letters 22 (1983), S. 221-225 
    ISSN: 1588-2837
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Abstract С помощью метода ИК спектроскопии следили за образованием изоцианата из CO и NH3 на катализаторах Rh/Al2O3 и Rh/NaY. Изоцианат образуется также за счет реакции CO с координационно связанным аммиаком в виде [Rh(NH3)5Cl]2+/NaY.
    Notes: Abstract The formation of isocyanate from CO and NH3 on Rh/Al2O3 and Rh/NaY catalysts under various conditions was obtained using IR-transmission spectroscopy. Isocyanate is also formed by the reaction of CO with NH3 coordinatively bound as [Rh(NH3)5Cl]2+NaY.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Reaction kinetics and catalysis letters 26 (1984), S. 387-390 
    ISSN: 1588-2837
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Abstract CO реагирует с Rh(III), нанесенном на MgO и ZnO при повышенных температурах (〉373 К), образуя геминальные дикарбонильные частицы Rh(CO)2 на поверхности. После восстановления водородом при 743 и 473 К, соответственно, доминирующими адсорбированными формами являются линейные и мостиковосвязанные CO на больших кристаллитах Rh. Это находится в пр=qoтивоположности с Rh на других носителях, таких как Al2O3, SiO2 и т.д.
    Notes: Abstract CO reacts with Rh(III) supported on MgO and ZnO at elevated temperatures (〉373 K) to form the gem-dicarbonyl species Rh(CO)2 on the surface. After reduction with hydrogen at 743 and 473 K, respectively, the dominant adsorption forms are the linear and bridge bonded CO on larger Rh-crystallites. This is in contrast to Rh on other supports such as Al2O3, SiO2, etc.
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  • 8
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 367 (1969), S. 34-39 
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: The catalytical activity of mixed oxides of Cr2O3 and MgO and Beo, respectively, on the CO oxidation depends on the solid state formation of the spinel phase MIICr2O4 as catalytically active component. The well-crystallised spinel phase is more active than the disordered one.
    Notes: An Mischoxiden von Cr2O3 und MgO bzw. Cr2O3 und BeO wurde eine Abhängigkeit der katalytischen Aktivität von der Zusammensetzung gefunden, die zeigt, daß der durch Festkörperreaktion gebildete Spinell MIICr2O4 die katalytisch aktive Komponente ist. Außerdem werden die katalytischen Eigenschaften von der Ausbildung der Kristallstruktur beeinflußt; die gut kristallisierte Spinellphase ist katalytisch aktiver als die gestörte ungeordnete Phase.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 325 (1963), S. 175-180 
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Specific rate constants of the alkaline solvolysis of p-substituted dimethyl-phenyl silanes in ethanol/water are determined and compared with former results of correspondingly substituted triphenyl silanes. The inductive and mesomeric effect of the aryl group on the reaction velocity are estimated.
    Notes: Es werden die spezifischen Geschwindigkeitskonstanten der alkalischen Solvolyse von p-substituierten Dimethyl-phenyl-silanen in Äthanol/Wasser gemessen und mit früheren Ergebnissen an entsprechend substituierten Triphenyl-silanen verglichen. Induktiver und mesomerer Effekt der Aryl-Gruppe auf die Reaktionsgeschwindigkeit werden abgeschätzt.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 346 (1966), S. 51-65 
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: MgO/Cr2O3 mixed-oxide catalysts contain, depending on the preparation conditions and molar composition, in addition to a more or less ordered spinel phase the free starting oxides, small amounts of MgCrO4 (being important as an intermediate of the spinel formation), and Cr3+ on Mg2+ positions of different site symmetry.In the less complicated BeO/Cr2O3 system, besides BeCr2O4 and the starting oxides only small amounts of BeCrO4 occur which, however, is supposed to activate catalytically the spinel formation like MgCrO4.
    Notes: Es wird gezeigt, daß im System MgO/Cr2O3 unter den gewählten Darstellungsbedingungen je nach Zusammensetzung neben einer mehr oder weniger geordneten Spinellphase die freien Ausgangsoxide, sehr kleine Mengen an MgCrO4, das eine sehr entscheidende Rolle als Zwischenprodukt bei der Spinellbildung spielt, sowie auf Mg2+-Gitterplätzen befindliches Cr3+ mit verschiedener Punktsymmetrie existieren.Einfacher liegen die Verhältnisse im System BeO/Cr2O3. Neben BeCr2O4 und den Ausgangsoxiden BeO und Cr2O3 enthalten diese Substanzen nur geringe Mengen an BeCrO4, das bei der Spinellbildung sicherlich die gleiche katalytische Rolle wie das MgCrO4 bei der MgCr2O4-Bildung spielt, nämlich die Aktivierungsenergie der Spinellbildung herabzusetzen.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
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