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  • 1
    ISSN: 1588-2837
    Keywords: Aniline hydrogenation ; alkali promoted nickel ; Ni/La2O3 ; selectivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract In the vapor phase, the selectivity of the title reaction could be increased to about 90% by promoting traditional type nickel catalysts with NaOH. The use of strongly basic lanthana as support resulted in 95–99% selectivity.
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  • 2
    ISSN: 1588-2837
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Abstract Окисление пропилена воздухом на серебряных катализаторах с микропористой структурой было исследовано как в проточном, так и в рециркуляционном открытом реакторе. При строго изотермических условиях, предотвращая местный перегрев катализатора, окись пропилена была получена с высокой селективностью, равной приблизительно 50%-ам.
    Notes: Abstract The oxidation of propylene with air on silver catalysts of macropore structure has been studied both in a flow and an open recirculation reactor. Under strictly isothermal conditions, avoiding the local overheating of the catalyst, propylene oxide was produced with a selectivity as high as about 50%.
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  • 3
    ISSN: 1588-2837
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Abstract Адсорбция CCl4 на V2O4 и кинетика стационарной реакции изучены с помощью волюметрического и термогравиметрического методов. Ниже 420 К адсорбция носит физический характер, однако предполагается, что незначительная часть CCl4 претерпевает диссоциацию. Кажущаяся энергия активации хлорирования 77±5 кДж. моль−1, а порядок реакции составляет 0,5 по CCl4.
    Notes: Abstract The adsorption of CCl4 on V2O5 as well as the steady state kinetics of the chlorination reaction in this system have been studied by volumetric and thermogravimetric methods. Though the adsorption observable below 420 K is of physical character, it can be suggested that an unmeasurable, dissociative type adsorption also occurs. The apparent activation energy of the chlorination process is 77±5 kJ mol−1, while the reaction order is 0.5 in CCl4.
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  • 4
    ISSN: 1588-2837
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Abstract Первоначальная стадия реакции CCl4 с V2O5 была изучена с помощью массспектрометрии и рентгеновской фотоэлектронной спектроскопии. По предложенному механизму диссоциативно-хемосорбированный CCl4 превращается в CO2 через COCl2, поверхностные атомы ванадия постепенно принимают два хлора перед образованием летучего конечного продукта реакции VOCl3.
    Notes: Abstract Initial stage of the reaction of CCl4 with V2O5 has been studied by MS and XPS techniques. According to the proposed mechanism dissociatively chemisorbed CCl4 transforms to CO2 via adsorbed COCl2, while surface vanadium atoms involved are gaining step by step two chlorine atoms before the formation of the volatile end-product VOCl3.
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  • 5
    ISSN: 1588-2837
    Keywords: COS formation ; oxide catalysts ; electronic structure ; activity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Under steady state conditions also La2O3 and ThO2, both having strong ionic character, unfilled d- and f-orbitals and a large metal ion radius proved to be order(s) of magnitude more active than oxides of s, sp and d-metals.
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  • 6
    ISSN: 1588-2837
    Keywords: Oxide catalysts ; acid-base properties ; COS formation ; initial activity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Among various acidic, basic and amphoteric oxides La2O3 and ThO2, both having strong ionic character and peculiar acid-base properties, exhibited outstanding initial catalytic activity in the CO2+CS2=2COS reaction.
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  • 7
    ISSN: 1573-8469
    Keywords: Virus assays ; virus strains ; strain distinctions ; Pisum sativum ; host reactions ; virus-induced plant necrosis ; symptom diversity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Description / Table of Contents: Samenvatting Tussen 1966 en 1970 zijn in verschillende landen virussen gerapporteerd, die bij erwt met zaad overgaan, maar in verschillende opzichten leken te verschillen. Isolaten uit Japan en de USA bleken serologisch nauw aan elkaar verwant, zo niet identiek te zijn. Daarom werd de internationale naam ‘pea seed-borne mosaic virus’ voorgesteld. In Nederland was het virus beschreven onder de naam erwterolmozaïekvirus. Zeven isolaten van het virus uit de USA, Japan, Tsjechoslowakije en Nederland zijn nader met elkaar vergeleken in reactie op geselecteerde differentiërende rassen van erwt (Pisum sativum) en op enkele andere plantessorten, en in serologische eigenschappen zowel als in deeltjeslengte. Serologisch waren de isolaten niet van elkaar te onderscheiden, wel echter van het verwante bonescherpmozaïekvirus. De voor alle vormen van het laatste virus onvatbare ‘Perfection’-type erwterassen bleken al eerder alle vatbaar te zijn voor het erwterolmozaïekvirus. Ook verschillen de isolaten niet in deeltjeslengte (750 nm). Bij toetsing in zes verschillende over de wereld verspreide laboratoria bleek de reactie van de differentiërende erwterassen te variëren van een snelle, de hele plant dodende necrose (groep I) tot onvatbaarheid (groep V). Ook tussen de virusisolaten bestonden kleine verschillen in reactie. Het Nederlandse isolaat E224 gedroeg zich opvallend mild. Ook in de, directe vergelijkingsproeven op enkele toetsplantesoorten bleken kleine biologische verschillen te bestaan. De geconstateerde verschillen overschrijden echter niet die tussen stammen van eenzelfde virus. Wellicht gaat het bij het optreden van necrose en van zwakke symptomen om genen die het vatbaarheidsgensbm modificeren.
    Notes: Abstract Seven isolates of pea seed-borne mosaic virus (PSbMV) were compared on selectedPisum sativum L. differentials and by microprecipitin and SDS-gel serology and particle length. All isolates were characterized by 750 nm particle-length modes and were closely related serologically, but some were readily distinguished onP. sativum differentials. Isolate distinctions were of the magnitude typical for virus strains. Differentials, diversePisum germplasm from U.S. Plant Introduction accessions, provided a practical means of PSbMV strain differentiation.
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  • 8
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 9 (1986), S. 237-241 
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Silica-alumina catalysts have been applied for a long time in cracking and reforming reactions. Lewis type surface sites are generally accepted to serve as active centers. In this respect, surface properties of these materials are of main concern. In the present work SiO2 doped γ-Al2O3 with less than a monolayer coverage were prepared by the reaction of SiCl4 (g) with γ-Al2O3 at 820-1120 K. Catalytic activity of the samples was tested by a model reaction of n-hexane cracking. Surface composition and electronic state were evaluated by XPS investigations performed on a KRATOS XSAM 800 instrument. Catalytic activity (conversion) varies remarkably with increasing Si content showing a sharp maximum at low Si coverage. The observed shift of Al 2p lines with increasing Si content is interpreted as an enhancement of the acceptor or acidic character of the surface Al atoms. The Auger parameter for Si(α'Si), (composed by addition of Si 2p BE and Si (KLL) KE values) passes also through a maximum at the same Si-content, as does the conversion curve. A close correlation of the Auger parameter and the catalytic activity is established for samples with (Si/Al)≲7%. This leads to a conclusion, that the rise in extra-atomic relaxation energy may serve as an additional indication of enhanced catalytic activity.
    Additional Material: 6 Ill.
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  • 9
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The mechanical properties of Si3N4 based ceramic bodies are largely controlled by the phases formed on the grain boundaries during sintering. For this reason determination of the state and the chemical composition of the surface of the starting Si3N4 powder is of prime theoretial and practical importance, especially in the cases when advanced ultrafine powders are used. In this work an ultrafine Si3N4 powder, obtained by high temperature plasma nitridation of silicon, has been characterized by XPS. Oxygen, carbon and also a small amount of potassium were detected as surface impurities. The Si 2p and Si (KLL) spectral lines could be decomposed into two components corresponding to silicon in Si3N4 and SiO2 phases. From angle-resolved and Ar-ion depth-profiling experiments a layer model, consisting of a Si3N4 core covered by a relatively thick SiO2 layer and a carbon contaminant overlayer, could be elucidated.
    Additional Material: 6 Ill.
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  • 10
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: For model calculations it is assumed that metal spheroids are randomly distributed on spherical support particles of nearly closest-packed arrangement. Both the metal and the support can be covered with layers or submonolayers of promoter(s) and carbon. The average diameters as well as n, the average number of metal particles on one support sphere, are estimated from total surface area and selective chemisorption measurements and preferably by electron microscopy too. In the computer programme two cases are distinguished depending on whether n 〈 4 or n 〉 4, since in the latter case the partial shadowing of coated metal particles by others should also be considered. Electron beams emitted by the metal, the support and their layers are calculated as a function of the ‘angle of latitude’ of the support spheres and the ‘angle of latitude and longitude’ of the metal spheroids. The computation variables are the thickness and sequence of different layers above the metal and the support, the extent of ‘immersion’ of metal particles into the support and/or its layers and the extent of diffusion of promotor cations into the support matrix. The calculated intensities are compared with the measured ones. By this method the probable fine structure of an alkali-promoted Pd/SiO2 (n 〈 4) and a sodium-promoted Ni/(Al2O3 + SiO2) catalyst (n 〉 4) has been determined.
    Additional Material: 6 Ill.
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