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  • 1
    Publication Date: 2016-05-26
    Description: One of the main goals in catalysis is the characterization of solid/gas interfaces in a reaction environment. The electronic structure and chemical composition of surfaces become heavily influenced by the surrounding environment. However, the lack of surface sensitive techniques that are able to monitor these modifications under high pressure conditions hinders the understanding of such processes. This limitation is known throughout the community as the “pressure gap.” We have developed a novel experimental setup that provides chemical information on a molecular level under atmospheric pressure and in presence of reactive gases and at elevated temperatures. This approach is based on separating the vacuum environment from the high-pressure environment by a silicon nitride grid—that contains an array of micrometer-sized holes—coated with a bilayer of graphene. Using this configuration, we have investigated the local electronic structure of catalysts by means of photoelectron spectroscopy and in presence of gases at 1 atm. The reaction products were monitored online by mass spectrometry and gas chromatography. The successful operation of this setup was demonstrated with three different examples: the oxidation/reduction reaction of iridium (noble metal) and copper (transition metal) nanoparticles and with the hydrogenation of propyne on Pd black catalyst (powder).
    Print ISSN: 0034-6748
    Electronic ISSN: 1089-7623
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
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  • 2
    Publication Date: 2012-07-25
    Description: Al13Fe4 as a low-cost alternative for palladium in heterogeneous hydrogenation Nature Materials 11, 690 (2012). doi:10.1038/nmat3347 Authors: M. Armbrüster, K. Kovnir, M. Friedrich, D. Teschner, G. Wowsnick, M. Hahne, P. Gille, L. Szentmiklósi, M. Feuerbacher, M. Heggen, F. Girgsdies, D. Rosenthal, R. Schlögl & Yu. Grin Replacing noble metals in heterogeneous catalysts by low-cost substitutes has driven scientific and industrial research for more than 100 years. Cheap and ubiquitous iron is especially desirable, because it does not bear potential health risks like, for example, nickel. To purify the ethylene feed for the production of polyethylene, the semi-hydrogenation of acetylene is applied (80 × 106 tons per annum; refs , , ). The presence of small and separated transition-metal atom ensembles (so-called site-isolation), and the suppression of hydride formation are beneficial for the catalytic performance. Iron catalysts necessitate at least 50 bar and 100 °C for the hydrogenation of unsaturated C–C bonds, showing only limited selectivity towards semi-hydrogenation. Recent innovation in catalytic semi-hydrogenation is based on computational screening of substitutional alloys to identify promising metal combinations using scaling functions and the experimental realization of the site-isolation concept employing structurally well-ordered and in situ stable intermetallic compounds of Ga with Pd (refs , , , , ). The stability enables a knowledge-based development by assigning the observed catalytic properties to the crystal and electronic structures of the intermetallic compounds. Following this approach, we identified the low-cost and environmentally benign intermetallic compound Al13Fe4 as an active and selective semi-hydrogenation catalyst. This knowledge-based development might prove applicable to a wide range of heterogeneously catalysed reactions.
    Print ISSN: 1476-1122
    Electronic ISSN: 1476-4660
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Natural Sciences in General , Physics
    Published by Springer Nature
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  • 3
    Publication Date: 2008-04-05
    Description: Alkynes can be selectively hydrogenated into alkenes on solid palladium catalysts. This process requires a strong modification of the near-surface region of palladium, in which carbon (from fragmented feed molecules) occupies interstitial lattice sites. In situ x-ray photoelectron spectroscopic measurements under reaction conditions indicated that much less carbon was dissolved in palladium during unselective, total hydrogenation. Additional studies of hydrogen content using in situ prompt gamma activation analysis, which allowed us to follow the hydrogen content of palladium during catalysis, indicated that unselective hydrogenation proceeds on hydrogen-saturated beta-hydride, whereas selective hydrogenation was only possible after decoupling bulk properties from the surface events. Thus, the population of subsurface sites of palladium, by either hydrogen or carbon, governs the hydrogenation events on the surface.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Teschner, Detre -- Borsodi, Janos -- Wootsch, Attila -- Revay, Zsolt -- Havecker, Michael -- Knop-Gericke, Axel -- Jackson, S David -- Schlogl, Robert -- New York, N.Y. -- Science. 2008 Apr 4;320(5872):86-9. doi: 10.1126/science.1155200.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin, Germany. teschner@fhi-berlin.mpg.de〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/18388290" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 4
    Publication Date: 2010-04-10
    Description: Production of the industrial chemical propylene oxide is energy-intensive and environmentally unfriendly. Catalysts based on bulk silver surfaces with direct propylene epoxidation by molecular oxygen have not resolved these problems because of substantial formation of carbon dioxide. We found that unpromoted, size-selected Ag3 clusters and approximately 3.5-nanometer Ag nanoparticles on alumina supports can catalyze this reaction with only a negligible amount of carbon dioxide formation and with high activity at low temperatures. Density functional calculations show that, relative to extended silver surfaces, oxidized silver trimers are more active and selective for epoxidation because of the open-shell nature of their electronic structure. The results suggest that new architectures based on ultrasmall silver particles may provide highly efficient catalysts for propylene epoxidation.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Lei, Y -- Mehmood, F -- Lee, S -- Greeley, J -- Lee, B -- Seifert, S -- Winans, R E -- Elam, J W -- Meyer, R J -- Redfern, P C -- Teschner, D -- Schlogl, R -- Pellin, M J -- Curtiss, L A -- Vajda, S -- New York, N.Y. -- Science. 2010 Apr 9;328(5975):224-8. doi: 10.1126/science.1185200.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Chemical Sciences and Engineering Division, Argonne National Laboratory, Argonne, IL 60439, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/20378815" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 5
    Publication Date: 2017-07-14
    Description: Author(s): V. V. Kaichev, A. A. Saraev, A. Yu. Gladky, I. P. Prosvirin, R. Blume, D. Teschner, M. Hävecker, A. Knop-Gericke, R. Schlögl, and V. I. Bukhtiyarov A novel type of temporal and spatial self-organization in a heterogeneous catalytic reaction is described for the first time. Using in situ x-ray photoelectron spectroscopy, gas chromatography, and mass spectrometry, we show that, under certain conditions, self-sustained reaction-rate oscillations a... [Phys. Rev. Lett. 119, 026001] Published Thu Jul 13, 2017
    Keywords: Condensed Matter: Structure, etc.
    Print ISSN: 0031-9007
    Electronic ISSN: 1079-7114
    Topics: Physics
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  • 6
    ISSN: 1572-879X
    Keywords: rhodium black ; platinum black ; surface carbon ; surface oxygen ; methylcyclopentane
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The surface composition of Rh and Pt blacks (as determined by XPS) shows carbon and oxygen impurities in the untreated state. Oxygen on Pt is present as adsorbed O as well as OH/H2O groups and oxidized carbon. Rh was partly oxidized to Rh2O3, in agreement with UPS showing hardly any Fermi‐edge intensity in untreated Rh as opposed to untreated Pt. High Fermi‐edge intensities indicated a predominant metallic surface after an in situ treatment with H2 at 483 K, increasing the purity (XPS) to ∼90%. This treatment reduced Rh to metal and removed its C impurity. Pt, in turn, retained much carbon after H2 treatment, present mainly as graphitic carbon. A minor amount of CO was also detected, some of the O 1s peak belonging to it. The two metals were tested in methylcyclopentane reactions. Considering the necessity of carbon for nondegradative reactions and oxygen enhancing fragmentation, a correlation is suggested between the typical impurities of Pt and Rh and their respective catalytic propensities: the high fragmentation activity of Rh and the predominant nondegradative reactions to C6 “ring opening products” on Pt.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Journal of pest science 35 (1962), S. 48-48 
    ISSN: 1612-4766
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Journal of pest science 37 (1964), S. 40-43 
    ISSN: 1612-4766
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Description / Table of Contents: Summary Nests of city pigeons have been sprayed with DDT and gathered for zoological investigation. Several of the insects and mites, which are living in these nests, are potential transmitters of infectious diseases, others are destructive in stored supply. Dominance has been found forDermanyssus gallinae (bird mite) andFannia canicularis (lesser house-fly). The importance of these and of some other species out of pigeon's nests is discussed. The results lead to consequences, which support the steps of boards of health to control city pigeons and their nests.
    Abstract: Résumé Des nids des pigeons domestiques sauvages furent arrosés avec DDT. Alors les nids ont été recueillis pour des explorations zoologiques. Quelques mites et insectes qui habitent ces nids sont potentiel capable de transmettre des maladies infectieuses, autres sont nuisible pour les provisions mises en magasin. Les especesDermanyssus gallinae (mite d'oiseau) etFannia canicularis (petite mouche domestique) se présentent dominants. L'importance de ces deux espèces et aussi de quelques autres de ces nids est discuté. Les résultats légitiment les dispositions des conseils de santé pour controller les pigeons domestiques et leurs nids.
    Notes: Zusammenfassung Nester verwilderter Haustauben wurden mit DDT übersprüht und zu zoologischer Untersuchung eingesammelt. Einige der Insekten und Milben, die in diesen Nestern leben, sind potentielle Überträger von Infektionskrankheiten, andere sind Vorratsschädlinge. Als dominant auftretende Arten werden herausgestellt die VogelmilbeDermanyssus gallinae und die kleine StubenfliegeFannia canicularis. Die Bedeutung dieser und einiger anderer Arten aus Taubennestern wird erörtert. Die Ergebnisse führen zur Folgerung, Maßnahmen der Gesundheitsämter zur Kontrolle der verwilderten Haustauben und ihrer Nester zu stützen.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Reaction kinetics and catalysis letters 68 (1999), S. 25-33 
    ISSN: 1588-2837
    Keywords: Rh/Al2O3 ; Rh/SiO2 ; methylcyclopentane ring opening ; and fragmentation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Hydrogenolytic ring opening of methylcyclopentane (MCP) was investigated on Rh/Al2O3 and Rh/SiO2 catalysts, prepared by the incipient wetness method. Strong dependence can be seen in the yield and distribution of ring opening products as a function of temperature and hydrogen pressure. They depended also on the support used. The ring opening reaction required high hydrogen coverage, and was not random (hindered in the vicinity of the methyl group), thus, mainly 2-methylpentane (2MP) and 3-methylpentane (3MP) were formed. The fragments consisted of C1–C5 alkanes, with methane andi-pentane as main fragments. This means the possibility of breaking two C−C bonds during one sojourn of the reactant on the catalyst, both taking place far from the substituent. The loose positive correlation between the ratios ofi-pentane/n-pentane and 3MP/n-hexane seems to support this conclusion.
    Type of Medium: Electronic Resource
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  • 10
    Publication Date: 2016-05-01
    Print ISSN: 0034-6748
    Electronic ISSN: 1089-7623
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
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